L0110 – Iron oxide as an effective sintering aid and a grain boundary scavenger for ceria-based electrolytes
The effect of FeO1.5 addition on the densification behavior and electrical properties of Ce0.8Gd0.2O(2-d) ceramics was examined. The
small addition of FeO1.5 (e.g., 0.5 at.%) reduced sintering temperature (by ~200°C) and promoted densification rate. When sintered at
1300°C for 5 h, the 0.5 at.% FeO1.5-doped Ce0.8Gd0.2O(2-d) has ~95% relative density, as compared to ~82% relative density for the
undoped one. The measurement of lattice parameter indicated that the FeO1.5 addition also promoted the dissolution of Gd2O3 in CeO2 at
lower sintering temperatures. On the other hand, the grain boundary (GB) conductivity could be significantly improved by small addition of
FeO1.5. The optimum scavenging effect on SiO2 impurity was achieved by adding 0.5 at.% FeO1.5 to Ce0.8Gd0.2O(2-d) ceramics and sintered
L0131 – Co-sintering and microstructural characterization of steel/cobalt base alloy bimaterials
The objective of this study is to process a bimaterial that combines the mechanical strength of a martensitic steel (X3CrNiMo13-4) and the wear and corrosion resistance of a cobalt base alloy (Stellite 6). The powder metallurgy route includes three steps: co-compaction, debinding, and pressureless co-sintering. The experimental approach consists in studying the compaction, the
debinding and the sintering behavior of single materials (dimensional changes during sintering, microstructure, and hardness after sintering) before studying co-sintering. The co-sintering temperature range is defined from thermochemical calculations and single material sintering experiments especially for Stellite 6. Finally, the co-sintering ability is evaluated (green and final densities, shrinkage mismatch, coefficient of thermal expansion…) and the bimaterial sintering is studied. Despite the shrinkage mismatch of single materials, cohesion is achieved between
the two materials through the infiltration of the supersolidus liquid from the Co base alloy to the steel and through the formation of an interdiffusion layer between the two materials characterized by a composition gradient.
L0120 – Proton conduction in ceria-doped Ba2In2O5 nanocrystalline ceramic at low temperature
Sintered pellets of Ce-doped Ba2In2O5 (BIC) were prepared from nanopowders. The electrical conductivities were measured using ac impedance spectroscopy under different atmospheres and temperatures. The electrical conductivity of sintered BIC was found sensitive to environmental humidity when the temperature was below 300 ?C. However, in the presence of hydrogen, the electrical conductivities were independent of water content in the range of 0–30 vol%. The electrical conductivities of BIC were significantly affected by the presence of hydrogen in a temperature range of 100–300 ?C. The estimated protonic transference number and the measured open circuit voltage suggested the existence of electronic conduction. The coefficient of thermal expansion of BIC is 11.2×10?6 K?1 from 25 to 1250 ?C.
L0130 – A Phenomenological Analysis of Sintering Mechanisms of W-Cu from the Effect of Copper Content on Densification Kinetics
The effect of addition of copper on the sintering of a W powder was systematically investigated by the analysis of dilatometric experiments on W and W-Cu compacts prepared with submi-
crometric powders. A pure W powder compact and a W-10 wt pct Cu powder compact with the same packing fraction ofWparticles were first studied, in order to analyze the effect of copper at
fixed microstructure of the solid W particle packing. A more systematic set of experiments with different copper contents and W particle sizes was also qualitatively analyzed. A phenomeno-
logical model of sintering was developed and fitted in order to extrapolate the effect of copper content on sintering kinetics at fixed microstructure of the W particle skeleton. An interpreta-
tion of the sintering mechanisms was then proposed. Sintering of a W-Cu powder compact is the result of solid-state sintering of the W skeleton, enhanced by the capillary forces exerted by
copper, with the superimposition of a particle rearrangement step after copper melting.
L0119 – Thermal cycling behaviour of stir cast Al–Mg alloy reinforced with fly ash
The thermal cycling behaviour of stir cast Al–Mg alloy A535 composites reinforced with various amounts of fly ash was investigated in this study. The test samples were subjected to 10 thermal cycles between 40 and 300 ?C in a Seteram Setsys Evolution Thermomechanical Analyser (TMA). The results show that strain hysteresis loops developed during thermal cycling. The hysteresis and residual plastic strains induced in the alloy during thermal cycling decreased with the addition of fly ash. Also, the incorporation of fly ash in A535 improved its dimensional stability
L0129 – Some studies on the phase formation and kinetics in TiO2 containing lithium aluminum silicate glasses nucleated by P2O5
Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O–71.7SiO2–7.1Al2O3–4.9K2O–3.2B2O3–1.25P2O5–1.25TiO2 were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li2SiO3 is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.
L0118 – Use of TMA to predict deposition behaviour of biomass fuels
Deposits formation on boiler heat transfer surfaces is one of the main operational problems associated to biomass co-combustion. This paper proposes a novel method to rank deposition propensity of biomass fuels. The method combines thermo-mechanical analysis (TMA) with ash leaching procedures and is applied here to a set of biomass fuels. Based on the TMA penetration and shrinkage traces obtained for the original and the leached ashes, the fuels are classified regarding their deposition tendencies. The results have been successfully
validated with chemical analysis of the liquid fraction from ash leaching. Initial results for the behaviour of coal–biomass mixtures are also presented
L0139 – Conductivity and expansion at high temperature in Sr0.7La0.3TiO(3??) prepared under reducing atmosphere
Sr0.7La0.3TiO(3??) specimens were prepared in reducing atmosphere, and the structural and electrical properties were studied. The lattice parameter of Sr0.7La0.3TiO(3??) at room temperature was larger than that expected from Vegard’s law between SrTiO3 and LaTiO3 due to the reductive expansion. The conductivity of this specimen was 100 S cm?1 at 1000°C, pO2 = 10?13 Pa. However, the conductivity was not preserved after an oxidation-reduction cycle. Over pO2 = 102 Pa, the conductivity drastically dropped th increasing pO2 . The thermal expansion coefficient of Sr0.7La0.3TiO(3??) was 11.8 × 10?6 K?1 in 9% H2/N2 (room temperature – 1000?C). In this Sr0.7La0.3TiO(3??), the chemical expansion on oxidation reached 1l/lo = 0.51%, when changing pO2 from 10?11 Pa to 2 × 104 Pa (air) at 1000°C.
L0128 – Preparation and studies of some thermal, mechanical and optical properties of xAl2O3(1 – x)NaPO3 glass system
Sodium aluminophosphate glasses having compositions of xAl2O3(1 – x)NaPO3 (x = 0×05–0×2) were prepared using conventional melt-quench technique. Density, glass transition temperature, microhardness (MH), thermal expansion coefficient (TEC) and transmission characteristics were measured as a function of alumina content for different samples. They were found to depend on O/P ratio with pronounced changes taking place for O/P ratio ³ 3×5. Density, glass transition temperature and microhardness were found to increase up to 15 mol% of alumina and then they showed a decreasing trend. Thermal expansion coefficient decreased continuously with alumina content. Optical gaps for different glass samples as measured from
transmission characteristics were found to be in the range 3×13–3×51 eV. It initially decreased with alumina content up to 15 mol% and then increased. The behaviour was explained on the basis of change in the average aluminum coordination number from six Al(6) to four Al(4) (i.e. Al(OP)6/Al(OP)4 ratio) along with the changes in polyhedra linkages in the glass network due to change in O/P ratio.
L0117 – High temperature properties of SiC and diamond CVD-monofilaments
The chemical, structural and thermomechanical properties of SiC and diamond CVD-monofilaments have been investigated. Electron and Raman microprobe analyses showed graded radial atomic and phase distributions in the SiC filaments. Thermomechanical investigations (tensile/bending elastic modulus/creep tests) were carried out on single filaments and these properties were correlated with the physicochemical features. The thermal behaviour of the CVD-SiC filaments is strongly related to the nature and the amounts of intergranular secondary phases
(free carbon or silicon). The strong covalent bonds and the microcrystalline state of the CVD-diamond filaments give rise to an outstanding thermal behaviour.
L0138 – Thermal Properties of Maleated Polyethylene/Layered Silicate Nanocomposites
Nanocomposites are a new class of composites in which the reinforcing phase dimensions are on the order of nanometer scale. In particular, the layered silicates are considered to be good candidates for the preparation of polymerinorganic nanocomposites. The mechanical and thermal properties of polymer can be altered by adding a few vol% of the nano-particles. The effect of the nano-sized particles on thermophysical properties such as melting and crystallization, coefficient of thermal expansion, and thermal conductivity was studied. After preparing the PEMA/layered silicate nanocomposites, the thermophysical properties were investigated by the differential scanning calorimetry and 3? methods. The content of layered silicate was varied from 0.5 to 5 vol%.
L0127 – Influence of synthesis route on morphology and conduction behavior of BaCe0.8Y0.2O32?
In this article, the role of the preparation route and calcinations temperature on the thermal expansion and conductivity of BaCe0.8Y0.2O3-d (BCY) has been studied. In particular, the samples were synthesized by means of the solid-state reaction and by a sol–gel route. BCY has been suggested as proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Proton conductivity strongly depends on the densification of the material as well as the crystal structure, which is generally influenced by the preparation procedure. It was found that a single phase material could be achieved at 1000 C for the samples prepared through the sol–gel route with *96% packing density. In case of ceramic route, single phase could be obtained at higher temperatures (1200 C) and does not lead to good density values. The ceramic synthesis produces BCY material in cubic symmetry where as the gel–citrate complexation route leads to homogenous orthorhombic BCY. The conductivity measurements of sample synthesized by two different routes were investigated by means of impedance spectroscopy and electron
microscopy. A comparative study of thermal expansion behavior of BCY synthesized by different route was carried out.
