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849 articles found

T0026 – Thermally stimulated measurements on polycrystalline Pbl2 layers

Thermally stimulated current measurements have been performed on polycrystalline layers of lead iodide grown from solution. Several TSC peaks or bands have been observed at temperatures of 100 K, 195-220 K, 230-240 K and 270-300 K. Comparison with PbI 2 single crystal shows that the polycrystalline structure of the material introduces additional defects. In contrast the defect currently found in single crystal and attributed to the lead vacancy has not been clearly evidenced in the polycrystalline layers. The position and relative intensity of the peaks can be modified by Ag doping and thermal annealing. On the other hand, only small differences resulting from the anisotropy of the material have been observed depending on the orientation of the electric field with regards to the grains orientation.
J.P. Ponpon and M. Amann, Eur. Phys. J. Applied Physics 18 (2002) 25-31

T0025 – Thermally stimulated current in SiO2

Thermally stimulated current (TSC) techniques provide information about oxide-trap charge densities and energy distributions in MOS (metal-oxide-semiconductor) capacitors exposed to ionizing radiation or high-field stress that is difficult or impossible to obtain via standard capacitance-voltage or current-voltage techniques. The precision and reproducibility of measurements through repeated irradiation/TSC cycles on a single capacitor is demonstrated with a radiation-hardened oxide, and small sample-to-sample variations are observed. A small increase in Edelta' center density may occur in some non-radiation-hardened oxides during repeated irradiation/TSC measurement cycles. The importance of choosing an appropriate bias to obtain accurate measurements of trapped charge densities and energy distributions is emphasized. A 10 nm deposited oxide with no subsequent annealing above 400°C shows a different trapped-hole energy distribution than thermally grown oxides, but a similar distribution to thermal oxides is found for deposited oxides annealed at higher temperatures. Charge neutralization during switched-bias irradiation is found to occur both because of hole-electron annihilation and increased electron trapping in the near-interfacial SiO2. Limitations in applying TSC to oxides thinner than 5 nm are discussed.
D.M. Fleetwood, R.A. Reber Jr, L.C. Riewe and P.S. Winokur, Microelectronics Reliability 39 (1999) 1323-1336

T0010 – Thermally stimulated current method applied to highly irradiated silicon diodes

We propose an improved method for the analysis of Thermally Stimulated Currents (TSC) measured on highly irradiated silicon diodes. The proposed TSC formula for the evaluation of a set of TSC spectra obtained with different reverse biases leads not only to the concentration of electron and hole traps visible in the spectra but also gives an estimation for the concentration of defects which not give rise to a peak in the 30-220K TSC temperature range (very shallow or very deep levels). The method is applied to a diode irradiated with a neutron fluence of ?n = 1.82 x 10^13 n/cm2.
I. Pintilie, C. Tivarus, L. Pintilie, M. Moll, E. Fretwurst, G. Lindstroem, Nuclear Instruments and Methods in Physics Research A 476 (2002) 652-657

L0192 – Influence of microstructure and architecture on oxygen permeation of La(1?X)SrXFe(1?Y)(Ga, Ni)YO3?? perovskite catalytic membrane reactor

Catalytic membrane reactors (CMR) have been an economically attractive process for natural gas reforming to syngas (H2 + CO) since more than twenty years. The CMR studied in this paper consists of a mixed ionic and electronic conductor dense layer (La(1?X)SrXFe(1?Y)GaYO3??). High temperature X-ray diffraction analysis, from room temperature to 900 °C under air and nitrogen atmosphere, show a reversible monoclinic to rhombohedral phase transition around 300 °C, and good chemical and dimensional stabilities of La0.8Sr0.2Fe0.7Ga0.3O3?? material. The La0.8Sr0.2Fe0.7Ga0.3O3?? dense layer elaborated by tape casting has been respectively coated with La0.8Sr0.2Fe0.7Ga0.3O3?? on the air side and La0.8Sr0.2Fe0.7Ni0.3O3?? on the inert side using screen printing. The influences of the dense membrane microstructure and of the surface exchange kinetics on the oxygen semi-permeation performances are evaluated. Small grain size, mainly below 1 ?m in the dense membrane significantly increases the oxygen flux. A porous layer of La0.8Sr0.2Fe0.7Ni0.3O3?? or La0.8Sr0.2Fe0.7Ga0.3O3?? on the air or inert side of the membrane increased strongly the specific oxygen semi-permeation. The impact of the porous layer is much more important than the reduction of the grain size. In this case, surface exchange kinetics are the limiting steps of oxygen permeation, and Ni-containing formulation leads to the highest flux.
E. Juste, A. Julian, P.-M. Geffroy, A. Viveta, V. Coudert, N. Richet, C. Pirovano, T. Chartier, P. Del Gallo, Journal of the European Ceramic Society 30 (2010) 1409–1417

L0191 – Ba1-xPrxCo1-yFeyO3-µ as cathode materials for low temperature solid oxide fuel cells

Ba1?xPrxCo1?yFeyO3?µ (BPCF) perovskite oxides have been synthesized and investigated as cathode materials for low temperature solid oxide fuel cells (LT-SOFCs). Compared with those of Ba0.5Sr0.5Co0.8Fe0.2O3?µ (BSCF) and Sm0.5Sr0.5CoO3 (SSCo) cathode materials, BPCF has a lower polarization resistance at decreased temperatures. In particular, Ba0.5Pr0.5Co0.8Fe0.2O3?µ showed the lowest polarization loss among the different compositions as a cathode material for LT-SOFCs. The area specific resistance (ASR) of Ba0.5Pr0.5Co0.8Fe0.2O3?µ as a cathode material is 0.70 and 0.185 cm2 at 500 ?C and 550 ?C, respectively. The maximum power density of the cell BPCF/SDC/Ni–SDC with humidified hydrogen as fuel and air as oxidant reaches 860mWcm?2 at 650 ?C.
Rob Hui, Chunwen Sun, Sing Yick, Cyrille Decès-Petit, Xinge Zhang, Radenka Maric, Dave Ghosh, Electrochimica Acta 55 (2010) 4772–4775

L0189 – Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate

Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by X-ray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using (31)P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistance of beta tricalcium phosphate-33.16 wt% fluorapatite composites reached its maximum value (13.7 MPa) at 1400 ( composite function)C, whereas the optimum densification was obtained at 1350 ( composite function)C (93.2%). Above 1400 ( composite function)C, the densification and mechanical properties were hindered by the tricalcium phosphate allotropic transformation and the formation of both intragranular porosity and cracks. The (31)P magic angle spinning nuclear magnetic resonance analysis of composites as sintered at various temperatures or with different percentages of fluorapatite reveals the presence of tetrahedral P sites
Nadhem Bouslama, Foued Ben Ayed , Jamel Bouaziz, Journal of the Mechanical Behavior of Biomedical Materials 3 (2010) 2-13

L0188 – Mechanical properties of tricalcium phosphate–alumina composites

This study deals to produce tricalcium phosphate - fluorapatite composites sintering at various temperatures (, and ) and with different alumina additives amounts (2.5 wt%, 5 wt%, 7.5 wt%, 10 wt% and 20 wt%). The characterization of samples before and after sintering was investigated, using X-ray diffraction, infrared spectroscopy, scanning electronic microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. Mechanical properties have been measured by Brazilian test. The evolution of composite rupture strength was studied as a function of sintering temperature. The effect of sintering on the mechanical properties was measured with the change in composition and microstructure of the composite. The mechanical resistances of composites were increased with the temperatures and with concentrations of alumina. At , the mechanical resistance reaches its maximum value with 5 wt% Al2O3 (13.6 MPa) whereas the optimum density is about 90% with 2.5 wt% Al2O3.
S. Sakka, F. Ben Ayed, J. Bouaziz, IOP Conf.Series:MaterialsScienceandEngineering 28 (2012) 012028

L0187 – The densification, microstructure, and electrical properties of aluminum-doped zinc oxide sputtering target for transparent conductive oxide film

AZO films are regarded as a potential substitute for ITO due to their excellent performance. To optimize the performances of AZO films, the correlation between the target and film must be clearly clarified. Therefore, how the properties, particularly the electrical ones, of the sputtering targets evolve with the sintering parameters are rarely highlighted. To develop high-quality AZO and ZnO targets, the densification, microstructure, and electrical properties of the targets were investigated in this study. The results showed that after sintering at 1100 °C in air, the 2 wt% Al2O3 additive in ZnO results in retarded densification, the formation of ZnAl2O4 phase, and inferior electrical properties. However, after sintering at 1200 °C or higher temperatures, the Al2O3 additive leads to finer grain size, higher sintered density, and better electrical properties. In general, the AZO targets are also found to exhibit higher Hall mobility and lower carrier density than the AZO films do.
Ming-Wei Wu, Day-Shan Liu, Yu-Hsiang Su, Journal of the European Ceramic Society 32 (2012) 3265–3275

L0186 – Structural modifications induced by free protons in proton conducting perovskite zirconate membrane

Recently hydrogen appears as an alternative energy vector for a sustainable modern world. Proton conducting perovskite ceramics showing significant proton conduction (~ 10? 2 S/cm at 600 °C) at medium temperature exhibit high potential as electrolytic membranes of water steam electrolysers. Prior to industrial requirements (mechanical and chemical stability, long working life) the structural behaviour of the host perovskite structure disturbed by the Ln/RE substitution and the presence of protonic species have to be well determined as a function of severe operating conditions. Ex situ neutron diffraction and thermal expansion as well as in situ high water pressure Raman studies were performed on non-protonated, protonated and deprotonated high dense SrZr0.9Yb0.1O2.95 ceramics. The results show that the proton doping (SrZr0.9Yb0.1O2.95H0.003) induces long range order structural modifications, weak enough to guaranty the stability during the high water pressure–high temperature cycling.
Aneta Slodczyk, Philippe Colomban, Gilles André, Oumaya Zaafrani, Frédéric Grasset, Olivier Lacroix, Béatrice Sala, Solid State Ionics 225 (2012) 214–218

L0184 – Upgrading the performance of La2Mo2O9-based solid oxide fuel cell under single chamber conditions

Various anode-supported solid oxide fuel cells (SOFC), based on 10 mol% Dy-doped La 2 Mo 2 O 9 (LDM) electrolyte, are prepared analytically and operated under single chamber conditions to explore the connections between electrode and power performance. The cathode of tested SOFCs is compositionally graded with three composites of samarium strontium cobaltite and Gd-doped ceria (GDC) to relax the thermal stress, because of sizable thermal expansion differences above 400 °C. We focus the research attention on varying the anode pore structure and composition to promote the power performance in methane/air mixture at 700 °C. For the one-layer support of GDC+NiO+LDM anode, addition of 10 wt% graphite minimizes its mass transport resistance through creating 8–5 ?m long and ?1 ?m wide slit-shaped pores. The graphite pore former raises the peak power value by 80 mW cm ?2 . Adopting a more porous and active outer layer, the double-layer support further enhances the cell power. The peak power was first raised by 48 mW cm ?2 , using an outer layer that was prepared with 63 wt% NiO. Dosing 3% Pd on this outer layer uplifts another 59 mW cm ?2 . In this study, with an improved anode, the peak power value reaches 437 mW cm ?2 .
Chi-Chieh Yao, Dah-Shyang Tsai, Jen-Chieh Lo, Wen-Hung Chung, David P. Wilkinson, International Journal of Hydrogen Energy 37 (2012) 9792-9800

L0183 – The effect of MgO and SiO2 codoping on the properties of Nd:YAG transparent ceramic

Nd:YAG transparent ceramics were fabricated by a reactive sintering method under vacuum using SiO2, MgO and compound additives (SiO2 and MgO) as sintering aids. The effects of SiO2 and MgO on the microstructure and sintering process of Nd:YAG ceramics were studied. High quality Nd:YAG ceramics with compound sintering aids obtained by vacuum sintering at 1780 °C are composed of grains of the size ˜10 ?m, and their transmittance is 82% at 400 nm. It was found the absorption coefficient of 1.0 mol% Nd:YAG ceramic was 8.6 cm-1 at 808 nm and its absorption cross section was calculated to be 6.26 × 10-20 cm2.
Hao Yang, Xianpeng Qin, Jian Zhang, Jan Mab, Dingyuan Tang, Shiwei Wang, Qitu Zhang, Optical Materials 34 (2012) 940–943

L0182 – Solution combustion synthesis and sintering behavior of CaAl2O4

The influence of the quantity of urea on the synthesis of calcium aluminate by solution combustion method was studied. It was shown that the amount of urea has a big influence on morphological characteristic and phase composition of the combustion products.The sintering behavior of the combustion products, before and after milling, was studied by rate controlled sintering method, based on which a thermal schedule was designed improving the sintering of CaAl2O4 .
M.A. Rodr?guez, C.L. Aguilar, M.A. Aghayan, Ceramics International 38 (2012) 395–399

L0181 – Chemical expansion of La0.8Sr0.2Fe0.7Ga0.3O3–?

This paper deals with the chemical expansion measurements and modelling of La0.8Sr0.2Fe0.7Ga0.3O3–?. The expansion behavior has been evaluated using a dilatometer and X-ray diffraction over a wide range of temperatures (RT to 1373 K) and oxygen partial pressures (10? 21 to 1 atm). The material stoichiometry evolution with temperature and oxygen partial pressure has been measured using thermogravimetry analysis at different oxygen partial pressure, from 10? 21 to 0.5 atm and from RT to 1473 K. Considering a typical defect model for lanthanum ferrite oxides, chemical expansion depends linearly on the Fe4+ concentration rather than on the oxygen vacancy concentration. A model of chemical expansion as a function of pO2 and temperature is then proposed. It helps to understand and anticipate the chemical expansion behavior exhibited by this material when used as Ionic Transport Membrane (ITM).
Olivier Valentin, Francis Millot, Éric Blond, Nicolas Richet, Aurelie Julian, Emmanuel Véron, Sandra Ory, Solid State Ionics 193 (2011) 23–31

L0180 – Microstructural development of interface layers between co-sintered alumina and spinel compacts

Tests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500 °C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40 ?m length and 5 ?m width was observed after 16 h at 1500 °C. Growth rate of the columnar spinel grains from parent spinel towards alumina follows parabolic kinetics, controlled by a mixed process of O2? ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth.
Emre Yalamac, Claude Carry, Sedat Akkurt, Journal of the European Ceramic Society 31 (2011) 1649–1659

L0175 – Sintering Behavior ofMagnesium-Substituted Fluorapatite Powders Prepared by HydrothermalMethod

Magnesium-substituted fluorapatite powders were synthesized by hydrothermal method, and their sintering behavior was investigated by dilatometry in the temperature range 25–1100°C. Analysis of the obtained powders by X-ray diffraction and 31P NMR spectroscopy showed that the powders consisted of a single apatite phase and no amorphous phase has been formed. Compared to pure fluorapatite, the shrinkage of the substituted samples occurred in two steps and the temperature at which the sintering rate was maximum is lower. In addition, the shrinkage was interrupted by an expansion of the samples due to the formation of a liquid phase. The latter phase led to the crystallization of needle-crystals by a dissolution-diffusion-reprecipitation process.
S. Nasr, K. Bouzouita, Bioinorganic Chemistry and Applications, Volume 2011, Article ID 453759

L0174 – Formation and calcination temperature-dependent sintering activity of YAG precursor synthesized via reverse titration method

The composition homogeneity of YAG precursors synthesized via both normal and reverse titration co-precipitation methods is discussed. It was demonstrated that that the reverse titration process possesses better co-precipitation characteristics than the normal titration process, based on a real-time monitoring of the reaction pH and measurement of the Y/Al ratio in the precipitate. The formation process of the precipitate obtained by reverse titration method was discussed. The effect of calcination temperature on sintering properties of the YAG powder was investigated by analysis of the crystalline phase, the specific surface area, and the morphology of the powder. The shrinkage rate test of compacts made from different powders indicates that a higher calcination temperature results in a lower densification speed and shrinkage ratios. Microstructure observation shows that the ceramics made from YAG nanopowder, which was obtained at a higher calcination temperature, have a more uniform grain-size distribution and fewer residual pores
Yuanhua Sang, Hong Liu, Xudong Sun, Xiaolin Zhang, Haiming Qin, Yaohui Lv, Di Huo, Duo Liu, Jiyang Wang, Robert I. Boughton, Journal of Alloys and Compounds 509 (2011) 2407–2413

L0173 – Sintering and conductivity of BaCe0.9Y0.1O2.95 synthesized by the sol–gel method

Ceramic powders of BaCe0.9Y0.1O2.95 (BCY10) have been prepared by the sol–gel method. Barium and yttrium acetate and cerium nitrate were used as ceramic precursors in a water solution. The reaction process studied by DTA–TG and XRD showed that calcination of the precursor powder at T ? 1000 °C produces a single perovskite phase. The densification behaviour of green compacts studied by constant heating rate dilatometry revealed that the shrinkage rate was maximal at 1430 °C. Sintered densities higher than 95% of the theoretical one were thus obtained below 1500 °C. The bulk and additional blocking effects were characterized by impedance spectroscopy in wet atmosphere between 150 and 600 °C. A proton conduction behaviour was clearly identified. The blocking effect can be related to a space-charge depletion layer of protons in the vicinity of grain boundaries.
Agnès Princivalle, Guilhem Martin, Céline Viazzi, Christian Guizard, Nicolas Grunbaum, Laurent Dessemond, Journal of Power Sources 196 (2011) 9238– 9245

L0170 – Magnetic and dielectric properties of Ba12Fe28Ti15O84 layered ferrite ceramics

In this study we report for the first time the magnetic and dielectric properties of the quaternary layered ferrite Ba12Fe28Ti15O84. Dense ferrite ceramics were prepared by conventional sintering using powders obtained by solid-state reaction and by coprecipitation. Only the latter powder resulted in nearly single phase ceramics, whereas larger amounts of secondary phases were observed in the material obtained by the solid-state route. According to the HRTEM investigation, the ferrite lattice is originated by the intergrowth of perovskite-like and spinel-like slabs and can be considered as a natural magnetic superlattice. A ferrimagnetic order with saturation magnetization of ?12.5?A?m2?kg?1 and coercivity of ~1590?A?m?1 (~20?Oe) is proposed at room temperature. The thermomagnetic data indicate a Curie temperature of ~420?K for the quaternary ferrite. An additional magnetic transition was detected at ~700?K and ascribed to a secondary magnetic phase, probably the solid solution of TiO2 in BaFe12O19. An intrinsic relative dielectric constant of the order of 23–50 at room temperature was measured at 109?Hz. At lower frequency the dielectric behaviour is dominated by extrinsic effects related to the heterogeneous electrical nature of the ceramics corresponding to semiconducting grains separated by more insulating grain boundary regions. The dielectric losses are rather high, often >1, indicating an overall semiconducting character of the material.
L P Curecheriu, M T Buscaglia, A C Ianculescu, R C Frunza, I V Ciuchi, A Neagu, G Apachitei, A Bassano, G Canu, P Postolache, L Mitoseriu, V Buscaglia, J. Phys. D: Appl. Phys. 44 (2011) 435002

L0169 – Constitutive modeling of the behaviour of cermet compacts during reaction sintering

This study deals with the identification of a constitutive equation describing the mechanical behaviour of a nickel ferrite based cermet during sintering. This constitutive equation considers the material as a continuum and may enable one to predict the densification behaviour of a powder under different thermal treatments and the impact of compact geometry, external loading on strain and stress generation. A classical viscous equation of the Newtonian type that includes a term describing free sintering densification has been chosen. The method used for the identification of the parameters of this equation is the one proposed Gillia et al., which is based on dilatometry measurement. It includes a stairway thermal cycle for the determination of the free sintering term and intermittent loading for estimating the viscosity. This approach has been successfully applied to nickel ferrite cermet. The model has been found to be adequate to model the densification behaviour up to 1250 °C, but experimental and theoretical efforts must be accomplished to describe the behaviour above this temperature, when the material exhibits swelling.
G. Largiller, L. Dong, D. Bouvard, C.P. Carry, A. Gabriel, Powder Technology 208 (2011) 496–502

L0168 – Long-term degradation of Ta2O5-doped Bi2O3 systems

Bismuth oxide in ?-phase is a well-known high oxygen ion conductor and can be used as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). 5–10 mol% Ta2O5 are doped into Bi2O3 to stabilize ?-phase by solid state reaction process. One Bi2O3 sample (7.5TSB) was stabilized by 7.5 mol% Ta2O5 and exhibited single phase ?-Bi2O3-like (type I) phase. Thermo-mechanical analyzer (TMA), X-ray diffractometry (XRD), AC impedance and high-resolution transmission electron microscopy (HRTEM) were used to characterize the properties. The results showed that holding at 800–850 °C for 1 h was the appropriate sintering conditions to get dense samples. Obvious conductivity degradation phenomenon was obtained by 1000 h long-term treatment at 650 °C due to the formation of ?-Bi2O3 phase and Bi3TaO7, and ?1 1 1? vacancy ordering in Bi3TaO7 structure.
S.E. Lin, W.C.J. Wei, Journal of the European Ceramic Society 31 (2011) 3081–3086

L0166 – Effect of sintering temperature on microstructure and transport properties of Li3xLa2/3?xTiO3 with different lithium contents

Li3xLa2/3?xTiO3 (LLTO) powder with different lithium contents (nominal 3x = 0.03–0.75) was synthesized via a simple sol–gel route and then calcination of gel-derived precursor at 900 °C which was much below the calcination temperature required for synthesizing the LLTO powder via solid state reaction route. The LLTO powder of sub-micron sized particles, derived from such sol–gel method, showed almost no aggregation. Starting from the sol–gel-derived powder, the LLTO ceramics with different lithium contents were prepared at different sintering temperatures of 1250 and 1350 °C. It demonstrated that our sol–gel route is quite simple and convenient compared to the previous sol–gel method and requires lower temperature for the LLTO. Our results also illustrated that lithium content significantly affects the structure and ionic conductivity of the LLTO ceramics. The dependence of the ionic conductivity on the lithium content, lattice structure, microstructure and sintering temperature was investigated systematically.
Hongxia Geng, Jinle Lan, Ao Mei, Yuanhua Lin, C.W. Nan, Electrochimica Acta 56 (2011) 3406–3414

L0165 – Processing, physico-chemical characterisation and in vitro evaluation of silicon containing ?-tricalcium phosphate ceramics

For bone grafting applications, the elaboration of silicon containing beta-tricalcium phosphate (?-TCP) was studied. The synthesis was performed using a wet precipitation method according to the hypothetical theoretical formula Ca3 ? x(PO4)2 ? 2x(SiO4)x. Two silicon loaded materials (0.46 wt.% and 0.95 wt.%) were investigated and compared to a pure ?-TCP. The maturation time of the synthesis required in order to obtain ?-TCP decreased with the amount of silicon. Only restrictive synthesis conditions allow preparing silicon containing ?-TCP with controlled composition. To obtain dense ceramics, the sintering behaviour of the powders was evaluated. The addition of silicon slowed the densification process and decreased the grain size of the dense ceramics. Rietveld refinement may indicate a partial incorporation of silicon in the ?-TCP lattice. X-ray photoelectron spectroscopy and transmission electron microscopy analyses revealed that the remaining silicon formed amorphous clusters of silicon rich phase. The in vitro biological behaviour was investigated with MC3T3-E1 osteoblast-like cells. After the addition of silicon, the ceramics remained cytocompatible, highlighting the high potential of silicon containing ?-TCP as optimised bone graft material.
N. Douard, R. Detsch, R. Chotard-Ghodsnia, C. Damia, U. Deisinger, E. Champion, Materials Science and Engineering C 31 (2011) 531–539

L0163 – Densification and grain growth of 8YSZ containing NiO

The effects of NiO addition on sintering yttria-stabilized zirconia were systematically studied to understand the role of the additive in the sintering process of the solid electrolyte. Specimens of 8 mol% yttria-stabilized zirconia with NiO contents up to 5.0 mol% were prepared using different Ni precursors and sintered at several dwell temperatures and holding times. Densification and microstructural features were studied by apparent density measurements and scanning electron microscopy observations, respectively. The sintering dynamic study was carried out by following the linear shrinkage of powder compacts containing 0–0.75 mol% NiO. Small (up to 1.0 mol%) NiO addition was found to improve the sinterability of yttria-stabilized zirconia. The activation energy for volume diffusion decreases with increasing NiO content, whereas the grain boundary diffusion seems to be independent on this additive. The grain growth of yttria-stabilized zirconia is found to be enhanced even for small NiO contents.
R.M. Batista, E.N.S. Muccillo, Ceramics International 37 (2011) 1047–1053

L0158 – New composites of ZnO–P2O5/Ni having PTC transition and high Seebeck coefficient

In this article, we report the electrical conductivity (?) and Seebeck coefficient (S) of ZnO–P2O5 matrix filled with conductive powder of nickel (Ni). The variation of ? versus volume fraction of Ni showed a non-conducting to conducting phase transition at percolation threshold (28 vol. %). The change of S from high positive to negative values exhibits that this transition is accompanied by the passing of carrier charge from p to n type. On the other hand, the measurements of ? and S as function of temperature, above the percolation threshold, showed a positive temperature coefficient (PTC) phase transition at Tc ? 400 K, linked with a high S = ? 5000 ?V/K, giving highest power factor PF = ?.S 2? 2.10? 4 W m? 1 K? 2. The temperature dependence of the volume expansion enabled to confirm that this transition is associated to the thermal volume variation in matrix. However, the temperature dependence of ? below the percolation threshold showed two different mechanisms: thermally activated hopping behavior at high temperatures and Mott's variable range hopping (VRH) at low temperatures
A. Maaroufi, O. Oabi, B. Lucas, A. El Amrani, S. Degot, Journal of Non-Crystalline Solids 358 (2012) 3312–3317

L0157 – Deformation and cracking during sintering of bimaterial components processed from ceramic and metal powder mixes. Part II: Numerical simulation

In a companion paper (Part I), the processing of two-layer parts by co-sintering of two powder blends has been investigated. As a complement to this experimental study, a finite element simulation of this operation has been achieved. This simulation was based on constitutive equations identified from specific experiments performed with each blend. The numerical results provided deformation and internal stress information that have been found to be fully consistent with the experimental observation. In particular they confirm that cracking occurs in the course of heating, when one material starts densifying and the other one is still brittle, whereas a large densification mismatch at high temperature is not harmful because the low viscosity of both materials leads to the relaxation of internal stresses.
G. Largiller, L. Dong, D. Bouvard, C.P. Carry, A. Gabriel, Mechanics of Materials 53 (2012) 132–141

L0156 – Influence of thermal damage occurrence at microstructural scale on the thermomechanical behaviour of magnesia–spinel refractories

Many refractory materials exhibit high thermal shock resistance, which is often mostly due to their high flexibility. Understanding the microstructure key points allowing to develop a non-linear mechanical behaviour is of great relevance for future material improvements. The present work aims at optimising the processing of magnesia–spinel refractory materials close to industrial ones with simplified microstructures. The final goal is the investigation of the relationship existing between microstructure evolutions and induced thermomechanical properties. The thermal expansion mismatch which exists between the two phases (spinel inclusions and magnesia matrix) is expected to generate, during cooling, radial microcracks around the inclusions. The development of such microcracks network, closely related to the inclusions content, has been studied and the damage occurrence has been confirmed by several high temperature characterisation techniques. The influence of this thermal micro damage on the evolution of stress–strain law in tension of such materials has also been investigated.
R. Grasset-Bourdel, A. Alzina, M. Huger, D. Gruber, H. Harmuth, T. Chotard, Journal of the European Ceramic Society 32 (2012) 989–999

L0154 – Thermal behavior of apatitic calcium phosphates synthesized from calcium carbonate and orthophosphoric acid or potassium dihydrogen orthophosphate

The synthesis of calcium hydroxyapatite powder (Ca-HA) from orthophosphoric acid or from potassium dihydrogen orthophosphate and calcium carbonate was carried out under moderate conditions. A better dissolution of calcium carbonate and a complete precipitation of the orthophosphate species were obtained with orthophosphoric acid, indicating that it may be of interest as a phosphate source compared with potassium dihydrogen orthophosphate. The influence of calcination treatment on the physico-chemical properties of the solids is discussed in this paper. Different characterization techniques such as specific surface area (SBET), true density, particle size distribution, thermo-mechanical analysis, simultaneous thermogravimetry and differential scanning calorimetry analysis, X-ray diffraction and infrared were performed to understand the phase changes during thermal treatment. Specific surface area decreased while true density and particle size increased with the rise in the calcination temperature, due to the sintering of particles and the chemical reactions occurring at high temperatures. Mixtures of well-crystallized Ca-HA and tricalcium phosphate (TCP) or well-crystallized Ca-HA, CaO, and TCP were obtained after calcination at 800–1,000 °C of the solid products starting from orthophosphoric acid or potassium dihydrogen orthophosphate, respectively.
Doan Pham Minh, Marta Galera Mart?nez, Ange Nzihou, Patrick Sharrock, J Therm Anal Calorim, 2012

L0151 – Microstructure and Thermal Behavior of Thermal Barrier Coatings

Yttria stabilized zirconia thick coatings were thermally sprayed from two different feedstock powders. Coating characteristics such as density, crystalline phase composition, and microstructure were evaluated. The thermal expansion coefficient and thermal diffusivity were measured as a function of temperature up to 800 °C and analyzed in terms of the microstructural features. The ability of available models to relate the measured thermal properties to the microstructural features as characterized by readily available methods was assessed. The importance of pore shape and orientation on the thermal conductivity was evidenced. The thermal contact resistance between the substrate and the coating in these samples was estimated from the thermal diffusivity data, and found to change during cooling from 800 °C.
E. Garcia, P. Miranzo, R. Soltani, T. W. Coyle, Journal of Thermal Spray Technology, Volume 17(4) December 2008, 478

L0149 – Synthesis, characterization, and sintering of sol±gel derived cordierite ceramics for high-frequency MLCIs

The synthesis, characterization, and sintering of sol±gel derived cordierite ceramics are investigated in the present paper. Synthesis was carried out by optimizing two main preparation parameters. The effect of the heat-treatment schedule on crystallization and the properties of crystalline phases were analyzed. The additives B2O3 and P2O5 were utilized to promote the crystallization or transformation to ?-cordierite and sintering. This material has a low dielectric constant and a low dissipation factor and can be co-fired with high conductivity metals such as Au, Ag/Pd, Cu paste at low temperature (below 1000°C), suggesting that it would be a promising material for high-frequency MLCIs.
Linghong Luo, Heping Zhou, Chen Xu, Journal of Materials Science: Materials in Electronics 13 (2002) 381-386

L0148 – Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying

In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low YoungÕs modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400 °C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore coarsening and stiffening of the coating. In-situ measurements at 1400 °C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.
Alexandre Guignard, Georg Mauer, Robert Vaßen, Detlev Stöver, Journal of Thermal Spray Technology, Volume 21(3-4), 416, June 2012

L0147 – Sintering and Creep Processes in Plasma-Sprayed Thermal Barrier Coatings

During operation at elevated temperatures, sintering processes can significantly influence the mechanical properties of thermal barrier coatings (TBCs) by increasing Young’s modulus and reducing strain tolerance. These changes of the mechanical response of TBCs were investigated using free-standing plasma-sprayed TBCs in a thermomechanical analysis (TMA) facility. The time-dependent change of Young’s modulus was determined in situ in a flexure mode at different annealing temperatures. In addition, relaxation processes during loading and unloading were monitored. The time-dependent deformation behavior of the TBC sample can be described by a simple viscoelastic approach (Burgers model). Viscosity data are determined as a function of annealing temperature and time.
M. Ahrens, S. Lampenscherf, R. Vaßen, D. Stöver, Journal of Thermal Spray Technology, Volume 13(3), 432, September 2004

L0146 – Synthesis and characterization of a nano-scaled barium cerate perovskite powder using starch as polymerization agent

The preparation of nano-sized BaCeO3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4 m2/g. TEM investigations reveal particles mainly in the size range of 30 to 65 nm. The shrinkage and sintering behavior of resulting powder compacts were studied in comparison to a coarse-grained mixed-oxide BaCeO3 powder (SBET=2.1 m2/g). Dilatometric measurements show that the beginning of shrinkage of compacts from the nano-sized powder is downshifted by 300 °C compared to mixed-oxide powder. Compacts from the nano-sized powder reach a relative density of 91% after sintering at 1450 °C for 10 h.
Roberto Köferstein, Dietrich Hesse, Stefan G. Ebbinghaus, Solid State Ionics 203 (2011) 52–56

L0145 – Drastic decrease of Ba(Zn1/3Ta2/3)O3 sintering temperature by lithium salts and glass phase addition

The complex perovskite oxide Ba(Zn1/3Ta2/3)O3 (BZT) has been studied for its attractive dielectric properties which make this material interesting for applications such as multilayer ceramics capacitors or hyperfrequency resonators. Nevertheless, BZT ceramic requires high temperature to be correctly sintered (@1450°C), that is too high to envisage a silver co-sintering (Tf(Ag) = 961°C). For this reason, the lowering of the sintering temperature of BZT by glass phase’s additions has been investigated. This material is sinterable at low temperature with combined glass phase –lithium salt additions, and exhibits, at 1MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 5 wt% of ZnO-SiO2-B2O3 glass phase and 1 wt% of LiF added BZT sample sintered at 900°C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?r of 32, low dielectrics losses (tan (?)< 10-3) and a temperature coefficient of permittivity ?? of -10ppm/°C. Their good dielectric properties and their compatibility with silver electrodes, make these ceramics suitable for L.T.C.C applications.
A. Chaouchi, S. d’Astorg, S. Marinel, M. Aliouat, Boletín de la Sociedad Española de Cerámica y Vidrio, Vol 50, 2, 79-84, Marzo-Abril 2011

L0142 – Sintering of tricalcium phosphate–fluorapatite composites with zirconia

Zirconia (ZrO2) addition effects on densification and microstructure of tricalcium phosphate–26.52 wt% fluorapatite composites were investigated, using X-ray diffraction, scanning electron microscopy and by analysis using 31P nuclear magnetic resonance. The tricalcium phosphate–26.52 wt% fluorapatite–zirconia composites densification increases versus temperature. At 1300 ?C, the composites apparent porosity reaches 9% with 5 wt% zirconia. XRD analysis of the composites reveals the presence of tricalcium phosphate, fluorapatite and zirconia without any other structures. Above 1300 ?C, the densification was hindered by grain growth and the formation of both intragranular porosity and new compounds. The 31P MAS-NMR analysis of composites sintered at various temperatures or with different percentages of zirconia reveals the presence of tetrahedral P sites. At 1400 ?C, XRD analysis of the tricalcium phosphate–26.52 wt% fluorapatite–20 wt% zirconia composites shows the presence of calcium zirconate and tetracalcium phosphate. This result indicated that partial decomposition of tricalcium phosphate during sintering process of composites when 20 wt% or less ZrO2 was added. Thus, zirconia reacts with tricalcium phosphate forming calcium zirconate and tetracalcium phosphate
Foued Ben Ayed, Jamel Bouaziz, Journal of the European Ceramic Society 28 (2008) 1995–2002

L0141 – Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate

Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by Xray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using 31P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistance of tricalcium phosphate–33.16 wt% fluorapatite composites reached its maximum value (13.7 MPa) at 1400°C, whereas the optimum densification was obtained at 1350°C (93.2%). Above 1400°C, the densification and mechanical properties were hindered by the tricalcium phosphate allotropic transformation and the formation of both intragranular porosity and cracks. The 31P magic angle spinning nuclear magnetic resonance analysis of composites as sintered at various temperatures or with different percentages of fluorapatite reveals the presence of tetrahedral P sites.
Nadhem Bouslama, Foued Ben Ayed, Jamel Bouaziz, Journal of the Mechanical Behavior of Biomedical Materials, 3 (2012) 2-13

L0140 – Sintering and mechanical properties of tricalcium phosphate–fluorapatite composites

Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic ceramics composites. The effect of fluorapatite addition on the densification and the mechanical properties of tricalcium phosphate were measured with the change in composition and microstructure of the bioceramic. The Brazilian test was used to measure the mechanical resistance of the tricalcium phosphate–26.52 wt% fluorapatite composites. The densification and rupture strength increase versus sintering temperature. The composites have a good sinterability and rupture strength in temperature ranging between 1300 and 1400 8C. Thus, the densification ultimate was obtained at 1350 8C and the mechanical resistance optimum reached 9.6 MPa at 1400 8C. Above 1400 8C, the densification and the mechanical properties were hindered by the allotropic transformation of tricalcium phosphate, grain growth and the formation of both intragranular porosity and many cracks. The 31P magic angle spinning nuclear magnetic resonance analysis of composites reveals the presence of tetrahedral P sites.
Nadhem Bouslama, Foued Ben Ayed, Jamel Bouaziz, Ceramics International 35 (2009) 1909–1917

L0135 – Effects of Glass Phase Additions and Stoichiometry on the Ba(Zn1/3X2/3)O3 (X = Ta or Nb) Sinterability and Dielectric Properties

Ba(Zn1/3X2/3)O3 materials where X = Ta or Nb (respectively named BZT and BZN) exhibit attractive properties suitable for applications in type I Multi Layer Ceramics Capacitors (MLCC). Nevertheless, to produce such components using Base Metal Electrodes such as copper, a significant reduction of their sintering temperature is required. The aim of this work is first to study the effects of glass phases additions and secondly the stoichiometry influence on the sintering temperature of BZT and BZN. It is shown for example, that our materials can be sintered in air at a temperature lowered by 450?C when sintering agents (B2O3 with LiF) are combined with a slight non-stoichiometry. The sintered samples are characterised in terms of final density, microstructure and phase content and it was underlined that such modifications (additions and stoichiometry) does not affect the dielectric properties.
François Roulland, Sylvain Marinel, Journal of Electroceramics, 14, 239–246, 2005

L0134 – Synthesis of Hafnia Powders and Nanofiltration Membranes by Sol-Gel Process

Hafnia nanofiltration membranes were prepared by sol-gel process from hafnium 1-methoxy-2 propoxide via colloidal route. This original molecular precursor has been synthesized and characterized by 1H NMR, mass spectroscopy, infrared and elemental analysis. Its peptization revealed to be the most efficient method to provide a highly reactive powder at a low sintering temperature. The porous volume variation and the pore diameter distribution of the hafnia powder have been studied as a function of the sintering temperature and the TGA, DTA and dilatometry study are reported. The membrane sintered at 450?C exhibited a defect-free texture with a cut-off equal to 420 Daltons and pore diameters equal to 1.9 nanometers.
P. Blanc, N. Hovnanian, D. Cot, A. Larbot, Journal of Sol-Gel Science and Technology 17, 99–110 (2000)

L0133 – Anisotropic kinetic of the kaolinite to mullite reaction sequence in multilayer ceramics

Multilayer ceramics with a composite and organized microstructure were realized from kaolin and alumina fibers to improve strength and fracture toughness. Dilatometry experiments along 3 directions reveal anisotropic shrinkages, which are in correlation with different activation energy for sintering. Mullite growth is strongly anisotropic, inducing the formation of an organized microstructure, where larger mullite crystals are mainly oriented in plane of layer and perpendicular to alumina fibers. Kinetic data from thermal transformations show that the starting reaction mechanism is mullite nucleation, and it is continued by a strongly anisotropic grain growth. It is explained by topotactic transformations at phyllosilicate faces and along alumina arrangements. Mullite growth kinetics is also favored perpendicularly to fiber main dimension by the anisotropy of alumina diffusion coefficient. It shows the limited importance of mullite crystallization in microstructural transformation, but it also shows that controlled mullite growth is central in microstructural arrangement.
K. Boussois, N. Tessier-Doyen, P. Blanchart, Journal of the European Ceramic Society 33 (2013) 243–249

L0122 – Sintering studies on Ni–Cu–YSZ SOFC anode cermet processed by mechanical alloying

New 40 vol%[(Cu)–Ni]–YSZ cermet materials processed by mechanical alloying (MA) of the row powders are prepared. The powder compacts are sintered in air, hydrogen and inert (argon) atmospheres at a dilatometer and tubular furnace up to 1,350 °C. Sintering by activated surface concept (SAS) can anticipate and enhance the densification in such powders. Stepwise isothermal dilatometry (SID) sintering kinetics study is performed allowing determining kinetic parameters for Ni–YSZ and Ni–Cu–YSZ pellets. Two-steps sintering processes is indicated while Cu-bearing material features the smallest activation energy for sintering. The allied MA–SAS method is a promising route to prepare SOFC fuel cell anode materials.
Thomaz Augusto Guisard Restivo, Sonia Regina Homem Mello-Castanho, J Therm Anal Calorim (2009) 97, 775–780

L0117 – High temperature properties of SiC and diamond CVD-monofilaments

The chemical, structural and thermomechanical properties of SiC and diamond CVD-monofilaments have been investigated. Electron and Raman microprobe analyses showed graded radial atomic and phase distributions in the SiC filaments. Thermomechanical investigations (tensile/bending elastic modulus/creep tests) were carried out on single filaments and these properties were correlated with the physicochemical features. The thermal behaviour of the CVD-SiC filaments is strongly related to the nature and the amounts of intergranular secondary phases (free carbon or silicon). The strong covalent bonds and the microcrystalline state of the CVD-diamond filaments give rise to an outstanding thermal behaviour.
Georges Chollona, Roger Naslain, Calvin Prentice, Robert Shatwell, Paul May, Journal of the European Ceramic Society 25 (2005) 1929–1942

L0116 – MgTiO3 for Cu base metal multilayer ceramic capacitors

The evolution of the cost of palladium justifies studies devoted to the use of cheap base metals as electrodes for multilayer ceramic capacitors. In a precedent [J. Eur. Ceram. Soc.10-11(2001) 1681] work we investigated on Mn acceptor together with W donor additions on the properties of MgTiO3 ceramics sintered at 1350°C under a reducing atmosphere (wet N2-1%H2). As in acceptor/donor [Proceedings K1; 1206 CIMTEF, Florence (1998) 88] codoped BaTiO3 the insulating character of MgTiO3 was conserved. In order to employ these materials in the production of type-I multilayer ceramic capacitors with Copper inner electrodes we investigate now on the possibility of sintering magnesium titanate at low temperature. We have studied the densification behavior of different MgTiO3 compositions with lithium salts additions, considering particularly the effect of the non-stoechiometry expressed as the Mg/Ti ratio. Full densification appears below 1000°C. The obtained ceramics, that have been co-sintered in a multilayer structure with Cu electrodes, are characterised by a resistivity higher than 10^(13) ohm cm together with a NPO dielectric constant ranging from 14 to 16 depending on the exact composition together with losses lower than 0.2%.
J. Bernard, D. Houivet, J. El Fallah, J.M. Haussonne, Journal of the European Ceramic Society 24 (2004) 1877-1881

L0115 – Lowering of BaB’1/3B”2/3O3 complex perovskite sintering temperature by lithium salt additions

Complex perovskite materials with the formula BaB'1/3B"2/3O3 have been broadly studied for their attractive dielectric properties. These materials exhibit a high relative dielectric constant and a very low dissipation factor. For example, the BaMg1/3Ta2/3O3 material has a relative dielectric constant close to 26 with a dissipation factor lower than 10^(-4) at 1 MHz. These properties are very promising for applications such as hyper-frequency resonators or/and capacitors. Unfortunately, a high temperature is necessary to achieve a satisfying densification of this materials family (>1400°C) whereas the lowering of this temperature is more and more crucial from the industrial point of view. In particular, the development of Base Metal Electrodes Multi-Layer Ceramic Capacitors (BME-MLCC) requires the sintering of dielectric materials at low temperatures (<1100°C). The aim of the study is thus to lower the sintering temperature of these materials. For this goal, lithium salts (Li2CO3, LiF, BaLiF3 and LiNO3) have been tested as sintering agents to densify BaZn1/3Ta2/3O3, BaMg1/3Ta2/3O3 and BaZn1/3Nb2/3O3 materials. It is shown, for example, that the BaMg1/3Ta2/3O3 sintering temperature is lowered by 300°C when 15 mol % of lithium nitrate is added without affecting the dielectric properties at 1 MHz. For the best sintering agents investigated and each studied materials, the ceramic is characterised in terms of final density, microstructure and dielectric properties and densification mechanisms are discussed.
F. Roulland, R. Terras, G. Allainmat, M. Pollet, S. Marinel, Journal of the European Ceramic Society 24 (2004) 1019-1023

L0114 – CaZrO3, a Ni-co-sinterable dielectric material for base metal-multilayer ceramic capacitor applications

The aim of this work is to obtain CaZrO3 powders that are co-sinterable with nickel electrodes. Since CaZrO3 is often sintered at temperatures higher than 1550°C to achieve high sample densities, obtaining a powder co-sinterable with Ni would require lower sinteringtemperatures. The co-sintering also requires that the reaction takes place in a reducing atmosphere. After optimizingthe thermal cycle for the phase synthesis, several approaches were investigated to decrease the CaZrO3 sinteringtemperature. First, the grain size effect on the densification was studied to enhance the calcined powder's reactivity before sintering. In addition, the Ca/Zr ratio was investigated, and the effect of doping with lithium salts was examined. Similarly, in order to allow co-sintering with basemetal inner electrodes, the sinterability and the properties of the dielectric were examined in a reducingatmosphere. Finally, a cosintered material was synthesized, resultingin good dielectric properties. The samples were analyzed in terms of structure and microstructure. The electric and dielectric properties were also measured on sintered samples.
M. Pollet, S. Marinel, G. Desgardin, Journal of the European Ceramic Society 24 (2004) 119-127

L0113 – Thermal and mechanical properties of cordierite, mullite and steatite produced by plasma spraying

Cordierite, mullite and steatite are silicate materials widely used in the ceramics industry. There is, however, only sparse information on their application in plasma spraying and properties of sprayed materials. Plasma sprayed deposits of cordierite, mullite and steatite contain amorphous phases as the result of rapid cooling of molten particles. The amorphous phase has a significant influence on physical properties, especially in connection with heat treatment. This article deals with phase changes of cordierite, mullite and steatite, resulting from plasma deposition. Special attention is paid to amorphous phase crystallization in subsequent heat treatment. Plasma sprayed deposits were produced using a water stabilized plasma torch WSP®. The processes taking place in the deposits were examined primarily by differential thermal analysis (DTA), thermal dilatometry (TMA) and X-ray diffraction (XRD). These measurements were complemented by the determination of physical properties (namely, density, Young's modulus and strength) and morphological observations. Important thermal characteristics like crystallization temperature and the coefficient of thermal expansion (CTE) of all materials were determined.
P. Rohan, K. Neufuss, J. Matejicek, J. Dubskya, L. Prchlik, C. Holzgartner, Ceramics International 30 (2004) 597-603

L0112 – Nanosized alumina from boehmite additions in alumina porcelain 1. Effect on reactivity and mullitisation

The influence of nanosized alumina additions and of grain size of alumina filler on the reaction-sintering of alumina porcelain is investigated. Phase and porosity evolution has been studied from room temperature up to 1400°C. When vitrification occurs the presence of alumina nanoparticles leads to a new type of mullitisation which has two major consequences: a volume expansion resulting in a shrinkage inhibition and a decrease of the amount of liquid which causes densification problems at usual firing temperatures. This phenomenon is enhanced if the alumina filler is coarse but it is limited when fine and round alumina is used because in that last case vitrification kinetics is slowed down.
F. Belnou, D. Goeuriot, P. Goeuriot, F. Valdivieso, Ceramics International 30 (2004) 883-892

L0110 – Iron oxide as an effective sintering aid and a grain boundary scavenger for ceria-based electrolytes

The effect of FeO1.5 addition on the densification behavior and electrical properties of Ce0.8Gd0.2O(2-d) ceramics was examined. The small addition of FeO1.5 (e.g., 0.5 at.%) reduced sintering temperature (by ~200°C) and promoted densification rate. When sintered at 1300°C for 5 h, the 0.5 at.% FeO1.5-doped Ce0.8Gd0.2O(2-d) has ~95% relative density, as compared to ~82% relative density for the undoped one. The measurement of lattice parameter indicated that the FeO1.5 addition also promoted the dissolution of Gd2O3 in CeO2 at lower sintering temperatures. On the other hand, the grain boundary (GB) conductivity could be significantly improved by small addition of FeO1.5. The optimum scavenging effect on SiO2 impurity was achieved by adding 0.5 at.% FeO1.5 to Ce0.8Gd0.2O(2-d) ceramics and sintered at 1400-1500°C.
T.S. Zhang, J. Ma, L.B. Kong, S.H. Chan, P. Hing, J.A. Kilner, Solid State Ionics 167 (2004) 203-207

L0109 – The synthesis mechanism of Ca3Al2O6 from soft mechanochemically activated precursors studied by time-resolved neutron diffraction up to 1000°C

The reaction pathway for the Ca3Al2O6 formation up to 1300°C, from mechanochemically treated mixtures of amorphous aluminum hydroxide and CaCO3; was studied in situ by differential thermal analysis, constant heating rate dilatometry and timeresolved neutron powder diffraction. The experiment was carried out, in an open system, on a sample with the nominal Ca3Al2O6 stoichiometry. The results obtained by neutron diffractometry and thermal analysis were in good agreement with the data obtained by scanning electron microscopy and X-ray diffraction on heat-treated and-quenched samples. The synthesis path implied the formation of cryptocrystalline Al2O3; crystalline CaO, CaAl2O4 and Ca12Al14O33 as transitory phases. Finally the nucleation and growth of the single phase Ca3Al2O6 took place at 1300°C and exhibited porous structure due to CO2 and H2O release.
J.M. Rivas Mercury, A.H. De Aza, X. Turrillas, and P. Pena, Journal of Solid State Chemistry 177 (2004) 866-874

L0108 – Effect of transition metal oxides on densification and electrical properties of Si-containing Ce0.8Gd0.2O(2-d) ceramics

Ce0.8Gd0.2O(2-d) (CGO20) ceramic has been considered as one of the most promising electrolytes for intermediate temperature (IT) fuel cells. It has been reported that some transition metal oxides (TMO), such as MnO2, Fe2O3 and Co3O4, are effective sintering aids for the densification of ceria-based electrolytes. However, very little information is available regarding the effect of TMO addition on the electrical properties of Si-containing CGO20 ceramics. In this study, 0.5 at.% (atomic percent) TMOs have been loaded into the CGO20 with ~30 ppm (pure) and ~200 ppm (impure) SiO2, respectively, and the sintering behavior and ionic conductivity have been investigated. It has been found that Co3O4 is the most effective sintering aid, and the sintering temperature of CGO20 can be reduced by over 200°C by adding 0.5 at.% CoO4/3. All the TMOs used show a slight effect on the grain-boundary (GB) conductivity of the pure CGO20. However, SiO2 additions, together with MnO2 and Co3O4, have found to be extremely detrimental to the GB conduction of CGO20. As compared to the impure CGO20, the GB resistance has been increased by over six times for the impure one with addition of only 0.5 at.% CoO4/3. On the other hand, in contrast to the Mn or Co doping case, small addition of Fe2O3 has a scavenging effect on SiO2 impurity, and significantly improves the GB conduction of the impure CGO20. Therefore, Fe2O3 could be used as an effective sintering aid, as well as a grain-boundary scavenger for SiO2 contaminated ceria-based electrolytes.
T.S. Zhang, J. Ma, Y.J. Leng, S.H. Chan, P. Hing, J.A. Kilner, Solid State Ionics 168 (2004) 187-195

L0107 – The kinetics of surface area reduction during isothermal sintering of hydroxyapatite adsorbent

The behaviour of non-stoichiometric hydroxyapatite (HA) during the calcination in a solid bed was investigated. The structural properties are described in terms of the specific surface area. Calcination led to a significant decrease of the specific surface area by particle coalescence and densification. Hydroxyapatite begins to shrink near 780°C and reaches 97% theoretical density at 1100°C. The specific surface area and density variations are caused both by sintering and chemical reaction. Sintering data from these solids were correlated as a function of time and temperature. The rate of sintering is assumed to obey an Arrhenius equation. These results are compared with a number of literature models describing the mechanism of sintering kinetics using the specific surface area, and a good agreement is observed. The kinetic equation used is based on sintering driven by the curvature gradient in the interparticle neck region associated with initial stage sintering. Then, the decline in specific surface area is accurately described by the empirical equation of the form dS/dt = -B(T)k^b. The changing value of b, also known as the "order" of the reaction, suggests that the diffusion mechanism for loss of surface area may be a function of the temperature.
S. Bailliez, A. Nzihou, Chemical Engineering Journal 98 (2004) 141-152

L0104 – Rare earth phosphate powders RePO4 . nH2O (Re=La, Ce or Y) II. Thermal behavior

The thermal behavior, thermostructural and morphological changes, of rare earth phosphate powders RePO4 . nH2O (Re=La, Ce or Y) was investigated up to 1500°C using high temperature X-ray diffraction, FT-infrared and Raman spectroscopies and thermogravimetry coupled with differential thermal analysis. The hydration water of the compounds was zeolitic (for Re=La or Ce) or coordinated (for Re=Y) and was associated with a divariant or a monovariant equilibrium of dehydration, respectively. The high temperature anhydrous monoclinic phase LaPO4 or CePO4 formed irreversibly at about 750°C after the total dehydration of the hexagonal hydrated structure while the dehydration of the monoclinic YPO4 . 2H2O phase began from about 190°C with its simultaneous decomposition into tetragonal YPO4. A polytrioxophosphate secondary minor phase Re(PO3)3 resulting from adsorbed H3PO4 was formed at 950°C and decomposed at 1350°C. The particle morphology did not change with the temperature but grain coalescence occurred below 1000°C.
S. Lucas, E. Champion, D. Bernache-Assollant, and G. Leroy, Journal of Solid State Chemistry 177 (2004) 1312-1320

L0103 – Ce0.8Gd0.2O(2-d) ceramics derived from commercial submicron-sized CeO2 and Gd2O3 powders for use as electrolytes in solid oxide fuel cells

Twenty percentage of Gd2O3-doped ceria solid solution has been prepared as an electrolyte for solid oxide fuel cells via the conventional mixed-oxide method from high-purity commercial CeO2 and Gd2O3. The solubility of Gd2O3 in CeO2 in the temperature range of 1300-1700°C has been examined based on the measurements of the lattice parameter. It is found that the dissolution of Gd2O3 in CeO2 is completed at 1600°C for 5 h. The addition of Gd2O3 increases sintering temperature, retards densification, and also depresses grain growth as compared with undoped CeO2. The sample sintered at 1550°C for 5 h has the highest grain boundary conductivity, while the highest grain interior conductivity is achieved for the sample sintered at 1600°C for 5 h. It is also observed that below 500°C, the maximum total conductivity is exhibited by the former sample, but above 500°C, for the latter one.
J. Ma, T.S. Zhang, L.B. Kong, P. Hing, S.H. Chan, Journal of Power Sources 132 (2004) 71-76

L0101 – Mullite phase formation in oxide mixtures in the presence of Y2O3, La2O3 and CeO2

The effect of oxides (Y2O3, La2O3, and CeO2), on phase formation of mullite, reaction sequence and microstructure evolution, in the mixtures of Al2O3 and SiO2, has been investigated. All three dopants showed a positive effect on the mullitization behavior, lowering the mullite formation temperature by about 100°C. The improved mullitization behavior was attributed to the formation of the low-viscosity liquid phase due to the addition of dopants. The reaction sequence was different in the three doping cases. Two types of yttrium silicate were found in the samples doped with Y2O3, with one being favored at low temperature and another at high temperature. No reaction was observed between CeO2 and Al2O3 or SiO2, while La2O3 was not detected by the X-ray diffraction (XRD) measurement for all doping levels. The samples with La2O3 had the best densification behavior among the three doping cases, while the effect of CeO2 on densification was slightly better than that of Y2O3. The difference in the effects of the three oxides on the mullitization and densification behavior of the doped samples implied the difference in the characteristics of the low-viscosity glass phases formed at high temperatures.
L.B. Kong, T.S. Zhang, J. Ma, F. Boey, R.F. Zhang, Journal of Alloys and Compounds 372 (2004) 290-299

L0100 – Structure, nonstoichiometry and magnetic properties of the perovskites Sr(1-x)CaxMnO(3-d)

The structural, thermal and magnetic properties of the perovskite-type alkaline-earth manganites of the series Sr(1-x)CaxMnO(3-d) (0 < x < 1) were investigated. SrMnO(3-d) forms a hexagonal perovskite lattice and shows a first-order transformation to a highly defective cubic high-temperature modification. By substituting Ca for Sr (x > 0.25) the hexagonal perovskite is suppressed and a cubic (or orthorhombic) lattice becomes stabilized for all temperatures. For x = 0.5 and 0.75 cubic perovskites with a large nonstoichiometry (e.g., d = 0.25 for x = 0.5) are obtained at 1400°C. The defective perovskites are prepared by either quenching from high temperature or by cooling in an inert atmosphere. The oxygen vacancies are easily filled by subsequent reoxidation at low temperature (400-600°C) and stoichiometric samples are obtained. Orthorhombic perovskites are formed at T < 1200°C with the nonstoichiometry d increasing with increasing temperature (e.g., d = 0.06 at 1000°C and d = 0.14 at 1200°C for x = 0.5). Slow cooling in air results in almost complete reoxidation (d = 0). CaMnO(3-d) is an orthorhombic perovskite with a large range of nonstoichiometry (0 < d < 0.30). The cubic to hexagonal phase transformation of the Sr-rich samples is accompanied by a large expansion of the lattice that is reduced by Ca substitution. The Ca/Sr-manganites are antiferromagnets with TN of 170 K for x = 0.5 and d = 0.02 and 120 K for x = 1 and d = 0.05.
J. Töpfer, U. Pippardt, I. Voigt, R. Kriegel, Solid State Sciences 6 (2004) 647-654

L0098 – Correlation between densification rate and microstructural evolution for pure alpha alumina

Correlation between microstructural evolution and macroscopic measurements has been investigated on pure alpha alumina under non-isothermal conditions. The densification of different as-received and milled powders of alumina has been monitored during sintering. Densification rate curves as a function of relative density are sensitive to microstructure, such as initial parameters of microstructure (agglomeration, pore size, heterogeneities), and heating schedule (thermal pre-treatment, heating rate). Densifi- cation rate curves can be correlated with microstructural evolution during overall sintering and are expected to be a good help to choose raw materials.
D. Lance, F. Valdivieso, P. Goeuriot, Journal of the European Ceramic Society 24 (2004) 2749-2761

L0097 – Synthesis of fine La0.8Sr0.2MnO3 powder by different ways

La0.8Sr0.2MnO3 (LSMO) powders were successfully synthesized by three routes (sol-gel, spray dryer and conventional solid state method). The precursors were characterized by particle size analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The sintering stage of all powders was also investigated by dilatometer. Finally, the sintered LSMO ceramics have been investigated magnetically and electrically in view to study the ferromagnetic-paramagnetic and/or metal-insulator transition. The magnetoresistance MR up to 42% above room temperature has been observed.
D. Grossin, J.G. Noudem, Solid State Sciences 6 (2004) 939-944

L0096 – Preparation of spherical zirconia powder in microemulsion system and its densification behavior

The water droplets in the microemulsion system of cyclohexane/water/TritonX-100/hexyl alcohol can act as the nano-reactors which solubilize zirconium oxychloride and ammonia separately. The precipitation reactions will take place in the confined spaces determined by the droplets size. The minute original reactors help us obtain nano-size spherical zirconia amorphous powder with uniform diameter distribution and weak aggregate. Such powder begins to crystallize at the temperature about 475°C, and its shrinkage of densification will be elementarily finished from 1080 to 1280°C. The powder is formed by dry pressing process. The 99% relative density and 100% tetragonal phase can be obtained when the green body is sintered at 1400°C for 2 h.
T. Ma, Y. Huang, J. Yang, J. He, L. Zhao, Materials and Design 25 (2004) 515-519

L0095 – Effect of ZrO2 additions on sintering of SnO2-based ceramics

The effect of zirconia additions on sintering of CoO doped tin dioxide has been investigated in the temperature range 1100- 1250°C. A first study showed that the substitution of tin by zirconium reduces significantly the volatilisation rate of SnO2 for temperatures greater than 1400°C. It appeared that the zirconium content increase inhibits the densification kinetics of SnO2-based ceramics. Indeed, the relative density did not exceed 93% for a Zr content lower than 6 mol% in the Sn(1-x)ZrxO2 solid solution. This negative effect can be imputed to the elastic distortions caused by the introduction of Zr in the tin dioxide lattice. So, the diffusion rate of point defects such as oxygen or cobalt ions is lowered.
A. Maître, D. Beyssen, R. Podor, Journal of the European Ceramic Society 24 (2004) 3111--3118

L0090 – Physical properties of BaMg(1/3)Nb(2/3)O3-BaCo(1/3)Nb(2/3)O3 solid solutions

Structural, electric and magnetic properties of Ba3Mg(1-x)CoxNb2O9 based dielectric ceramic compounds have been studied. The samples, prepared by a solid state reaction method, were characterised by X-ray powder diffraction (XRPD), electron microscopy (SEM), dielectric (epsilon(T)) and magnetic measurements (khi-1(T)). The XRPD analyses showed that the crystal structure of these compounds does change by the increase of substitution degree, passing froma superstructure hexagonal-type, P3m1 (no. 164), space group (SG) to a simple structure cubic-type, Pm3m (no. 221), SG. However, the evolution of the elementary unit cell lattice parameter can be followed and it exhibit a linear increasing tendency with increase in the substitution, indicating the existence of a solid solution through out the investigated range of substitution (0-1). Themicrostructure analysis shows a variation inthe grain size and also the porosity of the samples with the degree of substitution. The results are in good agreement with that of dielectricmeasurements, which also showed that the dielectric constant (epsilon) increases with the increase of cobalt content. The magnetic characterization of cobalt substituted samples showed an antiferromagnetic type super-exchange interaction between thesemagnetic ions. At the same time, the values of effective magnetic momentum (µeff) are close to the value that corresponds to Co2+ free ions. The study highlights the possibility of modelling these materials by substitutions, in order to improve properties of negative-positive-zero (NPO) type dielectric applications.
A. Veres, S. Marinel, M. Pollet, Journal of Physics and Chemistry of Solids 67 (2006) 822-827

L0088 – Mechanical and thermal expansion behavior of hipped aluminum-TiB2 composites

Aluminum-TiB2 composites reinforced with 5-20 vol.% ceramic particles were prepared by powder metallurgy (PM) method. Hot isostatic pressing was employed to consolidate the green PM products. The microstructure of metal matrix composites (MMCs) was found to depend greatly on the relative particle size (RPS) ratio between the aluminum and ceramic particles. Microstructural examination revealed that RPS value of 0.56 favors both the densification of MMC compacts and better uniform distribution of ceramic particles. Tensile measurements showed that the Young's modulus and ultimate tensile strength of the Al-TiB2p MMCs tend to increase with increasing TiB2p volume content at the expense of tensile ductility. Thermal expansion property of hipped MMCs was measured in the temperature range from 85 to 600°C. The results showed that the increase in the volume fraction of TiB2 reinforcement reduces the coefficient of thermal expansion (CTE) of the Al-TiB2 composites. Moreover, the CTE versus temperature plots exhibited an apparent peak minimum at ~380°C during the first heating stage for the composites reinforced with TiB2 >15 vol.%. This peak corresponds to the onset of relaxation for the compressive stress, leading to the Al matrix to deform plastically.
S.C. Tjong, K.F. Tam, Materials Chemistry and Physics 97 (2006) 91-97

L0086 – Evidence of the formation of a new rock-salt type compound Li2MgTiO4 and of its role on the properties of the Li doped MgTiO3

This work deals with the sintering of MgTiO3 in presence of Lithium salt and more precisely with lithium halide. These last sintering agents lead to the formation of a new rock-salt type structure Li2MgTiO4. This new phase was synthesized by a classical solid-state route and their electric and dielectric properties were characterize. The formed material is a type I dielectric material with a permittivity close to 12 with dielectric losses inferiors to 0.3% in the range of -50 to 150°C. X-ray diffraction and investigation by TEM were also performed. The influences of the formation of this new phase on the properties of MgTiO3 are described here.
J. Bernard, D. Houivet, M. Hervieu, J.M. Haussonne, Solid State Sciences 8 (2006) 598-605

L0081 – The rock salt oxide Li2MgTiO4: Type I dielectric and ionic conductor

The exploration of the Li-Ti-Mg-O system, using both sol-gel technique and solid state reaction method, allowed a new phase, Li2MgTiO4, with disordered rock salt structure (a = 4.159 Å ) to be synthesized. The latter is shown to be a good type I dielectric material, with a relative constant of 15 at high frequency and low dielectric loss (tand < 10^(-3)) over the temperature range - 60 to 160°C. It is also observed that the sintering temperature of this phase is strongly lowered by adopting the sol-gel technique compared to solid state reaction (1150°C instead of 1300°C). Finally we show that this phase exhibits cationic conductivity above 400°C (s600°C = 9 x 10^(-5) S cm-1).
M.V.V.M. Satya Kishore, S. Marinel, V. Pralong, V. Caignaert, S. D'Astorg, B. Raveau, Materials Research Bulletin 41 (2006) 1378-1384

