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5631 articles

A0712 – Solar sintering of cordierite-based ceramics at low temperatures

Solar furnaces allow materials processing at much higher heating and/or cooling rates compared with those in the conventional industrial and laboratory processes using electric furnaces. During the course of our recent works using solar furnace, we demonstrated usability of solar furnace for sintering-consolidation of oxide ceramics (alumina) and non-oxide ceramics (WC with Co additive) as well as for producing raw material powders including carbide and carbonitride of transition metals and silicon. Being encouraged by these earlier solar-consolidation experiment results obtained for ceramics with relatively simple composition, we decided to continue this line of solar-sintering experiments for other industrial ceramics with more complicated composition. In this work, two types of commercial ceramic powder mixtures, BL7 and RP7, supplied by Rauschert Portuguesa Lda, were subjected to sintering under concentrated solar beam at 950°C for 20min. No evidence of formation of cordierite (2MgO . 2Al2O3 . 5SiO2) phase was detected for the present solar sintered specimens whereas evidence of cordierite phase formation was detected for the RP7 powders heated to 950°C in a laboratory electric furnace. As such, the present results implied that, for the preparation of consolidated cordierite using solar furnace, control over the heating rate is of critical importance as well as selection of the starting materials and setting of the processing temperature.
F. Almeida Costa Oliveira, N. Shohoji, J. Cruz Fernandes, L. Guerra Rosa, Solar Energy 78 (2005) 351-361

A0715 – Bi17Yb7O36 and BiYbO3 crystal structures. Characterization of thulium and lutetium homologous compounds

Two new compounds Bi17Yb7O36 and BiYbO3 which were recently evidenced in the Bi2O3-Yb2O3 system, have been characterized and their structure determined from X-ray diffraction powder data using the Rietveld method in an orthorhombic and a triclinic lattice, respectively. The thulium and lutetium homologous compounds have been prepared for the first time. They are isostructural to the ytterbium homologous. The six compounds have been characterized versus temperature by DTA, X-ray thermodiffractometry, and they systematically show a transformation from their low temperature form, to a delta-Bi2O3-type phase, occurring on heating. For Bi17Ln7O36, the delta-type phase is obtained, directly with Ln = Lu (870°C) and Yb (855°C), and only after an intermediate biphasic orthorhombic-cubic mixture in the range 780-825°C for Ln = Tm. For BiLnO3, there is a large two-phased domain (delta-Bi2O3 + Ln2O3 related phases) from 955 to 1100°C for Lu, 970 to 1200°C for Yb and 980 to 1270°C for Tm. The lattice constants thermal expansion coefficients have been determined from the cell parameters evolutions versus temperature. The conductivity properties of the Bi17Ln7O36 series, which could be obtained as ceramic pellets after sintering in the stability range of their low-temperature forms, have been investigated.
M. Drache, P. Roussel, P. Conflant, J-P. Wignacourt, Solid State Sciences 7 (2005) 269-276

A0714 – Synthesis, characterization and catalytic properties of hexagonal mesoporous vanadium aluminophosphate molecular sieves

Novel vanadium containing hexagonal mesoporous aluminophosphate molecular sieve (VHMA) have been synthesized. XRD and TEM analysis confirm the phase purity of the synthesized samples. FT-IR analysis suggests the incorporation of V4+ in the aluminophosphate framework. ESR, UV-Vis spectroscopic techniques and cyclic voltammetric studies confirm the incorporation of vanadium and reveal its presence of tetrahedral and square pyramidal environments in the as-synthesized samples. Cyclic voltammetry reveals the presence of two redox couples in VHMA. This catalyst is found to be a good oxidation catalyst.
N. Venkatathri, R. Srivastava, Catalysis Communications 6 (2005) 177-183

A0716 – Thermal analysis (TG-DTA) and isotopic characterization (13C-15N) of humic acids from different origins

Thermal analyses (TG-DTA), elemental composition and isotope analyses (13C and 15N) were performed on humic acids (HA) from peats, leonardites and lignites, in order to investigate their structure and the changes taking place during the humification process. Thermal analyses showed structural differences between HA samples in relation to their coalification rank. In particular the lignite HA were characterized by a more stable chemical composition at high temperatures. The d13C and d15N values can provide information on the biogeochemical processes involved in HA formation. In particular, peat HA were linked to anoxic environments that enable plant residues to persist in their structure. In contrast, leonardite and lignite HA formation seems to be governed by different biogeochemical processes from those responsible for peat diagenesis. However, the isotopic analyses did not provide any distinction between leonardite and lignite HA. On the basis of the data presented in this study, it may be concluded that TG-DTA and isotope ratio measurements are powerful tools for investigating the formation pathway of humic substances from coals.
O. Francioso, D. Montecchio, P. Gioacchini, C. Ciavatta, Applied Geochemistry 20 (2005) 537-544

A0717 – Synthesis and characterization of zeogrid molecular sieves

Clear solution was prepared by hydrolyzing tetraethylorthosilicate (TEOS) in tetrapropylammonium (TPA) hydroxide and heated at 120°Cfor various times in order to generate half-nanoslabs, nanoslabs, tablets, intermediates and colloidal Silicalite- 1 crystals. These building units were precipitated by addition of cetyltrimethylammonium (CTMA) bromide. After evacuation of TPA and CTMA from the precipitates through calcination, microporous materials having substantial micropore volumes of 0.5-0.7 ml/g designated as Zeogrids were obtained. The micropores comprise ultra-micropores inside the zeolitic building units, and super-micropores between these building units. The ultra-micropores of Zeogrids render molecular sieving properties to these materials, which can be fine-tuned by adapting the size of the zeolitic building units
S.P.B. Kremer, C.E.A. Kirschhock, P.A. Jacobs, J.A. Martens, C. R. Chimie 8 (2005) 379-390

A0718 – Isothermal reduction kinetics at 900-1100°C of NiFe2O4 sintered at 1000-1200°C

Nickel ferrite is one of very important material, which is suitable for using in computer peripherals, telecommunications equipments, permanent magnets, electronic and microwave devices. Thus, the study of the behavior of NiFe2O4 in reducing atmosphere is very important. NiFe2O4 is prepared by mixing chemically pure powders of Fe2O3 and NiO in stoichiometric ratios then pressed at 250 kg/cm2 into cylindrical form of compacts before being fired at 1000, 1100 and 1200°C for 10 h. The characteristic of the prepared nickel ferrite have been studied using X-ray diffraction analysis technique, reflected light microscope and porosity measurements. The behavior of nickel ferrite in hydrogen atmosphere at 900-1100°C has been studied using thermogravimetric techniques. The reduction of NiFe2O4 is not found to proceed to completion at any firing or reduction temperature. The reduction proceeds via a topochemical mode. At firing temperatures 1000 and 1100°C, the rate is controlled initially by the combined gaseous diffusion interfacial chemical reaction mechanism while at the final stages, the interfacial chemical reaction is predominantly the rate-controlling mechanism. At 1200°C, initially the rate controlling is the interfacial chemical reaction mechanism while the solid-state diffusion is rate-controlling mechanisms at the final stages.
M.H. Khedr, J. Anal. Appl. Pyrolysis 73 (2005) 123-129

A0720 – AlPO-ERI, an aluminophosphate with the ERI framework topology: characterization and structure of the as-made and calcined rehydrated forms

An aluminophosphate with the ERI framework topology, further denoted AlPO-ERI, has been synthesized in the presence of N,N,N',N'-tetramethyl-1,6-hexanediamine and its structure was solved by single crystal X-ray diffraction. It crystallizes in the monoclinic space group P2(1) (No. 4) with a = 13.163(14) Å, b = 14.793(15) Å, c = 13.215(14) Å, b = 119.74(8)°. As compared to similar materials prepared with piperidine as template, extraframework hydroxyl groups are locally ordered in the structure. After calcination and rehydration, the aluminophosphate remains monoclinic and crystallizes in space group P2(1)/n (No. 14) with a = 13.283(17) Å, b = 14.910(14) Å, c = 22.76(3) Å and b = 90.19(10)°. Both the as made and calcined rehydrated forms of AlPO-ERI have been characterized by multidimensional solid state NMR. To cite this article: A. Tuel et al., C. R. Chimie 8 (2005).
A. Tuel, C. Lorentz, V. Gramlich, C. Baerlocher, C. R. Chimie 8 (2005) 531-540

A0719 – Synthesis and electrochemical performance of LiNi0.5Mn1.5O4 spinel compound

Spinel compound LiNi0.5Mn1.5O4 was synthesized by a chemical wet method. Mn(NO3)2, Ni(NO3)2.6H2O, NH4HCO3 and LiOH.H2O were used as the starting materials. At first, Mn(NO3)2 and Ni(NO3)2.6H2O reacted with NH4HCO3 to produce a precursor, then the precursor reacted with LiOH.H2O to synthesize product LiNi0.5Mn1.5O4. The product showed a single spinel phase under appropriate calcination conditions, and exhibited a high voltage plateau at about 4.6-4.8V in the charge/discharge process. The LiNi0.5Mn1.5O4 had a discharge specific capacity of 118 mAh/g at about 4.6V and 126 mAh/g in total in the first cycle at a discharge current density of 2 mA/cm2. After 50 cycles, the total discharge capacity was above 118 mAh/g.
G.Q. Liu, Y.J. Wang, Qilu, W. Li, Chenhui, Electrochimica Acta 50 (2005) 1965-1968

A0722 – Crystallization, stability and possible application of the molecular sieve cloverite

Experiences on crystallization, stability and application fields of the molecular sieve cloverite are summarized, with focus on the achievable stability improvements by silanation of the surface to shield the framework from bond-rupture by interacting small polar molecules like water and ammonia. Benefits of applying microwave-assisted syntheses routines are outlined, and the morphology of crystallization products as revealed by SEM images is discussed.
R. Fricke, H-L. Zubowa, M. Richter, H. Kosslick, C. R. Chimie 8 (2005) 549-559

A0721 – Synthesis and characterization of two aluminophosphates templated by N-methyl-1,3-diaminopropane

Two crystalline aluminophosphates have been synthesized under hydrothermal conditions using N-methyl-1,3-diaminopropane (MeDAP) as structure-directing molecule. The first one, denoted MDAP-1 is observed as an intermediate phase during the crystallization of the final product MDAP-2. The structure of MDAP-1, a 2D-layered compound with the empirical formula (C4H14N2)1.5[Al3P4O16] was refined using powder X-ray diffraction data. It crystallizes in the monoclinic space group P21/c (No. 14) with a = 14.080(10)Å , b = 8.4763(1)Å , c = 18.9954(1)Å , beta = 100.95(5)° and Z = 4: Inorganic sheets contain a novel 4 6 net, constructed from capped 6-membered rings. The sheets are held together by partially disordered, doubly protonated MeDAP molecules. Single crystal analysis showed that MDAP-2 is isostructural with AlPO4-21 and crystallizes in the monoclinic space group P21/n (No. 14) with a = 8.488(6)Å , b = 17.72(2)Å , c = 9.024(6)Å , beta = 106.96(5)° and Z = 4: MDAP-2 differs from AlPO4-21 by the presence of an octahedrally coordinated aluminum in the framework.
A. Tuel, J-L. Jorda, V. Gramlich, C. Baerlocher, Journal of Solid State Chemistry 178 (2005) 782-791

A0724 – Iron containing mesoporous solids: preparation, characterisation, and surface properties

This review article is devoted to our work in the area of MCM-41 type materials modified with iron species. Three types of matrices have been applied: silicate MCM-41, aluminosilicate AlMCM-41, and niobosilicate NbMCM-41. Iron was introduced by various methods: during the synthesis, immobilisation of ferroceneacetic acid (FAA), chemical vapour deposition (CVD), impregnation, cation exchange (IE) and template cation exchange (TIE). Three fundamental features of the prepared materials have been considered: (i) structure, (ii) iron state (coordination, oxidation level, reducibility), and (iii) catalytic activity. The latter was tested in isopropanol decomposition, oxidation of methanol, decomposition of NO, selective reduction of NO with propene, and hydroxylation/polymerisation of phenol.
P. Decyk, M. Trejda, M. Ziolek, C. R. Chimie 8 (2005) 635-654

A0723 – Characterization of pure and substituted 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3

Ferroelectric single crystals Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) are promising full materials for non-resonant or large bandwidth transducers due to the large values of their piezoelectric properties (dij, kij) and their low mechanical quality factor (Qij). The growth and characterization of pure and Mn-doped PZN-PT single crystals are reported in this paper. Crystals of pure and 1mol% Mn-doped PZN-4.5PT were grown by a Flux technique. The typical single crystals obtained are brown yellow for the pure PZN-4.5PT and black for the Mn-doped PZN-4.5PT. The crystal lattice parameters of doped PZN-PT crystals are slightly increased compared with the pure one. The room temperature dielectric permittivity along the /0 01S direction is about 3500, which is lower than that of the pure PZN-4.5PT. The Curie temperature Tc of the doped crystal is about 178°C (which is higher than that of the pure crystal (166°C)), while the ferroelectric phase transition temperature is 124°C (lower than that of the pure crystal (130°C)). The remnant polarization and coercive field of /0 01S oriented doped crystal measured at 1 kHz are around 31 mC/cm2 and 4.46 kV/ cm, respectively, 27 mC/cm2 and 3.32 kV/cm for the pure crystal. Piezoelectric charge coefficients of the /00 1S oriented doped crystal are about 1560 pC/N and 542 pC/N, respectively, for the longitudinal and the transverse modes. The mechanical quality factor Qm is around 400 for the doped single crystals at room temperature, larger than that of the pure single crystals. The valence state of the manganese dopant was determined by electron spin resonance indicating that the manganese is in majority in its lowest valence 2+. Physicochemical properties (such melting point, dilatation parameter and contents) were also determined. The variation of the piezoelectric coefficient d31 versus temperature and the d33 versus uniaxial stress shows that these coefficients are more stable for the doped crystals than for the pure one.
D. Kobor, L. Lebrun, G. Sébald, D. Guyomar, Journal of Crystal Growth 275 (2005) 580-588

A0726 – Metal organic frameworks based on Cu2+ and benzene-1,3,5-tricarboxylate as host for SO2 trapping agents