L0116 – MgTiO3 for Cu base metal multilayer ceramic capacitors
The evolution of the cost of palladium justifies studies devoted to the use of cheap base metals as electrodes for multilayer
ceramic capacitors. In a precedent [J. Eur. Ceram. Soc.10-11(2001) 1681] work we investigated on Mn acceptor together with W
donor additions on the properties of MgTiO3 ceramics sintered at 1350°C under a reducing atmosphere (wet N2-1%H2). As in
acceptor/donor [Proceedings K1; 1206 CIMTEF, Florence (1998) 88] codoped BaTiO3 the insulating character of MgTiO3 was
conserved. In order to employ these materials in the production of type-I multilayer ceramic capacitors with Copper inner electrodes
we investigate now on the possibility of sintering magnesium titanate at low temperature. We have studied the densification
behavior of different MgTiO3 compositions with lithium salts additions, considering particularly the effect of the non-stoechiometry
expressed as the Mg/Ti ratio. Full densification appears below 1000°C. The obtained ceramics, that have been co-sintered in a
multilayer structure with Cu electrodes, are characterised by a resistivity higher than 10^(13) ohm cm together with a NPO dielectric
constant ranging from 14 to 16 depending on the exact composition together with losses lower than 0.2%.
L0137 – Thermal Expansion of Simulated Fuels with Dissolved Fission Products in a UO2 Matrix
As a part of the DUPIC (direct use of spent PWR fuel in CANDU reactors) fuel development program, the thermal expansion of simulated spent fuel pellets with dissolved fission products has been studied by using a thermo-mechanical analyzer (TMA) in the temperature range from 298K to 1773K to investigate the effects of fission products forming solid solutions in a UO2 matrix on the thermal expansions. Simulated fuels with an equivalent burn-up of (30 to 120) GWd/tU were used in this study. The linear thermal expansions of the simulated fuel pellets were higher
than that of UO2, and the difference between these fuel pellets and UO2 increased monotonically with temperature. For the temperature range from 298K to 1773K, the values of the average linear thermal expansion coefficients for UO2 and simulated fuels with an equivalent burn-up of (30, 60, and 120) GWd/tU are 1.19 × 10?5 K?1, 1.22 × 10?5 K?1, 1.26 × 10?5 K?1, and 1.32 × 10?5 K?1, respectively.
L0126 – Dilatometric analysis on shrinkage behavior during nonisothermal sintering of nanocrystalline tungsten mechanically alloyed with molybdenum
The paper attempts to study the shrinkage behavior of nanocrystalline tungsten mechanically alloyed with molybdenum (5, 10, 15 and 20 wt.%). The dilatometric analysis was performed by Setsys Evolution TMA (ambient to 1600 ?C) using constant heating rate (CHR) method. The significant improvement in shrinkage with alloying of molybdenum is attributed to reduced grain size, lowered tungsten carbide contamination and enhanced diffusion kinetics. The initial stage sintering kinetics of W–20Mo alloy has been investigated. The densification starts with Mo diffusion (calculated activation energy = 128 kJ/mol) and proceeds with the diffusion of both along the grain boundaries (calculated activation energy = 307 ± 1 kJ/mol).
L0115 – Lowering of BaB’1/3B”2/3O3 complex perovskite sintering temperature by lithium salt additions
Complex perovskite materials with the formula BaB'1/3B"2/3O3 have been broadly studied for their attractive dielectric properties.
These materials exhibit a high relative dielectric constant and a very low dissipation factor. For example, the BaMg1/3Ta2/3O3
material has a relative dielectric constant close to 26 with a dissipation factor lower than 10^(-4) at 1 MHz. These properties are very
promising for applications such as hyper-frequency resonators or/and capacitors. Unfortunately, a high temperature is necessary to
achieve a satisfying densification of this materials family (>1400°C) whereas the lowering of this temperature is more and more
crucial from the industrial point of view. In particular, the development of Base Metal Electrodes Multi-Layer Ceramic Capacitors
(BME-MLCC) requires the sintering of dielectric materials at low temperatures (<1100°C). The aim of the study is thus to lower
the sintering temperature of these materials. For this goal, lithium salts (Li2CO3, LiF, BaLiF3 and LiNO3) have been tested as
sintering agents to densify BaZn1/3Ta2/3O3, BaMg1/3Ta2/3O3 and BaZn1/3Nb2/3O3 materials. It is shown, for example, that the
BaMg1/3Ta2/3O3 sintering temperature is lowered by 300°C when 15 mol % of lithium nitrate is added without affecting the
dielectric properties at 1 MHz. For the best sintering agents investigated and each studied materials, the ceramic is characterised in
terms of final density, microstructure and dielectric properties and densification mechanisms are discussed.
L0136 – Zirconia-MWCNT nanocomposites for biomedical applications obtained by colloidal processing
Zirconia ceramics are widely used as femoral heads, but case studies show that delayed failure can occur in vivo due to crack propagation. The addition of carbon nanotubes (CNT) is aimed to avoid the slow crack propagation and to enhance the toughness of the ceramic material used for prostheses. However, to really enhance the mechanical properties of the material it is necessary to achieve a uniform distribution of the CNT in the zirconia matrix. Colloidal processing has demonstrated to be suitable for obtaining ceramic-based composites with homogeneous distribution of the phases and high green density.This work compares the colloidal behavior of the as-received multi wall carbon nanotubes (ar-MWCNT) and the partially coated MWCNT (pc-MWCNT) when immersed in a nanozirconia matrix. With pc-MWCNT an improvement in the dispersion is proved. Moreover, the sintered samples that contain pc-MWCNT show higher
density, lower grain size, improved toughness and enhanced hardness under the same sintering cycle when compared to the samples with ar-MWCNT.
L0125 – Sintering kinetics study of mechanically alloyed nanocrystalline Mo- 30 wt % W
The paper details the results of sintering kinetics studies conducted on nanocrystalline Mo- 30 wt % W alloy powders using both conventional sintering method as well as stepwise isothermal dilatometry technique.
L0114 – CaZrO3, a Ni-co-sinterable dielectric material for base metal-multilayer ceramic capacitor applications
The aim of this work is to obtain CaZrO3 powders that are co-sinterable with nickel electrodes. Since CaZrO3 is often sintered at
temperatures higher than 1550°C to achieve high sample densities, obtaining a powder co-sinterable with Ni would require lower
sinteringtemperatures. The co-sintering also requires that the reaction takes place in a reducing atmosphere. After optimizingthe
thermal cycle for the phase synthesis, several approaches were investigated to decrease the CaZrO3 sinteringtemperature. First, the
grain size effect on the densification was studied to enhance the calcined powder's reactivity before sintering. In addition, the Ca/Zr
ratio was investigated, and the effect of doping with lithium salts was examined. Similarly, in order to allow co-sintering with basemetal
inner electrodes, the sinterability and the properties of the dielectric were examined in a reducingatmosphere. Finally, a cosintered
material was synthesized, resultingin good dielectric properties. The samples were analyzed in terms of structure and
microstructure. The electric and dielectric properties were also measured on sintered samples.
L0135 – Effects of Glass Phase Additions and Stoichiometry on the Ba(Zn1/3X2/3)O3 (X = Ta or Nb) Sinterability and Dielectric Properties
Ba(Zn1/3X2/3)O3 materials where X = Ta or Nb (respectively named BZT and BZN) exhibit attractive properties suitable for applications in type I Multi Layer Ceramics Capacitors (MLCC). Nevertheless, to produce such components using Base Metal Electrodes such as copper, a significant reduction of their sintering temperature is required. The aim of this work is first to study the effects of glass phases additions and secondly the stoichiometry influence on the sintering temperature of BZT and BZN. It is shown for example, that our materials can be sintered
in air at a temperature lowered by 450?C when sintering agents (B2O3 with LiF) are combined with a slight non-stoichiometry. The sintered samples are characterised in terms of final density, microstructure and phase content and it was underlined that such modifications (additions and stoichiometry) does not affect the dielectric properties.
L0124 – Sintering kinetics of submicron sized coblat powders
The paper details the results of sintering kinetics studies on submicron sized fine cobalt metal powder prepared through oxalate decomposition route using both conventional sintering method as well as stepwise isothermal dilatometry technique.
L0113 – Thermal and mechanical properties of cordierite, mullite and steatite produced by plasma spraying
Cordierite, mullite and steatite are silicate materials widely used in the ceramics industry. There is, however, only sparse information on
their application in plasma spraying and properties of sprayed materials. Plasma sprayed deposits of cordierite, mullite and steatite contain
amorphous phases as the result of rapid cooling of molten particles. The amorphous phase has a significant influence on physical properties,
especially in connection with heat treatment.
This article deals with phase changes of cordierite, mullite and steatite, resulting from plasma deposition. Special attention is paid to
amorphous phase crystallization in subsequent heat treatment.
Plasma sprayed deposits were produced using a water stabilized plasma torch WSP®. The processes taking place in the deposits were
examined primarily by differential thermal analysis (DTA), thermal dilatometry (TMA) and X-ray diffraction (XRD). These measurements
were complemented by the determination of physical properties (namely, density, Young's modulus and strength) and morphological observations.
Important thermal characteristics like crystallization temperature and the coefficient of thermal expansion (CTE) of all materials were
L0134 – Synthesis of Hafnia Powders and Nanofiltration Membranes by Sol-Gel Process
Hafnia nanofiltration membranes were prepared by sol-gel process from hafnium 1-methoxy-2 propoxide via colloidal route. This original molecular precursor has been synthesized and characterized by 1H NMR, mass spectroscopy, infrared and elemental analysis. Its peptization revealed to be the most efficient method to provide a highly reactive powder at a low sintering temperature. The porous volume variation and the pore diameter distribution of the hafnia powder have been studied as a function of the sintering temperature and the TGA, DTA and dilatometry study are reported. The membrane sintered at 450?C exhibited a defect-free texture with a cut-off equal to 420 Daltons and pore diameters equal to 1.9 nanometers.
L0123 – A Novel tool for assessing slagging propensity of coals in PF boilers
Over the years, wide ranges of testing and evaluating procedures have been developed to predict plant performance. Some of the conventional test results and empirical ratios generated out of it offer poorer predictive capability for slagging behaviour experienced in power plants. For better understanding of the coal properties related to slagging problems, a new coal characterization index based on thermo-mechanical analysis (TMA) has been developed in Research and Development Laboratory, BHEL, Tiruchirapalli. A new sampling set up has been designed to carry out shrinkage measurements using TMA. Coal samples collected from various Indian power plants are evaluated. The shrinkage profile of the ash specimen was recorded and characteristic data from the profile were taken for further calculations. Based on proximate analysis, calorific value of the fuels and the shrinkage data of the ash, a new slagging propensity index was proposed. The new index offers better correlation with field observation and hence the new index proposed, offer better predictive capability for understanding the field slagging observations than the conventional indices. The new empirical index can be used as guidelines for relative assessment of coals with respect to slagging, while designing the boiler and tuning the operational parameters.