L0080 – A novel low temperature sintering process for PMnN-PZT ceramics

Samples with the composition of 0.07Pb(Mn1/3Nb2/3)O3-0.468PbZrO3-0.462PbTiO3 was prepared in this study. A novel process was adapted to lower the sintering temperature without properties deterioration. The sintering process includes a vacuumed heating stage, a air-venting heating stage, and a final sintering at 1050°C with certain holding time without PbO compensating atmosphere. The influence of holding time at the final sintering stage on the characteristics of the ceramics was studied. The air-venting stage caused a large shrinkage (about 10%) and then slowing down the shrinking rate when the sample was heated up from 800 to 1050°C. The relationships between the crystalline characteristics and physical properties, such as microstructure, the mechanical quality factor (Qm), and electromechanical coupling factor (kp), are discussed in this paper.
C-Y. Chen, Y. Hu, H-L. Lin, Materials Chemistry and Physics 99 (2006) 26-29

L0076 – Modelling of the grain growth and the densification of SnO2-based ceramics

This work consisted in the kinetic study of grain growth and densification processes for SnO2 and Sn0.94Zr0.06O2 ceramics between 1100 and 1200°C. From dilatometric experiments, it appeared that zirconia additions inhibited the final densification rate. For pure SnO2, the rate limiting step of the densification mechanism would correspond to the grain boundary or volume diffusion. From normal grain growth kinetics, the corresponding limiting step has been identified, i.e. either the surface diffusion in pores or grain boundary diffusion for ZrO2 free-SnO2 and Sn0.94Zr0.06O2, respectively. All of these results permit establishing the corresponding sintering map. For pure SnO2 ceramic, the experimental data have been well restored by modelling.
A. Maître, D. Beyssen, R. Podor, Ceramics International xxx (2007) xxx-xxx

L0075 – Effects of the sintering atmosphere on Nb-based dielectrics

The effects of a forming atmosphere on the stability, the sintering and the dielectric properties of Ba5Nb4O15, BaNb2O6, ZnNb2O6 and Zn3Nb2O8 ceramics were investigated, because of the primary importance of the sintering atmosphere in relation to copper sintering. These Nbbased materials were sintered in air and in Ar/H210%. Zn-containing samples are very sensitive to the reductive atmosphere. ZnO volatilises at 800-850°C and the resulting compound does not exhibit the expected properties. BaNb2O6 and Ba5Nb4O15 are more stable in term of relative weight loss. Nevertheless, the phase analysis reveals a modification of the BaNb2O6 phase, what induces the degradation of the dielectric property stability versus temperature. The properties of Ba5Nb4O15 are not modified by a sintering in reductive atmosphere. A relative permittivity of 38.8, a permittivity temperature coefficient of -150 ppm°C-1 and an insulating resistivity of 10^10.9 V cm were obtained for this latter.
S. d'Astorg, S. Marinel, Ceramics International xxx (2007) xxx-xxx

L0074 – Preparation and properties of dense Ce0.9Gd0.1O(2-d) ceramics for use as electrolytes in IT-SOFCs

Gd-doped ceria solid solutions have been recognized to be leading electrolytes for use in intermediate-temperature fuel cells. In this communication, it reported on the preparation, solubility and densification of Ce0.9Gd0.1O(2-d) ceramics derived from carbonate coprecipitation. The dissolution of Gd2O3 in CeO2 lattice was identified to complete during coprecipitation process by studying lattice parameter against temperature. The calcining temperature was found to have a significant influence on the densification behavior and final sintered density for the carbonatecoprecipitated powder. The samples prepared from the powder calcined at <700°C had an expansion at ~1250 to 1400°C during sintering, and thus lowered sintered density. 800°C was identified to be an optimal calcining temperature for carbonate-coprecipitated powder. The powder calcined at 800°C for 2 h had a mean crystalline size of ~25 nm with nearly spherical shape and narrow particle-size distribution, which had a maximum densification rate at ~1190°C. This temperature (of maximum densification rate) could further be reduced to ~1080°C for the carbonate-coprecipitated powder by adding 0.5 at.% FeO1.5 (atomic ratio). At 1200°C for 5 h, over 98% relative density with an average grain size of ~1.2µm was obtained for the 0.5 at.% Fe-loaded Ce0.9Gd0.1O(2-d) ceramics. Fe loading was also found to have a positive effect on grain boundary conductivity of Ce0.9Gd0.1O(2-d) ceramics. An increase in the grain boundary conduction by over two times was achieved in the present work for the 0.5 at.% Fe-loaded Ce0.9Gd0.1O(2-d) ceramics.
T.S. Zhang, J. Ma, L.H. Luo, S.H. Chan, Journal of Alloys and Compounds 422 (2006) 46-52

L0073 – Abnormal thermal expansion and thermal stability of Ti3Al(1-x)SixC2 solid solutions

Ti3Al(1-x)SixC2 solid solutions exhibited abnormal high coefficients of thermal expansion at temperatures of >940°C during heating, which was ascribed to the precipitation of Si as Ti5Si3. Ti5Si3 phase usually located at the grain boundaries of the solid solutions.
J.X. Chen, Y.C. Zhou and J. Zhang, Scripta Materialia 55 (2006) 675-678

L0071 – Influence of the synthesis route on sol-gel SiO2-TiO2 (1:1) xerogels and powders

Five different sol-gel routes are used in order to synthesize mixed SiO2-TiO2 materials. Simple mixing of the Ti and Si precursors, prehydrolyzing of TEOS, modification of the Ti alkoxide with acetic acid, isoamyl alcohol and acetylacetone lead to translucent gels with different time of gelation. Different techniques such as TGA, DTA, XRD and IR spectroscopy are used to characterize each material. IR spectroscopy revealed the presence of Si-O-Ti and Si-O-Si bonds for all the xerogels letting suppose a composite microstructure of the gels. Pre-hydrolyzing of TEOS and modification of Ti alkoxide with isoamyl alcohol are the most appropriate routes to retain the anatase phase up to 1100°C.
S. Vives, C. Meunier, Ceramics International xxx (2007) xxx-xxx

L0070 – Proton conduction in ceria-doped Ba2In2O5 nanocrystalline ceramic at low temperature

Sintered pellets of Ce-doped Ba2In2O5 (BIC) were prepared from nanopowders. The electrical conductivities were measured using ac impedance spectroscopy under different atmospheres and temperatures. The electrical conductivity of sintered BIC was found sensitive to environmental humidity when the temperature was below 300°C. However, in the presence of hydrogen, the electrical conductivities were independent of water content in the range of 0-30 vol%. The electrical conductivities of BIC were significantly affected by the presence of hydrogen in a temperature range of 100-300°C. The estimated protonic transference number and the measured open circuit voltage suggested the existence of electronic conduction. The coefficient of thermal expansion of BIC is 11.2x10^(-6) K-1 from 25 to 1250°C.
R. Hui, R. Maric, C. Decès-Petit, E. Styles, W. Qu, X. Zhang, J. Roller, S. Yick, D. Ghosh, K. Sakata, M. Kenji, Journal of Power Sources 161 (2006) 40-46

L0069 – A study on sintering aids for Sm0.2Ce0.8O1.9 electrolyte

In this study, an addition of Co oxide or Cu oxide to Sm0.2Ce0.8O1.9 (SDC) was studied to improve the sinterability of SDC. It has been found that both Co and Cu oxide are very effective as sintering aids, and the SDC sintering temperature can be reduced from 1400°C without aids to below 1000°C with only 1 at.% of either Cu oxide or Co oxide. As compared to the pure SDC, a slight decrease of ionic conductivity was observed in SDC with Cu sintering aid. There is no obvious effect on electrochemical property of SDC with Co sintering aid under 2.5 at.%.
X. Zhang, C. Decès-Petit, S. Yick, M. Robertson, O. Kesler, R. Maric, D. Ghosh, Journal of Power Sources 162 (2006) 480-485

L0068 – Electrical properties of low-density polyethylene/multiwalled carbon nanotube nanocomposites

Low-density polyethylene (LDPE)/multiwalled carbon nanotube (CNT) nanocomposites were prepared via melt compounding. The electrical properties of LDPE/CNT nanocomposites as a function of CNT volume content, frequency and temperature were investigated. The results showed that dielectric constant of LDPE/CNT nanocomposites increases slightly with increasing CNT content up to 1.9 vol.%. Thereafter, the dielectric constant of the nanocomposites increases sharply. The dielectric constant of LDPE/3.6 vol.% CNT nanocomposite is more than two orders of magnitude larger than that of pure LDPE. The frequency dependence of electrical properties of LDPE/3.6 vol.% CNT nanocomposite can be well described by the percolation theory.
G.D. Liang, S.C. Tjong, Materials Chemistry and Physics 100 (2006) 132-137

L0067 – Low temperature sintering of ZnTiO3/TiO2 based dielectric with controlled temperature coefficient

Structure, microstructure and dielectric properties of ZnTiO3 and rutile TiO2 mixtures (ZnTiO3 + xTiO2 with x = 0, 0.02, 0.05, 0.1, 0.15 and 0.2) sintered using ZnO-B2O3 glass phase (5 wt.% added) as sintering aid have been investigated. For all compounds, the sintering temperature achieves 900°C. The X-ray diffraction patterns indicate for x = 0.1 that the material is composed by three phases identified as ZnTiO3 hexagonal, TiO2 rutile and ZnO. The presence of ZnO is explained by the introduction of Ti into Zn site to form the (Zn1-xTix)TiO3+x solid solution in resulting the departure of ZnO from the ZnTiO3 structure. The ZnTiO3 + 0.15TiO2 composition sintered at 900°C with glass addition exhibits attractive dielectrics properties (Er = 23, tan(delta) < 10^(-3) and a temperature coefficient of the dielectric constant near zero (t = 0 ppm/°C)) at 1 MHz. It is also shown that the introduction of TiO2 allows to tune the temperature coefficient of the permittivity. All these properties lead this system compatible to manufacture silver based electrodes multilayer dielectrics devices.
A. Chaouchi, S. Marinel, M. Aliouat, S. d'Astorg, Journal of the European Ceramic Society 27 (2007) 2561-2566

L0066 – Synthesis and sintering of a monazite-brabantite solid solution ceramic for nuclear waste storage

Various geological arguments suggest that monazite can be an interesting waste-form for actinides such as Np, Pu, Cm and Am. We set up a simple procedure for making dense pellets of monazite-brabantite solid-solution ceramics with composition Ca0.092Th0.092 Ce0.089La0.727PO4. It consists of co-milling CaCO3, ThO2, CeO2, La2O3, and NH4H2PO4, 1250°C calcination, milling, cold-pressing, and sintering at 1450°C for 4 h. X-ray investigations showed that the reaction scheme from oxides to monazite is complex and involves various P+La-based intermediate compounds. The final density of the the product is around 95% of the theoretical density. The texture is homogeneous with a typical grain of size 5-20 mm. This process is designed to be adapted to hot cells and telemanipulators.
J-M. Montel, B. Glorieux, A-M. Seydoux-Guillaume, R. Wirth, Journal of Physics and Chemistry of Solids 67 (2006) 2489-2500

L0064 – Microwave synthesis and characterization of metastable (Al/Ti) and hybrid (Al/Ti + SiC) composites

Two-directional microwave assisted rapid sinteringwas carried out to fabricate Al/Ti metastable composites and Al/(Ti + SiC) hybrid composites. The length scale of Ti was in microns (20µm) and of SiC in nanometers (50 nm). Microstructural characterization revealed uniform distribution of Ti particulates and SiC nanoparticulates in the Al matrix, relatively low amount of porosity and good matrix-reinforcement interfacial integrity. Coefficient of thermal expansion of the Al matrix reduced due to the presence of Ti and Ti + SiC reinforcements. The results revealed that addition of SiC nanoparticulates to Al-Ti formulations assisted in increasing microhardness, macrohardness, Al-Ti interfacial hardness, 0.2% YS and UTS while the ductility was marginally affected. Particular emphasis was placed to study the feasibility of using hybrid reinforcements in the Al matrix synthesized by using microwaves.
S.K. Thakur, T.S. Kong, M. Gupta, Materials Science and Engineering A 452-453 (2007) 61-69

L0063 – Rheological behaviour of kaolin/talc/alumina suspensions for manufacturing cordierite foams

This paper deals with the preparation and rheological charaterization of concentrated suspensions (40 vol.% solids) of mixtures of kaolin/talc/alumina to relative weight contents of 40/43.8/16.2, respectively. These concentrated suspensions were thixotropic and viscosus, the rheological properties being largely influenced by a number of processing parameters, the most relevant being the nature and content of deflocculant and the pH value. Best results were obtained for a polyacrylic-based polyelectrolyte and pH 11. Green densities of 59 % of TD were obtained. Dynamic and static sintering studies were performed and the analysis of the resulting phases was made by XRD. From these tests it was concluded that cordierite phase needed a thermal treatment of 1300ºC to be formed. The sintered slip cast materials have a large residual porosity because of the coarse particle size of the raw materals. Macroporous cordierite foams are obtained by impregnation of polyurethane foam into the optimized slip and heating at 1350ºC/1h with a burning out step at 550ºC/30 min.
J.B. Rodrigues Neto, R. Moreno, Applied Clay Science 37 (2007) 157-166

L0062 – Modelling WC-Co sintering shrinkage – Effect of carbide grain size and cobalt content

Phenomenological models based on the constitutive parameters uniaxial viscosity, viscous equivalent of Poisson's ratio and sintering stress are used to describe WC-Co sintering shrinkage. Shrinkage is divided into three subsequent stages. The influences of carbide grain size and cobalt content are accounted for and model parameters numerically adjusted to dilatometer results. The model successfully represents published shrinkage data for different materials and milling procedures.
A. Petersson, J. Ågren, Materials Science and Engineering A 452-453 (2007) 37-45

L0061 – Wetting, densification and phase transformation of La2O3/A2O3/B2O3-based glass-ceramics

A lead-free, non-alkali La2O3-Al2O3-B2O3 (LAB) glass with Al2O3 filler had been investigated for low temperature co-firing ceramic (LTCC) application. The glass forming window and several physical properties of the LAB systems were investigated by ICP, TMA, XRD, DSC, and SEM/EDS. The results show that the densification and crystallization temperatures of LAB/Al2O3 were between 700°C and 950°C and depended greatly on the formulation. Crystalline phase LaBO3 (LB) and LaAl2B3O9 (L2A3B) crystallized starting at 825°C and 925°C, respectively. High degree of densification and crystallization of one glass-Al2O3 composition (L30A) was observed with the microstructure composed of tabular L2A3B grains interlocking with submicron Al2O3 and LB grains.
C-L. Chen, W-C.J. Wei, A. Roosen, Journal of the European Ceramic Society 26 (2006) 59-65

L0060 – Processing and characterization of ultra-thin yttria-stabilized zirconia (YSZ) electrolytic films for SOFC

Sub-micron yttria-stabilized zirconia (YSZ) electrolyte layer was prepared by a liquid state deposition method and with an average thickness of 0.5 Am to improve the performance of the anode-supported solid oxide fuel cell (SOFC). The YSZ precursors, containing yttrium and zirconium species and an additive, poly-vinyl-pyrrolidone (PVP), were spin-coated on a Ni/YSZ anode substrate. Several properties, including crystalline phases, microstructures, and current-voltage (I -V) characteristics, were investigated. The thin film of 4 mol% Y2O3-doped ZrO2 (4YSZ) consisted of cubic, tetragonal, and a trace of monoclinic phases, and showed a crack-free layer after sintering at 1300°C. The anode supported SOFC, which consists of the Ni-YSZ anode, 4YSZ electrolyte, and Pt/Pd cathode, showed power densities of 477 mW/cm2 at 600°C, and 684 mW/cm2 at 800°C. Otherwise, the surface cracks of the other YSZ-coated samples (e.g. 8YSZ) can be repaired by a multi-coating method.
Y-Y. Chen, W-C.J. Wei, Solid State Ionics 177 (2006) 351 - 357

L0059 – High-temperature thermal characterization

G. Etherington, Ceramic Industry, feb 2007

L0058 – The current detour effect observed on materials with random microstucture: experimental evidence from Li3xLa2/3-xTiO3 studied by impedance spectroscopy

Impedance spectroscopy (IS) has been used to study the influence on the low frequency part of the impedance diagrams of the microstructure of a fast ionic conductor, Li3xLa2/3-xTiO3 with x = 0.10 (named hereafter LLTO). This oxide has been synthesised by sol-gel method. After synthesis, the powder of LLTO displays a large distribution of grain size and agglomerates. The grain size distribution and the porosity of the ceramic have been changed by heat-treatment from 600°C to 1200°C in air. The impedance spectra of these ceramics, recorded at different temperatures from room temperature (RT) to 400°C, show a low-frequency depressed arc, which is characteristic of the grain boundary response of the ceramic. Its shape depends strongly on the heat-treatment of the ceramic, and therefore, on its microstructure. It is a simple arc when the pellet is well sintered but becomes very complex for non-sintered ceramics with high resistive grain boundary and pores. The observed "fish" shape indicates the presence of current "detours effect" in the material. This effect means that current detours around blocking grain boundary and/or pores occur to lower the impedance. Consequently, the brick layer model (BLM), which assumes an ideal microstructure, and then no current "detours effect", can not be used to analyse these impedance data.
M. Vijayakumar, O. Bohnke, Journal of the European Ceramic Society 26 (2006) 3221-3231

L0056 – Piezo-spectroscopic characterization of alumina-aluminium titanate laminates

A multilayered alumina-aluminium titanate composite was prepared by a colloidal route from aqueous suspensions. The structure of the laminate was symmetric and constituted of two external Al2O3 layers (width=1750 µm), one central Al2O3 layer (width=1200 µm) and two intermediate thin (width=315-330 m) Al2O3-Al2TiO5 layers. Additional monolithic materials with the same compositions as those of the layers were fabricated as reference materials. Young's modulus of the monoliths was determined by three point bending. Dilatometry determinations were performed on green specimens, following the same heating and cooling schedules as those used for sintering the laminate, in order to determine the actual dimensional changes on cooling after sintering. The dimensional changes of the sintered specimens on heating and on cooling were also determined. Microscopic distributions of residual stresses were evaluated by fluorescence piezo-spectroscopy, and they revealed the existence of weak tensile and compressive hydrostatic stresses in the aluminium titanate and alumina layers, respectively. The level and sign of these stresses was in good agreement with those predicted based on analysis of the Young's modulus and the dimensional variations during cooling after sintering of the monoliths with the same compositions as those of the layers. Dimensional variations during cooling after sintering were different from those for sintered materials, which presented hysteresis between heating and cooling. In spite of the presence of compressive residual stresses in the external layers of the laminate, strength values of notched samples of the laminated specimens were lower than those for monoliths of the same composition as the external layers.
G. de Portu, S. Bueno, L. Micele, C. Baudin, G. Pezzotti, Journal of the European Ceramic Society 26 (2006) 2699-2705

L0055 – Ce4+ modified cordierite ceramics

A dense, low thermal expansion cordierite ceramic was prepared by the co-precipitation method and Ce4+ addition. Ce4+ addition can inhibit m-cordierite crystallization and improve a-cordierite crystallization. Adding 3.2 wt.% Ce4+ enables density and mechanical strength to reach maximum values with a minor increase in thermal expansion coefficient.
Z.M. Shi, X. Bai, X.F. Wang, Ceramics International 32 (2006) 723-726

L0054 – Electrical and thermal properties of La0.7Sr0.3Ga0.6Fe0.4O3 ceramics

Single-phase La0.7Sr0.3Ga0.6Fe0.4O3 (LSGF) ceramic powder was prepared in one step at 1500°C by solid-state reaction in air. The phase is a hexagonal (space group R-3c) at room temperature but becomes cubic at temperatures above 600°C. A high-density (97%) LSGF ceramic shows electrical conductivity of 4.3 S/cm (Ea = 0.32 eV) at 600°C in air. The thermal expansion coefficient of LSGF changes drastically in air due to oxygen loss and phase transition. High-density LSGF ceramic is relatively stable in forming gas (8% H2, 92% Ar). However, the powder decomposes in forming gas above 700°C with formation of LaSrGaO4. LSGF reacts with NiO at 1000°C. The ability of LSGF to split the C-H bond in methane at intermediate temperatures has been also evaluated.
S. Koutcheiko, P. Whitfield, I. Davidson, Ceramics International 32 (2006) 339-344

L0053 – Processing of Al2O3/Y-TZP laminates from water-based cast tapes

Laminated structures have been investigated due to their capability for the reinforcement of ceramics. Crack deflexion and bifurcation, surface strengthening and threshold strength are the mechanisms associated to the fracture of laminated ceramic. In all the cases, a precise control of the thickness and composition of the layers is necessary. In this sense, colloidal processing techniques have proved their adequacy for the fabrication of designed layered structures. This paper deals with the fabrication of layered ceramics by stacking water-based cast tapes at room temperature and using low pressures. In order to control the pressing procedure, the engineering strain-stress curves recorded during the stacking of the tapes were analyzed. Afterwards, the sintering conditions have been optimized by adjusting the green density of the tapes to avoid differential sintering and the associated cracks. Monolithic and layered materials free of cracks have been fabricated using optimized processing conditions.
A.J. Sanchez-Herencia, J. Gurauskis, C. Baudin, Composites: Part B 37 (2006) 499-508

L0052 – Effect of ceria on properties of yttrium-doped strontium titanate ceramics

This work reports the preparation and properties of the ceramic mixtures of the A-site deficient perovskite Sr0.94Y0.04TiO3 (SYT) with CeO2 in a range of ratios with a view to establishing their potential as anode materials for solid oxide fuel cells. Good electrical conductivity that decreased with increasing CeO2 content was observed on reduction in forming gas. The composition with 50 wt.% of CeO2 showed the conductivity of 7.0 S/cm at 900°C in forming gas. The thermal expansion of SYT-CeO2 ceramics in forming gas and in air were investigated in the range 25-900°C at a ramping rate of 3°C/min and thermal expansion coefficients were determined. The addition of ceria was found to have a positive influence on the catalytic behavior of SYT-CeO2 ceramics towards steam methane reforming.
S. Koutcheiko, Y. Yoo, A. Petric, Isobel Davidson, Ceramics International 32 (2006) 67-72

L0051 – Sintering and microstructure of rare earth phosphate ceramics REPO4 with RE = La, Ce or Y

Sintering of rare earth phosphates REPO4 (RE = La, Ce or Y) was studied using dilatometry. The presence of a secondary rare earth metaphosphate phase RE(PO3)3 as sintering aid was investigated. It proved to accelerate the densification but it activated fast grain growth, which was very detrimental to the microstructural design of processed ceramics. A temperature of 1400-1450°C was required to sinter pure LaPO4 and CePO4 ceramics with fine grains. Both compounds behave similar while YPO4 did not densify even at 1500°C. The influence of specific surface area of starting powders, temperature and holding time on the sintering rate and microstructures of dense REPO4 materials is also reported.
D. Bregiroux, S. Lucas, E. Champion, F. Audubert, D. Bernache-Assollant, Journal of the European Ceramic Society 26 (2006) 279-287

L0050 – Ba(Zn1/3Nb2/3)O3 sintering temperature lowering for silver co-sintering applications

The complex perovskite oxide Ba(Zn1/3Nb2/3)O3 have been broadly studied due to its attractive dielectric properties which place this material as a good candidate for manufacturing type I capacitors or hyperfrequency resonators. The development of Base Metal Electrodes Multi Layer Ceramic Capacitors (BME-MLCC) require a low sintering temperature to be co-sintered with a low cost metal such as copper or silver. Unfortunately, BZN requires a high temperature (1350°C according to the literature) to reach a satisfactory density (>90% of the theoretical one). The aim of this work is to lower the BZN sintering temperature to allow a co-sintering with copper or silver electrodes. For this goal, different sintering agents (lithium salts and glass phases) have been tested on the nominal compound. It is shown that an addition of 10 molar% B2O3 combined with 5 molar% LiF authorises a sintering temperature lowering near to 350°C. If a slight non-stoichiometry in A site is combined to these sintering agents, it is possible to reach a sintering temperature lower than 950°C without affecting the basic material properties. For each composition obtained, the ceramic is characterised in terms of final density, microstructure and dielectric properties. The silver co-sintering is also performed.
F. Roulland, S. Marinel, Ceramics International 32 (2006) 377-383

L0049 – Titanium effect on phase transformation and sintering behavior of transition alumina

The sintering behavior of doped gamma-alumina powders studied by dilatometry and electron microscopy is analysed with a particular emphasis on the role of titanium on the various densification steps. Compared with other doping elements, such as Mg, Y and Zr, which do not improve alpha-phase densification, titanium enhances this densification step by a fast decrease of internal colony porosity. This internal densification of single crystalline zones is attributed to the lengthening of the elementary bricks in titanium-doped samples.Atransient increase in densification rate is also observed, corresponding to the precipitation when during grain growth, grain boundaries become saturated with titanium. Final densities close to the theoretical values are obtained.
S. Lartigue-Korinek, C. Legros, C. Carry, F. Herbst, Journal of the European Ceramic Society 26 (2006) 2219-2230

L0048 – Effect of type of primary processing on the microstructure, CTE and mechanical properties of magnesium/alumina nanocomposites

Magnesium based composites containing 2.5wt.% of nano-sized Al2O3 (50nm) particulates reinforcement were synthesized using an innovative disintegrated melt deposition technique and blend-press-sinter powder metallurgy technique followed by hot extrusion. Microstructural characterization of the materials revealed uniform distribution of reinforcement, grain refinement and the presence of minimal porosity. Properties characterization revealed that the presence of nano-Al2O3 particulates led to an increase in dimensional stability, hardness, elastic modulus, 0.2% yield strength, UTS and ductility of pure magnesium. Amongst the composites, the ingot metallurgy processed material exhibited superior modulus and ductility while powder metallurgy processed material exhibited superior yield strength and ultimate tensile strength. The results further revealed that the overall combination of tensile properties of these materials remained superior when compared to high strength magnesium alloy AZ91 reinforced with much higher weight percentage of SiC. Fractography studies revealed that the typical brittle fracture of pure magnesium changed to ductile due to the incorporation of nano-Al2O3 particulates. An attempt is made in the present study to correlate the effect of nano-sized Al2O3 particulates as reinforcement and processing type with the microstructural and tensile properties of magnesium.
S.F. Hassan, M. Gupta, Composite Structures 72 (2006) 19-26

L0046 – Elaboration and characterisation of apatite based mineral supports for microfiltration and ultrafiltration membranes

The development and the characterisation of new supports for microfiltration and ultrafiltration membranes from apatite applied to filtration are presented. The choice of this material is based primarily on its low cost (considering its abundance in the Tunisian ores). The support, with tubular configuration, was prepared from natural apatite: apatite powders were crushed for 30 min and sieved to 200 mm. The resulting powders, mixed with organic additives and water, could be extruded to elaborate a porous structure. The firing temperature of the support is 1160°C. The morphologies of the surface and the cross-section observed on scanning electron microscope (SEM) are homogeneous and do not present any macro defects (cracks, etc.). The mean pore diameter, measured by mercury porosimetry, is 6 mm and the pore volume is 48%.
S. Masmoudi, A. Larbot, H. El Feki, R. Ben Amar, Ceramics International 33 (2007) 337-344

L0045 – Electrical and microstructural characterization of spinel phases as potential coatings for SOFC metallic interconnects

Several spinel samples, i.e., MnxCr3-xO4 (0.5
W. Qu, L. Jian, J.M. Hill, D.G. Ivey, Journal of Power Sources 153 (2006) 114-124

L0044 – Enhancing strength and ductility of Mg/SiC composites using recrystallization heat treatment

In the present study, magnesium composites with sub-micron size silicon carbide (SiC) particulate reinforcements were successfully synthesized using an innovative Disintegrated Melt Deposition technique followed by hot extrusion. The extruded materials were characterized for their microstructural, thermal and mechanical properties. Systematic investigations on the microstructure of the extruded samples revealed a fairly uniform distribution of SiC particulates with limited clustering. Good SiC/Mg interfacial integrity and limited porosity was observed for all the samples. The results of the properties characterization revealed that SiC in sub-micron length scale are more effective in lowering CTE, and enhancing hardness, 0.2% yield strength, and ultimate tensile strength when compared to SiC particulates in micron length scale. Subsequently, isothermal heat treatment at 150°C for 5 h was carried out for the composite samples. The results of tensile testing revealed that the heat treated samples showed an improvement of 0.2% YS, UTS and ductility. Particular emphasis is placed in this study to investigate the effect of heat treatment at the recrystallization temperature on the tensile properties of magnesium.
S. Ugandhar, M. Gupta, S.K. Sinha, Composite Structures 72 (2006) 266-272

L0042 – Cofiring behavior and interfacial structure of NiCuZn ferrite/PMN ferroelectrics composites for multilayer LC filters

The cofiring behavior, interfacial structure and cofiring migration between NiCuZn ferrite and lead magnesium niobate (PMN)-based relaxor ferroelectric materials were investigated via thermomechanical analyzer (TMA), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Mismatched sintering shrinkage between NiCuZn ferrite and PMN was modified by adding an appropriate amount of sintering aids, Bi2O3, into NiCuZn ferrite. Pyrochlore phase appeared in the mixture of NiCuZn ferrite and PMN, which is detrimental to the final electric properties of LC filters. EDS results indicated that the interdiffusion at the heterogeneous interfaces in the composites, such as Fe, Pb, Zn, existed which can strengthen combinations between ferrite layers and ferroelectrics layers.
C. Miao, J. Zhou, X. Cui, X. Wang, Z. Yue, L. Li, Materials Science and Engineering B 127 (2006) 1-5

L0041 – Surface resistance and sensitivity to hygrometry of various ceramic compositions for multilayer capacitors

Developing new dielectric compositions for multilayer ceramic capacitors, the authors of this work have observed an influence of hygrometry on the insulation resistance behavior of some of them. The swiftness of the phenomenon let us suppose a surface mechanism. Prompted by these observations, we have investigated the sensitivity of various conventional ceramic compositions to hygrometry by measuring their surface resistance versus the moisture rate in air. The studied materials are formulations for type I and type II ceramic capacitors. In order to understand some breakdown phenomena in ceramic multilayer capacitors, we have also investigated the influence of the screen printed electrodes composition.
J. Bernard, D. Houivet, J-M. Haussonne, Journal of the European Ceramic Society 25 (2005) 2977-2979

L0040 – Low temperature sintering of MgTiO3 with bismuth oxide based additions

MgTiO3 is a classical material for type I MLCC. However, its densification temperature is too high to allowco-sintering with copper electrodes. Investigations into low temperature sintering of MgTiO3 show the complexity of this problem particularly when co-sintering with copper electrodes and thus a reducing atmosphere are involved in the process. Though feasibility of MgTiO3/copper MLCC seem to be possible [Bernard, J., Houivet, D., El Fallah, J. and Haussonne, J. M., MgTiO3 for base metal multilayer ceramic capacitors. J. Eur. Ceram. Soc., 2004, 24, 1877-1881] studies have pointed out several remaining problems such as sensibility to hygrometry [Bernard, J., Houivet, D., El Fallah, J. and Haussonne, J. M., Effect of hygrometry on dielectric materials. J. Eur. Ceram. Soc., 2004, 24, 1509-1511]. Investigations into low temperature sintering of MgTiO3 are thus still necessary to find a formulation which is not detrimental to dielectric behaviour. Sintering aid capabilities and/or good dielectric properties of bismuth oxide based additives make them good candidate materials to lower MgTiO3 sintering temperature without altering its final properties. In this study bismuth titanate is either formed in situ by reaction-sintering of Bi2O3-B2O3 additives with MgTiO3 or obtained by pre-calcination of Bi2O3 and TiO2 powders and then added to MgTiO3 prior to sintering. Bismuth titanate appears as a good sintering aid that allows sintering of MgTiO3 under 1000°C. It is however highly sensitive to the nature of the sintering atmosphere, oxidizing or reducing. Dielectric properties of sintered specimens are compatible with type I capacitors applications.
F. Belnou, J. Bernard, D.d Houivet, J-M. Haussonne, Journal of the European Ceramic Society 25 (2005) 2785-2789

L0039 – Low sintering temperature of MgTiO3 for type I capacitors

Magnesium titanate MgTiO3 is a well-known compound for type I multilayer ceramic capacitors. Nevertheless, the sintering temperature of the pure ilmenite MgTiO3 is around 1350°C. Such a high sintering temperature together with the high sensitivity of the dielectric material to reduction when heated in a low-oxygen containing atmosphere implies that MgTiO3-based MLCC include palladium-rich inner electrodes. The high level of variation of both the costs of Pd and Ag justifies research leading to the use of cheaper metals such as silver or base metals such as nickel or copper. When using low-melting temperature metals (silver melts at 960°C and copper at 1085°C), the sintering temperature of the dielectric material has to be lowered.We report here on our investigations into the use of fluorine containing additives for the reducing of the sintering temperature of magnesium titanate, showing the ability of this material to be sintered at temperatures much lower than 1000°C. Both dielectric and electric properties of such ceramics are compatible with type I capacitors requirements.
J. Bernard, F. Belnou, D. Houivet, J-M. Haussonne, Journal of the European Ceramic Society 25 (2005) 2779-2783

L0038 – High decrease in CaZrO3 sintering temperature using complex fluoride fluxes

The effects of complex fluoride flux on the sintering and the electric/dielectric properties of CaZrO3 ceramics are investigated. Four fluoride mixtures are tested: LiF-CaF2-SrF2, LiF-CaF2-BaF2, LiF-SrF2-BaF2 and LiF-BaF2-B2O3. They are used because each of their associated phase diagrams shows the existence of an eutectic composition having a low melting temperature. This liquid phase is used to promote the densification at low temperature. The effect of various additions (nature and quantity) are also investigated to optimise the resulting thermal and physical properties. In terms of sintering behaviour, the results are unambiguous, leading to a drastic decrease of the densification temperature with all the non-boric additions (<1000°C). The dc/ac measurements carried out on the materials sintered at low temperature (900 and 1000°C) and either in air or in reductive atmosphere follow the same trend when using non-boric additions, with high permittivities (>25), low dielectric losses (<10x10^(-4)), low temperature coefficients of the permittivity (<100 ppm/K) and high insulating resistivities (up to 10^15 ohm.cm); the high frequency measurements lead to similar conclusions revealing high QF products (up to 40 THz) using non-boric additions. The effect of the sintering temperature, the sintering atmosphere, the flux composition and its amount on these properties are also discussed.
M. Pollet, S. Marinel, F. Roulland, Journal of the European Ceramic Society 25 (2005) 2773-2777

L0037 – Low temperature sintering of the binary complex perovskite oxides xBa(Zn1/3Ta2/3)O3 + (1-x)Ba(Mg1/3Ta2/3)O3

The interest for the complex perovskites oxides is known since several years. Ba(Zn1/3Ta2/3)O3 (BZT) and Ba(Mg1/3Ta2/3)O3 (BMT) have been broadly studied due to their attractive dielectric properties suitable for applications such as multilayer ceramic capacitors or hyperfrequency resonators. They hence exhibit at 1MHz very low dielectric losses combined with a high relative dielectric constant which is stable with the temperature. Unfortunately, these materials needs a too high temperature to reach a satisfying density. The BMT sintering temperature is indeed higher than 1500°C, which is too high to envisage a co-sintering with copper (Tf = 1083°C) or nickel (Tf = 1450°C). To lower the sintering temperature, a glass phase addition is performed on the complex formulations xBa(Zn1/3Ta2/3)O3 + (1-x)Ba(Mg1/3Ta2/3)O3 (with x = 0, 1/3, 1/2, 2/3 and 1). These mixtures are envisaged to explore their dielectric properties. The sintering temperature lowering reached is higher than 400°C when 10 molar% of borate oxide is added to the mixtures and their dielectric properties are very attractive (? = 25 and ?? =-59 ppm/°C for x = 1/3) for the fabrication of base metal electrodes multi layer ceramic capacitors (BME-MLCC).
F. Roulland, G. Allainmat, M. Pollet, S. Marinel, Journal of the European Ceramic Society 25 (2005) 2763-2768

L0036 – Dielectric properties of Ba(Mg,Zn)1/3Nb2/3O3 and effect of B2O3 and LiF addition

The dielectric and microwave properties of (x)BaZn1/3Nb2/3O3-(1-x)BaMg1/3Nb2/3O3 (BMZN) mixture were investigated. The complex perovskite-type ceramics Ba(Zn1/3Nb2/3)O3 (BZN) and Ba(Mg1/3Nb2/3)O3 (BMN) have a high dielectric constant (?r = 39 and 33, respectively), but while BZN has a relative low firing temperature (?1350°C), BMN has a too high sintering temperature (>1500°C) to make it attractive in some technological applications. Mixing these two dielectric ceramics in different proportions and adding some sintering agents (like glassy B2O3 and LiF) the sintering temperature can be decreased, and XRD patterns indicates the formation of a solid solution for all x values investigated. The dielectric properties are preserved or even improved for some specific combinations. For BMZN (x = 1/4), without any dopants, the Qf factor is 76.7 THz for f = 7.6 GHz and the temperature coefficient of the resonant frequency tf is -4 ppm/°C, which is the best value for BMZN. These values make BMZN compounds suitable for microwave resonator applications. We highlight in this paper that BMZN materials can be successfully sintered at low temperature (i.e. 940°C), opening opportunities to manufacture base metal electrodes multilayer ceramic capacitors (BME-MLCC).
A. Veres, S. Marinel, F. Roulland, Journal of the European Ceramic Society 25 (2005) 2759-2762

L0035 – Dielectric and electromechanical characterisation of fine-grain BaTi0.95Sn0.05O3 ceramics sintered from glycolate-precursor powder

Nanocrystalline BaTi0.95Sn0.05O3 (BTS-5) powder was synthesised from glycolate-precursors, and used to sinter fine-grain BTS-5 ceramics. We compare sintering behaviour, microstructure as well as dielectric and electromechanical properties of the advanced ceramics with ceramics sintered from classical mixed oxide powder.
L. Geske, V. Lorenz, T. Müller, L. Jäger, H. Beige, H-P. Abicht, V. Mueller, Journal of the European Ceramic Society 25 (2005) 2537-2542

L0034 – Electrical, thermal and catalytic properties of CeO2-Sm0.5Ti0.5O1.75 ceramics

The electrical conductivity of the ceramic composite, (CeO2)(1-x)(Sm0.5Ti0.5O1.75)x, where 0
S. Koutcheiko, Y. Yoo, I. Davidson, Ceramics International 31 (2005) 965-971

L0033 – Sintering, microstructure and grain growth of Fe-doped Ce0.9Gd0.1O2 d ceramics derived from oxalate coprecipitation

The precursor powder of Ce0.9Gd0.1O2 d ceramics was prepared by oxalate coprecipitation. 0.1-3 at% (atomic percent) Fe2O3 was added into the powder via the conventional mixed-oxide method. The effects of doping level, and sintering temperature and time on the densification, microstructure and grain growth of Ce0.9Gd0.1O2 d ceramics were investigated by means of dilatometry measurement, density testing and scanning electronic microscopy (SEM) observation. In the Fe content range used, the sintering temperature decreased consistently with increasing Fe level (from 1310°C at 0.1 at% Fe to 1104°C at 3 at% Fe). Small additions of Fe2O3 promoted the densification rate significantly. The densification rate reached a maximum at 1 at% Fe, then decreased with further increase in Fe content. For 0.5 at% Fe-doped Ce0.9Gd0.1O2 d ceramic, over 97% relative density was complete during heating ramp fromroomtem perature to 1350°C at a heating rate of 10°C/min, as compared to only 86% for the undoped ceramic. The Fe doping level was also found to have a remarkable influence on the grain growth behavior, which depended on sintering temperature. At lower temperatures (e.g., 1250°C), a pinning effect on grain growth was found above 1 at% Fe additions. However, such a pinning effect became less important with increasing temperature. A slight increase in grain size was actually observed in the Fe-doped ceramic sintered at 1500°C as the Fe content increased from0.1 to 3 at%. The analysis based on the grain growth kinetics indicated that the undoped Ce0.9Gd0.1O2 d ceramic followed a parabolic law for grain growth, while the 0.5 at% Fe-doped ceramic had a grain growth exponent of 4.
T.S. Zhang, J. Ma, Y.J. Leng, Z.M. He, Journal of Crystal Growth 274 (2005) 603-611

L0032 – Thermal analysis of the cyclic reduction and oxidation behaviour of SOFC anodes

The reduction and oxidation (redox) kinetics of a Ni/YSZ cermet were studied at temperatures between 400 and 850°C by thermogravimetric analysis (TGA) and reduction and oxidation activation energies were determined. In addition, the volume change after redox cycling was examined by thermomechanical analysis (TMA). Samples with fine microstructure similar to a typical SOFC anode functional layer (AFL) and samples with coarse microstructure similar to a typical anode substrate were characterized. Coarse structured samples experienced no volume change or cracking upon redox cycling. Fine structured anode samples did not change in volume after reduction, but expanded between 0.9% and 2.5% after oxidation. The samples were significantly cracked after oxidation. The amount of expansion and cracking was reduced by lowering the Ni content of the anode and by reducing the oxidation temperature. The reduction of the NiO/YSZ samples followed linear kinetics with an activation energy of 78 kJ/mol. Ni/YSZ oxidation followed parabolic kinetics at temperatures lower than 700°C. A divergence from parabolic kinetics was seen at higher temperatures (700-850°C). This divergence has been seen in many other kinetic studies and is usually attributed to short-circuit diffusion mechanisms. An activation energy of 87 kJ/mol was calculated for oxidation.
D. Waldbillig, A. Wood, D. G. Ivey, Solid State Ionics 176 (2005) 847-859

L0031 – A study of Pr0.7Sr0.3Fe(1-x)NixO(3-d) as a cathode material for SOFCs with intermediate operating temperature

Pr0.7Sr0.3Fe(1-x)NixO(3-d) (PSFN; x=0.2-0.5) compounds were synthesized and characterized by powder X-ray diffraction (XRD), thermal expansion coefficient (TEC) measurements, electrical conductivity and electrochemical impedance spectroscopy on coneshaped electrodes on a Ce0.9Gd0.1O1.95 (CGO10) electrolyte. The main phase of the powders belongs to the orthorhombic crystal system. The conductivities are fairly high, e.g., around 450 S.cm-1 at 600°C for the x=0.3 compound. The TEC of the compounds is close to the values of ceria-based electrolytes. PSFN showed hysteresis in the temperature dependence of the conductivity, TEC and area-specific polarization resistance Rpol. It is considered that the hysteresis was caused by relatively slow adjustment of the oxygen stoichiometry. The electrochemical performance Rpol 1 of the PSFN compounds is similar to that of La0.6Sr0.4Fe0.8Co0.2O(3-d).
S-I. Hashimoto, K. Kammer, P.H. Larsen, F.W. Poulsen, M. Mogensen, Solid State Ionics 176 (2005) 1013-1020

L0030 – Ionic conductivities and phase transitions of lanthanide rare-earth substituted La2Mo2O9

The ion conductivities and phase transitions of lanthanum molybdate (La2Mo2O9) substituted with lanthanide rare-earths are investigated using impedance spectroscopy, dilatometry, and X-ray powder diffraction. Among the substituted La2Mo2O9 of 10 mol% Ce, Nd, Sm, Gd, Dy, Er, Yb, the specimens containing Er, and Dy exhibit depressed alpha-beta phase transformation and high conductivities. Their 700°C conductivities are approximately five to seven times that of La2Mo2O9, around 0.26 S cm-1, comparable with those of (LaSr)(GaMg)O3 and Gd-substituted CeO2. Among the three compositions of 10 mol% Gd, Dy, Er showing depressed phase transition, Er- and Dy-substituted La2Mo2O9 possess relatively low thermal expansion coefficient 11 x 10^(-6) K-1, compared with that of the Gd-substituted La2Mo2O9, 18 x 10^(-6) K-1, which is near that of La2Mo2O9. Hence, Dy and Er are valuable dopants in improving the La2Mo2O9 properties. Across the lanthanide series, 10 mol%-substituted La2Mo2O9 demonstrates systematic variations in the conductivity-temperature relation. Hysteresis phenomena in both of conductivity and thermal expansion are also observed in those compositions which display phase transition.
D-S. Tsai, M-J. Hsieh, J-C. Tseng, H-Y. Lee, Journal of the European Ceramic Society 25 (2005) 481-487

L0029 – Sintering shrinkage of WC-Co materials with bimodal grain size distributions

Sintering shrinkage and densification rate were investigated for WC-Co materials with different grain size distributions. Unimodal distributions were compared to bimodal mixtures with size ratio close to four. A bimodal carbide mixture with 25% fine particles showed similar shrinkage behaviour to a material with unimodal distribution around the same mean value. With 50% fine particles the initial shrinkage was slightly faster than a unimodal material with the same mean size, while the late shrinkage was considerably slower. The effects of particle size distribution on particle packing and sintering are discussed, and the effect on viscosity modelled.
A. Petersson, J. Agren, Acta Materialia 53 (2005) 1665-1671

L0028 – Synthesis and characterisation of the double perovskite Ba2(Zn0.5Ti0.5X)O6 (X = Nb, Ta) ceramics

Ba2(Zn0.5Ti0.5X)O6 compounds from the general ABO3 perovskite family were synthesized by the classical solid-state route for X = Nb and Ta with various A/B ratios (1.005, 1 and 0.995). After the calcination step at 1100°C, both compounds (X = Nb and Ta) contain mainly the cubic disordered 'Ba2(Zn0.5Ti0.5X)O6' phase but traces of BaTiO3 and secondary phases are often detectable. Nevertheless, after the sintering stage at higher temperature (from 1300 to 1500°C) and for all A/B ratios investigated, Ti enters into the cubic perovskite structure, resulting in the formation of a unique 'Ba2(Zn0.5Ti0.5X)O6' phase. Attractive dielectric properties have been measured on the tantalum-based compound for A/B = 0.995 (Q 2000 at 7.4 GHz and e = 39.6) as well as on the niobium-based phase for A/B = 1.005 (Q 2200 at 6.1 GHz and e = 54.8). All these characteristics were confirmed at 1 MHz and a linear dependence of the permittivity versus temperature from 60 to 180°C has also been evidenced for both formulations. Sinterability, dielectric properties and microstructure of such compounds are discussed with respect to the stoichiometry.
S. Marinel, F. Roulland, Materials Research Bulletin 40 (2005) 962-969

L0027 – Influence of titanium nitride addition on the microstructure and mechanical properties of TiC-based cermets

In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high temperature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from lowcost raw materials. Cermets obtained by sintering powders of TiC and Mo2C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as Young s modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Mate´riaux a` base de carbures et nitrures, pour coupe et usure, obtenus a` partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders.
J. Russias, S. Cardinal, Y. Aguni, G. Fantozzi, K. Bienvenu, J. Fontaine, International Journal of Refractory Metals & Hard Materials 23 (2005) 358-362

L0026 – High temperature properties of SiC and diamond CVD-monofilaments

The chemical, structural and thermomechanical properties of SiC and diamond CVD-monofilaments have been investigated. Electron and Raman microprobe analyses showed graded radial atomic and phase distributions in the SiC filaments. Thermomechanical investigations (tensile/bending elastic modulus/creep tests) were carried out on single filaments and these properties were correlated with the physicochemical features. The thermal behaviour of the CVD-SiC filaments is strongly related to the nature and the amounts of intergranular secondary phases (free carbon or silicon). The strong covalent bonds and the microcrystalline state of the CVD-diamond filaments give rise to an outstanding thermal behaviour.
G. Chollon, R. Naslaina, C. Prentice, R. Shatwell, P. May, Journal of the European Ceramic Society 25 (2005) 1929-1942

L0024 – Synthesis of CaAl2O4 from powders: Particle size effect

Starting from high energetic attrition milled mixtures of either alpha-Al2O3 or amorphous (Al(OH)3) with CaCO3 the binary compound calcium monoaluminate (CaAl2O4) was synthesized with high purity. The processes were carried out on samples with the nominal CaAl2O4 stoichiometry. High energetic attrition milling of the reactants does not eliminate the starting carbonate, both batches showed a high degree of homogeneity and they behaved similarly on heating, forming CaAl2O4 at temperatures lower than 1300°C. These temperatures are lower than that required for the traditional solid state reaction process. The CaAl2O4 synthesis path implies the formation of cryptocrystalline and crystalline Al2O3, CaO, Ca12Al14O33 and CaAl4O7 as transitory phases. The nucleation and growth of CaAl2O4 took place at 1300°C and shows a porous structure and small grain size (-1.5 m).
J.M. Rivas Mercury, A.H. De Aza, P. Pena, Journal of the European Ceramic Society 25 (2005) 3269-3279

L0023 – Colloidal processing and sintering of nanosized transition aluminas

The dispersion of nanosized gamma aluminas with high specific surfaces areas (100 m2/g) and primary particle sizes around 20 nm, using polyacrylic acid, has been investigated. The effect of pH and polymer concentration showed that the highest density green bodies were produced using high polymer concentrations (6 wt.%) and pH of 6. Interparticle potential calculations have been made and help explain the underlying dispersion mechanism at least on a qualitative level. The dispersions were then used to slip cast green bodies followed by drying and sintering. The types of gamma alumina powder have been investigated, the pure gamma alumina, doped with MgO and also with the addition of alpha alumina seeds. The high degree of agglomeration of the gamma alumina powders led to very low densities (60%) even the alpha seeded alumina reached only 85% theoretical density. Attrition milling with zirconia media improves both green density and sintered densities significantly with all powders showing sintered densities >97%. Microstructural analysis on polished and etched surfaces show, however, that the grain sizes are well above 1 Am over 50 times greater than the initial gamma alumina primary particles. A two-step sintering cycle was investigated with the Mg doped powder and average grain sizes around 580 nm were achieved.
P. Bowen, C. Carry, D. Luxembourg, H. Hofmann, Powder Technology 157 (2005) 100 - 107

L0021 – Mullite compacts obtained by colloidal filtration of alumina powders dispersed in colloidal silica suspensions

This work deals with the manufacture of mullite-matrix composites by a colloidal filtration route. Avariation of the transient viscous sintering process is studied in which submicrometer sized alumina particles are dispersed in a nanosize colloidal silica
O. Burgos-Montes, M.I. Nieto, R. Moreno, Ceramics International 33 (2007) 327-332

L0020 – Synthesis and sintering of porous La0.8 Sr0.2 MnO3 powder

In this research, La0.8Sr0.2MnO3 precursors were synthesized from metallic nitrates by sol-gel method using polyacrylic acid (PAA) as the chelating to prepare pure and porous powders for the cathode application in solid oxide fuel cell (SOFC). The LSM powders after dried and sintered at suitable temperatures were characterized by X-ray diffractometry (XRD), scanning, and transmission electron microscopes (SEM and TEM). The LSM powder with nano-crystalline synthesized by adding (P)AA/LSM = 2 was obtained after calcined at 500°C for 2h, and still kept porous character up to 1000°C.
H-R. Hsu, S-C. Wang, W-C.J. Wei, Bulletin of the College of Engineering, N.T.U. 89 (2003) 83-90

L0019 – Processing and characterization of La2O3/Al2O3/B2O3 based glass-ceramics for LTCC application

A lead-free, non-alkali and low-sintering temperature, La2O3-Al2O3-B2O3 (LAB) glass with Al2O3 filler had been investigated for LTCC application. The glass melting, processing window of tape casting, and sintering of the LAB glass-ceramic systems the wetting behaviors of the LAB glass on alumina plate, and the crystallization kinetics in the LAB/Al2O3 glass-ceramics were also studied. Moreover, systematic studies of thermal characteristics, phase transformation and microstructures during different heat-treatments were investigated by DTA, XRD, TMA, SEM/EDS, TEM, and AEM. The densification and crystallization temperatures of LAB glass performed between 800°C-850°C. Additionally, the sintering and dielectric properties of layer LAB/Al2O3 glass-ceramics with Ag electrode were also measured. The densification kinetics and possible defects during the cofiring will be reported.
C-L.B. Chen, W-C.J. Wei and A. Roosen

L0017 – Low-temperature synthesis and sintering of y-Y2Si2O7

In this article, a novel pressureless solid-liquid reaction method is presented for preparation of yttrium disilicate ( -Y2Si2O7). Single-phase -Y2Si2O7 powder was synthesized by calcination of SiO2 and Y2O3 powders with the addition of LiYO2 at 1400°Cfor 4 h. The addition of LiYO2 significantly decreased the synthesis temperature, shortened the calcination time, and enhanced the stability of -Y2Si2O7. The sintering of these powders in air and O2 was studied by means of thermal mechanical analyzer. It is shown that the -Y2Si2O7 sintered in oxygen had a faster densification rate and a higher density than that sintered in air. Furthermore, single-phase -Y2Si2O7 with a density of 4.0 g/cm3 (99% of the theoretical density) was obtained by pressureless sintering at 1400°Cfor 2 h in oxygen. Microstructures of the sintered samples are studied by scanning electron microscope.
Z. Sun, Y. Zhou and M. Li, Journal of Materials Research 21 (2006) 1443-1450

L0012 – Sintering of a transition alumina : Effects of phase transformation, powder characteristics and thermal cycle.

The effects of several parameters on the pressureless sintering of a commercially available transition alumina has been investigated. The capacity of the particles to re-arrange during the phase transformation into the alpha-alumina phase has been shown to be a key feature in the densification mechanism. The degree to which the particle re-arrangement can lead to an enhanced densification over and above the change in density due to the phase transformation from y to alpha phase depends on several parameters: compact density, heating rate and the amount of alpha-alumina present in the as-supplied raw powder. The parameters influencing the degree of particle re-arrangement and what directions to take to improve on the above densities and grain sizes are discussed.
C. Legros, C. Carry, P. Bowen and H. Hofmann, Journal of European Ceramic Society 19 (1999) 1967-1978

L0011 – Pre-eutectic densification of calcium carbonate doped with lithium carbonate.

Pressureless sintering of CaCO3 was carried out, with Li2CO3 (from 0.5 to 8 wt%) as an additive, under different pressures of CO2. Densification occurs between 600 and 700°C. Sintering above the eutectic temperature (T>662°C) leads to the decomposition of calcium carbonate and the materials become expanded. At 620° under 1 kPa of CO2, a relative density of 96% is reached. Li2CO3 enhances the densification process and grain growth of calcium carbonate. CO2 pressure slows down densification and grain growth kinetics. These results are explained by the influence of carbonate and calcium ion vacancies on the sintering mechanisms.
F. Tétard, D. Bernache-Assollant and E. Champion, Journal of Thermal Analysis and Calorimetry 56 (1999) 1461-1473

L0010 – Dimensional stability and defect chemistry of doped lanthanum chromites.

Acceptor doped lanthanum chromites are potential interconnect materials to be used in high temperature Solid Oxide Fuel Cells (SOFC). However, instability of these materials when exposed to low oxygen partial pressure causes a volume expansion that can be detrimental to the SOFC performance. The stability of La0.8Sr0.2Cr0.97V0.03O3 is determined as function ofpO2 and temperature by isothermal thermogravimetry and dilatometry. The experimental data are analysed using a simple model for the defect chemistry. The relation between expansion behaviour and change in defect chemistry is discussed using a simple structural model.
P.H. Larsen, P.V. Hendriksen and M. Mogensen, Journal of Thermal Analysis and Calorimetry 49 (1997) 1263-1275

L0009 – Microstructure and piezoelectric properties of slip cast barium titanate ceramics

J. Lemaitre, C. Herard and D. Vogel, Third Euro-Ceramics 2 (1993) 59-64

L0008 – Effect of Yttrium doping on sintering of fine grained alumina

E. Sato and C. Carry, Third Euro-Ceramics 1 (1993) 691-696

L0007 – BaTiO3 ceramics. Sintering and residual carbon content.