Metal organic framework materials with Cu2+ as central cation and benzene-1,3,5-tricarboxylate (BTC) as linker were prepared via hydrothermal synthesis and impregnated with barium salts (chloride, nitrate, acetate) to explore the role of the Ba2+ counter ion on the SO2 uptake. The impregnation of the metal organic framework materials with barium salts led to a decrease of pore volume through the (intra pore) formation of small Ba salt crystals. The structure of the Cu-BTC material was preserved after the impregnation with acetate and nitrate, but partially destroyed during impregnation with chloride. The complete loss of the BTC structure occurred through thermal decomposition at temperatures around 573 K. The sample impregnated with BaCl2 showed a higher fraction of Cu2+ species compared to the other Ba/Cu-BTC samples. The SO2 uptake capacity of the Ba/Cu- BTC(Cl-) sample was the highest at temperatures below 673 K among all materials prepared and even higher compared to BaCO3/Al2O3/Pt based material. The comparison of the theoretical uptake (based on the stoichiometric formation of BaSO4) with the maximum SOx uptake achieved on the Ba/Cu-BTC samples clearly points out that a fraction of the SOx is stored on the Cu species being part of the metal organic framework structure.With increasing temperature the framework is (partially) decomposed and highly dispersed Cu species are released, which act as additional SOx storage sites in the high temperature region.
H. Dathe, E. Peringer, V. Roberts, A. Jentys, J.A. Lercher, C. R. Chimie 8 (2005) 753-763

A0725 – Sr2/3Y1/3CoO8/3+d: Transition from insulating antiferromagnet to metallic ferromagnet by control of the oxygen content

Magnetic and electronic properties of the oxygen deficient ordered perovskite, Sr2/3Y1/3CoO8/3+d, have been studied for two different oxygen contents corresponding to d = 0,00 and 0,04 in the chemical formula. For the former, at low temperature, the background state is antiferromagnetic insulating (TN = 290K; p10 K = 4 x 10^5 ohm.cm) as expected from the presence of trivalent cobalt in the high spin-state. Remarkably, the more oxidized compound with a cobalt oxidation state of E3.08 is a ferromagnetic half-metal with TC = 225K and p10 K = 2 x 10^3 ohm.cm. Consistently, upon application of an external magnetic field, the spinscattering reduction in the TC vicinity is responsible for a weak negative magnetoresistance. These dramatic changes of the physical properties for such a slight increase of the cobalt oxidation state are interpreted as a result of the structural disordering created by the extra oxygens. The thermoelectric power measurements, showing a sign change of the Seebeck coefficient as the oxygen content increases, indicate that electrons moving in a metallic eg band dominate the transport properties of the ferromagnetic and metallic compound. This suggests the existence of an orbital ordering in the pristine compound, related to an ordered array of CoO4 tetrahedra, which can be collapsed by the presence of these extra oxygen anions.
A. Maignan , S. Hébert, V. Caignaert, V. Pralong, D. Pelloquin, Journal of Solid State Chemistry 178 (2005) 868-873

A0727 – p-Type electron transport in La(1-x)SrxFeO(3-d) at high temperatures

Electrical conductivity, thermopower and oxygen content were measured for La(1-x)SrxFeO3-d (x = 0.2, 0.5, 0.9) within the oxygen partial pressure range 10^(-4) - 0.5 atm and at temperatures 750-950°C. The dominating charge carriers under these experimental conditions are electron holes. The results of oxygen nonstoichiometry measurements are used to estimate the concentration of holes and to analyze data on conductivity and thermopower. The changes in thermopower are described by the model assuming that the number of sites accessible for migration of holes is independent on oxygen content. The mobility of electron holes is calculated, and it is found to be virtually independent on temperature in the compositions with x<0.5 while compositions with x>0.5 exhibit thermally activated mobility and mobility values about 0.1 cm2 V-1 s-1 or smaller. It is suggested that the main contribution to the composition dependent variations in electron hole mobility are associated with Coulomb interactions at small x's, whereas at high degrees of doping the mobility of holes is most strongly affected by the increasing amount of oxygen vacancies.
M.V. Patrakeev, I.A. Leonidov, V.L. Kozhevnikov, K.R. Poeppelmeier, Journal of Solid State Chemistry 178 (2005) 921-927

A0728 – NEXAFS and X-ray scattering study of structure changes after post-annealing treatments of aligned MWNTs

The control of the crystallization degree is an important issue for carbon nanotube applications. In this context, we present the evolution of the structure after post-annealing treatment of multiwalled carbon nanotubes (MWNT), obtained by the aerosol pyrolysis process, involving liquid aerosols containing both hydrocarbon source and the metal catalyst precursor. The alignment and the degree of crystallinity of the raw and annealed carbon nanotubes have been quantified by X-ray diffraction measurements also used to analyze the metallic phases inside the nanotubes. The Near-Edge X-ray Absorption Fine Structure (NEXAFS) studies were performed at the C K-edge in order to follow the evolution of the electronic structure with the local structure and the degree of crystallinity of the nanotubes. We confirm that this chemical vapour deposition synthesis method enables to produce well-aligned multiwalled carbon nanotubes. The effect of post-annealing temperature both on local ordering and graphitization degree of nanotube walls are described. The results are compared to the previous observations of individual nanotubes by HRTEM concerning the structural changes occurring during annealing treatments.
B. Bouchet-Fabre, M. Pinault, V. Pichot, P. Launois, M. Mayne-L'Hermite, Ph. Parent, K. Laffon, D. Durand, C. Reynaud, Diamond & Related Materials 14 (2005) 881-886

A0729 – Preparation of VO2 nanowires and their electric characterization

Large-scale VO2 nanowires have been synthesized by two-step method. First, we have been obtained (NH4)0.5V2O5 nanowire precursors by hydrothermal treatment of ammonium metavanadate solution at 170°C. Secondly, the precursors have been sealed in quartz tube in vacuum and annealed to form VO2 nanowires at 570°C. Scanning electron microscope and transmission electron microscope analysis show that the nanowires have selfassembling nanostructure with the diameter of about 80-200 nm, length up to125 mm. Electrical transport measurements show that it is semiconductor with conduction activate energy of 0.128 eV. A metal-semiconductor transition can be observed around 341 K.
X. Wu, Y. Tao, L. Dong, Z. Wang, Z. Hu, Materials Research Bulletin 40 (2005) 315-321

A0733 – Du choix du précurseur pour la synthèse de poudres d’oxydes La1-xSrxMnO3

Différentes poudres précurseurs (carbonates, oxalates, citrates) de manganites de lanthane dopés au strontium ont été préparées par chimie douce. Après calcination, ces précurseurs conduisent aux oxydes mixtes à structure perovskite LaxSr1-xMnO3, dont la morphologie et la taille des particules dépendent à la fois de celles du précurseur et des conditions du traitement thermique. Des analyses thermiques de la décomposition des précurseurs montrent que seuls les citrates sont des précurseurs mixtes, ce qui permet d'obtenir les oxydes à structure perovskite dès 600°C, au lieu de 850°C pour les oxalates et 900°C pour les carbonates. De plus, seule la méthode des citrates conduit à des poudres d'oxydes dont la morphologie, la surface spécifique, la non-stoechiométrie peuvent être modulée dans une large gamme.
S. Guillemet-Fritsch, P. Alphonse, C. Calmet, H. Coradin, P. Tailhades, A. Rousset, C. R. Chimie 8 (2005) 219-227

A0732 – Phase equilibria in the system CePO4-K3PO4-K4P2O7

The phase diagram with liquids isotherms and isothermal section at room temperature of the system CePO4-K3PO4-K4P2O7 has been determined by thermal analysis, K4P2O7 powder X-ray diffraction and IR spectroscopy. The system contains two double phosphates: K3Ce(PO4)2 and K4Ce2P4O15. The first one melts incongruently at 1500°C. The other exists only in solid state (below 880°C). Two systems: CePO4-K4P2O7 and K3Ce(PO4)2-K4P2O7, which are binary only in the subsolidus region, have been found.
I. Szczygiel, Solid State Sciences 7 (2005) 189-194

A0730 – A transient thermogravimetric study on the oxygen permeation at high temperature of the superconducting material YBa2Cu3O7-d

The solid-gas phase oxygen ions exchange of the superconducting material YBa2Cu3O7-d (YBCO) powder at high temperature subject to an instantaneous change of surrounding gas between pure oxygen and nitrogen was studied by a transient thermogravimetric analysis (TGA) method. The dependence of equilibrium oxygen vacancy of YBCO sample on surrounding partial oxygen pressure at temperature region 500-800°C was measured by a homemade static oxygen absorption instrument. A rapid weight gain in the oxygen absorption period and a slow weight loss in the oxygen desorption period were observed in the transient experiment. The surface reaction rate constants both for the oxygen absorption and desorption periods were calculated by considering the surface reaction as the rate-limiting step. The result shows that rate constant for the oxygen desorption period is much smaller than that of the oxygen absorption period.
J. Hu, X. Hu, H. Hao, L. Guo, H. Song, D. Yang, Solid State Ionics 176 (2005) 487-494

A0734 – Spectroscopic characterization of alkaline earth uranyl carbonates

A series of alkaline uranyl carbonates, M[UO2(CO3)3] nH2O (M=Mg2, Ca2, Sr2, Ba2, Na2Ca, and CaMg) was synthesized and characterized by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after nitric acid digestion, X-ray powder diffraction (XRD), and thermal analysis (TGA/DTA). The molecular structure of these compounds was characterized by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). Crystalline Ba2[UO2(CO3)3] 6H2O was obtained for the first time. The EXAFS analysis showed that this compound consists of (UO2)(CO3)3 clusters similar to the other alkaline earth uranyl carbonates. The average U-Ba distance is 3.9070.02A ? .Fluorescence wavelengths and life times were measured using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The U-O bond distances determined by EXAFS, TRLFS, XPS, and Raman spectroscopy agree within the experimental uncertainties. The spectroscopic signatures observed could be useful for identifying uranyl carbonate species adsorbed on mineral surfaces.
S. Amayri, T. Reich, T. Arnold, G. Geipel, G. Bernhard, Journal of Solid State Chemistry 178 (2005) 567-577

A0735 – Investigation of the reactivity of AlCl3 and CoCl2 toward molten alkali-metal nitrates in order to synthesize CoAl2O4

Cobalt aluminate CoAl2O4 powder, constituted of nano-sized crystallites, is prepared, involving the reactivity of AlCl3 and CoCl2 with molten alkali-metal nitrates. The reaction at 450°C for 2 h leads to a mixture of spinel oxide Co3O4 and amorphous g-Al2O3. It is transformed into the spinel oxide CoAl2O4 by heating at 1000°C. The powders are mainly characterized by XRD, FTIR, ICP, electron microscopy and diffraction, X-EDS and diffuse reflection. Their properties are compared to those of powders obtained by solid state reactions of a mechanical mixture of chlorides or oxides submitted to the same thermal treatment.
N. Ouahdi, S. Guillemet, J.J. Demai, B. Durand, L. Er Rakho, R. Moussa, A. Samdi, Materials Letters 59 (2005) 334- 340

A0738 – Kinetic studies of oxidation of y-AlON-TiN composites

The present article deals with the investigation of the oxidation kinetics of y-aluminum oxynitride-Titanium Nitride composites (AlON-TiN) in the temperature range of 1100-1300°C by thermogravimetry. Oxidation experiments with AlON-TiN composite plates have been carried out in air both in isothermal and nonisothermal modes. The results showed that the rate of oxidation was negligible below 1000°C, and showed an increase with increasing temperature at higher temperature. Both isothermal studies as well as experiments with ramped temperature clearly indicated that the mechanism of the reaction changes around 1400°C. In the nonisothermal mode, the oxidation curve showed an increased reaction rate in this temperature range. Oxidation of AlON-TiN composite results in y-Al2O3 and TiO2 at a low temperature and Al2TiO5 at higher temperature. The buildup of the product layer leads to diffusion controlled kinetics. In the nonisothermal experiments, the phase transformation from Al2O3 and TiO2, to a Al2TiO5 product layer at higher temperature would lead to crack formation, thereby leading to direct chemical reaction. From the experiments for the isothermal oxidation of AlON-TiN composite plates, the overall reactions are separated into three stages: chemistry reaction-controlling stage; chemical reaction- and diffusion-mixed-controlled stage; diffusion-controlled stage. The apparent activation energy for the experiments were calculated to be 10.109, 2.19 and 5.614 kJ mol-1, respectively, in the above three stages.
Z. Zhang, X. Wang, W. Li, Journal of Alloys and Compounds 387 (2005) 74-81

A0737 – Bulk oxidation state of the different cationic elements in the MoVTe(Sb)NbO catalysts for oxidation or ammoxidation of propane

Different spectroscopic techniques like XANES, ESR, XPS and Mo¨ssbauer spectroscopy have been used to determine the oxidation state of the various cations in the M1 and M2 phases of the MoVTe(Sb)NbO catalysts used for the oxidation or ammoxidation of propane. It was observed that the tellurium or antimonyM1 orM2 phases contained mainly TeIV, and NbV. Molybdenum, vanadium and antimony were shown to be present as MoVI and MoV, VV and VIV and SbV and SbIII. The M1 phase which is responsible for the high efficiency of catalysts, corresponds to the total stoichiometry (AO)2 x(A2O)xM20O56 with A = Sb or Te, M = Mo, V and Nb and 0 x 1. It has a structure with hexagonal channels occupied by the A cations and oxides. This channel may contain an excess of oxygen which constitutes a reservoir for the catalysts and which likely plays a role in the reoxidation of the catalytic sites. The balance of the charges introduced by these oxides anions was achieved by the partial oxidation of SbIII to SbV in M1(Sb) and by the oxidation of MoV to MoVI in M1(Te), Te remaining always TeIV as shown from Mo¨ssbauer spectroscopy data. The characterization of the solids after catalytic test showed very few changes in the solids structures and compositions. The study allowed concluding that the lone pair elements does not have only a role as constituents of the surface catalytic sites but also as bulk components to store oxygen in the hexagonal channels and contributes to its rapid diffusion to the surface.
M. Baca, J-M.M. Millet, Applied Catalysis A: General 279 (2005) 67-77

A0736 – Mixed alkali effect in Li and Na aluminophosphate glasses: influence of the cation environment

This paper deals with the variation of the mixed alkali effect (MAE) in Li and Na aluminophosphate glasses. The general system investigated is: 0.46 [xNa2O(1 x)Li2O], 0.54 [ yAl2O3(1 y)P2O5], with x varying between 0 and 1 to probe the MAE, and y between 0 and 0.08 to modify the cation environment and to try to understand how the amorphous host affects the ionic motions. We show that the dc conductivity minimum characteristic of the MAE effect decreases and almost disappears as Al2O3 is added to mixed phosphate glasses. On another hand, the dc conductivity of the single alkali glasses is almost not affected by Al2O3 addition. Dielectric relaxation characteristics also change with the Al2O3 concentration in mixed glasses and not in single ones. On another hand, the mixed alkali peak measured using mechanical relaxation appears to be almost not affected by the presence of Al2O3. This decoupling between the mechanical and dielectric relaxation processes appears to Tthrough into questionr the proposal that the mechanical relaxation in mixed alkali glasses accounts for sites reconfiguration to adapt to the different cations.
A. Faivre, D. Viviani, J. Phalippou, Solid State Ionics 176 (2005) 325-332