L0112 – Nanosized alumina from boehmite additions in alumina porcelain 1. Effect on reactivity and mullitisation
The influence of nanosized alumina additions and of grain size of alumina filler on the reaction-sintering of alumina porcelain is investigated.
Phase and porosity evolution has been studied from room temperature up to 1400°C. When vitrification occurs the presence of alumina
nanoparticles leads to a new type of mullitisation which has two major consequences: a volume expansion resulting in a shrinkage inhibition
and a decrease of the amount of liquid which causes densification problems at usual firing temperatures. This phenomenon is enhanced if the
alumina filler is coarse but it is limited when fine and round alumina is used because in that last case vitrification kinetics is slowed down.
L0133 – Anisotropic kinetic of the kaolinite to mullite reaction sequence in multilayer ceramics
Multilayer ceramics with a composite and organized microstructure were realized from kaolin and alumina fibers to improve strength and fracture toughness. Dilatometry experiments along 3 directions reveal anisotropic shrinkages, which are in correlation with different activation energy for sintering. Mullite growth is strongly anisotropic, inducing the formation of an organized microstructure, where larger mullite crystals are mainly oriented in plane of layer and perpendicular to alumina fibers. Kinetic data from thermal transformations show that the starting reaction mechanism is mullite nucleation, and it is continued by a strongly anisotropic grain growth. It is explained by topotactic transformations at phyllosilicate faces and along alumina arrangements. Mullite growth kinetics is also favored perpendicularly to fiber main dimension by the anisotropy of alumina diffusion coefficient. It shows the limited importance of mullite crystallization in microstructural transformation, but it also shows that controlled mullite growth is central in microstructural arrangement.
L0122 – Sintering studies on Ni–Cu–YSZ SOFC anode cermet processed by mechanical alloying
New 40 vol%[(Cu)–Ni]–YSZ cermet materials processed by mechanical alloying (MA) of the row powders are prepared. The powder compacts are sintered in air, hydrogen and inert (argon) atmospheres at a dilatometer and tubular furnace up to 1,350 °C. Sintering by activated surface concept (SAS) can anticipate and enhance the densification in such powders. Stepwise isothermal dilatometry (SID) sintering kinetics study is performed allowing determining kinetic parameters for Ni–YSZ and Ni–Cu–YSZ pellets. Two-steps sintering processes is indicated
while Cu-bearing material features the smallest activation energy for sintering. The allied MA–SAS method is a promising route to prepare SOFC fuel cell anode materials.
L0111 – Effect of milling on the damping behavior of nano-structured copper
In the present study, elemental Cu powder was mechanically milled (MMed) for 10 h to reduce the grain (crystalline) size in the nano-range
(<100 nm). The mechanically milled powder (10 h-MMed) and elemental powder without mechanical milling (MM) (0 h-MMed) was consolidated
by die-cold compaction and were further hot extruded at different temperatures to maintain a crystallite size within the nano-range.
Further, the specimen was tested by a novel free-free type suspended beam arrangement, coupled with circle-fit approach to determine damping
characteristics. The characterization results help to understand the effect of the nano-size grains on the overall damping capacity of the
bulk samples compared to a normal micro-crystalline sample. Results show that the damping capacity of the nano-grained material increases
due to the presence of process induced microstructural changes similar to the damping behavior of a micro-grain sized specimen.
L0164 – Anode-supported microtubular cells fabricated with gadolinia-doped ceria nanopowders
Anode-supported microtubular SOFCs based on ceria 3 ± 0.2 mm diameter and about 100 mm in length have been prepared using gadolinia-doped ceria (GDC) nanopowders. Nanometric Ce0.9Gd0.1O1.95 (GDC) powders were deposited on NiO–Ce0.9Gd0.1O1.95 (NiO–GDC) anode supports by dip-coating technique. Fabrication conditions to obtain dense and gas tight electrolyte layers on porous microtubular supports were studied. Three different dispersing agents: commercial Beycostat C213 (CECA, France) and short chain monomer (?4 carbon atoms) with alcohol or carboxylic acid functional groups were evaluated. By optimizing colloidal dispersion parameters and sintering process, gas tight and dense GDC layers were obtained. Significantly lower sintering temperatures than reported previously (?1300 °C) were employed to reach ?98% values of theoretical density within electrolyte layers of ?10 ?m in thickness. A composite cathode, LSCF–GDC 50 wt.% with about 50 ?m thickness was dip coated on the co-fired half-cell and then sintered at 1050 °C for 1 h. The electrochemical performance of these cells has been tested. In spite of electronic conduction due to partial reduction of the thin-electrolyte layer, the I–V measurements show power densities of 66 mW cm?2 at 0.45 V at temperatures as low as 450 °C (using 100% H2 as fuel in the anodic compartment and air in the cathodic chamber).
L0153 – Combining in situ HT-ESEM observations and dilatometry: An original and fast way to the sintering map of ThO2
The sintering of ThO2 pellets prepared from the initial precipitation of thorium oxalate was investigated by the means of HT-ESEM observations and dilatometric measurements. On the one hand, the use of environmental microscope allowed the in situ observation of the pellet behaviour during heat treatments between 1250 °C and 1400 °C. Subsequent image analysis led to the determination of local (i.e. at the grain scale) and global (i.e. at the pellet scale) kinetic parameters. Particularly, the average grain size was plotted versus the holding time for the three considered temperatures. On the other hand, analogous experiments were performed by dilatometry and led to monitor both linear shrinkage and density of the samples. On this basis, the combination of the two sets of data allowed us to establish for the first time a sintering map for ThO2. This latter clearly evidenced two different zones driven by densification (d ? 92%) then by grain growth (d ? 92%) which can be used efficiently to monitor the final microstructure of sintered thorium oxide.
L0142 – Sintering of tricalcium phosphate–fluorapatite composites with zirconia
Zirconia (ZrO2) addition effects on densification and microstructure of tricalcium phosphate–26.52 wt% fluorapatite composites were investigated, using X-ray diffraction, scanning electron microscopy and by analysis using 31P nuclear magnetic resonance. The tricalcium phosphate–26.52 wt% fluorapatite–zirconia composites densification increases versus temperature. At 1300 ?C, the composites apparent porosity reaches 9% with 5 wt% zirconia. XRD analysis of the composites reveals the presence of tricalcium phosphate, fluorapatite and zirconia without any other structures. Above 1300 ?C, the densification was hindered by grain growth and the formation of both intragranular porosity and new compounds. The 31P MAS-NMR analysis of composites sintered at various temperatures or with different percentages of zirconia reveals the presence of tetrahedral P sites. At 1400 ?C, XRD analysis of the tricalcium phosphate–26.52 wt% fluorapatite–20 wt% zirconia composites shows the presence of calcium zirconate and tetracalcium phosphate. This result indicated that partial decomposition of tricalcium phosphate during sintering process of composites when 20 wt% or less ZrO2 was added. Thus, zirconia reacts with tricalcium phosphate forming calcium zirconate and tetracalcium phosphate
L0163 – Densification and grain growth of 8YSZ containing NiO
The effects of NiO addition on sintering yttria-stabilized zirconia were systematically studied to understand the role of the additive in the sintering process of the solid electrolyte. Specimens of 8 mol% yttria-stabilized zirconia with NiO contents up to 5.0 mol% were prepared using different Ni precursors and sintered at several dwell temperatures and holding times. Densification and microstructural features were studied by apparent density measurements and scanning electron microscopy observations, respectively. The sintering dynamic study was carried out by following the linear shrinkage of powder compacts containing 0–0.75 mol% NiO. Small (up to 1.0 mol%) NiO addition was found to improve the sinterability of yttria-stabilized zirconia. The activation energy for volume diffusion decreases with increasing NiO content, whereas the grain boundary diffusion seems to be independent on this additive. The grain growth of yttria-stabilized zirconia is found to be enhanced even for small NiO contents.
L0152 – Enhancing Physical and Mechanical Properties of Mg Using Nanosized Al2O3 Particulates as Reinforcement
A magnesium-based composite with 1.1 volume percentage of nanosized Al2O3 particulates reinforcement was fabricated using an innovative disintegrated melt deposition technique followed by hot extrusion. Al2O3 particulates with an equivalent size of 50 nm were used as reinforcement. Microstructural characterization of the materials revealed grain refinement of magnesium matrix due to incorporation, retention, and uniform distribution of reinforcement. Physical properties characterization revealed that the addition of nano-Al2O3 particulates as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterization revealed that the presence of nanoAl2O3 particulates as reinforcement leads to a significant increase in microhardness, dynamic elastic modulus, 0.2 pct yield strength (YS), ultimate tensile strength (UTS), and ductility of pure magnesium. The results revealed that the combined
tensile properties of these materials are superior when compared to Mg reinforced with much higher volume percentage of SiC. An attempt is made in the present study to correlate the effect of nano-Al2O3 particulates as reinforcement with the microstructural, physical, and mechanical properties of magnesium.
L0141 – Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate
Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by Xray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using 31P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistance of tricalcium phosphate–33.16 wt% fluorapatite composites reached its maximum value (13.7 MPa) at 1400°C, whereas the optimum densification was obtained at 1350°C (93.2%). Above 1400°C, the densification and mechanical properties were hindered by the tricalcium phosphate allotropic transformation and the formation of both intragranular porosity and cracks. The 31P magic angle spinning nuclear magnetic resonance analysis of composites as sintered at various temperatures or with different percentages of fluorapatite reveals the presence of tetrahedral P sites.
L0162 – Application of LIBS and TMA for the determination of combustion predictive indices of coals and coal blends
Presented work brings results of Laser-Induced Breakdown Spectroscopy (LIBS) and Thermo-Mechanical Analysis (TMA) of coals and coal blends used in coal fired power plants all over Spain. Several coal specimens, its blends and corresponding laboratory ash were analyzed by mentioned techniques and results were compared to standard laboratory methods. The indices of slagging, which predict the tendency of coal ash deposition on the boiler walls, were determined by means of standard chemical analysis, LIBS and TMA. The optimal coal suitable to be blended with the problematic national lignite coal was suggested in order to diminish the slagging problems.