C. Le Calvé-Proust, E. Husson, G. Blondiaux, J.P. Coutures, Third Euro-Ceramics 1 (1993) 799-804

L0006 – Grain growth and swelling of hot pressed BaTiO3 during annealing treatments

M. Demartin, C. Herard, J. Lemaitre and C. Carry, Third Euro-Ceramics 1 (1993) 775-780

L0005 – Sintering, grain growth and de-sintering processes in un-doped BaTiO3

M. Demartin, G. Pethybridge and C.Carry, Third Euro-Ceramics 1 (1993) 787-792

L0004 – Preparation of dense tetragonal zirconia ceramics from ZrO2 micropowders

A. Smith, B. Cales and J.F. Baumard, Journal de Physique, Colloque C1, supplément au n°2, Tome 47 (1986) 237-241

L0003 – The formation and characterization of a ceramic-ceramic interface between stabilized zirconia and lanthanum chromite

D. Smith, M. Sayer and P. Odier, Journal de physique, Colloque C1, supplément au n°2, Tome 47 (1986) 153-157

L0002 – Phase equilibrium and martensitic transformation in lanthana doped zirconia

The system ZrO2-La2O3 has been studied in the 0 to 15 mol% La2O3 range using X-ray diffraction and thermal analysis. Two kinds of diagrams were elaborated: First is a phase equilibrium diagram where the eutectoid decomposition of ZrO2,ss(T) => ZrO2,ss(M) + Pyss occurs at 1100°C and 0.75 mol% La2O3 (Py is the pyrochlore compound Zr2La2O7). The maximum solubility of La2O3 in ZrO2,ss(M) is 0.5 mol% at room temperature. Second, a nonequilibrium diagram is determined showing the correlations between grain size, La2O3 content, and the martensitic transformation temperature start (Ms).
B. Bastide, P. Odier and J.P. Coutures, Journal of the American Ceramic Society 71 (1988) 449-453

L0001 – Sintering behaviour of Y(u)Ba(v)Cu(w)O(7-d) (u ? 1; v ? 2; w ? 3)

B. Dubois, A. Douy, M. Gervais, F. Cabannes et P. Odier, International Conference on High Temperature Superconductors and Materials and Mechanisms of Superconductivity, Interlaken (Suisse) (1988)

G0013 – Application des mesures magnétiques à la métallurgie

E. Alff and Cl. Bronner, Conférence au Cercle d'Etudes des Métaux (1973) 1-34

G0012 – Recyling cemented carbides without pollution sorting chargeing material for zinc process

K. Hirose, I. Aoki, Int. Conf. Process. Mater. Prop., 1st (1993) 845-848

E0339 – Nonmagnetic Fe-site doping of BiFeO3 multiferroic ceramics

In this paper, we show that a pure single phase by doping Fe-site of BiFeO3 (BFO) using tetravalent Zr4+ ions can be achieved by introducing cation (Bi3+) vacancies. The structural analysis reveals that the ferroelectric nature of BFO should be weakly affected by 10% of Zr4+ doping as the c/a ratio and the Curie temperature TC remain roughly unchanged compared to that of pure BFO. In contrast, the magnetic properties are affected as a weak ferromagnetism and a change of Néel temperature TN are observed. Beyond the double-exchange interactions arising from the creation of Fe2+, we propose another simple model inducing a local ferromagnetic coupling rather than an antiferromagnetic which considers the replacement of the magnetically active Fe3+, time to time, by a nonactive Zr4+.
Jie Wei, Raphael Haumont, Romain Jarrier, Patrik Berhtet, Brahim Dkhil, Appied Physics Letters 96, 102509 2010

E0314 – Effect of inclusions in Nd-doped NaY(WO4)2 single crystals

Single crystals of Nd-doped NaY(WO4)2 (Nd:NYW) were grown using the Czochralski technique. Crystal cracking and the presence of inclusions were found to be the main problems associated with the growth of crystals. Thermal expansion measurements were carried out on as-grown crystal samples that were cut perpendicular to the growth direction and had different amounts of inclusions. Differential thermal analysis was also carried out on these same samples. The amount of inclusions present in the Nd:NYW crystal was found to affect the thermal characteristics of the crystal. The role of impurity phases in the Nd:NYW lattice during growth is discussed on the basis of obtained results. The inclusions present in the crystal are found to produce excessive strain in the lattice, which ultimately results in cracking of the crystal.
R G Salunke, S G Singh, A K Singh, D G Desai, M Tyagi, S Wgosavi, S C Gadkari, Phys. Scr. 84 (2011) 045601

E0305 – Size ratio induced yttrium aluminum garnet formation characteristics in nano-scaled Y2O3–Al2O3 powder systems via fast firing processes

The formation characteristics of YAG phase synthesized by fast-firing Y2O3 and Al2O3 powder mixtures were examined. Y2O3 powders of 100, 350, and 500 nm in D50 were mixed with ?-Al2O3 powder of (D50) 200 nm to obtain starting powders denoted as S0.5, S1.75, and S2.5, respectively. In these mixtures, the two oxides contacted wholly with each other but varied in number of contact points and diffusion length. This study aimed to eliminate the YAM and YAP phases, which normally occur during YAG formation. Examinations were conducted using pressed compacts (bulk density of 0.91 g cm?3) prepared with the three mixtures. After pre-heating at 700 °C for 30 s, the compacts were plunged at temperatures of 1050–1450 °C for 5–60 s and then quenched to room temperature. In the S0.5 system, one-step YAG formation occurred by an interface-controlled mechanism, and intermediates were apparently suppressed. However, YAG formation was divided into two stages in the S1.75 and S2.5 systems. Two stages were defined by the heating duration prior to and after 20 s. The interface-controlled mechanism was dominant in the initial stage, and then the diffusion-controlled mechanism was dominant in the second stage, in which YAG formed sluggishly and substantial amounts of YAM and YAP persisted. However, both stages followed the conversion sequence of YAM to YAP and then to YAG. Accordingly, two YAG formation routes derived from reacted Y2O3 of different sizes are proposed. Finally, a pure YAG phase could be obtained by calcining the S0.5 system at 1200 °C for 60 s.
Chen-Tsung Hung, Chai-Yuan Lai, Fu-Su Yen, Materials Chemistry and Physics 129 (2011) 534– 539

E0289 – Phase relations in the ZrO2–Nd2O3–Y2O3–Al2O3 system: Experimental study and thermodynamic modeling

The Nd2O3–Al2O3 and ZrO2–Nd2O3–Al2O3 systems were simultaneously re-assessed to reproduce experimental data from present study and literature. Phase relations in the Nd2O3–Y2O3–Al2O3 system were investigated by XRD, electron microscopy and DTA for the first time. Invariant reaction in solid phases B + YAM = NdAlO3 + C was determined to occur at 1863 K. The eutectic reaction liquid = YAG + NdAlO3 + Al2O3 was determined to occur at 2042 K and composition Al2O3–10 mol.% Nd2O3–13 mol.% Y2O3. The obtained data were used to assess thermodynamic parameters of this system. Isothermal sections were calculated in the range 1523–1923 K. Liquidus surface of the Nd2O3–Y2O3–Al2O3 system was calculated. The derived databases were combined with already available descriptions of the ZrO2–Nd2O3–Y2O3 and ZrO2–Y2O3–Al2O3 systems into four-oxide database.
O. Fabrichnaya, G. Savinykh, G. Schreiber, H.J. Seifert, Journal of the European Ceramic Society 32 (2012) 3171–3185

E0279 – Thermal analysis and SANS characterisation of hybrid materials for biomedical applications

Silicate hybrid materials were prepared by the sol–gel process with the addition of x mass% of zirconium propoxide (x = 0 and 1). The thermal behaviour as well as the influence of Zr addition was studied by thermal gravimetric analysis and differential thermal analysis. The microstructure evolution with temperature was investigated by X-ray diffraction and small-angle neutron scattering. It was found that the beginning of polymer degradation occurs at a higher temperature in the material prepared with addition of Zr than in the one prepared without. At the nanometric scale, the materials prepared without Zr show smooth interfaces, whereas those with Zr present a mass fractal structure. This structure is also observed in the material without Zr after thermal treatment at 200 °C. The results showed that bioactivity is favoured by mass fractal structures in comparison with one consisting of smooth surfaces.
J. J. H. Lancastre, F. M. A. Margaça, L. M. Ferreira, A. N. Falcao, I. M. Miranda Salvado, M. S. M. S. Nabiça, M. H. V. Fernandes, L. Almasy, J Therm Anal Calorim (2012) 109, 413–418

E0272 – Synthesis and Sintering of Bi2Ti4O11

The conditions of Bi2Ti4O11 formation are studied. It is shown that the process is diffusion-controlled and depends significantly on the heating rate. The optimal conditions for producing Bi 2Ti4O11 ceramics are determined. Cold pressing of Bi2Ti4O11 ceramic powder at high pressures is shown to influence the unit-cell parameters and volume, positional parameters of Bi and Ti, and bond distances in the ferroelectric ceramics produced by subsequent sintering. The ferroelectric transition temperature decreases steadily with increasing densification pressure.
A. I. Akimov, G. K. Savchuk, Inorganic Materials, Vol. 40, No. 7, 2004, pp. 716–720

E0266 – Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics

Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al2O3, BaTiO3, CaTiO3, TiO2, ZrO2, MgO and SiO2 were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al2O3, BaTiO3, CaTiO3 and MgO samples demonstrated crystalline phases, CaAl2Si2O8, BaAl2Si2O8, CaTiSiO5 and CaMgSi2O6, respectively, as a result of firing at 850 °C. For the sample containing CaTiO3 filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO2. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO2. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.
Ik Jin Choi, Yong Soo Cho, J Electroceram (2009) 23, 185–190

E0264 – Possible stibnite transformation at the friction surface of the semi-metallic friction composites designed for car brake linings

After a friction process several changes in phase composition of friction composites are often registered. High temperature, accompanied by high pressure induced during braking can cause initiation of chemical reactions which do not run at room or elevated temperatures under the atmospheric pressure. Most of the studies in the field of tribochemistry at friction surfaces of automotive semi-metallic brake linings deal with phenolic resin degradation and corrosion of metallic components. The paper addresses the formation of elemental antimony as well as the alloying process of iron with antimony observed on the surface of laboratory prepared semi-metallic friction composites containing stibnite. The role of alumina abrasives in the process of stibnite transformation is also discussed and mechanism of stibnite transformation was outlined.
V. Matejkaa, Y. Lub, P. Matejkovác, B. Smetanad, J. Kukutschováa, M. Vaculíka, V. Tomáseka, S. Zlád, Y. Fan, Applied Surface Science 258 (2011) 1862– 1868

E0262 – Application of a modified Pechini method for the synthesis of Ln2MGe4O12 (Ln 5 Y, Eu; M 5 Ca, Zn, Mn) optical hosts

A modified Pechini method followed by conventional and microwave heating was used to synthesise the new promising Ln2MGe4O12 (Ln = Y, Eu; M = Ca, Zn, Mn) optical hosts. Comparison between solid-state and Pechini synthesis methods showed that the latter reduces the temperature required for cyclo-tetragermanate formation. The highest yield of cyclo-tetragermanates for both methods is observed at 1,000–1,100 °C, with significantly shorter time of annealing in the case of the Pechini synthesis. Compositional, structural and morphological characterisations of the samples obtained by both routes were carried out using X-Ray powder diffraction, thermogravimetry, electron spin resonance spectroscopy, energy-dispersive X-Ray spectroscopy and scanning electron microscopy.
Marina A. Melkozerova, Nadezda V. Tarakina, Lidia G. Maksimova, Alexander P. Tyutyunnik, Ludmila L. Surat, Ivan I. Leonidov, Vladimir G. Zubkov, Elena V. Zabolotskaya, Rina F. Samigullina, J Sol-Gel Sci Technol (2011) 59, 338–344

E0252 – Microstructure effect on the properties of a commercial low-fusing dental porcelain

The aim of this study was to investigate the effect of firing cycle on a dental porcelain microstructure in order to correlate microstructure changes with mechanical and thermal properties. A commercial low-fusing dental porcelain powder (Omega 900, Vita) was investigated for this purpose. The powder was treated at different temperatures in the range 750±1000° C. The fired samples were characterized in terms of their morphology and microstructure, and their mechanical and thermal properties were evaluated. The results showed that firing temperature affects porcelain microstructure influencing significantly in this way both the mechanical properties and the thermal expansion coefficient of the fired objects. Firing at 800° C led to a homogeneous structure. After treatment at this temperature, the leucite crystals exhibit their maximum concentration and they are well dispersed into the glassy phase. As a consequence the optimum mechanical strength and the maximum thermal expansion coefficient are observed in these samples.
Athena Tsetsekou, Triantafillos Papadopoulos, Othon Adamopoulos, Journal of Materials Science: Materials in Medicine, 13 (2002) 407-416

E0250 – Characterization of nanostructured magnetite thin films produced by sol–gel processing

Nanocrystalline films of magnetite have been prepared by a novel sol–gel route in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. Annealing temperature was selected between 291 and 350 °C by DTA analysis in order to obtain magnetite films. In-plane grazing angle XRD and TEM studies showed that magnetite phase was present upon annealing the films at 300 °C. The films had crack free surfaces and their thicknesses varied between *10 and 200 nm. UV–Vis spectrum results showed that transmittance of the films increases with decreasing annealing temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900–1,100 nm. Vibrating sample magnetometer measurements indicated that magnetite thin films showed ferromagnetic behavior and the saturation magnetization value was found as ~35 emu/cm3.
Ali Erdem Eken, Macit Ozenbas, J Sol-Gel Sci Technol (2009) 50, 321–327

E0247 – Mechanical Activation of Spinel and Pyrochlore Phases in ZnO Based Varistors

Mixtures of ZnO, Sb2O3 and Bi2O3 powders corresponding to the stoichiometric compositions of Zn7Sb2O12 (spinel) and Zn2Bi3Sb3O14 (pyrochlore) were milled in a shaker mill (SPEX) up to 180 minutes. The influence of the mechanical activation of the powders, as a result of the milling, was determined by Differential Thermal Analysis, Thermogravimetric Analysis and X-ray Diffraction. Additionally, in order to compare to commercial recipes the mixture ZnO + 2.7 wt% Sb2O3 + 4.5 wt% Bi2O3 was milled in a shaker mill up to 180 minutes. Varistor devices were fabricated with both milled and unmilled mixtures. The devices were characterized by I-V studies, Scanning Electron Microscopy and X-ray Diffraction. Mechanical activation on the system ZnO-Bi2O3-Sb2O3 produced a chemical reaction and amorphization in the powder mixture. The weight loss due to volatilization of Bi2O3 and Sb2O3 that occurrs in both ZnO-Sb2O3 and ZnO-Sb2O3-Bi2O3 systems at temperatures below 1200°C is reduced by milling the powder mixtures.
C. Gomez-Yanez, J. Velazquez-Morales, E.G. Palacios, Journal of Electroceramics, 13, 745–750, 2004

E0241 – Structural, dielectric and multiferroic properties of Er and La substituted BiFeO3 ceramics

Erbium (Er) and lanthanum (La) substituted BiFeO3 (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi(0.9–x) La0.1Erx FeO3 (x = 0.05, 0.07 and 0.1) (BLEFOx = 0.05, 0.07,0.1) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFOx = 0.1.
Pragya Pandit, S Satapathy, Poorva Sharma, P K Gupta, S M Yusuf, V G Sathe, Bull. Mater. Sci., Vol. 34, No. 4, July 2011, pp. 899–905

E0225 – Titanium—hydroxyapatite porous structures for endosseous applications

Materials for uncemented endosseous implants have to assure an as short as possible osseointegration time. Thus, a material with both surface bioactivity and a porous outer structure can become a preferred choice for this type of applications. This paper presents a class of titanium-base PM composites, reinforced with particulate hydroxyapatite. Raw materials were titanium powder, obtained through hydriding—milling—dehydriding, with the grain size of 63–100?m, and sol-gel hydroxyapatite (HA) powder, produced by the reaction between Ca(NO3)2·4H2O and (NH4)2HPO4. Blends with 5 to 50% HA were prepared and pressed in a rigid die, producing single composition or gradual composition samples. The applied pressure was of 400, 500 or 600 MPa. Sintering was performed in vacuum, at 1160 ?C. All samples, although well sintered, displayed swelling during sintering, due to diffusion into the matrix. The increase in volume is more severe for higher amounts of HA in the green compacts and for higher applied compaction pressure. Compacts with a gradual increase of the HA content are recommended from the functional and mechanical point of view, but the increase should be slow, not to produce interlayer cracks. The outer surface shows interconnected pores, suitable for the ingrowth of vital new bone.
C. Popa, V. Simon, I . Vida-Simiti, G. Batin, V. Candea, S. Simon, Journal of Materials Science: Materials in Medicine 16 (2005) 1165-1171

E0224 – Thermodynamic Evaluation of the C-Co-W-Hf-Zr System for Cemented Carbides Applications

Cemented carbides consist of hard carbide particles of hexagonal WC and often also of cubic carbides cemented together in a binder consisting of mainly cobalt (Co). A thermodynamic evaluation of the cubic carbide formers hafnium (Hf) and zirconium (Zr) in cemented carbides has been done. Both thermodynamic evaluations of lower-order systems and experimental investigations have been performed. The new experimental information was necessary for a satisfactory thermodynamic description because there is a lack of earlier experiments of this alloy system. The assessment work with the C-Co-W-Hf-Zr system has resulted in a satisfactory description of the thermodynamic properties compared with the experimental values. This work has been done by combining a new assessment of the CoHf and CoZr systems with already assessed investigations of the Hf-C and Zr-C systems. New experimental information in higher-order systems has been used to improve the thermodynamic descriptions and to verify the reliability of the assessments. The main results of the experimental work are measurements of the composition of the cubic carbide in selected equilibria; measurements of the temperatures of the L + fcc + WC + graphite and L + fcc + WC + M6C equilibria in the C-Co-Hf, C-Co-Zr, and C-Co-W-X (X=Hf and Zr) systems; and measurements of the solubility of Hf and Zr in liquid cobalt. Detailed comparisons between calculated and experimental data are presented.
Johan Bratberg, Bo Jansson, Journal of Phase Equilibria and Diffusion Vol. 27 No. 3 (2006) 213-219

E0214 – Direct measurements of fusion and phase transition enthalpies in lanthanum oxide

Enthalpies of high-temperature phase transitions and fusion in lanthanum oxide (La2O3) were directly measured for the first time. Three samples were prepared by laser melting, sealed in tungsten crucibles, and heated in a differential thermal analyzer calibrated by melting Al2O3. Transformation enthalpy of La2O3 from A to H phase is 23 ± 5 kJ/mol at 2046 ± 5 °C and from H to X phase is 17± 5 kJ/mol at 2114 ± 5 °C. Lanthanum oxide melts at 2301 ± 10 °C, with enthalpy of fusion of 78 ± 10 kJ/mol.
Sergey V. Ushakova, Alexandra Navrotsky, J. Mater. Res., Vol. 26, No. 7, Apr 14, 2011

E0211 – Phase transition in LAMOX type compounds

La2Mo2O9 (LMO) was synthesized at lower temperature 973 K (LT-phase) by ceramic route. Differential thermal analysis (DTA) scan of LT-phase of LMO showed ??? transition at 843 K during heating and ??? conversion via a metastable g-phase during cooling. This was also confirmed by thermo-dilatometry and impedance spectroscopy. La2Mo1.95V0.05O9–d (LMVO), La1.96Sr0.04Mo2O9–d (LSMO) and La1.96Sr0.04Mo1.95V0.05O9–d (LSMVO) were prepared in a similar way. These compounds exhibited ??? transition on heating with shift in transition temperature, but the existence of ?-phase during cooling disappeared. Substitution increased the ionic conductivity of ?-phase and reduced that of ?-phase.
M. Ali (Basu), B. N. Wani, S. R. Bharadwaj, Journal of Thermal Analysis and Calorimetry, Vol. 96 (2009) 2, 463–468

E0206 – Phosphate glasses for tissue engineering: Part 2. Processing and characterisation of a ternary-based P2O5-CaO-Na2O glass fibre system

This paper presents the results of a study of the thermal properties, solubility and dimensions of a range of phosphate-based glass fibres (PB-GFs). The glass compositions were limited by fixing the P2O5 content to 45, 50 and 55 mol%, and varying the CaO mol% at 30, 35 and 40. PB-GFs were obtained from the 50 and 55 mol% P2O5 compositions; however, we were unable to obtain fibres from the 45 mol% compositions. This was linked to the cross-linked density, network connectivity and average chain length of the compositions studied. With regards to thermal parameters investigated, initial data showed an increase of the Tg and crystallisation temperatures with increasing CaO mol% at each fixed phosphate content. A decrease in Tg temperatures was also observed with increasing P2O5 content to 55 mol%. The crystallisation temperatures obtained for compositions with fixed phosphate at 55 mol%, showed a reverse pattern, with a decrease in values as compared to the fixed 50 mol% phosphate compositions. The diameters of the fibres all decreased with increasing RPMs as expected, and the solubility also increased with increasing RPMs. This was related to the increased surface area of the higher RPM fibres. There was also a decrease seen in solubility with increasing CaO mol%.
I. Ahmed, M. Lewis, I. Olsen, J.C. Knowles, Biomaterials 25 (2004) 501-507

E0205 – Phosphate glasses for tissue engineering: Part 1. Processing and characterisation of a ternary-based P2O5-CaO-Na2O glass system

This paper presents the results of a study of the thermal properties, X-ray powder diffraction (XRPD), NMR and solubility of a range of phosphate-based glasses. Ion release and pH measurements were also obtained. The compositions were limited by fixing the P2O5 mol% content at 45, 50 and 55 mol%, and varying the CaO mol% at 30, 35 and 40 mol%. Initial data collected from thermal analysis showed an increase in the Tg values, with increasing CaO mol%, as expected. An increase in crystallisation temperatures with increasing CaO mol% was also observed, with sharp peaks indicating the presence of single and/or double phases. Initial XRPD data revealed that the 45mol% P2O5 precipitated a calcium bridged trimetaphosphate (Na4Ca[PO3]6) at the sodium oxide contents of 25 and 20 mol%, but at the 15mol% level two phases formed, NaCa[PO3]3 and Ca2P2O7. The 50 mol% P2O5 compositions showed two sodium phosphate-rich phases [NaCa(PO3)3 and NaPO3] for the lower calcium containing compositions, and a calcium phosphate phase [CaP2O6] for compositions with higher CaO mol%. The 55 mol% P2O5 compositions, exhibited similar phases for the lower calcium containing compositions, and a single calcium phosphate phase (CaP2O6) was identified for the higher calcium containing composition. NMR analysis revealed the presence of Q1 and Q2 species in the 45mol% P2O5 compositions, and Q2 species present in the 50 and 55mol% P2O5 compositions. The non-linear data obtained from the thermal and solubility analyses conducted were attributed to the packing density of the 45mol% P2O5 compositions. The solubility was seen to decrease with increasing CaO mol%, for all the glasses investigated, and all the compositions showed a gradual decrease in pH with time, and this was accounted for by the release of Na+ and Ca2+ ions into solution.
I. Ahmed, M. Lewis, I. Olsen, J.C. Knowles, Biomaterials 25 (2004) 491-499

E0199 – Observation of nucleation effect on crystallization in lithium aluminosilicate glass by viscosity measurement

The crystal nucleation effect in lithium aluminosilicate glasses was investigated by the viscosity measurement with aid of the fiber elongation method. The abrupt increase of viscosity due to the crystallization of glass was observed in viscosity-temperature curve but the minimum viscosity temperature (Tn) related with crystallization showed a strong dependence on the nucleation state such as nucleation temperature, nucleation time and heating rate. The results by viscosity agreed well with those of DTA. The nucleation effect on the microstructure of glass-ceramics was also discussed. Finally, the nucleation effect on the crystallization kinetics was approached quantitatively by calculating the crystal volume from viscosity value.
K-D. Kim, S-H. Lee, H-K. Ahn, Journal of Non-Crystalline Solids 336 (2004) 195-201

E0196 – Study on some thermo-physical properties in Li2O-ZnO-SiO2 glass-ceramics

Lithium zinc silicate (LZS) glasses containing Li2O-ZnO-SiO2-Na2O-B2O3-P2O5 were prepared by conventional melt and quench technique and subsequently converted to glass-ceramics by controlled nucleation and crystallization. Both these parameters were determined by differential thermal analysis (DTA) studies. The effect of ZnO/(ZnO+SiO2) ratio on various thermo-physical properties was investigated by changing the ratio from 0.1 to 0.31. A number of crystalline phases have been identified by X-ray diffraction studies on the glass-ceramics including cristobalite (SiO2), lithium zinc silicate (Li3Zn0.5SiO4) and lithium silicate (Li2SiO3). Density (?) was found to increase from 2.62 to 2.82 g cm-3 while microhardness (Vicker's hardness number, VHN) decreased from 6.56 to 5.79 GPa with increase in ZnO/(ZnO+SiO2) ratio in the glass-ceramics. Average thermal expansion coefficient (TEC) in the temperature range 30-450°C increased from 125 x 10^(-7) to 185 x 10^(-7)/°C. The increase in expansion coefficient and decrease in microhardness are thought to be due to the formation of different phases which in turn influence the rigidity/bonding in the glass-ceramics. The material has been used for the fabrication of hermetic seal with copper. A study on the microstructure close to the interface of the glass-ceramics to metal is also carried out. The seal withstands a vacuum off ~10^(-6) Torr at helium leak rate of 3 x 10^(-10) Torr l/s.
B. Indrajit Sharma, Madhumita Goswami, P. Sengupta, V.K. Shrikhande, G.B. Kale, G.P. Kothiyal, Materials Letters 58 (2004) 2423-2428

E0195 – Processing route to an oxide dispersed iron/carbide composite

A new combination of techniques which should make it possible to produce oxide dispersed alloys by internal oxidation is suggested. The new technique has been used to produce a prototype alloy with a ferritic matrix containing fine (10-20 nm) oxides as well as a large volume fraction of carbides (about 40%). The microstructure indicates that it would be possible to produce an ironbase hard material with improved hot hardness. The technique is based upon an intermetallic starting material and utilises powder metallurgy and attrition ball milling.
H. Larsson, R. Erni, L-O. Nordberg, J. Agren, International Journal of Refractory Metals & Hard Materials 22 (2004) 159-167

E0191 – Thermal properties of Hf-based metallic glasses

Recently new Hf-based multicomponent amorphous alloys have been developed based on empirical rules for large glass forming ability. These ribbons were obtained by melt-spinning a master alloy, composed of Group IVB elements (Ti, Zr, Hf) of the Periodic Table with additions of late transition metals such as Cu or Ni. One of the best knownbulk glass-forming alloy systems is based on (Zr/Ti)-(Cu/Ni)-Al, the addition of Al of the IIIA group with sp electrons and strong interactions with Zr is a key factor in reducing the critical cooling rate for glass formation. Hf is chemically similar to Zr but has a much higher melting temperature. Characterization of the as-quenched (Hf/Zr/Ti)-(Cu/Ni)-(Al/Ga)-(Si/Ge) ribbonswas carried out by X-ray diffraction and the thermal stabilitywas followed by differential scanning calorimetry and differential thermal analysis.
A. Révész, J-L. Uriarte, D. Louzguine, A. Inoue, S. Surinach, M.D. Baro, A.R. Yavari, Materials Science and Engineering A 375-377 (2004) 381-384

E0188 – Calcium phosphates and glass composite coatings on zirconia for enhanced biocompatibility

Calcium phosphates (CaP) and phosphate-based glass (P-glass, xCaO-(0.55 x)Na2O-0.45P2O5 composition) composite coatings were obtained on a strong ZrO2 to improve biocompatibility, the mechanical strength and biological activity. Hydroxyapatite (HA) and P-glass mixed powder slurries were coated on the ZrO2 substrate, and subsequently heat-treated to obtain CaP- and P-glass composite coatings. The effects of glass composition (x=0.3, 0.4, 0.5 mol), mixing ratio of glass to HA (30%, 40%, 50% wt/wt), and heat treatment temperature (800°C, 900°C, 1000°C) on the coating properties were investigated. After heat treatment, additional calcium phosphates, i.e., dicalcium phosphate (DCP) and tricalcium phosphate (TCP), were crystallized, resulting in the formation of triphasic calcium phosphates (HA-TCP-DCP) surrounded by a glass phase. The relative amounts of the crystalline phases varied with coating variables. The higher heat treatment temperature and glass amount, and the lower CaO content in the glass composition rendered the composite coatings to retain the higher amounts of TCP and DCP while the initial HA decreased. These appearance of additional crystalline phases and reduction of HA amount were attributed to the combined effects, i.e., the meltingcrystallization of P-glass and the reaction between glass liquid phase and HA powder during thermal treatment. As a result of the glass phase in the composite coatings, their microstructures became much denser when compared to the pure HA coating. In particular, a completely dense structure was obtained at coating conditions with large amount of glass addition (50 wt%) at the glass composition of lower CaO content (0.3 mol CaO), and the following heat treatment above 800°C for 2 h. As a result, the adhesion strengths of the composite coating layers were significantly improved when compared to the pure HA coating. The highest strength of the composite coating was ~40 MPa, an improvement of ~80% with respect to the pure HA coating. The composite coatings showed much higher dissolution rates than the pure HA coating due to the newly formed crystallines (TCP and DCP) and the remaining glass phase. The osteoblast-like cells grew and spread actively on the composite coating samples. The proliferation numbers and alkaline phosphate (ALP) activities of the cells on the composite coatings were improved by ~30-40% when compared to Thermanox control and ZrO2 substrate, and were comparable to the pure HA coating. These findings suggested that the CaP and P-glass composites are potentially useful for hard tissue coating system, due to their morphological and mechanical integrity, enhanced bioactivity, and favorable responses to the osteoblast-like cells.
H-W. Kim, G. Georgiou, J.C. Knowles, Y-H. Koh, H-E. Kim, Biomaterials 25 (2004) 4203-4213

E0187 – Effect of Ce-Zr mixed oxides on the thermal stability of transition aluminas at elevated temperature

Ce-Zr mixed oxides is a kind of promoted oxygen storage capability material widely used in three-way catalysts. Various contents (10, 20, 30 and 40%) of Ce-Zr were physically mixed into the pure gamma-alumina for surface modification. The thermal stability of a series of Ce-Zr/Al2O3 supports was examined. Differential thermal analysis shows Ce-Zr mixed oxides increase the theta-alumina transformation temperature up to 1222°C. The powder X-ray diffraction studies show that minor theta-alumina phase still exists in the samples with > 20% Ce-Zr doping content after aging at 1050°C for 50 h. The best stabilizing effect is observed in the case of 20% Ce-Zr/Al2O3. Even after the accelerated aging test, it maintains an acceptable specific surface area (24m2 g-1) in relation with the delayed transformation of theta into alpha-alumina.
X. Wu, B. Yang, D. Weng, Journal of Alloys and Compounds 376 (2004) 241-245

E0184 – Preparation and crystallization of glasses in the system tetrasilicic mica-fluorapatite-diopside

The production of glasses whose composition ranged between tetrasilicic mica and fluorapatite-diopsite 50/50 (in wt.%) was investigated. Glass-ceramics were obtained by both bulk crystallization and sintering of glass powder compacts. The experimental results showed that increasing amount of apatite and diopsite components in the ternary system until 50% mica content generally caused decrease of melting temperature and increasing stability of glass against spontaneous crystallization during cooling after casting. Liquid immiscibility, whose features depend on the particular glass composition, characterized all the investigated glasses but it was more pronounced in the glasses with higher amount of apatite and diopsite components. The investigated glasses are preferably crystallized in bulk form between 700 and 900°C, resulting in formation of different combinations between mica, fluorapatite and diopsite, depending on the particular composition. The obtained glass-ceramics exhibited attractive aesthetics, structural integrity and dense structure.
D.U. Tulyaganov, S. Agathopoulos, H.R. Fernandes, J.M. Ventura, J.M.F. Ferreira, Journal of the European Ceramic Society 24 (2004) 3521-3528

E0183 – Thermal characterization of Cu60ZrxTi(40-x) metallic glasses (x = 15; 20, 22, 25, 30)

The crystallization behavior, the thermal stability and the microhardness of Cu60ZrxTi(40-x) amorphous alloys (x = 15; 20, 22, 25, 30) prepared by melt-spinning have been studied by means of differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD) and microhardness tests. DSC analysis have confirmed the existence of glass transition, followed by a supercooled liquid region in all the compositions. However, depending on the Zr content, different crystallization behavior has been observed. The apparent activation energies of the crystallization processes have been determined and the obtained values indicate high thermal stability for all the alloys. XRD-patterns of the as-quenched samples showed a broad symmetric halo typical of a fully amorphous structure. Independently of the composition, after the first crystallization stage the XRD patterns present a structure similar to that of an amorphous one. But the final developed microstructure depends on the composition of the alloys. The addition of Zr has not shown significant differences in microhardness of the amorphous alloys, although they have exhibited good mechanical properties.
A. Concustell, M. Zielinska, A. Révész, L.K. Varga, S. Surinach, M.D. Baro, Intermetallics 12 (2004) 1063-1067

E0181 – Electrical impedance determination of phase transitions in glasses and melts

The electrical impedances of glasses in the system BaO*Al2O3*B2O3 were studied in the temperature range from 550 to 1150°C using different heating and cooling rates. The specific conductivities were illustrated by fitting Arrhenius functions to the data and the derivative (-d ln ?/ d(1/kT)). In this system, the activation energy of the electrical conductivity depends on temperature. Crystallization of the melt affects the derivative. Depending on the specific conductivities and the respective activation energies of the liquid and the crystalline phase, maxima or minima (or both) are observed in the derivative. The melting of the crystalline phase during heating results in a maximum of the derivative. The shape of the derivative can be explained taking into account the specific conductivities and the attributed activation energies of the liquid and crystalline phase.
R. Keding, D. Tauch, C. Rüssel, Journal of Non-Crystalline Solids 348 (2004) 123-130

E0177 – Dielectric properties of sodium fluoride added kaolinite at different firing temperatures

The dielectric properties of NaF doped and undoped kaolinite were measured as a function of frequency in the range 40 kHz to 50 MHz. The epsilon', tan d and ?ac values are given as a function of firing temperature and NaF concentration. The addition of NaF increased the dielectric constant of pure kaolinite. However, the dielectric constant and ac conductivity of mullite obtained by the addition of NaF to kaolinite decreased from the value for pure kaolinite. Furthermore, the addition of NaF reduced the formation temperature of mullite from 1200 to 1000°C.
H. Zipkin, L. Israel, S. Güler, C. Güler, Ceramics International 33 (2007) 663-667

E0176 – Influence of Ce3+ doping on the structure and luminescence of Er3+-doped transparent glass-ceramics

Transparent glass-ceramics possess high thermal and mechanical properties, easy shaping allowing fibers elaboration and easy synthesis. However, previously studied Yb:Er-doped glass-ceramics do not appear efficient enough for optical amplification at 1.5 µm in the telecommunication window. So, the addition of Ce3+ doping ions was performed. Oxyfluoride glasses (GeO2-PbO-PbF2) doped with ErF3, YbF3 and CeF3 were prepared and heated above glass transition temperature to obtain transparent glass-ceramics. Such treatment brings about the precipitation of fluorite-type nanocrystallites embedded into an amorphous oxide phase. Differential Thermal Analysis shows evidence that CeF3 acts as nucleating agent for the heterogeneous crystallization of the beta-PbF2 phase. Through Transmission Electron Microscopy the morphology of these glass-ceramics was studied. Energy dispersive X-ray microanalysis and unit cell parameter study show a segregation of the three rare-earth ions inside the fluorite crystallites, forming a solid solution Pb(1-x-y-z)Er(x)Yb(y)Ce(z)F(2+x+y+z). The luminescence characteristics of the glass-ceramics doped with ErF3, YbF3 and CeF3 were compared to those of Yb:Er-doped glass-ceramics. CeF3 enables to dramatically decrease the up-conversion fluorescence of Er3+. The study of temporal dynamic of the 4 I 13/2 level of Er3+ reveals a cross-relaxation process between Er3+ and Ce3+. Hence, the presence of Ce3+ enables to decrease the Er3+ up-conversion fluorescence at the benefit of the fluorescence of interest at 1.5 µm, which is strongly enhanced.
G. Dantelle, M. Mortier, D. Vivien, G. Patriarche, Optical Materials 28 (2006) 638-642

E0174 – Homogeneity range and order-disorder transitions in R(1-x)Ni2 Laves phase compounds

The homogeneity range of R(1-x)Ni2 Laves phases (R=Ce, Gd, Tb) has been studied by X-ray diffraction, microprobe analysis and density measurements. In these compounds, the number of R vacancies varies as a function of the atomic number of the rare earth metal and the nominal composition. For R=Tb the number of vacancies varies by 0
V. Paul-Boncour, A. Lindbaum, M. Latroche, S. Heathman, Intermetallics 14 (2006) 483-490

E0172 – Characteristics of chabazite modified by hexadecyltrimethylammonium bromide and of its affinity toward chromates

The FTIR, XRD, SEM and equilibrium data concerning the chabazite modified by hexadecyltrimethylammonium bromide (HDTMA) are presented. The zeolite plays the role of surfactant carrier. Its sodium form is converted to surfactant form through its equilibration with aqueous solutions of HDTMA. It is established that HDTMA cations are incorporated into the chabazite structure via ion-exchange and Van der Waals forces. Gauche and trans conformers are recognised in alkyl chains arrangement of surfactant cations. HDTMA-chabazite is evaluated as efficient adsorbent for chromates with quick kinetics (equilibrium completed in 120 min) and high adsorption maximum a=0.00005 mol/g.
M. Majdan, S. Pikus, Z. Rzaczynska, M. Iwan, O. Maryuk, R. Kwiatkowski, H. Skrzypek, Journal of Molecular Structure 791 (2006) 53-60

E0170 – Er3+-doped PbF2: Comparison between nanocrystals in glass-ceramics and bulk single crystals

An appropriate annealing of a GeO2-PbO-PbF2:ErF3 glass leads to the formation of a glass-ceramic, composed of Pb(1-x)ErxF(2+x) nanosized crystallites dispersed throughout an amorphous oxide matrix. These nanocrystallites are compared to Er3+-doped PbF2 bulk single crystals. The influence of the annealing temperature on the glass-ceramics characteristics is thoroughly investigated. For several glass-ceramics resulting from different heat treatments, the quantity of crystallized PbF2, as well as the segregation of Er3+ ions into the crystallites, has been studied through two methods: first, the study of the crystallographic characteristics and second, the evolution of the optical properties. It was evidenced that, for a heat treatment over 365°C, the whole PbF2:Er has completely crystallized and that the segregation of Er3+ ions into the crystallites was total. Strong interactions between Er3+ ions occur in the Pb(1-x)ErxF(2+x) single and nanocrystals, promoting cross-relaxation processes, under 488-nm excitation, and favouring the 660- (red) and 810-nm emissions at the expense of the 550-nm (green) one.
G. Dantelle, M. Mortier, G. Patriarche, D. Vivien, Journal of Solid State Chemistry 179 (2006) 1995-2003

E0167 – Production and identification of rare-earth doped lithium triborate

Research in the field of non-linear optical (NLO) devices lead to an increasing interest in new borate compounds, capable of expanding the frequency range provided by common laser sources. Lithium triborate (LBO) is a newly developed ideal non-linear optical crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. In this study, synthesis and identification of rare-earth doped lithium triborate was carried out. Borates containing rare-earth elements are of great interest since they are found to be superior in non-linear optical applications. Lithium triborate was produced from the solid-state reaction. Lithium triborate was then doped with some rare-earth elements (Gd, La, Y, etc.) in several different concentrations. In this study, LBO samples doped with Gd are presented. Characterization of the new products was done by X-ray diffraction (XRD) and infrared (IR) analysis. Differential thermal analysis (DTA) was used for examination of the thermal properties of the compounds, morphology of new compounds was observed by scanning electron microscopy (SEM). The compounds are then subjected to thermoluminescence (TL) studies. From the XRD studies, no change related to addition of the rare-earth elements was observed. IR analysis showed that there is no change related to B-O link with the addition of rare-earth elements. DTA studies showed that the melting point of LBO decreases with the addition of rare-earth elements. In the SEM images, particles of rare-earth elements and lithium triborate were observed clearly.
B. Ardiçoglu, G. Özbayoglu, Z. Özdemir, A. Yilmaz, Journal of Alloys and Compounds 418 (2006) 77-79

E0166 – A novel simple method to stably synthesize Ti3AlC2 powder with high purity

In this work, a novel simple method is presented to synthesize highly pure Ti3AlC2 powder by heating 2TiC/Ti/Al (molar ratio) powder system between 1300°C and 1400°C for 15-30 min in flowing argon atmosphere. 2TiC/Ti/Al is selected as the raw material because of its much lower exothermal quantity than elemental 3Ti/Al/2C powder system in reacting process. The purity of Ti3AlC2 is not sensitive to the final temperature, soaking time or raw material scale. Its content is maintained around 97 wt.%, even though the scale of mixed raw materials vary from 5 g to 1000 g. The synthesized samples can be easily ground into powders with a mean particle size of 4.9 µm. Synthesis mechanism shows that both Ti2AlC and Ti3AlC2 will generate from the reaction among TiC, Ti and Al below 1200°C. Above 1300°C, Ti2AlC will continue to react with TiC and generate Ti3AlC2. The formation of Al liquid phase above 660°C is considered as a promoting factor in the reacting process.
C. Peng, C-A. Wang, Y. Song, Y. Huang, Materials Science and Engineering A 428 (2006) 54-58

E0165 – High temperature phase transition in Sm0.95MnO2.925

Samarium deficient SmMnO3 crystallizes in orthorhombic phase and it transforms to another orthorhombic phase at ~743 K. The above phase transformation was experimentally investigated by a variety of techniques like differential thermal analysis, dilatometry, high temperature X-ray diffraction and electrical conductivity measurements.
R.V. Wandekar, B.N. Wani, S.R. Bharadwaj, Journal of Alloys and Compounds 437 (2007) 53-57

E0164 – Crystal structure and thermal evolution of inedite alpha-Zr2O(PO4)2 and alpha-Hf2O(PO4)2

The structures of isotypic alpha-Zr2O(PO4)2 (S.G. I 2/m, a = 10.2726(6), b = 6.5957(3), c = 10.0665(5) Å, beta = 95.433(3)°, V = 679.00(6) Å3, Z = 4) and alpha-Hf2O(PO4)2 (S.G. I 2/m, a = 10.2301(3), b = 6.5819(2), c = 10.0075(5) Å, beta = 95.371(1)°, V = 670.87(3) Å3, Z = 4) have been resolved ab initio by Rietveld analysis. At variance with the beta-form, they show both MO6 and MO7 polyhedra (M = Zr, Hf), forming ribbons with the PO4 tetrahedra. A lattice energy calculation explains why the alpha-form is less stable than the beta-form, thus making the alpha-beta transition irreversible. However, the substitution of smaller HfIV for ZrIV allows to keep the alpha-framework up to 1500°C by stabilizing the MO6 octahedra.
G. Wallez, J-P. Souron, M. Quarton, Solid State Sciences 8 (2006) 1061-1066

E0161 – Study of the magnesia additive on the characterization of zirconia-magnesia composite sphere

Zirconia composite with varying amounts of magnesia was prepared by sol-gel technique. A series of carefully designed experiments were conducted to obtain data needed to assist the comparison of the resultant composites in terms of surface area, pore diameter, pore volume, crystalline phase and their stability to temperature. The results show that the presence of magnesia can be helpful for stabilization of zirconia composite, and different amounts of magnesia doping result in ultimate composite materials with different properties. We can tailor the structural and surface characteristics through changing the reactant ratio of magnesium chloride to zirconyl chloride to cater for its various applications, such as catalysts, chromatographic packings and so on.
Z-G. Shi, L. Xu, S-L. Da, Y-Q. Feng, Microporous and Mesoporous Materials 94 (2006) 34-39

E0160 – The A(1-x)UNbO(6-x/2) compounds (x = 0, A = Li, Na, K, Cs and x = 0.5, A = Rb, Cs): from layered to tunneled structure

Attempts to prepare alkaline metal uranyl niobates of composition A(1-x)UNbO(6-x/2) by high-temperature solid-state reactions of A2CO3, U3O8 and Nb2O5 led to pure compounds for x = 0 and A = Li (1), Na (2), K (3), Cs (4) and for x = 0.5 and A = Rb (5), Cs (6). Single crystals were grown for 1, 3, 4, 5, 6 and for the mixed Na0.92Cs0.08UNbO6 (7) compound. Crystallographic data: 1, monoclinic, P2 1/c, a = 10.3091(11), b = 6.4414(10), c = 7.5602(5) Å , beta = 100.65(1), Z = 4, R1 = 0.054 (wR2 = 0.107); 3, 5 and 7 orthorhombic, Pnma, Z = 8, with a = 10.307(2), 10.272(4) and 10.432(3) Å , b = 7.588(1), 7.628(3) and 7.681(2) Å , c = 13.403(2), 13.451(5) and 13.853(4) Å , R1 = 0.023, 0.046 and 0.036 (wR2 = 0.058, 0.0106 and 0.088) for 3, 5 and 7, respectively; 6, orthorhombic, Cmcm, Z = 8, and a = 13.952(3), b = 10.607(2) Å , c = 7.748(2) Å , R1 = 0.044 (wR2 = 0.117). The crystal structure of 1 is characterized by [UNbO6]- layers of uranophane sheet anion topology parallel to the (100) plane. These layers are formed by the association by edge-sharing of [UO5]4- chains of edge-shared UO7 pentagonal bipyramids and [NbO4]3- chains of corner-shared NbO5 square pyramids alternating along the [010] direction. The Li+ ions are located between two consecutive layers and hold them together; the Li+ ions and two layers constitute a neutral "sandwich" {(UNbO6)- - (Li)2 2+ - (UNbO6)-}. In this unusual structure, the neutral sandwiches are stacked one above another with no formal chemical bonds between the neutral sandwiches. The homeotypic compounds 3, 5, 6, 7 have open-framework structures built from the association by edge-sharing in two directions of parallel [UO5]4- chains of edge-shared UO7 pentagonal bipyramids and [Nb2O8]6- ribbons of two edge-shared NbO6 octahedra further linked by corners. In 3, 5 and 7, the mono-dimensional large tunnels created in the [001] direction by this arrangement can be considered as the association by rectangular faces of two columns of triangular face-shared trigonal prisms of uranyl oxygens. In 3 and 7, all the trigonal prisms are occupied by the alkaline metal, in 5, they are half-occupied. In 6, the polyhedral arrangement is more symmetric and the tunnels created in the [010] direction are built of face-sharing cubes of uranyl oxygens totally occupied by the Cs atoms. This last compound well illustrates the structure-directing effect of the conterion.
S. Surblé, S. Obbade , S. Saad, S. Yagoubi, C. Dion, F. Abraham, Journal of Solid State Chemistry 179 (2006) 3238-3251

E0157 – The nucleation and crystallization of fine grained leucite glass-ceramics for dental applications

Objectives. The aims of the study were to control the nucleation and crystal growth of selected aluminosilicate glass powders, to produce uniform leucite glass-ceramic microstructures consisting of fine (<1000 nm) grained leucite crystals. Methods. A starting glass composition of wt%; 64.2% SiO2, 16.1% Al2O3, 10.9% K2O, 4.3% Na2O, 1.7% CaO, 0.5% LiO2 and 0.4% TiO2 was heated in an electric furnace and later quenched to produce glasses. The glass powders were ball milled to two different particle sizes and heattreated using one and two-step crystallization heat treatments. Dta, Xrd, and Sem analyses was used to characterise and explore the crystallization kinetics of the glasses. Results. Selected heat treatments of the glass powders produced a uniform distribution of fine tetragonal leucite crystals (mean±S.D.) 0.1±0.2 µm2 in the glassy matrix, with minimal matrix microcraking in the glass-ceramics produced. The addition of a two-step heat treatment increased the leucite volume fraction in all instances. Significance. Selected crystallization heat treatments and powder particle sizes were used to control the leucite crystal size, distribution and volume fraction, in order to produce uniformly distributed ultra fine grained tetragonal leucite glass-ceramics for dental applications.
M.J. Cattell, T.C. Chadwick, J.C. Knowles, R.L. Clarke, D.Y.D. Samarawickrama, Dental Materials 22 ( 2006 ) 925-933

E0147 – Influence of expandable graphite on fire resistance and water resistance of flame-retardant coatings

Expandable graphite (EG) coating and ammonium polyphosphate-pentaerythritol-melamine (APP-PER-MEL) coating were prepared. Thermal degradation and char formation of the coatings were investigated by differential thermal analysis (DTA), thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results have shown that the anti-oxidation and fire-resistant properties of expandable graphite coating containing EG with size of 74 lm are better than those of APP-PER-MEL coating. The static immersion test was applied to study water resistance of the coatings, and the fire protection test and mechanical test were used to analyse heat insulation and mechanical properties of coatings before and after water immersion. The fire-resistant and mechanical properties of APP-PER- MEL coating were severely damaged by water immersion, whereas EG coating containing 8.5% EG with size of 74 lm could retain the good fire resistance even after 500 h water immersion.
Z. Wang, E. Han, W. Ke, Corrosion Science 49 (2007) 2237-2253

E0146 – Proof of the ISS-concept for LTA and FAU membranes and their characterization by extended gas permeation studies

Molecular sieve membranes are expected to separate molecules by size and shape provided that the intercrystalline defect transport is negligible. However, in the case of a non-negligible mass transport through the grain boundaries in the polycrystalline zeolite layer, the separation properties of the membrane become influenced by both the regular and defective transport. Nevertheless, also in this case proper separation performance is found due to adsorptive and/or diffusive interactions of the mixture components with the membrane. In a previous report [M. Noack, P. Kölsch, A. Dittmar, M. Stöhr, G. Georgi, R. Eckelt, J. Caro, Micropor. Mesopor. Mater. 97 (2006) 88] the concept of crystal intergrowth supporting substances (ISS) was demonstrated. The charge neutralization of the negatively charged crystal surfaces of a growing MFI membrane by the positively charged ISS molecules improves the crystal intergrowth and results in a higher permeation selectivity. LTA and FAU membranes can separate water-organic mixtures in an excellent way but they fail in shapeselective gas separations. Therefore, many attempts were made to improve the separation properties of LTA and FAU membranes for gases. Zeta potential measurements on the Al-rich zeolite crystals LTA and FAU show a strong negative surface charge like it was found in [Noack et al., 2006] for MFI. In this work LTA and FAU multi-layer membranes were prepared by using an ISS. These membranes were characterized by SEM, XRD, permporosimetry, single gas permeation in combination with different probe molecules for the selective blocking of the micro and mesopore system. The results are discussed on the basis of pore condensation or pore narrowing according to the Kelvin and Halsey equations. Repeated strong de-watering of the hydrophilic LTA and FAU membranes have changed the membrane structure.
M. Noack, P. Kölsch, A. Dittmar, M. Stöhr, G. Georgi, M. Schneider, U. Dingerdissen, A. Feldhoff, J. Caro, Microporous and Mesoporous Materials 102 (2007) 1-20

E0145 – The effect of Al2O3 on sintering and crystallization of MgSiO3-based glass-powder compacts

The influence of Al2O3 (8 wt.%) on sintering and crystallization features of glass powders based on magnesium silicate (MgSiO3) was experimentally determined. The investigated compositions were Y0.125Mg0.875Si0.875B0.125O3 and Y0.125Mg0.725Ba0.15Si0.875B0.125O3. For the experiments, glasses in bulk and frit forms were produced by melting in Pt-crucible at 1600°C for 1.5 h. Glass-powder compacts were sintered at different temperatures between 900°C and 1100°C. The evolution of crystalline regime was determined by in situ recording of X-ray diffractograms of fine glass powders at elevated temperatures. The results and their discussion showed that addition of 8 wt.% Al2O3 in glass batches affected the thermal properties of the glasses and resulted in MgSiO3-based glass ceramics well sintered between 900°C and 1100°C. In the BaO-free MgSiO3 glass ceramics, clino- and orthoenstatite crystallize while the presence of BaO favours the formation of hexacelsian.
A. Goel, D.U. Tulyaganov, S. Agathopoulos, J.M.F. Ferreira, Ceramics International xxx (2007) xxx-xxx

E0143 – Three-dimensional framework of uranium-centered polyhedra with non-intersecting channels in the uranyl oxy-vanadates A2(UO2)3(VO4)2O (A = Li, Na)

The uranyl vanadates A2(UO2)3(VO4)2O (A = Li, Na) have been synthesized by solid-state reaction and the structure of the Li compound was solved from single-crystal X-ray diffraction. The crystal structure is built from [UO5] 4- chains of edge-shared U(2)O7 pentagonal bipyramids alternatively parallel to a- and b-axis and further connected together to form a three-dimensional (3-D) arrangement. The perpendicular chains are hung on both sides of a sheet [(UO2)(VO4)2] 4- parallel to (001), formed by U(1)O6 square bipyramids connected by VO4 tetrahedra, and derived from the autunite-type sheet. The resulting 3-D framework creates nonintersecting channels running down the a- and b-axis formed by empty face-shared oxygen octahedra, the Li+ ions are displaced from the center of the channels and occupy the middle of one edge of the common face. The peculiar position of the Li+ ion together with the full occupancy explain the low conductivity of Li2(UO2)3(VO4)2O compared with that of Na(UO2)4(VO4)3 containing the same type of channels half occupied by Na+ ions in the octahedral sites. Crystallographic data for Li2(UO2)3(VO4)2O: tetragonal, space group I41/amd, a = 7,3303(5) Å, c = 24,653(3) Å, V = 1324,7(2) Å^3, Z = 4, Pmes = 5,32(2) g/cm3, Pcal = 5,36(3) g/cm3, full-matrix least-squares refinement basis on F² yielded, R1 = 0,032, wR2 = 0,085 for 37 refined parameters with 364 independent reflections with I>2s(I).
S. Obbade, L. Duvieubourg, C. Dion, F. Abraham, Journal of Solid State Chemistry 180 (2007) 866-872

E0142 – Fabrication and characterization of Pb-free transparent dielectric layer for plasma display panel

Glasses within the Bi2O3-B2O3-BaO-ZnO system were examined as potential replacements for PbO-based glass frits with low firing temperatures. These frits are used in the transparent dielectric layer of plasma display panels (PDP). The glass transition temperature (Tg) of the prepared glasses varied between 450 and 460°C. These glasses display dynamic dielectric properties, high transparency and thermal expansion as well as matching well with substrate glass. The thermal coefficient of expansion (TCE) was with the desired range of 81-86.10^(-7)/K. Moreover, when the screen printed film was heat-treated at 570°C for 30 min, optical transmittance (83%), root-mean square (rms) roughness (177.6 Å ), dielectric constant (10.25) and withstand voltage (4.15 kV) satisfied the requirements necessary for transparent dielectric layers to be used in PDP applications.
J-Y. Song, S-Y. Choi, Displays 27 (2006) 112-116

E0141 – Preparation and characterization of CuO doped Bi2O3-B2O3-BaO-ZnO glass system for transparent dielectric layer

The electrical, thermal, optical, and morphological properties of CUO doped Bi2O3-B2O3-BaO-ZnO glasses were studied as a PbOfree, low firing transparent dielectric layer for plasma display panels (PDP). CuO improved the transmittance of Bi2O3-B2O3-BaO-ZnO by up to 84% in the visible region, eliminating a yellowish color typical of Bi2O3-B2O3-BaO-ZnO. A slight absorption within the near infrared (NIR) region was also observed. The glass transition temperature (Tg), thermal coefficient of expansion (TCE), and root-mean square (rms) roughness of 0.005 wt% CuO doped Bi2O3-B2O3-BaO-ZnO were found to be 455°C, 81.4 x 10^(-7)/K, respectively, and 162 ± 14 Å , which satisfied the requirements for a transparent dielectric layer for PDP application.
J-Y. Song, T-J. Park, S-Y. Choi, Journal of Non-Crystalline Solids 352 (2006) 5403-5407

E0140 – Thermomechanical characteristics of calcium aluminate cement and sand tapes prepared by tape casting

The present paper concerns the mechanical characterization of calcium aluminate cement and sand tapes prepared by tape casting, including ultrasonic measurements of Young's modulus at high temperature and evaluation of four point flexural behavior after heat treatments in the range of 20-1400°C. It is shown that dehydration strongly affects mechanical properties in the 400-900°C range, but that treatments at temperatures higher than 1200°C increase both Young's modulus and strength. By correlation with thermal and X-ray diffraction analyses, the evolutions of thermomechanical properties have been related to phase and microstructural changes when heating the material after hydration: conversion of hydrates and dehydration at low temperature, then, crystallization of C-A and C-A-S phases and finally sintering at the highest temperatures. In a last part, it is shown that the reinforcement by glass fibres enhances the mechanical properties, in particular in the temperature range of dehydration, and gives to the material a non-brittle behavior.
J. Soro, A. Smith, C. Gault, Journal of the European Ceramic Society 26 (2006) 3799-3807

E0139 – Nucleation and crystal growth of glasses produced by a generic plasma arc-process

The feasibility to crystallise a glass prepared by thermal plasma vitrification of hospital wastes to produce a glass-ceramic suitable to be used as a construction material was investigated by using differential thermal analysis (DTA) and X-ray diffraction (XRD). Two crystallisation exotherms in DTA were attributed to the formation of wollastonite and a crystalline phase belonging to the melilite group (gehlenite or akermanite). DTA tests have shown that the glass is not suitable for bulk crystallisation and must be converted into a glass-ceramic by using the sintering process route through a single crystallisation step at 1000°Cfor 10 min.
M.S. Hernandez-Crespo, M. Romero, J.Ma. Rincon, Journal of the European Ceramic Society 26 (2006) 1679-1685

E0138 – Synthesis of glass-ceramics in the CaO-MgO-SiO2 system with B2O3, P2O5, Na2O and CaF2 additives

Glass-ceramics based on the CaO-MgO-SiO2 system with limited amount of additives (B2O3, P2O5, Na2O and CaF2) were prepared. All the investigated compositions were melted at 1400°C for 1 h and quenched in air or water to obtain transparent bulk or frit glass, respectively. Raman spectroscopy revealed that the main constituents of the glass network are the silicates Q1 and Q2 units. Scanning electron microscopy (SEM) analysis confirmed liquid.liquid phase separation and that the glasses are prone to surface crystallization. Glass-ceramics were produced via sintering and crystallization of glass-powder compacts made of milled glass-frit (mean particle size 11-15µm). Densification started at 620-625°C and was almost complete at 700°C. Crystallization occurred at temperatures >700°C. Highly dense and crystalline materials, predominantly composed of diopisde and wollastonite together with small amounts of akermanite and residual glassy phase, were obtained after heat treatment at 750°C and 800°C. The glass.ceramics prepared at 800°C exhibited bending strength of 116-141MPa, Vickers microhardness of 4.53-4.65 GPa and thermal expansion coefficient (100-500°C) of 9.4-10.8 x 10^(-6) K-1.
D.U. Tulyaganov, S. Agathopoulos, J.M. Ventura, M.A. Karakassides, O. Fabrichnaya, J.M.F. Ferreira, Journal of the European Ceramic Society 26 (2006) 1463-1471

E0137 – Processing of glass-ceramics in the SiO2-Al2O3-B2O3-MgO-CaO-Na2O-(P2O5)-F system via sintering and crystallization of glass powder compacts

Glass-ceramics were produced by crystallization of glasses in the SiO2-Al2O3-B2O3-MgO-CaO-Na2O-F system. The experimental results showed that bulk glasses are prone to surface crystallization. Hence, crystallization of bulk glasses resulted in non-homogeneous crystalline materials, which comprised relatively coarse crystals. Therefore, processing was realized using glass-powder compacts. Maximum densification was reached at 700-750°C. This interval is positioned at relatively lower temperatures than those often reported for similar sintered glass-ceramics. Doping with P2O5 improved sintering behaviour and broadened sintering temperature range. Sintering between 750 and 800°C resulted in materials, which exhibited dense crystalline microstructure and the maximum flexural strength.
D.U. Tulyaganov, S. Agathopoulos, H.R. Fernandes, J.M.F. Ferreira, Ceramics International 32 (2006) 195-200

E0135 – Low temperature synthesis of anorthite based glass-ceramics via sintering and crystallization of glass-powder compacts

Anorthite based glass-ceramics were synthesized. The investigated glass compositions are located close to the anorthite-rich corner of the fluorapatite-anorthite-diopside ternary system. Glass powder compacts with mean particle size of 2 and 10 µm were prepared. Sintering behaviour, crystallization and the properties of glass-ceramics were investigated between 800 and 950°C. In the case of specimens made from the finer particles, complete densification was achieved at a remarkably low temperature (825°C) and the highest mechanical strength was obtained at 850°C, but density significantly decreased at higher temperatures. The samples prepared from the larger particles exhibited higher values of density, shrinkage and bending strength within a wider temperature range (825-900°C). Anorthite was predominantly crystallized between 850 and 950°C, along with traces of fluorapatite. Diopside was detected only in the MgO richer compositions.
V.M.F. Marques, D.U. Tulyaganov, S. Agathopoulos, V.Kh. Gataullin, G.P. Kothiyal, J.M.F. Ferreira, Journal of the European Ceramic Society 26 (2006) 2503-2510

E0134 – Crystallization of lanthanum and yttrium aluminosilicate glasses

The crystallization behaviour of aluminosilicate glasses of lanthanum (LAS) and yttrium (YAS) containing 2-8 mol% of Ln2O3 (Ln = La or Y), 12-30 mol% of Al2O3, and 64-80 mol% of SiO2 has been studied by DTA, XRD and SEM-EDX analysis. X-ray diffraction results indicate the presence of the mullite phase and La2Si2O7 in the monoclinic high-temperature G form (group space P21/c) for the LAS glasses, and mullite y-Y2Si2O7 in the monoclinic structure (group space C2/ m) and a small amount of b-Y2Si2O7 in the orthorhombic structure (space group Pna2) for the YAS. For both cases, very little tridymite phase is observed. The results also show that the values of Tg for YAS are higher than those for LAS glasses. The crystallization of LAS glasses is more difficult than that of YAS. For all samples, we observed only one kind of mullite (Al/Si = 3.14).
N. Sadiki, J.P. Coutures, C. Fillet, J.L. Dussossoy, Journal of Nuclear Materials 348 (2006) 70-78

E0133 – Effect of ZrO2 nucleant on crystallisation behaviour, microstructure and magnetic properties of BaO-Fe2O3-B2O3-SiO2 glass ceramics

Differential thermal analysis, X-ray diffractometry and scanning electron microscopy with energy dispersive spectroscopy were used to study the crystallisation of glass ribbons with a composition of 35% BaO, 35% Fe2O3, 20% B2O3 and 10% SiO2 (mol%) with 1% ZrO2 added as a nucleant. The magnetic properties of ribbons prepared via cooling the melts between steel rollers were measured with a vibrating sample magnetometer. The addition of ZrO2 apparently resulted in a quite distinct glass-in glass phase separation in as prepared specimens, greatly affecting the nucleation process. Heat treatment of specimens at their DTA exo-peak temperature of 721°C led to the formation of BaFe12O19 and BaB2O4 as the only crystalline phases. The glass ribbons heat treated in one-stage exhibited a quite non-uniform distribution of particles exhibiting exagerated grain growth, while a two-stage heat treatment at 526 and 721°C for different time periods generally led to more uniform distribution of platelet particles. The values of saturation magnetisation of specimens were in the Ms = 23-29 emu/g range, while the coercivity values varied between Hc = 1800-3000 Oe.
M. Mirkazemi, V.K. Marghussian, A. Beitollahi, S.X. Dou, D. Wexler, K. Konstantinov, Ceramics International 33 (2007) 463-469

E0132 – Local and average atomic order of ion-conducting Bi0.775La0.225O1.5 studied by neutron scattering and reverse Monte Carlo simulations

Bi0.775La0.225O1.5 has been investigated by means of neutron scattering in combination with Rietveld refinement and reverse Monte Carlo (RMC) simulations to study the average and local atomic order of the material. At low temperature the crystallographic analysis shows a clear split of anionic positions similar to that reported for Sr doped bismuth oxides. Although this split appears to be absent in the average structure at high temperature, an even larger split of Bi-O local distances is found in the pair distribution function calculated from the RMC models. This latter feature can be indicative of a tendency to have similar oxygen environments for all Bi atoms at high temperature, as a precursor of the fluorite structure that is the stable phase at even higher temperatures.
A. Ahi, A. Mellergard, S-G. Eriksson, Solid State Ionics 177 (2006) 289-297

E0129 – A study on colouration and axial variation of composition in the single crystal of lead tungstate grown by Czochralski technique

A thorough study reveals the importance of a proper synthesis condition in the growth of colour-free lead tungstate single crystals. An optimised synthesis scheme is described. The temperature gradient required, above the melt, for the growth of crack-free crystals is 25°C/cm. Differential thermal analysis shows that an improper synthesis results in a compositional variation along the vertical axis of the crystal. UV-visible absorption detects an enhanced absorption in the wavelength, 380-450nm for the pale yellow-coloured crystals. Annealing in air for 15 h at 1050°C removes the special blue absorption in the coloured crystal.
I. Bhaumik, S. Ganesamoorthy, A.K. Karnal, V.K. Wadhawan, Journal of Crystal Growth 275 (2005) e839-e842

E0126 – Growth features of RENi2B2C (RE = Y, Ho, Tb) single crystals

Features characterizing the perfection of high-quality YNi2B2C, HoNi2B2C and TbNi2B2C single crystals grown by the floating zone technique with optical heating in the TSFZ regime are investigated. The grown crystals are crack free, single phase and single crystalline in the whole cross-section. Various origins of small fractions of minority phases in several crystals impurities, phase diagram features and limits of growth parameters are revealed. For the crystals a subgrain misorientation o0.151 was determined by neutron diffraction. The YNi2B2C crystals show an extremely narrow superconducting transition width 0.1K and high residual resistivity ratios up to 48. Longitudinal and radial element segregation phenomena with particular respect to the light elements are related to the various modifications of superconducting properties and Tc variations in HoNi2B2C single crystals. The interface shape and radial segregation suggest a noticeable convection flow in HoNi2B2C melts.
D. Souptel, G. Behr, A. Kreyssig, W. Löser, Journal of Crystal Growth 276 (2005) 652-662

E0123 – Thermodynamic exploitation of the liquidus curves in the MIPO3-Pb(PO3)2, MIPO3-Cu(PO3)2 AND MIPO3-Ce(PO3)3 SYSTEMS(MI=Li, Na, K, Rb, Cs, Ag, Tl)

The thermodynamic exploitation of the solid-liquid equilibria in the M I PO3-Pb(PO3)2, M I PO3-Cu(PO3)2 and M I PO3-Ce(PO3)3 systems (with M I =Li, Na, K, Rb, Cs, Ag, Tl) is carried out using a semi-empirical equation of the liquidus curves already used with success for similar binary systems. The enthalpy of fusion is calculated for each pure polyphosphate on the assumption that the liquid solution is ideal and only formed by M I PO3 and M(PO3)q entities (q=2 for Pb and Cu, q=3 for M=Ce). In the most binary systems, a wide difference between the calculated values of the melting enthalpies of these polyphosphates and the measured ones determined from the DTA curves, was observed. This difference is probably due to the existence of some molecular associations in the liquid phase. The enthalpy of fusion of each terminal phase was then recalculated on the assumption that the liquid contains a molecular association of the type of M pn I Mn(PO3)n(q+p) in the region of the diagram rich in M I PO3 or a molecular association of the type of M n IMnp(PO3)n(qp+1) in the region rich in M(PO3)q (q=2 for Pb and Cu, q=3 for M=Ce). In this case, the obtained values are in good agreement with experimental determinations.
C. Marhag, D. Ben Hassen-Chehimi and H. Said, Journal of Thermal Analysis and Calorimetry 86 (2006) 249-254

E0122 – Characterisation of antibacterial copper releasing degradable phosphate glass fibres

Phosphate-based glass fibres (PGF) of the general formula Na2O-CaO-P2O5 are degradable in an aqueous environment, and therefore can function as antibacterial delivery systems through the inclusion of ions such as copper. In this study, PGF with varying amounts of copper oxide (CuO) were developed for potential uses in wound healing applications. PGF with 0, 1, 5 and 10mol% CuO were produced with different diameters and characterised in terms of structural and antibacterial properties. The effect of CuO and fibre pulling speed on the glass properties were investigated using rapid differential scanning calorimetry, differential thermal analysis and X-ray diffraction. The effect of two fibre diameters on short-term (3 h) attachment and killing against Staphylococcus epidermidis were investigated and were related to their rate of degradation in deionised water, as well as copper ion release measured using ion chromatography. Thermal analysis showed that there was a significant increase in the PGF glass transition temperature as the CuO content increased. There was a significant decrease in the rate of degradation with increasing CuO content and an increase in fibre diameter. Over 6 h, both the amount and rate of copper ions released increased with CuO content, as well as a reduction in fibre diameter thus increasing the surface area to volume ratio. There was a decrease in the number of viable staphylococci both attached to the CuOcontaining fibres and in the surrounding environment.
E.A. Abou Neel, I. Ahmed, J. Pratten, S.N. Nazhat, J.C. Knowles, Biomaterials 26 (2005) 2247-2254

E0121 – Nominal vs. actual stoichiometries in Al-doped NASICONs: A study of the Na1.4Al0.4M1.6(PO4)3 (M=Ge, Sn, Ti, Hf, Zr) family

Nominal Na1.4Al0.4M1.6(PO4)3 (M=Ge, Sn, Ti, Hf, Zr) NASICON compounds have been prepared as polycrystalline powders. Rietveld analysis of X-ray and neutron diffraction patterns showed that M=Ge and Sn samples crystallize in the R3¯ space group (s.g.) and that M=Ti, Hf, Zr compositions crystallize in the R3¯c s.g. Data analyses indicated that aluminum contents into the main NASICON phases are always smaller than the nominal ones. 27Al, 31P and 23Na magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies have been used to deduce aluminum contents and local atomic environments. In samples with high aluminum contents, M=Ge, Sn and Ti, electrical conductivity has been deduced from impedance spectroscopy data. The titanium sample incorporates the maximum aluminum content and displays the lowest activation energy, 0.52(1) eV, and the highest conductivity, rT(400 K)=1.5(3) 10 5 S cm 1. The influence of structural parameters on conductivity values has been analyzed with the bond valence sum method. With this technique, the most probable conduction pathways in Na1+xAlxTi2 x(PO4)3 and Na1+xInxZr2 x(PO4)3 samples have also been deduced.
P. Maldonado-Manso, M.A.G. Aranda, S. Bruque, J. Sanz, E.R. Losilla, Solid State Ionics 176 (2005) 1613 - 1625

E0120 – Crystal structures of Rb2U2O7 and Rb8U9O31, a new layered rubidium uranate

Two alkali metal uranates Rb2U2O7 and Rb8U9O31 have been synthesized by solid state reaction at high temperature and their crystal structures determined from single crystal X-ray diffraction data, collected with a three circles Brucker SMART diffractometer equipped by Mo(Ka) radiation and a charge-coupled device (CCD) detector. Their structures were solved using direct methods and Fourier difference techniques and refined by a least-square method on the basis of F2 for all unique reflections, with R1 = 0,043 for 53 parameters and 746 independent reflections with I>2?(I) for Rb2U2O7, monoclinic symmetry, space group P21/c, a = 7,323(2) Å, b = 8,004(3) Å, c = 6,950(2) Å, beta = 108,81(1)°, pmes = 6,56(3) g/cm3, pcal = 6,54(2) g/cm3, Z = 2 and R1 = 0,036 for 141 parameters and 2065 independent reflections with I>2?(I) for Rb8U9O31, orthorhombic, space group Pbna, a = 6,9925(9) Å, b = 14,288(2) Å, c = 34,062(5) Å, pmes = 6,47(3) g/cm3, pcal = 6,48(2) g/cm3, Z = 4. The Rb2U2O7 structure presents a strong analogy with that of K2U2O7 and can be described by layers of distorted UO2(O4) octahedra built from dimeric units of edge shared octahedra further linked together by opposite corners. In Rb8U9O31 puckered layers are formed by the association of two different uranium polyhedra, pentagonal bipyramids and distorted octahedra. The structure of Rb8U9O31 is built from a regular succession of 1[U4O14] 4- infinite ribbons similar to those observed in diuranates M2U2O7 (MQK, Rb) and infinite three polyhedra wide ribbons 1[U5O21] 12- , to create an original undulated sheets 2[U9O31] 8- . For both compounds Rb+ ions occupy the interlayer space and exhibit comparable mobility with conductivity measurements indicating an Arrhenius-type behavior.
S. Yagoubi, S. Obbade, C. Dion, F. Abraham, Journal of Solid State Chemistry 178 (2005) 3218-32

E0119 – Crystallization in the Na2O-CaO-Al2O3-SiO2-(LiF) glass compositions

Spodumene-nepheline glass-ceramics was prepared from Na2O-CaO-Al2O3-SiO2 glass compositions. Addition of LiF changes the course of the reaction toward the formation of beta-spodumene together with nepheline. The crystallization of beta-spodumene strongly reduce
E.M.A. Hamzawy, E.M. El-Meliegy, Ceramics International 33 (2007) 227-231

E0118 – A comparative study of the dehydroxylation process in untreated and hydrazine-deintercalated dickite

A dickite from Tarifa (Spain) was used to study the influence of the intercalation and the later deintercalation of hydrazine on the dehydroxylation process. The dehydroxylation of the untreated dickite occurs through three overlapping endothermic stages whose DTA peaks are centred at 586, 657 and 676°C. These endothermic effects correspond, respectively, to the loss of the inner-surface, the inner hydroxyl groups, and the loss of the water molecules, product of dehydroxylation process, which has been trapped in the framework of the dehydroxylated dickite. The intercalation of hydrazine in the interlayer space of dickite and the later deintercalation affect the dehydroxylation process. It occurs through only two endothermic stages which DTA peaks are centred at 575 and 650°C. The first corresponds to the simultaneous loss of both the inner and the inner-surface hydroxyl groups, whereas the second one is analogous to that at 676°C observed in the DTA curve of untreated dickite. These effects appear shifted to lower temperatures compared to those observed in the untreated dickite.
F. Franco and M.D. Ruiz Cruz, Journal of Thermal Analysis and Calorimetry 85 (2006) 369-375

E0109 – DSC Study of Y(a)Ba(b)Cu(c)O(7-d) homogeneity in the region 1050-1300K

Phase transitions of the compositions Y1±xBa2±yCu3±zO72212; (x,y=0-0.2;z=0-0.5; step 0.1) were studied by DSC in argon atmosphere in the temperature range 1050-1300 K. The formation of three polymorphous modifications of the 123 phase was observed. The solubilities of yttrium, barium and copper oxides in every modification were determined. TheT-x-y phase microdiagram for the 123 phase was mapped out.
K.S. Gavrichev, A.V. Khoroshilov, G.D. Nipan and P. Manca, Journal of Thermal Analysis and Calorimetry 48 (1997) 1039-1050

E0108 – Determination of phase diagrams by heat evaluation from DTA.