A0740 – The effect of varying synthesis conditions on zinc chromium hydrotalcite: a spectroscopic study

Zn/Cr hydrotalcites were synthesised by coprecipitation, with varying pH values and divalent/trivalent metal ion ratio. Depending on the pH conditions, two 3R rhombohedral varieties were synthesised with different layer spacings of 7.8 and 8.9 Å, at room temperature. More carbonate was incorporated in the interlayer of samples prepared at low pH values, increasing the interlayer distance and the unit cell. Preparation under acidic conditions lead to a more crystalline, pure and thermally stable compound. Spectroscopy was used to determine the effect of varying the ratio of divalent/trivalent metal ion ratio. It was shown that although ratios >2 yield crystalline compounds a ratio of 3 was preferred for both phases.
J.T. Kloprogge, L. Hickey, R.L. Frost, Materials Chemistry and Physics 89 (2005) 99-109

A0739 – Structure and thermal behavior of nanocrystalline boehmite

First, the structural features of nanocrystalline boehmite synthesized by hydrolysis of aluminum sec-butoxide according to the Yoldas method are reported. The nanosized boehmite consists of rectangular platelets averaging 8 by 9 nm and 2-3 nm in thickness which contain a large excess of water. Dehydration by heating under vacuum induced an increase in the specific surface area, down to a minimum water content (-0.2 H2O per Al2O3); values up to 470m2/g can be reached. However this enlargement of specific surface area only results from water loss, the surface area remaining constant. The particle morphology, the excess of water, as well as the specific surface area, depend on the amount of acid used for the peptization during the synthesis. Second, a comprehensive investigation of the dehydration kinetics is presented. The simulations of the non-isothermal experiments at constant heating rates show that thermally stimulated transformation of nanocrystalline boehmite into alumina can be accurately modeled by a 4-reaction mechanism involving: (I) the loss of physisorbed water, (II) the loss of chemisorbed water, (III) the conversion of boehmite into transition alumina, (IV) the dehydration of transition alumina (loss of residual hydroxyl groups). The activation energy of each step is found to be very similar for experiments done in various conditions (heating rate, atmosphere, kind of sample,. . .).
P. Alphonse, M. Courty, Thermochimica Acta 425 (2005) 75-89

A0741 – Oxidation of o-xylene on mesoporous Ti-phosphate-supported Vox catalysts and promoter effect of K+ on selectivity

The selective oxidation of o-xylene on catalysts based on mesoporous titanium phosphate-supported vanadium oxide has been studied. The catalysts were characterized by different physico-chemical techniques (XRD, XPS, N2 isotherms, TPD of chemisorbed NH3 and Raman spectroscopy). The conversion and yield to phthalic anhydride increased with vanadium oxide loading up to one theoretical monolayer. Beyond this point, no substantial improvement was achieved. Moreover, a significant improvement in the yield of phthalic anhydride, coinciding with a decrease in the formation of carbon oxides, was observed when potassium was incorporated to the vanadium catalysts. The enhancement of the phthalic anhydride yield was correlated with the neutralization of the stronger surface acid centers by the K+ ions, providing evidence for the hypothesis that stronger acid sites are involved in the formation of total oxidation products (carbon oxides).
J. Jiménez-Jiménez, J. Mérida-Robles, E. Rodriguez-Castellon, A. Jiménez-Lopez, M. Lopez Granados, S. del Val, I. Melian Cabrera, J.L.G. Fierro, Catalysis Today 99 (2005) 179-186

A0743 – Oxidation of magnetite concentrate powders during storage and drying

Oxidation of magnetite pellet concentrates (from LKAB, Sweden) during drying and storage was studied using thermogravimetric analysis (TGA). The Fe2+content of a standard LKAB pellet feed decreased by 0.2% during heat treatment at 105°C for 2 days. The results indicate that magnetite concentrates of pelletizing fineness already start to oxidize to g-hematite during drying at 105°C, although 105°C is recommended by ISO 7764 and ISO 3087 and given as the maximum allowable drying temperature in ISO 3082. The importance of drying time for the amount of magnetite oxidized should also be recognized, but is not mentioned in the ISO standards. The sensitivity of magnetite particles for oxidation during drying could not be predicted by measuring the BET surface area. A simple isothermal TGA run gives exact experimental data and is recommended as a standard procedure before choosing the drying temperature for magnetite concentrate samples. Oxidation during storage at room temperature was observed as well. The Fe2+content in a standard Luossavaara- Kiirunavaara (LKAB) pellet feed decreased by 0.3% Fe2+during 4 years of storage at room temperature. Oxidation during storage was completely hindered when the samples were stored in a freezer at 50°C. Therefore, freezer storage is recommended for all magnetite reference materials. These materials are used over several years and are especially susceptible to oxidation because they are usually finely ground and high in Fe2+content. The results also show that if the magnetite sample has partly oxidized to g-hematite, the oxidation curve obtained by TGA will overestimate the Fe2+content of the sample, if background correction is necessary.
S.P.E. Forsmo, Int. J. Miner. Process. 75 (2005) 135- 144

A0742 – Crystallographic changes and thermal properties of lanthanum-strontium ferromanganites between RT and 700°C

X-ray powder diffraction was used to determine the crystallographic changes between room temperature (RT) and 700°C of the (La0.8Sr0.2)(Mn1 yFey)O3Fd perovskites with y=0.2, 0.5, 0.8, 1 which can be considered as possible cathode materials for the ITSOFCs. For y=0.2, the rhombohedral symmetry was preserved in the whole temperature range. For y=1, a transition from orthorhombic to rhombohedral symmetry occurred at 290°C. The compounds with y=0.5 and 0.8 were found to be diphasic at RT by combination of both rhombohedral and orthorhombic symmetries. They became only rhombohedral at 80 and 160°C, respectively. This reversible transition is discussed in terms of iron concentration, vacancy diffusion and oxidation state. These results were corroborated by a dilatometric study. The thermal expansion coefficients of these materials show a good compatibility with YSZ, the usual yttria-stabilized zirconia electrolyte.
M. Petitjean, G. Caboche, L-C. Dufour, Solid State Ionics 176 (2005) 9 -16

A0745 – Mechanistic and kinetic studies on glyoxal oxidation with Bi- and Pb-promoted Pd/C catalysts

Bimetallic Pd-M/C catalysts (M = Bi, Pb) for the selective oxidation of glyoxal into glyoxalic acid were prepared either from inorganic salts or from acetate-type precursors. The bimetallic catalysts were found to be very active, confirming the promoting ability of both bismuth and lead in this reaction. The magnitude of their effect in terms of activity and selectivity was similar, and dependent on the preparation method and on the composition (optimum for ratios Pd:M = 1). The heavy elements could play their promoter role when introduced in solution in combination with a monometallic Pd/C catalyst. A kinetic treatment of the complex reaction scheme was carried out, and the rate constants for each step were determined. This showed that the reaction proceeds through a real heterogeneous mechanism involving the catalyst for the oxidation of glyoxal into glyoxalic acid and then, in a second step, into oxalic acid. The direct formation of oxalic acid from glyoxal could be neglected, and the formation of glycolic acid was confirmed to depend only on the pH. The absence of deactivation with our catalysts was also demonstrated. Correlations between the rate constants and some surface characteristics of the promoted catalysts were evidenced.
F. Alardin, H. Wullens, S. Hermans, M. Devillers, Journal of Molecular Catalysis A: Chemical 225 (2005) 79-89

A0744 – Influence of spectator ions on the reactivity of divalent metal salts in molten alkali metal nitrates. Morphology of the resulting metal oxides

This work focuses on the investigation of the reaction of alkali metal nitrates (LiNO3, NaNO3 and KNO3) with divalent metal salts (Cu2+, Ni2+ and Zn2+). Thermogravimetric analysis (TGA) was employed to study the kinetics and mechanisms of the above reactions, which led to the formation of the corresponding metal oxides. The reaction temperature was found to depend not only on the alkali metal but also on the metal salt (MCl2 or M(NO3)2) involved in the reaction. SEM observations show that the spectator ions present in the reacting medium have varying degrees of influence on the morphology of the powder; the growth directions, sizes and the homogeneity of their distribution, are modified. KNO3 generates the most significant differences compared to LiNO3 and NaNO3.
P. Marote, C. Matei, C. Sigalac, J.P. Deloume, Materials Research Bulletin 40 (2005) 1-11

A0747 – Effect of Zn doping on crystal growth and structure of the pseudo-ladder compound CaCu2O3

Large single crystals of Ca(Cu1-xZnx)2O3 (x = 0; 0.035, 0.07, 0.14) have been grown by the traveling solvent floating zone (TSFZ) method. Appropriate growth atmosphere (5 bar oxygen) and CuO-poor starting composition to form solvent are found to be crucially important for successful crystal growth. Lower Zn content (x = 0:035; 0.07) promotes the phase formation and stability of the melt zone during the growth. Grown crystals were characterized by polarized optical microscopy, energy-dispersive analysis of X-rays (EDAX), thermogravimetry-differential thermal analysis (TGDTA), Laue back-scattering photography, and powder X-ray diffraction (XRD) methods.
C. Sekar, G. Krabbes, A. Teresiak, Journal of Crystal Growth 273 (2005) 403-411

A0746 – Retained molten salt electrolytes in thermal batteries

In high temperature electrical generators such as thermal batteries, the molten salt electrolyte needs to be retained by a binder, e.g. MgO.We have pointed out that the magnesia volume fraction was a more accurate parameter than the usually used weight fraction. Moreover, based on our technique measurements, we defined a magnesia volume fraction range (27-30 vol.%) where the electrolyte retention could be considered as efficient whatever its nature. And finally, we proposed a microstructure description of the retained electrolyte.
P. Masset, S. Schoeffert, J-Y. Poinso, J-C. Poignetc, Journal of Power Sources 139 (2005) 356-365

A0749 – The beneficial effect of water vapour on the oxidation at 600 and 700°C of a MoSi2-based composite

The oxidation characteristics of a MoSi2-based composite in O2 and O2 + 10% H2O at 600 and 700°C were investigated. The effects of temperature and water vapour on oxidation were examined. The oxidation kinetics were studied using a thermobalance and furnace exposure, while the morphologies and compositions of the oxides were examined using XRD, ESEM/EDX, and SEM/EDX.We propose that oxidation proceeds by the initial formation of MoO3 crystals and amorphous SiO2 on the surface. The MoO3 is then evaporated; as volatile (MoO3)3 species in O2 and additional MoO2(OH)2 species in O2 + 10% H2O, which results in a porous, Mo-depleted oxide. However, the pores in the Mo-depleted SiO2 scale heal, and a protective crystalline scale is established eventually. The vapour pressures of the abovementioned volatile species increase with temperature and/or water vapour content in the atmosphere, which leads to accelerated Mo depletion from the oxide scale. A shorter time elapses before the oxide scale is transformed into the relatively Mo-free protective SiO2 scale, which results in less oxide being formed. Thus, the formed scale becomes thinner in O2 + 10% H2O than in O2. Thereby the Mo removal is beneficial when water vapour is added to the exposure atmosphere.
K. Hansson, J.E. Tang, M. Halvarsson, R. Pompe, M. Sundberg, J.-E. Svensson, Journal of the European Ceramic Society 25 (2005) 1-11

A0748 – Study on the pyrolysis of wood-derived rayon fiber by thermogravimetry-mass spectrometry

The thermal pyrolysis of wood-derived rayon fiber has been studied from ambient temperature up to 800°C by thermogravimetry-mass spectrometry (TG-MS) analysis in an inert environment. Following an initial plateau region, the wood-derived rayon fiber rapidly decomposes in a narrow temperature range of 300-350°C. After this sharp weight loss, there is a gradual but constant weight loss up to 800°C. The values of kinetic parameters have been determined by using two dynamic thermogravimetric curves (TG and DTG). The data show that kinetics of wood-derived rayon fiber is similar to that of other cellulosic materials thermal degradation. Gases and tarry volatile products formed from the pyrolysis of wood-derived rayon fiber are monitored by MS. Water (m/z 18) is the predominant ion observed, followed by CO (m/z 28), CO2 (m/z 44) and CH4 (m/z 16). The MS signals show that the tarry volatiles are composed of varieties of compounds. The formation reactions of primary products from the pyrolysis are discussed in detail in the present paper.
Q. Liu, C. Lv, Y. Yang, F. He, L. Ling, Journal of Molecular Structure 733 (2005) 193-202

A0750 – Synthesis, crystal structure and magnetic properties of the spin ladder compounds La2(Cu1 xZnx)2O5 and La8(Cu1 xZnx)7O19

The influence of Zn-doping on the crystal structure and magnetic properties of the spin ladder compounds La2Cu2O5 (4-leg) and La8Cu7O19 (5-leg) have been investigated. The La2(Cu(1-x)Znx)2O5 and La8(Cu(1-x)Znx)7O19 solid solutions were obtained as single phases with x = 0-0,1 via the solid-state reaction method in the temperature range between 1005-1010°C and 1015-1030°C in oxygen and air atmospheres, respectively. The lattice parameters a and c of the monoclinic crystal structures as well as the unit cell volume V increase with increasing x, while b and b decrease for both series. The magnetic susceptibilities w of both series show a very similar behavior on temperature as well as on Zn-doping, which is supposed to be due to the similar Cu-O coordination in both La2Cu2O5 and La8Cu7O19. For low Zn-doping (x<0,04), a spin-chain like behavior is found. This quasi-one-dimensional behavior is strongly suppressed in both series for x>0,04: Here, the maximum (characteristic for spin chains) in x(T) disappears and x(T) decreases monotonically with increasing temperature.
C. Sekar, B. Schüpp-Niewa, G. Krabbes, M. Wolf, D. Eckert, M. Knapp, K.-H. Müller, Journal of Solid State Chemistry 178 (2005) 28-35

A0751 – Characterization and possible uses of ashes from wastewater treatment plants