Used techniques were evaluated based on the precision, acquisition time, extension and quality of information they could provide. Finally, the applicability of LIBS and TMA to the successful calculation of slagging indices is discussed and their substitution of time-consuming and instrumentally difficult standard methods is considered.
L0151 – Microstructure and Thermal Behavior of Thermal Barrier Coatings
Yttria stabilized zirconia thick coatings were thermally sprayed from two different feedstock powders. Coating characteristics such as density, crystalline phase composition, and microstructure were evaluated. The thermal expansion coefficient and thermal diffusivity were measured as a function of temperature up to 800 °C and analyzed in terms of the microstructural features. The ability of available models to relate the measured thermal properties to the microstructural features as characterized by readily available methods was assessed. The importance of pore shape and orientation on the thermal conductivity was evidenced. The thermal contact resistance between the substrate and the coating in these samples was estimated from the thermal diffusivity data, and found to change during cooling from 800 °C.
L0140 – Sintering and mechanical properties of tricalcium phosphate–fluorapatite composites
Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic ceramics composites. The effect of fluorapatite addition on the densification and the mechanical properties of tricalcium phosphate were measured with the change in composition and microstructure of the bioceramic. The Brazilian test was used to measure the mechanical resistance of the tricalcium phosphate–26.52 wt% fluorapatite composites. The densification and rupture strength increase versus sintering temperature. The composites have a good sinterability and rupture strength in temperature ranging between 1300 and 1400 8C. Thus, the densification ultimate was obtained at 1350 8C and the mechanical resistance optimum reached 9.6 MPa at 1400 8C. Above 1400 8C, the densification and the mechanical properties were hindered by the allotropic transformation of tricalcium phosphate, grain growth and the formation of both intragranular porosity and many cracks. The 31P magic angle spinning nuclear magnetic resonance analysis of composites reveals the presence of tetrahedral P sites.
L0161 – Densification behaviour and sintering kinetics of ThO2–4%UO2 pellet
ThO2–?4% 233UO2 fuel will be the driver fuel for the forthcoming Advanced Heavy Water Reactor (AHWR) in India. Densification behaviour such as shrinkage and shrinkage rates of the green pellets of ThO2–4wt.% UO2 (natural ‘U’) fabricated by Coated Agglomerate Pelletization (CAP) process were studied using a vertical dilatometer at different heating rates. Activation energy of sintering, ‘Q’, was estimated in the initial stages of sintering by continuous rate of heating (CRH) technique as proposed by ‘Wang and Rishi Raj’ and ‘Young and Cutler’. The sintering mechanism was identified to be as the grain boundary diffusion (GBD) and the average ‘Q’ value obtained by these two methods were found to be 350 ± 16 kJ/mole and 358 ± 5 kJ/mole, respectively.
L0150 – Interfacial investigation of the Co-fired NiCuZn Ferrite/PMN composite prepared by tape casting
The co-firing behavior and interfacial diffusion of the co-fired system of NiCuZn ferrite (abbreviated as NiCuZn) and Pb(Mg1/3Nb2/3)O3 (abbreviated as PMN) relaxor ferroelectric are studied in this work. NiCuZn layers and PMN layers prepared by tape casting were stocked alternately. X-ray diffraction analysis shows no new phase appeared in the mixture of NiCuZn and PMN.
Scanning electronic microscopy observation of the bi-layer composite indicates obvious warp at the interface due to the sintering mismatch between ferrite and ferroelectrics. The co-firing property of NiCuZn and PMN is modified by doping appropriate content of Bi2O3. By pressing a mixed composition interlayer in the ratio 50:50 between the ferrite and ferroelectric layers, a crack-free multilayer structure could be obtained.
L0171 – Phase transformation kinetics of 3 mol% yttria partially stabilized zirconia (3Y-PSZ) nanopowders prepared by a non-isothermal process
A crystalline nanopowder of 3 mol% yttria-partially stabilized zirconia (3Y-PSZ) has been synthesized using ZrOCl2 and Y(NO3)3 as raw materials throughout a co-precipitation process in an alcohol–water solution. The phase transformation kinetics of the 3Y-PSZ freeze dried precursor powders have been investigated by nonisothermal methods. Differential thermal and thermogravimetric analyses (DTA/TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) have been utilized to characterize the 3Y-PSZ nanocrystallites. When the 3Y-PSZ freeze dried powders are calcined in the range of 703–1073 K for 2 h, the crystal structure is composed of tetragonal and monoclinic ZrO2. The BET specific surface area of the 3Y-PSZ freeze dried precursor powders calcined at 703 K for 2 h is 118.42 m2/g, which is equivalent to a crystallite size of 8.14 nm. The activation energy from tetragonal ZrO2 converted to monoclinic ZrO2 in the 3Y-PSZ freeze dried precursor powders was determined as 401.89 kJ/mol. The tetragonal (T) and monoclinic (M) ZrO2 phases coexist with a spherical morphology, and based on TEM examination have a size distribution between 10 and 20 nm. When sintering green compacts of the 3Y-PSZ, a significant linear shrinkage of 8% is observed at about 1283 K. On sintering the densification cycle is complete at approximately 1623 K when a total shrinkage of 32% is observed and a final density above 99% of theoretical was achieved.
L0160 – Development of new magnesium based alloys and their nanocomposites
In the present study, 1 and 2 wt.% of aluminum were successfully incorporated into magnesium based AZ31 alloy to develop new AZ41 and AZ51 alloys using the technique of disintegrated melt deposition. AZ41–Al2O3 and AZ51–Al2O3 nanocomposites were also successfully synthesized through the simultaneous addition of aluminum (1 and 2 wt.%, respectively) and 1.5 vol.% nano-sized alumina into AZ31 magnesium following same route. Alloy and composite samples were then subsequently hot extruded at 400 °C and characterized. Microstructural characterization studies revealed equiaxed grain structure, reasonably uniform distribution of particulate and intermetallics in the matrix and minimal porosity. Physical properties characterization revealed that addition of both aluminum and nano-sized alumina reduced the coefficient of thermal expansion of monolithic AZ31. The presence of both Al and nano-sized Al2O3 particles also assisted in improving overall mechanical properties including microhardness, engineering and specific tensile strengths, ductility and work of fracture. The results suggest that these alloys and nanocomposites have significant potential in diverse engineering applications when compared to magnesium AZ31 alloy
L0149 – Synthesis, characterization, and sintering of sol±gel derived cordierite ceramics for high-frequency MLCIs
The synthesis, characterization, and sintering of sol±gel derived cordierite ceramics are investigated in the present paper. Synthesis was carried out by optimizing two main preparation parameters. The effect of the heat-treatment schedule on crystallization and the properties of crystalline phases were analyzed. The additives B2O3 and P2O5 were utilized to promote the crystallization or transformation to ?-cordierite and sintering. This material has a low dielectric constant and a low dissipation factor and can be co-fired with high conductivity metals such as Au, Ag/Pd, Cu paste at low temperature (below 1000°C), suggesting that it would be a promising material for high-frequency MLCIs.
L0170 – Magnetic and dielectric properties of Ba12Fe28Ti15O84 layered ferrite ceramics
In this study we report for the first time the magnetic and dielectric properties of the quaternary layered ferrite Ba12Fe28Ti15O84. Dense ferrite ceramics were prepared by conventional sintering using powders obtained by solid-state reaction and by coprecipitation. Only the latter powder resulted in nearly single phase ceramics, whereas larger amounts of secondary phases were observed in the material obtained by the solid-state route. According to the HRTEM investigation, the ferrite lattice is originated by the intergrowth of perovskite-like and spinel-like slabs and can be considered as a natural magnetic superlattice. A ferrimagnetic order with saturation magnetization of ?12.5?A?m2?kg?1 and coercivity of ~1590?A?m?1 (~20?Oe) is proposed at room temperature. The thermomagnetic data indicate a Curie temperature of ~420?K for the quaternary ferrite. An additional magnetic transition was detected at ~700?K and ascribed to a secondary magnetic phase, probably the solid solution of TiO2 in BaFe12O19. An intrinsic relative dielectric constant of the order of 23–50 at room temperature was measured at 109?Hz. At lower frequency the dielectric behaviour is dominated by extrinsic effects related to the heterogeneous electrical nature of the ceramics corresponding to semiconducting grains separated by more insulating grain boundary regions. The dielectric losses are rather high, often >1, indicating an overall semiconducting character of the material.
L0159 – Viscosity of Ba–B–Si–Al–O glass measured by indentation creep test at operating temperature of IT-SOFC
Viscosity of a specific Ba–B–Si–Al–O glass used for intermediate-temperature solid oxide fuel cell was measured using indentation creep tests. Responses of shear strain to corresponding shear stress at the operating temperature of solid oxide fuel cell were analyzed, and the results revealed that the glass system
possesses Newtonian flow behavior at 600–630 °C. In addition, the stress exponent and the activation energy for viscous flow at different temperatures and stresses were also determined. Finally, the absolute-rate theory was adopted to describe the viscous flow for the glass. The results were compared with other glass systems.
L0148 – Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying
In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low YoungÕs modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400 °C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore
coarsening and stiffening of the coating. In-situ measurements at 1400 °C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.
L0169 – Constitutive modeling of the behaviour of cermet compacts during reaction sintering
This study deals with the identification of a constitutive equation describing the mechanical behaviour of a nickel ferrite based cermet during sintering. This constitutive equation considers the material as a continuum and may enable one to predict the densification behaviour of a powder under different thermal treatments and the impact of compact geometry, external loading on strain and stress generation. A classical viscous equation of the Newtonian type that includes a term describing free sintering densification has been chosen. The method used for the identification of the parameters of this equation is the one proposed Gillia et al., which is based on dilatometry measurement. It includes a stairway thermal cycle for the determination of the free sintering term and intermittent loading for estimating the viscosity. This approach has been successfully applied to nickel ferrite cermet. The model has been found to be adequate to model the densification behaviour up to 1250 °C, but experimental and theoretical efforts must be accomplished to describe the behaviour above this temperature, when the material exhibits swelling.