Basing on a quantitative analysis of DTA heat flow measurements the compositions of eutectic and peritectic reactions in complicated systems can be sensitively determined. In addition to the conventionally used DTA onset temperatures, the quantitative analysis of the corresponding heat flows provides important further information which significantly improve the determination of phase relations in complicated systems. The general concept is demonstrated for simple model systems. The sensitivity of detection and the separability of the DTA events will be discussed in detail. The applicability of the method is proved for two complicated examples from the Y---Ba---Cu---O system: (1) the quasibinary section YBa2Cu3O7 - delta---BaCuO2 and (2) the ternary eutectics YBa2Cu3O7 - delta---bBaCuO2---bCuO.
U. Wiesner, W. Bieger and G. Krabbes, Thermochimica Acta 290 (1996) 115-121

E0099 – Bi, Pb(2212) and Bi(2223) formation in the Bi-Pb-Sr-Ca-Cu-O system

A new route has been found for producing the Bi2Sr2CaCu2Oy, phase with Pb substituted for part of the Bi (denoted Bi,Pb(2212)). By this novel route, Bi,Pb(2212) has been prepared in air at 860 degrees C. For comparison, this phase has also been prepared in argon at 740 degrees C by the previously known route. Bi,Pb(2212) transforms from a tetragonal to an orthorhombic structure as the Pb content grows. Once this phase was obtained with a nominal composition of Bi(2-x)PbxSr2CaCu2Oy, with Pb contents x=0, 0.2, 0.4 and 0.6, the Bi(2223) phase was formed starting from Bi(2212) and Bi,Pb(2212). Single-phase samples were obtained after two heat treatments at 849 degrees C with Bi,Pb(2212) and a proportion of Pb of x=0.4. This proportion corresponds to the one used previously by the authors to obtain high critical current carrying tapes in Ag-clad Bi(2223) tapes.
A. Jeremie, K. Alami-Yadri, J-C. Grivel and R. Flükiger, Superconductor Science and Technology 6 (1993) 730-735

E0096 – Thermal analysis of new glass ceramic composite tapes and their components

Glass ceramic tapes prepared from various AlN, glass and organic binders were studied by simultaneous TG-DTA. Thermooxidative decomposition of polymeric binder, dehydration, oxidation of residual carbon, glass crystallization and oxidation of AlN were detected and evaluated. Results are compared with those obtained with the pure components AlN and glass. The rate of oxidation of various AlN charges at> 800°C in an air flow depends on their specific surface and eventual special (antihydrolytic) coating. In the ceramic composite the oxidation of AlN is much slower than in free AlN powder because of the embedding in the glass matrix. The glass exhibits crystallization to cordierite, the crystallization rate and final crystallinity depending on the P2O5 and B2O3 contents and the particle size of the glass. In the composite the crystallization of the glass component is accelerated and proceeds to a higher degree owing to the smaller particle size and to interactions between glass and filler. Grinding of the ceramic raw mix results in additional adsorption of moisture.
D. Schultze, W. Schiller and E. Schiller, Thermochimica Acta 246 (1994) 81-97

E0080 – Reaction between carbon fibres and molten silicon: heat determination using DTA

The highly exothermic reaction between carbon fibres and molten silicon, which is the basis of SiC--Si composite production, was investigated using a Setararn 2000 K thermoanalyser. DTA curves were recorded in 1.3 Pa vacuum and up to 1770 K, i.e. under the conditions of composite production. The results allowed calculation of the heat of the reaction, which ranged from 91 to 115 k J/tool.
M. Pyzalski, J. Bialoskorski and E. Walasek, Journal of Thermal Analysis 31 (1986) 1193-1196

E0079 – Studies of the reaction between the amorphous carbon and silicon

The kinetic parameters and the mechanism of reaction carbon black-silicon was studied by DTA, QXRD and microscopic methods. The possibility of SiC micropowders production at temperatures below the melting point of silicon was proved.
J. Bialoskorski, M. Pyzalski and E. Walasek, Journal of Thermal Analysis 36 (1990) 2033-2036

E0077 – Heats and entropies of fusion of ABC2 chalcopyrite semiconductors

Using quantitative DTA the melting temperatures and the enthalpies of fusion of some A(I)B(III)C(VI), and A(II)B(IV)C(V), compoundsare measured. The entropies of fusion are calculated and discussed in terms of the dielectric theory, and with regard to the structure of the liquid phase.
G. Kuhn, W. Moller and W. Engel, Thermochimica Acta 78 (1984) 129-134

E0076 – Phase interactions in silicon carbide reinforced composites.

Y. Bienvenu, J.C. Flour, Y. Favry, A.R. Bunsell, 7th International Conference "The materials revolution through the 90's", Paper 34

B3299 – Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared by sol–gel method

We have studied the structural and optical properties of thin films of TiO2, doped with 5% ZrO2 and deposited on glass substrate (by the sol–gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450 °C) and for various layer thicknesses (63–286 nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62–2.29 and the porosity is in the range of 0.21–0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO2, doped with 5% ZrO2, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm grains). However, the undoped TiO2 exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58–20.56 nm).
H. Bensouyad, H. Sedrati, H. Dehdouh, M. Brahimi, F. Abbas, H. Akkari, R. Bensaha, Thin Solid Films 519 (2010) 96–100

B3297 – Structural evidence for the nonmonotonic trend of TC in tetragonal PbTiO3ABiScO3 solid solutions

High-T C piezoelectric(1?x)PbTiO 3 ?xBiScO 3 shows a nonmonotonic trend of T C in the tetragonal phase with respect to content of BiScO 3 . To understand this behavior, the structure of (1?x)PbTiO 3 ?xBiScO 3 solid solutions is studied by means of neutronpowderdiffraction. The cation displacements of Pb/Bi and Ti/Sc exhibit a coupling property and a different impact by the substitution content of BiScO 3 . Its nonmonotonic trend of T C is quantitatively related to the calculated spontaneous polarization in the whole tetragonal range. The unique role of Bi-substitution not only contributes to enhance the component of polarization of Pb/Bi but also to increase the T C .
Jun Chen, Krishna Nittala, Jacob L. Jones, Penghao Hu, Xianran Xing, Applied Physics Letters 96, 252908 2010

B3262 – Determination of the thermodynamic stability of TiB2

The standard free energy of formation of titanium boride (TiB2) was measured by the Electro Motive Force (EMF) method (by using yttria doped thoria (YDT) as the solid electrolyte). Two galvanic cells viz. Cell (I): Pt, TiB2 (s), TiO2 (s), B (s) |YDT| NiO (s), Ni (s), Pt and cell (II): Pt, TiB2 (s), TiO2 (s), B (s) |YDT| FeO (s), Fe (s), Pt were constructed in order to determine the ?fG° of TiB2. Enthalpy increments on TiB2 were measured by using inverse drop calorimetry over the temperature range 583–1769 K. The heat capacity, entropy and the free energy function have been derived from these experimental data in the temperature range 298–1800 K. The mean value of the standard enthalpy of formation of TiB2 ( ?TiB2?) was obtained by combining these ?fG° values and the free energy functions of TiB2 derived from the drop calorimetry data. The mean values of ?TiB2? derived from the ?fG° data obtained from cell I and II were ?322 ± 1.2 kJ mol?1 and ?323.3 ± 2.1 kJ mol?1, respectively. These values were found to be in very good agreement with the assessed data.
Ashish Jain, R. Pankajavalli, S. Anthonysamy, K. Ananthasivan, R. Babu, V. Ganesan, G.S. Gupta, Journal of Alloys and Compounds 491 (2010) 747–752

B3246 – Influence of residual stresses and grain size on the spinodal decomposition of metastable Ti1?xAlxN coatings

At elevated temperatures, the metastable Ti1 ? xAlxN solid solution decomposes in cubic AlN and cubic TiN. Within this work, the effect of residual stresses on the decomposition of sputtered Ti1 ? xAlxN coatings was investigated. Using different bias voltages, a series of Ti1 ? xAlxN coatings (x = 0.63) with stresses ranging from + 630 to ? 2500 MPa was synthesized on Si (100) substrates. Vacuum annealing treatments and subsequent X-ray diffraction measurements showed that tensile stresses foster the formation of more volume consuming cubic TiN domains, while compressive stresses promote the formation of smaller cubic AlN domains. The influence of the grain size has been considered by investigations of free standing films using differential scanning calorimetry. Smaller grains lead to faster decomposition and earlier precipitation of wurtzite AlN.
N. Schalk, C. Mitterer, J. Keckes, M. Penoy, C. Michotte, Surface & Coatings Technology 209 (2012) 190–196

B3232 – Numerical simulation of the cooling-down of high-zirconia fused-cast refractories

This study concerns high zirconia fused-cast refractories used in the glass industry. In situ temperature measurements have been performed in the casting structure during an actual casting of a tile. A two-dimensional mesh of the casting structure has been developed so as to perform numerical simulations. From temperature recordings, an interfacial heat transfer coefficient between the tile and the graphite mould has been determined, by an inverse method, by fitting the calculated temperatures with those measured. A similar procedure allowed the thermal conductivity and the heat capacity of the surrounding insulating medium to be determined. Then, the numerical model allowed the evolution of the temperature field, within the tile, to be determined. The influences of different parameters (mould thickness and thermal properties of the annealing medium) have been numerically tested, by comparison with the cooling-down kinetics of the tile
Laetitia Petroni, Michel Boussuge, David Ryckelynck, Journal of the European Ceramic Society 32 (2012) 3941–3947

B3186 – Phase equilibrium of Bi2O3–Fe2O3 pseudo-binary system and growth of BiFeO3 single crystal

Thermodynamic decomposition of BiFeO3 (BFO) powder has been investigated and its peritectic transition temperature was determined to be 852±5 °C. Other typical characteristic temperatures in Bi2O3–Fe2O3 pseudo-binary phase diagram were reevaluated with high-purity starting materials. Based on the precision knowledge of improved Bi2O3–Fe2O3 pseudo-binary phase diagram, 1–2 mm sized single crystals BFO have been grown and characterized, showing ferroelectric transition temperature near 825 °C and remanent polarization about 70 ?C/cm2 along its polar axis.
J. Lu, L.J.Qiao, P.Z.Fu, Y.C.Wu, Journal of Crystal Growth 318 (2011) 936–941

B3184 – A study of electroless copper–phosphorus coatings with the addition of silicon carbide (SiC) and graphite (Cg) particles

Copper composite coating with graphite (Cg) and/or silicon carbide (SiC) particles were deposited by electroless plating. The surface morphology of the coatings that were analysed using scanning electron microscopy (SEM) showed that Cu particles were uniformly distributed. The obtained coating thickness was approximately ± 5 ?m. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were used to characterise the structure and to study the phase transition of the coatings, respectively. Phases such as Cu, Cu2O, Cu3P, Cu3Si, SiC and Cg were observed from X-ray diffraction patterns and the presence of Cu2O, Cu3P and Cu3Si was confirmed by differential scanning calorimetry (DSC) studies. The results demonstrated that SiC and Cg particles have little influence on the phase transition of the coating. The hardness and wear resistance of Cu–P composite coatings were improved with the incorporation of SiC particles. The friction coefficient of Cu–P composite coatings decreased with the incorporation of Cg particles. Atomic force microscopy (AFM) results of coatings showed that the roughness of the coatings increased with the incorporation of SiC to the Cu–P coatings and decreased with the incorporation of Cg. Cu–P–Cg–SiC composite coatings showed a moderate roughness, hardness between Cu–P–SiC and Cu–P–Cg coatings, had low friction and good anti-wear properties. The anti corrosion resistance of the electroless Cu–P composite coatings on carbon steel were studied in 3.5% NaCl and 1 M HCl solutions by the potentiodynamic polarisation technique. The study revealed that the corrosion resistance increased with the incorporation of SiC particles in the Cu–P and Cu–P–Cg matrix but reduced with the incorporation of graphite.
Soheila Faraji, Afidah Abdul Rahim, Norita Mohamed, Coswald Stephen Sipaut, Surface & Coatings Technology 206 (2011) 1259–1268

B3182 – Preparation and characterization of nanocomposite, silica aerogel, activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET). In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1 g at 60 C temperature. Subsequently, the equilibrium was achieved for Cd with 120 min of contact time.
M.H. Givianrad, M. Rabani, M. Saber-Tehrani, P. Aberoomand-Azar, M. Hosseini Sabzevari, Journal of Saudi Chemical Society (2013) 17, 329–335

B3169 – Cu22Bi12S21Cl16—A mixed conductor with fast one-dimensional copper(I) ion transport

Melting reactions of Cu, CuCl, S, and Bi2S3 yield black, shiny needles of Cu22(1)Bi12S21(1)Cl16(1). The compound decomposes peritectically at 649(5) K. Oxidation state +I of the copper atoms is supported by Cu–K-XANES. The compound crystallizes in the hexagonal space group P6/m with a=2116.7(7) pm and c=395.17(5) pm. Seven anions coordinate each of the two independent bismuth cations in the shape of mono-capped trigonal prisms. These polyhedra share edges and faces to form trigonal and hexagonal tubes running along [0 0 1]. The hexagonal tubes are centered by chloride ions, which are surrounded by disordered copper cations. The majority of copper cations are distributed over numerous sites between the tubes. The Joint Probability Density Function (JPDF) reveals a continuous pathway along [0 0 1]. The high mobility of the copper cations along [0 0 1] was demonstrated by impedance spectroscopy and DC polarization measurements on single crystals. The ionic conductivity at 450 K is about ?ion=0.06 S cm?1, and the activation energy for Cu+ ion conduction is Ea=0.44 eV. The chemical diffusion coefficient of copper is in the order of Dcu?=1019 cm?3 at 420 K. The electronic band gap (p-type conductor) was determined as Eg=0.06 eV. At room temperature the thermal conductivity of a pressed pellet is about ?=0.3 W K?1 m?1 and the Seebeck coefficient is S=43 ?V K?1.
Andreas Heerwig, Rotraut Merkle, Joachim Maier, Michael Ruck, Journal of Solid State Chemistry 184 (2011) 191–198

B3165 – Aging and thermal expansion behavior of Si3N4p/2024Al composite fabricated by pressure infiltration method

The aging and thermal expansion behaviors of Si3N4p/2024Al composite fabricated by pressure infiltration method were investigated. The peak-aging time and peak hardness both decrease with the increase of aging temperature for both the 2024Al alloy and Si3N4p/2024Al composite. The calculated activation energies of s? (precursors of the Al2MgCu) phase indicate that the precipitation of s? phase in Si3N4p/2024Al composite occurs easily than in 2024Al alloy. The presence of Si3N4 particles does not alter precipitation sequence, but accelerates the process of aging precipitation in Si3N4p/2024Al composite. The experimental coefficient of thermal expansion (CTE) of Si3N4p/2024Al composite bellow 100°C is more close to the average value of the Kerner model (upper bound Schapery model) and lower bound Schapery model. Aging treated Si3N4p/2024Al composite presents the best dimensional stability due to low internal stress and strong pining effect on dislocations from fine dispersed precipitates (Al2MgCu) and high density tangled dislocations. The good mechanical properties, compatible CTE with steel and high dimensional stability make Si3N4p/2024Al composite very competitive for application in the inertial guidance field.
Chen Guo-qing, Yang Wen-shu, Ma Kang, Murid Hussain, Jiang Long-tao, Wu Gao-hui, Transactions of Nonferrous Metals Society of China, Volume 21, Supplement 2, August 2011, Pages s262–s273

B3152 – The Lu–Ru–O System: Thermodynamic properties and impedance measurements of the pyrochlore Lu2Ru2O7(s)

The Gibbs free energy of formation of Lu2Ru2O7(s) has been determined using solid-state electrochemical technique employing oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured: Cell:(?)Pt/{Lu2O3(s)+Lu2Ru2O7(s)+Ru(s)}//CSZ//O2(p(O2)=21.21 kPa)/Pt(+)Cell:(?)Pt/Lu2O3s+Lu2Ru2O7s+Rus//CSZ//O2pO2=21.21 kPa/Pt+ The Gibbs free energy of formation of Lu2Ru2O7(s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be represented by: {f?G°(Lu2Ru2O7,s)/(kJ·mol?1)±2.7}=?2513.7+0.6265·(T/K);943.9£T/K£1230).{?fG°Lu2Ru2O7,s/kJ·mol?1±2.7}=?2513.7+0.6265·T/K;943.9£T/K£1230). Standard molar heat capacity C°p,m(T) of Lu2Ru2O7(s), was measured using a heat flux type differential scanning calorimeter (DSC) in two different temperature ranges, from 127 K to 299 K and 307 K to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: C°p,m(Lu2Ru2O7(s)(J.K?1·mol?1)=294.535+2.0·10?4T(K)?49.00688·105/T2(K).C°p,m(Lu2Ru2O7sJ.K?1·mol?1=294.535+2.0·10?4TK?49.00688·105/T2K. The second law method gave the value of standard enthalpy of formation and entropy, of the compound from elements at 298.15 K. An oxygen potential diagram for the Lu–Ru–O system was computed based on the thermodynamic data obtained. Impedance measurements on Lu2Ru2O7(s), suggests a semiconductor like behavior with low activation energy.
Aparna Banerjee, R. Mishra, Ziley Singh, Solid State Ionics 201 (2011) 42–48

B3147 – Annealing temperature effect on the properties of mercury-doped TiO2 films prepared by sol–gel dip-coating technique

This work presents the annealing temperature effect on the properties of mercury (Hg)-doped titanium dioxide (TiO2). Thin films and polycrystalline powders have been prepared by sol–gel process. The structure, surface morphology and optical properties, as a function of the annealing temperature, have been studied by atomic force microscopy (AFM), Raman, reflectance and ellipsometric spectroscopies. In order to determine the transformation points, we have analyzed the xerogel-obtained powder by differential scanning calorimetry (DSC). Raman spectroscopy shows the crystalline anatase and rutile phases for the films annealed at 400 °C and 1000 °C respectively. The AFM surface morphology results indicate that the particle size increases from 14 to 57 nm by increasing the annealing temperature. The complex index and the optical band gap (Eg) of the films were determined by the spectroscopic ellipsometry analysis. We have found that the optical band gap decreases by increasing the annealing temperature.
R. Mechiakh, N. Ben Sedrine, M. Karyaoui, R. Chtourou, Applied Surface Science 257 (2011) 5529–5534

B3130 – Effect of additional B-site transition metal doping on oxygen transport and activation characteristics in La0.6Sr0.4(Co0.18Fe0.72X0.1)O3?? (where X = Zn, Ni or Cu) perovskite oxides

The bulk structure, surface characteristics and catalytic properties of perovskite-type oxides with the formula La0.6Sr0.4(Co0.18Fe0.72X0.1)O3?? with X = Zn, Ni and Cu have been investigated. With additional B-site doping with divalent cations, the oxygen vacancy generation properties were significantly enhanced, while still maintaining a stable perovskite structure. The Zn-doped sample showed the best performance and was further characterized for surface structure and properties. CO2 TPD and methane oxidation experiments were conducted to gauge the oxygen activation and oxygen mobility and the Zn-doped catalyst showed improved performance over the baseline La0.6Sr0.4Co0.2Fe0.8O3?? catalyst, making it a potential SOFC cathode catalyst.
Nandita Lakshminarayanan, Hyunkyu Choi, John N. Kuhn, Umit S. Ozkan, Applied Catalysis B: Environmental 103 (2011) 318–325

B3129 – Variation of structure and properties of La1?xSrxCo0.2Fe0.8O(3??) with Sr content: Implications for oxidation activity

The bulk structure, surface characteristics and catalytic properties of Fe-based perovskite-type oxides with the formula La1-xSrxCo0.2Fe0.8O(3??) for x=0.2. 0.4, 0.6 and 0.8 have been investigated as potential anode catalysts for solid oxide fuel cells. The properties were found to strongly depend upon Sr-content, temperature, and environment. The bulk structure shifted towards being oxygen deficient and cubic under atmospheric conditions as the Sr content increased. The oxygen activation was found to be a strong function of Sr content with the catalysts being more active and having a lower activation energy for Sr-rich La1-xSrxCo0.2Fe0.8O3-delta. The materials showed good activity for methane oxidation forming only complete oxidation products and showing no propensity to coke formation, making them a stable potential anode catalyst for SOFCs
Nandita Lakshminarayanan, John N. Kuhn, Hyunkyu Choi, Jean-Marc M. Millet, Umit S. Ozkan, Journal of Molecular Catalysis A: Chemical 336 (2011) 23–33

B3115 – Ferroelectric electrocaloric conversion in 0.75(PbMg1/3Nb2/3O3)–0.25(PbTiO3) ceramics

This paper presents electrocaloric measurements on 0.75(PbMg1/3Nb2/3O3)–0.25(PbTiO3) ceramics. Reversible heat exchanged up to 0.15?J?g?1 with an applied field of 1.35?kV?mm?1 was obtained. The interpretation of this observation is based on direct polarization measurements. Starting from the integration along the electric field of the derivative of the polarization versus temperature, it was possible to predict the heat upon a decrease in electric field for values up to 3?kV?mm?1. However the simulations differ from the experiments and the discrepancy is believed to be due to hysteresis in ferroelectric materials. Finally a practical limit of the use of ferroelectric 0.75(PbMg1/3Nb2/3O3)–0.25(PbTiO3) ceramics is evidenced through electric conductivity appearance when the electrothermal conversion is very high.
Daniel Guyomar, Gael Sebald, Benoit Guiffard, Laurence Seveyrat, J. Phys. D: Appl. Phys. 39 (2006) 4491–4496

B3114 – Electrocaloric properties of high dielectric constant ferroelectric ceramics

In the last two decades, the electrocaloric (EC) effect which is associated to the temperature (?) dependence of the macroscopic polarization P(E, ?) under electric field E has been spasmodically studied in ferroelectric materials in order to find an alternative to the classical refrigeratory devices using freon. Basically, large electrocaloric temperature variation ?T originates from electric field-induced phase transition at the Curie temperature, but temperature changes of the sample are difficult to measure and depend on the experimental conditions. In this paper, the electrocaloric effect has been quantified directly and precisely by measuring the thermal energy exchanged under isothermal conditions using a modified Differential Scanning Calorimetry (DSC) apparatus. The DSC technique allowed to compare the EC properties of high-dielectric-constant (?) ceramics in the vicinity of ferroelectric–paraelectric phase transition. The measurements were also simulated starting from polarization versus electric field hysteresis loops for different temperatures. It is shown excellent agreement between simulations and direct DSC measurements, except in a limited temperature range where the hysteresis of the polarization versus temperature is high.
Gaël Sebald, Sébastien Pruvost, Laurence Seveyrat, Laurent Lebrun, Daniel Guyomar, Benoît Guiffard, Journal of the European Ceramic Society 27 (2007) 4021–4024

B3113 – Electrocaloric and pyroelectric properties of 0.75Pb„Mg1/3Nb2/3…O3–0.25PbTiO3 single crystals

Pyroelectric and electrocaloric characterization has been determined for 0.75Pb(Mg1/3Nb2/3)O3–0.25PbTiO3 relaxor based single crystal and ceramic. Differential scanning calorimetry was used for measuring the electrocaloric response for different electric fields in the vicinity of the Curie temperature. For both ceramic and crystals the maximum activity is found to be around the transition temperature. On the other hand hysteresis loops for different temperatures were used to predict the electrocaloric effect with very good qualitative agreements with direct measurements. Pyroelectric coefficient is found to be much larger for ?111? single crystals reaching 1300×10?6?C?m?2?K?1 whereas the ceramic reaches only 750×10?6?C?m?2?K?1. Higher pyroelectric coefficient and lower dielectric permittivity lead to outstanding figures of merits for sensors and energy harvesting, with a gain of 260% for voltage responsivity and more than 500% for energy harvesting. Although having a much larger pyroelectric activity, the electrocaloric effect is about the same for crystals and ceramics—around 0.40?J/g for 2.5?kV/mm electric field step. This result is interpreted by the decrease of the pyroelectric coefficient for high electric field. The electrocaloric activity is in fact limited by the saturation polarization and difference between Curie transition temperature and the working temperature. Those two parameters are very similar for crystals and ceramics. Single crystals are consequently very interesting materials in the framework of energy harvesting and sensor applications whereas no real improvement of performances can be expected for electrocaloric refrigeration devices.
Gael Sebald, Laurence Seveyrat, Daniel Guyomar, Laurent Lebrun, Benoit Guiffard, Sebastien Pruvost, Journal of Applied Physics 100, 124112 2006

B3055 – High-temperature ferroic phase transitions and paraelectric cubic phase in multiferroic Bi0.951dFe0.9Zr0.1O3

The temperature-dependent phase transitions of Bi(0.95+?)Fe0.9Zr0.1O3 have been studied using high temperature x-ray powder diffraction together with differential scanning calorimetry measurements. The results show that Bi(0.95+?)Fe0.9Zr0.1O3 undergoes two phase transitions at 815°C and 905°C before decomposition at 920°C. It appears that Zr-doping seems to stabilize the high temperature phases in such compound. Both the sharp contraction in the unit-cell volume and enthalpy thermal hysteresis demonstrate that the ferroelectric phase transition (? ? ?) at 815°C is of first order nature. In contrast, the highest (? ? ?) phase transition at 905°C appears to be a second-order-like one. The analysis of the diffraction pattern in addition to Rietveld refinement strongly suggests a cubic symmetry for ?-phase
Jie Wei, Raphael Haumont, Romain Jarrier, Patrick Berthet, Brahim Dkhil, J. Appl. Phys. 111, 114106 (2012)

B3002 – Surface studies of hydroxylated multi-wall carbon nanotubes

CVD grown MWCNTs, of typical diameter 5 to 50 nm and with approximately 15–20 concentric graphene layers in the multi-walls, have been surface functionalised using the Fenton hydroxylation reaction. HRTEM reveals little physical difference between the treated and untreated materials; images from both exhibit similar multi-wall structure and contain evidence for some low-level disruption of the very outermost layers. Raman spectra from the two types of nanotubes are almost identical displaying the disorder (D) peaks at approximately 1350 cm?1 and graphite (G) peaks at approximately 1580 cm?1, characteristic of graphene-based carbon materials, in approximately equal intensity ratios. Equilibrium adsorption data for nitrogen at 77 K leads to BET surface areas of 60.4 m2 g?1 for the untreated and 71.8 m2 g?1 for the hydroxylated samples; the increase in area being due to separation of the tube-bundles during functionalization. This is accompanied by a decrease in measured porosity, mostly at high relative pressures of nitrogen, i.e. where larger (meso 2–5 nm and macro >5 nm) pores are being filled, which is consistent with an attendant loss of inter-tube capillarity. X-ray photoelectron spectroscopy (XPS) shows that hydroxylation increases the nanotube surface oxygen level from 4.3 at.% to 22.3 at.%; chemical shift data indicate that approximately 75% of that oxygen is present as hydroxyl (–OH) groups. Water vapour adsorption by the hydroxylated surfaces leads to Type II isotherms which are characteristic of relatively high numbers of hydrogen bonding interactions compared to the untreated materials which exhibit Type III curves. This difference in polar surface energy is confirmed by calorimetric enthalpies of immersion in water which are ?54 mJ m?2 for the untreated and ?192 mJm?2 for the hydroxylated materials. The treated materials therefore have significantly increased water wettability/dispersivity and a greater potential for crosslinking with matrix compounds. The mechanism by which hydroxylation occurs i.e. free radical (OH•) attack and subsequent electrophilic addition at C C bonds in the graphene basal planes, is discussed.
Robert H. Bradley, Kelby Cassity, Rodney Andrews, Mark Meier, Susan Osbeck, Aurik Andreu, Colin Johnston, Alison Crossley, Applied Surface Science 258 (2012) 4835– 4843

B2949 – DSC investigation of nanocrystalline TiO2 powder

The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm) and low temperature (B200 C). The as-prepared samples were characterized with respect to their composition by ICP (inductive coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured TiO2 was compared with three commercial TiO2 samples. The sequence of brookite–anatase–rutile phase transformation in TiO2 samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported
Cornelia Marinescu, Ancuta Sofronia, Cristina Rusti, Roxana Piticescu, Viorel Badilita, Eugeniu Vasile, Radu Baies, Speranta Tanasescu, J Therm Anal Calorim (2011) 103, 49–57

B2922 – Synthetic conditions and their doping effect on ?-K2Bi8Se13

In this work the synthetic conditions for K2Bi8Se13 and their effect on its thermoelectric properties were investigated. K2Bi8Se13 was prepared as a single phase using K2Se and Bi2Se3 as starting materials in a furnace or via a reaction using direct flame, followed by remelting or annealing. Seebeck coefficient measurements showed that the doping level in the material is sensitive to the synthetic conditions. Higher synthesis temperatures aswell as the flame reaction technique followed by annealing gave more homogenous samples with higher Seebeck coefficient. IR optical spectroscopic measurements showed a wide range of doping level achieved among the different synthetic conditions. These findings suggest that synthetic conditions can act as a useful tool for the optimization of the thermoelectric properties of these materials.
Th. Kyratsi, I. Kika, E. Hatzikraniotis, K.M. Paraskevopoulos, K. Chrissafis, M.G. Kanatzidis, Journal of Alloys and Compounds 474 (2009) 351–357

B2913 – Correlation between structural and optical properties of TiO2:ZnO thin films prepared by sol–gel method

We have studied structural and optical properties of thin films of TiO2, doped with 5% ZnO and deposited on glass substrate (by the sol–gel method). Dipcoated thin films have been examined at different annealing temperatures (350–450 °C) and for various layer thicknesses (89–289 nm). Refractive index, porosity and energy band gap were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.97–2.44, the porosity is in the range of 0.07–0.46 and the energy band gap is in the range of 3.32–3.43. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO2, doped with 5% ZnO, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 20.23 nm grains). However, the undoped TiO2 exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range of 8.61–29.48 nm.
H. Bensouyad, D. Adnane, H. Dehdouh, B. Toubal, M. Brahimi, H. Sedrati, R. Bensaha, J Sol-Gel Sci Technol (2011) 59, 546–552

B2901 – System Zn–Rh–O: heat capacity and Gibbs free energy of formation using differential scanning calorimeter and electrochemical cell

The standard molar Gibbs free energy of formation of ZnRh2O4(s) has been determined using an oxide solid-state electrochemical cell wherein calcia-stabilized zirconia (CSZ) was used as an electrolyte. The electromotive force was measured in the temperature range from 943.9 to 1,114.2 K. The standard molar Gibbs energy of formation of ZnRh2O4(s) from elements in their standard state using the oxide electrochemical cell has been calculated. Standard molar heat capacity Cop,m(T) of ZnRh2O4(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges, from 127 to 299 and 307 to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression. The heat capacity of ZnRh2O4(s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K
Aparna Banerjee, Ziley Singh, J Solid State Electrochem (2009) 13, 1201–1207

B2900 – Thermodynamic studies on SrFe12O19(s), SrFe2O4(s), Sr2Fe2O5(s) and Sr3Fe2O6(s)

The citrate-nitrate gel combustion route was used to prepare SrFe2O4(s), Sr2Fe2O5(s) and Sr3Fe2O6(s) powders and the compounds were characterized by X-ray diffraction analysis. Different solid-state electrochemical cells were used for the measurement of emf as a function of temperature from 970 to 1151 K. The standard molar Gibbs energies of formation of these ternary oxides were calculated as a function of temperature from the emf data and are represented as ?fG°m (SrFe2O4, s, T)/kJ mol-1 (± 1.7) = -1494.8+0.3754 (T/K) (970? T/K? 1151). ?fG°m (Sr2Fe2O5, s, Tj/kJ mol-1 (±3.0) = -2119.3+0.4461 (T/K) (970 ? T/K? 1149). ?fG°m (Sr3Fe2O6, s, T)/kJmol-1 (±7.3) = -2719.8+0.4974(T/K) (969?T/K?1150). Standard molar heat capacities of these ternary oxides were determined from 310 to 820 K using a heat flux type differential scanning calorimeter (DSC). Based on second law analysis and using the thermodynamic database FactSage software, thermodynamic functions such as AfH°(298.15 K), S°(298.15K) S°(T), Cp°(T), H°(T), {H°(T)-H°(29&.15K)}, G°(T), free energy function (fef), ?fH°(T) and ?fG°(T) for these ternary oxides were also calculated from 298 to 1000 K.
S.K. Rakshit, S.C. Parida, S. Dash, Z. Singh, B.K. Sen, V. Venugopal, Journal of Solid State Chemistry 180 (2007) 523–532

B2899 – Thermochemical studies on SrFe12O19(s)

The citrate-nitrate gel combustion route was used to prepare SrFe12O19(s) powder sample and the compound was characterized by X-ray diffraction analysis. A solid-state electrochemical cell of the type: (-)Pt, O2(g)/ (CaO(s) + CaF2(s)}//CaF2(s)//(Srfe12O19(s) + SrF2(s) + Fe2O3(s) )}/O2(g), Pt(+) was used for the measurement of emf as a function of temperature from 984 to 1151 K. The standard molar Gibbs energy of formation of SrFe12O19(s) was calculated as a function of temperature from the emf data and is given by: ?fGom(SrFe12O19, , s, T)/kJ mol-1 (?1.3) = -5453.5 + 1.5267 x (TIK). Standard molar heat capacity of SrFe12O19(s) was determined in two different temperature ranges 130-325 K and 310-820 K using a heat flux type differential scanning calorimeter (DSC). A heat capacity anomaly was observed at 732 K, which has been attributed to the magnetic order-disorder transition from ferrimagnetic state to paramagnetic state. The standard molar enthalpy of formation, ?fHom[(298.15 K) and the standard molar entropy, Som(298.15 K) of SrFe12O19(s) were calculated by second law method and the values are -5545.2 kJ mol-1 and 633.1 J K-1 mol-1, respectively.
S.K. Rakshit, S.C. Parida, S. Dash, Z. Singh, R. Prasad, V. Venugopal, Materials Research Bulletin 40 (2005) 323–332

B2897 – Heat capacities, order–disorder transitions, and thermodynamic properties of rare-earth orthoferrites and rare-earth iron garnets

Rare-earth orthoferrites, RFeO3, and rare-earth iron garnets (RIGs) R3Fe5O12 (R=rare-earth elements) were prepared by citrate–nitrate gel combustion method and characterized by X-ray diffraction method. Isobaric molar heat capacities of these oxides were determined by using differential scanning calorimetry from 130 to 860 K. Order–disorder transition temperatures were determined from the heat capacity measurements. The Néel temperatures (TN) due to antiferromagentic to paramagnetic transitions in orthoferrites and the Curie temperatures (TC) due to ferrimagnetic to paramagnetic transitions in garnets were determined from the heat capacity data. Both TN and TC systematically decrease with increasing atomic number of R across the series. Lattice, electronic and magnetic contributions to the total heat capacity were calculated. Debye temperatures as a function of absolute temperature were calculated for these compounds. Thermodynamic functions like , , Ho, Go, , , , , and have been generated for the compounds RFeO3(s) and R3Fe5O12(s) based on the experimental data obtained in this study and the available data in the literature.
S.C. Parida , S.K. Rakshit, Ziley Singh, Journal of Solid State Chemistry 181 (2008) 101–121

B2895 – Thermodynamic studies on lithium ferrites

Thermodynamic studies on ternary oxides of Li–Fe–O systems were carried out using differential scanning calorimetry, Knudsen effusion mass spectrometry, and solid-state electrochemical technique based on fluoride electrolyte. Heat capacities of LiFe5O8(s) and LiFeO2(s) were determined in the temperature range 127–861 K using differential scanning calorimetry. Gibbs energies of formation of LiFe5O8(s) and LiFeO2(s) were determined using Knudsen effusion mass spectrometry and solid-state galvanic cell technique. The combined least squares fits can be represented as ?fGmo(LiFe5O8,s,T)/kJ mol?1 (±6)=?2341+0.6764(T/K) (588?T/K?971) ?fGmo(LiFeO2,s,T)/kJ mol?1 (±3)=?708+0.1656(T/K) (569?T/K?1021) The temperature independent term of the above equations represents ?fHom(Tav) and temperature dependent term represents negative change in entropy of the respective compounds. Thermodynamic analysis shows that LiFe5O8(s) is more stable compared to LiFeO2(s).
S.K. Rakshit, S.C.Parida, Y.P.Naik, Ziley Singh Chaudhary, V.Venugopal, Journal ofSolidStateChemistry184(2011)1186–1194

B2894 – Determination of thermodynamic properties of YRhO3(s) by solid-state electrochemical cell and differential scanning calorimeter

The standard molar Gibbs free energy of formation of YRhO3(s) has been determined using a solid-state electrochemical cell wherein calcia-stabilized zirconia was used as an electrolyte. The cell can be represented by: (-)Pt - Rh/[Y2O3(s) + YRhO3(s) + Rh(s)] //CSZ//O2(p(O2) = 21.21 kPa)/Pt - Rh(+). The electromotive force was measured in the temperature range from 920.0 to 1,197.3 K. The standard molar Gibbs energy of the formation of YRhO3(s) from elements in their standard state using this electrochemical cell has been calculated and can be represented by: ?fGof[YRhO3(s)]/kJ mol-1 (±1:61) = -!1,147.4 + 0.2815 T(K). Standard molar heat capacity Cop,m (T) of YRhO3(s) was measured using a heat flux-type differential scanning calorimeter in two different temperature ranges from 127 to 299 K and 305 to 646 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: Cop, (YRhO3,s,T) ( J K-1mol-1) = 109:838 + 23:318x10-3 T(K) -12.5964)x105/T2(K). (305
Aparna Banerjee, Ziley Singh, J Solid State Electrochem (2010) 14, 1227–1233

B2893 – Synergistic use of Knudsen effusion quadrupole mass spectrometry, solid-state galvanic cell and differential scanning calorimetry for thermodynamic studies on lithium aluminates

Three ternary oxides LiAl5O8(s), LiAlO2(s) and Li5AlO4(s) in the system Li–Al–O were prepared by solidstate reaction route and characterized by X-ray powder diffraction method. Equilibrium partial pressure of CO2(g) over the three-phase mixtures {LiAl5O8(s)+Li2CO3(s)+5Al2O3(s)}, {LiAl5O8(s)+5LiAlO2(s)+2Li2 CO3(s)} and {LiAlO2(s)+Li5AlO4(s)+2Li2CO3(s)} were measured using Knudsen effusion quadrupole mass spectrometry (KEQMS). Solid-state galvanic cell technique based on calcium fluoride electrolyte was used to determine the standard molar Gibbs energies of formations of these aluminates. The standard molar Gibbs energies of formation of these three aluminates calculated from KEQMS and galvanic cell measurements were in good agreement. Heat capacities of individual ternary oxides were measured from 127 to 868 K using differential scanning calorimetry. Thermodynamic tables representing the values of ?fH0(298.15 K), S0(298.15 K) S0(T), Cp 0 (T), H0(T), {H0(T)–H0(298.15 K)}, G0(T), ?fH0(T), ?fG0(T) and free energy function (fef) were constructed using second law analysis and FACTSAGE thermo-chemical database software.
S.K. Rakshit, Y.P. Naik, S.C. Parida, Smruti Dash, Ziley Singh, B.K. Sen, V. Venugopal, Journal of Solid State Chemistry 181 (2008) 1402– 1412

B2865 – A Thermoporometry Study of Fumed Silica/Aerogel Composites

The porous texture of fumed silica/aerogel composite materials is studied by thermoporometry. The effect of fumed silica (Aerosil) powder in aerogels, added during the sol-gel processing is investigated. The textural change due to the autoclave drying process as a function of the fumed silica/aerogel ratio of the systems is investigated. The meso- and macro porosity of the fumed silica/aerogel composites is mainly influenced by the ratio fumed silica/aerogel and only slightly by the autoclave drying process. Addition of fumed silica powder results in an increase of the mean pore radius of the system and in a decrease of the meso- and macro-pore volume. By contrast, the micro-porosity is hardly affected by the addition of the fumed silica powder; it is only influenced by the autoclave drying process.
M.J. Van Bommel, C.W. Den Engelsend, J.C. Van Miltenburg, Journal of Porous Materials 4, 143–150 (1997)

B2850 – Experimental Investigation of the Bi-Sb-Zn System: Study of the Isoplethic Sections Bi-SbZn, Bi-Sb3Zn4 and Bi-Sb2Zn3

The ceramics based on zinc oxide undergo doping on bismuth and antimony. Exploring the rich part of zinc in the Bi-Sb-Zn system is necessary to know the present phases. For this purpose, an experimental study was carried out by differential scanning calorimetry on alloys belonging to the isopleths Bi-SbZn, Bi-Sb3Zn4 and Bi-Sb2Zn3.
Malek Bouharkat, Fouzia Adjadj, Journal of Phase Equilibria and Diffusion Vol. 32 No. 4 2011

B2827 – Maps of Fe–Al phases formation kinetics parameters during isothermal sintering

The influence of technological parameters (compaction pressure and sintering temperature) on Fe–Al phase formation was investigated. The kinetics of phase transformation preceding and during an SHS reaction was studied in isothermal conditions by DSC using the JMA (Johnson–Mehl–Avrami) model. This model allowed us to determine basic kinetic parameters, including the Avrami exponent, which characterises the rate and manner of particular phase nucleation. The activation energy (Ea) of particular phase formation was determined by the Kissinger method. XRD analysis and SEM observations of sintered material showed that not only Fe2Al5 phase and low aluminium solid solution in iron but also aluminium rich FeAl2 and FeAl3 phases are formed during the sintering of an FeAl50 elementary powder mixture in isothermal conditions with an SHS reaction. The above conclusions were confirmed by ironbased solid solution lattice parameter studies and microhardness measurements.
Ewelina Pochec, Stanis?aw Józwiak, Krzysztof Karczewski, Zbigniew Bojar, Thermochimica Acta 545 (2012) 14– 19

B2714 – Study of the La2O3-Ga2O3 System by Experiment and Thermodynamic Calculations

Thermodynamic and phase diagram experimental data relevant to the La2O3-Ga2O3 system have been critically assessed. The system is characterized by the presence of two stoichiometric, congruently melting compounds LaGaO3 and La4Ga2O9, each occurring in two polymorphic modifications. A number of key experiments have been carried out to measure the heat capacity and to characterize phase transitions in both compounds as well as to determine the solubility of La in Ga2O3 and that of Ga in La2O3. These data were used together with information from the literature to generate self-consistent thermodynamic description of the La2O3-Ga2O3 system.
M. Zinkevich, S. Geupel, H. Nitsche, M. Ahrens, F. Aldinger, Journal of Phase Equilibria and Diffusion Vol. 25 No. 5 (2004)

B2705 – High temperature enthalpy, heat capacity and other thermodynamic functions of solid InN

The heat capacity and the heat content of indium nitride were measured by Calvet calorimetry (305–390 K) and by drop calorimetry (427–774 K). The temperature dependence of the heat capacity in the form Cpm = 43:886 + 8:194 x 10.-3 x T - 1:007 x 106 x T-2 + 8.353 x 107 x T-3(J K-1 mol-1) was derived by the least squares method from the experimental data. Furthermore, x the standard molar entropy S0m (298 K) = 42.51 J K-1 mol-1 was assessed taking into account the recently reported phonon density of states, low temperature Cpm and the current data. Thermodynamic functions calculated on the basis of our results and literature data on the heat of formation of InN are given.
J. Leitner, P. Mars?ka, D. Sedmidubsky, K. Ruzicka, Journal of Physics and Chemistry of Solids 65 (2004) 1127–1131

B2704 – Heat capacity, enthalpy and entropy of strontium niobates Sr2Nb10O27 and Sr5Nb4O15

Heat capacity and enthalpy increments of strontium niobates Sr2Nb10O27 (S2N5) and Sr5Nb4O15 (S5N2) were measured by the relaxation time method (2–275 K), DSC (253–353 K) and drop calorimetry (673–1371K). Temperature dependencies of the molar heat capacity in the form Cpm = 835 + 0.23 T – 14×106/T2 JK?1 mol?1 for S2N5 and Cpm = 511 + 0.14 T – 6.6×106/T2 JK?1 mol?1 for S5N2 were derived by the leastsquares method. The molar entropies at 298.15 K, Som (S2N5, 298.15 K) = 759.7 JK?1 mol?1 and Som (S5N2, 298.15 K) = 524.5 JK?1 mol?1,were evaluated from the lowtemperature heat capacity measurements.
J. Leitner, I. Sipula, K. Ruzicka, D. Sedmidubsky, P. Svobodad, Journal of Alloys and Compounds 481 (2009) 35–39

B2699 – Crystallization in the SiO2-Al2O3 System from Amorphous Powders

The crystallization of amorphous chemically homogeneous powders in the SiO2.Al2O3 system has been studied by differential scanning calorimetry and X-ray diffraction. Up to 1300?C only one exotherm has been observed. Only mullite crystallizes for compositions ?69 mol% Al2O3 and spinel for those ?80%. The crystallizations into mullite and spinel are sharp and exothermic, with an enthalpy of 250–300 J/g. The chemical composition of the crystallized mullite regularly increases from 68 to 76 mol% Al2O3 with increasing bulk composition from 60 to 75 mol% Al2O3.
I. Jaymes, A. Douy, M. Gervais, J.P. Coutures, Journal of Sol-Gel Science and Technology 8, 415–418 (1997)

B2698 – Phase Formation and Transformation in Alumina/YSZ Nanocomposite Coating Deposited by Suspension Plasma Spray Process

Suspension Plasma Spray process was used for deposition of pseudo-eutectic composition of alumina-yttria-stabilized zirconia as a potential thermal barrier coating using Mettech axial III torch. Processvariables including feed and plasma parameters were altered to find their effects on the formation of phases in the composite coating. The in-flight particle velocity was found to be the crucial parameter on phase formation in the resulting coatings. Low particle velocities below 650 m/s result in the formation of stable phases i.e., a-alumina and tetragonal zirconia. In contrast, high particle velocities more than 750 m/s favor the metastable c-alumina and cubic zirconia phases as dominant structures in as-deposited coatings. Accordingly, the plasma auxiliary gas and plasma power as influential parameters on the particle velocity were found to be reliable tools in controlling the resulting coating structure thus, the consequent properties. The noncrystalline portion of the coatings was also studied. It was revealed that upon heating, the amorphous phase prefers to crystallize into pre-existing crystalline phases in the as-deposited coating. Thus, the ultimate crystalline structure can be designed using the parameters that control the particle velocity during plasma spray coating.
F. Tarasi, M. Medraj, A. Dolatabadi, J. Oberste-Berghaus, and C. Moreau, Journal of Thermal Spray Technology, Volume 19(4) June 2010—787

B2697 – Spin-Reorientation Transition in TbCo5

Nearly single-phase samples of compound TbCo5+? (where ?= 0) are obtained and certified in the poly- and monocrystalline state. The latent heat is measured on these samples for the first time in the region of the spin-reorientation phase transition using differential scanning calorimetry. The latent heat of the transition is found to be 1.3 ± 0.2 kJ/kg. The experimental data are compared with the theoretical results obtained in the framework of the single-ion theory (QL= 1.1 kJ/kg). It is found that the discrepancy is insignificant to within the experimental error.
I.S. Tereshina, N. L. Korenovskii, G. S. Burkhanov, M. D. Kuz’min, K. P. Skokov, J. J. Melero, Journal of Experimental and Theoretical Physics, 2007, Vol. 105, No. 6, pp. 1230–1235

B2678 – Heat capacity, enthalpy and entropy of SrBi2O4 and Sr2Bi2O5

Heat capacity and enthalpy increments of ternary strontium bismuth(III) oxides SrBi2O4 and Sr2Bi2O5 were measured by the relaxation time method (2–210 K), DSC (253–352 K) and drop calorimetry (570–1072 K). Temperature dependencies of the molar heat capacity in the form Cpm = 161.97 + 45.936 ×10?3 T – 1.7862 ×106/T2 J K?1 mol?1 and Cpm = 197.48 + 87.463 ×10?3 T – 1.9282 ×106/T2 J K?1 mol?1 for SrBi2O4 and Sr2Bi2O5, respectively, were derived by the least-squares method from the experimental data. The molar entropies at 298.15 K, S?m(298.15 K) = 206.1±1.1 J K?1 mol?1 for SrBi2O4 and S?m(298.15 K) = 261.2±1.4 J K?1 mol?1 for Sr2Bi2O5, were evaluated from the low temperature heat capacity measurements.
J. Leitner, D. Sedmidubsky, K. Ruzickac, P. Svoboda, Thermochimica Acta 531 (2012) 60– 65

B2648 – Calorimetric Measurement of Surface and Interface Enthalpies of Yttria-Stabilized Zirconia (YSZ)

The surface and interface enthalpies of cubic stabilized zirconia solid solutions containing 8, 10, and 12 mol?% Y2O3 were determined by a combination of calorimetric, morphological, and structural analyses techniques. Nanocrystalline samples with several surface areas and degrees of agglomeration were synthesized by simultaneous precipitation and annealing at temperatures of 470?900 °C. Samples were characterized by X-ray diffraction and Raman spectroscopy. Surface areas were measured by N2 adsorption, and interface areas were estimated by comparing surface areas from N2 adsorption to those derived from an analysis of the crystallite sizes refined from X-ray diffraction data. Calorimetric measurements of heat of solution in a sodium molybdate melt, as a function of surface and interface areas, enabled us to experimentally derive trends in the surface and interface enthalpies of hydroxylated surfaces. Accounting for heats of water adsorption measured by microcalorimetry allowed us to obtain the surface enthalpies (energies) of the anhydrous surfaces at each composition. Average surface enthalpies were determined to increase with yttria content, from 0.85 ± 0.07 J/m2 (for 8 mol?% yttria) to 1.27 ± 0.08 J/m2 (for 12 mol?% yttria) for the hydrous surface and from 1.16 ± 0.08 J/m2 to 1.80 ± 0.10 J/m2 for the anhydrous surface. Interface enthalpies were determined to be in the range of 0.9 ± 0.5 J/m2 for all studied compositions. Comparisons with measured surface energies for pure ZrO2, and Y2O3 nanopowders and grain-boundary energies for YSZ dense nanoceramics are presented.
Gustavo C. C. Costa, Sergey V. Ushakov, Ricardo H. R. Castro, Alexandra Navrotsky, Reginaldo Muccillo, Chem. Mater., 2010, 22 (9) 2937–2945

B2442 – Calorimetric investigations on stoichiometric barium and uranium oxides

Heat capacities and enthalpy increments of barium uranates: BaU2O7(s), Ba2U3O11(s), Ba2.875UO5.875(s) and Ba3UO6(s) were measured using a differential scanning calorimeter and a high-temperature Calvet calorimeter. The heat capacities and enthalpy increments were measured in the temperature range 126–304 K and 299–1011 K, respectively. A set of self consistent thermodynamic functions such as entropy, Gibbs energy function, heat capacity and Gibbs energy and enthalpy of formation values for BaU2O7(s), Ba2U3O11(s), Ba2.875UO5.875(s) and Ba3UO6(s) have been computed for the first time using the data obtained in the present study and other available experimental data.
Smruti Dash, Ziley Singh, Journal of Nuclear Materials 404 (2010) 9–18

B2430 – The high temperature heat capacity of NpO2

LAPW electronic structure calculations within density functional theory.
O. Benes, P. Gotcu-Freis, F. Schwörer, R.J.M. Konings, Th. Fanghänel, J. Chem. Thermodynamics 43 (2011) 651–655

B2379 – Sugar cane bagasse fibres reinforced cement composites: Thermal considerations

This paper examines the thermal properties of cement composites reinforced with vegetable bagasse fibres (1.5% and 3% wrtc). Thermal properties have been correlated to macroscopic density and porosity in order to estimate thermal conductivity of fibres using a calculation inspired from the Maxwell–Eucken modelling. Experimental investigations reveal that adding retified bagasse fibres reduces composites thermal conductivity and yields a weaker specific heat in comparison with composites made with alkaline bagasse fibres. Moreover, the more the fibres, the lighter the specimen; lower its thermal conductivity and lower its specific heat. Thermal conductivity of alkaline fibres is lower than retified fibres one.
Cristel Onésippe, Nady Passe-Coutrin, Fernando Toro, Silvio Delvasto, Ketty Bilba, Marie-Ange Arsène, Composites: Part A 41 (2010) 549–556

B2264 – Dipolar-glass-like behaviour of 0.7PMN-0.3PZ ceramic

Relaxor ferroelectric behaviour has been observed for lead magnesium niobate-lead zirconate (0.7PMN-0.3PZ) ceramic. The freezing temperature obtained from fitting of dielectric data to the Vogel-Fulcher equation is very close to the dielectricmaximum temperature and to the temperature of collapse of remanant polarization. The temperature dependence of the spontaneous polarization follows a modified Neel's equation. Specific-heat measurement shows canonical glass-like behaviour, and the value of the glass-transition temperature is very close to the freezing temperature obtained from the Vogel-Fulcher equation. All the observations together indicate that 0.7PMN-0.3PZ ceramic behaves like a dipolar glass.
G. Singh, V.S. Tiwari, V.K. Wadhawan, Solid State Communications 129 (2004) 665-670

B2183 – Thermodynamic properties of quaternary oxides in the system Ba-La-Fe-O by differential scanning calorimetry and solid-state electrochemical cells

Two compounds, BaLa2Fe2O7(s) and BaLaFeO4(s) in the quaternary system Ba-La-Fe-O have been prepared by citrate-nitrate gel combustion route and characterized by X-ray diffraction analysis. Heat capacities of these two oxides were measured in the temperature range from 302 K to 832 K using a heat flux type differential scanning calorimeter. Two different types of solidstate electrochemical cells with CaF2 as the solid electrolyte were employed to measure the e.m.f. as a function of temperature. The standard molar Gibbs energy of formation of the above oxides was calculated as a function of temperature from the e.m.f. data. The standard molar enthalpy of formation at 298.15 K, ?fHm° (298.15 K) and the standard entropy Sm° (298.15 K), of these two oxides were calculated by second law method. The values of ?fHm° (298.15 K) and Sm° (298.15 K) obtained for BaLa2- Fe2O7(s) are: 3446.4 kJ.mol-1 and 246.6 J.K-1.mol-1 whereas those for BaLaFeO4(s) are: 2080.4 kJ.mol-1 and 95.0 J.K-1.mol-1, respectively.
S.C. Parida, S.K. Rakshit, S. Dash, Ziley Singh, R. Prasad, V. Venugopal, J. Chem. Thermodynamics 36 (2004) 911-917

B2092 – Effect of drying temperature on structure, phase transformation of sol-gel-derived lead zirconate titanate powders

Lead zirconate titanate (PZT) (53/47) powders were prepared by a cheating acetate sol-gel process. The drying temperature effect on crystallization behavior was conducted to determine the best conditions for preparing high content of perovskite PZT powders in the morphotropic region. DSC/TG analysis, FT-IR spectrum and X-ray diffraction were carried out to identify the reaction sequences and calculated the activation energy of every transition temperature during the drying procedures. In the present work, well-crystallized, single-phase perovskite PZT powders were obtained after drying PZT stock solution at 300°C for 1 h, then heat treatment at 600°C for 30 min. The dependence of this crystallization temperature on the drying conditions was discussed.
T-.I Chang, J-L. Huang, H-P. Lin, S-C. Wang, H-H. Lu, L. Wu, J-F. Lin, Journal of Alloys and Compounds 414 (2006) 224-229

B2084 – Al2O3-NiCrAl composites and functional gradient materials fabricated by reactive hot pressing

Al2O3-NiCrAl composites were fabricated by mixing NiO, Al and Cr powders and then reactive hot pressing. The high temperature alloy NiCrAl was formed by the reaction of extra Al, Cr and the Ni reduced from NiO. The Al2O3-NiCrAl composites with various Al2O3 fractions were successfully fabricated by the proper addition of extra Ni, Cr, Al or Al2O3 powders. A five-layer functional gradient material of YSZ-NiCrAl was fabricated using the Al2O3-NiCrAl composites with 25, 52.2 and 75 vol.% Al2O3 as interlayers. The results from XRD analysis, optical microscope observation and thermal cycling test show that the composites fabricated by this method consist of alpha-Al2O3 phase and (Ni, Cr, Al) solid solution mainly, together with a small amount of NiAl. The alpha-Al2O3 grains formed by this in situ reaction between NiO and Ni are ultrafine and uniformly distributed. The three-point bending strength for the composite with 52.2 vol.% Al2O3 is 363.5MPa. No cracking was found in the functional gradient materials after 10 thermal cycles up to 1000°C. It shows that the composites and the functional gradient material fabricated in this work have good strength, good resistance to oxidation and thermal shock.
J.Q. Li, K.M. Gu, J.N. Tang, S.H. Xie, Y.H. Zhuang, Materials Chemistry and Physics 97 (2006) 31-36

B2058 – Systems R-Fe-O (R = Ho, Er): Thermodynamic properties of ternary oxides using differential scanning calorimetry and solid-state electrochemical cells

The thermodynamic properties of three different types of ternary oxides RFeO3(s), R3Fe5O12(s) and RFe2O4(s) (where R = Ho and Er) have been determined by calorimetric and solid-state galvanic cell methods. Heat capacities of RFeO3(s) and R3Fe5O12(s) have been determined by differential scanning calorimetry from 130 to 860 K. Heat capacity measurements from 130 to 860K revealed l-type anomalies for RFeO3(s) and R3Fe5O12(s) compounds which are assigned due to magnetic order-disorder transitions. The oxygen chemical potentials corresponding to the three-phase equilibria involving these ternary oxides have been determined by using solid-state electrochemical cells. The standard molar Gibbs energies of formation of RFeO3(s), R3Fe5O12(s) and RFe2O4(s) have been computed from the oxygen potential data. Based on the thermodynamic information, oxygen potential diagrams have been computed for the systems R-Fe-O (R = Ho and Er) at two different temperatures: T = 1250 and 1450 K. Thermodynamic functions like Cp;m°, Sm°, H°, G°, (HT°-H0°), (HT°-H(298.15 K)°), -(GT°- H(298.15 K)°)/T, ?fHm°, and ?fGm° have been generated for the compounds RFeO3(s) and R3Fe5O12(s) based on the experimental data obtained in this study and the available data in the literature.
S.C. Parida, S.K. Rakshit, S. Dash, Ziley Singh, B.K. Sen, V. Venugopal, Journal of Solid State Chemistry 179 (2006) 2212-2230

B2011 – Effect of calcination temperature on the electrochemical behavior of ZnO-coated LiCoO2 cathode

Surface modification of LiCoO2 by metal oxides was verified to be an effective way to retard the abrupt capacity fading of LiCoO2 cycled at cut-off voltage higher than 4.2 V. In this study, LiCoO2 powders were coated with ZnO by the wet chemical method with a calcination process under various temperatures. Morphological and structural characterization of the bare and ZnO-coated LiCoO2 before and after cycling was carried out with field-emission scanning electron microscope (FE-SEM) and X-ray diffractometry (XRD). The electrochemical test results confirmed that ZnO coating was indeed a feasible approach to enhance the electrochemical performance of LiCoO2 at high voltage. The modified cathodes exhibited significantly improved capacity retention. In this material system, the optimal calcination temperature for ZnO-coated LiCoO2 is around 650°C. Although the initial capacity of coated LiCoO2 derived at 650°C was not the highest, its capacity retention was the most favorable. The mechanism of the cycleability improvement was proposed with respect to structural evolution, cation mixing degree, and the surface conditions.
T. Fang, J-G. Duh, Surface & Coatings Technology 201 (2006) 1886-1893

B1988 – Electrolyte additive trimethyl phosphite for improving electrochemical performance and thermal stability of LiCoO2 cathode

The purpose of this paper is to investigate compositions on the interface between LiCoO2 and electrolyte when trimethyl phosphite TMP(i) is used as an additive in 1M LiPF6/EC + DEC electrolyte system and the thermal stability of the electrolyte as well as Li0.5CoO2 mixed with the electrolyte. The electrochemical performance of LiCoO2 electrode in the two electrolyte systemswas also studied. It is found that the electrochemical performance, including capacity, cycle performance and 3.6V plateau efficiency, has been improved in the electrolyte with TMP(i) additive. FTIR analysis indicates that LixPOy is an important surface film composition on the cathode in TMP(i) containing system. A thicker and more passivating surface layer is formed when using TMP(i) additive as an additive. The thermal stability of the cathode is substantially improved in the electrolyte containing TMP(i) additive in the system, especially the exothermic peak around 190°C, which is associated with the reaction between active surface of cathode and solvents, is obviously restrained.
H.Y. Xu, S. Xie, Q.Y. Wang, X.L. Yao, Q.S. Wang, C.H. Chen, Electrochimica Acta 52 (2006) 636-642

B1987 – Synthesis and electrochemical properties of Li2S-B2S3-Li4SiO4

New Li+ ion-conductive glasses Li2S-B2S3-Li4SiO4 were synthesized by rapid quenching, and they were transformed into glass ceramics by heat treatment. The heat treatment increased the ionic conductivities of the Li4SiO4-doped glasses, and the highest ionic conductivity observed in the system was 1.0x10^(-3) S cm-1 at room temperature. The glass ceramics were highly stable against electrochemical oxidation with a wide electrochemical window of 10 V.
Y. Seino, K. Takada, B-C. Kim, L. Zhang, N. Ohta, H. Wada, M. Osada, T. Sasaki, Solid State Ionics 177 (2006) 2601-2603

B1982 – Calorimetric analysis of NaF and NaLaF4

Heat flux calorimetry was used to measure the heat capacity of NaF between 630 K and 1100 K. The results agreed well with previous measurements known from the literature. Similar experiments were performed on NaLaF4. This compound was synthesized from NaF and LaF3 and analyzed by X-ray diffraction. The heat capacity of NaLaF4 was determined for two temperature ranges: from 4 K to 400 K, for which adiabatic calorimetry, and from 623 K to 1213 K for which differential scanning heat flux calorimetry was used. The two heat capacity series fit smoothly; the resulting Cp,m function was used in a reassessment of the binary system (NaF + LaF3).
J.P.M. van der Meer, R.J.M. Konings, D. Sedmidubsky, A.C.G. van Genderen, H.A.J. Oonk, J. Chem. Thermodynamics 38 (2006) 1260-1268

B1950 – Study of sol-gel derived di-ureasils doped with zinc triflate

Zinc triflate (Zn(CF3SO3)2)-doped sol-gel derived di-urea cross-linked POE/siloxane ormolytes (designated as di-ureasils) with ?> n > 1 (where the salt content is expressed as n, the molar ratio of oxyethylene moieties to Zn2+ ions) were investigated. The hybrids with n > 5 are entirely amorphous; those with n > 10 are thermally stable up to approximately 305°C. The siliceous network of representative samples (n = 200 and 10) is essentially composed of (SiO)3Si(CH2)-environments and is thus highly branched. The distance between the structural units in samples with 200 > n > 10 and n < 7 is 4.2 and 4.3 Å, respectively. The estimated interdomain distance is 11 and 13 Å for xerogels with 200 > n > 20 and n < 10, respectively. At n = 1 a crystalline POE/Zn(CF3SO3)2 complex of unknown stoichiometry is formed. The conductivity maxima are located at n = 60 (3x10^(-6) S cm-1) and n = 20 (7x10^(-5) S cm-1) at 30 and 100°C, respectively.
S.C. Nunes, V. de Zea Bermudez, M.M. Silva, M.J. Smith, E. Morales, R.A. Sa Ferreira, L.D. Carlos, J. Rocha, Solid State Sciences 8 (2006) 1484-1491