This work, on the ashes from the wastewater treatment plant of Galindo (Vizcaya, Spain), has been outlined with the purpose of finding their physico-chemical properties and suggesting possible applications. Ashes contain important quantities of iron, calcium, silica, alumina and phosphates. X-Ray diffraction data make it possible to estimate the mineralogical compositions of the original ashes and also, after thermal treatment at 1200 and 1300°C, the main reactions occurring in thermal treatment. Particle size analysis makes it possible to classify ashes as a very fine powdered material. The thermal treatment leads to a densification of the material and provokes losses of weight mainly due to the elimination of water, carbon dioxide and sulphur trioxide. Application tests show that ashes are not suitable for landfill and similar applications, because of their plastic properties. Testing for pozzolanic character, after the ashes had been heated at 1200°C, did not lead to a strong material probably due to low contents in silica and alumina or to requiring a higher heating temperature. Thermal treatment leads to densification of the material with a considerable increase of compressive strength of the probes. The use of additives (clays and powdered glass) to improve ceramic properties of ashes will be the aim of a future work.
I. Merino, L.F. Arévalo, F. Romero, Waste Management 25 (2005) 1046-1054

A0752 – Modification of the oxidation behaviour of Si3N4-TiB2 composites by PECVD alumina coatings

A nearly fully dense (>98%) electroconductive silicon nitride-35 vol.% titanium diboride composite was obtained by hot isostatic pressing (HIP) in presence of a low content of sintering aids (0.5 wt.% Y2O3 + 0.25 wt.% Al2O3). To improve the oxidation behaviour of this composite material, a 3- m thick protective coating of aluminium oxide was deposited on cubic samples (4mm x 4mm x 4 mm) by microwave plasmaenhanced chemical vapor deposition (PECVD) using an oxygen plasma and an organometallic precursor (trimethylaluminium). SEM images demonstrated that the coating was homogeneously distributed on the external surface of the specimens. Non-isothermal and isothermal oxidation tests were carried out with a Setaram Microbalance under pure flowing oxygen (10 L/h) on both uncoated and coated Si3N4-TiB2 samples. In the case of non-isothermal oxidation of a substrate without coating, the reaction started at 600°C. Between 1100 and 1350°C, a plateauwas observed and above 1350°C the weight gain increased significantly. In presence of an Al2O3 coating, the composite started to oxidize at higher temperature (1200°C). Isothermal kinetics recorded for 24 h, at 1350 and 1400°C, revealed that the presence of the Al2O3 coating improved drastically the oxidation resistance and changed the shape of the curves from globally parabolic to almost logarithmic. An explanation of this protective behaviour, based on the characterization by XRD, SEM and EDS of the reaction products, is proposed.
B. Vasques, C. Tixier, R. Klein, H. Hidalgo, P. Tristant, J. Desmaison, Journal of the European Ceramic Society 25 (2005) 1749-1755

A0755 – Nanocrystalline ceria from carbon free materials

Nanocrystalline ceria powders were synthesized using carbon free starting materials, viz. Ce(NO3)3 6H2O, hydrazine and ammonium nitrate. Thermal decomposition of the precursors was studied by TG-DTA. The powders obtained in both the cases have crystallite size of about 13 nm, as calculated by X-ray line broadening, and a high surface area of >75 m2/g. The deagglomeration behaviour was also investigated, by dynamic light scattering experiments, for the two powders to ascertain the nature of agglomerates. The sintered density of the powders after sintering in air at 1250°C for 2 h was found to be about 94% and 90%, respectively, of the theoretical density, for hydrazine and ammonium nitrate derived products.
S.V. Chavan, A.K. Tyagi, Ceramics International 31 (2005) 731-735

A0754 – High-temperature oxidation of AlN-SiC-TiB2 ceramics in air

The oxidation behaviour of AlN-SiC-TiB2 composite materials with 2, 5 and 10 mass% TiB2 and 3 mass% Fe additive obtained using powder metallurgy methodswas studied in air up to 1500°C by thermogravimetry (TG) and differential thermal analysis (DTA) techniques. The phase composition and structure of the oxide films formed were investigated using metallography, X-ray diffraction (XRD) and electron probe microanalysis (EPMA) methods. The two-stage character of non-isothermal oxidation kinetics (heating rate of 15 grade/min) of composites was established. During the first oxidation stage (up to 1350°C), the formation of alpha-Al2O3, TiO2 (rutile), B2O3 and beta-cristobalite as well as different aluminium borates was found. They formed as a result of interaction between Al2O3 and melted B2O3. During the second stage (above 1350-1400°C), the mullite 3Al2O3.2SiO2 proved to be a main oxidation product in the scale; besides, some amounts of beta-Al2TiO5 were formed as well. The iron additive dissolved in the mullite and aluminium titanate phases that led to the stabilization of a scale formed. It was established that for the three different TiB2 contents, oxidation isotherms follow the parabolic or paralinear rate law. The slope change on the Arrhenius plot given by the dependence of the parabolic rate constants on the reciprocal temperature, suggests a change of the oxidation mechanism in the temperature range of 1300-1350°C. For example, for the (AlN-SiC)-5% TiB2 composite specimen, the calculated values of apparent activation energy are equal to 285 kJ/mol (1100-1300°C) and 500 kJ/mol (1350-1550°C), respectively. The AlN-SiC-TiB2 ceramics developed here can be recommended as high-performance materials for a use in oxidizing medium up to 1450°C.
V.A. Lavrenko, J. Desmaison, A.D. Panasyuk, M. Desmaison-Brut, E. Fenard, Journal of the European Ceramic Society 25 (2005) 1781-1787

A0753 – Structures, phase transitions and electrical properties of Ag5Te2-ySeyCl (y = 0-0.7)

Herein we report the structural, thermal and physical properties of Ag5Te2-ySeyCl (y = 0-0.7). Polymorphic Ag5Te2Cl (y = 0) is an ion conductor with two reversible phase transitions at 241 and 334 K. While the monoclinic room temperature beta- and the low temperature y -phase show conductivities below ? = 10^(-3) ohm-1 cm-1, the tetragonal high temperature alpha-phase is a promising conductor for electronic devices with conductivities up to 10^(-1) ohm-1 cm-1 in addition to high moisture and photo stability. The alpha-beta-phase transition temperature of ion conducting Ag5Te2Cl can be lowered by partial substitution of tellurium by selenium. From differential thermal analysis (DTA) and differential scanning calorimetry (DSC) a linear decrease of the alpha-beta-phase transition temperature with increasing compositional parameter y to a minimum transition temperature of 239 K was observed for Ag5Te1.3Se0.7Cl. Phases up to a maximum selenium content of y = 0.7 were stabilized by preservation of the beta- and alpha-Ag5Te2Cl structure types. Ag5Te2-ySeyCl (y = 0-0.9) phases were characterised by powder X-ray diffraction (XRD) at room temperature. The stabilization of the alpha-Ag5Te2Cl structure type in Ag5Te2-ySeyCl around room temperature results in an increase of conductivity of more than 2 orders of magnitude compared to the ternary phase. Conductivity of up to ? = 5.1 x 10^(-2) ohm-1 cm-1 (314 K, alpha-Ag5Te1.6Se0.4Cl) was observed by impedance spectroscopy. In the range from room temperature down to 239 K any transition temperature can be chosen by simply varying the composition.
T. Nilges, C. Dreher, A. Hezinger, Solid State Sciences 7 (2005) 79-88

A0756 – Oxidation behaviour of an aluminium nitride-hafnium diboride ceramic composite

An aluminium nitride-hafnium diboride electroconductive particulate composite was produced via hot isostatic pressing without sintering aids. Oxidation kinetics studies were performed up to 1350°C under a flow of pure oxygen using a microbalance. The reaction products were analysed using SEM and XRD techniques. This composite had a high oxidation resistance up to 1200°C. The kinetic curves had an asymptotic or paralinear shape. The formation of a protective oxide scale containing hafnia (HfO2) and aluminium borate (Al18B4O33) phases embedded in a glassy phase was observed. The evaporation of B2O3 was limited by the formation of refractory aluminium borate. Above 1200°C, morphological observations showed the formation of a Maltese cross structure associated with the cracking of the oxide scale along the edges resulting in sigmoidal oxidation kinetics and in a high oxidation rate of the ceramic composite.
D. Mattia, M. Desmaison-Brut, S. Dimovski, Y. Gogotsi, J. Desmaison, Journal of the European Ceramic Society 25 (2005) 1789-1796

A0757 – H-titanate nanotube: a novel lithium intercalation host with large capacity and high rate capability

Nanostructured electrodes have been shown to exhibit enhanced rate capability and large discharge/charge capacity for lithium intercalation and extraction. In this paper, electrode made of H-titanate nanotubes show large lithium intercalation capacity, high discharge/charge rate capabilities and excellent cycling stabilities. A facile way is adopted to fabricate well-dispersed nanostructured electrode film by in situ ultrasonic dispersion in N-methyl pyrrolidone. The electrode film containing H-titanate nanotubes, conductive black and polyvinylidene fluoride binder is coated on aluminum foil. The material exhibits an initial discharge capacity of 282.2 mAh/g at a current density of 0.24 A/g, and keeps a stable cycling discharge capacity of 210, 185.7 and 165.9 mAh/g at current density of 0.24, 1.0 and 2.0 A/g, respectively, demonstrating large reversible capacity and excellent rate capabilities. An about 100% of coulombic efficiency implies the perfect reversibility of lithium intercalation into and release from the H-titanate nanotubes and thus the extraordinary cycling stability. The results indicate that this layered, open ended nanotubes may become a candidate for novel lithium storage material with high capacity, high rate capability and excellent cycling stability.
J. Li, Z. Tang, Z. Zhang, Electrochemistry Communications 7 (2005) 62-67

A0758 – The effect of the reduction temperature on the structure of Cu/ZnO/SiO2 catalysts for methanol synthesis

The structure of Cu/SiO2 and Cu/ZnO/SiO2 catalysts was studied after reduction at 450-1300 K. The influence of the ZnO promoter on the exposed Cu surface area and metal cluster size was determined by N2O chemisorption and X-ray diffraction. After reduction at 450 K, the metal surface area amounted to 9 m2/gcat for both catalysts. Oxygen uptake during N2O chemisorption increased significantly up to reduction temperatures of 800-900 K. This increase was most prominent for the ZnO-promoted catalyst, although no oxygen uptake was observed for a similarly treated ZnO/SiO2 sample. The behaviour of the promoted catalyst can be explained by formation of Zn0, surface alloying, and segregation of ZnOx species on top of Cu clusters. The high thermostability of the catalysts was confirmed by in situ XRD measurements. The Cu crystallite size in both catalysts was about 4 nm, and did not increase when the reduction temperature was raised to 1100 K for 1 h.
E.D. Batyrev, J.C. van den Heuvel, J. Beckers, W.P.A. Jansen, H.L. Castricum, Journal of Catalysis 229 (2005) 136-143

A0759 – Processing and characterization of sol-gel fabricated mixed metal aluminates

Nanocrystalline lanthanum aluminate (LaAlO3, LAP) and Sr-substituted LAP ceramics were synthesized by sol-gel processes using mixtures of inorganic salts of the respective elements. The metal ions, generated by dissolving metal nitrates or acetates in acetic acid and/or water were complexed by 1,2-ethanediol to obtain the precursor for LAP. The XRD patterns of the LaAlO3 and La1-xSrxAlO3-d (x < 0.50) ceramic sintered at 1000°C were almost identical with the perovskite LAP composition. The phase transformations, composition and microstructural features in the gels and polycrystalline samples were studied by thermal analysis (TG/DTA), powder X-ray diffraction analysis (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and inductively coupled argon plasma emission spectroscopy (ICP). The quality of the resulting products (homogeneity, crystallisation temperature, grain size and grain size distribution, etc.) of the "chimie douce" synthetic route is discussed.
M. Chroma, J. Pinkas, I. Pakutinskiene, A. Beganskiene, A. Kareiva, Ceramics International 31 (2005) 1123-1130

A0761 – Thermochemistry of iron manganese oxide spinels

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (MnxFe(1-x))3O4 at 298K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe3O4 (magnetite), is negative from x = 0 to x = 0,67 and becomes slightly positive for 0.67oxo1.0. Relative to cubic Mn3O4 (stable at high temperature) and cubic Fe3O4 (magnetite), the enthalpy of formation is negative for all compositions. The enthalpy of formation is most negative near x = 0,2: There is no significant difference in the trend of enthalpy of formation versus composition for cubic (x<0,6) and tetragonal (x>0,6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. DSmix; consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0,5; but the entropy of mixingappears to be smaller than these predicted values for x<0,4.
S. Guillemet-Fritsch, A. Navrotsky, P. Tailhades, H. Coradin, M. Wang, Journal of Solid State Chemistry 178 (2005) 106-113

A0760 – Characterization of Al2O3-Al nano-composite powder prepared by a wet chemical method

A wet chemical method was used to prepare Al2O3-coated Al nano-size-composite powders using Al, aluminum nitrate and ammonia as the starting materials. TEM, SEM, TG/DSC, zeta potential, XPS, X-ray were used to characterize the composite powders. Results showed that a uniform thin Al(OH)3 layer can formed on the surface of Al particles. After calcined at 1000°C for 2 h, the thin Al(OH)3 layer transforms to a-Al2O3 with mean size about 20 nm resulting in well dispersed Al2O3-Al composite powder.
H-X Lu, J. Hu, C-P. Chen, H-W. Sun, X. Hu, D-L. Yang, Ceramics International 31 (2005) 481-485

A0762 – Sucrose combustion synthesis of LaxSr(1-x)MnO3 (x<0.2) powders

An energy efficient combustion synthesis has been used for the preparation of nanocrystalline LSM powder of composition La(1-x)SrxMnO3 (x < 0.2) using sucrose as a polymerisable fuel. Nitrate salt of La3+ and Sr2+ and acetate of Mn2+ were dissolved in water along with sucrose and concentrated by heating in to the form of a viscous resin which is then transformed in to macro porous foam by drying at 120°C. Phase pure LSM has been obtained by combustion of these foams initiated with a matchstick in a set up fabricated in our laboratory. A minimum of 2 moles of sucrose is required for one mole of LSM ions for the formation of perovskite LSM phase. The LSM powder obtained by planetary milling of the combustion ash shows particle size in the range 0.1-6 mm with a D50 value 0. 2 mm. The crystallite size calculated from XRD data using Scherer equation is in the range 13.12-17.9 nm. More than 97% TD has been achieved by cold compaction and sintering at of these powders.
K. Prabhakaran, J. Joseph, N.M. Gokhale, S.C. Sharma, R. Lal, Ceramics International 31 (2005) 327-331