L0158 – New composites of ZnO–P2O5/Ni having PTC transition and high Seebeck coefficient
In this article, we report the electrical conductivity (?) and Seebeck coefficient (S) of ZnO–P2O5 matrix filled with conductive powder of nickel (Ni). The variation of ? versus volume fraction of Ni showed a non-conducting to conducting phase transition at percolation threshold (28 vol. %). The change of S from high positive to negative values exhibits that this transition is accompanied by the passing of carrier charge from p to n type. On the other hand, the measurements of ? and S as function of temperature, above the percolation threshold, showed a positive temperature coefficient (PTC) phase transition at Tc ? 400 K, linked with a high S = ? 5000 ?V/K, giving highest power factor PF = ?.S 2? 2.10? 4 W m? 1 K? 2. The temperature dependence of the volume expansion enabled to confirm that this transition is associated to the thermal volume variation in matrix. However, the temperature dependence of ? below the percolation threshold showed two different mechanisms: thermally activated hopping behavior at high temperatures and Mott's variable range hopping (VRH) at low temperatures
L0147 – Sintering and Creep Processes in Plasma-Sprayed Thermal Barrier Coatings
During operation at elevated temperatures, sintering processes can significantly influence the mechanical properties of thermal barrier coatings (TBCs) by increasing Young’s modulus and reducing strain tolerance. These changes of the mechanical response of TBCs were investigated using free-standing plasma-sprayed TBCs in a thermomechanical analysis (TMA) facility. The time-dependent change of Young’s modulus was determined in situ in a flexure mode at different annealing temperatures. In addition, relaxation processes during loading and unloading were monitored. The time-dependent deformation behavior of the TBC sample can be described by a simple viscoelastic approach (Burgers model). Viscosity data are determined as a function of annealing temperature and time.
L0168 – Long-term degradation of Ta2O5-doped Bi2O3 systems
Bismuth oxide in ?-phase is a well-known high oxygen ion conductor and can be used as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). 5–10 mol% Ta2O5 are doped into Bi2O3 to stabilize ?-phase by solid state reaction process. One Bi2O3 sample (7.5TSB) was stabilized by 7.5 mol% Ta2O5 and exhibited single phase ?-Bi2O3-like (type I) phase. Thermo-mechanical analyzer (TMA), X-ray diffractometry (XRD), AC impedance and high-resolution transmission electron microscopy (HRTEM) were used to characterize the properties. The results showed that holding at 800–850 °C for 1 h was the appropriate sintering conditions to get dense samples. Obvious conductivity degradation phenomenon was obtained by 1000 h long-term treatment at 650 °C due to the formation of ?-Bi2O3 phase and Bi3TaO7, and ?1 1 1? vacancy ordering in Bi3TaO7 structure.
L0157 – Deformation and cracking during sintering of bimaterial components processed from ceramic and metal powder mixes. Part II: Numerical simulation
In a companion paper (Part I), the processing of two-layer parts by co-sintering of two powder blends has been investigated. As a complement to this experimental study, a finite element simulation of this operation has been achieved. This simulation was based on constitutive equations identified from specific experiments performed with each blend. The numerical results provided deformation and internal stress information that have been found to be fully consistent with the experimental observation. In particular they confirm that cracking occurs in the course of heating, when one material starts densifying and the other one is still brittle, whereas a large densification mismatch at high temperature is not harmful because the low viscosity of both materials leads to the relaxation of internal stresses.
L0146 – Synthesis and characterization of a nano-scaled barium cerate perovskite powder using starch as polymerization agent
The preparation of nano-sized BaCeO3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4 m2/g. TEM investigations reveal particles mainly in the size range of 30 to 65 nm. The shrinkage and sintering behavior of resulting powder compacts were studied in comparison to a coarse-grained mixed-oxide BaCeO3 powder (SBET=2.1 m2/g). Dilatometric measurements show that the beginning of shrinkage of compacts from the nano-sized powder is downshifted by 300 °C compared to
mixed-oxide powder. Compacts from the nano-sized powder reach a relative density of 91% after sintering at 1450 °C for 10 h.
L0167 – Preparation of morphology controlled Th1?xUxO2 sintered pellets from low-temperature precursors
Dense sintered samples of Th1 ? xUxO2 solid solutions were prepared from the initial precipitation of oxalate precursors through two different wet chemical routes, based either on the direct precipitation of the cations or on the use of hydrothermal method. For both low-temperature precursors, the specific surface area was followed versus the heating temperature and the influence of the conversion step on the oxide powder reactivity was evidenced since it allowed to obtain reactive surfaces in the range of 15–45 m2 g?1 without any additional grinding step. From dilatometric studies, the operating conditions required for the complete densification of the Th1 ? xUxO2 pellets were set to a heat treatment of 3 h at 1500 °C. In these conditions, the density of the samples lies between 94% and 99% of the calculated value whatever the preparation method chosen which appeared very promising compared to the results already reported under inert atmosphere. The initial precipitation of low-temperature precursors thus allowed to lower the sintering temperature by about 100 °C while the use of hydrothermal conditions significantly improved the cationic distribution in the sintered samples, as shown from EPMA statistical experiments.
L0156 – Influence of thermal damage occurrence at microstructural scale on the thermomechanical behaviour of magnesia–spinel refractories
Many refractory materials exhibit high thermal shock resistance, which is often mostly due to their high flexibility. Understanding the microstructure key points allowing to develop a non-linear mechanical behaviour is of great relevance for future material improvements. The present work aims at optimising the processing of magnesia–spinel refractory materials close to industrial ones with simplified microstructures. The final goal is the investigation of the relationship existing between microstructure evolutions and induced thermomechanical properties. The thermal expansion mismatch which exists between the two phases (spinel inclusions and magnesia matrix) is expected to generate, during cooling, radial microcracks around the inclusions. The development of such microcracks network, closely related to the inclusions content, has been studied and the damage occurrence has been confirmed by several high temperature characterisation techniques. The influence of this thermal micro damage on the evolution of stress–strain law in tension of such materials has also been investigated.
L0145 – Drastic decrease of Ba(Zn1/3Ta2/3)O3 sintering temperature by lithium salts and glass phase addition
The complex perovskite oxide Ba(Zn1/3Ta2/3)O3 (BZT) has been studied for its attractive dielectric properties which make this material interesting for applications such as multilayer ceramics capacitors or hyperfrequency resonators. Nevertheless, BZT ceramic requires high temperature to be correctly sintered (@1450°C), that is too high to envisage a silver co-sintering (Tf(Ag)
= 961°C). For this reason, the lowering of the sintering temperature of BZT by glass phase’s additions has been investigated. This material is sinterable at low temperature with combined glass phase –lithium salt additions, and exhibits, at 1MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature.
The 5 wt% of ZnO-SiO2-B2O3 glass phase and 1 wt% of LiF added BZT sample sintered at 900°C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant ?r of 32, low dielectrics losses (tan (?)< 10-3) and a temperature coefficient of permittivity ?? of -10ppm/°C. Their good dielectric properties and their compatibility with silver
electrodes, make these ceramics suitable for L.T.C.C applications.
L0166 – Effect of sintering temperature on microstructure and transport properties of Li3xLa2/3?xTiO3 with different lithium contents
Li3xLa2/3?xTiO3 (LLTO) powder with different lithium contents (nominal 3x = 0.03–0.75) was synthesized via a simple sol–gel route and then calcination of gel-derived precursor at 900 °C which was much below the calcination temperature required for synthesizing the LLTO powder via solid state reaction route. The LLTO powder of sub-micron sized particles, derived from such sol–gel method, showed almost no aggregation. Starting from the sol–gel-derived powder, the LLTO ceramics with different lithium contents were prepared at different sintering temperatures of 1250 and 1350 °C. It demonstrated that our sol–gel route is quite simple and convenient compared to the previous sol–gel method and requires lower temperature for the LLTO. Our results also illustrated that lithium content significantly affects the structure and ionic conductivity of the LLTO ceramics. The dependence of the ionic conductivity on the lithium content, lattice structure, microstructure and sintering temperature was investigated systematically.
L0155 – Thermophysical properties of U2Mo intermetallic
The current paper has investigated specific heat capacity, coefficient of thermal expansion and phase transition temperatures of U2Mo intermetallic. The transformation of U2Mo phase to bcc (?-uranium) phase occurred at 853 K. The coefficient of thermal expansion has been determined in the temperature range 423–873 K to be 14.65 × 10?6 K?1. The specific heat data showed a smooth curve up to 773 K and above it a change in trend to follow a ?-shape was observed. The specific heat values of U2Mo have been found to be lower than that calculated from the additivity rule. This study provides first time data on U2Mo. The data obtained from this investigation were compared to available literature on U–Mo alloys
L0144 – Non-Newtonian Deformation of Co-Based Metallic Glass at Low Stresses
Abstract—The results of precision measurements of creep in Co-based metallic glass are presented. It is shown that, in spite of generally accepted concepts, plastic flow at low stresses under intense structural relaxation conditions is of a non-Newtonian type. Consequences of this fact are considered
L0165 – Processing, physico-chemical characterisation and in vitro evaluation of silicon containing ?-tricalcium phosphate ceramics
For bone grafting applications, the elaboration of silicon containing beta-tricalcium phosphate (?-TCP) was studied. The synthesis was performed using a wet precipitation method according to the hypothetical theoretical formula Ca3 ? x(PO4)2 ? 2x(SiO4)x. Two silicon loaded materials (0.46 wt.% and 0.95 wt.%) were investigated and compared to a pure ?-TCP. The maturation time of the synthesis required in order to obtain ?-TCP decreased with the amount of silicon. Only restrictive synthesis conditions allow preparing silicon containing ?-TCP with controlled composition. To obtain dense ceramics, the sintering behaviour of the powders was evaluated. The addition of silicon slowed the densification process and decreased the grain size of the dense ceramics. Rietveld refinement may indicate a partial incorporation of silicon in the ?-TCP lattice. X-ray photoelectron spectroscopy and transmission electron microscopy analyses revealed that the remaining silicon formed amorphous clusters of silicon rich phase. The in vitro biological behaviour was investigated with MC3T3-E1 osteoblast-like cells. After the addition of silicon, the ceramics remained cytocompatible, highlighting the high potential of silicon containing ?-TCP as optimised bone graft material.