B1941 – Thermal stability of magnetron sputtered Zr-Si-N films

The article reports on thermal stability of the structure and mechanical properties of Zr-Si-N filmswith a high (>25 at.%) Si content deposited froma ceramic ZrSi2 target by reactive magnetron sputtering. The annealed films were characterized using X-ray diffraction, microhardness and macrostress measurements, and differential scanning calorimetry. Special attention was devoted to the influence of the annealing temperature (up to 1600°C), annealing environment and presence of the substrate. It was found that the phase composition of the films strongly influences its thermal stability. Furthermore, (i) microhardness of the Zr-Si-N films sputtered under conditions used in our experiments is determined by their structure and not by the macrostress, (ii) crystallization of the X-ray amorphous films strongly depends on its phase composition, the ambient atmosphere and the incorporation of the substrate elements into the filmdue to interdiffusion during annealing, and (iii) X-ray amorphous Zr-Si-N films containing a high (>50 vol.%) content of the Si3N4 phase exhibit the highest thermal stability considerably exceeding 1000°C.
R. Daniel, J. Musil, P. Zeman, C. Mitterer, Surface & Coatings Technology 201 (2006) 3368-3376

B1920 – Synthesis and characterization of lead lanthanum zirconate titanate (Pb0.95La0.05Zr0.65Ti0.35)O3

Lanthanum doped lead zirconate titanate of composition (Pb0.95La0.05Zr0.65Ti0.35)O3 was prepared by gel entrapment technique (GET). The gel was suitably calcined and the resultant product was characterized by XRD, BET surface area analysis, dynamic light scattering and SEM. X-ray analysis of the powder calcined at 1023K indicated formation of product free from other phases. Characterization of the powder by XRD line-broadening showed an average particle size of ?40 nm. SEM study of the pellet sintered at 1173K showed presence of uniform grains of submicron size. DSC studies indicated that there is an electronic transition at the Curie temperature of 565 K. The dielectric constant of the sample measured as a function of temperature at different frequencies also showed an electronic transition at 543 K.
R.V. Pai, T.V.V. Rao, A. Kumar, S.K. Mukerjee, V. Venugopal, Journal of Alloys and Compounds xxx (2007) xxx-xxx

B1918 – Synthesis, FT-IR and X-ray diffraction investigations of gadolinium-substituted pyrochlore oxide Gd1.82Cs0.18Ti2O6.82 via a sol-gel process

Novel pyrochlore oxides Gd1.82Cs0.18Ti2O6.82 has been synthesized using the sol-gel process from the titanium alkoxide Ti(OR)4 and two ultra pure oxides Cs2CO3 and Gd2O3. Pure acetic acid was used as mutual solvent. This carboxylic acid does not act only as an acid catalyst, but also as ligand modifying the whole hydrolysis condensation process. The effect of heat treatment, to eliminate the organic material from xerogel was investigated by FT-IR spectroscopy. Based on thermal gravimetric (TG) and differential scanning calorimetric (DSC) analysis results, we suggest that thermal decomposition of the xerogel takes place in three major steps. X-ray powder diffraction (XRD) measurements were carried out to study the structure evolution of the sample and to determine the crystalline phases present after heat treatment. Crystal structure of oxygen deficient pyrochlore, Gd1.82Cs0.18Ti2O6.82 calcinated at 1000°C, was determined using the Rietveld method. It was found that the sample crystallise in the cubic symmetry with Fd3m space group and with a lattice parameter a = 10.1835 (4) Å. The oxygen vacancies in this compound are randomly distributed over the O sites. Conductivity in this material, which is an anionic conductor, results of migration of oxygen vacancies into the conduction pathways.
A. Garbout, S. Bouattour, M. Ellouze, A.W. Kolsi, Journal of Alloys and Compounds 425 (2006) 88-95

B1909 – Crystallisation of amorphous spray-dried precursors in the Al2O3-SiO2 system

The crystallisation of amorphous precursors has been studied in the whole range of composition in the Al2O3-SiO2 system. The amorphous precursors have been obtained by hydrolysing TEOS directly in a diluted aqueous solution of aluminium nitrate, spray drying the clear solution and heating the resulting powder. Up to 70 mol% Al2O3, only mullite crystallises around 980-1000°C; between 70 and 80 mol% Al2O3 mullite and spinel crystallise together; and for more than 80 mol% Al2O3 only spinel is formed. In the 70-80 mol% Al2O3 range of composition, when both mullite and spinel crystallise, low heating favours the crystallisation of mullite and it is nearly possible to crystallise only mullite from a 75 mol% Al2O3 sample. By rapid heating it is also possible to crystallise only spinel from the same 75 mol% Al2O3 precursor. The enthalpy and the activation energy for crystallisation are maximum for 60-80 mol% Al2O3. Heating the samples up to 1700°C for 1 h, the phase equilibrium is not reached, particularly when both mullite and spinel crystallise together, and theta-Al2O3 is still present.
A. Douy, Journal of the European Ceramic Society 26 (2006) 1447-1454

B1898 – Study on the kinetics properties of lithium hexafluorophosphate thermal decomposition reaction

The thermal decomposition of lithium hexafluorophosphate was studied by using C80 calorimeter, and the samples were heated at a 0.2 KImin 1 heating rate from ambient temperature to 573 K in pressure-sensitive transducer fitted and sealed vessel with argon atmosphere. It is found that LiPF6 decomposes near 433 K, and the gas product PF5 causes the pressure increasing. The LiPF6 decomposition reaction order is calculated based on the pressure data by two methods, its average value is n =1.5, then, the reaction is assumed to be dependent on the Arrhenius law and mass action law, and thus the activation energy and pre-exponential factor were calculated to be E =104.2 kJImol 1, A=1.12 107 s 1, respectively.
Q. Wang, J. Sun, S. Lu, X. Yao, C. Chen, Solid State Ionics 177 (2006) 137 - 140

B1877 – Significance of kinetic theories on the recrystallization of kaolinite

Mathematical methods have been extensively used for the analysis of data obtained from non-isothermal thermal analysis of kaolinite or other clay minerals and Kissinger description is frequently considered. It is based on an Avrami-type transformation and an Arrhenian dependence of the reaction rate. In general, the calculation of the activation energy uses an incorrect neglect of the temperature dependence of the transformation rate. For kaolinite, Kissinger method applied to dehydroxylation gives an activation energy close to the measured enthalpy change for the reaction, but for recrystallization the activation energy exceeds the enthalpy change by a factor as high as 30. It is related to the complex character of recrystallization, since nucleation and crystal growth simultaneously occur, with the existence of both spinel and mullite phases. Consequently, the temperature dependence of recrystallization cannot be assumed to be Arrhenian. An interpretation is also found with Polanyi-Wigner equation applied to kaolinite transformations. Using thermodynamic data of entropy variation, the recrystallization rate should attain very high values, ranging from 5 to 10 order of magnitude over standard values for solid transformations. These observations cast some doubts on calculated activation energy of kaolinite recrystallization obtained from Kissinger kinetic method.
K. Traoré, F. Gridi-Bennadji, P. Blanchart, Thermochimica Acta 451 (2006) 99-104

B1875 – Thermochemical characteristics of La(n+1)Ni(n)O(3n+1) oxides

Lanthanum nickelates: La2NiO(4+d), La3Ni2O(7-d), La4 Ni3O(10-d) and LaNiO(3-d) the members of Ruddlesden-Popper series La(n+1)NinO(3n+1) were prepared using citrate route. Dissolution enthalpies of complex oxides as well as a number of subsidiary substances were measured by means of Calvet calorimeter in 1M solution of hydrochloric acid at 25°C. The dissolution scheme of complex oxides in hydrochloric acid was proposed and enthalpies of formation of the complex oxides from binary oxides were calculated considering oxygen nonstoichiometry of these substances. Enthalpies of step-by-step oxidation were evaluated. Partial enthalpy contribution of LaO layers was calculated endothermic equals to 30.9 J/mol while partial enthalpy contribution of perovskite LaNiO3 layers was negative equals to -97.0 J/mol. Enthalpy of formation of any complex oxide of Ruddlesden-Popper series fits very well to the linear regression based on these values.
D.O. Bannikov, A.P. Safronov, V.A. Cherepanov, Thermochimica Acta 451 (2006) 22-26

B1870 – Aluminium borates: synthesis via a precipitation process and study of their formation by DSC analysis

Aluminium borates have been synthesized via a precipitation process. Their formation has been studied by DSC analysis and X-ray diffraction. Aqueous solutions of aluminium nitrate and boric acid in various proportions were precipitated into solutions of ammonium carbonate, acting as a base like ammonia. The resulting mixtures were evaporated to dryness in order to recover the soluble boron species (ammonium borate). The by-product ammonium nitrate was decomposed at 300°C. The DSC analysis, at 5 Kmin-1, showed the crystallization temperature of aluminium borates to decrease regularly with the increase of the boron content in the sample, from 900°C for the A9B2 compound (abbreviation of 9Al2O3.2B2O3) to 670°C for a composition "AB2". A9B2 was stable, at least up to 1200°C. For boron-richer compositions, like "A6B2", a boron-excess A9B2 solid solution was crystallized at the detriment of A4B2. This metastable solid solution decomposed at 1000°C into A9B2 and boron oxide. Even for the composition "A4B2", A9B2 crystallized along with A4B2. The latter compound was found to be stable up to 1000°C, and to decompose into A9B2 and boron oxide at higher temperature, without any sign of melting. This decomposition was confirmed by thermogravimetric analysis. The problem of volatilization of boric acid or boric oxide, often encountered in the synthesis of borates, is avoided.
A. Douy, Solid State Sciences 7 (2005) 117-122

B1845 – Heusler bulk materials as targets for pulsed laser deposition: growth and characterisation

This work concerns the preparation and characterisation of homogeneous bulk Co2Mn (Si, Ge, Ga, Sn Sb0.8Sn0.2) to be used as targets for pulsed laser deposition of magnetic contacts for spintronic devices. The samples have been prepared by direct synthesis from elemental powders followed by vertical gradient freeze. Characterisation of their structural properties and compositional homogeneity was performed by X-ray diffraction and energy-dispersive X-ray spectroscopy combined with scanningelectron microscopy. The results show one-phase for the Heusler alloys. The Curie temperatures of the samples have been measured by both thermogravimetric analysis and differential scanning calorimetry and are in a good agreement with the previously published values. The saturation magnetisation values are close to the values for single crystals.
A.S. Manea, O. Monnereau, R. Notonier, F. Guinneton, C. Logofatu, L. Tortet, A. Garnier, M. Mitrea, C. Negrila, W. Branford, C.E.A. Grigorescu, Journal of Crystal Growth 275 (2005) e1787-e1792

B1821 – Sol-gel synthesis and microwave assisted sintering of zirconia-ceria solid solution

Zirconia, ceria and zirconia-ceria solid solution have been synthesized using internal gelation process. The thermal decomposition behaviour of internally gelated ZrO2, CeO2 and Zr0.9Ce0.1O2 were investigated using thermo-gravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) along with X-ray diffraction (XRD). The ceria gel decomposes to give a crystalline phase whereas zirconia as well as zirconia-ceria gels decompose to amorphous phase which on heating undergoes irreversible transformation to corresponding equilibrium crystalline phases. The sol-gel derived product could be sintered to 92% theoretical density using microwave energy source in 60 min. The oxides obtained from the thermal decomposition are found to be nano-phasic in nature.
K.S. Kumar, T. Mathews, Journal of Alloys and Compounds 391 (2005) 177-180

B1813 – Heat capacity, enthalpy and entropy of strontium bismuth niobate and strontium bismuth tantalate

The heat capacities and enthalpy increments of strontium bismuth niobate SrBi2Nb2O9 (SBN) and strontium bismuth tantalate SrBi2Ta2O9 (SBT) were measured by the relaxation method (2-150 K), Calvet-type heat-conduction calorimetry (305-570 K) and drop calorimetry (773-1373 K). The temperature dependences of non-transition heat capacities in the form Cpm = 324.47 + 0.06371T-5.0755x10^6/T2 JK-1 mol-1 (298-1400 K) and Cpm = 320.22 + 0.06451T-4.7001x10^6/T2 JK-1 mol-1 (298-1400 K) were derived for SBN and SBT, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15K S°m (SBN) = 327.15 ± 0.80 and S°m (SBT) = 339.23 ± 0.72 JK-1 mol-1 were evaluated from the low-temperature heat capacity measurements.
J. Leitner, M. Hampl, K. Ruzicha, D. Sedmidubsky, P. Svoboda, J. Vejpravova, Thermochimica Acta 450 (2006) 105-109

B1782 – Calorimetric study of reactions occurring between impregnated activated fibres and hydrogen sulphide

Activated carbon fibres, which exhibit high specific area and numerous active surface sites constitute very powerful adsorbents and are widely used in filtration to eliminate pollutants from liquid or gaseous effluents. The fibres studied in this work are devoted to the filtration of gaseous effluents containing very small amounts (few vpm) of hydrogen sulphide. To improve their fixation capacity towards H2S the activated fibres are impregnated in an aqueous solution of potassium hydroxide and then thermally treated. The treatment leads to the deposition of crystallites of K2CO3 showing a great activity for H2S gas in the presence of water vapour. The H2S fixation mechanism proposed can be summarised as follow: K2CO3 and H2S dissolve in a liquid aqueous solution formed on the fibre surface. Then carbonate ions and H2S molecules react together almost completely to yield HS species. This mechanism has been validated and completed by the study of the thermal effects induced when the treated fibres are in contact with H2S together with water vapour. The study has been carried out using a calorimetric method. The variations of standard enthalpy of reactions involved in the fixation mechanism are measured and compared to the data given by the thermodynamic tables for bulk solutions.
L. Meljac, L. Perier-Camby, G. Thomas, Carbon 43 (2005) 1407-1415

B1756 – Investigations on the phase equilibria of some hydride ion conducting electrolyte systems and their application for hydrogen monitoring in sodium coolant

Electrochemical meters for measuring hydrogen levels in liquid sodium need thermodynamically stable hydride ion conducting electrolytes. In order to identify electrolytes that have high hydride ion conductivity, phase diagram of systems consisting of low melting compounds such as CaCl2-LiCl, SrBr2-LiBr, SrBr2-SrHBr and CaBr2-CaHBr were investigated by differential scanning calorimetry and their phase diagrams established. Using these information and supplementary information on effects of addition of alkaline earth hydride to these systems, potential electrolytes were tested for their use in electrochemical meters. Meters were constructed using electrolytes with (i) 22mol%SrCl2- 12.2mol%CaCl2-54.5mol%LiCl-11.3mol%CaHCl, (ii) 70mol%LiCl-16mol%CaHCl-14mol%CaCl2 and (iii) 40mol%- CaHBr-60mol%CaBr2 compositions. Output of meters that had Li ions in liquid phase electrolyte showed non-linearity at low hydrogen levels. Output of meters using CaBr2-40mol%CaHBr solid showed linearity in the concentration range of 50-250 ppb in sodium.
Kitheri Joseph, K. Sujatha, S. Nagaraj, K.H. Mahendran, R. Sridharan, G. Periaswami, T. Gnanasekaran, Journal of Nuclear Materials 344 (2005) 285-290

B1740 – Formation enthalpy of ThSiO4 and enthalpy of the thorite ==> huttonite phase transition

"The standard enthalpy of formation of thorite and huttonite and the enthalpy of the phase transition between these polymorphs were determined using high-temperature oxide melt solution calorimetry and transposed temperature drop calorimetry. Standard enthalpies of formation of thorite and huttonite are reported for the first time and are 2117.6 4.2 kJ/mol and 2110.9 4.7 kJ/mol, respectively. Based on our measurements, thorite and huttonite are metastable relative to SiO2 (quartz) and ThO2 (thorianite) at standard conditions, but are presumably stabilized at high temperature by the entropy contribution. Based on the measured enthalpy of the thorite-huttonite phase transition of 6.7 2.5 kJ/mol, a dP/dT slope for the transformation was calculated as 1.21 0.45 MPa/K."
L. Mazeina, S.V. Ushakov, A. Navrotsky, L.A. Boatnar, Geochimica et Cosmochimica Acta 69 (2005) 4675-4683

B1729 – Calorimetry, dilatometry at high temperature

Methods to characterize materials at high temperature are undergoing major development. Thermal analysis methods, especially using high-temperature thermoanalyzers and large amounts of sample have proved to be efficient in providing this information.
P. Le Parlouer, I. Chan, American Ceramic Society Bulletin 80 (2001) 31-37

B1727 – Wärmekapazitätsmessungen nach scanning-methoden bis zu hohen temperaturen

Scanning calorimetric methods permit determination of heat capacities at high temperatures up to 1600°C. For disk systems with power compensation application limits are in order of 700°C, and for cylindrical systems with electrical calibration up to 1000°C. For the high temperature range above 1000°C DSC plates and a cylindrical calorimetric systems based on the CALVET principle ('MULTI HTC') are known. For cylindrical calorimetric systems the precision of the Cp data is between 2 and 5% even at high temperatures without any requirements on the kind and shape of samples. These results are better than data provided by DSC plate systems.
R. Naumann, Journal of Thermal Analysis and Calorimetry 53 (1998) 659-669

B1686 – Direct measurement of relative partial molar enthalpy of SiO2 in SiO2-M2O (M=Li, Na, K, Cs) binary and SiO2-CaO-Al2O3 ternary melts

The relative partial molar enthalpies, ?SiO2, of SiO2 in SiO2-M2O (M = Li, Na, K and Cs) binary and SiO2-CaO-Al2O3ternary melts were directly measured by drop-solution calorimetry at 1465 K and 1663 K. ?SiO2 changes from exothermic to endothermic as silica content increases, confirming the tendency toward immisciblity seen from activity measurements. It is concluded that ?SiO2 is negative due to acid-base reactions and charge-coupled substitutions when the melt is composed of fewer Q4 and more Q3 and Q2 species, but positive due to structural strain when the melt is composed of mostly Q4 species. The ?SiO2 obtained by calorimetry is a useful measure of basicity, when comparing different alkali and alkaline earth oxides.
M. Morishita, A. Navrotsky, M.C. Wilding, Journal of the American Ceramic Society 87 (2004) 1550-1555

B1685 – Enthalpy of formation of cubic yttria-stabilized zirconia

Oxide melt solution calorimetric measurements were made to determine the enthalpy of formation of c-yttria-stabilized zirconia (YSZ) with respect to the oxides m-ZrO2 and C-type YO1.5. The enthalpy of formation can be fit either by a quadratic equation or by two straight line segments about the minimum near x = 0.40. The quadratic fit gives a strongly negative interaction parameter, Ù = -93.7 ± 12.0 kJ/mol, but does not imply regular solution behavior because of extensive short-range order. In this fit, the enthalpy of transition of m-ZrO2 to c-ZrO2, 9.7 ± 1.1 kJ/mol, is in reasonable agreement with earlier estimates and that of C-type to cubic fluorite YO1.5, 24.3 ±14.4 kJ/mol, is consistent with an essentially random distribution of oxide ions and anion vacancies in the high-temperature fluorite phase. The two straight-line segments give 6.1 ± 0.6 kJ/mol and 5.5 ± 2.5 kJ/mol for these transitions, respectively. The latter value would imply strong short-range order in cubic fluorite YO1.5. Clearly more complex solution thermodynamic descriptions need to be developed. The enthalpy of transition from the disordered c-YSZ phase to the ordered ä-phase at 25°C was also measured and was 0.4 ± 1.6 kJ/mol. No energetic difference between the disordered c-YSZ phase and the ordered ä-phase underscores the importance of short-range order in c-YSZ. Enthalpy data were combined with Gibbs free energy data to calculate entropies of mixing. Using the quadratic fit, negative excess entropy of mixing in the cubic solid solution, relative to a system with maximum randomness on cation and anion sublattices, was found and was another indication of extensive short-range order in c-YSZ.
T.A. Lee, A. Navrotsky, I. Molodetsky, Journal of Materials Research 18 (2003) 908-918

B1684 – Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (alpha-FeOOH), lepidocrocite (gamma-FeOOH), and maghemite (gamma-Fe2O3)

The enthalpy of formation from the elements at 298.15 K (?Hf°) of lepidocrocite (gamma-FeOOH) and maghemite (gamma-Fe2O3) has been measured by acid-solution calorimetry as -549.4 ± 1.4 and -808.1 ± 2.0 kJ/mol, respectively. The ?Hf° of goethite (alpha-FeOOH) was measured by high-temperature transposed temperature drop and acid-solution calorimetry as -559.5 ± 1.1 and -560.7 ± 1.2 kJ/mol, respectively. Mathematical programming analysis (MAP) was used to generate an internally consistent data set for goethite and hematite, using the thermodynamic data presented in this study for goethite, and additional thermodynamic data for hematite and synthesis experiments of Baneyeva and Bendeliani (1973) (BB) and Voigt and Will (1981) (VW). Using BB brackets, the thermodynamic values for goethite were refined to ?Hf° = -561.9 kJ/mol and entropy at standard pressure and temperature (S°) = 59.2 J/K.mol; using VW brackets, we arrived at ?Hf° = -561.4 kJ/mol and S° = 59.5 J/(K.mol). However, MAP failed to include the magnetic transition in goethite, and the derived data should be used with caution. Combined with the entropies for the studied phases, the Gibbs free energies of formation from the elements at 298.15 K are -489.8 ± 1.2, -480.1 ± 1.4, and -727.9 ± 2.0 kJ/mol, for goethite, lepidocrocite, and maghemite, respectively. Only hematite (alpha-Fe2O3) and goethite have a stability field in the Fe2O3.H2O system at low to moderate pressures; maghemite and lepidocrocite are meta-stable at all pressures and temperatures. Goethite is 1.0 ± 1.4 kJ/mol metastable in ?G with respect to hematite and liquid water, and 2.0 ± 1.4 kJ/mol metastable with respect to hematite and water vapor at 298 K and 50% relative humidity.
J. Majzlan, K-D. Grevel and A. Navrotsky, American Mineralogist 88 (2003) 855-859

B1683 – In situ calorimetric study of the hexagonal-to-lamellar phase transformation in a nanostructured silica/surfactant composite

Restructuring of hexagonal silica/surfactant composites under hydrothermal conditions was studied using in situ scanning microcalorimetry to understand the energetic changes associated with these rearrangements. Thermal processes can be associated with either changes in packing of the organic template or with chemistry of the cross-linked inorganic framework. To sort these out, calorimetric data were collected as composites were heated in water, where a hexagonal-to-lamellar phase transformation occurs, and as composites were heated in an acidic boric acid buffer, where no phase change is observed. The scanning calorimetric data were correlated with in situ low angle XRD to explore the relationship between rearrangements of the nanoscale architecture and the various energetic processes occurring in these materials. 29Si NMR, which tracks changes in framework bonding, TGA and 1H NMR, which measure surfactant loss from the composite, and 13C NMR, which tells us about surfactant rearrangement and degradation, were also correlated with the calorimetric data. Both samples showed an endotherm at 70-71 C that was assigned to an order-disorder transformation of the organic surfactant of the composite. In this same moderate temperature range, broad exotherms observed in both samples were associated with condensation of the silica framework. Two endotherms were observed in calorimetric scans of the water-treated composites that were not present in data collected on composites treated in boric acid. These endotherms were thus associated with the hexagonal-to-lamellar phase transformation, which has an enthalpy change of +0.5 ± 0.1 kJ/(mol SiO2) or +2.4 ± 0.3 kJ/(mol surfactant) and entropy changes of +1 J K-1 (mol SiO2)-1 or +6 J K-1 (mol surfactant)-1. The results quantify differences in thermodynamic stability in silica/surfactant composites and identify the physical, molecular, and nanoscale changes that influence stability in these materials.
A F.Gross, S.Yang, A.Navrotsky, and S.H.Tolbert J. Phys. Chem. B, 107 (12), 2709 -2718, 2003

B1682 – Direct measurements of water adsorption enthalpy on hafnia and zirconia

A commercial surface area analyzer and Calvet-type microcalorimeter were combined for measurements of heats of gas-solid interactions, providing enhanced resolution, flexibility, and throughput compared to conventional methods. Integral adsorption enthalpies for half monolayer coverage on HfO2 and ZrO2 surfaces were found to be in the range -130-190 and -110-170 kJ per mole of gaseous H2O for differently prepared monoclinic phases and -70 and -90 kJ/mole for tetragonal phases from precipitation. The surface enthalpy for anhydrous tetragonal ZrO2 was derived as 1.23±0.04 J/m2 from water adsorption and high-temperature solution calorimetry data.
S.V. Ushakov and A. Navrotsky, Appl. Phys. Lett. 87, 164103 (2005) (3 pages)

B1681 – High-temperature calorimetry of zirconia: Heat capacity and thermodynamics of the monoclinic-tetragonal phase transition

The high-temperature heat capacity of zirconia was directly measured by differential scanning calorimetry between T = (1050 and 1700) K and derived from the heat content measured by transposed temperature drop calorimetry between T = (970 and 1770) K, including the monoclinic-tetragonal (m-t) phase transition region. The enthalpy and entropy of the m-t phase transition are (5.43 ± 0.31) kJ . mol-1 and (3.69 ± 0.21) J . K-1 . mol-1, respectively. Values of thermodynamic functions are provided from room temperature to 2000 K.
Y. Moriya and A. Navrotsky, J. Chem. Thermodynamics 38 (2006) 211-223

B1653 – High-temperature heat capacities of EuPO4 and SmPO4 synthetic monazites

High-temperature enthalpy increments of monazite-type EuPO4 and SmPO4 were measured by drop calorimetry in the temperature range 450-1570 K and the heat capacity was derived. The excess heat capacity Cexs was calculated by subtracting the lattice heat capacity, interpolated from isostructural LaPO4 (4f0) and GdPO4 (4f7) compounds. A good agreement was found with Cexs calculated from (estimated) crystal field energies. The heat capacity of PrPO4 was estimated with this approach.
K. Popa and R.J.M. Konings, Thermochimica Acta 445 (2006) 49-52

B1652 – Effect of lithium-sodium mixed-alkali on phase transformation kinetics in Er3+/Yb3+ co-doped aluminophosphate glasses

Er3+ doped aluminophosphate glasses with various Na2O/Li2O ratios were prepared at 1250°Cusing a silica crucible to study mixed alkali effect (MAE). The effect of relative alkali content on glass transition temperature, crystallization temperature and thermal stability were investigated using differential scanning calorimetry (DSC). In addition, apparent activation energies for crystallization, Ec, were determined employing the Kissinger equation. The effect of Al2O3 content on the magnitude of MAE was also discussed. No mixed-alkali effect is observed on crystallization temperature.
Y. Fang, M. Liao and L. Hu, Thermochimica Acta 443 (2006) 179-182

B1645 – Thermal behaviour of mechanochemically synthesized nanocrystalline CuS

Thermal behaviour of mechanochemically synthesized nanocrystalline CuS particles by high-energy milling in an industrial mill has been studied. Structure properties were characterized by X-ray powder diffraction that reveals the formation of copper sulphide CuS as well as of copper sulphate CuSO4.5H2O. Thermal properties of the as-prepared products were studied by the differential scanning calorimetry together with X-ray inspection for detection by pass products formed. The decomposition of the as-prepared sample has been studied too. Thermal stability of the anhydrous CuSO4 formed by the thermal decomposition is lower than the thermal stability of non-milled samples. The final product of the thermal decomposition is metallic copper instead of Cu2O, which is stable up to 1100°C. Differential scanning calorimetry (DSC) analysis proved that the percentage of chalcantite in the covellite mechanochemically synthesized by high-energy milling is 48-51%.
E. Godocíkova, P. Balaz, J.M. Criado, C. Real and E. Gock, Thermochimica Acta 440 (2006) 19-22

B1586 – High temperature enthalpy, heat capacity and other thermodynamic functions of solid InN

The heat capacity and the heat content of indium nitride were measured by Calvet calorimetry (305-390 K) and by drop calorimetry (427-774 K). The temperature dependence of the heat capacity in the form Cpm = 43,886 + 8,194 x 10^(-3) T - 1,007 x 10^6 T^(-2) + 8,353 x 10^7 T^(-3) (J K-1 mol-1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy S0m (298 K) = 42.51 J K-1 mol-1 was assessed taking into account the recently reported phonon density of states, low temperature Cpm and the current data. Thermodynamic functions calculated on the basis of our results and literature data on the heat of formation of InN are given.
J. Leitner, P. Marsik, D. Sedmidubsky, K. Ruzicka, Journal of Physics and Chemistry of Solids 65 (2004) 1127-1131

B1577 – Thermodynamic properties of lithium mica : Lepidolite

Calorimetric measurements were made on natural sample of lepidolite having the composition (K0.80Na0.05Ca0.07Rb0.16Cs0.03)(Li1.34Al1.40Fe3+0.01)[Si3.25Al0.75O10]F1.80(OH)0.20 from Na-Li-type rare-element-rich pegmatites of East Sayany, Russia. High-temperature enthalpy increments were measured with a Tian-Calvet calorimeter at 444-972 K using the drop method. The resultant (T) equation in the interval T = 298.15-972 K was calculated: = 316.10 + 228.12 x 10^(-3) T - 50.10 x 10^5 T^(-2) (J K-1 mol-1) [± 0.4%] and the value of (298.15 K) = 327.8 J K-1 mol-1 was obtained. The standard molar enthalpy of formation from the elements was determined by high-temperature drop solution calorimetry in molten lead borate at T = 973 K. The value of ?f(298.15 K) for lepidolite was found to be -6201 ± 18 kJ mol-1. The thermodynamic properties of lepidolite of idealized composition KLi1.5Al1.5[Si3AlO10]F2 were estimated based on the experimental data obtained.
L.P. Ogorodova, I.A. KiselevaL, V. Melchakova, T.N. Schuriga, Thermochimica Acta 435 (2005) 68-70

B1544 – Direct calorimetric measurement of enthalpies of phase transitions at 2000°C-2400°C in Yttria and Zirconia

High-temperature differential thermal analysis provided data on phase transitions in zirconia and yttria. The tetragonal form of ZrO2 transforms to the cubic fluorite structure at 231117151C with an enthalpy of 3.473.1 kJ/mol. Cubic C-type Y2O3 transforms, probably to the fluorite structure, at 230817151C with DH547.773.0 kJ/mol. This high-temperature polymorph melts at 238217151C with an enthalpy of fusion of 35.67 3.0 kJ/mol.
A. Navrotsky, L. Benoist, H. Lefebvre, J. Am. Ceram. Soc. 88 (2005) 2942-2944

B1443 – Calorimetric study of the mechanochemically activated sphlalerite

The thermal behavior of mechanochemically activated sphalerite during aging was investigated by calorimetry. The results indicate that mechanochemically activated sphalerite releases the stored energy which may origin from a series of complex transformations. The amount of energy released increases with the grinding time but remains almost constant after grinding for 1 h. It is independent of the grinding atmosphere and is related to the ball-mill medium. The XRD results illustrate a difference of the microstructure between activated and non-activated sphalerite. The microstructure of the activated sphalerite remains the same when it is heated in a calorimeter for the measurement of the heat released. The particle size analyses show that the particle size of the activated sphalerite increases when it is heated in the calorimeter. Therefore, it can be concluded that the released energy is probably caused by the decrease of the specific surface energy.
Z. Xiao, Q. Chen, Z. Yin, P. Zhang, Thermochimica Acta 404 (2003) 265-270

B1396 – High temperature enthalpy and heat capacity of GaN

The heat capacity and the heat content of gallium nitride were measured by calvet calorimetry (320-570 K) and by drop calorimetry (670-1270 K), respectively. The temperature dependence of the heat capacity in the form Cpm=49.552+5.440x10^(-3) T^(-2).190x10^6 T^(-2)+2.460x10^8 T^(-3) was derived by the least squares method. Furthermore, thermodynamic functions calculated on the basis of our experimental results and literature data on the molar entropy and the heat of formation of GaN are given.
J. Leitner, A. Strejc, D. Sedmidubsky, K. Ruzicka, Thermochimica Acta 401 (2003) 169-173

B1366 – Differential thermal analysis and high-temperature calorimetry of refractory materials

H. Kleikamp, Thermans (2002) 1-4

B1312 – Drop calorimetric measurements on U0.79Pu0.21O2

R. Kandan, R. Babu, K. Nagarajan, P.R. Vasudeva Rao, Thermans (2002) 169-171

B1275 – Heat capacity of glass-forming fluorozirconates

Heat capacities of fluorozirconates between 25 and 800°C have been determined by differential scanning calorimetry (DSC) and transposed-temperature-drop calorimetry. Heat capacities of glasses are relatively similar, while the heat capacities of melts are more distinct among different compositions in the superliquidus range. The average heat capacity between the glass transition temperature (Tg) and the liquidus temperature (Tl) has a value close to the heat capacity of the supercooled liquid just above Tg, but is higher than the heat capacity of high-temperature melts. Therefore, the fluorozirconate exhibits an increased heat capacity in the Tg-Tl interval. The region of high heat capacity is related to the restructuring in the supercooled liquid regime. This behavior supports our previous study which suggests a substantial structural change from melt to glass. The restructuring gives excess contributions to heat capacity, enthalpy, and entropy and allows the supercooled liquid to significantly lower its free energy (relative to one which does not change structural state), resulting in a diminished thermodynamic driving force for crystallization. Glass formation in fluorozirconates is not only controlled by kinetics but also assisted by restructuring thermodynamics.
I.C. Lin, A. Navrotsky, Journal of Non-Crystalline Solids 215 (1997) 125-133

B1254 – High-temperature heat capacity of Co3O4 spinel : thermally induced spin unpairing transition

A strong anomaly was found in the heat capacity of Co[3]O[4] between 1000 K and the decomposition temperature. This anomaly is not related to the decomposition of Co[3]O[4] to CoO. The measured entropy of transition, ?S = 46 ± 4 J mol[#751]K[#751] of Co[3]O[4], supports the interpretation that this anomaly reflects a spin unpairing transition in octahedrally coordinated Co[3+] cations. Experimental values of heat capacity, heat content and entropy of Co[3]O[4] in the high temperature region are provided
K. Mocala, A. Navrotsky and D. M. Sherman, Phys. Chem. Minerals 19 (1992) 88-95

B1246 – Thermodynamic properties of Na2W2O7(s) and Na2W4O13(s) in the temperature range 298.15-1000K

273.15 K T Hm o of each compound were measured by a drop method using a high-temperature Calvet calorimeter HT-1000 in the temperature range (273 to 979) K {or T = (273 to 878) K for K2W2O7}. The expression for molar heat capacity of each compound against temperature was obtained from experiment results.
S. Liu, Q. Chen and P. Zhang, Thermochimica Acta 371 (2001) 7-11

B1245 – Heat capacity of potassium tungstates K2WnO(3n+1) (n=2,3,4) at temperatures from 273 K to 979 K.

Compounds K2Wn O3n + 1 (n = 2, 3, 4) were synthesized using a pyrometallurgical technique. The products were characterized by X-ray diffraction analysis and found to be single-phase compounds. The enthalpy increments
Q. Chen, S. Liu, P. Zhang, J. Chem. Thermodynamics 31 (1999) 513-519

B1244 – Standard enthalpy of formation of paratungstate B ion (H2W12O42)10- (aq)

The enthalpy of sodium paratungstate Na10H2W12O42.27H2O(s) dissolved in solution of 1.0 mol dm-3 LiClO4 was measured at 298.15 K using a Calvet twin-vessel microcalorimeter. The standard enthalpy of formation of paratungstate B ion, (H2W12O42)10-(aq), was calculated on the basis of the experimental results. Combining this with values from the literature led to ?fHm° ((H2W12O42)10-, aq, 298.15 K)=-(11653.5±10.9) kJ mol-1.
S. Liu, Q. Chen, P. Zhang, Thermochimica Acta 352-353 (2000) 103-105

B1243 – Standard enthalpy of formation of sodium paratungstate Na10H2W12O42.27H2O(s)

The standard enthalpy of decomposition of Na10H2W12O42.27H2O(s) at 298.15 K was measured using the method of three-step calorimetry in a Calvet twin-vessel microcalorimeter. The standard enthalpy of formation of Na10H2W12O42.27H2O(s) at 298.15 K was first obtained as -(21898.2±10.8) kJ mol-1.
Q. Chen, S. Liu, P. Zhang, Thermochimica Acta 352-353 (2000) 99-102

B1239 – Kinetic study of isothermal crystallization in amorphous Al33Ni16Zr51 produced by mechanical alloying

A non-conventional way of production has been chosen to prepare Al33Ni16Zr51 amorphous alloy: mechanical alloying which allowed the microstructure of the material to be monitored. For this type of non-equilibrium alloys, the evolution toward an equilibrium state and the crystallization kinetics were studied by differential scanning calorimetry. The crystallization processes were interpreted in terms of several theoretical models based on nucleation and growth processes.
J-Ph. Braganti, O. Held, F-A. Kuhnast, E. Illekova, Thermochimica Acta 362 (2000) 71-78

B1238 – Anomalies in heat capacity measurements of RuO2-TiO2 system.

DSC was used for heat capacity measurements of pure RuO2 in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti1-xRux)O2 (x0.15 and x0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within ±2% of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend on the chemical composition x. It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation model.
T. Mitsuhashi and A. Watanabe, Journal of Thermal Analysis and Calorimetry 60 (2000) 683-689

B1237 – Thermodynamic aspects of the vaterite-calcite phase transition.

Although vaterite is the least stable anhydrous calcium carbonate polymorph, it is formed as a metastable phase in some normal and pathological biomineralisation processes. In this work, thermodynamic aspects of the vaterite-calcite phase transition were comprehensively studied. Vaterite samples were prepared by different methods and characterised for the composition, crystal structure, specific surface and grain size. All products were identified to be pure vaterite by careful X-ray diffraction measurements. The enthalpy and Gibbs energy of transition were determined by precise calorimetric and potentiometric measurements. The reliability of the thermodynamic data for the vaterite-calcite phase transition derived from this work was shown by the use of different calorimetric methods to determine the enthalpy of transition and the independent measurements of heat capacity and entropy of vaterite. Our recommended values are trs G*=-2.9±0.2 kJ mol-1, trs H*=-3.4±0.2 kJ mol-1 and trs S*=-1.7±0.9 J K-1 mol-1, where the uncertainties are given as twice the standard deviations.
G. Wolf, E. Königsberger, H. G. Schmidt, L.-C. Königsberger and H. Gamsjäger, Journal of Thermal Analysis and Calorimetry 60 (2000) 463-472

B1233 – High-temperature calorimetry of fusion reactor blanket materials

The experimental techniques of high-temperature heat flow calorimetry are explained in view of selection and mass optimisation of standards for caloric calibration, condition of samples, heating rates and liner materials. Calorimetric work is illustrated on enthalpy measurements of Li4SiO4, Li2SiO3, Li2ZrO3, LiAlO2 and Li2TiO3 by isothermal drop calorimetry and by heat capacity calculations therefrom. The physics of second-order transitions is discussed taking Li4SiO4 as an example. An additional enthalpy uptake occurs in the critical temperature range under anisothermal conditions. The behaviour is reversible. The anisothermal calorimetry is further outlined by measurements of the enthalpy of solidification of Li4SiO4 and the enthalpy of transformation and melting of beryllium.
H. Kleykamp, Netsu Sokutei 27 (2000) 100-104

B1202 – Etude expérimentale et modélisation des équilibres solide-liquide du système binaire H2O-UO2(NO3)2.

The binary system H2O-UO2(NO3)2 was studied by solubility measurements and constant heat flow thermal analysis. Temperature and composition of the eutectic transformation between ice and uranyl nitrate hexahydrate were accurately defined. A new hydrate with 24 molecules of water decomposes at -21°C according to the peritectoid reaction + 18 The quasi-ideal model was applied to the solid-liquid equilibria, using the following reaction hypothesis: ((UO 2 2+ )) + 2((NO 3 - ))+ h((H2O)) ((UO2OH+aq)) + ((H3O+aq + 2((NO 3 - aq)) A complete calculation of the binary system was carried out with a global ionic hydration number h equal to 9 in the aqueous solutions. It allowed to the melting enthalpies of uranyl nitrate hydrates.
R. Tenu, S. Gentil, S. Baudu, J.J. Counioux, Journal of Thermal Analysis and Calorimetry 58 (1999) 89-101

B1114 – Valence states of copper in copper ferrite spinels CuxFe(3-x)O4 (O

The oxidation in cation deficient spinels of copper iron spinels CuxFe3-xO4 (0 < x < 1) synthesized by soft chemistry with a grain size < 50 nm has been investigated by thermal measurements (DTG and DSC). For stoichiometric synthesized spinels when the copper content determines the number of oxidizable cations 1-x per mole of ferrite, three oxidation phenomena corresponding to Cu+ at B-sites (130°C), Fe2+ at B-sites (180°C) and Cu+ at A-sites (240°C) have been found in close relation with the cation-oxygen distance of each oxidizable cation. For nonstoichiometric synthesized spinels CuxFe3-xO4+d with d < 0 when the oxidation reveals a mass gain larger than that calculated with 1-x, the presence of additional interstitial Cu+ ions has been envisaged. The oxidation temperature of these interstitial ions ( > 300°C) is higher than that for Cu+ ions at Asites suggesting that interstitial copper ions also essentially reside in A-sites.
E. Kester, B. Gillot, C. Villette, Ph. Tailhades, A. Rousset, Thermochimica Acta 297 (1997) 71-78

B1062 – Surface nucleation of µ-cordierite in cordierite glass : thermodynamic aspects.

The heterogeneous nucleation rate of µ-cordierite at the surface of cordierite glass (2 MgO . 2Al2O3 . 5SiO2) is discussed in terms of classical nucleation theory (CNT). Calculations are based on experimental viscosity data and estimates of the melting temperature and melting enthalpy of µ-cordierite from calorimetric measurements. A virtual melting temperature of the metastable µ-cordierite, Tm, was estimated, by means of X-ray measurements, from the primary occurrence of µ-cordierite after brief thermal treatment. Tm was found to lie in the range 1300-1467°C. The molar enthalpy of melting, ?Hm, was calculated from calorimetric measurements and literature data. Referring to the molar weight of the formula unit, M = 585g.mol-1, ?Hm could be narrowed to the range 171-190 kJ mol-1. The heterogeneous volume nucleation rate, I*(T), was estimated from the apparent nucleation rate of p-cordierite which was previously studied at fractured and polished surfaces of cordierite glass by means of transmitting light microscopy. I*(T) steadily increases up to 235 K above the glass transition temperature at 815°C without reaching a maximum. In the present paper, this exceptional temperature-dependence is discussed in terms of CNT. The best fit of experimental data was obtained for Tm ? 1467°C, a low liquid-crystal interracial free energy, sigma, and a low activity of nucleating substrates, phi, if sigma.phi^(1/3) ? 100 mJ m-2 is valid.
R. Müller, R. Naumann, S. Reinsch, Thermochimica Acta 280/281 (1996) 191-204

B1054 – Elaboration de poudres de yig par coprécipitation.

This paper deals with an original method for the preparation of ferrites with the garnet structure by coprecipitation. The different transformations of the coprecipitated hydroxide during heat treatment are studied and reported. YIG crystallization from amorphous oxide is significantly dependent of some parameters. However, pure homogeneous materials can be obtained at low temperature (800-850C) for Al substituted YIG Y3AlxFe5-xO12 with 0.5x1.
P. Grosseau, A. Bachiorrini, B. Guilhot, Journal of Thermal Analysis 46 (1996) 1633-1644

B1034 – Die spezifische Wärmekapazität und die thermische Längenausdehnung von Salz/Keramik-Kompositmaterialien für Temperaturen bis 1000°C

W.Notter, Thèse Stuttgart (1995)

B1030 – Water desorption and aragonite-calcite phase transition in scleractinian corals skeletons.

Using differential scanning calorimetry coupled with thermogravimetry measurements, we have observed the existence of double endothermic peaks probably connected with two separate phenomena: water desorption, followed by the aragonite-calcite transition. Determination of the enthalpy of the first endothermic peak allowed us to predict the existence of hydrogen-bonding interactions between the oxygen atoms of the carbonate planes and the water molecules.
N. Passe-Coutrin, Ph. N'Guyen, R. Pelmard, A. Ouensanga, C. Bouchon, Thermochimica Acta 265 (1995) 135-140

B1026 – Calorimetry of electrode reaction under linear sweep-current polarization.

The mathematical-physical equation concerning the process of calorimetry of electrode reactions was deduced, and the corresponding solutions were obtained respectively for the period of the electrochemical polarization and that of the natural cooling. The calorimetry of the anodic oxidation of ferrocyanide to ferricyanide under linear sweep-current polarization was carried out, the obtained apparent enthalpy change of the electrode reaction agreed well with that obtained by the calorimetry with constant currents. The developed calorimetry with linear sweep-current and the data processing method are applicable for quick determination of apparent enthalpy changes of electrode reactions.
H. Zhang, P. Zhang, Z. Fang, Journal of Thermal Analysis 45 (1995) 151-156

B1015 – Measurement of heat of fusion of peridotite in the system CaO-MgO-Al2O3-SiO2

H. Kojitani, M. Akaogi, JSCTA (1995) 184-185

B0986 – Investigation of the thermodynamic properties of y-Al2O3

The heat capacities of y-Al2O3 were measured from 50 to 700°C using an HT1000 calorimeter. The heat of transformation y-Al2O3 to alpha-Al2O3 was directly measured using an HT1500 calorimeter. Combination of these results with the values from the literature led to ?Hm = -(1657.2 ± 1.5) kJ mol-1, Sm = (52.30 ± 2.00) J mol-1 K-1 and ?fGm = - (1564.2 ± 2.0) kJ mol-1.
C. Qiyuan, Z. Wenming, C. Xinmin, G. Songqing, Y. Guanqun, Z. Huifang, Y. Zhonglin, Thermochimica Acta 253 (1995) 33-40

B0953 – Heat capacity of rare earth oxides obtained with an extensively calibrated high-temperature calorimeter up to 1400°C

U.Kolitsch, H.J. Seifert, H.L. Lukas, F. Aldinger, Discussion meeting on Thermodynamics of alloy (1994) poster

B0951 – Calorimetric study of sol and gel formation

J.W. Fleming, S.A. Fleming, D. Kelly, Ultrastructure processing of advanced materials, chapter 7, 77-85

B0929 – The measurement of heat of fusion of model basalt

H. Kojitani, M. Akaogi, JSCTA 100-101

B0896 – Metastable phases in powders of the system Y2O3-Al2O3 obtained by two chemical synthesis

S. Le Floch, J. Coutures, A. Douy, M. Gervais, J.P. Coutures, Third Euro-Ceramics 1 (1993) 1029-1034

B0859 – Detailed study of a two component smectic 4TPB-8OCB system with a nematic gap. Phase diagram and viscosity study

K. Czuprynski, J. Janik, J.K. Moscicki, Liquid Crystals 14 (1993) 1371-1375

B0858 – Three ring dioxanes as dopants enhancing the stability of the smectic C phase

J. Szulc, K. Czuprynski, R. Dabrowski, J. Przedmojski, Liquid Crystals 14 (1993) 1377-1387

B0852 – Thermophysical properties of the composite ceramic-salt system (SiO2/Na2SO4)

A composite ceramic-salt packed bed configuration is being developed for high-temperature thermal storage. The range of application is industrial waste heat recovery and utilization, off peak utilization reserve and solar thermal power systems application
W. Notter, Th. Lechner, U. Groß and E. Hahne, Thermochimica Acta 218 (1993) 455-463

B0851 – Inverse drop-calorimetry. A study of metastable and nonequilibrium phases

The method of inverse drop-calorimetry was extended for studying the thermodynamic properties of metastable and nonequilibrium phases over a wide temperature range and in the phase transition regions.
V.L. Solozhenko, Thermochimica Acta 218 (1993) 395-400

B0723 – Etude calorimétrique de l’enthalpie de dissolution d’alumines industrielles dans des bains cryolithiques

The partial molar enthalpies of dissolution in cryolitic baths of two different industrial aluminas were measured by calorimetry at 1290 K. The influence of the physico-chemical properties of the aluminas and of additions of excess AIF3 in the bath were examined. The effects of the presence in the solvent of NaF and LiF (F" donors) and of AIF3 in excess (F" acceptor) agree well with the proposed mechanism of dissolution of alumina in cryolite.
M. Yagoubi, Y. Bertaud et R. Castanet, Journal of Thermal Analysis 36 (1990) 589-597

B0665 – Trends in the high-temperature heat capacities of ternary chalcopyrite semiconductors

The anharmonic contribution to the heat capacity of any chalcopyrite semiconductor AIBmC vl or AnBwC v is evaluated. It is shown that the degree of lattice anharmonicity decreases with increasing atbmic weight of the constituen! atoms of the compounds, and there is no essential difference in the degree of lattice anharmonicity of the two groups of compounds. Except for CdGeAs2, the trend in the Grfineisen constants is the same.
G. Kühn, H. Neumann and E. Nowak, Journal of Thermal Analysis 33 (1988) 197-203

B0661 – Modélisation par analyse thermique de réactions de greffage d’oxo-silatrane sur les sites actifs de substrats carbonés de composites carbone/carbone

J.P. Rosnet, G. Palavit, P. Vast, AFCAT (1990) 289-296

B0597 – Heat capacity and kinetic parameters in the glass transformation interval of diopside, anorthite and albite glass

The heat capacity CP of rate-cooled glasses of CaMgSi2O6 (diopside), CaAl2Si2O8 (anorthite) and NaAlSi3O8 (albite) composition has been measured employing a Tian-Calvet microcalorimeter. Experiments were performed with heating/cooling rates q of between 2 and 18 K hr.-1 at temperatures from above the glass transition temperature Tg to temperatures 250 K below Tg. With decreasing cooling rate q, the glass transition temperature is shifted to lower temperatures [by 16, 20 and 30 K for diopside, anorthite and albite, respectively, for one order of magnitude in cooling rate q (K hr.-1)]. Assuming Arrhenian behavior in the glass transformation interval, an activation enthalpy can be derived for each glass which is consistent with the activation enthalpy for viscous flow, derived from low-temperature viscosities (10^10-10^13 dPa s). Kinetic parameters for structural relaxation were extracted from fictive temperatures Tf derived from heat capacities employing methods previously developed by DeBolt et al. Agreement between experimental and predicted fictive temperatures is excellent for the compositions studied. The results may be useful for all quantitative considerations which are related to the kinetic behavior of thermodynamic properties in the glass transition interval.
R.M. Martens, M. Rosenhauer, H. Büttner and K. von Gehlen, Chemical Geology 62 (1987) 49-70

B0580 – Energetics, composition, and structure of alkoxide derived silica gels

P. Maniar, A. Navrotsky, E.M. Rabinovich, D.L. Wood and N.A. Kopylov, Mat. Res. Soc. Symp. Proc. 121 (1988) 323-329

B0579 – Measurement of the thermal capacity of solids by DSC

The methods for determining the thermal capacity of solids using a SETARAM DSC-III calorimeter have been studied. Two methods can be employed: periodic heating and continuous heating. The method using periodic heating is characterized by an accuracy of 0.6% ,'while the method with continuous heating has an accuracy of 5%. Thermal capacity measurements on corundum, copper oxide and magnetite are reported.
G.K. Demensky and O.A. Teplov, Journal of Thermal Analysis 32 (1987) 451-461

B0573 – Measurement of the enthalpy of mixing of the liquid system CaO-B2O3 by drop calorimetry

x
J. Klein, F. Müller, High Temperatures - High Pressures 19 (1987) 201-209

B0565 – Etude thermocinétique des phénomènes de dissolution par calorimétrie Calvet à haute température. Dissolution d’alumines dans la cryolithe

Although the thermal curves given by a Calvet calorimeter can be considered representative of the thermogenesis of slow phenomena, this is not the case for the brief thermal effects of dissolution, for example, which need typically no more than twenty minutes. At high temperatures, a numerical method of deconvolution of the recorded signal was applied in order to obtain the proper thermogenesis of the phenomenon. The time constants of the calorimeter were determined from thermal effects due to the dropping into the bath of small quantities of silver and platinum. The method was applied to the dissolution of s-alumina and industrial aluminas in cryolithic baths at 1290 K. The different kinds of alumina could be classified according to their time of dissolution. The dependence of the alumina concentration of the bath on the dissolution rate was also investigated.
M. Yagoubi, J.P. Dubes, Y. Bertaud et R. Castanet, Journal of Thermal Analysis, 31 (1986) 1359-1373

B0525 – High-temperature specific heats of chalcopyrite – type semi-conductors

The molar specific heat was measured for any chalcopyrite - type compounds in the temperature range from 300 to 500 K. An analysis of the experimental data for AgInS2 and AgGaSe2 for example showed that the contribution to the specific beat Sue to lattice anharmonicity can be described by a polynomial of third order in the temperature.
W. Möller, G. Kühn and H. Neumann, Thermochimica Acta 93 (1985) 669-672

B0524 – Etude thermique de coacervats et de gels destinés à l’élaboration de céramiques et émaux

G. Palavit, A.M. Bera, P. Vast, AICAT, Ferrara, (1986) 68-72

B0509 – Direct measurement of the enthalpy of fusion of diopside

Crystalline diopside, CaMgSi2O6, was dropped directly into a Setaram "HT1500" calorimeter operating at high temperature. At 1575 < T < 1624 K, the heat content of the crystals was in excellent agreement with previously published results. Above 1634 K, a rise in the enthalpy was seen, supporting the incongruent melting reported by Kushiro. The total enthalpy of fusion at 1665 K, the nominal melting point, is 138.5 kJ/mol, in excellent agreement with measurements which used a cycle that involves dropping the liquid to form a glass and measuring heats of solution of glass and crystals. The heat content of a glassy diopside starting material was also measured. Because the calorimetric experiment lasts only about 8 minutes, these measurements could be extended into the supercooled liquid range (to 1170 K) before the onset of rapid crystallization. A change in slope in the measured heat contents gives a glass transition temperature of 933 K, about 70 K lower than that reported by other methods. A linear fit of all the data above T8 (supercooled liquid at 970 to 1170 K, stable liquid at 1668 to 1766 K) gives an average heat capacity for the liquid of 332.8 J/mol . K, comparable to the value of 334.6 J/mol . K reported by Richet and Bottinga.
D. Ziegler and A. Navrotsky, Geochimica et Cosmochimica Acta 50 (1986) 2461-2466

B0456 – Microcalorimetrie à haute température (en Russe)

N. Topor (1984)

B0448 – Etude des minéraux à haute température (en Russe)

N. Topor, Mineralogia, 1241 (1981)

B0419 – Etude thermodynamique du système uranium-oxygène à 1050°C

La méthode microcalorimétrique a été utilisée pour déterminer, à 1050°C, l'enthalpie molaire partielle de mélange de l'oxygène, ?H(O2), dans les oxydes d'uranium de compositions comprises entre UO2.00 et UO22.60. Les limites obtenues pour les domaines UO2 + x et U4O9-y sont en parfait accord avec celles déterminées par Kotlar [13]. Les grandeurs thermodynamiques pour les oxydes U4O9-y ainsi que l'enthalpie standard de formation à 1050°C de UO2.242 à partir de UO2 et de O2 ont été calculées.
C. Picard and P. Gerdanian, Journal of Nuclear Materials 99 (1981) 184-189

B0385 – Thermodynamic and structural aspects of phase transitions in some uraniumum coumpounds

J.P. Bros et al., Proceedings and Esta, Aberdeen (1981) 139

A2384 – Differences between films and monoliths of sol–gel derived aluminas

This work compares thin layers (films) and monoliths prepared from alumina sols with respect to their microstructure, thermal evolution, porosity and specific surface area. After heat treatment at similar temperatures, films and monoliths showed the same qualitative changes in porosity and specific surface area. However, some marked quantitative differences were detected. Film fragments had a lower open porosity, a lower specific surface area and a narrower pore size distribution. Furthermore, the thermal evolution showed a markedly different burnout of organic components between films and monoliths. The observed differences between films and monolith can be explained by the ageing history of the sols during sample preparation
M. Dressler, M. Nofz, P. Klobes, I. Dörfel, S. Reinsch, Thin Solid Films 519 (2010) 42–51

A2382 – Alternative perovskite materials as a cathode component for intermediate temperature single-chamber solid oxide fuel cell

This paper exploits the suitability of three perovskite materials Ba0.5Sr0.5Co0.8Fe0.2O3?? (BSCF), GdBaCo2O5+? (GBC) and Ba0.5Sr0.5Mn0.7Fe0.3O3?? (BSMF) as SOFC cathodes in the single-chamber configuration operating at the intermediate temperature range. TG analysis showed high thermal stability depending on the crystalline phases of the materials. The catalytic activity of these three materials for hydrocarbon conversion was investigated under a realistic feed, i.e. with hydrocarbon, oxygen, water and carbon dioxide. Electrochemical impedance spectroscopy of the various cathodes tested in symmetric cell configuration revealed a B-site dependence of the electrode catalytic activity for oxygen reduction. High temperature (1000 °C) powder reactivity tests over a gadolinium doped-ceria (CGO) and perovskite cathode revealed excellent chemical compatibility of BSMF and CGO. Catalytic tests associated with thermal and structural characterization attest to the suitability of these materials in the single-chamber configuration.
Cyril Gaudillère, Louis Olivier, Philippe Vernoux, Chunming Zhang, Zongping Shao, David Farrusseng, Journal of Power Sources 195 (2010) 4758–4764

A2381 – Preparation, characterization and application in BSA solution of silica ceramic membranes

This work is devoted to the study of ceramic membranes elaborated from mineral oxides. The mesoporous silica layer was prepared by the sol–gel method using a SiO2 sol. The silica membranes were obtained by slip casting silica solution on a clay tubular support, followed by drying and sintering at 600 °C during 2 h. The effect of various contact times on the layer thickness and the pore diameters was investigated. Two membranes M1 and M2 were obtained having 12.5 and 27 ?m thickness respectively. Their pore diameters were centred at 2.5 nm for M1 and 1.5 nm for M2. The performances of the two membranes were compared in terms of water flux, permeate flux, retention rate of bovine serum albumin (BSA) and the resistance of fouling. Results indicated that the water permeability was 77.3 L/h m2bar for M1 and 34.56 L/h m2bar for M2. The BSA retentions for M1 and M2 were 78.33% and 98.64% respectively. For M2, the irreversible fouling resistance represented a little contribution of the total resistance (17.53%), while for M1, there was high contribution (84.34%). The effect of pH of BSA by filtration M1 membrane has been examined.
Salma Fakhfakh, Semia Baklouti, Samir Baklouti, Jamel Bouaziz, Desalination 262 (2010) 188–195

A2380 – Porous alumina ceramics prepared with wheat flour

It is shown that wheat flour can be used as a pore-forming and body-forming agent in ceramic technology. In contrast to pure native starch, however, the pores do not result from the swelling starch granules alone but are mainly due to protein-assisted foaming. Therefore the porosity is significantly higher and the pore size larger than that resulting from the starch granules alone, and the wet milling time applied for homogenizing the ceramic suspensions becomes the most critical process parameter. Alumina suspensions with 70 wt.% alumina and 20–30 vol.% wheat flour with different initial particle size (fine grade and semolina, respectively) have been prepared using milling times of up to 8 h. Porosities of up to approx. 60% can be achieved with only 20 vol.% of flour or semolina after 8 h of milling time, with the cell sizes (diameters of pore cavities resulting from foam bubbles) being essentially independent of the milling time (median diameters of 120–240 ?m). Effective pore throat sizes (i.e. diameters of cell windows or channels between cells), measured via mercury porosimetry, are 1–2 ?m for short milling times (2–3 h), but for long milling times (8 h) they change by more than one order of magnitude to median sizes of 20–30 ?m, closely corresponding to the median size of wheat starch granules (approx. 20 ?m).
Eva Gregorová, Willi Pabst, Zuzana Zivcová, Ivona Sedlárová, Svatava Holíková, Journal of the European Ceramic Society 30 (2010) 2871–2880

A2376 – Synthesis and characterization of Bi31Cr5O61.5, a new bismuth chromium oxide, potential mixed-ionic–electronic conductor for solid oxide fuel cells

Single crystals, as well as pure powder of the new bismuth chromate, Bi31Cr5O61.5 were synthesized by slow cooling of a mixture of Bi2O3–Cr2O3 and then fully structurally characterized using X-ray diffraction. It crystallizes in the monoclinic space group P21/n with unit cell parameters a = 23.5794(8), b = 11.6189(4), c = 24.3629(8) Å and ? = 108.02(1)°, Z = 4. The final conventional agreement factors converged to R = 0.0540 and wR = 0.0561 for 27520 independent reflections. The +VI chromium oxidation state was proved by thermogravimetric and magnetic measurements. The structure can be described by the association of isolated CrO4 tetrahedra surrounded by 11 or 12 Bi atoms forming truncated or not cuboctahedra. The stability of both pure powder sample and pressed sintered pellets was studied at elevated temperature by X-ray diffraction and by dilatometry previously to ionic conductivity measurements done by impedance spectroscopy.
Marie Colmont, Michel Drache, Pascal Roussel, Journal of Power Sources 195 (2010) 7207–7212

A2375 – Preparation, characterization, and electrochemical application of mesoporous copper oxide

Mesoporous CuO was successfully synthesized via thermal decomposition of CuC2O4 precursors. These products had ring-like morphology, which was made up of nanoparticles with the average diameter of 40 nm. The electrochemical experiments showed that the mesoporous CuO decreased the overvoltage of the electrode and increased electron transference in the measurement of dopamine.
Liang Cheng, Mingwang Shao, Dayan Chen, Yuzhong Zhang, Materials Research Bulletin 45 (2010) 235–239

A2373 – Carbonatation and Decarbonatation Kinetics in the La2O3-La2O2CO3 System under CO2 Gas Flows

The carbonatation of La2O3 oxide and the decarbonatation of lanthanum carbonate phase La2O2CO3 are investigated using thermal and thermogravimetry analyses under CO2 gas flow. The initial phase La2O3 is first elaborated from pyrolysis of a LaOHCO3 precursor. Then, thermal and thermogravimetry analyses are carried out under CO2 flow, as temperature increases then decreases. The carbonatation kinetics of La2O3 is determined at three fixed temperatures. Electrical impedance spectroscopy is performed to determine the electrical responses associated with ionic mobilities and phase changes, in the temperature range 25 to 9 0 0 ? C. The electrical conduction during heating under C O 2 gas flow should be linked to two regimes of ionic conduction of the carbonate ions. From these electrical measurements, the ionic mobility of carbonate ions C O 3 2 ? is found to be close to 0.003 · 1 0 ? 4 ? c m 2 ? s ? 1 ? V ? 1 at 7 5 0 ? C for the monoclinic La2O2CO3 phase.
Bahcine Bakiz, Frédéric Guinneton, Madjid Arab, Abdeljalil Benlhachemi, Sylvie Villain, Pierre Satre, Jean-Raymond Gavarri, Advances in Materials Science and Engineering Volume 2010, Article ID 360597

A2367 – On the LiNi0.2Mn0.2Co0.6O2 positive electrode material

Layered LiNi0.2Mn0.2Co0.6O2 phase, belonging to a solid solution between LiNi1/2Mn1/2O2 and LiCoO2 most commercialized cathodes, was prepared via the combustion method at 900 °C for a short time (1 h). Structural, electrochemical and magnetic properties of this material were investigated. Rietveld analysis of the XRD pattern shows this compound as having the ?-NaFeO2 type structure (S.G. R-3m; a = 2.8399(2) ?; c = 14.165(1) ?) with almost none of the well-known Li/Ni cation disorder. SQUID measurements clearly indicate that the studied compound consists of Ni2+, Co3+ and Mn4+ ions in the crystal structure. X-ray analysis of the chemically delithiated LixNi0.2Mn0.2Co0.6O2 phases reveals that the rhombohedral symmetry was maintained during Li-extraction, confirmed by the monotonous variation of the potential–composition curve of the Li//LixNi0.2Mn0.2Co0.6O2 cell. LiNi0.2Mn0.2Co0.6O2 cathode has a discharge capacity of ?160 mAh g?1 in the voltage range 2.7–4.3 V corresponding to the extraction/insertion of 0.6 lithium ion with very low polarization. It exhibits a stable capacity on cycling and good rate capability in the rate range 0.2–2 C. The almost 2D structure of this cathode material, its good electrochemical performances and its relatively low cost comparing to LiCoO2, make this material very promising for applications.
Yassine Bentaleb, Ismael Saadoune, Kenza Maher, Latifa Saadi, Kenjiro Fujimoto, Shigeru Ito, Journal of Power Sources 195 (2010) 1510–1515