A0764 – Structure and magnetism in Ho(1-x)Sr(x)CoO(3-d)

We have magnetically and structurally characterized the Ho(1-x)Sr(x)CoO(3-d) family of materials where 0.67
D.J. Goossens, K.F. Wilson, M. James, Journal of Physics and Chemistry of Solids 66 (2005) 169-175

A0763 – Synthesis of a new microporous gallophosphate obtained by in situ generation of cyclohexylamine

A novel gallophosphate [Ga13(PO4)18(C6H14N)13(C6H13N).2H3O+ .3H2O] was synthesized using cyclohexylformamide as main solvent. The structure-directing agent is the cyclohexylamine which is generated in situ by thermal decomposition of the solvent. The structure was solved by single-crystal X-ray diffraction (space group P-3, a = 16.605(14) Å, c = 17.22(2) Å, Z = 1, V = 4112(6) Å3). The 2D structure of Mu-30 is built up from (4,6) layers constituted of PO4 tetrahedra sharing three of their oxygen atoms with one GaO6 octahedron and two GaO4 tetrahedra. Monoprotonated cyclohexylamine, water molecules and H3O+ ion are intercalated between the layers. Characterizations of this new gallophosphate by bulk chemical analysis, scanning electron microscopy, thermal analysis, and 13C and 31P solid state NMR spectroscopies are also reported.
L. Lakiss, A. Simon-Masseron, V. Gramlich, J. Patarin, Solid State Sciences 7 (2005) 141-148

A0765 – Correlation between the basicity of solid bases and their catalytic activity towards the synthesis of unsymmetrical organic carbonates

The correlation between the basic properties of solid catalysts and the reaction rate of the selective synthesis of unsymmetrical organic carbonates via direct condensation of diethylcarbonate (DEC) and alcohols was investigated. A detailed kinetic study of the transesterification of 1-phenylethanol and DEC was made with catalysts with different basic strengths. The solids included fluorinated hydrotalcite,MgLa mixed oxides, CsF (pure or supported on alpha- and gamma -aluminas), KF (pure or supported on alpha- and gamma -aluminas), anatase, rutile, and zirconia. Basic properties were determined by the adsorption of CO2, measured by gravimetry coupled with mass spectrometry and by calorimetry. Both techniques show a higher basicity for MgLa mixed oxides. The rate of the reaction was roughly proportional to the number of strongly basic sites present on the catalyst, except for CsF/alpha-Al2O3, which showed higher activity for several different substrates in spite of a lower number and strength of basic sites. This is attributed to the high nucleophilicity of the alcoholate formed as an intermediate. The addition of water to the reaction medium induces two effects: inhibition of the reaction and the promotion of etherification of the substrate by ethanol as a side reaction. The catalysts can be reused several times with a small loss of activity.
B. Veldurthy, J-M. Clacens, F. Figueras, Journal of Catalysis 229 (2005) 237-242

A0767 – Crystal structure, conductivity and reversible water uptake of new layered potassium antimonates K(x)L((1+x)/3)Sb((2-x)/3)O2 (L = Ni2+, Mg2+, Co2+)

Novel mixed potassium antimonates K0.59Mg0.53Sb0.47O2, K0.5Ni0.5Sb0.5O2, K0.5Co0.5Sb0.5O2 (rhombohedral P3-type structure), K0.56Ni0.52Sb0.48O2 and K0.86Co0.62Sb0.38O2 (hexagonal P2 type) have layered structures based on brucite-like (L,Sb)O6/3 sheets of edge-shared octahedra and interlayer K+ cations in trigonal prismatic coordination. The preference to form P2 and P3 structures rather than closely related O3 type is dictated by the large radius of K+ and the value of unit cell parameter a, restricted by average size of the cations randomly distributed in the octahedral sites within (L,Sb)O6/3 layer. The new phases reversibly absorb atmospheric moisture leading to the formation of hydrates with ca. 11% larger interlayer distances. The impedance spectroscopy of P2-type K0.56Ni0.52Sb0.48O2 and P3-type K0.59Mg0.53Sb0.47O2 ceramics shows relatively high ionic conductivity, presumably due to potassium cationic transport, with activation energies of 3572 and 3371 kJ/mol, respectively. At 573 K, the conductivity values are 0.016 S/cm for K0.56Ni0.52Sb0.48O2 and 0.021 S/cm for K0.59Mg0.53Sb0.47O2. Interaction with water vapor leads to increasing total conductivity.
O.A. Smirnova, V.B. Nalbandyan, M. Avdeev, L.I. Medvedev, B.S. Medvedev, V.V. Kharton, F.M.B. Marques, Journal of Solid State Chemistry 178 (2005) 172-179

A0766 – Evolution of oxide scales on an ODS FeAl intermetallic alloy during high temperature exposure in air

The oxide dispersion strengthened FeAl Grade 3 intermetallic alloy have been shown to develop a structured oxide scale upon isothermal oxidation between 850 and 950°C for 24 h. Transmission electron microscopy studies have revealed a top nanoequiaxed alumina, alumina and Fe-Al spinel at the outer, central and internal layers, respectively. At 1000°C, the spinel phase no longer forms but a columnar alumina layer topped by a nanoequiaxed structure. The role of yttria is negligible at lower temperatures whereas some segregation at the scale/substrate interface and precipitation of YAlO3 is observed at 1000°C.
F. Pedraza, J.L. Grosseau-Poussard, J.F. Dinhut, Intermetallics 13 (2005) 27-33

A0769 – Mesoporous silica functionalized with 2-mercaptopyridine: Synthesis, characterization and employment for Hg(II) adsorption

Mesoporous silicas (SBA-15 and MCM-41) have been functionalized by two different methods. Using the heterogeneous route the silylating agent, 3-chloropropyltriethoxysilane, was initially immobilized onto the mesoporous silica surface to give the chlorinated mesoporous silica Cl-SBA-15 or Cl-MCM-41. In a second reaction a multifunctionalized N, S donor compound (2-mercaptopyridine, MP) was incorporated to obtain the functionalized silicas denoted as MP-SBA-15-Het or MP-MCM-41-Het. Using the homogeneous route, the functionalization was achieved via the one step reaction of the mesoporous silica with an organic ligand containing the chelating functions, to give the modified mesoporous silicas denoted as MP-SBA-15-Hom or MP-MCM-41-Hom. When the functionalized mesoporous silicas were employed as adsorbents for the regeneration of aqueous solutions contaminated with Hg(II), mercury adsorption was higher in the mesoporus silicas prepared by the homogeneous method. The modified mesoporous silica MP-SBA-15-Hom displayed the best mercury adsorption efficiency.
D. Pérez-Quintanilla, I. del Hierro, M. Fajardo, I. Sierra, Microporous and Mesoporous Materials 89 (2006) 58-68

A0768 – Nitridation under ammonia of high surface area vanadium aerogels

Vanadium pentoxide gels have been obtained from decavanadic acid prepared by ion exchange on a resin from ammonium metavanadate solution. The progressive removal of water by solvent exchange in supercritical conditions led to the formation of high surface area V2O5, 1.6H2O aerogels. Heat treatment under ammonia has been performed on these aerogels in the 450-900°C temperature range. The oxide precursors and oxynitrides have been characterized by XRD, SEM, TGA, BET. Nitridation leads to divided oxynitride powders in which the fibrous structure of the aerogel is maintained. The use of both very low heating rates and high surface area aerogel precursors allows a higher rate and a lower threshold of nitridation than those reported in previous works. By adjusting the nitridation temperature, it has been possible to prepare oxynitrides with various nitrogen enrichment and vanadium valency states. Whatever the V(O,N) composition, the oxidation of the oxynitrides in air starts between 250 and 300°C. This determines their potential use as chemical gas sensors at a maximum working temperature of 250°C.
O. Merdrignac-Conanec, K. El Badraoui, P. L'Haridon, Journal of Solid State Chemistry 178 (2005) 218-223

A0770 – Incorporation of RuO2 nanoparticles into MFI-type zeolites

Ruthenium oxide particles were introduced into the medium-pore zeolite ZSM-5 (MFI) by ion exchange in aqueous suspension and by the addition of ruthenium chloride to the synthesis gel in hydrothermal zeolite syntheses. The latter approach was systematically studied in the presence and absence of tetrapropyl ammonium ions as organic structure-directing agents. The materials were characterized by chemical analysis, XRD, SEM, XANES, EXAFS, HRTEM, hydrogen chemisorption and the competitive hydrogenation of 1-hexene and 2,4,4-trimethyl-1-pentene. This catalytic test reaction was applied to discriminate between ruthenium species in the zeolite pores and on the outer crystal surface. The addition of ruthenium chloride during the zeolite synthesis strongly affects the rate of crystallization. In the case of the template-free synthesis, the presence of ruthenium chloride in the synthesis gel also changes the size and the morphology of the zeolite crystals. Independent of the preparation conditions, the ruthenium species are oxidized during the hydrothermal synthesis or during the post-synthesis modification to ruthenium oxide with ruthenium in the oxidation state +IV. However, by ion exchange in aqueous suspension or by adding ruthenium chloride to the gel of a tetrapropyl ammonium-templated hydrothermal synthesis with subsequent calcination, large anhydrous ruthenium oxide particles are formed. These are predominantly located on the outer surface of the zeolite crystals. Upon adding ruthenium chloride to a template-free gel of a hydrothermal ZSM-5 synthesis, hydrous ruthenium oxide nanoparticles can be prepared. The majority of these particles are between 0.5 nm and 0.9 nm in diameter, located inside the pores of the MFI structure, and are, thus, available for shape-selective catalytic conversions.
S. Altwasser, R. Glaser, A. Sulaiman Lo, P-H Liu, K-J Chao, J. Weitkamp, Microporous and Mesoporous Materials 89 (2006) 109-122

A0772 – Preparation, characterization and catalytic behavior in methanol decomposition of nanosized iron oxide particles within large pore ordered mesoporous silicas

Nanosized iron oxide particles within various ordered mesoporous silicas (SBA-15, SBA-16, Fm3m, Ia3d) have been prepared from the corresponding nitrate and acetylacetonate precursors. N2 physisorption, X-ray diffraction and Moessbauer spectroscopy are used for their characterization. The reductive properties of the modified materials were investigated by temperature-programmed reduction with hydrogen. Methanol decomposition to H2, CO and methane was used as a test reaction. Some differences in the iron state, its phase transformations in reductive medium and also some variations in its catalytic behavior were observed and discussed in view of the iron oxide particle size dispersion and its dependency on the pore geometries of the silica supports.
T. Tsoncheva, J. Rosenholm, C.V. Teixeira, M. Dimitrov, M. Linden, C. Minchev, Microporous and Mesoporous Materials 89 (2006) 209-218

A0771 – 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.
P. Kirszensztejn, R. Przekop, A. Szymkowiak, E. Mackowska, J. Gaca, Microporous and Mesoporous Materials 89 (2006) 150-157

A0775 – Structure, phase transitions and molecular dynamics in 4-aminopyridinium hexachloroantimonate(V), [4-NH2C5H4NH][SbCl6]

4-Aminopyridinium hexachloroantimonate(V), [4-NH2C5H4NH][SbCl6], abbreviated to 4APCA, crystallizes at room temperature in the monoclinic system, space group P21/c (phase III). The crystal undergoes two reversible phase transitions of first order type at 386/346 K (II4III) and at 467/466 K (I4II) on heating-cooling runs. Dielectric studies suggest the plastic crystal's behavior above 386 K (phase II). The proton NMR second moment (M2) and the1H NMR spin-lattice relaxation time (T1) for 4APCA measured between 77 and 420 K revealed the C2 reorientation of the 4-aminopyridinium cations. The mechanism of the phase transitions in 4APCA at 386 K is discussed.
B. Kulicka, R. Jakubas, A. Pietraszko, W. Medycki, J. S wiergiel, Journal of Molecular Structure 783 (2006) 88-95

A0774 – Spectroscopic characterization of chosen Ln(III) polyoxometalate complexes with organic counter cations in solid and in non-aqueous solutions

Polyoxometalate (POM) compositions containing organic counter cations and SiMo2W9O39 8- polyanion have been synthesized using extraction. Several compounds with counter ions containing phosphorus such as: Ph3P+CPh3, Ph3P+Et, Ph3P+C16H33, Ph4P+, Bu4P+ were obtained and their Eu(III) complexes synthesized. Luminescence characterization of the europium complexes concerning their intensities, quantum yields and luminescence lifetimes of Eu(III) ion both in DMF solutions and solid are discussed. The complexation study has been carried out analyzing absorption spectra of Nd(III) ion in the range of its hypersensitive transition (4I9/2 => 2H9/2). Results indicated formation of the Ln(POM)2 sandwich complexes. Computer-assisted target factor analysis has been applied to evaluate the spectra of Nd(III) in DMSO solutions containing varying amounts of the POM. The conditional formation constants with lg beta12 = 8.6±0.5, lg beta12 = 8.2±0.4 and lg beta12 = 9.6±0.7 were obtained for (Ph3PEt)5H3SiMo2W9O39, (Ph3PC16H33)7HSiMo2W9O39 and (Ph3PCPh3)6H3SiMo2W9O39, respectively. Studies have shown significant influence of the counter ion structure on the luminescence properties of Eu(III) in the systems studied. The most intensive luminescence and the highest value of quantum yield were observed in the case of the complex (Ph3PCPh3)7H6Eu(SiMo2W9O36)2, containing six phenyl groups in the organic counter cation.
S. Lis, S. But, G. Meinrath, Journal of Alloys and Compounds 408-412 (2006) 958-961

A0773 – Catalytic ozonation of natural organic matter on alumina

The paper aims to show the potential of catalytic ozonation in the presence of alumina for the removal of natural organic mater from drinking water. An investigation into the efficiency of catalytic ozonation, ozonation by-products formation and their biodegradability was the main goal of the paper. Characterisation of fresh and worn alumina was also conducted. The results clearly indicated the high activity of alumina over a long period of time, which is crucial in water treatment technology. The application of alumina to the ozonation system doubled the efficiency of NOM removal from water when compared to ozonation alone. Furthermore, catalytic ozonation resulted in lower by-products and biodegradable organic carbon formation.
B. Kasprzyk-Hordern, U. Raczyk-Stanislawiak, J. Swietlik, J. Nawrocki, Applied Catalysis B: Environmental 62 (2006) 345-358

A0778 – Mixed conductivity, stability and thermomechanical properties of Ni-doped La(Ga,Mg)O(3-d)