L0154 – Thermal behavior of apatitic calcium phosphates synthesized from calcium carbonate and orthophosphoric acid or potassium dihydrogen orthophosphate
The synthesis of calcium hydroxyapatite powder (Ca-HA) from orthophosphoric acid or from potassium dihydrogen orthophosphate and calcium carbonate was carried out under moderate conditions. A better dissolution of calcium carbonate and a complete precipitation of the orthophosphate species were obtained with orthophosphoric acid, indicating that it may be of interest as a phosphate source compared with potassium dihydrogen orthophosphate. The influence of calcination treatment on the physico-chemical properties of the solids is discussed in this paper. Different characterization techniques such as specific surface area (SBET), true density, particle size distribution, thermo-mechanical analysis, simultaneous thermogravimetry and differential scanning calorimetry analysis, X-ray diffraction and infrared were performed to understand the phase changes during thermal treatment. Specific surface area decreased while true density and particle size increased with the rise in the calcination temperature, due to the sintering of particles and the chemical reactions occurring at high temperatures. Mixtures of well-crystallized Ca-HA and tricalcium phosphate (TCP) or well-crystallized Ca-HA, CaO, and TCP were obtained after calcination at 800–1,000 °C of the solid products starting from orthophosphoric acid or potassium dihydrogen orthophosphate, respectively.
L0143 – Mechanisms in oxidation and sintering of magnetite iron ore green pellets
Thermal volume changes and oxidation mechanisms in magnetite iron ore green pellets balled with 0.5% bentonite binder, as a function of raw material fineness and pellet porosity, are shown. When a pellet starts to oxidize, a shell of hematite is formed around the pellet while the core still is magnetite. Dilatation curves were measured under non-oxidizing and oxidizing atmospheres to separately describe thermal volume changes in these two phases. Dilatation measurements showed contraction during oxidation between 330 and 900 °C by 0.5%. The extent of contraction was not influenced by the raw material fineness or the original porosity in pellets. Sintering started earlier in the magnetite phase (950 °C) compared to the hematite phase (1100 °C). The sintering rate increased with increasing fineness in the magnetite concentrate. A finer grind in the raw material would, therefore, promote the formation of duplex structures with a more heavily sintered core pulling away from the less sintered outer shell. At constant porosity in green pellets, the oxidation time became longer as the magnetite concentrate became finer, because of the enhanced sintering. In practical balling, however, the increase in fineness would necessitate the use of more water in balling, which results in an increase in green pellet porosity. These two opposite effects levelled out and the oxidation time became constant when green pellets were balled at constant plasticity. Combining the results from the oxidation and dilatation studies revealed new information on the rate limiting factors in oxidation of iron ore pellets. At 1100 °C, the diffusion rate of oxygen was limited by sintering in the magnetite core, taking place before oxidation rather than by the diffusion rate of oxygen through the oxidized hematite shell, as has been claimed in earlier literature. The oxidation rate was at maximum at around 1100 °C. At 1200 °C, the rate of oxidation substantially decreased because both the hematite shell and the magnetite core show heavy sintering at this temperature. Dilatometer measurements showed large thermal volume changes in the presence of olivine, at temperatures above 1200 °C. This is explained by the dissociation of hematite back to magnetite. Dissociation leads to an increase in the volume of the oxidized shell, while sintering of the magnetite core is further enhanced by the olivine additive.
T0004 – Thermally stimulated current observed in glass transition temperature
L0185 – Preparation of a poly(methyl methacrylate)-reduced graphene oxide composite with enhanced properties by a solution blending method
Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by a simple solution blending method. The glass transition temperature of the produced PMMA/graphene composite was increased by 37 °C with 1.0 wt.% RGO content, which is approximately 40% of improvement compared to that of pure PMMA. The thermal expansion coefficient (TEC) decreased by 68% with as low as 0.1 wt.% RGO loading. The electrical conductivity of the nanocomposites reached up to 0.037 S/m even with only 2.0 wt.% RGO, which increased by more than twelve orders of magnitude. The resulting nanocomposites showed that a stable colloidal suspension of graphene dispersion in organic solvent before blending with PMMA is necessary to fabricate the nanocomposites with enhanced properties.
L0174 – Formation and calcination temperature-dependent sintering activity of YAG precursor synthesized via reverse titration method
The composition homogeneity of YAG precursors synthesized via both normal and reverse titration co-precipitation methods is discussed. It was demonstrated that that the reverse titration process possesses better co-precipitation characteristics than the normal titration process, based on a real-time monitoring of the reaction pH and measurement of the Y/Al ratio in the precipitate. The formation process of the precipitate obtained by reverse titration method was discussed. The effect of calcination temperature on sintering properties of the YAG powder was investigated by analysis of the crystalline phase, the specific surface area, and the morphology of the powder. The shrinkage rate test of compacts made from different powders indicates that a higher calcination temperature results in a lower densification speed and shrinkage ratios. Microstructure observation shows that the ceramics made from YAG nanopowder, which was obtained at a higher calcination temperature, have a more uniform grain-size distribution and fewer residual pores
T0003 – Open-circuit TSD method and anomalous air gap current in Teflon FEP
L0184 – Upgrading the performance of La2Mo2O9-based solid oxide fuel cell under single chamber conditions
Various anode-supported solid oxide fuel cells (SOFC), based on 10 mol% Dy-doped La 2 Mo 2 O 9 (LDM) electrolyte, are prepared analytically and operated under single chamber conditions to explore the connections between electrode and power performance. The cathode of tested SOFCs is compositionally graded with three composites of samarium strontium cobaltite and Gd-doped ceria (GDC) to relax the thermal stress, because of sizable thermal expansion differences above 400 °C. We focus the research attention on varying the anode pore structure and composition to promote the power performance in methane/air mixture at 700 °C. For the one-layer support of GDC+NiO+LDM anode, addition of 10 wt% graphite minimizes its mass transport resistance through creating 8–5 ?m long and ?1 ?m wide slit-shaped pores. The graphite pore former raises the peak power value by 80 mW cm ?2 . Adopting a more porous and active outer layer, the double-layer support further enhances the cell power. The peak power was first raised by 48 mW cm ?2 , using an outer layer that was prepared with 63 wt% NiO. Dosing 3% Pd on this outer layer uplifts another 59 mW cm ?2 . In this study, with an improved anode, the peak power value reaches 437 mW cm ?2 .
L0173 – Sintering and conductivity of BaCe0.9Y0.1O2.95 synthesized by the sol–gel method
Ceramic powders of BaCe0.9Y0.1O2.95 (BCY10) have been prepared by the sol–gel method. Barium and yttrium acetate and cerium nitrate were used as ceramic precursors in a water solution. The reaction process studied by DTA–TG and XRD showed that calcination of the precursor powder at T ? 1000 °C produces a single perovskite phase. The densification behaviour of green compacts studied by constant heating rate dilatometry revealed that the shrinkage rate was maximal at 1430 °C. Sintered densities higher than 95% of the theoretical one were thus obtained below 1500 °C. The bulk and additional blocking effects were characterized by impedance spectroscopy in wet atmosphere between 150 and 600 °C. A proton conduction behaviour was clearly identified. The blocking effect can be related to a space-charge depletion layer of protons in the vicinity of grain boundaries.
T0002 – Thermal analysis of amorphous phase in a pharmaceutical drug
Thermally Stimulated Current (TSC) spectroscopy and Differential Scanning Calorimetry (DSC) have been applied to the characterization of the microstructure of a pharmaceutical drug.
The dielectric relaxation spectrum shows two modes located in the temperature range of the glass transition. They have been attributed to the molecular mobility in the true amorphous phase and in the rigid amorphous region.
L0183 – The effect of MgO and SiO2 codoping on the properties of Nd:YAG transparent ceramic
Nd:YAG transparent ceramics were fabricated by a reactive sintering method under vacuum using SiO2, MgO and compound additives (SiO2 and MgO) as sintering aids. The effects of SiO2 and MgO on the microstructure and sintering process of Nd:YAG ceramics were studied. High quality Nd:YAG ceramics with compound sintering aids obtained by vacuum sintering at 1780 °C are composed of grains of the size ˜10 ?m, and their transmittance is 82% at 400 nm. It was found the absorption coefficient of 1.0 mol% Nd:YAG ceramic was 8.6 cm-1 at 808 nm and its absorption cross section was calculated to be 6.26 × 10-20 cm2.
L0172 – Reaction sintering of colloidal processed mixtures of sub-micrometric alumina and nano-titania
The fabrication of composites formed by alumina grains (95vol%) in the micrometer size range and aluminium titanate nanoparticles (5vol%) by reaction sintering of alumina (Al2O3) and titania (TiO2) is investigated. The green bodies were constituted by mixtures of sub-micrometric alumina and nano-titania obtained from freeze-drying homogeneous water based suspensions, and pressing the powders. The optimization of the colloidal processing variables was performed using the viscosity of the suspensions as control parameter. Different one step and two step sintering schedules using as maximum dwell temperatures 1300 and 1400°C were established from dynamic sintering experiments. Specimens cooled at 5°C/min as well as quenched specimens were prepared and characterized in terms of crystalline phases, by X-ray diffraction, and microstructure by scanning electron microscopy of fracture surfaces.Even though homogeneous final materials were obtained in all cases, full reaction was obtained only in materials treated at 1400°C. The microstructure of the composites obtained by quenching was formed by an alumina matrix with bimodal grain size distribution and submicrometric aluminium titanate grains located inside the largest alumina grains and at triple points. However a cooling rate of 5°C/min led to significant decomposition of aluminium titanate. This fact is attributed to the small size of the particles and the effect of the alumina surrounding matrix
T0001 – Molecular mobility study of amorphous and crystalline phases of a pharmaceutical product by thermally stimulated current spectroscopy
Two crystalline forms and the amorphous state of irbesartan, a pharmaceutical
drug chosen as a model, were analyzed by Thermally Stimulated Current (TSC)
spectroscopy, a powerful technique currently used in polymer science to investigate the
molecular dynamics of heterogeneous and complex materials. Whereas no specific
dielectric response was noted for the B crystalline form, the A form of irbesartan
exhibited molecular motions localized inside its channel structure. The dynamics
involved in the dielectric glass transition of amorphous samples followed a compensation
law characteristic of highly cooperative relaxation processes. Concerning the
amorphous content in physical mixtures, a calibration curve and a limit of detection
(2.5%) were established. The limit of detection could be improved by optimizing the TSC
experimental parameters. The amorphous sample recrystallized at a single temperature
was interpreted by the "idealized one-state model" defined here to describe systems
composed of identical semicrystalline particles in which amorphous and crystalline
phases are independent of each other (i.e., no chemical and physical interaction between
the two phases). Therefore, the idealized one-state model may be simulated by a twostate
model, which is representative of the two-phase model. Other samples recrystallized
through a complex annealing stage were explained by the classical one-state
model in agreement with the three-phase model used to describe bulk semicrystalline
systems. These results demonstrate that, as for polymers, the semicrystalline state of
pharmaceutical drugs should not be considered as a single state but as a more complex
system that can be described as an idealized one-state model or a one-state model
depending on the applied thermal treatment. These results give a new view that should
be taken into account in the development of amorphous pharmaceutical drugs and
L0182 – Solution combustion synthesis and sintering behavior of CaAl2O4
The influence of the quantity of urea on the synthesis of calcium aluminate by solution combustion method was studied. It was shown that the amount of urea has a big influence on morphological characteristic and phase composition of the combustion products.The sintering behavior of the combustion products, before and after milling, was studied by rate controlled sintering method, based on which a thermal schedule was designed improving the sintering of CaAl2O4 .