A2366 – Multifunctional sol-gel derived thin film based on nanocrystaline hydroxyapatite powders

The aim of this work was to prepare bioactive hydroxyapatite coatings by sol-gel method and to study the effect of thermal treatment temperature upon the bioactivity and corrosion protection of these coatings on Ti6Al4V alloy. The application of (DTA/TGA) and (XRD) has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size and degree of crystallinity. (SEM/EDX) has been applied to study the surface morphology of coated samples before and after immersion in simulated body fluid (SBF) to detect the biomimetic precipitation of the bonelike apatite. The obtained results show that all the prepared samples are ceramic nanocrystalline with crystal structure and composition like hydroxyapatite, with little deviations from that present in the human bone. The bioactivity of the studied samples is found to be closely related to the thermal treatments applied. That is, the bioactivity decreases as the temperature of the thermal treatment increase. Coatings from such prepared hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti6Al4V alloy for biomedical applications. The corrosion behaviour of the resulting hydroxyapatite coatings in a (SBF) has been studied by electrochemical impedance spectroscopy (EIS). The hydroxyapatite coated Ti6Al4V alloy displayed excellent bioactivity when soaked in the (SBF) and acceptable corrosion protection behaviour.
A.A. El hadad, V. Barranco, A. Jiménez-Morales, E. Peon, J.C. Galván, Journal of Physics:Conference Series 252 (2010) 012007

A2361 – Structural and thermal characterization of SiO2–P2O5 sol–gel powders upon annealing at high temperatures

This study deals with SiO2–P2O5 powders obtained by sol–gel process, starting from tetraethoxysilane (TEOS) as precursor for SiO2 and either triethylphosphate (TEP) or phosphoric acid (H3PO4) as precursors for P2O5. In the case of samples prepared with H3PO4, TG–DTA data showed an accentuated weight loss associated to an endothermic effect up to about 140 °C, specific for the evaporation of water and ethylic alcohol from structural pores, and also due to alkyl-amines evaporation. Sol–gel samples prepared with TEP exhibited different thermal effects, depending on the type of atmosphere used in the experiments, i.e. argon or air. XRD analysis revealed that annealed sol–gel samples prepared with H3PO4 showed specific peaks for silicophosphate compounds such as Si3(PO4)4, Si2P2O9, and SiP2O7. XRD results for annealed sol–gel samples prepared with TEP indicated mainly the presence of a vitreous (amorphous) phase, which could be correlated with SEM images. The presence of SiO2 in the sample might be expected. Thus, we have searched for any SiO2 polymorph possible to crystallize. Only potential peaks of cristobalite were identified but some of them are overlapping with peaks of other crystalline phosphates. SEM analysis indicated a decrease of the amount of crystalline phases with the increase in the annealing temperature
M. Elisa, B.A. Sava, A. Volceanov, R.C.C. Monteiro, E. Alves, N. Franco, F.A. Costa Oliveira, H. Fernandes, M.C. Ferro, Journal of Non-Crystalline Solids 356 (2010) 495–501

A2356 – In-situ processing of carbon coatings on the surface of SiC-based fibers

Carbon coatings have been formed on the surface of free carbon containing Tyranno ZMI and Nicalon SiC-based fibers by reaction with chlorine gas (chlorination) in the temperature range 550–675 °C. The kinetics and growth mechanisms have been investigated for both fibers. Results have shown that, for similar experimental conditions, the reactivity of both fibers displayed noticeable discrepancies. It has thus been observed that the Nicalon fiber was more prone to chlorine-based treatment and displayed a thicker carbon coating than the ZMI fiber. These results have also revealed that, in both cases, these thicknesses can be closely monitored by physical parameters such as temperature and aging duration. The nature of the obtained coating has also been investigated by various experimental devices. AES, SEM and TEM analyses have thus evidenced that these carbon coatings were uniform and well adherent whereas AFM showed that the chlorine-based treatments resulted in a nanometer-range roughness at the fiber surface. Adsorption gas analyses also revealed a microporosity coupled with a high specific surface area. The chemical composition of the final products was determined by XPS and Mass Spectroscopy. Finally, the oxidation behavior which was investigated by thermogravimetric analysis revealed that oxidation occurs at a quite low temperature (225 °C).
A. Delcamp, L. Maillé, B. Rufino, S. Mazerat, R. Pailler, A. Guette, P. Weisbecker, H. Plaisantin, E. Philippe, S. Loison, Surface & Coatings Technology 205 (2010) 703–709

A2355 – Comparison of Sr-doped and Sr-free La1?xSrxMn0.5Cr0.5O3±? SOFC Anodes

Single phase La1 ? xSrxMn0.5Cr0.5O3 ± ? (LSMC, xSr = 0 and 0.2) and composite LSMC:Gd-doped ceria (GDC) mixed ionic and electronic conducting anodes were studied in half-cell and full-cell electrochemical configurations using humidified fuel environments at 700 to 800 °C. We demonstrate here that the removal of Sr from La1 ? xSrxMn0.5Cr0.5O3 ± ? improves both the thermo-chemical stability and the electronic conductivity of these materials in a humidified H2 environment, while also enhancing their H2 oxidation activity, when operating at 700 and 800 °C. It is also shown that the addition of 50:50 wt.% GDC:LaMn0.5Cr0.5O3 ± ? results in the retention of all of these benefits, as compared to a mixture of GDC with the Sr-containing La0.8Sr0.2Mn0.5Cr0.5O3 ± ? (xSr = 0.2) oxide.
L. Deleebeeck, J.L. Fournier, V. Birss, Solid State Ionics 181 (2010) 1229–1237

A2350 – Stoichiometric control of single walled carbon nanotubes functionalization

Covalent modifications of single-walled carbon nanotubes, while being useful for their manipulation and functionalization, alter the electronic properties through disruption of the nanotube ? electronic system. To avoid such negative impact, we demonstrate here that carbon nanotubes can be alkylated in a controlled manner by first preparing and isolating reduced nanotube salts with varied charge/C ratios. The reduction reaction, in the present work performed in THF with a K/naphthalene salt, is almost quantitative and the KCx salt can be isolated with a wide range of x values ranging from 10 to 370, while remaining soluble in DMSO. The reaction of these salt solutions with two alkyl bromide reagents yields functionalized SWCNTs, as demonstrated by combined IR, UV-vis-NIR and Raman spectroscopies, XPS and thermogravimetric measurements. In particular, quantification of the number of functional groups grafted shows a direct correlation with the charge/C ratio of the initial salts. Detailed analysis of Raman spectra confirms this control over the extent of covalent functionalization and shows it is not selective towards any type of SWCNT. This latter observation is ascribed to the isolation of the intermediate salts as solids, resulting in homogenization of charge densities on the reduced CNTs.
Damien Voiry Olivier Roubeau, Alain P enicaud, J. Mater. Chem., 2010, 20, 4385–4391

A2341 – Caracterização superficial de nanopartículas de BaTiO3 preparado pelo método dos precursores poliméricos

A síntese de nanopartículas e a sua caracterização têm sido a grande mola propulsora do desenvolvimento de materiais nano-estruturados. Pouca atenção tem sido dedicada aos fenômenos físico-químicos relacionados às enormes superfícies intrínsecas destes materiais. Dentre eles, o titanato de bário ocupa uma posição de destaque devido ao seu grande potencial na geração de produtos de alta tecnologia. Neste estudo o BaTiO3 foi sintetizado pelo método dos precursores poliméricos, que proporciona a geração de nanopartículas de grande uniformidade química. Contudo, o uso de cátions que formam carbonatos de alta estabilidade pode inviabilizar o uso do método. Os pós de titanato de bário preparados apresentaram elevada área de superfície específica, porém com formação de fases parasitas de carbonato de bário e carbonatos adsorvidos na superfície do titanato de bário. O estudo da química de superfície utilizando métodos como espectroscopia de infravermelho e análises eletrocinéticas permitiu a caracterização deste contaminante e demonstraram indícios de condições específicas de dissolução do carbonato de bário, que podem possibilitar a descontaminação do titanato de bário.
S. L. M. Brito, D. Gouvêa, Cerâmica 56 (2010) 228-236

A2340 – Separation of single-walled carbon nanotubes from graphite by centrifugation in a surfactant or in polymer solutions

Electric arc single-walled carbon nanotubes (SWCNTs) can be separated from their graphitic impurities by a single centrifugation process in a surfactant or in polymer solutions. The purity of SWCNT dispersions, evaluated from near infrared (NIR) spectroscopy measurements, substantially increased after centrifugation at a moderate speed. The supernatant NIR purity was affected by the surfactant choice, following the sequence: sodium cholate ? Pluronic F68 > sodium dodecylbenzene sulfonate > Pluronic F127 > sodium dodecyl sulfate. NIR purity was also influenced by the centrifugation speed and the pristine SWCNT concentration in the starting dispersion, but not by the surfactant concentration. SWCNT enrichment was not observed in a pure organic solvent (N,N?-dimethylformamide) under identical centrifugation conditions. X-ray diffraction analysis demonstrated that graphitic impurities were mostly eliminated from SWCNTs during the centrifugation process in a surfactant or in polymer solutions. Thermogravimetric analysis under CO2 showed that metallic impurities were substantially reduced during the centrifugation process.
A. Anson-Casaos, J.M. Gonzalez-Dom?nguez, M.T. Mart?nez, Carbon 48 (2010) 2917-2924

A2337 – Physical and photoelectrochemical characterizations of hematite ?-Fe2O3: Application to photocatalytic oxygen evolution

The physical properties and photoelectrochemical characterization of ?-Fe2O3, synthesized by co-precipitation, have been investigated in regard to solar energy conversion. The optical gap is found to be 1.94 eV and the transition is indirectly allowed. The chemical analysis reveals an oxygen deficiency and the oxide exhibits n-type conductivity, confirmed by a negative thermopower. The plot log ? vs 1/T shows linearity in the range (400–670 K) with the donor levels at 0.14 eV below the conduction band and a break at ?590 K, attributed to the ionization of the donors. The conduction occurs by small polaron hopping through mixed valences Fe2+/3+ with an electron mobility ?400 K of 10?3 V cm2 s?1. ?-Fe2O3 exhibits long term chemical stability in neutral solution and has been characterized photoelectrochemically to assess its activity as bias-free O2-photoanode. The flat band potential Vfb (?0.45VSCE) and the electron density ND (1.63 × 1018 cm?3) were determined, respectively, by extrapolating the linear part to C?2 = 0 and the slope of the Mott Schottky plot. At pH 6.5, the valence band (+1.35VSCE) is suitably positioned with respect to the O2/H2O level (+0.62 V) and ?-Fe2O3 has been evaluated for the chemical energy storage through the photocatalytic reaction: (, ?G = 213.36 kJ mol?1). The best photoactivity occurs in solution (0.025 M, pH 8) with an oxygen rate evolution of 7.8 cm3 (g catalyst)?1 h?1.
S. Boumaza, A. Boudjemaa, S. Omeiri, R. Bouarab, A. Bouguelia, M. Trari, Solar Energy 84 (2010) 715–721

A2336 – Poly(vinyl alcohol)-colloidal silica composite membranes for fuel cells

The aim of this study is to develop an environmentally and friendly poly(vinyl alcohol) based low cost membrane with improved ionic conductivity, thermal and mechanical stability. In this work, the effect of colloidal silica content on membrane properties was investigated. Sulfosuccinic acid (SSA) was used as the sulfonating agent. In order to enhance the mechanical and ionic conduction properties, colloidal silica was used. The range of silica content in the membrane solution investigated was 5–20%. For the characterizations, the synthesized membranes were subjected to FT-IR, TGA, tensile strength analysis, water uptake, ion exchange capacity (IEC) and impedance measurements for proton conductivity. Synthesized membranes demonstrated high water uptake (up to 80%) without swelling, high ion exchange capacities was found to increase with increasing SSA content. The proton conductivity of CS doped membranes increased with increase in temperature and the temperature dependence showed significant change in the CS doped membranes. An increase in the values of the proton conductivity was driven by the mobility of free charges (free ions) as the temperature was increased. Addition of SSA and CS to the polymer matrix improved the thermal stability of the membranes. It was also discovered that membranes were in a composite structure and colloidal silica particles did not contribute to the structure of the polymer matrix at the molecular level. Mechanical durability of the membranes having SSA content above 15% decreased and these membranes showed a more fragile structure.
Muzaffer Balbas?, Burcu Gözütok, Synthetic Metals 160 (2010) 150–155

A2330 – Stability of Ba(Zr,Pr,Y)O3-? materials for potential application in electrochemical devices

Ba(Pr1-xZrx)1-yYyO3-? materials were obtained by a two-step process of mechanical activation followed by annealing at 1250 °C. Guidelines for correlations between structure and composition, and their role on stability were characterised as a function of atmosphere, with special emphasis on degradation by carbonation in CO2-rich atmospheres, or upon redox changes. The role of humidity on these degradation processes was also analysed by taking into account differences between wet and dry atmospheres with regards to the onset of secondary phases and structural changes. Thermodynamic calculations were used to predict 2-phase and 3-phase equilibria in contact with CO2-rich atmospheres and to obtain corresponding stability diagrams. The thermodynamic calculations were also used as guidelines for the progress of carbonation in isothermal conditions, and also with variable temperature, namely on cooling carbonate free materials from high temperatures, or on re-heating under CO2.
I. Antunes, G.C.Mather, J.R.Frade, J.Gracio, D.P.Fagg, Journal of Solid State Chemistry 183 (2010) 2826–2834

A2321 – The first 3D malonate bridged copper [Cu(O2C–CH2–CO2H)2 2H2O]: Structure, properties and electronic structure

A new inorganic-organic compound [Cu(O2C–CH2–CO2H)2·2H2O] ([Cumal]) was hydrothermally synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffraction. [Cumal] is the first three-dimensional compound existing in the system Cu(II)–malonic acid–H2O. Its framework is built up through carboxyl bridged copper where CuO6 octahedra are elongated with an almost D4h symmetry (4+2) due to the Jahn–Teller effect. The magnetic properties were studied by measuring its magnetic susceptibility in the temperature range of 2–300 K indicating the existence of weak ferromagnetic interactions. The electronic structure of [Cumal] was calculated within the density functional theory (DFT) framework. Structural features are well reproduced using DFT structural optimizations and the optical spectra, calculated within the dielectric formalism, explain very well the light blue colour of the compound. It is shown that a GGA+U approach with a Ueff value of about 6 eV is necessary for a better correlation with the experiment
A. Seguatni, M.Fakhfakh, L.S.Smiri, P.Gressier, F.Boucher, N.Jouini, Journal of Solid State Chemistry 187 (2012) 7–14

A2303 – Structural evolution in nanoporous anodic aluminium oxide

Nanoporous and self-organized layers of aluminium alloys are used in many applications as membranes, templates for nanometric objects or corrosion protection for aluminium alloys. The use of this nanometric structure widely remains empirical, especially in the case of very small pores (<20 nm). The objective of this study is to present the structural evolution of nanoporous anodic aluminium oxide during “sealing” processes and ageing on aluminium alloy. The probing on the chemical bonding environment of aluminium by XANES spectroscopy, combined with different analytical techniques demonstrate that the oxide structure is constituted by 2/3 of aluminium in tetrahedral coordination 1/3 in octahedral coordination and sulphate species. In contact with water electrolyte, the hydrolysis of AlO4 into AlO6 cluster and a partial release of sulphate ions are an important chemical transformation of the amorphous structure. This structural transformation defines the chemistry (pH and surface charge) inside the nanopores, the ageing behaviour and the possible incorporation or diffusion of chemical species in the nanostructure.
Emmanuel Rocca, Delphine Vantelon, Solenn Reguer, François Mirambet, Materials Chemistry and Physics 134 (2012) 905-911

A2294 – Insights into high temperature oxidation of Al2O3-forming Ti3AlC2

Insights into high temperature oxidation of Al2O3-forming Ti3AlC2 are made to understand the sub-parabolic oxidation rate and the absence of Al-depletion zone beneath the protective Al2O3 scale. The scale results from selective oxidation of Al that migrated from Ti3AlC2 according to Ti3AlC2 + 3/2y O2 ? Ti3Al1?yC2 + 1/2y Al2O3, leaving Al vacancy in the substrate. Inward diffusion of oxygen via grain boundaries of the Al2O3 scale predominates for the scale growth. The Al2O3 grains grow with time, yielding sub-parabolic oxidation kinetics. The Al diffuses in a fast manner, accounting for the absence of Al-depletion zone.
X.H. Wang, F.Z. Li, J.X. Chen, Y.C. Zhou, Corrosion Science 58 (2012) 95–103

A2286 – A novel approach to determine oxidation kinetics of Mo–16Cr–xSi(x = 4–6 wt.%) alloy using stepwise isothermal thermo-gravimetry

A new method was developed for measuring the kinetics of oxidation. In this method, apparent activation energy and the exponent related to the oxidation phenomena can be evaluated by conducting a single experiment. The method was tested for its applicability by measuring the activation energy for oxidation of pure Mo. It was found that the isothermal weight change data of Mo from stepwise isothermal thermo-gravimetry (SITG) could be well analyzed to get kinetics parameters according to the empirical rate equation. Further, the method was extended for evaluating the oxidation kinetics parameters for Mo–16Cr–(4–6 wt.%)Si alloys. Effects of concentration of Si on the oxidation behaviors of the alloys were also studied.
Bhaskar Paul, S. Koley, A.K. Suri, Thermochimica Acta 549 (2012) 57– 62

A2285 – Al2TeO6: Mechanism of phase formation and dielectric properties

Low-loss dielectrics with low sintering temperatures will facilitate microelectronics to reach the high levels of integration that wireless communications currently require. In this work the phase-formation mechanism of 1:1 Al2O3–TeO2 is proposed. It is shown that TeO2 oxidation, which occurs in air at >600 °C to form Te4O9 and TeO3, triggers Al2TeO6 formation. The dielectric permittivity of Al2TeO6 was calculated to be ?22 at 1 MHz. Al2TeO6 is a promising material for ceramic bodies or substrates for dielectric applications,
Xinming Su, Aiying Wu, Paula M. Vilarinho, Scripta Materialia 67 (2012) 927–930

A2284 – Preparation and evaluation of Ca3?xBixCo4O9?? (0< x ? 0.5) as novel cathodes for intermediate temperature-solid oxide fuel cells

The misfit compounds Ca3?xBixCo4O9?? (x = 0.1–0.5) were successfully synthesized via conventional solid state reaction and evaluated as cathode materials for intermediate temperature-solid oxide fuel cells. The powders were characterized by X-ray diffraction, scanning emission microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and oxygen-temperature programmed desorption. The monoclinic Ca3?xBixCo4O9?? powders exhibit good thermal stability and chemical compatibility with Ce0.8Sm0.2O2?? electrolyte. Among the investigated single-phase samples, Ca2.9Bi0.1Co4O9?? shows the maximal conductivity of 655.9 S cm?1 and higher catalytic activity compared with other Ca3?xBixCo4O9?? compositions. Ca2.9Bi0.1Co4O9?? also shows the best cathodic performance and its cathode polarization resistance can be further decreased by incorporating 30 wt.% Ce0.8Sm0.2O2??. The maximal power densities of the NiO/Ce0.8Sm0.2O2?? anode-supported button cells fabricated with the Ce0.8Sm0.2O2?? electrolyte and Ca2.9Bi0.1Co4O9?? + 30 wt.% Ce0.8Sm0.2O2?? cathode reach 430 and 320 mW cm?2 at 700 and 650 °C respectively.
Jing Zou, Jungdeok Park, Heechul Yoon, Taewook Kim, Jongshik Chung, International Journal of Hydrogen Energy 37 (2012) 8592-8602

A2282 – Remarkable oxygen adsorption/desorption capability of Y0.5Tb0.5BaCo4O7+? under temperature cycles

When the Y0.5Tb0.5BaCo4O7+d ceramic powder is heated to 200–380 8C in oxygen atmosphere, it can adsorb oxygen remarkably. The adsorbed oxygen could be released by raising temperature over 420 8C or by switching the atmosphere from oxygen to nitrogen. In a temperature cycle between 360 8C and 440 8C, the relative mass change of the Y0.5Tb0.5BaCo4O7+d sample can reach 4.4% of its original mass, and shows high efficiency and stable oxygen adsorption/desorption reproducibility. However, the oxygen adsorption/desorption efficiency in the cycles switched between oxygen and nitrogen atmosphere is poor. The large adsorption capacity, the fast adsorption/desorption speeds, and the easy regeneration of Y0.5Tb0.5BaCo4O7+d absorbent under temperature cycles make it to be a highly potential candidate in air separation and oxygen removal.
Hongzhang Song, Jianfeng Jia, Sumei Zhang, Delin Yang, Hongwei Sun, Xing Hu, Materials Research Bulletin 47 (2012) 518–520

A2278 – Effect of twins in Ni substrates on the microstructure of La2Zr2O7 films for coated conductors

La2Zr2O7 (LZO) films were deposited by chemical solution deposition on Ni95Wi5 Rolling Assisted Bi-axially Textured substrates to be used in YBa2Cu3O7 (YBCO) coated conductors. These LZO films were proved of good qualities for YBCO deposition by Metal Organic Chemical Vapour Deposition that is an economic process. The mosaic of LZO films is only slightly degraded by the process of grain-to-grain epitaxial transfer (16% with respect to that of the substrate). The film is composed of small crystallites (20 - 40 nm) and larger anomalous crystallites (100 - 400 nm) found in great number in transferred twins from the substrate. The anomalous crystallites are poorly crystallised or amorphous and contain more C than areas with normal crystallites. High temperature in-situ X ray shows a sudden crystallisation at 860°C that does not seems to involve a solid state reaction. The anomalous crystallites are analysed to result from a locally enhanced barrier to nucleation and might reveal sor characteristics of the crystallization.
Sarah Petit, Sébastien Pairis, Mélissa Mikolajczyk, Luc Ortega, Jean-Louis Soubeyroux, Philippe Odier, Thin Solid Films 531 (2013) 545–551

A2277 – Thermal stability of magnetron sputtered Si–B–C–N materials at temperatures up to 1700 °C

Thermal stability of deposited Si–B–C–N materials (film fragments or powders without a substrate) in inert gases (He and Ar) up to 1700 °C was investigated using differential scanning calorimetry, high-resolution thermogravimetry and X-ray diffraction measurements. Amorphous Si–B–C–N films were fabricated by dc magnetron co-sputtering of a single B4C–Si target in two nitrogen–argon gas mixtures (50% N2 + 50% Ar or 25% N2 + 75% Ar). It was found that the deposited Si–B–C–N materials can be more stable at high temperatures in the inert atmosphere than the usually used substrates (e.g. SiC or BN). The materials with the compositions (in at.%) Si32–33B10C2N50–51, for which N/(Si + B + C) = 1.1–1.2, retained their amorphous structure up to 1600 °C without any structural transformations and detectable mass changes.
P. Zeman, J. ?apek, R. ?erstvý, J. Vl?ek, Thin Solid Films 519 (2010) 306–311

A2276 – Pulsed reactive magnetron sputtering of high-temperature Si–B–C–N films with high optical transparency

Multifunctional Si–B–C–N films with exceptionally high thermal stability are becoming increasingly attractive because of their potential applications in coating technologies, and in high-temperature electronics and optoelectronics. In the present work, amorphous Si–B–C–N films were deposited onto SiC and Cu floating substrates using pulsed dc magnetron co-sputtering of a single (B4C)25Si75 target in a 50% Ar + 50% N2 gas mixture. High-quality defect-free films with smooth surfaces (average roughness Ra = 4 nm) were produced. The films, possessing a composition (in at.%) of Si30–32B10–12C2–4N49–51, exhibited a hardness of 22 GPa, an effective Young's modulus of 170 GPa and an elastic recovery of 75%. The oxidation resistance of the Si–B–C–N films in air was found to be very high up to 1600 °C. The film materials retained their amorphous structure after annealing in inert gases (He and Ar) up to 1600 °C. Annealing of the as-deposited films in He from room temperature to 1400 °C led to a slight decrease in the refractive index from 1.92 to 1.91 and to an accompanying increase in the extinction coefficient from 3 × 10? 4 to 3 × 10? 3 (both at the wavelength of 550 nm).
J. Vl?ek, P. Calta, P. Steidl, P. Zeman, R. ?erstvý, J. Houška, J. Kohout

A2275 – Microstructure characterization of high-temperature, oxidation-resistant Si-B-C-N films

In this work, we have employed high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and nano indentation to study the microstructure and the mechanical properties of Si-B-C-N films treated at high temperatures. Si-B-C-N films with a chemical composition of Si30–32B10–12C2–4N49–51 were deposited in a 50% Ar/50% N2 gas mixture by pulsed DC magnetron sputtering. In order to study the microstructure at elevated temperatures of the films, they were subjected to annealing at temperatures up to (i) 1400 °C in He and (ii) 1700 °C in air. XPS studies showed that annealing to 1400 °C in He does not affect the chemical composition of the film, while annealing to 1700 °C in air results in the oxidation of the film via the loss of N and B and formation of SiOx. HRTEM studies demonstrated that the as-deposited film and the film annealed to 1400 °C in He are amorphous. A three-layer structure was found in the film annealed to 1700 °C in air: the original amorphous Si-B-C-N base-layer, a transition nanocomposite layer consisting of BN nanocrystals embedded in a SiOx amorphous matrix and an amorphous SiOx top layer. The present evidence suggests that O reacts with Si in the Si-B-C-N amorphous structure resulting in the formation of SiOx and concomitant nucleation of BN crystals at the base/transition layer interface. Nano-indentation tests show that the film annealed to 1400 °C in He has a hardness of 22.1 GPa and a modulus of 210.8 GPa, higher than that of the as-deposited film (19.5 and 204.9 GPa), whereas the values for the film annealed to 1700 °C in air (9.8 and 76.5 GPa) simply reflect those of the SiOx top layer. The high oxidation resistance of the films is attributed to the presence of BN in front of the base layer interface that can act as a barrier to O diffusion.
Jie He, Minghui Zhang, Jiechao Jiang, Jaroslav Vl?ek, Petr Zeman, Petr Steidl, Efstathios I. Meletis, Thin Solid Films 542 (2013) 167–173

A2273 – Nanocrystalline magnetite and Mn–Zn ferrite particles via the polyol process: Synthesis and magnetic properties

Nanocrystalline Fe3O4 and Mn–Zn ferrite powders with crystallite sizes of 10 and 7 nm, respectively, and narrow size distribution were synthesized in a triethylene glycol medium. Mn–Zn ferrite particles with crystallite size of 9 and 12 nm were obtained after annealing of the as prepared ferrite particles at 300 and 500 °C, respectively. The saturation magnetization at 5 K of the Mn–Zn ferrite obtained at 300 °C (79 emu g?1) is smaller than that of the bulk material. Hysteresis loop measurements indicate ferrimagnetic behavior at 5 K and superparamagnetic behavior at 295 K. The Mn–Zn ferrite nanocrystals obtained at 500 °C, however, exhibit a smaller Ms compared to the ferrite annealed at 300 °C indicating a change in the cation distribution.
J. Töpfer, A. Angermann, Materials Chemistry and Physics 129 (2011) 337– 342

A2267 – Amorphous Boron containing silicon carbo-nitrides created by ion sputtering

Silicon carbo-nitride films with Boron were deposited onto Silicon, glass and SS304 Stainless Steel substrates using the ion beam assisted deposition (IBAD) method. The coating composition, rate of ion-assistance and substrate temperature were varied. Films were examined by X-Ray Diffraction, Scanning Electron microscopy, Energy Dispersive X-Ray analysis, Cathodoluminescence, Atomic Force Microscopy and Nano-indentation. The composition and chemical bonding variation was found to be dependent on deposition conditions. All coatings were amorphous, fully dense and showed high hardness up to 33 GPa. It is suggested that the low friction coefficient of about 0.3, measured against Al2O3 using the pin-on-disc method, may be the result of the presence of C nanoclusters which are formed under the low energy deposition conditions. Films deposited on Stainless Steel had an onset of rapid thermal oxidation at 1150 °C in air as determined by thermogravimetric analysis. The films have a Tauc bandgap between 2.2 and 2.8 eV and were also exceptionally high electrical resistive which may indicate the presence of localised states.
V.M. Vishnyakov, A.P. Ehiasarian, V.V. Vishnyakov, P. Hovsepian, J.S. Colligon, Surface & Coatings Technology 206 (2011) 149–154

A2265 – Oxidation of ??-aluminium oxynitride

The oxidation in air of single crystal ??-aluminium oxynitride (AlON) grains has been characterized by thermogravimetry and X-ray diffraction in the 1273–1673 K range. Two oxidation stages have been observed, suggesting the formation of a transitional phase. Below 1473 K, oxidation results in the apparition of platelets and noodle-like crystals on the surface of the initially faceted single crystals. Above 1473 K, low density ?-alumina polycrystals start forming on the grain surface and grow towards the grain core with increasing temperature or time. Their low density is mainly due to the presence of a network of nano-porosities.
E. Xolin, Y. Jorand, C. Olagnon, L. Gremillard, Corrosion Science 53 (2011) 939–945

A2248 – Effect of rotation of feed and seed rods on the quality of Na0.75CoO2 single crystal grown by traveling solvent floating zone method

High purity Na0.75CoO2 single crystals have been grown by floating zone method. We found the rotation of feed and seed rods play a crucial role in growing high quality single crystal. Systematic investigations suggest the occurrence of a phase separation at microscopic level, such as the separation into Na-rich and Na-poor domains during the growth, and formation of impurity phase(s) depending on growth conditions. NaxCoO2 (x = 0.30, 0.60) crystals have been prepared by sodium deintercalation from Na0.75CoO2. Powder X-ray and energy dispersive X-ray analyses have confirmed the phase purity and homogeneity of the samples. Magnetic susceptibility measurements of x = 0.60 and 0.75 crystals indicate a bulk phase transition at 22 K and an anomaly around 339 K and 334 K respectively which are attributed to structural transition. In addition some unique features related to Na0.60CoO2 were observed
C. Sekar, S. Paulraj, P. Kanchana, B. Schüpp-Niewa, R. Klingeler, G. Krabbes, B. Büchner, Materials Research Bulletin 46 (2011) 675–681

A2247 – Studies on Formation and Decomposition of the Layered Cobaltite LixNayCoO2

Lithium-sodium cobaltite LixNayCoO2 () with ordered layered structure is promising thermoelectric material. Here we report the peculiarities of this phase formation and decomposition processes studied by TG/DTA, XRD, SEM, and TEM methods. Significant weight loss resulting from oxygen liberation and endothermic effect at °C are the main features of the LixNayCoO2 formation. Decomposition of the ordered phase is accompanied by exothermic effect at °C and the weight increase. Electron microscopic study shows that the lithium-sodium cobaltite decomposes into LiCoO2 and ?-Na0.7CoO2. Lattices of the initial phase and formed ones demonstrate mutual orientation.
A. S. Semenova, R. F. Samigullina, E. V. Shalaeva, N. I. Kourov, D. G. Kellerman, International Journal of Inorganic Chemistry Volume 2011, Article ID 649183

A2244 – Effect of oxygen vacancy variation on the photo-assisted degradation and structural phase transition of oxygen defective Ba(Fe,Co)O3 x

The different effect of oxygen vacancy variation on photo-assisted degradation effect and structural phase transition of oxygen defective Ba(Fe,Co)O3?x in dye degradation were investigated via comparative studies. The samples of perovskite BaFeO3?x and BaCoO3?x were synthesized at 700 °C by citrate sol–gel method. Samples synthesized above 700 °C show oxygen deficiency. With oxygen vacancy increasing, the BaFeO3?x becomes instable, whereas BaCoO3?x improves the stability. The instability is due to CO2 adsorption activity of oxygen vacancies, and then this may make negative effects on their photo-assisted degradation effect. So finally, the oxygen vacancies take different effects on photo-assisted degradation effect of Ba(Fe,Co)O3?x.
Mengmeng Sun, Yinshan Jiang, Fangfei Li, Maosheng Xia, Bing Xue, Darui Liu, Materials Research Bulletin 46 (2011) 801–809

A2229 – Thermochemical characterisation of the calcination process step in the sulphate method for production of titanium dioxide

Calcination is the last process step of the sulphate method for production of titanium dioxide. The chemical reactions that occur during calcination are analysed by means of simultaneous DTA-TG-MS-measurements in order to provide a 5-step reaction schematic. The corresponding enthalpies of reaction are determined calorimetrically by means of the reversed drop method. The developed schematic is suitable for process modelling purposes.
T. Ginsberg, M. Modigell, W. Wilsmann, Chemical Engineering Research and Design 8 9 ( 2 0 1 1 ) 990–994

A2228 – Cr-doped perovskite and rutile pigments derived from industrial by-products

In order to enhance the use of environment-friendly materials and to stimulate waste recycling, this work has developed brown-maroon inorganic pigments belonging to rutile (TiO2) and perovskite (CaTiO3) structures. They were obtained by solid state reaction of industrial residues mixtures: tionite (i.e. insoluble residue of titania slag processing), Cr/Ni plating sludge and marble cutting/sawing sludge, for sake of comparison, analogous formulations were prepared by using reagent-grade precursors. Chromium-doped (0.04 mole of Cr2O3) perovskite and rutile pigments were obtained at 1200 °C and their phase composition, microstructure, optical properties and technological behaviour were characterized by XRD, SEM, DRS and application in glazes, respectively. The presence of impurities (e.g. Fe, Ni, Al, Si) in the wastes induced the crystallization of secondary phases, like wollastonite (CaSiO3) and titanite (CaTiSiO5), whose occurrence slightly shaded off the final colouration of the waste-based pigments; a further addition of chromium is required to improve their colouring power in transparent glazes. The diffuse reflectance spectroscopy shows that the colour development, in both structures, is due to the partial substitution of titanium by chromium in octahedral coordination.
W. Hajjaji, C. Zanelli, M.P. Seabra, M. Dondi, J.A. Labrincha, Chemical Engineering Journal 171 (2011) 1178– 1184

A2227 – Synthesis and properties of mullite-type (Bi(1?x)Srx)2(M1(1?y)M2y)4O(9?x) (M = Al, Ga, Fe)

Mullite-type A2M4O9 phases (M = Al, Ga, Fe), representing promising oxygen conducting materials for solid oxide fuel cells (SOFCs), were synthesized using the glycerine- and the EDTA/citric acid synthesis method. For strontium-doped material pure phases could be obtained only by washing the samples after the heating in both synthesis methods. Temperature dependent investigations were carried out to show the influence of the metal atoms on the structural stability and thermal expansion coefficients. Whereas the Sr-free phases show a quasi linear thermal expansion behavior in all three directions up to their incongruent melting points, a discontinuity in the measured range is observed for the investigated strontium doped dibismuth-nonaoxotetrametallate(III) caused by the decomposition into Bi2M4O9, strontium metallates and bismuthoxide. Big single crystals were only observed for the Sr-free compound, of which the structure of Bi2(Ga0.45Fe0.55)4O9 will be presented here in the Bärnighausen tree corresponding mullite-type setting
Thorsten M. Gesing, Reinhard X. Fischer, Manfred Burianek, Manfred Mühlberg, Tapas Debnath, Claus H. Rüscher, Jan Ottinger, J.-Christian Buhl, Hartmut Schneider, Journal of the European Ceramic Society 31 (2011) 3055–3062

A2223 – Preparation of Ni-doped ZnO ceramics for thermoelectric applications

Zn1?xNixO dense ceramics were prepared from Zn1?xNixO nanoparticles with x varying from 0 to 0.06. These nanoparticles were synthesized by liquid route. In the sintered samples, the solubility limit of Ni in the Zn1?xNixO wurtzite structure was found to be 0.03. The increase of x until 0.03 led to a significant raise in both electrical conductivity (?) and absolute value of Seebeck coefficient (|S|). Ni-richer samples (x > 0.03) contained in addition a small amount of Ni rich secondary phase (ZnyNizO) with a cubic structure similar to NiO. The thermoelectric properties of all samples were investigated from room temperature to 1000 K. All doped samples showed a n-type semiconducting conductivity. For Ni contents higher than x = 0.03, the increase of the secondary phase content induced a decrease in ? and |S|. The highest power factor (0.6 mW m?1 K?2) and ZT (0.09) were found for Zn0.97Ni0.03O at 1000 K.
H. Colder, E. Guilmeau, C. Harnois, S. Marinel, R. Retoux, E. Savary, Journal of the European Ceramic Society 31 (2011) 2957–2963

A2206 – Thermochemistry of La0.7Sr0.3Mn1?xFexO3 solid solutions (0

The structure, the energetics and the internal redox reactions of La0.7Sr0.3FexMn1?xO3 have been studied in the complete solid solution range 0.0
Nihan Kemika, Yayoi Takamura, Alexandra Navrotsky, Journal of Solid State Chemistry 184 (2011) 2118–2123

A2198 – High-temperature electron–hole transport in PrBaCo2O5+?

The oxygen content, conductivity and thermopower in the double perovskite-like cobaltite PrBaCo2O5+? are reported in the oxygen partial pressure range 2×10?6–0.21 atm and temperatures between 650 and 950 °C. The electrical properties are shown to be continuous through the transition from ?>0.5 to ?<0.5. The variations of transport parameters with temperature and oxygen content reveal hole polaron hopping conduction within oxygen non-stoichiometry domain ?<0.5.
A.Yu. Suntsov, I.A.Leonidov,M.V.Patrakeev,V.L.Kozhevnikov, Journal of Solid State Chemistry 184 (2011) 1951–1955

A2193 – Ordered mesoporous silicoboron carbonitride ceramics from boron-modified polysilazanes: Polymer synthesis, processing and properties

Ordered two-dimensional (2D) mesoporous silicoboron carbonitride (SiBCN) ceramics were prepared by a nanocasting approach of a boron-modified polysilazane of the type [B(C2H4SiCH3NH)3]n (C2H4 = CHCH3, CH2CH2) ([Si3B1.1C10.5N3.0H25.5]n) using mesoporous CMK-3 carbon as hard template. The polymer was synthesized according to a monomer route by hydroboration of CH2 = CHSiCH3Cl2 followed by reaction of the as-made tris(dichloromethylsilylethyl)borane (B(C2H4SiCH3Cl2)3 (TDSB, C2H4 = CHCH3, CH2CH2) with lithium amide (LiNH2). It was generated as a highly soluble compound which could easily impregnate mesoporous CMK-3 carbon. The derived [B(C2H4SiCH3NCH3)3]n-carbon composite was directly pyrolyzed in flowing nitrogen at 1000 °C to generate a SiBCN-carbon composite. The carbon template was subsequently removed through thermal treatment at 1000 °C in a mixture of ammonia and nitrogen to generate ordered mesoporous Si3.0B1.0C4.2N2.4 structures. XRD and TEM analyses revealed that the obtained amorphous mesoporous ceramic exhibits open, continuous, and ordered 2D hexagonal frameworks which are strongly dependent on the number of impregnation cycles and the carbon removal step. Using a double impregnation cycle combined with a pyrolysis process up to 1000 °C in flowing nitrogen and a carbon removal step at 1000 °C for 3 h in a volumetric flow ratio between ammonia and nitrogen of 1, the ordered mesoporous SiBCN ceramic displays high surface area (630 m2 g?1), high pore volume (0.91 cm3 g?1), and narrow pore-size distribution (around 4.6 nm) with a thermal stability which extends up to 1180 °C under nitrogen.
Olivier Majoulet, Johan G. Alauzun, Laura Gottardo, Christel Gervais, Manfred E. Schuster, Samuel Bernard, Philippe Miele, Microporous and Mesoporous Materials 140 (2011) 40–50

A2184 – Effect of Al–Cr doping on the structural,magnetic and dielectric properties of strontium hexaferrite nanomaterials

Nanosized strontium hexaferrite doped with a binary mixture of Al–Cr at the iron site is synthesized by the chemical co-precipitation method. The hexagonal phase and the nominal composition of the synthesized nanomaterials are confirmed by X-ray diffraction and energy dispersive X-ray fluorescence analyses. The crystallite size is found in the range of 14–30 nm, which is small enough to obtain a suitable signal-to-noise ratio in high density recording media. The average grain size of the material is found in the range of 40–85 nm as determined by scanning electron microscopy. The magnetic properties, such as saturation magnetization, remanence and coercivity, are calculated from hysteresis loop measurement, and the value of the magnetic moment is also calculated from the saturation magnetization data. All the magnetic properties are found to decrease with the increase in Al–Cr content, which is due to the occupation of the doped cations at the octahedral sites (12k and 2a) having spin of electrons in upward direction. The variation in the dielectric constant and dielectric loss factor with frequency is discussed on the basis of Wagner and Koop’s theory. It is found that the dielectric constant decreases with the increase in Al–Cr content, which suggests that the doped nanomaterials are suitable for applications in microwave devices.
Muhammad Naeem Ashiq, Muhammad Javed Iqbal, Iftikhar Hussain Gul, Journal of Magnetism and Magnetic Materials 323 (2011) 259–263

A2177 – Cation disorder in NaW2O6+?·nH2?zO post-ion exchange with K, Rb,Sr,andCs

The structure of the defect pyrochlore NaW2O6+?·nH2?zO after ion exchange with K, Rb, Sr or Cs for Na has been investigated using thermal analysis, solid-state nuclear magnetic resonance, laboratory X-ray and neutron diffraction methods. Neutron diffraction studies show that both the A-type cations (Na+, K+, Rb+, and/or Cs+) and the water molecules reside within the channels that form in the 111 direction of the W2O6 framework and that these strongly interact. The analytical results suggest that the water and A-type cations compete for space in the tunnels within the W2O6 pyrochlore framework, with the total number of water molecules and cations being approximately constant in the six samples investigated. The interplay between the cations and water explains the non-linear dependence of the a lattice parameter on the choice of cation. It appears that the ion-exchange capacity of the material will be controlled by the amount of water initially present in the sample
Gordon J.Thorogood, Brendan J. Kennedy, Maxim Avdeev, Vanessa K. Peterson, John V. Hanna, Vittorio Luca, Journal Physics and Chemistry of Solids 72 (2011) 692–700

A2176 – Crack severity in relation to non-homogeneous Ni oxidation in anode-supported solid oxide fuel cells

The full oxidation of Ni–YSZ anode-supported cells at high temperatures (>700 °C) is shown here to lead to much more severe degradation (larger quantity and wider cracks in the electrolyte) than at lower temperatures. This correlates with the linear mass gain/time profile observed in TGA experiments at high temperatures, indicative of diffusion controlled Ni oxidation and thus the presence of O2 (and Ni/NiO) concentration gradients into the depth of the anode layer. At low partial pressures of O2, the severity of cracking also increases. SEM studies of partially oxidized anode layers confirmed that Ni oxidation is non-homogeneous when carried out at either high temperatures or low pO2, in which case the outer regions of the anode (near the anode/air interface) become almost fully oxidized, while the inner regions (near the electrolyte) remain metallic. Under these conditions, the continued volume expansion associated with NiO formation can then only occur towards the electrolyte, increasing the compressive stress inside the anode as the Ni continues to be oxidized, leading to electrolyte cracking and warping (convex to the electrolyte). To prevent severe degradation to the cell, efforts should therefore be made to avoid gradients in NiO/Ni content during oxygen exposure of Ni–YSZ anode-supported cells at high temperatures.
J.L. Young, V.I. Birss, Journal of Power Sources 196 (2011) 7126– 7135

A2175 – Structure, crystal chemistry and magnetism of rare earth calcium-doped cobaltates: Ln2?xCaxCoO4+? (Ln ¼ Pr, Nd, Sm, Eu and Gd)

Single-phase samples of Ln2?xCaxCoO4+? (Ln = Pr3+ ? Gd3+) around x?1 have been prepared. For the first time, the phase field for these compounds has been defined using powder X-ray diffraction and a very narrow solid solution was observed. Under our synthetic conditions, the K2NiF4 structure was not formed for the large La3+ ion, or for compositions containing the smaller rare earths ions (
Gordon J. Thorogood, Pierre-Yves Orain, Mickael Ouvry, Bruno Piriou, Tony Tedesco, Kia S. Wallwork, Jan Herrmann, Michael James, Solid State Sciences 13 (2011) 2113-2123

A2172 – Investigations on synthesis of ZrB2 and development of new composites with HfB2 and TiSi2

This paper presents the results of experimental investigations carried out on the synthesis of pure ZrB2 by boron carbide reduction of ZrO2 and densification with the addition of HfB2 and TiSi2. Process parameters and charge composition were optimized to obtain pure ZrB2 powder. Monolithic ZrB2 was hot pressed to full density and characterized. Effects of HfB2 and TiSi2 addition on densification and properties of ZrB2 composites were studied. Four compositions namely monolithic ZrB2, ZrB2 + 10% TiSi2, ZrB2 + 10% TiSi2 + 10% HfB2 and ZrB2 + 10% TiSi2 + 20% HfB2 were prepared by hot pressing. Near theoretical density (99.8%) was obtained in the case of monolithic ZrB2 by hot pressing at 1850 °C and 35 MPa. Addition of 10 wt.% TiSi2 resulted in an equally high density of 98.9% at a lower temperature (1650 °C) and pressure (20 MPa). Similar densities were obtained for ZrB2 + HfB2 mixtures also with TiSi2 under similar conditions. The hardness of monolithic ZrB2 was measured as 23.95 GPa which decreased to 19.45 GPa on addition of 10% TiSi2. With the addition of 10% HfB2 to this composition, the hardness increased to 23.08 GPa, close to that of monolithic ZrB2. Increase of HfB2 content to 20% did not change the hardness value. Fracture toughness of monolithic sample was measured as 3.31 MPa m1/2, which increased to 6.36 MPa m1/2 on addition of 10% TiSi2. With 10% HfB2 addition the value of KIC was measured as 6.44 MPa m1/2, which further improved to 6.59 MPa m1/2 with higher addition of HfB2 (20%). Fracture surface of the dense bodies was examined by scanning electron microscope. Intergranular fracture was found to be a predominant mode in all the samples. Crack propagation in composites has shown considerable deflection indicating high fracture toughness. An oxidation study of ZrB2 composites was carried out at 900 °C in air for 64 h. Specific weight gain vs time plot was obtained and the oxidized surface was examined by XRD and SEM. ZrB2 composites have shown a much better resistance to oxidation as compared to monolithic ZrB2. A protective glassy layer was seen on the oxidized surfaces of the composites.
J.K. Sonber, T.S.R. Ch. Murthy, C. Subramanian, Sunil Kumar, R.K. Fotedar, A.K. Suri, Int. Journal of Refractory Metals and Hard Materials 29 (2011) 21–30

A2170 – Effects of the nature of the doping salt and of the thermal pre-treatment and sintering temperature on Spark Plasma Sintering of transparent alumina

A slurry of ?-Al2O3 was doped with Mg, Zr and La nitrates or chlorides, in various amounts in the range 150–500 wt ppm and then freeze-dried to produce nanosized doped powder (?150 nm). The powder was sintered by SPS to yield transparent polycrystalline alpha alumina. The influence of the nature of the doping element and the starting salt, the thermal treatment before sintering and the sintering temperature on the transparency of the ceramics were investigated. The transparency of the ceramics of nanosized Al2O3 was shown to depend mainly on the way the powder was prepared, the nature of the doping salt also had an effect. Finally, a high real inline transmittance, reaching 48.1% was achieved after optimization.
Nicolas Roussel, Lucile Lallemant, Bernard Durand, Sophie Guillemet, Jean-Yves Chane Ching, Gilbert Fantozzi, Vincent Garnier, Guillaume Bonnefont, Ceramics International 37 (2011) 3565–3573

A2168 – The oxidation behaviour of uniaxial hot pressed MoSi2 in air from 400 to 1400 C

MoSi2 samples were prepared by hot uniaxial pressing from a 2 mm grain-size powder of commercially available MoSi2. The oxidation behaviour of MoSi2 was systematically studied from 400 C to 1400 C, which includes the pest-oxidation temperature range. It was observed that the rate and mechanism for oxidation of MoSi2 change significantly with increasing temperature. Five temperature regimes have to be considered regarding both kinetic results and cross-sections: i) 400 < T < 550 C; ii) 550 T < 750 C; iii) 750 T < 1000 C; iv) 1000 T < 1400 C; v) T 1400 C. In the first range, pesting did not occur in samples that were free of cracks and residual stresses and the oxidation kinetics were governed by surface or phase boundary reactions. Above 550 C, there was a change in the physical properties of the oxidation products due to the evaporation of MoO3. The formation of Mo5Si3 was observed above 800 C showing that the thermodynamic previsions were satisfied above this temperature. At higher temperatures (>1000 C), the oxide scale became very protective and transport in the silica scale (amorphous and b cristobalite) governed the oxidation kinetics. The Mo5Si3 phase did not appear anymore at 1400 C, indicating that another oxidation mechanism has to be proposed.
S. Knittel, S. Mathieu, M. Vilasi, Intermetallics 19 (2011) 1207-1215

A2165 – Catalysis of the hydrogen oxidation reactions by Sr-doped LaMn1?yCryO3±? oxides

Sr-doped and Sr-free La1 ? xSrxMn1 ? yCryO3 ± ? (LSMC, x(Sr) = 0–0.2, y(Cr) = 0.4–0.6) perovskite-type oxides were synthesized and evaluated as single phase anodes for use in intermediate temperature solid oxide fuel cell applications. Their thermo-chemical and chemical stabilities were investigated in hydrogen at high temperatures and correlated with their oxygen non-stoichiometry (3 ± ?), determined by permanganate titration. The catalytic activity towards hydrogen oxidation was examined as a function of oxide sintering time, operating temperature, and the Sr and Cr contents, using a Pt mesh current collector. While all of the perovskite oxides studied here showed some irreversible performance degradation with time under both open circuit and anodically polarized conditions, La0.9Sr0.1Mn0.6Cr0.4O3.03 (LSMC9164), sintered at 1200 °C for 10 h, was found to be the most catalytically active and also the most stable.
L. Deleebeeck, V. Birss, Solid State Ionics 203 (2011) 69–79

A2162 – Cationic doping effect on the structural, magnetic and spectroscopic properties of delafossite oxides CuCr1?x(Sc,Mg)xO2

This article reports the effect of Sc and (Sc + Mg) substitution on the structural and physical properties of delafossite-type CuCrO2 oxide. X-ray diffraction and Raman spectroscopy show that the structure is maintained for 10% Sc and (10% Sc + 4% Mg) substitutions for chromium. The incorporation of these elements generates very anisotropic microstrains in the structure. Strain also increases with oxygen intercalation, probably because a non-uniform distribution of intercaled oxygen. Thermal stability in oxygen was found to decrease with increasing the M3+ cation size. The evolution of relative intensities of Raman bands points towards an increase in lattice distortion with substitution, in agreement with ionic radii considerations. Comparing the substitution effect of Mg2+ to those of the nonmagnetic Sc3+, magnetization around the AF transition does not seem to correlate with randomness and lattice parameter but with itinerancy of the doped hole.
M. Amami, S. Smari, K. Tayeb, P. Strobel, A. Ben Salah, Materials Chemistry and Physics 128 (2011) 298–302

A2160 – A sol–gel route to nanocrystalline TiN coated cubic boron nitride particles

For the purpose of increasing microstructural homogeneity and enhancing the reinforcement-matrix interfacial area, cubic Boron Nitride, cBN particles were coated by nanocrystalline TiN by a sol–gel route that required neither the need for pH adjustment nor the use of surfactants or additives. Uniform shells of amorphous titania having thicknesses in the nanometers scale were formed on the surface of the cBN particles by hydrolysis and condensation reactions of titanium (IV) isopropoxide. The amorphous coated cBN powder was nitrided to crystalline TiN coated cBN by treating in NH3 gas at 900 °C. After nitridation the amorphous layer was completely converted to nanocrystalline TiN particles that uniformly covered the surface of cBN. Changes in the TiOx coated layer thickness and the size of the TiN particles were investigated as a function of alkoxide content. TiO2 nanoparticles were synthesized using the same reaction conditions, but without the presence of cBN. These nanoparticles were calcined in air at different temperatures (250–700 °C) and then nitrided at 900 °C. The nitridation behavior of TiO2 nanoparticles was studied as a function of calcination temperature.
Malik Adeel Umer, Hee Sub Park, Dong Ju Lee, Ho Jin Ryu, Soon Hyung Hong, Journal of Alloys and Compounds 509 (2011) 9764– 9769

A2147 – Tribological and oxidation behaviour of TiAlCN/VCN nanoscale multilayer coating deposited by the combined HIPIMS/(HIPIMS-UBM) technique

A TiAlCN/VCN nanostructured multilayer coating with a bi-layer thickness of 2.2 nm and a total thickness of 2.6 ?m was deposited by mixed High Power Impulse Magnetron Sputtering and Unbalanced Magnetron Sputtering (HIPIMS-UBM) technique. HIPIMS was utilized in both surface pretreatment as well as coating deposition steps. The ionic composition of the HIPIMS plasma as a function of discharge current was analysed by plasma sampling using energy-resolved mass spectrometery. The spectral intensities have shown high metal ion concentration of Ti+, V+, and Al+ in the plasma. A significant amount of C+ ions were also observed due to the decomposition of the reactive methane (CH4) gas. High ionisation of the condensing species resulted in formation of a highly dense microstructure. This was confirmed through the cross-sectional TEM analysis. Thermo-gravimetric analysis showed a significant rise in the onset of rapid oxidation temperature to ? 780 °C. In contrast, the carbon-free TiAlN/VN multilayer coating starts oxidising rapidly at 638 °C. Dry sliding wear tests were conducted on the coatings at room temperature and at elevated temperatures of 200 °C, 450 °C, and 650 °C. The friction coefficient was found to be ?=0.45 at room temperature, whereas the coefficient steadily decreased from 0.7 at 200 °C, to 0.5 at 450 °C and 0.4 at 650 °C respectively. Raman spectra taken in the wear track of the coating suggested the presence of Magneli phase oxides of the form, V2O5, VO2, TiO2, and AlVO4. These Raman results were compared with previously reported XRD studies performed on the oxidised surface of the TiAlCN/VCN coating at above mentioned consecutive temperatures.
G. Kamath, A.P. Ehiasarian, Y. Purandare, P.Eh. Hovsepian, Surface & Coatings Technology 205 (2011) 2823–2829

A2146 – Tailoring the properties of yttria-stabilized zirconia powders prepared by the sol–gel method for potential use in solid oxide fuel cells

Yttria-stabilized zirconia (YSZ) powders have been prepared by the sol–gel method, following two alternative procedures: a series of powders was obtained by drying the sol–gel solutions in air at 100 °C until dry residue, and another series of powders was obtained by scratching the thin films deposited on cylindrical wide flat glassy surfaces after evaporating to dryness in air at 100 °C for 2 h. Samples were characterized by Scanning Electron Microscopy (SEM), nitrogen adsorption at ?196 °C and Fourier Transform Infrared (FT-IR) spectroscopy. In general, a noticeable contraction of the pores is observed as the molecular size of the alcohols used grows. Powders prepared by conventional drying of sol–gel solutions at 100 °C exhibit remarkably high values of specific surface area (up to 148 m2 g? 1). On the contrary, samples prepared by scratching of the deposited thin films show a noticeable decrease in their specific surface area. Values of fractal dimension follow the same trend and indicate that, in general, the texture of the samples is mainly microporous for the first series of samples and more ordered for the second one. Finally, in order to investigate the effect of the calcination temperature on the morphological and textural properties of 3 mol% yttria-stabilized zirconia powders, once the 3YSZ powders were dried at 100 °C they were subjected to calcination at different temperatures. The experimental results suggest that the removal of residual water and alcohol occluded within the powder particles as well as the elimination of gases produced during the calcination stage play a very important role in the development of the porosity and surface area of the samples.
A. Díaz-Parralejo, E.M. Cuerda-Correa, A. Macías-García, M.A. Díaz-Díez, J. Sánchez-González, Fuel Processing Technology 92 (2011) 183–189

A2141 – Alumina foam catalyst supports for industrial steam reforming processes

The manufacture and the characterisation of alumina foams as alternative catalysts supports for industrial steam reforming processes are presented here. The possibility of use of alumina foams as catalysts supports in such processes is evaluated by studying their resistance toward mechanical and chemical stresses. The alumina foams produced are characterised owing to their processing parameters (slurry infiltration, sintering temperature, template pore size). Their ability to work in hydrothermal atmosphere is assessed by characterising the evolution of microstructures and mechanical strengths upon aging. Thermodynamic studies of the stability of alumina in industrial steam reforming working conditions are performed and correlated to the experiments to demonstrate the stability of such a system
Raphaël Faure, Fabrice Rossignol, Thierry Chartier, Claire Bonhomme, Alexandre Maître, Grégory Etchegoyen, Pascal Del Gallo, Daniel Gary, Journal of the European Ceramic Society 31 (2011) 303–312

A2136 – Pt and PtRu electrocatalysts supported on carbon xerogels for direct methanol fuel cells

Carbon xerogels (CXs) have been prepared by polycondensation of resorcinol and formaldehyde in water by the sol–gel method. Functionalization with diluted and concentrated nitric acid as oxidizing agents was carried out to create surface oxygen groups, acting as anchoring sites for metallic particles. Characterization techniques included nitrogen physisorption, scanning electron microscopy, temperature programmed desorption and temperature programmed oxidation. Functionalized xerogels were used as supports to synthesize Pt and PtRu electrocatalysts by a conventional impregnation method. Catalysts electrochemical activity towards the oxidation of methanol was studied by cyclic voltammetry and chronoamperometry to establish the effect of the surface chemistry on the catalysts synthesis. Carbon monoxide oxidation was also studied to determine the electrochemical active area and the CO tolerance of the as prepared catalysts. Results were compared to those obtained with commercial Pt/C and PtRu/C catalysts supported on Vulcan XC-72R (E-TEK). All electrocatalysts supported on carbon xerogel showed better performances than commercial ones, providing higher current density values for the oxidation of methanol.
C. Alegre, L. Calvillo, R. Moliner, J.A. González-Expósito, O. Guillén-Villafuerte, M.V. Martínez Huerta, E. Pastor, M.J. Lázaro, Journal of Power Sources 196 (2011) 4226–4235

A2120 – Study of the nitridation process of TiSi2 powder

This paper reports on the nitriding process of TiSi2 micro/submicrometer-sized powders. TiSi2 powders were treated under nitrogen flow, at 1100 °C, during various durations. The composition and morphology of the nitride powders are characterized by X-ray diffraction and observed on cross-section, prepared using ion polishing system by scanning electron microscopy whereas the chemical composition is analyzed by energy dispersive X-ray spectroscopy. All these analyses revealed that under nitrogen flow, TiSi2 grains are first transformed into a core-shell structure composed of TiN, surrounded by Si. Long nitriding treatments result in the complete transformation of Si3N4. These results are discussed in terms of various diffusion limitation phenomena
L. Maillé, M.A. Dourges, S. Le Ber, P. Weisbecker, F. Teyssandier, Y. Le Petitcorps, R. Pailler, Applied Surface Science 260 (2012) 29– 31

A2108 – Upscaling potential of the CVD stacking growth method to produce dimensionally-controlled and catalyst-free multiwalled carbon nanotubes

Multi-walled CNTs (MWCNTs) with structural characteristics optimised for bio-applications have been produced using a catalyst-supported chemical vapour deposition (CVD) method. The upscale potential of the process was demonstrated by combining classical semi-continuous and stacked-growth modes. The vertically aligned MWCNT films thus obtained were multi-layered with five continuous strata of well-structured nanotubes. Following gentle disentanglement, the stacks were converted to individual MWCNTs with short dimensions (a final length and diameter of ?1.2 ?m and ?12 nm) and almost catalyst-free (<0.04%). Overall, our process produces dispersed, bio-tailored MWCNTs with an output growth-yield 20 times higher than a standard CVD setup and exempt of complex or destructive post-growth steps of purification and separation. These constitute key steps towards the mass production of MWCNTs with low toxicological risks, an essential prerequisite for biomedical applications.
D. Mata, R.M. Silva, A.J.S. Fernandes, F.J. Oliveira, P.M.F.J. Costa, R.F. Silva, Carbon, 50 (2012) 3585-3606

A2104 – Thermodynamic restrictions on mechano synthesis of strontium titanate

Chemical potential phase stability diagrams were calculated from relevant thermodynamic properties and used to predict the thermodynamic driving force under prospective conditions of room temperature mechanosynthesis. One analysed the dependence of chemical potential diagrams on temperature and partial pressure of evolving gases such as oxygen or carbon dioxide, as expected on using strontium peroxide or strontium carbonate as precursor reactants for the alkali earth component. Thermodynamic calculations were also obtained for changes in titania precursor reactants, including thermodynamic predictions for reactivity of strontium carbonate with amorphous titania. Experimental evidence showed that strontium titanate can be obtained by mechanosynthesis of strontium carbonate+anatase mixtures, due to previous amorphization under high energy milling. Ability to perform mechanosynthesis with less energetic milling depends on the suitable choice of alternative precursor reactants, which meet the thermodynamic requirements without previous amorphization; this was demonstrated by mechanosynthesis from anatase+strontium peroxide mixtures.
J.F. Monteiro, A.A.L.Ferreira, I.Antunes, D.P.Fagg, J.R.Frade, Journal of Solid State Chemistry 185 (2012) 143–149

A2103 – Innovative fabrication of PZT pillar arrays by a colloidal approach

An innovative approach for fabricating pillar arrays for ultrasonic transducer applications is disclosed. It involves the preparation of concentrated piezoelectric lead zirconate titanate (PZT) suspensions in aqueous solutions of epoxy resin and its polymerization upon adding a polyamine based hardener. Zeta potential and rheological measurements revealed that 1 wt.% dispersant, 20 wt.% of epoxy resin and a hardener/epoxy resin ratio of 0.275 mL g?1, were the optimized contents to obtain strong PZT samples with high green strength (35.21 ± 0.39 MPa). Excellent ellipsoidal and semi-circle shaped pillar arrays presenting lateral dimensions lower than 10 ?m and 100 ?m height were successfully achieved. The organics burning off was conducted at 500 °C for 2 h at a heating rate of 1 °C min?1. Sintering was then carried out in the same heating cycle at 1200 °C for 1 h. The microstructures of the green and sintered ceramics were homogeneous and no large defects could be detected.
Susana M. Olhero, Luis Garcia-Gancedo, Tim W. Button, Fernando J. Alves, José M.F. Ferreira, Journal of the European Ceramic Society 32 (2012) 1067–1075

A2101 – A simple chemical method for deposition of electrochromic potassium manganese oxide hydrate thin films

A new chemical method for fast deposition of electrochromically active thin films of birnessite-type potassium manganese oxide (K0.27MnO2·xH2O) has been developed. The chemical deposition has been performed at room temperature by a reaction of aqueous solutions of potassium permanganate and manganese(II) chloride. The prepared thin films have thickness from 50 to 250 nm depending on the number of the deposition cycles. The composition and the structure of the K-birnessite films are studied by XRD, IR spectroscopy and TG/DTA analyses. Electrochemical studies using four different electrolytes such as aqueous K2SO4, Li2SO4, KNO3, and LiClO4 in PC have been performed. The electrochromic activity has been explored by cyclic voltammetry and VIS spectrometry. The best electrochromic properties are obtained using aqueous KNO3, where the difference in the transmittance at 400 nm between the bleached and colored state is 40% for both as-deposited and annealed films. The obtained data allow the prepared K-birnessite thin films in aqueous KNO3 electrolyte to be proposed as a promising system for electrochromic applications. ⺠A new method for deposition of electrochromic K0.27MnO2·xH2O thin films is developed. ⺠The deposition has been performed by a reaction between KMnO4(aq) and MnCl2(aq). ⺠The films exhibit electrochromism changing the color from brown to pale yellow. ⺠The achieved difference in the transmittance of bleached and colored state is 40%. ⺠The best electrochromic properties are obtained by using aqueous KNO3 solution.
Metodija Najdoski, Violeta Koleva, Sani Demiri, Sasho Stojkovikj, Materials Research Bulletin 47 (2012) 2239–2244

A2092 – A study on the properties of Zr-doped ?-Al2O3 xerogels hybridized with ?-Al2O3 whiskers synthesized by solvothermal drying