Perovskite-type LaGa0.65Mg0.15Ni0.20O(3-d) exhibiting oxygen transport comparable to that in K2NiF4-type nickelates was characterized as a model material for ceramic membrane reactors, employing mechanical tests, dilatometry, oxygen permeability and faradaic efficiency measurements, thermogravimetry (TG), and determination of the total conductivity and Seebeck coefficient in the oxygen partial pressure range from 10^(-15) Pa to 40 kPa. Within the phase stability domain which is similar to La2NiO(4+d), the defect chemistry of LaGa0.65Mg0.15Ni0.20O(3-d) can be adequately described by the ideal solution model with oxygen vacancies and electron holes to be the only mobile defects, assuming that Ni2+ may provide two energetically equivalent sites for hole location. This assumption is in agreement with the density of states, estimated from thermopower, and the coulometric titration and TG data suggesting Ni4+ formation in air at T <1150 K. The hole conductivity prevailing under oxidizing conditions occurs via small-polaron mechanism as indicated by relatively low, temperature-activated mobility. The ionic transport increases with vacancy concentration on reducing p(O2) and becomes dominant at oxygen pressures below 10^(-7) - 10^(-5) Pa. The average thermal expansion coefficients in air are 11.9 x 10^(-6) and 18.4 x 10(-6) K-1 at 370-850 and 850-1270 K, respectively. The chemical strain of LaGa0.65Mg0.15Ni0.20O(3-d) ceramics at 1073-1123 K, induced by the oxygen partial pressure variations, is substantially lower compared to perovskite ferrites. The flexural strength determined by 3-point and 4-point bending tests is 167-189 MPa at room temperature and 85-97 MPa at 773-1173 K. The mechanical properties are almost independent of temperature and oxygen pressure at p(O2)=1-2.1x10^4 Pa and 773-1173 K.
A.A. Yaremchenko, V.V. Kharton, E.N. Naumovich, D.I. Shestakov, V.F. Chukharev, A.V. Kovalevsky, A.L. Shaula, M.V. Patrakeev, J.R. Frade, F.M.B. Marques, Solid State Ionics 177 (2006) 549-558

A0776 – Neutron powder diffraction studies of NdSrNi(1-x)CuxO(4-d), 0

Compounds from the solid solution NdSrNi(1-x)CuxO(4-d), 0 < x < 1, have been prepared using conventional solid state methods and were characterized by X-ray powder diffraction, thermo-gravimetric analysis and magnetic susceptibility measurements. The samples adopt the K2NiF4-type structure. For x = 0.2 and x = 0.6, neutron diffraction measurements were performed and bond-valence sums (BVSs) were calculated from the Brown bond valence calculation theory. Magnetic susceptibility data for all the compositions follow Curie-Weiss behavior in the temperature range 100-300 K with no evidence of long range magnetic ordering down to 2 K. The effect of Cu2+ incorporation on the magnetic properties of NdSrNi(1-x)CuxO(4-d), 0 < x < 1, is discussed.
H. Chaker, T. Roisnel, O. Cador, M. Amami, R. Ben Hassen, Solid State Sciences 8 (2006) 142-148

A0779 – Synthesis and characterization of CuFeO2+d delafossite powders

Effects of oxygen off-stoichiometry have been investigated on CuFeO2+d delafossite-type powders prepared by solid state reaction. Materials annealed at different temperatures under air atmosphere were compared. Thermogravimetric analysis coupled with X-ray structural analysis showed that a powdered CuFeO2 can be oxidized up to CuFeO2+d with d =0.18. Electrical measurements confirm the existence of oxidized CuFeO2+d phases. Particular attention is paid to the correlation between oxidation process and phase stabilities in the CuFeO2 and copper spinel phase system.
E. Mugnier, A. Barnabé, P. Tailhades, Solid State Ionics 177 (2006) 607-612

A0780 – Study of an iron-manganese Fischer-Tropsch synthesis catalyst promoted with copper

The metal-silica interaction and catalytic behavior of Cu-promoted Fe-Mn-K/SiO2 catalysts were investigated by temperature-programmed reduction/desorption (TPR/TPD), differential thermogravimetric analysis, in situ diffuse reflectance infrared Fourier transform analysis, and Mössbauer spectroscopy. The Fischer-Tropsch synthesis (FTS) performance of the catalysts with or without copper was studied in a slurry-phase continuously stirred tank reactor. The characterization results indicate that several kinds of metal oxide-silica interactions are present on Fe-Mn- K/SiO2 catalysts with or without copper, which include iron-silica, copper-silica, and potassium-silica interactions. In addition to the well-known effect of Cu promoter on easing the reduction of iron-based FTS catalysts, it is found that Cu promoter can increase the rate of carburization, but does not vary the extent of carburization during the steady-state FTS reaction. The basicity of the Cu and K co-promoted catalyst is greatly enhanced, as demonstrated by CO2-TPD results. In the FTS reaction, Cu improves the rate of catalyst activation and shortens the induction period, whereas the addition of Cu has no apparent influence on the steady-state activity of the catalyst. Promotion of Cu strongly affects hydrocarbon selectivity. The product distribution shifts to heavy hydrocarbons, and the olefin/paraffin ratio is enhanced on the catalyst due to the indirect enhancement of surface basicity by the copper promotion effect.
C-H. Zhang, Y. Yang, B-T. Teng, T-Z. Li, H-Y. Zheng, H-W. Xiang, Y-W. Li, Journal of Catalysis 237 (2006) 405-415

A0781 – Increasing the hydrothermal stability of mesoporous SiO2 with methylchlorosilanes – a structural study

Mesoporous silica gels with various pore sizes are hydrophobised by liquid-phase silylation with mono- and difunctional methylchlorosilanes. Changes in the pore structure as a result of the silylation reactions are monitored in order to assess the distribution of the hydrophobic groups. Extensive polymerisation of dimethyldichlorosilane (DMDCS) causes blocking of the micropore fraction. For silica with pore sizes in the supermicroporous range (2 nm pore diameter), this leads to hydrophobisation of almost exclusively the outer surface. While for trimethylchlorosilane (TMCS) a smaller number of molecules react with the surface, modification is more homogeneous and an open structure is optimally preserved. Both silanes lead to lower surface polarity and increased hydrothermal stability, i.e., preservation of the porous structure during exposure to water. As DMDCS reacts more extensively, this agent would be recommended for ceramics with pore diameters larger than about 6 nm. TMCS is the most suitable agent for pore diameters smaller than 4 nm and in case preservation of micropores is required.
H.L. Castricum, M.C. Mittelmeijer-Hazeleger, A. Sah, J.E. ten Elshof, Microporous and Mesoporous Materials 88 (2006) 63-71

A0783 – Palladium(II) and platinum(II) monoselenocarboxylates: Synthesis, spectroscopy, structure and their use as molecular precursors for metal selenides

Treatment of MCl2(PP) or MCl2(PnPr3)2 with two equivalents of ArCOSeK readily yields cis-[M(SeCOAr)2(PP)] and trans- [M(SeCOAr)2(PnPr3)2], respectively (M = Pd or Pt; Ar = Ph or 4-MeC6H4; PP = dppm, dppe, dppp). The reaction of Pd(SeCOAr) 2(dppe) with PdCl2(dppe) in the presence of NaBPh4 in methanol gave a tri-nuclear ionic complex, [Pd3(l3-Se)2(dppe)3][BPh4]2. These complexes were characterized by UV-Vis, IR and NMR spectroscopy. The complex [Pt(SeCOPh)2(dppp)] has been structurally characterized by X-ray crystallography. The coordination environment around square planar platinum atom is defined by chelating dppp ligand and two unidentate selenocarboxylates bonded through selenium atoms. Pyrolysis of [Pd(SeCOAr)2(PnPr3)2] either in tri-n-butylphosphate (TBP) (at 200°C) or in the solid state (furnace heating at 350°C) gave Pd17Se15.
L.B. Kumbhare, V.K. Jain, B. Varghese, Inorganica Chimica Acta 359 (2006) 409-416

A0782 – Microporous aluminum bisphosphonates

Several bisphosphonates of trivalent elements (Al, Ga and La) have been prepared under different synthetic conditions in order to induce microporosity. Two bisphosphonic acids, 4,40-biphenylenebis(phosphonic acid), [H2O3P-C6H4]2, and 4-(4-phosphonophenoxy) phenyl phosphonic acid, [H2O3P-C6H4]2-O, have been used as crosslinking agents. The materials have been characterized by a number of techniques including N2 adsorption-desorption isotherms and temperature-programmed desorption of ammonia to characterize the specific surface and acid properties, respectively. Crosslinked hybrid materials with surface areas ranging between 100 and 400 m2/g and textural properties varying from non-porous to mainly microporous can be isolated. The use of inexpensive phenylphosphonic acid as a spacer group has also been studied. The experimental conditions to get microporous solids with specific surface areas as high as 400 m2/g are described. Usually, the compounds contain both mesopores and micropores. The micropore size distributions are centered between 7 and 20 A ? .
M. del Mar Gomez-Alcantara, A. Cabeza, L. Moreno-Real, M.A.G. Aranda, A. Clearfield, Microporous and Mesoporous Materials 88 (2006) 293-303

A0784 – Processing and structural characterization of porous reforming catalytic films

Nickel-based catalysts are often used to reform methanol into hydrogen. The preparation and installation of these catalysts are costly and laborious. As an alternative, directly applying catalytic films onto the separator components can improve the manufacturing efficiency. This paper reports the successful deposition of adherent porous NiO-Al2O3-based catalytic films with well-controlled stoichiometry, using a single-step Aerosol Assisted Chemical Vapour Deposition (AACVD) method. The microstructure, composition and crystalline phase of the as-deposited catalytic films are characterized using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FTIR) Spectrometer. The results have demonstrated the capability of AACVD to produce porous NiO-Al2O3-based catalytic films.
X. Hou, J. Williams, K-L. Choy, Thin Solid Films 495 (2006) 262 - 265

A0785 – Influence of the acid-base properties in Si-MCM-41 and B-MCM-41 mesoporous materials on the activity and selectivity of e-caprolactam synthesis

B-MCM-41 mesoporous molecular sieves have been prepared with different B contents (Si/B = 40-10). Three synthesis procedures were compared: (i) direct synthesis by using tetraethyl orthosilicate as the silica source, boric acid as the boron source and the surfactant cetyltrimethylammonium bromide, (ii) direct synthesis with a post-synthesis treatment in NH4F solution and (iii) capillary impregnation of mesoporous Si-MCM-41. The solid structures were analysed by XRD, N2 adsorption, TG-DTA and DRIFT. The surface acidity was determined by TPD and DRIFT by using pyridine as the probe molecule. Furthermore, the presence of acid and basic sites was shown from the conversion of 2-methyl-3- butyn-2-ol. This study indicated that samples obtained by direct synthesis had both acid and basic properties, while fluorinated samples had mainly acid properties and those synthesised by capillary impregnation exhibited predominantly basic properties. Likewise, an increase in boron content produced a decrease in both the intensity of the XRD peaks and BET surface area as well as an increase in total acidity. In the absence of deactivation processes (pulse method), at 573 K, silicates and borosilicates MCM-41 catalysed the formation of by-products of e-caprolactam, although this process was favoured on solids with mainly basic properties. Under continuous flow reaction conditions, at 723 K, results indicated that the incorporation of boron to the Si-MCM-41 framework did not affect the activity and product distribution. Finally, when acetonitrile was used as the solvent in a continuous flow system, although selectivity to e-caprolactam improved, the by-products of e-caprolactam adsorption were also favoured resulting in the deterioration of catalyst life.
T.D. Conesa, J.M. Hidalgo, R. Luque, J.M. Campelo, A.A. Romero, Applied Catalysis A: General 299 (2006) 224-234

A0786 – Effect of improving flue gas cleaning on characteristics and immobilisation of APC residues from MSW incineration

The flue gas cleaning system of a MSW incinerator with a capacity of 350 kt/year was changed to improve the HCl elimination efficiency. Instead of the semi-wet operating spray reactor and subsequent baghouse, a two-step wet flue gas cleaning was added behind the baghouse. Elemental composition, X-ray powder diffraction patterns and TGA measurements showed that the resulting APC residue was totally different from the former residue. As a consequence, leaching characteristics of both residues also differed and another treatment was required prior to disposal. For the former residue, mainly leaching of Pb (>100 mg/l), necessitated treatment prior to landfilling. The lower alkalinity of the new residue resulted in a leachate pH of 9.7 and a Pb concentration of 0.8 mg/l. The leachate pH of the former residue was 12.4. The leaching of Pb and Zn increased above 100 mg/l when immobilising the new residue with cement. Better results were obtained when immobilising with micro silica. The high CaCl2.2H2Ocontent of the newresidue brought along clogging of the bag filter system. Adding 1.4% of CaO (or 1.9% of Ca(OH)2) to the residue already improved these inconveniences but again significantly changed the leaching behaviour of the residue.
D. Geysen, C. Vandecasteele, M. Jaspers, E. Brouwers, G. Wauters, Journal of Hazardous Materials B128 (2006) 27-38

A0787 – Carbon dioxide sequestration in municipal solid waste incinerator (MSWI) bottom ash

During bottom ash weathering, carbonation under atmospheric conditions induces physico-chemical evolutions leading to the pacification of the material. Fresh bottom ash samples were subjected to an accelerated carbonation using pure CO2. The aim of this work was to quantify the volume of CO2 that could be sequestrated with a view to reduce greenhouse gas emissions and investigate the possibility of upgrading some specific properties of the material with accelerated carbonation. Carbonation was performed by putting 4 mm-sieved samples in a CO2 chamber. The CO2 pressure and the humidity of the samples were varied to optimize the reaction parameters. Unsieved material was also tested. Calcite formation resulting from accelerated carbonation was investigated by thermogravimetry and differential scanning calorimetry (TG/DSC) and metal leaching tests were performed. The volume of sequestrated CO2 was on average 12.5 L/kg dry matter (DM) for unsieved material and 24 L/kg DM for 4 mm-sieved samples. An ash humidity of 15% appeared to give the best results. The reaction was drastically accelerated at high pressure but it did not increase the volume of sequestrated CO2. Accelerated carbonation, like the natural phenomenon, reduces the dangerous nature of the material. It decreases the pH from 11.8 to 8.2 and causes Pb, Cr and Cd leaching to decrease. This process could reduce incinerator CO2 emissions by 0.5-1%.
E. Rendek, G. Ducom, P. Germain, Journal of Hazardous Materials B128 (2006) 73-79