T0012 – Dielectric study of the molecular mobility and the isothermal crystallization kinetics of an amorphous pharmaceutical drug substance
During the development of new pharmaceutical products based on drug
substances in their amorphous form, the molecular mobility of an amorphous active
ingredient was characterized in detail within a very broad time-temperature range. The
relation between the isothermal crystallization kinetics and the dynamics of this
amorphous substance was investigated. First, dynamic dielectric spectroscopy (DDS) and
the thermostimulated current (TSC) techniques were used to analyze the molecular
mobility of the amorphous drug substance over a wide frequency and temperature range
(the drug substance is referred to as SSR in this text and was chosen as a model glassforming
system). Two relaxation processes, corresponding to different molecular
motions, were identified. The beta(a)-relaxation process, associated with intramolecular
oscillation of small dipolar groups, followed Arrhenius temperature behavior over the
entire time-temperature domain that was studied. However, the main alpha(a)-relaxation
process, assigned to the dielectric manifestation of the dynamic glass transition of the
amorphous phase, was described by Vogel-Fulcher-Tammann (VFT) and Arrhenius
behavior above and below the glass transition temperature (Tg) respectively. The
physical meaning of these complex dynamics is explained in the context of the Adam and
Gibbs (AG) model, by the temperature dependence of the size of cooperatively
rearranging regions (CRR) that govern the time scale of delocalized molecular motions.
The distinction between the molecular mobility and the structural relaxation of
amorphous systems below Tg is discussed. This work shows that the complementary
nature of bothDDSandTSCtechniques is essential to directly analyze the intramolecular
and molecular motions of disordered phases over a wide time-temperature range above
and below the Tg. Second, real-time dielectric measurements were carried out to
determine the isothermal crystallization kinetics of the SSR amorphous drug. Whatever
the crystalline form obtained over time in the crystallization process, the decrease of the
dielectric response of amorphous phase, which is characteristic of the isothermal crystallization,
was studied to monitor the time dependence of the degree of crystallinity. The
characteristic crystallization time, derived from Kohlrausch-Williams-Watt (KWW)-
Avrami analyses performed at different temperatures, followed an Arrhenius temperature
dependence. Behaviors specific to the molecular mobility of the amorphous drug
substance were compared with the characteristic crystallization time. It was concluded that the crystal growth process of the SSR drug seems to be controlled by the
intramolecular motions involving the beta(a)-relaxation mode and not by the molecular
motions responsible for the alpha(a)-relaxation mode in the range of temperatures >Tg.
Subsequent studies will focus on the crystallization process of the SSR drug in the glassy
L0192 – Influence of microstructure and architecture on oxygen permeation of La(1?X)SrXFe(1?Y)(Ga, Ni)YO3?? perovskite catalytic membrane reactor
Catalytic membrane reactors (CMR) have been an economically attractive process for natural gas reforming to syngas (H2 + CO) since more than twenty years. The CMR studied in this paper consists of a mixed ionic and electronic conductor dense layer (La(1?X)SrXFe(1?Y)GaYO3??). High temperature X-ray diffraction analysis, from room temperature to 900 °C under air and nitrogen atmosphere, show a reversible monoclinic to rhombohedral phase transition around 300 °C, and good chemical and dimensional stabilities of La0.8Sr0.2Fe0.7Ga0.3O3?? material. The La0.8Sr0.2Fe0.7Ga0.3O3?? dense layer elaborated by tape casting has been respectively coated with La0.8Sr0.2Fe0.7Ga0.3O3?? on the air side and La0.8Sr0.2Fe0.7Ni0.3O3?? on the inert side using screen printing. The influences of the dense membrane microstructure and of the surface exchange kinetics on the oxygen semi-permeation performances are evaluated. Small grain size, mainly below 1 ?m in the dense membrane significantly increases the oxygen flux. A porous layer of La0.8Sr0.2Fe0.7Ni0.3O3?? or La0.8Sr0.2Fe0.7Ga0.3O3?? on the air or inert side of the membrane increased strongly the specific oxygen semi-permeation. The impact of the porous layer is much more important than the reduction of the grain size. In this case, surface exchange kinetics are the limiting steps of oxygen permeation, and Ni-containing formulation leads to the highest flux.
L0181 – Chemical expansion of La0.8Sr0.2Fe0.7Ga0.3O3–?
This paper deals with the chemical expansion measurements and modelling of La0.8Sr0.2Fe0.7Ga0.3O3–?. The expansion behavior has been evaluated using a dilatometer and X-ray diffraction over a wide range of temperatures (RT to 1373 K) and oxygen partial pressures (10? 21 to 1 atm). The material stoichiometry evolution with temperature and oxygen partial pressure has been measured using thermogravimetry analysis at different oxygen partial pressure, from 10? 21 to 0.5 atm and from RT to 1473 K. Considering a typical defect model for lanthanum ferrite oxides, chemical expansion depends linearly on the Fe4+ concentration rather than on the oxygen vacancy concentration. A model of chemical expansion as a function of pO2 and temperature is then proposed. It helps to understand and anticipate the chemical expansion behavior exhibited by this material when used as Ionic Transport Membrane (ITM).
T0010 – Thermally stimulated current method applied to highly irradiated silicon diodes
We propose an improved method for the analysis of Thermally Stimulated Currents (TSC) measured on highly
irradiated silicon diodes. The proposed TSC formula for the evaluation of a set of TSC spectra obtained with different
reverse biases leads not only to the concentration of electron and hole traps visible in the spectra but also
gives an estimation for the concentration of defects which not give rise to a peak in the 30-220K TSC temperature
range (very shallow or very deep levels). The method is applied to a diode irradiated with a neutron fluence of
?n = 1.82 x 10^13 n/cm2.
L0191 – Ba1-xPrxCo1-yFeyO3-µ as cathode materials for low temperature solid oxide fuel cells
Ba1?xPrxCo1?yFeyO3?µ (BPCF) perovskite oxides have been synthesized and investigated as cathode materials for low temperature solid oxide fuel cells (LT-SOFCs). Compared with those of Ba0.5Sr0.5Co0.8Fe0.2O3?µ (BSCF) and Sm0.5Sr0.5CoO3 (SSCo) cathode materials, BPCF has a lower polarization resistance at
decreased temperatures. In particular, Ba0.5Pr0.5Co0.8Fe0.2O3?µ showed the lowest polarization loss among the different compositions as a cathode material for LT-SOFCs. The area specific resistance (ASR) of Ba0.5Pr0.5Co0.8Fe0.2O3?µ as a cathode material is 0.70 and 0.185 cm2 at 500 ?C and 550 ?C, respectively.
The maximum power density of the cell BPCF/SDC/Ni–SDC with humidified hydrogen as fuel and air as oxidant reaches 860mWcm?2 at 650 ?C.
L0180 – Microstructural development of interface layers between co-sintered alumina and spinel compacts
Tests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500 °C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40 ?m length and 5 ?m width was observed after 16 h at 1500 °C. Growth rate of the columnar spinel grains from parent spinel towards alumina follows parabolic kinetics, controlled by a mixed process of O2? ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth.
T0009 – The beta-alpha branching in D-sorbitol as studied by thermally stimulated depolarization currents (TSDC)
The molecular motions in D-sorbitol (D-glucitol) have been studied by thermally stimulated depolarization currents (TSDC) in the temperature region between -160 and 10°C. The relaxation appears as a broad global peak between -160 and -50°C and its features were compared with those of the relaxation of maltitol (a D-glucitol derivative). A study of the relaxation of sorbitol, which shows a maximum intensity at approximately -1°C, is also presented, and from the obtained data, the fragility index of this glass former is calculated. The and relaxations are observed to merge in the frequency window of the TSDC technique, and it is underlined that this merging is a consequence of the overlap of the tails of these distributions in this frequency window. In this context, the merging observed by TSDC images the branching of the most probable times of the two distributions predicted by dielectric relaxation spectroscopy at the branching temperature T.
L0190 – Studies on the synthesis of a Mo–30wt%W alloy by non-conventional approaches
In the present study, alternate routes for the synthesis of a single phase Mo–30 wt% W alloy were pursued to surmount the limitations experienced in conventional technique. The process essentially consists of preparation of active Mo and W powders by H2 reduction of the respective oxide intermediates through multiple processing steps and then converting those pure powders into Mo–30 wt% W alloy by mechanical alloying technique (MA) at RT under Ar atmosphere in a high-energy planetary ball mill. The structural evolution of the alloy from the milled powders at different interval of time was studied by X-ray diffraction (XRD) and phase corresponding to Mo–30W alloy was confirmed. The broadening of peaks in XRD pattern was due to crystallite refinement during milling towards the formation of the designated alloy. A high rate of densification for MA powder was achieved during sintering between 900 °C and 1200 °C and density close to theoretical density was attained. The microstructure of sintered alloy exhibited uniform, polyhedral grains with average grain size of about 3 ?m. The morphological evolution of as-milled powder was studied by Scanning electron microscopy (SEM) which revealed the formation of nano sized crystallites with polyhedral shapes. The crystallites were initially arranged in clusters which later on got distributed uniformly with the progress in milling time. The average crystallite size of MA powder was found to be 7.3 nm after 25 h of milling.