Hydrophobic zirconium doped alumina xerogels and zirconium doped alumina xerogels hybridized with ?-Al2O3 whisker were fabricated by Si(CH3)3 (trimethylsilyl substituent) modification of alcogels via ambient pressure solvothermal drying procedure. One-step solvent exchange and surface modification were simultaneously progressed by immersing alumina alcogels in hexamethyldisilazane/hexane solution. The synthesized Zr doped Al2O3 xerogels have shown increased phase transition temperature from ?-phase to ?-phase over 200 °C. Although phase transition temperature was increased, the porous structure of Zr-doped Al2O3 xerogel was collapsed over 1200 °C losing its specific surface area. To maintain their porous structures at the elevated temperatures, the Zr-doped Al2O3 xerogels were hybridized with ?-Al2O3 whiskers. The ?-Al2O3 whiskers were grown at 1400 °C and thus sustained its phase and structure over 1400 °C. The ?-Al2O3 whiskers in xerogels act as a pillar at elevated temperatures. As a result, Zr doped Al2O3 xerogels hybridized with ?-Al2O3 whiskers maintained their porous structure over 1400 °C even though there was a phase transition from ?-Al2O3 to ?-Al2O3.
In Keun Jung, Tae-Jung Ha, Hyung-Ho Park, Si Jung Park, Doo Jin Choi, Seungsu Baek, Surface & Coatings Technology (2012)

A2088 – The properties of silica aerogels hybridized with SiO2 nanoparticles by ambient pressure drying

In this study, we report the chemical characteristics of silica aerogels that were produced by adding SiO2 nanoparticles into silica aerogel by ambient pressure drying. We synthesized silica aerogel composites with different weight percentages of SiO2 nanoparticles ranging from 0 wt% to 0.025 wt% of the total amount of solution. As the wt% of SiO2 nanoparticles increased, the number of chemical bonds that formed during condensation of the silica aerogel increased because of the presence of surface hydroxyl groups, thus the particle size of the silica aerogels increased. Silica nanoparticle-doping of silica aerogels can be used to control the synthesis of nanocomplex structures.
In-Keun Jung, Jyoti L. Gurav, Tae-Jung Ha, Sun Gyu Choi, Seungsu Baek, Hyung-Ho Park, Ceramics International 38S (2012) S105–S108

A2087 – Stability study of possible air electrode materials for proton conducting electrochemical cells

In the search for new air electrode materials for Proton Conducting Cells (PCC), the case of basic (rare earth and/or alkaline earth containing) oxocobaltites has been considered to find materials exhibiting mixed electron and proton conductivity. The stability in dry and wet air of classical (cubic and derived) as well as hexagonal 2H perovskite structures has been examined. The following compositions were studied: LaCoO3, Sr0.5La0.5CoO3, SrCoO3, Ba0.5Sr0.5CoO3, BaCoO3 and Ba0.5La0.5CoO3. Among them, four materials appeared to be stable enough in the selected operating conditions of ageing: BaCoO3, LaCoO3, Sr0.5La0.5CoO3 and Ba0.5La0.5CoO3. The reactivity study of the latter materials with the classical BaZr0.9Y0.1O3 electrolyte material has also been studied. Oxygen vacancy formation and structural water incorporation was analyzed by iodometry and TGA allows identifying them as the best compromise of the series for a PCC air electrode application.
G. Goupil, T. Delahaye, G. Gauthier, B. Sala, F. Lefebvre Joud, Solid State Ionics 209–210 (2012) 36–42

A2086 – Non stoichiometry,point defects and magnetic properties in Sr2FeMoO(6-?) double perovskites

The phase stability, nonstoichiometry and point defect chemistry of polycrystalline Sr2FeMoO6?? (SFMO) was studied by thermogravimety at 1000, 1100, and 1200 C. Single-phase SFMO exists between ?10.2 ? log pO2 ? -13.7 at 1200 °C. At lower oxygen partial pressure a mass loss signals reductive decomposition. At higher pO2 a mass gain indicates oxidative decomposition into SrMoO4 and SrFeO3?x. The nonstoichiometry ? at 1000, 1100, and 1200 °C was determined as function of pO2. SFMO is almost stoichiometric at the upper phase boundary (e.g. ?=0.006 at 1200 °C and log pO2=-10.2) and becomes more defective with decreasing oxygen partial pressure (e.g. ?=0.085 at 1200 °C and log pO2 = ?13.5). Oxygen vacancies are shown to represent majority defects. From the temperature dependence of the oxygen vacancy concentration the defect formation enthalpy was estimated (?HOV=253 ± kJ/mol). Samples of different nonstoichiometry ? were prepared by quenching from 1200 °C at various pO2. An increase of the unit cell volume with increasing defect concentration ? was found. The saturation magnetization is reduced with increasing nonstoichiometry ?. This demonstrates that in addition to Fe/Mo site disorder, oxygen nonstoichiometry is another source of reduced magnetization values.
R. Kircheisen, J.Topfer, Journal of Solid State Chemistry 185 (2012) 76–81

A2082 – Investigations of SiC aggregates oxidation: Influence on SiC castables refractories life time at high temperature

This paper reports results concerning the oxidation of silicon carbide of pure SiC powder (98% of SiC) and the oxidation of two silicon carbide castables, used in waste-to-energy plants (WTE), and containing 60% and 85% of SiC, respectively. The investigated temperature range (800–1200 °C) corresponds to typical service conditions in WTE. Thanks to thermogravimetric and thermal expansion tests, kinetics of oxidation of the powder of SiC and of the castables has been investigated. According to these tests, several important points have been underlined. Firstly, the oxidation of SiC aggregates has a high influence on the thermal expansion and on the weight gain of SiC castables. Secondly, the grain size distribution of SiC aggregates within castables plays a dominating role (especially enhanced for the fine particles) in castable expansion behaviour induced by oxidation. This is a key point according to the evolution of thermal expansion of such materials.
A. Gallet-Doncieux, O. Bahloul, C. Gault, M. Huger, T. Chotard, Journal of the European Ceramic Society 32 (2012) 737–743

A2081 – Ni-8YSZ cermet re-oxidation of anode supported solid oxide fuel cell: From kinetics measurements to mechanical damage prediction

The ‘redox’ tolerance of a typical anode supported cell was evaluated for three temperatures of re-oxidation. For this purpose, an experimental work has been coupled to a modelling approach to estimate the risk of electrolyte failure during re-oxidation. A special attention has been paid to take into account both (i) the heterogeneity of oxidation and (ii) the cermet visco-plasticity in operation. Data required for the simulations – i.e. the oxidation kinetics rates, the cermet expansions and Young’s modulus – were determined at T = 600, 700 and 800 °C. It has been found that the activation energy related to the kinetics of re-oxidation encounters a modification at high temperature (700–750 °C). This modification has been ascribed to a transition from a homogeneous oxidation process to a heterogeneous one. Local X-ray measurements have confirmed that an oxidation gradient in the cermet arises at T = 800 °C. Mechanical analysis has shown that the presence of an oxidised front at T = 800 °C strongly impacts the cell ‘redox’ tolerance. Indeed, this phenomenon induces a significant cell bending, which adds a compressive stress component to the thin electrolyte. Simulations have been carried out to determine both critical degree of oxidation and durations before electrolyte cracking. The effect of the cermet creep during operation on the cell ‘redox’ tolerance is also discussed.
J. Laurencin, V. Roche, C. Jaboutian, I. Kieffer, J. Mougin, M.C. Steil, International Journal of Hydrogen Energy, 37 (2012) 12557-12573

A2077 – Microstructure evolution of TiO2 gas sensors produced by electrospinning

Gas sensors produced by electrospinning demonstrate excellent performance in terms of sensitivity, reversibility, response and recovery time. These merits are formally attributed to their nanostructured fibrillar morphology and the relationship between microstructure and gas sensing properties. Thus, careful investigation is required to optimize the microstructure in order to achieve high gas sensing performance. In this work we study the microstructure evolution of nanostructured TiO2 gas sensors produced by electrospinning and examine the correlation between processing conditions, microstructure and gas sensing properties. Two distinguished TiO2 mesoporous morphologies were obtained, one with smaller grain size (29 nm) and higher specific surface area (71.4 m2/g) and the other with larger grain size (42 nm) and lower specific surface area (13.3 m2/g). The sensors displayed stable and reversible response to CO and NO2, with response and recovery time of several min. Two contributions to the overall impedance were observed, corresponding to the surface depletion region and the remaining bulk region. The surface impedance was found to be sensitive to CO and NO2 unlike the bulk impedance that displayed very little sensitivity to these gases. These results give new insight on the correlation between microstructure and gas sensing properties of electrospun TiO2 gas sensors.
Osnat Landau, Avner Rothschild, Sensors and Actuators B 171– 172 (2012) 118– 126

A2074 – Synthesis and electrical properties of co-doping with La3+, Nd3+, Y3+ and Eu3+ citric acid-nitrate prepared samarium-doped ceria ceramics

Fluorite oxides Ce0.8Sm0.1Ln0.1O1.9 (denoted as SDC for singular doping and LnSDC for Ln=La, Nd, Y and Eu), were prepared by the citric acid–nitrate combustion reaction to act as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The thermal decomposition, phase identification, morphology, density, particle size distribution and electrical properties of the samples were studied by TGA/TDA, XRD, SEM, the Archimedes method, a laser size analyzer and Impedance spectroscopy, respectively. All crystallite powders that calcined at 800 °C had a cubic fluorite structure; the average crystallite size was between 63 and 68.5 nm. The pellets were then sintered at 1400 °C in air for 7 h. The relative densities of these pellets were over 95%, which was in good agreement with the results of the SEM. The impedance measurements were performed in an open circuit using two electrode configurations. The results showed that Ce0.8Sm0.1La0.1O1.9 had the highest electrical conductivity, ?700 °C, equal to 6.59×10?2 S cm?1 and the lowest activation energy equal to 0.85 eV. It was therefore concluded that co-doping with the appropriate rare-earth cations can further improve the electrical properties of ceria electrolytes
Massoud Kahlaouin, Sami Chefi,Abdelwahab Inoubli,Adel Madani,Chaabane Chefi, Ceramics International 39 (2013) 3873–3879

A2070 – Preparation and characterization of Ce- and La-doped Ba2In2O5 as candidates for intermediate temperature (100–500 ?C) solid proton conductors

Five different compositions of brownmillerite materials, Ce- and La-doped, and undoped Ba2In2O5 were synthesized via the solid-state reaction and the glycine-nitrate combustion process. Properties of the materials were characterized using XRD, HR-TEM, and TGA/DSC techniques. Conductivity measurements by AC impedance spectroscopy, performed in air and hydrogen-containing atmospheres, in the temperature range from 100 °C to 500 °C, were correlated to the properties of the materials and revealed the effects of dopant, microstructure, temperature and atmosphere on the total electrical conductivity of the materials. All compositions showed low conductivity in air. In hydrogen-containing atmospheres, while Ce- and La-doped Ba2In2O5 showed low conductivity (4 × 10?6–3 × 10?6 S cm?1 at 500 °C), undoped Ba2In2O5 demonstrated a surprisingly high conductivity (between 0.02 S cm?1 and 0.7 S cm?1 in the temperature range from 300 °C to 500 °C), especially samples produced by the glycine-nitrate process. This finding creates potential opportunity for using Ba2In2O5 as a proton-conductive material in intermediate temperature fuel cells.
Jasna Jankovic, David P. Wilkinson, Rob Hui, Journal of Power Sources 201 (2012) 49– 58

A2063 – High-temperature conductivity, stability and redox properties of Fe3?xAlxO4 spinel-type materials

Iron-based oxides are considered as promising consumable anode materials for high temperature pyroelectrolysis. Phase relationships, redox stability and electrical conductivity of Fe3?xAlxO4 spinels were studied at 300–1773 K and p(O2) from 10?5 to 0.21 atm. Thermogravimetry/XRD analysis revealed metastability of the sintered ceramics at 300–1300 K. Low tolerance against oxidation leads to dimensional changes of ceramics upon thermal cycling. Activation energies of the total conductivity corresponded to the range of 16–26 kJ/mol at 1450–1773 K in Ar atmosphere. At 1573–1773 K and p(O2) ranging from 10?5 to 0.03 atm, the total conductivity of Fe3?xAlxO4 is nearly independent of the oxygen partial pressure. The conductivity values of Fe3?xAlxO4 (0.1 ? x ? 0.4) at 1773 K and p(O2) ?10?5 to 10?4 atm were found to be only 1.1–1.5 times lower than for Fe3O4, showing high potential of moderate aluminium additions as a strategy for improvement of refractoriness for magnetite without significant deterioration of electronic transport.
Andrei V. Kovalevsky, Eugene N. Naumovich, Aleksey A. Yaremchenko, Jorge R. Frade, Journal of the European Ceramic Society 32 (2012) 3255–3263

A2054 – Synthesis and electrochemical characterization of LiFePO4/C composites prepared by the microemulsion method

LiFePO4/C composites were synthesized by a solid state reaction method utilizing two-component mixture of FeC2O4·2H2O and LiH2PO4. Sintering the reactants with C12H22O11 at different temperatures above 650 °C yields a product containing Fe2P as a secondary phase to olivine LiFePO4. The LiFePO4/Fe2P/C composite synthesized at 750 °C exhibits an excellent electrochemical performance, i.e. a discharge capacity of 152 mAh/g with a smooth plateau of 3.37 V and a good cycle performance at 0.2C charge/discharge current rate. Other detection techniques, such as X-ray absorption near edge structure (XANES) and scanning electron microscopy (SEM), were also carried out to characterize the sample.
Jing-Han Lin, Jenn-Shing Chen, Electrochimica Acta 62 (2012) 461– 467

A2032 – TetragonalYBaFe4O7.0: Astoichiometricpolymorphofthe‘‘114’’ ferrite family

The exploration of the phase diagram of the ferrite YBaFe4O7+? versus the oxygen content ? and temperature shows the complex crystal chemistry of this system. Besides the cubic form (F4¯3m), which is observed up to 600 °C and for 0
V. Duffort, V.Caignaert, V.Pralong, N.Barrier, B.Raveau, M.Avdeev, H.Zheng, J.F.Mitchell, Journal of Solid State Chemistry 191 (2012) 225–231

A2031 – A composite sol–gel process to prepare a YSZ electrolyte for Solid Oxide Fuel Cells

ZrO2–8% Y2O3 (YSZ) thick film was deposited on a YSZ–NiO anode and co-sintered to obtain a gas-tight electrolyte for an application as Solid Oxide Fuel Cell. A YSZ sol–gel composite sol is synthesized from a YSZ colloidal binder and a YSZ commercial powder and deposited as a thick (>10 ?m) monolayer by the dip-coating process. The evolution of the composite sol viscosity with time and its influence on the deposited film thickness is studied. The influence of the composite sol composition, the film sintering on the films microstructure is also studied in order to achieve dense films. The interest of co-sintering the electrolyte with the anodic support is demonstrated. Ionic conductivity and activation energy are measured on pellets obtained from pressed-powder obtained from (a) the calcination of composite sol and (b) the commercial powder. Conductivity of 0.03 S cm?1 at 800 °C and activation energy of 0.9 eV were measured through impedance spectroscopy. Finally, an entire cell is processed with the developed electrolyte and polarization curves (I–V) were measured at 850 °C. OCV of 1.23 V was achieved, indicating the quality of the synthesized YSZ electrolyte
E. Courtin, P. Boy, T. Piquero, J. Vulliet, N. Poirot, C. Laberty-Robert, Journal of Power Sources 206 (2012) 77– 83

A2030 – Synthesis of YSZ thin films by the novel aqueous sol–gel citrate-precursor method

The objective of this work is the synthesis of 20 mol% Y2O3 doped ZrO2 thin films on crystalline silicon (Si) substrate from the aqueous Y–Zr–O nitrate–citrate sols dissolved in ethanol or isopropanol using spin-coating technique and the investigation of the morphological, structural and electrical properties. All obtained samples were repeatedly annealed at 800 °C temperature after spin-coating procedure and fully characterized by X-ray diffraction (XRD) analysis. XRD data exhibited that nanosized Y0.2Zr0.8O2 (YSZ) thin films have been formed at 800 °C. Thermal decomposition mechanisms of dried Y–Zr–O were monitored by TG/DTA measurements in the dynamic 80%Ar + 20%O2 atmosphere. The morphological features of obtained coatings were investigated by scanning electron microscopy (SEM). The electrical properties were characterized by impedance spectroscopy in a temperature range from 200 °C to 450 °C. Impedance results demonstrate that the conductivity of prepared layer is one order of magnitude lower in comparison with the YSZ bulk reference conductivity and the total conductivity of the YSZ film on silicon is mostly determined by the grain conductivity.
Brigita Abakevi?ien?, Art?ras Žalga, Stasys Tautkus, Jurgis Pilipavi?ius, Edvinas Navickas, Aivaras Kareiva, Sigitas Tamulevi?ius, Solid State Ionics 225 (2012) 73–76

A2029 – Experimental determination of the eutectic temperature in air of the CuO–TiO2 pseudobinary system

Eutectic temperature and composition in the CuO–TiO2 pseudobinary system have been experimentally determined in air by means differential thermal analysis (DTA), thermogravimetry (TG) and hot-stage microscopy (HSM). Samples of the new eutectic composition treated at different temperatures have been characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structural spectroscopy (XANES) to identify phases and to determine the Cu valence state, respectively. The results show that the eutectic temperature in air is higher by 100 °C (?1000 °C) for a Ti-richer composition (XTiO2=25?mol%XTiO2=25?mol%) than the one calculated in the literature. The reduction of Cu2+ to Cu+ takes places at about 1030 °C. The existence of Cu2TiO3 and Cu3TiO4 has been confirmed by XRD in the temperature range between 1045 and 1200 °C.
M.A. de la Rubia, J.J. Reinosa, P. Leret, J.J. Romero, J. de Frutos, J.F. Fernández, Journal of the European Ceramic Society 32 (2012) 71–76

A2024 – High temperature conduction and methane conversion capability of BaCeO3 perovskite

The transport properties and reactivity in gases of a BaCeO3 perovskite phase have been investigated to develop new materials for methane conversion in microsystems. The polycrystalline material has been synthesized at moderate temperature using a specific modified EDTA-citrate complexing methodology. The BaCeO3 phase has been characterized by X-ray diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), scanning and transmission electronic microscopy techniques (SEM, TEM), energy dispersive X-ray (EDX) and surface area analyses. A Rietveld analysis of diffraction profiles has allowed determining the structural parameters of the as prepared material. Next, the catalytic efficiency of the BaCeO3 phase with air-methane gas flows has been characterized by Fourier transformed infrared (FTIR) spectroscopy: the conversion rate of CH4 into CO2 has been determined from the intensities of CO2 absorption bands, as a function of temperature (from 450 to 750 °C) and reaction time. Finally, the electrical conduction of compacted BaCeO3 pellets has been determined from electrical impedance spectroscopy analyses between 300 °C and 950 °C. A series of electrical transitions correlated with well known structural changes has been observed between 300 °C and 950 °C. The starting catalytic activity of BaCeO3 might be correlated to the enhanced ionic conduction observed above 450 °C.
Francisco Wendell Bezerra Lopes, Madjid Arab, Heloisa Pimenta Macedo, Carlson Pereira de Souza, João Fernandes de Souza, Jean Raymond Gavarri, Powder Technology 219 (2012) 186–192

A2020 – Recycling of foundry by-products in the ceramic industry: Green and core sand in clay bricks

Green and core foundry sand are mixed with clay in proportions 0–50% and fired at 850–1050 °C to produce ceramic bricks. The specimens are physically and mineralogically evaluated, the scaling-up analyzed, and an optimization study developed. Clay/green sand bricks fired at 1050 °C have the better physical properties values, while the mineralogy is not significantly affected. The industrial quality brick can be estimated with laboratory trials, and the optimum amount of sand is found to be 35% of green sand and 25% of core sand
R. Alonso-Santurde, A. Coz, J.R. Viguri, A. Andrés, Construction and Building Materials 27 (2012) 97–106

A2019 – Gadolinia-doped ceria mixed with alkali carbonates for SOFC applications: II e An electrochemical insight

Composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li2CO3-K2CO3 or Li2CO3-Na2CO3) are potential electrolytes for low temperature solid oxide fuel cell applications (LTSOFC). This paper completes a first one dedicated to the thermal, structural and morphological study of such compounds; it is fully focussed on their electrical/electrochemical properties in different conditions, temperature, composition and gaseous atmosphere (oxidative or reductive). The influence of the gaseous composition on the Arrhenius conductivity plots is evidenced, in particular under hydrogen atmosphere. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 6000 h. First results on single cells showed performance at 600 °C of 60 mW cm?2.
M. Benamira, A. Ringuede, L. Hildebrandt, C. Lagergren, R-N. Vannier, M. Cassir, International Journal of Hydrogen Energy, 37 (2012) 19371-19379

A2009 – Effect of reactive gas composition on the microstructure, growth mechanism and friction coefficient of TiC overlayers

Titanium carbide overlayers were synthesized by gas phase carburization of titanium at 1150 °C with varying reactive gas compositions and durations. These layers were investigated by X-ray diffraction, tribometry, Raman spectroscopy and scanning electron microscopy. Titanium carbide layers exhibited very low coefficient of friction due to the presence of amorphous carbon on the surface. The growth mechanism and the surface microstructure of the layers showed a critical dependence on methane content in the reactive gas mixture
P.K. Ajikumar, M. Vijayakumar, M. Kamruddin, S. Kalavathi, N. Kumar, T.R. Ravindran, A.K. Tyagi, Int. Journal of Refractory Metals and Hard Materials 31 (2012) 62–70

A2007 – Study of structure–performance relationships in Meerwein–Ponndorf–Verley reduction of crotonaldehyde on several magnesium and zirconium-based systems

Several magnesia and zirconia systems were synthesized through the sol–gel process (calcination temperature in the 175–600 °C range) and tested for liquid and gas-phase Meerwein–Ponndorf–Verley reduction of crotonaldehyde with 2-propanol. In the liquid phase, only zirconia systems were active, probably because carbonates and water “poison” active sites in basic magnesia. Moreover, the more surface OH groups were present in zirconia solids, the higher the activity exhibited. As far as reactions in the gas phase are concerned, both zirconia and magnesia solids were active, the latter exhibiting higher conversions at the same reaction temperatures. Furthermore, for MgO solids selectivity to crotyl alcohol increases with the reaction temperature which suggests that either new active sites were “in situ” created or the existing ones were unblocked and made accessible to the reactants. All in all, selectivities to crotyl alcohol of ca. 62% at 16% conversion were obtained for more active systems ZrO2-200 and ZrO2-250 in the liquid phase whereas values above 85% at 50% conversion were achieved on MgO solids in the gas-phase.
S. Axpuac, M.A. Aramendía, J. Hidalgo-Carrillo, A. Marinas, J.M. Marinas, V. Montes-Jiméne, F.J. Urbano, V. Borau, Catalysis Today 187 (2012) 183– 190

A1999 – Heavy metals and color retention by a synthesized inorganic membrane

In this study, a new type of a double-layer ceramic membrane was used for the filtration of wastewater. The synthesized membrane consists of a macroporous substrate (with pore size of about 0.1 ?m) prepared following the colloid filtration technique and a thin film functional layer (with pore size of about 10 nm) carried out according to the sol–gel preparation method. The ceramic membranes were tested for the removal of cadmium, zinc, Methylene Blue and Malachite Green from water under a pressure of 5 bar and a treatment time of 2 h. Liquid filtration and flow tests through these membranes resulted in a rejection rate of 100% for Methylene Blue and Malachite Green. This paper also presents the ability of the tubular membrane prepared to separate heavy metals (cadmium and zinc) from their synthetic aqueous solutions. The influence of the applied pressure, feed solute concentration, feed pH on the rejection of cadmium and zinc ions was studied. Retention rates of cadmium and zinc ions of 100% were observed for an initial feed concentration of 10?4 mol/L.
A. Chougui, K. Zaiter, A. Belouatek, B. Asli, Arabian Journal of Chemistry (2012)

A1985 – Mechanochemical preparation, sintering aids and hybrid microwave sintering in the proton conductor Sr0.02La0.98Nb(1-x)VxO(4-?), x= 0, 0.15

Mechanochemical preparation of Sr0.02La0.98Nb(1-x)VxO(4-?) was demonstrated for values of x = 0 and 0.15. Crystallinity could be improved by calcining at 1073 K. On cooling, the high temperature scheelite phase was retained to room temperature. Several novel sintering additives for LaNbO4 materials have been tested. The most successful were Cu3Nb2O8 and CuV2O6, which reduced the temperature of maximum shrinkage rate to temperatures ~ 1173 K. The additive CuV2O6 was shown to increase densification and promote grain growth. A mechanosynthesised sample of Sr0.02La0.98Nb0.85V0.15O(4-?) + 2 mol% CuV2O6 could be densified to w 90% that of the theoretical by hybrid microwave sintering at 1168 K for 5 min. The scheelite phase in this material was retained to room temperature, against the normal thermodynamic tendency. Impedance spectroscopy in wet and dry, nitrogen and oxygen atmospheres suggested that the bulk conductivity of this material is unaffected by the sintering aid, whereas the grain boundary conductivity was impaired and exhibited ntype conductivity behaviour, characteristic of the additive. The concentration of this promising additive should be reduced in further work.
A.D. Brandao, I. Antunes, J.R. Frade, J. Torre, S.M. Mikhalev, D.P. Fagg, International Journal of Hydrogen Energy, 37 (2012) 7252-7261

A1984 – Enthalpies of formation and insights into defect association in ceria singly and doubly doped with neodymia and samaria

It has been suggested that co-doping ceria with two trivalent ions of different sizes to minimize lattice strain producesmaterials with better ionic conductivity. To investigate the thermodynamic basis of such behavior, enthalpies of formation at roomtemperature of samarium-doped ceria (Ce(1?x)SmxO(2?0.5x) with 00.05 for singly doped ceria systems can be attributed to defect associates of trivalent cations coupled with charge-balancing oxygen vacancies. For co-doped Ce(1?x)Ndx/2Smx/2O(2?0.5x), there is less destabilization at low x compared to singly doped CeO2 but less stabilization at high x and a shift in the composition of maximum (most endothermic) formation enthalpy toward higher dopant concentration. Enthalpies of defect association of Ce(1?x)Ndx/2Smx/2O(2?0.5x) are less exothermic than those of singly doped materials.
Salih Buyukkilic, Tatiana Shvareva, Alexandra Navrotsky, Solid State Ionics 227 (2012) 17–22

A1968 – Thermal Behavior of (Organosilicon) Polymer-Derived Ceramics. V: Main Facts and Trends

Extensive investigations of polymer-based ceramic materials taken within the Si-C-N-O-(H) system have been performed and previously published as Parts I - IV. This paper reports the main results, facts, trends and conclusions which can be drawn from them, regarding the physical and chemical behavior of these materials submitted to an increasing thermal treatment. Both similarities and discrepancies are described and explained, whatever the chemical composition of the ceramic, (i.e. containing StC or StC-N, 22-C-0, StC-N-O). Emphasis is made on the mechanisms, and the role of various parameters, either intrinsic (e.g. the role of compositional C, 0, or N) or extrinsic (e.g. injluence of the atmosphere), is examined. The overall results indicate, among others, that excess carbon (relative to the Sic stoichiometry) is always beneficial both to the structural stability of the ceramic and the mechanical properties (when measurable), while heteroatoms (0, N) are always finally detrimental. They thus sustain the current eflorts to develop ceramic$bers from chemical systems as simple as possible, using oxygen-free curing processes. More generally, they provide guidelines for understanding, and somewhat predicting, the thermochemical behavior of any related materials.
M. Monthioux, 0. Delverdier, Journal of the European Ceramic Society 16 (1996) 721-131

A1967 – Modulation of the crystallinity of hydrogenated nitrogen-rich graphitic carbon nitrides

An hydrogenated nitrogen-rich graphitic carbon nitride, structurally related to the theoretical graphitic phase of C3N4, has been synthesized in a bulk well-crystallized form. This new material was prepared by thermal decomposition of thiosemicarbazide up to 600 °C at ambient pressure under nitrogen flow. Its composition was determined by elemental combustion analysis. Powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and C13 MAS NMR characterizations were performed. This material can be schematically described with a two-dimensional framework and a composition close to C3N4.17H1.12. In this nitrogen-rich material, C3N3 voids are fully occupied by water molecules which are strongly trapped into the material. A loss of crystallinity associated with a modification of the thermal behavior is observed when the amount of trapped molecules decreases in the graphitic material, order being damaged both between and in the graphitic planes.
Denis Foy, Gérard Demazeau, PierreFlorian, Dominique Massiot, Christine Labrugère, GraziellaGoglio, Journal of Solid State Chemistry182 (2009) 165–171

A1965 – Oxidation behaviour of ceramic fibres from the Si-C-N-O system and related sub-systems

The oxidation of Si-C-N-O fibres has been investigated. The oxidation rates and the activation energies for the Si-C-O system are similar to those for crystalline SiC. The oxygen and the free carbon concentrations in the ceramics have a limited influence on the oxidation behaviour. As long as the formed silica scale is protective, oxidation kinetics are essentially controlled by the difffusion of oxygen through SiO2. The parabolic rates in the Si-C-N-O and Si-N-O systems are lower and their activation energies higher than those for SiC. Their values strongly depend on the ratios of C and N bonds to Si and continuously vary from those for SiC (Ea = 110 -140kJ mol-1) to Si3N4 (Ea = 330-490 kJ mol-1). The oxidation mechanism might be related to a complex diffusion/reaction regime via the formation of an intermediate silicon-oxynitride (like for Si3N4) or silicon-oxycarbonitride layer. The oxidation behaviour of such complex systems is not significantly influenced by the oxygen nor the free carbon contents. It might be governed by the C/Si and N/Si ratios, limiting the nitrogen concentration gradient of the silicon-oxy(carbo)nitride sub-layer.
Georges Chollon, Journal of the European Ceramic Society 20 (2000) 1959-1974

A1937 – The thermal decomposition of barium trifluoroacetate

A detailed analysis of the thermal decomposition of barium trifluoroacetate under different atmospheres is presented. Thermogravimetry, differential thermal analysis, and evolved gas analysis have been used for this in situ analysis. The presence of oxygen significantly advances the decomposition, while the presence of water vapor has a minor effect. The process is exothermic, the heat evolved being significantly larger in the presence of oxygen. The final product is BaF2, which is stable up to 1200 ?C. The underlying mechanism has been disclosed thanks to MS analysis of the volatiles formed during decomposition.
J. Farjas, J. Camps, P. Roura, S. Ricart, T. Puig, X. Obradors, Thermochimica Acta 544 (2012) 77– 83

A1927 – A temperature-programmed desorption and oxidation investigation of wear debris from carbon/carbon composite aircraft brakes

Wear debris obtained from pilot scale disc–disc friction tests carried out at different temperatures and sliding speeds were characterized by simultaneous thermogravimetric and mass-spectrometric measurements. The original C/C material consisted of an ex-PAN preform densified by CVI. Friction tests cycles consisted of a large number of identical braking strokes with experimental parameters corresponding to taxiing. Temperature-programmed desorption spectra of CO2, CO and H2O present similarities with those published in the literature for a wide variety of oxidized activated carbons. However the amount of oxygen expressed per unit surface is generally higher for debris than for oxidized activated carbons. The formation of the corresponding oxygen groups is attributed to the mecanochemical actions (rupture, oxidation, and compaction) that carbon debris undergoes on sliding surfaces before being ejected from the disc/disc contact. In addition, temperature-programmed oxidation of debris under diluted oxygen showed that they are much more oxidable than the original C/C material.
M. François, J.P. Joly, P. Kapsa, P. Jacquemard, Carbon 45 (2007) 124–131

A1925 – On the importance of the structure in the electrical conductivity of fishbone carbon nanofibers

Carbon nanofibers (CNFs) have a remarkable electrical conductivity resulting highly attractive for different applications such as composites or electronics due to their high quality/price ratio. Although it is known that their graphitic character provides a high conductivity, very little is known about the influence of the nanofibers structure on that property. In this study, CNFs characterized by different physical properties are prepared at diverse synthesis temperatures within a range (550–750 C) in which significant structural and dimensional changes are accomplished and homogeneous nanofiber growth takes place. The electrical conductivity is determined on the powdery as-grown materials modifying the compaction degree by applying pressure. Because of a combination of structural features, the apparent electrical conductivity increases with synthesis temperature of CNFs, ranging from 50 S m-1 for the worst conducting CNFs at a low compaction degree (25 % of solid volume fraction) to 3 9 103 S m-1 for the best conducting CNFs at a high compaction degree (60 % of solid volume fraction). Further analysis is carried out applying the percolation theory to analyze the experimental data and the results suggest that both the orientation of the graphenes and the filament diameter distribution play a determining role in the intrinsic electrical conductivity with values in the interval 1.5 9 103 to 1.3 9 104 S m-1. These intrinsic values of electrical conductivity are found between one and two orders of magnitude higher than that of the powder, highlighting the also important effect of porosity.
David Sebastian, Andres G. Ruiz, Isabel Suelves, Rafael Moliner, Mar?a J. Lazaro, J Mater Sci (2013) 48, 1423–1435

A1923 – Multi-wall carbon nanotube networks as potential resistive gas sensors for organic vapor detection

The sensitivity of multi-wall carbon nanotube (MWCNT) networks of randomly entangled pure nanotubes and those oxidized with acidic KMnO4 to various organic solvent vapors (iso-pentane, diethyl ether, acetone and methanol) has been investigated by resistance measurements. The solvents had different polarities given by Hansen solubility parameters and different volume fractions of saturated vapors defined by the vapor pressure. The results show that the network electrical resistance increases when exposed to organic solvent vapors, and a reversible reaction is observed when the network is removed from the vapors. The reaction with KMnO4 increases oxygen content on the nanotube surface and causes lower porosity of MWCNT network as well as higher electrical resistance, which improves the network selectivity to polar solvents. The investigated MWCNT networks could be potentially used as sensing elements for sensitive and selective organic vapor switches.
P. Slobodian, P. Riha, A. Lengalova, P. Svoboda, P. Saha, Carbon 49 (2011) 2499-2507

A1915 – A novel approach towards selective bulk synthesis of few-layer graphenes in an electric arc

The paper demonstrates the selective bulk synthesis of few-layer graphenes by optimizing an external magnetic field assisted electric arc. An ultra-high purity glassy graphite anode was sublimated in an argon atmosphere, and carbon nanotubes (CNTs), along with graphene sheets, were found inside the deposit formed on the cathode. Both the high purity CNTs and the graphene sheets, with minimal structural defects, were synthesized separately by varying the strength and orientation of the external magnetic field. The as-synthesized carbonaceous samples were characterized with the help of transmission electron microscopy, selected area electron diffraction (SAED), Raman spectroscopy and thermogravimetry with the objective of optimizing the highest selective production of 2D graphene structures. The as-synthesized graphene sheets exhibited a relatively high degree of graphitization and low structural defect density as confirmed by Raman spectroscopy. They were found to exhibit higher oxidation temperature (767 ?C) than that of the carbon nanocrystalline particles (690 ?C), as inferred from the thermogravimatric analysis. Moreover, they were found to roll up at their edges on account of their surface energy minimization. This was confirmed by the SAED analysis. With this new technique, we could successfully synthesize 2D graphene structures at the rate of a few gh?1.
Soumen Karmakar, Naveen V Kulkarni, Ashok B Nawale, Niranjan P Lalla, Ratikant Mishra, V G Sathe, S V Bhoraskar, A K Das, J. Phys. D: Appl. Phys. 42 (2009) 115201

A1909 – A review on the thermal stability of calcium apatites

High temperature processing is essential for the preparation of apatites for biomaterials, lighting, waste removal and other applications. This requires a good understanding of the thermal stability and transitions upon heating. The most widely used is hydroxyapatite (HAp), but increasing interest is being directed to fluorapatite (FAp) and chlorapatite (ClAp). The structural modifications for substitutions are discussed to understand the temperature processing range for the different apatites. This is based on a review of the literature from the past few decades, together with recent research results. Apatite thermal stability is mainly determined by the stoichiometry (Ca/P ratio and structural substitutions) and the gas composition during heating. Thermal stability is lowered the most by a substitution of calcium and phosphate, leading to loss in phase stability at temperatures less than 900 °C. The anions in the hexagonal axis, OH in HAp, F in FAp and Cl in ClAp are the last to leave upon heating, and prevention of the loss of these groups ensures high temperature stability. The information discussed here will assist in understanding the changes of apatites during heating in calcination, sintering, hydrothermal processing, plasma spraying, flame pyrolysis, and other high-temperature processes.
Kaia Tönsuaadu, Karlis Agris Gross, Liene Pluduma, Mihkel Veiderma, J Therm Anal Calorim (2012) 110, 647–659

A1907 – Thermoanalytical study of the YSZ precursors prepared by aqueous sol–gel synthesis route

The Y-Zr-O precursors derived from an aqueous sol–gel synthesis have been applied for the preparation of yttria-stabilized zirconia (YSZ) powders and thin films on the corundum (Al2O3) substrate, using dip-coating technique. In this aqueous sol–gel synthesis route, citric acid as a complexing agent has been used for the preparation of stable Y-Zr-O nitrate–citrate sols and gels. Thermal decomposition of dried gels was studied by simultaneous TG/DTA/EGA-FTIR measurements in the dynamic 80%Ar ? 20%O2 atmosphere. FTIR and X-ray diffraction analyses were used for the determination of phase purity of the end products obtained at 700, 800 and 900 °C. The morphological features of the prepared YSZ coatings and powders were evaluated using scanning electron microscopy.
K. Tönsuaadu, A. Zalga, A. Beganskiene, A. Kareiva, J Therm Anal Calorim (2012) 110, 77–83

A1893 – Synthesis and characterisation of cobaltite and ferrite spinels using thermogravimetric analysis and X-ray crystallography

The synthesis for a series of ferrite (MIIFe2O4) and cobaltite (MIICo2O4) spinels was investigated where MII is Mg, Co, Ni, Cu or Zn. The ferrites were prepared at a calcination temperature of 800 °C; the cobaltites at 500 °C. TG–MS indicated that reduction of CoIII to CoII occurs at ca. 800 °C, hence, the lower calcination temperature. For both the ferrites and the cobaltites, the evolution of water and CO2 during the calcination suggests the presence of both species in the precipitates. The observed mass losses indicated that the precursor basic carbonate precipitates for the cobaltite synthesis were predominantly carbonate, while the precursor basic carbonate precipitates for ferrite synthesis were predominantly hydroxide in character. XRD data showed successful synthesis of the ferrites with minimal contamination from the parent oxides, while the cobaltites were observed to be predominantly of the spinel structure.
Kia Angus, Paul Thomas, Jean-Pierre Guerbois, J Therm Anal Calorim (2012) 108, 449–452

A1878 – Nano-alumina by gel combustion, its thermal characterization and slurry-based coating on stainless steel surface

Gel combustion method was used to prepare nano-alumina from aluminum nitrate and stoichiometric amount of glycine as fuel. The TG–DTA pattern of the as-prepared powder (combustion product) exhibited exotherms with peaks around 500 and 900 °C accompanied with loss of weight of 25 and 5 % attributed to burning away of carbon left behind and decomposition of residual reaction intermediates left behind, respectively. Even though mass stability is attained above 900 °C, the DTA exhibited an exotherm around 1,150 °C attributed to transformation of gamma to alpha form of alumina. The XRD studies revealed that the powder heated to 900 °C was chemically pure nano-crystalline alumina while that heated above 1,150 °C was crystalline alpha form. As nano-crystalline powders are sinter-active, the nano-crystalline alumina formed by calcination at 900 °C was used to form the coating. A morphological feature of the agglomerates of nano-alumina powders were evaluated using SEM. The powder was de-agglomerated by wet grinding method. The dispersion conditions to form slurry using 900 °C calcined powder for slurry-based coating was optimized using zeta-potential studies, and it was found to exhibit a maximum value of -45 mV at a pH of 9. After 8 h of grinding, the median agglomerate size reduced to 2 lm. Rheological studies exhibited desired pseudoplastic behavior in the range of 10–20 vol.% of solid while the slurry with 15 vol.% only form crack free, dense, and adherent coating after heat treatment at 1,150 °C. The morphology of the coating was found to be uniform and dense.
M. B. Kakade, S. Ramanathan, G. P. Kothiyal, J Therm Anal Calorim, 2012

A1863 – Sintering behaviour of porous ceramic kaolin–corundum composites: Phase evolution and densification

Kaolinite–corundum (derived from bauxite) associations were assessed as candidate matrices in the field of porous ceramics composites. Particles of corundum were expected to behave as non reactive second phase, deflecting the matrix cracks and increasing the toughness. Porosity and densification were monitored by developing coarse grains (67 wt.% of grains <1 mm and 33 wt.% of grains between 1 and 4 mm) of bauxitebased chamotte with corundum as principal phase. The main features resulting from the use of bauxitebased chamotte were the increase of softening point, the absence of vitrification in the temperature range of refractory composites in service and the achievement of a good thermal stability. For temperatures ranging between 1200 and 1300 ?C, flint kaolin matrix did not show any reaction with the red corundum grains. Refractory composites elaborated with more than 30% of corundum exhibited typical final characteristics which satisfied ASTM C155 and ISO 1109 standards for refractory materials, namely: the chemical composition (Al2O3 > 56 wt.%), the secondary expansion (<0.1%), the total porosity (?45 vol.%) and the bulk density (1.9 g/cm3). Such materials are promising lowcost solutions for the production of porous ceramics composites.
Chantale Njiomou Djangang, Elie Kamseu, Maurice Kor Ndikontar, Gisèle Laure Lecomte Nana, Julien Soro, Uphie Chinje Melo, Antoine Elimbi, Philippe Blanchart, Daniel Njopwouo, Materials Science and Engineering A 528 (2011) 8311– 8318

A1859 – Y2O3:Eu3+,Tb3+ thin films prepared by sol–gel method: structural and optical studies

Y2O3: Eu3+,Tb3+ transparent, high density and optical quality thin films were prepared by the sol–gel dip-coating technique. Yttrium (III) 2,4-pentadionate was used as a precursor by its hydrolysis in ethanol. The doping agents were incorporated in the form of europium and terbium nitrate. Structural, morphological and optical properties of prepared films were investigated for different annealing temperatures in order to establish the ideal processing route that enhances the luminescent properties. X-ray diffraction (XRD) analysis shows the cubic phase for 10-layer films and annealing temperatures higher than 500°C. At 700°C, highly densified (4.52 g cm-3) and very smooth films (1.4 nm at 700°C) are produced, composed of crystallites with a grain size of 11 nm. The film thickness, refractive index and porosity, as well as the luminescent properties, were found to vary with treatment temperature.
A. de J. Morales Ram?rez, A. Garc?a Murillo, F. de J. Carrillo Romo, M. Garc?a Hernandez, E. de la Rosa, J. Moreno Palmerin, J Sol-Gel Sci Technol (2011) 58, 366–373

A1858 – Water based sol–gel methods used for Bi-222 thermoelectrics preparation

Three different water based sol–gel methods were compared in the synthesis of Bi2Sr2Co1.8Ox thermoelectric ceramics. We chose methods that can stabilize a Bi3? ion while solution and gel are formed: chelating method using combination of ethylenediamintetraacetic acid (EDTA) and triethanolamine (TEA) chelating agents and, further, synthesis using two different water soluble polymers—polyacrylamide or polyethylenimin. In each sol–gel process, we tested two gel decomposition atmospheres. The gels were decomposed either in air or in inert atmosphere (followed by treatment in pure oxygen). Additionally, a sample synthesized by solid state reaction was used for comparison with the sol–gel prepared samples. The grain size of precursors and also their phase composition were determined for methods used and different gels decomposition atmospheres. The sintered final samples did not differ in phase composition; on the other hand, they vary in volume density and microstructure. The differences were reflected in electric transport measurement (the temperature dependence of Seebeck coefficient, resistivity and thermal conductivity). The use of EDTA/TEA or PEI methods led to the samples with improved thermoelectric parameters in comparison to the solid state sample.
K. Rubesova, T. Hlasek, V. Jakes, D. Sedmidubsky, J. Hejtmanek, J Sol-Gel Sci Technol (2012) 64, 93–99

A1852 – The effect of high tempered firing cycle on the bioactive behavior of sol–gel derived dental porcelain modified by bioactive glass

The purpose of the present study was to investigate the influence of end-temperature over the structural properties, chemical composition and bioactivity of dental porcelain modified by bioactive glass. In particular, sol–gel derived specimens of bioactive glass dental porcelain underwent firing at two increased end-temperatures. All specimens were characterized using Scanning Electron Microscopy, Fourier Transform Infrared and Raman Spectroscopy, X-ray diffraction and N2-porosimetry. In vitro bioactivity test was performed too. SEM analysis of both specimens revealed smooth morphology of particles, which were sintered together. Spherical and closed porei were evident. N2- adsorption isotherms of specimens represented non nano-/meso-porous materials. FTIR and Raman spectroscopy revealed the predominance of b-wollastonite as well as the appearance of a-cristobalite. XRD confirmed the results. In vitro tests evidenced the bioactivity of the specimens regardless of temperature. However, the increased temperature caused delayed apatite precipitation. In conclusion, increased temperature favored the sintering process initiation, along with the surface crystallization, which in turn delayed bioactivity.
Marianthi Manda, Ourania-Menti Goudouri, Lambrini Papadopoulou, Nikolaos Kantiranis, Dimitris Christofilos, Konstantinos Triantafyllidis, Konstantinos Chrissafis, Konstantinos M. Paraskevopoulos, Petros Koidis, J Sol-Gel Sci Technol (2012) 63, 481–494

A1850 – Oxygen Nonstoichiometry and the Thermodynamic and Structural Properties of Double Perovskites PrBaCo(2 –x)CuxO(5+?)

The special features of the structure, electrophysical properties, and oxygen nonstoichiometry of new double perovskites PrBaCo(2 –x)CuxO(5+?) were studied. Within the homogeneity region with respect to copper 0
A. Yu. Suntsov, I. A. Leonidov, A. A. Markov, M. V. Patrakeev, Ya. N. Blinovskov, and V. L. Kozhevnikov, Russian Journal of Physical Chemistry A, 2009, Vol. 83, No. 5, pp. 832–838

A1849 – Oxygen transport in La0.6Sr0.4Co(1-y) FeyO(3-?)

The surface exchange coefficient and chemical diffusion coefficient of oxygen for the perovskites La0.6Sr0.4Co(1-y) FeyO(3-?) (y=0.2, 0.5 and 0.8) were measured using the conductivity relaxation technique. Measurements were performed between 600 and 800 °C in an oxygen partial pressure range between 10-4 and 1 bar. Both transport coefficients decrease markedly with decreasing oxygen partial pressure below about 10-2 bar at all temperatures. This is attributed to ordering of oxygen vacancies. Implications for using La0.6Sr0.4Co(1-y) FeyO(3-?) as an oxygen separation membrane are discussed.
H. J. M. Bouwmeester, M. W. Den Otter, B. A. Boukamp, J Solid State Electrochem (2004) 8, 599–605

A1846 – Oxygen permeability, stability and electrochemical behavior of Pr2NiO4þd -based materials

The high-temperature electronic and ionic transport properties, thermal expansion and stability of dense Pr2NiO4+?; Pr2 Ni0:9Fe0:1O4+? and Pr2 Ni0:8Cu0:2O4+? ceramics have been appraised in comparison with K2NiF4-type lanthanum nickelate. Under oxidizing conditions, the extensive oxygen uptake at temperatures below 1073–1223 K leads to reversible decomposition of Pr2NiO4-based solid solutions into Ruddlesden–Popper type Pr4Ni3O10 and praseodymium oxide phases. The substitution of nickel with copper decreases the oxygen content and phase transition temperature, whilst the incorporation of iron cations has opposite effects. Both types of doping tend to decrease stability in reducing atmospheres as estimated from the oxygen partial pressure dependencies of total conductivity and Seebeck coefficient. The steady-state oxygen permeability of Pr2 NiO4+? ceramics at 1173–1223 K, limited by both surface-exchange kinetics and bulk ionic conduction, is similar to that of La2NiO4+?. The phase transformation on cooling results in considerably higher electronic conductivity and oxygen permeation, but is associated also with significant volume changes revealed by dilatometry. At 973–1073 K, porous Pr2 Ni0:8Cu0:2O4+? electrodes deposited onto lanthanum gallate-based solid electrolyte exhibit lower anodic overpotentials compared to La2Ni0:8Cu0:2O4+?, whilst cathodic reduction decreases their performance.
A. V. Kovalevsky, V. V. Kharton, A. A. Yaremchenko, Y. V. Pivak, E. V. Tsipis, S. O. Yakovlev, A. A. Markov, E. N. Naumovich, J. R. Frade, J Electroceram (2007) 18, 205–218

A1837 – Bioactivity of wollastonite/aerogels composites obtained from a TEOS–MTES matrix

Organic–inorganic hybrid materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS), methyltrimethoxysilane (MTES), synthetic wollastonite powders and polydimethylsiloxane (PDMS) in an ethanol solution. Aerogels were prepared from acid hydrolysis of TEOS and MTES with different volume ratio in ethanol, followed by addition of wollastonite powder and PDMS in order to obtain aerogels with 20 wt% of PDMS and 5 wt% of CaO of the total silica. Finally, when the wet gels were obtained, they were supercritically dried at 260 °C and 90 bar, in ethanol. In order to obtain its bioactivity, one method for surface activation is based on a wet chemical alkaline treatment. The particular interest of this study is that we introduce hybrid aerogels, in a 1 M solution of NaOH, for 30 s at room temperature. We evaluate the bioactivity of TEOS–MTES aerogel when immersed in a static volume of simulated body fluid (SBF). An apatite layer of spherical-shaped particles of uniform size smaller than 5 microns is observed to form on the surface of the aerogels after 25 days soaking in SBF.
Jose Antonio Toledo-Fernandez, Roberto Mendoza-Serna, Victor Morales, Nicolas de la Rosa-Fox, Manuel Pinero, Alberto Santos, Luis Esquivias, J Mater Sci: Mater Med (2008) 19, 2207–2213

A1832 – Oxidation Mechanisms of Copper and Nickel Coated Carbon Fibers

Differential-Thermal Analysis (DTA) and X-ray diffraction analysis were applied to determine the mechanisms of high-temperature oxidation of copper- and nickel-coated carbon fibers. Both kinds of coatings were deposited by electroless plating onto the fiber surface. The as-deposited copper film was crystalline, whereas the nickel coating consisted of an amorphous Ni–P alloy. Coated fibers were heated from room temperature to 900 °C in air at 10 °C min-1. For the copper coating, the main oxidation product formed at low temperatures was Cu2O, while at higher temperatures was CuO. The crystallization of Ni–P took place at 280–360 °C with the formation of Ni and Ni3P. The final compounds were NiO, Ni2P and Ni3(PO4)2. After complete oxidation of the carbon fibers, copper and nickel-oxidized microtubes were obtained. Besides, while copper reduced the temperature of the fiber oxidation, nickel coatings increased the minimum temperature needed for this reaction.
M. Sanchez, J. Rams, A. Urena, Oxid Met (2008) 69, 327–341

A1831 – Improvement of the bioactivity of organic–inorganic hybrid aerogels/wollastonite composites with TiO2

Organic–inorganic hybrid aerogels containing P and Ti have been synthesized by supercritical drying of alkogels prepared by hydrolysis and poly-condensation of metalo-organic precursors under high-power ultrasound. These materials become bioactive when doped with Ca. Wollastonite particles (CaSiO3) were added as an active phase, instead of incorporating Ca into the aerogel atomic network. These particles had previously been precipitated and were then added to the sol. The aerogels were studied by Fourier transform infrared analysis, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction and N2 adsorption. The stress–strain behaviours were evaluated under compression to obtain the Young’s modulus. It was found that the incorporation of TiO2 into wollastonite-P2O5 hybrid aerogels increased their capacity to form apatite and, consequently, improving their bioactive response.
J. A. Toledo Fernandez, R. Mendoza-Serna, A. Santos, M. Pinero, N. de la Rosa-Fox, L. Esquivias, J Sol-Gel Sci Technol (2008) 45, 261–267

A1825 – Polymer-like C:H Thin Film Coating of Nanopowders in Capacitively Coupled RF Discharge

Nanopowders of amorphous SiO2, with typical particle sizes of 30–80 nm, were treated under the non-equilibrium plasma conditions, created by a capacitively coupled (CC) RF discharge formed in pure methane or ethane. The plasma gas flow rate varied between 0.02 and 0.06 slpm, with reactor pressures between 1000 and 5000 Pa, and applied RF power inputs between 700 and 1500 W. The plasma properties were monitored through measurements of the rotational temperature, as derived from the C2 5160 A ° Swan band and N2 second positive 3577 A ° band, and the atomic hydrogen excitation temperature, from the Hb, Hg and Hd lines during the powder treatment process. The compositions of the gases that passed through the plasma were analyzed by mass spectrometry. In spite of the evidence for the presence of CnH2n+2 and CnH2n (n = 1–3) species and acetylene in the discharge, the homogeneous formation of soot was not observed. At the same time, the introduced nanoparticles were observed to act as centers for the inception and growth of C:H thin coatings in the form of a polymer-like hydrocarbon layers, of thickness between <5 and 30 nm. The results of TEM, IR spectroscopy, thermo-gravimetric and precision calorimetric analysis performed on the treated powders provide evidence to the formation of an amorphous, high density C:H matrix on the particles’ surfaces.
A. Kouprine, F. Gitzhofer, M. Boulos, A. Fridman, Plasma Chemistry and Plasma Processing, Vol. 24, No. 2, June 2004

A1823 – Application of Cs salt of 12-tungstophosphoric acid supported on SBA-15 mesoporous silica in NOx storage

Cs salt of 12-tungstophosphoric acid (HPW) was deposited simultaneously at the external surface of the SBA-15 silica microcrystals and inside its mesoporous channels at loading of 60 wt% and Cs/W ratio in the range between 0.9 and 2, followed by impregnation of 1 wt% Pt. The performance of the Pt/CsHPW/SBA-15 composite materials was tested in the NOx storage. The optimal NOx storage capacity and efficiency were achieved at Cs/W of 1.5. The dispersion of CsHPW on SBA-15 led to a significant decrease of its crystal size (5–13 nm) compared with bulk HPW and HPW supported on titania (28–29 nm). Pt/CsHPW/SBA-15 displayed lower NOx absorption capacity but much higher absorption and desorption efficiency than the reference Pt/HPW and Pt/HPW/TiO2 materials. Consequently, Pt/CsHPW/SBA-15 displayed a better performance in short lean (2 min)—rich (1 min) absorption-desorption cycles. The novel Pt/CsHPW/SBA-15 nanocomposites presents the basis for improved storage material for NOx removal from lean exhaust gases in highly dynamic aftertreatment technologies.
M. V. Landau, P. M. Rao, S. Thomas, V. Pitchon, R. Zukerman, L. Vradman, and M. Herskowitz, Topics in Catalysis Vols. 42–43, May 2007

A1822 – Comparison of n-pentane reforming over Pt supported on amorphous and ?-Al2O3

The n-pentane reforming activity of Pt supported on nonhydrolytic amorphous Al2O3 (Pt/NH–Al2O3), was investigated and compared to the catalytic activity of Pt supported on crystalline ?-Al2O3. The Pt was introduced by (a) impregnation with either a solution of H2PtCl6 in water or a solution of platinum acetylacetonate (PtAcac) in toluene; (b) in situ introduction of a Pt precursor, either PtBr4 or cis-bis(benzonitrile)platinum dichloride, before gelation of the NH alumina. The rate-controlling step in the reforming of n-pentane for both amorphous and crystalline aluminas was found to be the reaction on the alumina acidic sites. The Pt/?-Al2O3 catalysts exhibit higher conversions of n-pentane and higher selectivity to isopentane, than the corresponding amorphous alumina samples. After 1.5 h at 400 C, the highest conversion of the ?-Al2O3-based catalysts was 47% with 20.3% selectivity to isopentane. The highest conversion of the NH–Al2O3-based catalysts under the same conditions was only 26% with 13.6% selectivity to isopentane. The high intrinsic Cl content (2.6 wt%) of the amorphous alumina was found to have a minor effect on the activity of the alumina, compared to the activity of the more ordered ?-alumina. Catalysts prepared by impregnation of the NH alumina with aqueous chloroplatinic acid, exhibited higher conversions compared to catalysts prepared by impregnation of the NH alumina with a solution of PtAcac in toluene. This result occurred in spite of the lower surface area and lower Pt dispersions of the chloroplatinic acid-impregnated catalysts, and is explained by the formation of microcrystalline surface structures and existence of surface chlorine.
Alon Dolev, Vladimir Gelman, Gennady E. Shter, Gideon S. Grader, Catalysis Letters Vol. 89, Nos. 3–4, September 2003

A1821 – Modification of Non-Hydrolytic Sol-Gel Derived Alumina by Solvent Treatments

The effect ofwetting non-hydrolytic derived alumina xerogelswithwater and organic solvents in the 20–70°C range on the alumina’s properties was investigated.Wetting with organic solvents does not affect the alumina. However, contact with water was found to change the sharp crystallization at?800°C to a continuous crystallization starting at ?450°C. Water treatment for a day at room temperature (RT) followed by second calcination decreased the surface area by 10%. This decrease in surface area is less pronounced with increasing wetting periods. On the other hand water treatment at 50–70°C followed by a second calcination resulted in a surface area increase of up to 15%. Upon water treatment the total pore volume has decreased from 0.65 (cm3/gr) to 0.48 (cm3/gr) and the average pore size decreased from 6.8 nm to 4.1 nm. The Cl content was found to be uneffected by the water treatment, remaining at ?2.5% wt.Wetting with water at elevated temperature (70°C) accelerated the morphological changes, eliminating the crystallization peak at 800°C in one hour. A dissolution-reprecipitation mechanism is suggested to explain the results. In addition, Mass-Spectroscopy of the effluent gas during heat treatment revealed the emission of CO2 and water upon phase transition into ?-Al2O3, at 1150–1300°C.
G.S. Grader, G.E. Shter, D. Avnir, H. Frenkel, D. Sclar, A. Dolev, Journal of Sol-Gel Science and Technology 21, 157–165, 2001

A1820 – Novel synthesis route to titanium oxides nanomaterials using soluble starch

A novel and easy synthesis route to mesoporous nanocrystalline TiO2 samples using soluble starch as the structural agent and mainly titanium(IV) isopropoxide as the inorganic precursor was described. The effect of key parameters, including soluble starch removal process, the solvent nature and the type of titaniumprecursorwere discussed.Using soluble starch in cyclohexane as non polar solvent, a surface area of 94 m2.g?1 associated with 23 nm crystallites size was obtained. TiO2 samples were characterized by means of N2 adsorption-desorption, X-ray Diffraction (XRD), TGDTA, Scanning ElectronMicroscopy (SEM) and ATR-FTIR spectroscopy.
H. Kochkar, M. Triki, K. Jabou, G. Berhault, A. Ghorbel, J Sol-Gel Sci Techn (2007) 42, 27–33

A1812 – Surface characterization and dissolution study of biodegradable calcium metaphosphate coated by sol–gel method

Coatings of biomedical implant surfaces by a bioactive calcium phosphate film render bioactivity to the implant surface and shorten the healing time. In this present study, calcium metaphosphate (CMP) sol was synthesized by sol–gel method and coated onto the titanium alloys (Ti-6Al-4V). CMP sol was first synthesized by reacting Ca(NO3)24H2O (Sigma–Aldrich 99%, USA) with (OC2H5)3P (Fluka 97%, Japan) in methyl alcohol. A stoichiometric Ca/P ratio of 0.5 was obtained by varying the amounts of the reactants. Sol was then coated on Ti-6Al- 4V substrates by spin coating. The coated-specimens were then dried at 70 C for 24 h, followed by a heat treatment at 650 C for 1 h. Structural and chemical properties of the coatings were evaluated using XRD, SEM, and EPMA. The dissolution property of the coated-CMP layer was investigated by immersing the samples in the simulated body fluid (SBF) for 1, 3, 7 and 21 days. The concentration of Ca2? released was measured using ICP. After heat treatment, SEM indicated a smooth and uniform CMP layer, with CMP grains of approximately 100 nm. The CMP phase was identified with d-CMP (JCPDS #9-363). After immersion in SBF, coatings were observed to be roughened and porous. The concentration of Ca2? in SBF was observed to increase over time, indicating continuous dissolution. The presence of titanium oxide phosphate compounds were also observed on CMP surfaces after immersion. It was thus concluded that the ability to control coating properties as well as the need for low heat treatment temperature offers advance for the use of CMP coating by sol–gel process on Ti-6Al-4V implant surfaces
Sunho Oh, Myung-Ho Han, Wan-Bin Im, Suk Young Kim, Kyo Han Kim, Changkook You, Joo L. Ong, J Sol-Gel Sci Technol (2010) 53, 627–633

A1805 – Synthesis of SiO2–SnO2 gels in water free conditions

A series of SiO2–SnO2 samples with various Sn/Si molar ratios (0.05–1.0) have been synthesized by the sol–gel technique from (Tetraethylorthosilicate) TEOS and Sn(CH3COO)4 precursors in water free conditions. The synthesis applied allowed obtaining the final product in monolithic (nonfractured upon drying) form with no use of drying control chemical additives. All samples are characterized by thermal analysis, XRD, and FTIR. The low temperature nitrogen adsorption measurements indicate the presence of both micro and mesopores. The samples containing less than 20 wt% of SnO2 show much higher surface area than SiO2 gel. The appearance of new bands at 1,048 and 882 cm-1 in the FTIR spectra could be related to stretching vibrations of the three dimensional Si–O–Sn network, which suggests that tin component has replaced silicon atoms in Si–O–Si structure.
Piotr Kirszensztejn, Adriana Kawa?ko, Agnieszka Tolinska, Robert Przekop, J Porous Mater (2011) 18, 241–249

A1797 – Preparation of MgO–Al2O3 binary gel system with mesoporous structure

A series of MgO–Al2O3 samples with MgO to Al2O3 molar ratio of 2:1, 1:1, 0.2:1, have been synthesized by a sol–gel technique from two different precursors of magnesium i.e. magnesium methoxide and metallic magnesium. Both series have been characterized by thermal analysis, XRD, and TEM. On the basis of the low temperature nitrogen adsorption the porous structure has been determined. It has been established that the structure of the binary gel system obtained with the use of metallic Mg as a precursor of MgO is much more uniform than when Mg(OCH3)2 is used, however, the samples with the spinel stoichiometry i.e. 1:1 obtained by either of the techniques differ distinctly from the others.
Piotr Kirszensztejn, Robert Przekop, Agnieszka Szymkowiak, Ewa Mackowska, Jerzy Gaca, Microporous and Mesoporous Materials 89 (2006) 150–157

A1794 – Low temperature synthesis of calcium cobaltites in a solid state reaction

This paper presents synthesis of calcium cobaltites of the nominal composition of Ca3Co4O9 prepared by the solid state reaction. The reaction between CaCO3 and Co3O4 was investigated at 700–900 °C during 20 h and at 800 °C during 2–30 h. Mass changes, phase composition and Co+3, Co+4 content were examined. Stability of the calcined specimens was tested by DTA/TG. It was found that two phases: Ca3Co4O9 and Ca3Co2O6 were present as a result of calcinations above 800 °C. On the other hand, the temperature of 750 °C was too low for calcium cobaltites to be synthesized. Mono-phase material with Ca3Co4O9 phase was obtained after calcinations at 800 °C but non-stoichiometry of the compound and its relation to the calcinations time were found. Once synthesized, the compound was stable up to 900 °C.
Pawe? Smaczy?ski, Ma?gorzata Sopicka-Lizer, Karolina Koz?owska, Julian Plewa, J Electroceram (2007) 18, 255–260

A1787 – The Effect of Heat Treatment on the Oxidation Mechanism of Blended Powder Cr3C2-NiCr Coatings

The advantageous oxidation and wear properties of Cr3C2-NiCr thermal spray coatings have resulted in them being extensively applied to combat erosion at high temperatures. Under these conditions, oxide layers take on an ever more significant role in determining the composite response. The response of blended powder-based carbide coatings for erosion applications has formed the basis for application of cermet-based coatings at elevated temperature. In this study, the oxidation mechanisms of as-sprayed and heat-treated Cr3C2-NiCr blended powder-based coatings are characterized. Interdiffusion between the coating phases with long-term exposure increased the Cr content of the matrix phase. This had a significant effect on the oxidation mechanism. The implications of the change in oxidation mechanism and oxide morphology on the coating response to high-temperature erosion are discussed.
S. Matthews, B. James, M. Hyland, Journal of Thermal Spray Technology, Volume 19(1-2) January 2010—119