A0788 – Relation between the oxidation mechanism of nickel, the microstructure and mechanical resistance of NiO films and the nickel purity I. Oxidation mechanism and microstructure of NiO films

The effect of impurities on the oxidation mechanism of nickel and on the mechanical characteristics of NiO films was studied on two industrial nickel grades compared to a pure nickel. In this part, influence of impurities on the oxidation mechanism and on the NiO film microstructure will be detailed. The oxidation mechanism, especially studied at 800°C in air, was clarified using complementary techniques, SEM and STEM microstructural and analytical investigations, XPS analyses, profilometry, oxygen isotopic exchange and SIMS. Depending on the Ni purity, the morphology of the oxide scale and the porosity amount differs. Duplex oxide layers and internal oxidation are observed on industrial grades, while a simple NiO film grows on pure nickel without internal oxidation. An oxidation mechanism, which differs according to the presence or not of impurities in the nickel substrate, is proposed. The mechanical characteristics will be characterised and discussed in the following paper (part II) in relation with the microstructural modifications induced by changing the nickel purity.
A.M. Huntz, M. Andrieux, R. Molins, Materials Science and Engineering A 415 (2006) 21-32

A0790 – Influence of sol-gel derived Al2O3 film on the oxidation behavior of a Ti3Al based alloy

Al2O3 thin films were deposited on a Ti3Al based alloy (Ti-24Al-14Nb-3V-0.5Mo-0.3Si) by sol-gel processing. Isothermal oxidation at temperatures of 900-1000°C and cyclic oxidation at 800-900°C were performed to test their effect on the oxidation behavior of the alloy. Results of the oxidation tests show that the oxidation parabolic rate constants of the alloy were reduced due to the applied thin film. This beneficial effect became weaker after longer oxidation time at 1000°C. TiO2 and Al2O3 were the main phases formed on the alloy. The thin film could promote the growth of Al2O3, causing an increase of the Al2O3 content in the composite oxides, sequentially decreased the oxidation rate. Nb/Al enriched as a layer in the alloy adjacent to the oxide/alloy interface in both the coated and uncoated alloy. The coated thin film decreased the thickness of the Nb/Al enrichment layer by reducing the scale growth rate.
M. Zhu, M. Li, Y. Li, Y. Zhou, Materials Science and Engineering A 415 (2006) 177-183

A0789 – Cadmium removal from aqueous solutions by hydroxy-8 quinoleine intercalated bentonite

An Algerian bentonite was purified and modified by intercalation of 8-hydroxyquinolinium ion. These materials were characterized by X-ray diffraction, infrared spectroscopy, and thermal analysis. Comparative batch experiments were performed using bentonite-oxine complex (B-oxine) and sodic bentonite (B-Na) for removing cadmium from aqueous solutions. Kinetics study results of cadmium removal with B-Na and B-oxine fit a pseudo-second-order model. The adsorption isotherm data follow the Langmuir equation in which parameters were calculated. B-oxine has a better cadmium removal capacity (61.35 mg/g) than B-Na (29.41 mg/g). Calculated thermodynamic parameters using the van't Hoff equation showed that the removal process is endothermic with B-oxine and exothermic with B-Na. A mechanism of ion exchange followed by complexation-precipitation is suggested for cadmium removal with B-oxine.
A. Bentouami, M.S. Ouali, Journal of Colloid and Interface Science 293 (2006) 270-277

A0791 – Oxidative dehydrogenation of i-butane over nanostructured silica-supported NiMoO4 catalysts with low content of active phase

NiMoO4 silica-supported samples (6.5% w/w) were prepared by coprecipitation technique. In order to study the influence of the surface area of the support material, silicas with different surface areas have been used: Durosil (60 m2/g) and Sipernat 22 (190 m2/g) from Degussa and silica prepared in the laboratory (590 m2/g). Nanosized grains of b-NiMoO4 phase were obtained for all the prepared samples. The crystallinity of the active phase (mixed oxide) depends on the nature of the support material. The laboratory-made silica allowed reaching the highest degree of nanocrystallinity (observed by TEM) for the active phase. Results from TPR and ITR show that the sample reducibility depends on the size and crystallinity of the dispersed active phase. All the prepared samples were more reducible than the unsupported NiMoO4 sample due to the presence of b-phase instead a-NiMoO4 phase. In the tested conditions the sample prepared using the silica with the highest surface area displays the highest i-butane conversion, the highest i-butene selectivity and the lowest selectivity towards deep oxidation products.
R. Zavoianu, C.R. Dias, A.P.V. Soares, M.F. Portela, Applied Catalysis A: General 298 (2006) 40-49

A0793 – The oxidation of three Ni-6Si-xAl alloys in 1 atm O2 at 1000°C

The oxidation of three ternary Ni-6Si-xAl alloys containing 6, 10 and 15 at.% Al and of the corresponding binary Ni-Al alloys has been studied at 1000°C under 1 atm O2 to examine the effect of different Al additions on the behavior of ternary Ni-Al-Si alloys containing 6 at.% Si. Of the three binary Ni-Al alloys only Ni-15Al was able to form external alumina scales. Conversely, all the three ternary alloys formed an innermost layer of alumina directly in contact with the alloy following very similar and approximately parabolic kinetics after a short faster initial stage due to transient formation of NiO. Thus, the presence of silicon is very effective to reduce the critical Al content needed to form exclusive alumina scales with respect to binary Ni-Al alloys. The third-element effect due to silicon is interpreted on the basis of an extension of Wagner s criterion for the transition from the internal to the external oxidation of the most reactive component in binary alloys.
Y. Niu, Y. Wu, F. Gesmundo, Corrosion Science 48 (2006) 1-22

A0792 – FTIR spectroscopic study of the nature and reactivity of NOx compounds formed on Cu/Al2O3 after coadsorption of NO and O2

Copper cations present on alumina surface even in low concentrations (0.75 wt %) are characterized by a high heterogeneity. Thus, two kinds of Cu+ sites have monitored by CO adsorption and three kinds of Cu2+ cations by NO adsorption. Adsorption of NO also leads to development of bands due to small amounts of nitro/nitrito and nitrato compounds. Introduction of oxygen to the Cu/Al2O3-NO system causes initial concentration rise of the NO2- compounds followed by oxidation of these complexes to nitrates. The nitrates thus obtained are stable up to 723 K. Surface copper nitrates begin to react with C2H4 at 573 K, as a result of which isocyanate and cyanide species are formed. Simultaneously, oxidation of C2H4 on the catalyst surface proceeds, leading ultimately to the appearance of carboxylates. The mechanism of SCR by ethene on Cu/Al2O3 has been discussed.
T. Venkov, M. Dimitrov, K. Hadjiivanov, Journal of Molecular Catalysis A: Chemical 243 (2006) 8-16

A0794 – Modification of cement hydration at early ages by natural and heated wood

Heat treatments of wood are widely used for the reduction of wood swelling and dimensional instability of wood-cement composites. The effect of natural and heated wood on the hydration of cement at early ages was investigated by isothermal calorimetry, thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy. The addition of wood strongly delays and inhibits the hydration of the silicate phases. Consequently, the amount of portlandite is lower in composites than in neat cement. Approximately 30% of the inhibition of portlandite precipitation is due to an increase of calcium carbonate content in cement paste. The absorption of a part of water by wood produces a decrease in gypsum consumption. Nevertheless, the ettringite formation is not significantly affected since a diffusion of sulfate ions from wood occurs.
A. Govin, A. Peschard, R. Guyonnet, Cement & Concrete Composites 28 (2006) 12-20

A0796 – Hydration of hydratable alumina in the presence of various forms of MgO

This work investigates hydration behavior of hydratable alumina in the presence of several forms of magnesia used for production of refractory castables. The mixtures of hydratable alumina with reactive magnesia, fused magnesite and deadburnt magnesite were hydrated at 20°C and 110°C. The hydration products were determined with X-ray diffractometer and the hydration extent was calculated from thermogravimetric analysis. The results revealed significant difference in the hydration products between the hydratable alumina-reactive magnesia mixture and the hydratable alumina-fused magnesite or deadburnt magnesite mixtures under the hydration conditions. The relationships of the compositions of hydrotalcite-like hydrates with different types of magnesias are elucidated. The bonding formed between hydratable alumina and magnesite aggregate in castables and its effect on the strength of the castables dried at 110°C and fired at 816°C was discussed.
G. Ye, T. Troczynski, Ceramics International 32 (2006) 257-262

A0795 – New open-framework three-dimensional lanthanide oxalates containing as a template the diprotonated 1,2- or 1,3-diaminopropane

Single crystals of three new open-framework lanthanide oxalates have been synthesized hydrothermally, in the presence of 1,2- diaminopropane, (C3N2H12)[Nd(H2O)(C2O4)2]2.3H2O I and (C3N2H12)[Yb(C2O4)2]2.5H2O II, or 1,3-diaminopropane (C3N2H12)2 [La2(C2O4)5].5H2O III. Their structures have been determined by X-ray diffraction data: I and III crystallize in the triclinic system, space group P-1, with a = 7,8130(5) Å, b = 11,8800(6) Å, c = 12,9940(8) Å, alpha = 93,092(5)°, beta = 93,930(6)°, gamma = 108,359(5)° and a = 11,6650(9) Å, b = 11,9240(6) Å, c = 13,2230(7) Å, alpha = 104,585(4)°, beta = 108,268(5)°, gamma = 111,132(5)°, respectively while II crystallizes in the orthorhombic system, space group F2dd, with a = 8,7970(4) Å, b = 16,1550(8) Å, c = 32,170(2) Å. The three-dimensional (3D) framework of these compounds is built up by the linkages of lanthanide atoms and the oxygen atoms of the bischelating oxalate ligands. Instead of four chelating oxalate units surrounding a lanthanide atom (I and II), both lanthanum atoms, in III, are surrounded by five chelating oxalate groups and that is new. In all the cases within the frame, are observed 8- and 12-membered channels where are localized the guest species, 1,2- or 1,3-diaminopropane cations and free water molecules. The ratio of the guest number (especially the diaminopropane) per 12-membered ring could tune the shape and the size of 12-membered channels: thus, the 12-membered channels, observed for I and II, have elliptical cross-section (5.5 Å x 11.4 Å and 5.2 Å x 9.5 Å ) while those, observed for III, have nearly circular cross-section (9.1 Å x 9.5 Å ). The lanthanide atoms are 8, 9 and 10-fold coordinated for Yb (II), Nd (I) and La (III), respectively.
A. Mohanu, C. Brouca-Cabarrecq, J.C. Trombe, Journal of Solid State Chemistry 179 (2006) 3-17

A0797 – Thermogravimetric study of the pyrolysis of biomass residues from tomato processing industry

There is an increasing concern with the environmental problems associated with the increasing CO2, NOx and SOx emissions resulting from the rising use of fossil fuels. Renewable energy, mainly biomass, can contribute to reduce the fossil fuels consumption. Biomass is a renewable resource with a widespread world distribution. Tomato processing industry produces a high amount of biomass residue (peel and seeds) that could be used for thermal energy and electricity. A characterization and thermogravimetric study has been carried out. The residue has a high HHVand volatile content, and a low ash, and S contents. A kinetic model has been developed based on the degradation of hemicellulose, cellulose, lignin and oil that describe the pyrolysis of peel, seeds and peel and seeds residues.
V. Mangut, E. Sabio, J. Ganan, J.F. Gonzalez, A. Ramiro, C.M. Gonzalez, S. Roman, A. Al-Kassir, Fuel Processing Technology 87 (2006) 109 - 115

A0799 – New chemical route based on sol-gel process for the synthesis of oxyapatite La9.33Si6O26

The aim of this paper is to advance in the field of the development of low-cost synthesis techniques easy to transfer at an industrial scale for electrolyte functional materials in intermediate temperature solid oxide fuel cells (IT-SOFC). We developed an original sol-gel route to synthesize La9.33Si6O26 oxides. This approach is straightforward, inexpensive, versatile and it produces pure powders with controlled size and morphology. Via sol-gel route, crystallization temperature of such phases are drastically reduced: 800°C in comparison with 1500°C in solid-state conventional routes. The dependance of the nature of the phases was studied by varying several parameters as the hydrolysis rate, the volumetric ratio of catalyst to TEOS and the silicon concentration. All these parameters affect the homogeneity of the gel and thus, the purity of the oxides obtained after heat treatment in air. These oxyapatite materials have particle size of about 100 nm after heat treatment at 1000°C. The use of these powders for ceramic processing allows a decrease of the sintering temperature of more than 200°C.
S. Célérier, C. Laberty, F. Ansart, P. Lenormand, P. Stevens, Ceramics International 32 (2006) 271-276

A0798 – Crystal phase separation and microstructure of a thermally treated vitrified solid waste

The vitrification method was used to stabilize a solid industrial waste residue rich in iron and lead oxides. Upon devitrification of the glass products, the effect of batch composition on the ability to produce glass-ceramic materialswas investigated by electron microscopy techniques. The crystallization and microstructural evolution of the vitreous products was explored with respect to the annealing conditions. In the course of vitrification, ferric oxide functioned as a glass network former, contributing to the structural integrity of the vitreous matrix. After thermal treatment of the vitrified products, at temperatures determined by differential thermal analysis, Pb8Fe2O11, PbFe12O19 and Fe2O3 were the dominant crystal phases detected in the glass-ceramic products, the former characterized as a new structure. The distribution of iron and lead oxides among different crystalline phases was found to be the dominant parameter determining the efficiency of lead captivation into the volume of the devitrified products, whereas in glass products lead is diffused in the amorphous matrix.
Th. Kehagias, Ph. Komninou, P. Kavouras, K. Chrissafis, G. Nouet, Th. Karakostas, Journal of the European Ceramic Society 26 (2006) 1141-1148

A0801 – Influence of the de-waxing atmosphere on the properties of AlN ceramics processed from aqueous media

The influence of binder burnout atmosphere (air or N2) on surface chemistry of thermo-chemically treated AlN powders processed in aqueous media, and on the final properties of AlN ceramics was studied. The surface chemistry after de-waxing was accessed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD), SEM, high-resolution transmission electron microscopy (HR-TEM), were used to identify the phase assemblage and for microstructural analysis. The effects of the residual carbon and oxygen at the surface on the thermal conductivity and sintered density of AlN samples were investigated. The surface C/O ratios were observed to correlate with the sintering behaviour, the composition and distribution of secondary phases, and grain-boundary composition, as well as thermal conductivity of AlN samples. Thermal conductivities of about 140W/mK were obtained for the aqueous processed AlN samples de-waxed in nitrogen atmosphere and sintered for 2 h at 1750°C in the presence of 4 wt.% YF3 + 2 wt.% CaF2 as sintering additives.
S.M. Olhero, P. Miranzo, J.M.F. Ferreira, Journal of the European Ceramic Society 26 (2006) 2475-2483