A1785 – Photoelectrochemical characterization of the synthetic crednerite CuMnO2

High quality crednerite CuMnO2 was prepared by solid state reaction at 950 °C under argon flow. The oxide crystallizes in a monoclinically distorted delafossite structure associated to the static Jahn–Teller (J–T) effect of Mn3? ion. Thermal analysis showed that it converts reversibly to spinel CuxMn3-xO4 at *420 °C in air and further heating reform the crednerite above 940 °C. CuMnO2 is p-type, narrow semiconductor band gap with a direct optical gap of 1.31 eV. It exhibits a long-term chemical stability in basic medium (KOH 0.5 M), the semilogarithmic plot gave an exchange current density of 0.2 lA cm-2 and a corrosion potential of *-0.1 VSCE. The electrochemical oxygen insertion/desinsertion is evidenced from the intensity–potential characteristics. The flat band potential (Vfb = -0.26 VSCE) and the holes density (NA = 5.12 9 1018 cm-3) were determined, respectively, by extrapolating the curve C-2 versus the potential to the intersection with C-2 = 0 and from the slope of the Mott–Schottky plot. From photoelectrochemical measurements, the valence band formed from Cu-3d wave function is positioned at 5.24 ± 0.02 eV below vacuum. The Nyquist representation shows straight line in the high frequency range with an angle of 65° ascribed to Warburg impedance originating from oxygen intercalation and compatible with a system under mass transfer control. The electrochemical junction is modeled by an equivalent electrical circuit thanks to the Randles model.
B. Bellal, B. Hadjarab, N. Benreguia, Y. Bessekhouad, M. Trari, J Appl Electrochem (2011) 41, 867–872

A1777 – Effect of surfactants on the morphology of titania microspheres prepared by internal gelation process

Internal gelation process was employed for preparation of 0.3–1 mm sized microspheres of titania for their application in ion exchange columns. The conventional internal gelation process was modified by adding surfactant and oil emulsion in the feed broth, which introduced large pores in the structure of the material. The effects of concentration of hydrochloric acid, titanium, surfactant and hexamethylenetetramine to titanium ratio in the feed broth and temperature of calcination on the surface characteristics of the final product were studied. The conditions of preparation were optimized to obtain physically stable porous microspheres suitable for various applications. The resultant material was characterized by pore size distribution, pore volume, thermogravimetry, X-ray diffraction and SEM analyses. Ion exchange behaviour of the material was then studied by pH titration.
Sachin S. Pathak, I. C. Pius, R. D. Bhanushali, K. T. Pillai, J. V. Dehadraya, S. K. Mukerjee, J Porous Mater, November 2012

A1764 – Synthesis of BaTiO3 powder from barium titanyl oxalate (BTO) precursor employing microwave heating technique

Cubic barium titanate (BaTiO3) powder was synthesized by heating barium titanyl oxalate hydrate, BaTiO(C2O4)2 ×4H2O (BTO) precursor in microwave heating system in air at 500°C. Heating BTO in microwave above 600°C yielded tetragonal form of BaTiO3. Experiments repeated in silicon carbide furnace showed that BaTiO3 was formed only above 700°C. The product obtained was cubic.
Y. S. Malghe, A. V. Gurjar, S. R. Dharwadkar, Bull. Mater. Sci., Vol. 27, No. 3, June 2004, pp. 217–220

A1763 – Synthesis and characterization of highly ordered mesoporous YSZ by tri-block copolymer

Ahighly ordered mesoporous yttria-stabilized zirconia (YSZ) has been successfully prepared by evaporation-induced self-assembly method (EISA) using tri-block copolymer Pluronic F127 as a structure-directing agent and inorganic chlorides as precursors in a non-aqueous medium. The characterization of the mesoporous YSZ materials was carried out by using small angle X-ray diffraction (SAXRD), transmission electron microscopy (TEM) and N2 adsorption/desorption. The well ordered mesoporous YSZ is thermally stable up to 600?C with an average pore size of 5.4 nm and specific surface area of 90m2/g. Thewalls of mesoporous YSZ are composed of ?6.5 nm nano-crystalline domains.
I-Ming Hung, De-Tsai Hung, Kuan-Zong Fung, Min-Hsiung Hon, J Porous Mater (2006) 13, 225–230

A1762 – Preparation and characterization of CaTiO3–(Li1/2Nd1/4Sm1/4)TiO3 microwave ceramics by a sol–gel combustion process

A novel sol–gel combustion process was adopted to synthesize reactive ceramic powder with composition of 0.25 CaTiO3–0.75 (Li1/2Nd1/4Sm1/4)TiO3, and microwave dielectric ceramics were prepared at different sintering temperatures using the synthesized powder. The combustion behavior of citrate gel and the sintering feature of the synthesized powder were evaluated by using differential thermal analysis–thermogravimetric analysis and thermo-mechanical analysis techniques, respectively. The citrate gel exhibits a self-propagating behavior after being ignited in air at room temperature. The as-burnt powder is so highly reactive that it can be transformed into single-phase perovskite at 900 ?C and it can be sintered at 1100 ?C. The effects of sintering temperature on the density, microstructure, and dielectric properties of the sintered ceramics were investigated.
Z. Yue, Y. Zhang, Z. Gui, l. Li, Appl. Phys. A 80, 1757–1761 (2005)

A1761 – Preparation of Ca3Co4O9 by polyacrylamide gel processing and its thermoelectric properties

Ca3Co4O9 powder was prepared by a poly-acrylamide gel route in this paper. The effect of the processing on microstructure and thermoelectric properties of Ca3Co4O9 ceramics via spark plasma sintering were investigated. Electrical measurement shows that the Seebeck coefficient and conductivity are 170 lV/K and 128 S/cm, respectively, at 700 °C, yielding a power factor value of 3.70 · 10ÿ4 W mÿ1 Kÿ2 at 700 °C, which is larger than that of Ca3Co4O9 ceramics via solid-state reaction processing. The polyacrylamide gel processing is a fast, cheap, reproducible and easily scaled up chemical route to improve the thermoelectric properties of Ca3Co4O9 ceramics by preparing the homogeneous and pure Ca3Co4O9 phase.
Ying Song, Ce-Wen Nan, J Sol-Gel Sci Technol (2007) 44, 139–144

A1760 – Synthesis and characterization of novel Ca2Zn4Ti15O36 microwave ceramics derived from sol-gel powder

A novel microwave dielectric ceramics with composition of Ca2Zn4Ti15O36 (CZT) have been synthesized at different sintering temperatures, using citrate sol-gel derived powder. The sintering behavior and the phase identification of the powders were evaluated using differential thermal analysis-thermo gravimetric analysis and X-ray powder diffraction analysis techniques. The phase of CZT can be observed in the powder calcined at 900 °C. The single-phase of CZT, however, can only be obtained at sintering temperature of 1,000 °C or above. The single-phase CZT ceramics can be sintered into dense at 1,100 °C, exhibiting excellent microwave dielectric properties. The effects of sintering temperature on the density, microstructure, and dielectric properties of the sintered ceramics were investigated. The mechanism responsible for the change of dielectric properties with sintering temperature was also discussed.
F. Zhao, Z. X. Yue, Z. L. Gui, L. T. Li, J Electroceram (2008) 21, 120–123

A1759 – Effect of Si Content on the Oxidation Resistance of Ti3Al1?xSixC2 (x60.25) Solid Solutions at 1000–1400°C in Air

The oxidation behavior of Ti3Al1?xSixC2 (x 6 0.25) solid solutions was investigated in flowing air at 1000–1400 °C for up to 20 h. Similar to Ti3AlC2, Ti3Al1?xSixC2 (x60.15) solid solutions display excellent oxidation resistance at all temperatures because of the formation of the continuous ?-Al2O3 protective layers. However, Al2(SiO4)O formed during oxidation of Ti3Al1?xSixC2 (x =0.2 and 0.25) solid solutions at and above 1100°C, which is believed to be responsible for the deterioration of oxidation resistance of Ti3Al0.75Si0.25C2 at 1300°C. Additionally, Ti5Si3 was also found in the oxidized samples. This implies that Ti5Si3 precipitated from Ti3Al1?xSixC2 solid solutions during oxidation. But it has been proven that Ti5Si3 has little effect on the oxidation resistance of the material, which is attributed to an interstitial carbon effect.
J. X. Chen, Y. C. Zhou, Oxidation of Metals, Vol. 65, Nos. 1/2, February 2006

A1730 – Hydrogen Reduction of a Cu2O-WO3 Mixture

In the present work, the reduction kinetics of Cu2O-WO3 mixtures by hydrogen gas was studied by thermogravimetric analyses (TGA). The reduction experiments were carried out both isothermally and nonisothermally on shallow powder beds in the temperature interval 673 to 1073 K. During the experiments, the reductant gas flow rate was kept just above the starvation rate for the reaction to ensure that chemical reaction was the rate-controlling step. The composition and microstructures of the reaction products were analyzed after each experiment by X-ray diffraction (XRD) as well as by microprobe analyses. In the temperature interval 673 to 923 K, copper oxide was found to be preferentially reduced in the early stages of the experiment followed by the reduction of tungsten oxide. The reaction mechanism was found to be affected by a reaction/transformation in the starting copper-tungsten oxide mixtures in the temperature interval 923 to 973 K. At temperatures higher than 973 K, the reduction of the complex oxide formed was found to have a strong impact on the reaction kinetics. The activation energy was evaluated, from the isothermal as well as nonisothermal reduction experiments, for the two stages of reduction identified. The XRD and scanning electron microscopy (SEM) studies indicated the formation of a metastable solution of copper in tungsten at about 923 K. The advantage of the hydrogen reduction route toward the bulk production of alloy powders in the nanosize is demonstrated
U. Tilliander, R.E. Aune, S. Seetharaman, Metallurgical and Materials Transactions B, Volume 37B, April 2006—265

A1711 – Redox energetics of perovskite-related La(B1?xB?x)O3?? oxides where BB? is FeCo, MnCo, MnNi and CoCu

The enthalpy of oxidation of La(B1?xB?x)O3?? (x=0.25 and 0.75 for BB??FeCo, MnCo, MnNi and x=0.2 for BB ??CoCu) has been derived using solid solution models to analyse thermogravimetric measurements of oxygen non-stoichiometry vs. log(pO2) at 1273 K. For selected samples the enthalpy of oxidation has also been measured by TG-DSC, and the direct heat measurements agree well with the results from the solution models. The affinity for oxygen decreases when x in La(B1?xB?x)O3?? increases from 0.25 to 0.75. This trend may be extended to a larger range of x-values (x?[0,1]) when isotherms from the literature are included in the solution modelling. For the materials investigated in this work, the affinity for oxygen decreases in the order Mn0.75Ni0.25NMn0.75Co0.25NFe0.75Co0.25 (for x=0.25) and in the order Mn0.25Co0.75NFe0.25Co0.75NMn0.25Ni0.75 (for x=0.75). The Co0.80Cu0.20 containing material has the smallest affinity for oxygen among all the samples.
Egil Bakken, Paul I. Dahl, Camilla Haavik, Svein Stølen, Yngve Larring, Solid State Ionics 182 (2011) 19–23

A1697 – Thermal, chemical, and mineralogical characterization of ceramic tobacco pipes from Cyprus

This study is focused on simultaneous thermoanalytical investigations by TG/DTG-DTA technique applied for characterization of samples collected from archaeological site of Nicosia, Cyprus, dating to seventeenth century and gave new information on the firing technology. The ceramic samples derived from Ottomanic tobacco pipes were characterized by the related techniques such as X-ray powder diffraction for the mineralogical composition, and inductively coupled plasma-atomic emission spectrometry and micro-X-ray fluorescence spectroscopic analysis for the chemical content. It was found that they consisted mainly of quartz, calcite, feldspars, and micas. For the majority of the investigated ceramic samples, the thermal behavior investigation collaborates with their mineralogical findings, and resulted to the firing temperature at *700 C, due to the existence of calcite. Only in two samples with very high content in quartz, absence of calcite, low amounts of adsorbed water and of total mass loss, and absence of micas, the firing process resulted up to 1000 C.
J. A. Stratis, M. Lalia-Kantouri, El. Charalambous, A. Charalambous, N. Kantiranis, J Therm Anal Calorim (2011) 104, 431–437

A1677 – Physico-chemical properties of silica aerogels prepared from TMOS/MTMS mixtures

In the present work, results on the physico-chemical properties of the silica aerogels prepared by sol–gel process using mixtures of TMOS and MTMS as precursor are reported. The wide range of precursor mixture was studied with ratio of MTMS/TMOS in precursor mixtures as 0:100, 25:75, 50:50, 75:25, and 100:0 by volume. The gels with these precursor mixtures were successfully prepared using two step acid–base catalysis for gelation. Acetic acid (0.001 M) and NH4OH (1.5 M) were used for catalysis and resulting alcogels were subsequently dried by supercritical solvent extraction method. FTIR spectroscopy revealed that the aerogels show more intense peak at 1,260 and 790 cm-1 attributed to Si–CH3 resulting in more hydrophobic nature and these results were concurrent with adsorbed water content measurements made using Karl Fischer’s titration technique. The resulted aerogels were characterized using differential thermal analysis, thermogravimetric analysis and surface area measurements. The surface area measurements showed an interesting trend that the surface area increased from 395 to 1,037 m2/g with increase in MTMS content in the precursor mixture from 0 to 50% and then again decreased to 512 m2/g for further increase in MTMS content from 50 to 100% in the precursor mixture. It was observed from our studies that silica aerogels prepared using a starting mixture of 50% TMOS and 50% MTMS resulted in high moisture resistance (adsorbed water content of 0.721% w/w), low density of 90 kg/m3 and the highest surface area of 1,037 m2/g, which has great potential for catalysis support applications.
S. V. Ingale, P. B. Wagh, A. K. Tripathi, V. S. Kamble, Ratanesh Kumar, Satish C. Gupta, J Porous Mater (2011) 18, 567–572

A1676 – Kinetics of Reduction of NiO–WO3 Mixtures by Hydrogen

The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows: NiO-WO3 ? Ni-WO3 ? Ni-WO2 ? Ni-W From the experimental results, the Arrhenius activation energies of the three steps were evaluated for all of the studied compositions. The activation energy for the first step was calculated to be approximately 18 kJ/mol. For the second and third stages, the activation energy values varied from 62 to 38 kJ/mol for the second stage and 51 to 34 kJ/mol for the third stage depending on the Ni/(Ni+W) molar ratio in the precursors; the activation energy increased with increasing ratios. SEM images showed that the grain size of the final product was dependent on the Ni/(Ni+W) molar ratio; smaller grains were formed at higher nickel contents.
Hesham M. Ahmed, Abdel-Hady A. El-Geassy, Seshadri Seetharaman, Metallurgical and Materials Transactions B, Vol. 41B, 161, Février 2010

A1672 – Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture

Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of NiO-WO3 oxide precursors using H2-CH4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas–solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reduction–carburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.
Hesham M. Ahmed, Seshadri Seetharaman, Metallurgical and Materials Transactions B, Volume 41B, 173, Février 2010

A1671 – Oxidation Kinetics of AlN Under CO2 Atmosphere

IN view of the increasing recycling of aluminum, the remelting of the aluminum scrap and the consequent handling of the increasing amounts of dross/salt cake is receiving significant attention. Dross has been reported to contain such compounds as chlorides, Al2O3, AlN, Al4C3, SiO2, MgO, and even organic materials like ink and varnish.[1,2] It is important to recover the potentially valuable compounds from this by-product and modify those that can cause environmental damage. For instance, value-added MgAl2O4, AlON, SiAlON, and MgAlON may be prepared by using aluminum dross as raw material. However, the oxidation behavior of AlN in the aluminum dross needs to be understood in view of the importance of this phenomenon during the synthesis. Furthermore, AlN, when dumped in nature, can get hydrolyzed by rainwater to produce NH3 gas, which is highly undesirable. The oxidation behavior of AlN under O2 and air have already been investigated by Hou et al.,[3] and various kinetics models (linear or parabolic) have been proposed. Kim and Moorhead[4] reported that the oxidation kinetics of sintered aluminum nitride followed linear rate law, but became parabolic at higher temperatures. Recently, Chou[5,6] developed a series of models that can explicitly describe the oxidation reaction under oxygen atmosphere. However, the oxidation behavior of AlN has not been studied when greenhouse gas CO2 is employed as an oxidation agent. In the present work, the oxidation behavior of AlN in CO2 gas was investigated. Experiments were carried out at different temperatures under different CO2 flow rates. The oxidation process involving gas absorption, dissociation, and gas–solid reaction is complicated and requires a critical consideration of several factors. A simple model was developed in the present work to simulate the oxidation process.
Peng Li, Lidong Teng, Min Guo, Mei Zhang, SeshadriI Seetharaman, Metallurgical and Materials Transactions B, Volume 43B, 406, Avril 2012

A1667 – Influence of ferrous iron incorporation on the structure of hydroxyapatite

Iron is a vital element of cellular function within the body. High concentrations of iron can be found in the kidneys and the circulatory system. In bones and teeth it is present as a trace element. The use of iron-based compounds in combination with hydroxyapatite offers a new alternative for prosthetic devices. This work investigates the synthesis and processing of iron containing apatites as a possible new type of ceramic for biomedical devices. Stoichiometric and calcium deficient iron containing apatites were synthesized by a wet chemical reaction with di-ammonium-hydrogen-phosphate, calcium nitrate and a ferrous iron nitrate solution. A secondary phase of tri-calcium-phosphate (TCP) was observed after heat treatment of iron containing, calcium deficient, hydroxyapatite. The apatite structure was maintained after heat treatment of stoichiometric apatite, synthesized in the presence of iron. Sintering in air produced oxidation of Fe2+ to Fe3+, resulting in the formation of hematite as a secondary phase. The introduction of iron into the synthesis of hydroxyapatite causes: (i) an increase of the a-lattice parameter after synthesis and heat treatment in air; (ii) an increase in the c-lattice parameter after sintering in air.
R. Morrissey, L. M. Rodriguez-Lorenzo, K. A. Gross, Journal of Materials Science: Materials in Medicine 16 (2005) 387-392

A1664 – The oxidation behaviour of uniaxial hot pressed MoSi2 in air from 400 to 1400 C

MoSi2 samples were prepared by hot uniaxial pressing from a 2 mm grain-size powder of commercially available MoSi2. The oxidation behaviour of MoSi2 was systematically studied from 400°C to 1400°C, which includes the pest-oxidation temperature range. It was observed that the rate and mechanism for oxidation of MoSi2 change significantly with increasing temperature. Five temperature regimes have to be considered regarding both kinetic results and cross-sections: i) 400 < T < 550°C; ii) 550 T < 750°C; iii) 750 T < 1000°C; iv) 1000 T < 1400°C; v) T 1400°C. In the first range, pesting did not occur in samples that were free of cracks and residual stresses and the oxidation kinetics were governed by surface or phase boundary reactions. Above 550 C, there was a change in the physical properties of the oxidation products due to the evaporation of MoO3. The formation of Mo5Si3 was observed above 800°C showing that the thermodynamic previsions were satisfied above this temperature. At higher temperatures (>1000°C), the oxide scale became very protective and transport in the silica scale (amorphous and b cristobalite) governed the oxidation kinetics. The Mo5Si3 phase did not appear anymore at 1400°C, indicating that another oxidation mechanism has to be proposed.
S. Knittel, S. Mathieu, M. Vilasi, Intermetallics 19 (2011) 1207-1215

A1651 – Synthesis of the perovskite ceramic Li3xLa2/(3–x)?1/(3–2x)TiO3 by a chemical solution route using a triblock copolymer surfactant

The synthesis of the perovskiteLi3xLa2/(3–x)?1/(3–2x)TiO3 by a chemical solution route, using a triblock copolymer surfactant, PEOn–PPOm–PEOn, is described. This titanate is a non-hygroscopic fast lithium conductor and therefore is a good candidate for electrochemical applications. It is generally prepared by a conventional solid-state reaction (SSR) method. However this synthesis method does not allow the preparation of nanopowders or the formation of thin films. For these special purposes, synthesis by a chemical solution route, with the formation of a polymeric precursor during synthesis, has been investigated. By using the above-mentioned non-ionic surfactant, the preparation of nanopowders of complex oxides can be done. Furthermore, this way of synthesis leads to the formation of an intermediate polymeric precursor which can be easily spread on substrates to obtain films. We show that the formation of a pure phase of the perovskite Li3xLa2/(3–x)?1/(3–2x)TiO3 is highly dependent on the synthesis conditions, namely the presence of water in the solvent, the EO/metal ratio, the Li+ content in the precursor and the calcination temperature.
Thi Ngoc Ha Le, Mickaël Roffat, Quoc Nghi Pham, Stéphanie Kodjikian, Odile Bohnke, Claude Bohnke, J Sol-Gel Sci Technol (2008) 46, 137–145

A1626 – Hydrothermal synthesis of nanosized BaTiO3 powders and dielectric properties of corresponding ceramics

BaTiO3 fine powders were synthesized by hydrothermal method at 150 -C or 250 -C for 7 h, starting from a mixture of TiCl3+BaCl2 or TiO2+BaCl2. The size of the crystallites is close to 20 nm whatever the starting mixture and the reaction temperature. These powders are well crystallized and constituted of a mixture of the metastable cubic and stable tetragonal phases. The ceramics obtained after uniaxial pressing and sintering at 1250 -C for 10 h or 20 h present high densification (up to 99.8%). The Curie temperature (Tc) and the electrical permittivity (er) of the ceramics strongly depend on the type of titanium source that has been used for preparing the powder and on the sintering dwell time. Particularly, Tc is shifted towards lower temperature when TiCl3 is used. The permittivity value at Tc of BaTiO3 sintered at 1250 -C for 10 h reaches 7000 and 11,000 with respectively TiCl3 and TiO2 used as titanium source.
Madona Boulos, Sophie Guillemet-Fritsch,T, François Mathieu, Bernard Durand, Thierry Lebey, Vincent Bley, Solid State Ionics 176 (2005) 1301 – 1309

A1615 – Effect of Co Content Upon the Bulk Structure of Sr- and Co-doped LaFeO3

The bulk structure was investigated for Fe-based perovskite-type oxides with the formula La0.6Sr0.4 CoyFe1-yO3-d (y = 0.1, 0.2, and 0.3). The materials were confirmed to be stoichiometric with respect to oxygen under ambient conditions and the structural features were then further characterized under different environments as a function of temperature. Under reducing atmospheres, the degree of reduction increased with Co content, suggesting the presence of preferential oxidation of Fe over Co. Under milder conditions, oxygen vacancy formation was not proportional to Co content, which was likely caused by an electronic structure transition. The unit cell parameters were also shown to strongly depend upon Co content, temperature, and environment. A rhombohedral to cubic transition occurred at lower temperatures for higher Co content, but showed less dependence upon environment. A change in the thermal expansion behavior occurred at the temperature where oxygen vacancies formed leading to two regions of linear thermal expansion. The use of lattice parameters compared to dilatometry allowed for the simultaneous monitoring of unit cell symmetry and expansion behavior so the link between thermal properties and unit cell symmetry could be firmly established.
John N. Kuhn, Umit S. Ozkan, Catal Lett (2008) 121, 179–188

A1610 – Formation of WC powders using carbon coated precursors

This paper deals with the formation of tungsten carbide from carbon coated tungstic oxide precursors. This study makes use of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). DSC and TGA data for both coated and mixed 17.2 wt% carbon containing tungstic oxide demonstrate the superiority of the coated precursor in the formation of tungsten carbide, as conversion is initiated at lower temperature. XRD patterns of products from each 100°C isotherm from 900–1400°C, inclusive, illustrate the formation as it proceeds through lower oxides into tungsten then carburizes into tungsten carbide for both the mixed and coated samples.
G. A. Swift, R. Koc, Journal of Materials Science, Volume 35, Issue 9, pp 2109-2113

A1608 – Formation studies of TiC from carbon coated TiO2

This paper deals with the formation of titanium carbide from carbon coated titanium dioxide precursors. This study makes use of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and both scanning and transmission electron microscopy (SEM and TEM). DSC curves of both coated and mixed 33.2 wt % carbon containing titania demonstrates the superiority of the coated precursor by exhibiting both more reactions and reactions at lower temperatures than the mixed powder. Weight loss as powders were reacted in argon at varying temperatures was measured using TGA, while heat flow vs. temperature was measured by DSC. The weight loss allowed for calculation of the activation energy of TiC via the formation of various lower oxides of titanium. The activation energy was calculated as 731.6 ± 24.2 kJ/mol. XRD was used to characterize the products resulting from the reaction of the carbon coated precursor at isotherms at each 100 °C interval from 1100 to 1500 °C, inclusive. These diffraction patterns support the hypothesis that the TiC formation proceeds through the formation of lower oxidation states of titanium.
G. A. Swift, R. Koc, Journal of Materials Science, Volume 34, Issue 13, pp 3083-3093

A1607 – Tungsten powder from carbon coated WO3 precursors

This paper deals with the formation of tungsten powder from carbon coated tungstic oxide precursors. This study makes use of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). TGA data allowed for calculation of the activation energy as 626 ± 18.2 kJ/mol. XRD characterized the products resulting from the reaction of the carbon coated WO3 for each isotherm. These diffraction patterns support the hypothesis that reduction to W proceeds through the formation of lower oxidation states. This is the first isolation of a metal powder using the carbon coated precursor process
Geoffrey A. Swift, Rasit Koc, Journal of Materials Science ,Volume 36, Issue 4, pp 803-806

A1606 – On the influence of the milling time in the Curie temperature of Fe56Co7Ni7Zr10B20 investigated by magnetic thermogravimetric analysis

Magnetic thermogravimetric analysis (TGM) was used to investigate the influence of the milling time (tmill) in the Curie temperature (TC) of nanocrystalline powders and of a melt-spun amorphous ribbon with composition Fe56Co7Ni7Zr10B20. The TGM analysis was carried in a continuous flow of 99.99% pure argon from room temperature up to 1250 K. A magnetic field of 100 Oe was applied throughout the measurements. Nanopowders of Fe56Co7Ni7Zr10B20 were produced by mechanical alloying the samples in an argon atmosphere for milling times ranging from 1 to 100 h. The samples were characterized by X-ray diffraction and by scanning electron microscopy. The average particle size decreased from 45.4 nm for a powder milled for 1 h to 5 nm after being milled for 100 h. Moreover, TC (=1126.4 ± 4.4 K) was found to be nearly independent of tmill while for the melt-spun amorphous ribbon it was found to be substantially smaller (TC = 482 K). This is a clear indication that TC is quite sensitive to the degree of amorphosity present in the sample. The activation energy associated to the crystallization process was estimated from DSC data by using the Kissinger’s method to be 193 kJ/mol.
G. F. Barbosa, F. L. A. Machado, A. R. Rodrigues, W. M. Azevedo, J Therm Anal Calorim, 2011

A1605 – All alkoxide route to manganate and coboltate perovskite films and powders: effects of processing parameters

Manganate and cobaltate perovskites having the general formula ABO3 have many technologically important applications. Here we present all alkoxide based routes to manganate and coboltate perovskite films and nano-phase powders of the compositions; LCMO (La0.67 Ca0.33MnO3), LSMO (La0.75Sr0.25MnO3), LNCMO (La0.33 Nd0.33Ca0.33MnO3), LBSMO (La0.75Ba0.125Sr0.125MnO3) and LSCO (La0.50Sr0.50CoO3). The Mn and Co (oxo) methoxy-ethoxide precursors were prepared by reaction of MnCl2 or CoCl2 with 2 Kmoe in methoxy-ethanol-toluene. After hydrolysis of the alkoxide solutions by atmospheric air all systems produced X-ray and electron diffraction amorphous gels of high elemental homogeneity, and the IR spectra showed that they consisted of hydrated oxo-carbonates. Heating in air resulted in similar weight-loss curves for all studied gels passing; loss of H2O in the range 20–300 °C, decomposition of carbonate groups into oxide and CO2 in the temperature range 300–700 °C, and in some cases loss of a small amount of oxygen in the temperature range 700–1,000 °C. The pure perovskites were obtained at 690–770 °C with heat rates of typically 5–20 °C min-1 without annealing. Perovskites could also be obtained at 550 °C by annealing, but these perovskites are prone to be A-site ion inhomogeneous according to the TEM EDS studies, which was not the case for the perovskites heat-treated to at least the carbonate decomposition temperature.
Gunnar Westin, Annika Pohl, Mikael Ottosson, Koroush Lashgari, Kjell Jansson, J Sol-Gel Sci Technol (2008) 48, 194–202

A1603 – DFT modeling, UV-Vis and IR spectroscopic study of acetylacetone-modified zirconia sol-gel materials

Theoretical and spectroscopic studies of a series of monomeric and dimeric complexes formed through the modification of a zirconium butoxide precursor with acetylacetone and subsequent hydrolysis and/or condensation have been performed by applying DFT/B3LYP/6-31+ +G(d) and highly accurate RI-ADC(2) methods as well as IR and UV-Vis transmittance and diffuse reflectance spectroscopies. Based on DFT model calculations and simulated and experimental UV-Vis and IR spectra of all the studied structures, the most probable building units of the Zr(IV)–AcAc gel were predicted: the dimeric double hydroxo-bridged complex Zr2(AcAc)2(OH)4(OH)2br and the monooxo-bridged complex Zr2(AcAc)2(OH)4Obr·2H2O. In both structures, the two AcAc ligands are coordinated to one Zr atom. The observed UV-Vis and IR spectra of Zr(IV)-AcAc gel were interpreted and a relation between the spectroscopic and structural data was derived. The observed UV-Vis bands at 315 nm and 298/288 nm were assigned to partial ligand–metal transitions and to intra-/inter-AcAc ligand transitions, respectively.
Ivelina Georgieva, Nina Danchova, Stoyan Gutzov, Natasha Trendafilova, J Mol Model (2012) 18, 2409–2422

A1600 – Photo- and radiation-induced preparation of Y2O3 and Y2O3:Ce(Eu) nanocrystals

A convenient method for preparation of pure and doped yttrium oxide was developed, which is based on irradiation of solutions containing yttrium nitrate and ammonium formate with UV light or accelerated electrons. Solid phase formed under irradiation was consequently calcined at 500 °C or higher temperatures to obtain nanocrystalline yttrium oxide. Addition of small amount of cerium(III) or europium(III) nitrates to irradiated solutions resulted in doping of yttrium oxide with Ce(III) or Eu(III) ions. Under both types of irradiation, the method yields material with high specific surface area, consisting of spherical nanoparticles 25–100 nm in diameter depending on preparative conditions and post-radiation treatment and with narrow size distribution. In the doped oxides (Y2O3:Ce or Y2O3:Eu), radioluminescence spectra typical for Ce3? or Eu3? doped oxide structures were observed.
Vaclav Cuba, Tereza Pavelkova, Jan Barta, V?tezslav Jary, Martin Nikl, Ivo Jakubec, J Nanopart Res (2012) 14, 794

A1587 – Stability and Thermal Expansion of Na+-Conducting Ceramics

An impedance spectroscopy study of sodium cation-conducting ceramics, including layered compounds Na0.8Ni0.4Ti0.6O2, Na0.8Fe0.8Ti0.2O2, Na0.8Ni0.6Sb0.4O2 (structural type O3), Na0.68Ni0.34Ti0.66O2 (P2 type), and NASICON-type Na3Si2Zr1.88Y0.12PO11.94 and Na3.2Si2.2Zr1.88Y0.12P0.8O11.94, showed that their transport properties are essentially independent of partial water vapor pressure at temperatures above 420 K. In the low-temperature range, increasing vapor partial pressure from approximately 0 (dry air) up to 0.46 atm. leads to a reversible increase in the conductivity. The sensitivity of studied materials to air humidity is strongly affected by the ceramic microstructure, being favored by larger boundary area and porosity. Maximum stability in wet atmospheres was found for NASICON ceramics, which also exhibit the highest cationic conduction. The average thermal expansion coefficients at 300–1173 K are in the range (13.7–16.0) × 10?6 K?1 for the layered materials and (5.9–6.5) × 10?6 K?1 for NASICON-type ceramics.
O.A. Smirnova, R.O. Fuentes, F. Figueiredo, V.V. Kharton, F.M.B. Marques, Journal of Electroceramics, 11, 179–189, 2003

A1586 – Preparation and characterization of nanocrystalline CoFe2O4 deposited on SiO2: in situ sol–gel process

In situ base catalyst assisted sol–gel process is used for the synthesis of nanocrystalline CoFe2O4 deposition on SiO2 particles. The SiO2 particles were prepared using base catalyst assisted sol–gel process and the consecutive formation and deposition of nanocrystalline CoFe2O4 on SiO2 particles was monitored using Powder X ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric And Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy (SEM–EDS) and High Resolution Transmission Electron Microscopy (HRTEM). The crystallite size of CoFe2O4 is calculated using Scherrer’s formula and it is found to be 8 nm. The HRTEM images and selective area electron diffraction (SAED) results confirmed the formation of nanocrystalline CoFe2O4 particles deposited over SiO2 spheres.
I. Prakash, N. Nallamuthu, P. Muralidharan, M. Venkateswarlu, Manjusri Misra, Amar Mohanty, N. Satyanarayana, J Sol-Gel Sci Technol (2011) 58, 24–32

A1574 – Sol-Gel Synthesis and Pyrolysis Study of Oxyfluoride Silica Gels

Silicon oxyfluoride materials are synthesized by the sol-gel method using triethoxyfluorosilane as precursor, bearing the Si F bond. SiO(2?0.5x)Fx gel preparation requires peculiar experimental control of hydrolysis and condensation reactions. Maintenance of the Si F bond during gelling, heating and aging was studied in the case of processes carried out under an argon atmosphere or in air. Fluorine contents in resulting samples were quantified by FT-IR and X-ray photoelectron spectroscopy (XPS); specific surface area and porosity of powdered samples were determined by N2 adsorption. The thermal stability of oxyfluoride gels was studied by thermogravimetric-mass spectrometric (TG-MS) coupled analyses during heat treatment, under He flow. Mass spectra recorded during principal weight losses indicate the release of variously fluorinated silicon species resulting from Si F/Si O exchange reactions. The evolution of these species was observed at different temperatures, depending on gelling conditions. In particular, degradation of Si F moieties was prominent for gels aged in air, whereas samples processed under an argon atmosphere preserve the Si F bond up to 300°C.
Renzo Campostrini, Marco Ischia, Giovanni Carturan, Lidia Armelao, Journal of Sol-Gel Science and Technology 23, 107–117, 2002

A1573 – The hydrolytic route to Co-porphyrin-doped SnO2 gas-sensing materials. Chemical study of Co-porphyrin versus Sn(IV) oxide interactions

SnO2 and SnO2 + Co-porphyrin solids were prepared from SnCl4 in propanol and hydrolyzed to sol. Thermal behavior of samples obtained at 110 °C was studied in the 20–600 °C interval by thermal analysis coupled with mass spectrometry for identification of released species. The original samples maintain residual Sn–OR, Sn–OH and Sn–Cl groups up to 350 °C. The sample doped with 1% Co-porphyrin differs for a significant presence of residual Sn–Cl species, accounting for SnCl4 release in the 300–340 °C range. 119Sn solid state NMR analysis reveals disordered SnO2 species in the sample heated at 250 °C and non-uniform SnO6 units in the SnO2 + Co-porphyrin sample at 110 °C, due to persistence of Sn–OR and Sn–OH groups. This complexity is lost at 250 °C. X-ray diffraction analysis confirms all these data. The sensing efficiency of these materials versus alcohols is ascribed to the presence of an open, incomplete SnO2 structure, which is more pronounced in the Co-porphyrin-doped sample.
Emanuela Callone, Giovanni Carturan, Marco Ischia, Mauro Epifani, Angiola Forleo, Pietro Siciliano, Roberto Paolesse, Inorganica Chimica Acta 361 (2008) 79–85

A1572 – Synthesis, Characterization and Photocatalytic Activity of TiO2 Powders Prepared Under Different Gelling and Pressure Conditions

Homogeneous TiO2 gel powders were prepared by hydrolysis and condensation of titanium(IV) iso-propoxide with HCl or SnCl2 catalysts, by working under reduced pressure or in air. Ti(IV) alkoxide was previously modified by reaction with formic or acetic acid, used as chelating ligands, when gelation was performed in acidic catalysis. Crude TiO2 xerogels were purified by water reflux treatment in order to induce a low temperature crystallisation to the anatase phase. Both crude and purified TiO2 samples were characterised by XRD, FT-IR, SEM, and N2 adsorption analysis. Thermoanalyses (TG, DTA, DTG, TG-MS, TG-GC-MS) were carried out to quantify the residual organic components in the crude TiO2 gels and to obtain stoichiometric formulas to describe their chemical compositions. XRD data of purified TiO2 powders were processed by means of a Rietveld refinement procedure to determine TiO2 polymorphs, crystallite sizes and cell parameters, before their use in photocatalytic tests. The photoactivity of the purified TiO2 anatase powders was studied by using 4-nitrophenol degradation as “probe” reaction carried out in a batch and/or a membrane photoreactor. Samples prepared by using formic acid or SnCl2 were the most photoactive, whereas specimens gelled under vacuum treatment showed detrimental effects.
Marco Ischia, Renzo Campostrini, Luca Lutterotti, Elisa Garcialo-Lopez, Leonardo Palmisano, Mario Schiavello, Fabrizio Pirillo, Raffaele Molinari, Journal of Sol-Gel Science and Technology 33, 201–213, 2005

A1561 – Formation, densification and properties of sol–gel TiO2 films prepared from triethanolamine-chelated soluble precursor powders

Amorphous, soluble powders were synthesized with triethanolamine (TEA) as chelating agent as precursors for TiO2 sol–gel solutions. Dip coating on glass substrates and subsequent annealing yielded thin films with excellent optical properties. Furthermore as-dried films were scraped of substrates, annealed at different temperatures and characterized in order to investigate the structural changes during processing. The observations were systematically compared with previous studies on precursor powders based on acetylacetone. Results indicate that tri- ethanolamine provides both a sufficient hydrolytical stability of the Ti-precursor during coating and an adequate plasticity of the film material throughout thermal densification. These characteristics significantly improve the practical workability of the respective process. Additionally former assumptions regarding the relationship between film properties and intermediate structural features were verified and refined.
Matthias Bockmeyer, Peer Löbmann, J Sol-Gel Sci Technol (2008) 45:251–259

A1560 – Synthesis and Characterization of Photocatalytic Porous Fe3+/TiO2 Layers on Glass

Wet chemical synthesis and preliminary photocatalytical characteristics of titania and Fe(III)-containing TiO2 layers are presented. A highly stable coating colloids could be prepared under base- as well as acid-catalyzed condensation conditions. Structural properties of the as-prepared wet gels and sintered films were investigated using SEM, TEM, XRD as well as optical absorption spectroscopy, DTA-TG analysis and photomineralisation studies. X-ray amorphous wet titania gel layers start to crystallize at 500?C forming the characteristic anatase phase. In the presence of iron ions (Fe/Ti = 1), nanocrystalline FeTiO3 ilmenite phase forms. Both TiO2 and Fe-containing TiO2 films demonstrate a photocatalytic activity in the process of the photomineralization of dichloroacetic acid.
Natalie Smirnova, Anna Eremenko, Olga Rusina, Werner Hopp, Lubomir Spanhel, Journal of Sol-Gel Science and Technology 21, 109–113, 2001

A1559 – Soluble Powders as Precursors for TiO2 Thin Films

Amorphous precursor powders have proven to be highly advantageous for the sol–gel processing of TiO2 thin films. Oxide yield, density, solubility, and thermal degradation of powders prepared under various conditions were determined; the thermoanalytical data could be assigned to the oxidative decomposition of different organic constituents. Certain powders are suitable for the preparation of alcohol-based sols, whereas also aqueous coating solutions can be prepared from others. Thin films prepared from both systems show excellent adhesion and optical properties when deposited on borosilicate glass substrates
Peer Löbmann, Journal of Sol-Gel Science and Technology 33, 275–282, 2005

A1558 – Sol–gel preparation of calcium titanium phosphate: viscosity, thermal properties and solubility

Calcium titanium phosphate (CTP) was prepared by the sol–gel route in order to prepare suitable coatings. This work addresses the question of how to prepare stable CTP sols. Their rheological properties as a function of process parameters like solid loading and water content are investigated. It was found that an increased solid loading as well as an increased water content lead to an increased initial viscosity as well as a more pronounced ageing induced viscosity rise. In addition, the thermal behavior of the resulting xerogels was analyzed. Furthermore, we studied the ion release behavior of the xerogels when brought in contact with water. Results suggest that calcium titanium phosphate shows a diffusion controlled ion release mode with a preferential release of Ca
M. Dressler, J. Bornstein, M. Meinel, U. Ploska, S. Reinsch, V. D. Hodoroaba, D. Nicolaides, K. J. Wenzel, J Sol-Gel Sci Technol (2012) 62:273–280

A1555 – Low Temperature Bonding of Ceramics by Sol-Gel Processing

Sol-gel bonds were produced between smooth, clean silicon or polycrystalline alumina substrates by spin-coating solutions containing partially hydrolysed silicon alkoxides onto both substrates. The two coated substrates were assembled and the resulting sandwich was fired at temperatures ranging from 300 to 600?C. The influence of the sol-gel chemistry on the film microstructure and interfacial fracture energy was investigated using a wide range of techniques, including ellipsometry, FTIR, TG-DTA, rheology,TEMand micro-indentation. For silicon wafers, an optimum water-alkoxide molar ratio of 10 and hydrolysis water pH of 2 were found. Such conditions led to relatively dense films (>90%), resulting in bonds with significantly higher fracture energy (3.5 J/m2) than those obtained using classical water bonding (typically 1.5 J/m2). Aging of the coating solution was found to decrease the bond strength. Poly-crystalline alumina substrates were similarly bonded at 600?C; the optimised silica sol-gel chemistry yielded interfaces with fracture energy of 4 J/m2.
C.J Barbé, D.J. Cassidy, G. Triani, B.A. Latella, D.R.G. Mitchell, K.S. Finnie, J.R. Bartlett ,J.L. Woolfrey, G.A. Collins, Journal of Sol-Gel Science and Technology 19, 321–324, 2000

A1550 – Defect Chemical Modeling of (La,Sr)(Co,Fe)O3??

Different defect chemical models for calculation of ionic and electronic defect concentrations are discussed regarding their applicability to transition metal perovskite-type oxides (ABO3?±) with large ranges of oxygen non-stoichiometry. A point defect model, which allows simultaneous consideration of three different B-site species concentrations as a function of the oxygen partial pressure is compared to a simple point defect model, considering only two different B-site species. Additionally, a model assuming electrons/holes as negative resp. positive electronic charge carriers is presented. Further, models involving association of point defects in different complexes are discussed. Examples are given for fits of experimental data of La1?x SrxBO3?? (x = 0.6, B = Fe, Co) to selected models in the temperature range 700–900?C and oxygen partial pressures 10?5 < pO2/atm < 1.
Edith Bucher, Werner Sitte, Journal of Electroceramics, 13, 779–784, 2004

A1538 – Synthesis of YAP nanopowder by a soft chemistry route

Polycrystalline fine powder of YAlO3 (YAP) was synthesized by the modified polymeric precursor method. A preliminary gradual pyrolytic decomposition under nitrogen flux was crucial in the removal process of organic residues to avoid the formation of molecular level inhomogeneities. YAP single phase was crystallized at temperatures between 950 ?C and 1000 ?C using chemically homogeneous ball-milled amorphous particles and very fast heating rates, corresponding to the lowest synthesis temperature of pure YAP nanopowder by soft chemistry routes.
J.F. Carvalho, F.S. De Vicente, S. Pairis, P. Odier, A.C. Hernandes, A. Ibanez, Journal of the European Ceramic Society 29 (2009) 2511–2515

A1528 – Synthesis and thermal decomposition of a novel zirconium acetato-propionate cluster: [Zr12]

This work reports a novel Zirconium acetato-propionate complex herein called [Zr12] obtained by reaction of zirconium acetylacetonate Zr(acac)4 with propionic acid. The molecular structure has been determined by X-ray diffraction on single crystals and proposed to be [Zr12(m3-O)16(CH3CH2CO2)12(CH3CO2)8(m2-CH3CH2CO2)4]. This cluster involves oxo/hydroxo bonds in the direct surrounding of the metallic center. The decomposition of [Zr12] has been studied by thermal analysis and compared to Zr(acac)4. Its temperature of decomposition is much lower than for acetylacetonate derivative. In consequence, the formation of ZrO2 is easier from [Zr12] than from Zr(acac)4. This phenomenon highlights the influence of the molecular structure on the process of decomposition. The local surrounding of Zr in [Zr12] and in ZrO2 are very close, while it is markedly different in Zr(acac)4.This difference of environment of the metallic ions is at the origin of the huge difference of thermal behavior of both compounds.
Sarah Petit, Stéphanie Morlens, Zeming Yu, Dominique Luneau, Guillaume Pilet, Jean-Louis Soubeyroux, Philippe Odier, Solid State Sciences 13 (2011) 665e670

A1515 – Abnormal High Growth Rates of Metastable Aluminas on FeCrAl Alloys

Experimental evidence in high temperature oxidation of alumina-forming alloys has accumulated that the overall growth kinetics of the oxide scale are slower for 1000?C, where the stable ?-Al2O3 phase predominates, than for 900?C where metastable ? -Al2O3 and/or ?-Al2O3 polymorphs predominate. This intriguing behaviour has been unanimously related to the substantial presence of twin boundaries and the cation vacancy network intrinsic to the metastable aluminas allowing faster diffusion than in the nearly close packed corundum structure. This paper shows that this abnormal growth rate accompanying the presence of stable alumina polymorphs in platelets or needle-like morphology is rather due to the formation of a corundum-alumina-rich compact layer from an outer metastable layer by the concomitant sintering at the intersection vertices of the platelets and secondary recrystallization in these platelets. These phenomena are illustrated from oxidation tests performed on thin FeCrAl foils in both a conventional muffle furnace (designed by AET) and thermogravimetric analysis furnace (TGA) over the temperature range of 800–1300?C using field emission scanning electron microscope (FEG-SEM), transmission electron microscope (TEM), electron probe microanalysis (EPMA), atomic force microscope (AFM), grazing incidence X-ray diffraction (GIXRD) and image analysis (IA) techniques.
H. El Kadiri, R. Molins, Y. Bienvenu, M. F. Horstemeyer, Oxidation of Metals, Vol. 64, Nos. 1/2, August 2005

A1509 – Conception, elaboration and characterization of silica-zirconia based nanostructured optical fibres obtained by the sol-gel process

This paper presents an original nanostructured optical fibre obtained by the sol-gel process. The studied fibre is composed with zirconia nanocrystals dispersed inside an amorphous silica matrix as core surrounded by a pure silica cladding. The conception and the elaboration of the fibre are described, as well as its structural and optical characterization. A preliminary study of the rheological properties of the initial silica-zirconia sol has been realized to determine the evolution of the sol behaviour as a function of the time .The introduction of ytterbium ions in the core composition is also investigated and the luminescence properties of the fibre are exposed and discussed.
Brasse Gurvan, Restoin Christine, Auguste Jean-Louis, Roy Philippe, Leparmentier Stephanie, Blondy Jean-Marc, WSEAS TRANSACTIONS on ADVANCES in ENGINEERING EDUCATION, Issue 2, Volume 6, February 2009

A1487 – Influence of Ni substitution on redox properties of In2(1?x) Ni2xTiO5?? oxides

The thermal behavior of mixed metal oxides with nominal compositions of In2(1?x)Ni2xTiO5?? where 0.0 ? x ? 0.2, were investigated by recording their temperature programmed reduction (TPR). The samples were synthesized by ceramic route and analyzed for phase composition using powder X-ray diffraction. The TPR profile of pristine In2TiO5 indicated the reduction of In3+, which takes place predominantly over the other species Ti4+ in In2TiO5 sample. Ni substitution at In3+ site induced ease in reducibility as indicated by lowering of onset reduction temperature and Tmax. Moreover, it also facilitated the reduction of otherwise non reducible cation, Ti4+. Ni metal initially formed by reduction, dissociates and activates hydrogen which then reacts and reduces the oxide (even Ti4+), a case of hydrogen spillover. The metallic Ni forms an alloy Ti2Ni with reduced Ti metal and ?In3Ni2 alloy with the reduced In metal as evident by XRD and XPS results of the reduced residue of 20% Ni doped (In1.6Ni0.4TiO5??) sample. Due to formation of new alloy phases of ?In3Ni2 and Ti2Ni, the rate of hydrogen adsorption diminishes which slows down further hydrogen activation and consequent further Ti4+ reduction.
A.M. Banerjee, M.R. Pai, Jagannath, S.R. Bharadwaj, Thermochimica Acta, 516 (2011) 40–45

A1486 – Influence of the processing parameters of slurries for the deposit of nickelate thick films

Thick films cathodes for Solid Oxide Fuel Cells (SOFC) are prepared by dip-coating slurries made of several lanthanum nickelate oxide powders onto yttria stabilized zirconia (YSZ) substrates. The processing parameters for the slurries preparation and the multilayers coating have been optimized to obtain homogeneous, crack-free, thick and adherent films after heat treatment
S. Castillo, R.F. Cienfuegos, M.L. Fontaine, P. Lenormand, P. Bacchin, F. Ansart, Materials Research Bulletin 42 (2007) 2125–2131

A1472 – Estimate of firing temperatures through bone-based chalcolithic decorated pottery

Guadiana River Chalcolithic middle basin (Badajoz, Spain) pottery was in many cases decorated with bone, which suffers a hydroxyapatite to b tri-calcium phosphate transformation while firing. The evolution of physico-chemical characteristics of bone decorations and experimentally heated fossil bone as a function of temperature through 1) major XRD planes, and 2) OH librational mode at 630 cm–1 in the FTIR spectra let us establish a correlation between the physico-chemical features and firing temperature, allowing the estimate of firing temperatures for bone decorated pottery. What is a reliable criterion to differentiate over potters behavior and skill during the pottery production.
C. Odriozola, J. M. Martínez-Blanes, Journal of Thermal Analysis and Calorimetry, Vol. 87 (2007) 1, 135–141

A1426 – Carbothermal reduction of the YSZ–NiO solid oxide fuel cell anode precursor by carbon-based materials

The thermal behavior of the yttria-stabilized zirconia (YSZ) and nickel oxide (YSZ–NiO) composite mixtures with the addition of graphite, multiwall carbon nanotubes and functionalized multiwall carbon nanotubes was studied. The YSZ–NiO composite is the precursor of the YSZ–Ni anode of solid oxide fuel cells. The anode exhibits a porous structure, which is usually obtained by the addition of carbon containing pore formers. Thermal analysis and X-ray diffraction evidenced that the properties of carbonaceous materials (C) and atmosphere have a strong influence on the thermal evolution of the reactions taking place upon heating the anode precursor. The dependence of both the carbon content and the chemical nature of the ceramic matrix on the thermal behavior of the composite were investigated. The discussed results evidenced important features for optimized processing of the anode.
E. Arico, F. Tabuti, F. C. Fonseca, D. Z. de Florio, A. S. Ferlauto, J Therm Anal Calorim (2009) 97, 157–161

A1400 – Nano structure et propriétés de revêtements d’alumine obtenus par dépôt chimique en phase vapeur à partir d’isopropoxyde d’aluminium

Des revêtements d’alumine ont été préparés par la technique MOCVD, en utilisant le tri-iso-propoxyde d’aluminium comme précurseur, sur des substrats d’acier inoxydable, de silicium et de titane, à des températures modérées comprises entre 350°C et 700°C. Ces films ont été soumis à diverses techniques d’analyse et de caractérisation (EDS, EMPA, ERDA-RBS, DRX, MEB, MET, FTIR, ATG, tests de corrosion). La composition des dépôts préparés par simple pyrolyse du précurseur transporté par de l’azote sec dépend de la température : à 350°C, le dépôt est constitué d’AlOOH amorphe ; au-dessus de 415°C, il est constitué d’alumine Al2O3, amorphe ou nanocristallin suivant la température ; entre 350°C et 415°C le dépôt se comporte comme un mélange des deux espèces. Par contre, en ajoutant de la vapeur d’eau dans la phase vapeur, on obtient uniquement des dépôts d’alumine Al2O3 amorphe ou nanocristalline, sur tout le domaine de température étudié. Des revêtements déposés en présence de vapeur d’eau, à différentes températures, sur des disques de Ti 6242, ont été testés comme couches protectrices contre la corrosion. On constate dans tous les cas une amélioration de la résistance à la corrosion, le revêtement déposé à 480°C se distinguant cependant très nettement des autres.
C. Vahlas, M.-M. Sovar, A. Gleizes, M. Raciulete, G. Boisier, N. Pébère, D. Samélor, MATERIAUX 2006 13-17 Novembre 2006 – Dijon, France

A1398 – Effect of the gas mixture composition on high-temperature behavior of magnetron sputtered Si–B–C–N coatings

The effect of the gas mixture composition on the high-temperature behavior of amorphous Si–B–C–N coatings was systematically investigated up to 1700 °C in a flowing air and inert gases (He and Ar). The Si–B–C–N coatings were deposited by reactive dc magnetron co-sputtering using a single B4C–Si target in two nitrogen–argon gas mixtures (50% N2+50% Ar or 25% N2+75% Ar). A fixed 75% Si fraction in the target erosion area, an rf induced negative substrate bias voltage of ?100 V, a substrate temperature of 350 °C and a total pressure of 0.5 Pa were held constant in depositions. The high-temperature behavior of the coatings, including their oxidation resistance in air and thermal stability in inert gases, was characterized by means of high-resolution thermogravimetry, differential scanning calorimetry, X-ray diffraction, Rutherford backscattering spectrometry and elastic recoil detection analysis. It was found that the Ar fraction in the gas mixture determines an important N/ (Si+B+C) concentration ratio in the coatings, and hence their hightemperature behavior. The coating prepared with a 50% Ar fraction exhibits extremely high oxidation resistance (?m=0) up to 1400 °C and very high oxidation resistance (?mb0.02 mg/cm2) up to 1600 °C in air, and extremely high thermal stability up to 1600 °C in inert gases. The stability of the coating prepared with a 75% Ar fraction is very high up to the onset (at about 1250 °C) of crystallization of its initial amorphous structure.
J. ?apek, S. H?eben, P. Zeman, J. Vl?ek, R. ?erstvý, J. Houška, Surface & Coatings Technology 203 (2008) 466–469

A1393 – Thermogravimetry-evolved gas analysis–mass spectrometry system for materials research

Thermal analysis is a widely used analytical technique for materials research. However, thermal analysis with simultaneous evolved gas analysis describes the thermal event more precisely and completely. Among various gas analytical techniques, mass spectrometry has many advantages. Hence, an ultra high vacuum (UHV) compatible mass spectrometry based evolved gas analysis (EGA–MS) system has been developed. This system consists of a measurement chamber housing a mass spectrometer, spinning rotor gauge and vacuum gauges coupled to a high vacuum, high temperature reaction chamber. A commercial thermogravimetric analyser (TGA: TG + DTA) is interfaced to it. Additional mass flow based gas/vapour delivery system and calibration gas inlets have been added to make it a versatile TGA–EGA–MS facility. This system which gives complete information on weight change, heat change, nature and content of evolved gases is being used for (i) temperature programmed decomposition (TPD), (ii) synthesis of nanocrystalline materials, (iii) gas–solid interactions and (iv) analysis of gas mixtures. The TPD of various inorganic oxyanion solids are studied and reaction intermediates/products are analysed off-line. The dynamic operating conditions are found to yield nanocrystalline products in many cases. This paper essentially describes design features involved in coupling the existing EGA–MS system to TGA, associated fluid handling systems, the system calibration procedures and results on temperature programmed decomposition. In addition, synthesis of a few nanocrystalline oxides by vacuum thermal decomposition, gas analysis and potential use of this facility as controlled atmosphere exposure facility for studying gas–solid interactions are also described.
M. Kamruddin, P. K. Ajikumar, S. Dash, A. K. Tyagi, Baldev Raj, Bull. Mater. Sci., Vol. 26, No. 4, June 2003, pp. 449–460

A1355 – Thermal analysis and microstructural characterization of ceramic green tapes prepared by aqueous tape casting

In this study, aqueous lead magnesium niobate (PMN) slurry formulations were developed for tape casting using a poly(acrylic acid) – poly(ethylene) oxide comb polymer as the dispersant, nonionic acrylic latex as the binder phase and hydroxypropylmethylcellulose as the wetting agent. Concentrated suspensions were cast onto a silicone-coated mylar film, and the effect of acrylic latex on deposition was investigated. Thermal analyses were performed to investigate the mass loss of the green tapes as a function of calcination temperature. Differential scanning calorimetric analyses were made under air and nitrogen atmospheres to investigate the binder distribution through the green tapes. Results showed that it is possible to prepare flexible, crack free PMN thick films using a proper slurry composition in the presence of acrylic latex binder, without using any plasticizer. Additionally, decomposing mechanisms of the acrylic based binder were essentially different in the two atmospheres
A. Sakar-Deliormanli, E. Celik and M. Polat, Journal of Thermal Analysis and Calorimetry, Vol. 94 (2008) 3, 663–667

A1354 – Influence of lime-containing additives on the thermal behaviour of ammonium nitrate

Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious disadvantages being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing substances mainly Estonian limestone and dolomite – as internal additives on thermal behaviour of AN. Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated on the mole ratio of AN/(CaO,MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C (10°C min–1) in a stream of dry air or N2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR). The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the decomposition of AN in air or in N2. At the thermal treatment of AN’s blends with CaCO3, MgCO3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism – depending on the origin and the content of additives, partially or completely, through the formation of Mg(NO3)2 and Ca(NO3)2.
T. Kaljuvee, E. Edro and R. Kuusik, Journal of Thermal Analysis and Calorimetry, Vol. 92 (2008) 1, 215–221

A1349 – Characterization of thin solid films containing yttrium formed by electrogeneration of base for high temperature corrosion applications

Mixed water-ethyl alcohol solutions of Y(NO3)3, 6H2O at 0.01 M were used for cathodic electrodeposition of Y(OH)3 thin films on Ni- 20 wt.% Cr-1.5 wt.% Si substrate. Y(OH)3, xH2O deposits were obtained using a conventional three electrode cell. Current density and duration of deposition were optimized in order to obtain thin (<1 µm), uniform and adherent films. These deposited films were further transformed by thermal treatment into Y2O3 coatings, expected to increase the high temperature oxidation resistance of the substrate. Thermal stability, microstructure and formed phase of as deposited films and thermally treated films were characterized by differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron and atomic force microscopies (SEM, AFM), inductively coupled plasmaoptical emission spectroscopy (ICP-OES) and X-ray diffraction.
J-M. Brossard, J. Balmain, J. Creus, G. Bonnet, Surface & Coatings Technology 185 (2004) 275-282

A1347 – Synthesis of zeolite beta in fluoride media under microwave irradiation

Zeolite beta has been successfully prepared at 150°C within 4 h by direct synthesis under microwave irradiation. Addition of seeds into the synthesis solution under microwave irradiation did not affect overall synthesis time of the material significantly, while addition of ammonium fluoride accelerated the crystallization of zeolite beta. In particular, microwave technique combined with fluoride species and seeding led to more rapid synthesis of crystalline zeolite beta. Upon microwave irradiation fluoride species and the microwave-activated water in the synthesis solution might be ascribed to shortening an induction period at the nucleation step, resulting in the rapid synthesis of the material.
D.S. Kim, J-S. Chang, J-S. Hwang, S-E. Park, J.M. Kim, Microporous and Mesoporous Materials 68 (2004) 77-82

A1346 – Synthesis of a silica monolith with textural pores and ordered mesopores

Silica monolith with textural pores and ordered mesopores was fabricated through a sol-gel process by using triblock polymer of F127 as pore directing reagent. In the reaction, F127 demonstrated its dual functions-phase separation inducing function and template function. The former resulted in co-continuous structure of silica skeletons and textural pores, while the latter led to the formation of ordered mesopores.
Z-G. Shi, Y-Q. Feng, L. Xu, S-L. Da, Y-Y. Ren, Microporous and Mesoporous Materials 68 (2004) 55-59

A1345 – Synthesis of AlPO4-31 from nonaqueous systems

The aluminophosphate molecular sieve AlPO4-31 has been synthesized from a nonaqueous system in the presence of hexamethyleneimine as templating agent and has been characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), FT-IR, differential thermal analysis (DTA) and thermogravimetric analysis (TG) and 27Al and 31P MAS NMR techniques.
N. Venkatathri, Materials Letters 58 (2003) 241-244

A1343 – Synthesis and characterization of (La1-xMx)2Mo2O9-d ; M=Ca2+, Sr2+ or Ba2+

The system (La(1-x)Cax)2Mo2O(9-d) was characterized in the region x=0.01
R. Subasri, D. Matusch, H. Näfe, F. Aldinger, Journal of the European Ceramic Society 24 (2004) 129-137

A1342 – Hydrothermal processing of nanocrystalline anatase films from tetraethylammonium hydroxide peptized titania sols

Nanocrystalline anatase films were obtained by hydrothermally treating dip-coated TiO2 gel films onto silicon substrates from tetraethylammonium hydroxide (TENOH) peptized titania aqueous sols diluted with different solvents (isoproponol, acetone and propanediol) at 240°C for 2 h. SEM, AFM and XRD analysis were used to characterize the microstructure and phase evolution of the films. The highest degree of homogeneity and good wettability towards the substrate could only be obtained with mixed solvents of acetone and isopropanol, yielding denser structure with homogeneously distributed fine grains among all the three solvents. A uniform distribution of fine grains of around 50 nm was obtained after hydrothermal treatment, while the film calcined at 500°C/2 h displayed larger grains of around 80 nm and were not so uniformly developed. All these results suggest that (a) TENOH peptized titania sol is a promising novel stock precursor for synthesizing TiO2 films; (b) hydrothermal technique is quite efficient in preparing titania nanocrystalline films compared with calcination method.
J. Yang, S. Mei, J.M.F. Ferreira, Journal of the European Ceramic Society 24 (2004) 335-339

A1340 – Disproportionation of stoichiometric LiMn2O4 on annealing in oxygen

The evolution of stoichiometric LiMn2O4 upon annealing under oxygen pressures in the range 0.2-5 atm at moderate temperature (450°C) was studied with a combination of thermogravimetry, X-ray and neutron diffraction. It is shown that such treatments result in a slight, but significant mass increase. Structural analyses show that the resulting spinel is a manganese-deficient spinel phase with lower cell parameter and higher manganese valence, and that the expelled manganese forms Mn2O3. The presence of this second phase, which was not identified in a recent study of oxygen annealing on this compound (Nakamura and Kajiyama, Solid State Ionics 133 (2000) 195), is compatible with the initial stoichiometry and does not require any oxygen vacancies in the initial LiMn2O4, as supposed earlier. The most likely formula of the resulting lithium-rich spinel with increased manganese valence is Li(Mn(2-e)e)O4 with e in the range 0.02-0.03 at 5 atm O2.
P. Strobel, G. Rousse, A. Ibarra-Palos, and C. Masquelier, Journal of Solid State Chemistry 177 (2004) 1-5

A1339 – Towards single step production of multi-layer inorganic hollow fibers

In this work we propose a generic synthesis route for the single step production of multi-layer inorganic hollow fibers, based on polymer wet spinning combined with a heat treatment. With this new method, membranes with a high surface area per unit volume ratio can be produced, while production time and costs are dramatically reduced. The proof-of-principle of the concept will be demonstrated with the production of double layer alpha-alumina hollow fibers. Although various problems were anticipated at the interface of the layers, the adhesion between the two layers is surprisingly good, both in the precursor and the sintered fiber. Produced fibers show an asymmetric structure with a porosity between 37 and 45%. The macrostructure of the sintered fiber is largely determined by the macrostructure of the precursor fiber, while differences in microstructure disappear during the heat treatment step. The proposed method is not limited to alpha-alumina membranes; in principle many ceramic or metallic powders may be used. This means that this method can open up the way for a new generation of membranes.
J. de Jong, N.E. Benes, G.H. Koops, M. Wessling., Journal of Membrane Science 239 (2004) 265-269

A1335 – Morphology and sintering behaviour of yttria stabilised zirconia (8-YSZ) powders synthesised by spray pyrolysis

This work is focused on the synthesis of nano-crystallised yttria stabilised zirconia (YSZ) powders by the spray pyrolysis method, the aim of the study being a better understanding of the influence of the spray pyrolysis parameters on the morphology of the produced powders. Spray pyrolysed powder consists of polycrystalline particles, which are spherical. Each particle consists of nanometric primary grains. The morphology of these polycrystalline particles was characterised by scanning electron microscopy (SEM), helium pycnometry, thermogravimetric analysis (TGA) and mass spectroscopy (MS), and the results are compared. Thus, particle size, particle size distribution and particle porosity were determined and correlated to the process parameters. Finally, by dilatometric measurements, sintering curves of pellets prepared from different sets of powders were analysed in regard of their morphologies. Two main conclusions could be deduced from these studies. Firstly, the process parameters influence both internal porosity and particle size distribution of the synthesised powders. Secondly, the morphologies of the spray pyrolysed nano-powders lead to particularly high sintering activities.