A0800 – Thermal degradation kinetics of the biodegradable aliphatic polyester, poly(propylene succinate)

The preparation of the biodegradable aliphatic polyester poly(propylene succinate) (PPSu) using 1,3-propanediol and succinic acid is presented. Its synthesis was performed by two-stage melt polycondensation in a glass batch reactor. The polyester was characterized by gel permeation chromatography, 1H NMR spectroscopy and differential scanning calorimetry (DSC). It has a number average molecular weight 6880 g/mol, peak temperature of melting at 44°C for heating rate 20°C/min and glass transition temperature at 36°C. After melt quenching it can be made completely amorphous due to its low crystallization rate. According to thermogravimetric measurements, PPSu shows a very high thermal stability as its major decomposition rate is at 404°C (heating rate 10°C/min). This is very high compared with aliphatic polyesters and can be compared to the decomposition temperature of aromatic polyesters. TG and Differential TG (DTG) thermograms revealed that PPSu degradation takes place in two stages, the first being at low temperatures that corresponds to a very small mass loss of about 7%, the second at elevated temperatures being the main degradation stage. Both stages are attributed to different decomposition mechanisms as is verified from activation energy determined with isoconversional methods of Ozawa, Flyn, Wall and Friedman. The first mechanism that takes place at low temperatures is auto-catalysis with activation energy EZ157 kJ/mol while the second mechanism is a first-order reaction with EZ221 kJ/mol, as calculated by the fitting of experimental measurements.
K. Chrissafis, K.M. Paraskevopoulos, D.N. Bikiaris, Polymer Degradation and Stability 91 (2006) 60-68

A0803 – An investigation of the pyrolysis kinetics of some aliphatic amino acids

The thermal behavior of some aliphatic amino acids, including alanine, valine, leucine, isoleucine, and proline was investigated by thermogravimetry (TG) in the range of temperatures within 30-400°C. Pyrolysis of these amino acids was performed at various heating rates under inert (non-oxidative) conditions. The kinetic analysis was carried out using a composite procedure involving the iso-conversional method and the master plots method. The iso-conversional method indicated that the pyrolysis reaction should conform to single reaction model. The master plots method suggested that the phase boundary reaction models best describe the pyrolysis of alanine, valine, leucine and isoleucine, while the pyrolysis of proline should conform to the simple order reaction model. Also, for each amino acid, the kinetic parameters, such as activation energy and pre-exponential factor, were determined, respectively.
T. Wanjun, W. Cunxin, C. Donghua, J. Anal. Appl. Pyrolysis 75 (2006) 49-53

A0802 – Optimal design and preparation of beta-SiAlON multiphase materials from natural clay

Beta-SiAlON powders have been synthesized using natural clay containing kaolin and quartz by carbothermal reduction and nitridation (CRN), then beta-SiAlON bonded corundum multiphase materials have been sintered using the as prepared powders. The results indicated that both the holding time and sintering temperature are relatively significant in accordance with optimal analysis by orthogonal method. Reaction process can be briefly interpreted by means of X-ray Diffraction and Difference Temperature Analysis as well as phase diagram principle. Bending strength and bulk density were measured in SiAlON in situ bonded corundum materials with doped various sintering agents. Furthermore, the relevant mechanical properties and microstructure were discussed in detail.
L-H. Xu, F. Lian, H. Zhang, Y-B. Bi, K. Cheng, Y-B. Qian, Materials and Design 27 (2006) 595-600

A0804 – The effect of the cobalt loading on the growth of single wall carbon nanotubes by CO disproportionation on Co-MCM-41 catalysts

Highly ordered MCM-41 mesoporous molecular sieves in which silicon was isomorphously substituted with 0.5-4 wt.% cobalt were synthesized using an alkyl template with a 16 carbon atoms alkyl chain length. These materials were used as catalysts for the synthesis of uniform diameter single wall carbon nanotubes (SWNT) by CO disproportionation (Boudouard reaction). The SWNT synthesis conditions were identical for all Co-MCM-41 samples, and consisted of pre-reduction of the Co-MCM-41 catalyst in hydrogen at 500°C for 30 min followed by reaction with pure CO at 800°C and 6 atm for 1 h (conditions previously optimized for 1 wt.% Co-MCM-41). The SWNT grown in the Co-MCM-41 catalysts were characterized by TGA, multi-excitation energy Raman spectroscopy and TEM. The state of the catalyst and the size of the metallic cobalt clusters formed in Co-MCM-41 during the SWNT synthesis were characterized by X-ray absorption spectroscopy. The mechanism controlling the diameter distribution of the SWNT produced is related to the size uniformity of the cobalt clusters nucleated in the Co-MCM-41 catalytic template: the SWNT growth selectivity and size uniformity is influenced by the cobalt concentration in the framework. If the cobalt is not initially strongly stabilized in the MCM-41 framework during template synthesis, the catalyst produces SWNT with a wider diameter distribution. Co-MCM-41 catalysts with up to 3 wt.% cobalt can be used to grow SWNT with a diameter distribution similar to that obtained with 1 wt.% Co-MCM-41, but at yields greater by a factor of approximately 2.4.
Y. Chen, D. Ciuparu, S. Lim, G.L. Haller, L.D. Pfefferle, Carbon 44 (2006) 67-78

A0805 – In situ neutron diffraction analysis of the influence of geometric confinement on crystalline swelling of montmorillonite

The swelling properties of a bentonite MX-80 and a Na montmorillonite obtained from MX-80 purification were analyzed as a function of relative humidity in free and constrained conditions. Gravimetric and XRD techniques were used to study the hydration of powder and compacted pellets in non confined conditions whereas hydration under constrained conditions was investigated in situ by neutron diffraction using a cell specifically designed for the present study. MX-80 bentonite and purified montmorillonite were compacted to an apparent density of 1.7 and equilibrated at various relative humidities using P2O5 and solutions saturated with different salts allowing to work in a wide range of relative humidity between 0 and 0.98. At low relative humidity, the hydration of montmorillonite is similar in free and constrained conditions. For relative pressures higher than 50%, swelling in constrained pellets deviates from that observed for free pellets. Reorientation phenomena of clay layers were also observed for bentonite and montmorillonite starting at 65% RH. At 98% RH, two well-defined basal spacings were obtained in the case of confined bentonite. The major peak corresponds to three-layer hydrates (18.6 Å) and the second one to twolayer hydrates (16 Å). In contrast, only the latter peak is observed when hydration is realized in free geometrical conditions. In the case of Na montmorillonite, for the same relative humidity, the confinement cell did not resist swelling pressure. This was explained by the fact that, for the 1.7 density, porosity was too small to allow the formation of the three layer hydrates to compensate for water swelling pressure.
K. Devineau, I. Bihannic, L. Michot, F. Villiéras, F. Masrouri, O. Cuisinier, G. Fragneto, N. Michau, Applied Clay Science 31 (2006) 76-84

A0806 – Polyhedral oligomeric silsesquioxanes (POSS) thermal degradation

The mechanism of thermal degradation of several substituted polyhedral oligomeric silsesquioxanes (POSS) cages is studied in this work. Hydrogen POSS and methyl POSS shows incomplete sublimation on heating, both in inert atmosphere and in air. Isobutyl and octyl substituted POSS undergo an almost complete evaporation when heated in inert atmosphere. In air, oxidation competes with volatilization, producing a considerable amount of silica-like residue on heating up to 800°C. Phenyl POSS shows a higher thermal stability than saturated aliphatic POSS and limited volatility, producing a ceramic residue at high yield on heating in nitrogen, composed of a silica containing a considerable amount of free-carbon. A lower amount of residue is shown after heating in air, corresponding to the POSS Si-O fraction. A vinyl POSS cage/network resin is also studied, in comparison to above materials, showing the highest ceramic yield.
A. Fina, D. Tabuani, F. Carniato, A. Frache, E. Boccaleri, G. Camin, Thermochimica Acta 440 (2006) 36-42

A0808 – Ceramic formulations prepared with industrial wastes and natural sub-products

This work describes the studies carried out with various industrial wastes and natural sub-products based on the SiO2-Al2O3-CaO system, aimed at producing ceramic products of industrial interest. The physical and chemical characterization of the waste materials is reported and their thermal behaviour is described. Several mixtures were prepared and fired at different temperatures. Compositional evolution was assessed by X-ray diffraction and fluorescence and the sintered samples were characterised in terms of density and mechanical strength. For comparison, similar compositions based on high purity grade commercial reagents were also investigated. The presence of impurities in the former waste materials induces changes on functional properties (e.g. refractoriness). However, those variations are easily predicted and can be accounted for.
F. Raupp-Pereira, D. Hotza, A.M. Segadaes, J.A. Labrincha, Ceramics International 32 (2006) 173-179

A0807 – The application of thermal processes to valorise waste tyre

Scrap tyres are a growing environmental problem because they are not biodegradable and their components cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tyres by pyrolysis and the value of the products obtained have been studied. First, thermobalance experiments were carried out, studying the influence of the following variables: heating rate, flow rate, particle size and temperature. These thermobalance results were extended by performing experiments in a fixed bed reactor, studying the effect of the main process variables on yields of derived products: oils, gases and solid residue. The oils have been characterized using a combination of analytical techniques (TLC-FID, GC-MS and simulated distillation). No relationship between functional group composition of the oils determined by TLC-FID and process variables was found. The carbonaceous material obtained was characterized by N2 and CO2 adsorption. The possible uses of this char have been analyzed taking into account and calculating the emissions that would be produced if the char were burnt.
R. Murillo, E. Aylon, M.V. Navarro, M.S. Callén, A. Aranda, A.M. Mastral, Fuel Processing Technology 87 (2006) 143 - 147

A0809 – Kinetic of mullite formation from a porcelain stoneware body for tiles production

The growth of mullite (3Al2O3.2SiO2) in a porcelain stoneware body for tiles production has been investigated using differential thermal analysis (DTA). The activation energy calculated by both isothermal and non-isothermal treatments is 599 and 622 kJ mol-1, respectively. The growth morphology parameters n and m are both about 1.5 indicating that bulk nucleation is dominant in mullite crystallisation followed by three-dimensional growth of mullite crystals with polyhedron-like morphology controlled by diffusion from a constant number of nuclei. The frequency factor calculated by the isothermal treatment is equal to 8.21x10^(22) s-1.
M. Romero, J. Martin-Marquez, J.Ma. Rincon, Journal of the European Ceramic Society 26 (2006) 1647-1652

A0811 – 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

A0810 – Structure, phase transitions, dielectric and spectroscopic studies of the 2-aminopyrimidinium salts: [(2-NH2C4N2H3)2H][ClO4] and [2-NH2C4N2H4][BF4]

Crystal structure of the 2-aminopyrimidinium derivatives: [(2-NH2C4N2H3)2H][ClO4] (I) and [2-NH2C4N2H4][BF4] (II) has been determined at 100 K (I) and 293 K (II) by means of single crystal X-ray diffraction as monoclinic space group, P2/c and P21/n, respectively. The asymmetric part of the unit cell of (I) contains two symmetry independent 2-aminopyrimidine forming one dimeric cation and one disordered perchlorate anion. The structure of (II) consists of 2-aminopyrimidinium cation, [2-NH2C4N2H4]+, protonated at a pyrimidine ring-N atom and [BF4]- anion. Differential scanning calorimetry (DSC) on perchlorate derivative (1 : 1), [2-NH2C4N2H3][ClO4] (III)-being isomorphic to tetrafluoroborate one (I) at room temperature, reveals two phase transitions of first order: at 250/275 K and 390/410 K (cooling-heating, respectively), whereas the analog (II) only one transition at high temperatures-343/385 K. The dielectric studies in the frequency range 75 kHz - 10 MHz disclose relaxation process at high temperatures in salt (I). Infrared spectra of polycrystalline [2-NH2C4N2H4][BF4] have been studied in the temperature range 300-420 K. Substantial changes in the temperature evolution of frequencies of internal modes of the 2-aminopyrimidinium cations and [BF4]- anions near 390 K are due to the variations in the motion of both moieties and hydrogen bond configuration. The experimental studies indicate that all phase transitions taking place in studied 2-aminopyrimidinium derivatives are classified as an order-disorder.
O. Czupinski, M. Wojtas, Z. Ciunik, R. Jakubas, Solid State Sciences 8 (2006) 86-96

A0813 – Hydroxyapatite nano-powders produced hydrothermally from nacreous material

Nano-powders of pure AB-type carbonated hydroxyapatite (HA) sized of -100 nm were successfully produced via hydrothermal transformation (HT) of milled oyster shell powders at 200°C. Low production cost, worldwide availability and natural-biological origin of raw materials are important features of the investigated process. When fine shell powders were used, the transformation reaction from aragonite to hydroxyapatite was accomplished within about 24 h. Calcite, concentrated at the outer surface of the shells, was less prone to transform into hydroxyapatite under the investigated hydrothermal conditions, even after prolonged reaction time (72 h) or in highly concentrated phosphate solutions.
A.F. Lemos, J.H.G. Rocha, S.S.F. Quaresma, S. Kannan, F.N. Oktar, S. Agathopoulos, J.M.F. Ferreira, Journal of the European Ceramic Society 26 (2006) 3639-3646

A0812 – 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

A0815 – Effect of calcination temperature on morphology of mesoporous YSZ

A nano-structured mesoporous yttria-stabilized zirconia (YSZ) powders were prepared for the first time using cetyltrimethylammonium bromide (CTAB) as the surfactant and urea as the hydrolyzing agent and using ZrO(NO3).6H2O and Y(NO3)3.6H2O as inorganic precursors. The Brunauer-Emmett-Teller (BET) surface area, Barrett-Joyner-Halender (BJH) pore size distribution and crystallite/particle size of mesoporous YSZ varied with calcine temperatures were studied. Characterizations revealed that the mesoporous YSZ powder calcined at 600°C was weakly agglomerated and had a high surface area of 137m2/g with an average grain size of -5.8 nm. It was demonstrated that the mesoporous structure remained up to 900°C. The low-densified YSZ sample with porosity as high as 33% was prepared from mesoporous YSZ powder sintered at 1500°C for 6 h.
I-M. Hung, D-T. Hung, K-Z. Fung, M-H. Hon, Journal of the European Ceramic Society 26 (2006) 2627-2632