L0179 – Effect of mechanical stretching on electrical conductivity
and positive temperature coefficient characteristics of poly(vinylidene fluoride)/carbon nanofiber composites prepared by non-solvent precipitation
Poly(vinylidene fluoride) (PVDF)/carbon nanofiber (CNF) composites with filler content ranging from 0.047 to 4.7 vol.% were prepared with non-solvent precipitation followed by melt compression. The morphology and electrical conductivity of the composites before and after mechanical stretching were examined. The results showed that CNFs were dispersed homogeneously in the PVDF matrix and a low electrical percolation threshold of 0.90 vol.% CNFs was obtained. Mechanical stretching led to a sharp decrease in the electrical conductivity of a composite containing 0.94 vol.% CNF. This was caused by the destruction of a conducting network structure when the fillers aligned along the stretching direction. This did not happen when the filler content was increased to 1.88 vol.%. The percolating composites displayed a positive temperature coefficient (PTC) effect with the effect being larger in stretched composites. This can be attributed to the presence of PVDF ?-phase in stretched composites as revealed by X-ray diffraction and Fourier transform infrared spectroscopy.
T0008 – Comments on the compensation effect observed in thermally stimulated depolarization current analysis
Compensation has been reported for the relaxation parameters (the activation energy W and the pre-exponential factor t0) determined by using the thermal sampling (TS) technique. For the peaks obtained by the thermally stimulated depolarization current (TSDC) measurement, there is a relationship between W, t0 and the temperature of maximum intensity of the peak Tm that can be employed to deduce a general relationship between W, Tm, the compensation temperature Tc and the compensation time tc. This relationship can be used for a basic analysis of the compensation effect. By numerical simulations, and using parameters similar to those reported for concrete measurements, we show that it is possible to observe a compensation point only if the activation energy is a monotonically increasing power function of temperature of power coefficient between 1 and 2, more precisely, if Wincreases with temperature stronger than linearly but weaker than quadratically. The actual values of the compensation parameters are determined by the relationship between the activation energy and the temperature. The experimental uncertainties affecting the compensation temperature and the compensation time are significant, and consequently, it is not possible to have a precisely defined compensation point.
L0189 – Effect of fluorapatite additive on densification and mechanical properties of tricalcium phosphate
Tricalcium phosphate and synthesized fluorapatite powder were mixed in order to elaborate biphasic composites. The samples were characterized by X-ray diffraction, differential thermal analysis, infrared spectroscopy, scanning electron microscopy and by an analysis using (31)P nuclear magnetic resonance. The sintering of tricalcium phosphate with different percentages of fluorapatite (13.26 wt%; 19.9 wt%; 33.16 wt% and 40 wt%) indicates the evolution of the microstructure, densification and mechanical properties. The Brazilian test was used to measure the rupture strength of the sintered biphasic composites. The mechanical properties increase with the sintering temperature and with the addition of fluorapatite additive. The mechanical resistance of beta tricalcium phosphate-33.16 wt% fluorapatite composites reached its maximum value (13.7 MPa) at 1400 ( composite function)C, whereas the optimum densification was obtained at 1350 ( composite function)C (93.2%). Above 1400 ( composite function)C, the densification and mechanical properties were hindered by the tricalcium phosphate allotropic transformation and the formation of both intragranular porosity and cracks. The (31)P magic angle spinning nuclear magnetic resonance analysis of composites as sintered at various temperatures or with different percentages of fluorapatite reveals the presence of tetrahedral P sites
L0178 – Microwave sintering of nano-sized ZnO synthesized by a liquid route
Zinc oxide is a widely used material in various applications in electronic, optic, and spintronic fields, in particular. The control of the final properties of ZnO requires the mastering of the final microstructure. To achieve this goal, the grain growth of ZnO has been examined as a function of the sintering conditions, in particular in using a specific microwave sintering method. In order to get nano-sized ZnO powder as a starting material, a liquid route was implemented. The latter is based on the direct precipitation of a zinc oxalate solution. After thermal treatment, pure ZnO powder was obtained with a very narrow grain size distribution, centered at around 20 nm. The sintering of this powder was then carried out in conventional and microwave furnaces. While an important grain growth occurs during the conventional sintering, it is shown that microwave sintering allows us to maintain the grain size at the nano-metric scale.
T0007 – Coherent vibrations in “polar / non-polar”-like complex polymeric mixtures. A dielectric approach to percolation phenomena
The analysis of thermostimulated currents by the fractional polarization procedure has been used to establish the existence of a coherent vibration in Linseed oil/mastic varnish mixtures. This excitation is seen in the oil component when its proportion in the system is inferior to its percolation threshold. The observed phenomenon complies with compensation laws and is interpreted in the framework of the formalism developed by Fröhlich to understand collective phenomena in biological systems.
L0188 – Mechanical properties of tricalcium phosphate–alumina composites
This study deals to produce tricalcium phosphate - fluorapatite composites sintering at various temperatures (, and ) and with different alumina additives amounts (2.5 wt%, 5 wt%, 7.5 wt%, 10 wt% and 20 wt%). The characterization of samples before and after sintering was investigated, using X-ray diffraction, infrared spectroscopy, scanning electronic microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. Mechanical properties have been measured by Brazilian test. The evolution of composite rupture strength was studied as a function of sintering temperature. The effect of sintering on the mechanical properties was measured with the change in composition and microstructure of the composite. The mechanical resistances of composites were increased with the temperatures and with concentrations of alumina. At , the mechanical resistance reaches its maximum value with 5 wt% Al2O3 (13.6 MPa) whereas the optimum density is about 90% with 2.5 wt% Al2O3.
L0177 – Enhancing strength and hardness of AZ31B through simultaneous addition of nickel and nano-Al2O3 particulates
In the present study, AZ31B–Al2O3–Ni composites are developed by the addition of different amounts of Ni particulates into AZ31B–1.5Al2O3 using disintegrated melt deposition technique followed by hot extrusion. The AZ31B–1.5Al2O3 nano-composite is known to exhibit excellent ductility (?30%) matching with that of pure aluminum but its strength levels are compromised. The composites developed in the current study show a homogeneous microstructure and significant improvement in mechanical characteristics. The results of mechanical properties characterization reveal that addition of Ni led to a simultaneous improvement in 0.2% YS (up to 25%), UTS (up to 13%) and hardness (up to 62%). The ductility, however, stayed almost similar to the ductility of monolithic AZ31B in the case of AZ31B–1.5Al2O3–1.5Ni composite while it was compromised for AZ31B–1.5Al2O3–3.19Ni. The results clearly reveal the superior capability of AZ31B–Al2O3–Ni formulations in terms of overall mechanical response when compared to monolithic AZ31B.
T0006 – Effect of water on thermally stimulated currents in oxidised low-density polyethylene
The electrical conduction properties of low-density polyethylene (LDPE) oxidised in an ozone atmosphere produced by an electrical discharge in air, particularly the current behaviour in a short-circuited state, have been investigated. An anomalous discharging current and a reverse TSC flowing in the same direction as the charging current were observed. It has been found that the cause of these unique phenomena exists not on the cathode side, but on the anode side and that the water absorbed in the oxidised LDPE plays an important part. It is suggested that these unique properties are due to protons (H+) injected at the anode, possibly associated with an anode oxidation reaction at the oxidised LDPE-electrode interface
L0187 – The densification, microstructure, and electrical properties of aluminum-doped zinc oxide sputtering target for transparent
conductive oxide film
AZO films are regarded as a potential substitute for ITO due to their excellent performance. To optimize the performances of AZO films, the correlation between the target and film must be clearly clarified. Therefore, how the properties, particularly the electrical ones, of the sputtering targets evolve with the sintering parameters are rarely highlighted. To develop high-quality AZO and ZnO targets, the densification, microstructure, and electrical properties of the targets were investigated in this study. The results showed that after sintering at 1100 °C in air, the 2 wt% Al2O3 additive in ZnO results in retarded densification, the formation of ZnAl2O4 phase, and inferior electrical properties. However, after sintering at 1200 °C or higher temperatures, the Al2O3 additive leads to finer grain size, higher sintered density, and better electrical properties. In general, the AZO targets are also found to exhibit higher Hall mobility and lower carrier density than the AZO films do.
L0176 – Feasibility study on utilizing carbon dioxide during the processing of Mg–Al alloys
The feasibility of utilizing carbon dioxide (CO2) during magnesium–aluminium (Mg–Al) alloys processing was investigated by incorporating CO2 gas during melting and casting of the alloys. Mg–Al alloys containing ?3 wt.% and ?5 wt.% Al were processed with and without CO2 atmosphere using the disintegrated melt deposition (DMD) technique. The cast alloys after extrusion were characterized for their structural, physical and mechanical properties to identify the utilization of carbon dioxide during processing. Results indicated that sound, defect-free Mg-Alloys were produced with CO2 processing. Improvement in mechanical properties such as hardness, tensile strength and compressive yield strength were observed. The in situ formation of Al4C3 phase during processing was identified as the reason for the improvement in the properties, which indicated the utilization of carbon dioxide by the melt.
T0005 – Amorphous phase separation in polypropylene block copolymers as revealed by thermostimulated depolarization measurements. I.complex spectra study
The thermally stimulated depolarization (TSD) technique was used to observe the amorphous phase separation in polypropylene block copolymers and to attribute its various dielectric relaxations to precise mobile entities. The complex thermostimulated spectra of polypropylene block copolymers were compared to complex spectra of polymers of the same nature as those of its main components, i.e., isotactic polypropylene, high-density polyethylene, and propylene-ethylene rubber. With TSD we then studied a binary blend of polypropylene and high-density polyethylene and another blend of polypropylene and propylene-ethylene rubber and also the various parts of polypropylene block copolymer which were separated by a selective solvent extraction. From peak-position and intensity considerations we suggested the origin of the three relaxations appearing from 90 to 290 K in the TSD complex spectra of polypropylene block copolymer
L0186 – Structural modifications induced by free protons in proton conducting perovskite zirconate membrane
Recently hydrogen appears as an alternative energy vector for a sustainable modern world. Proton conducting perovskite ceramics showing significant proton conduction (~ 10? 2 S/cm at 600 °C) at medium temperature exhibit high potential as electrolytic membranes of water steam electrolysers. Prior to industrial requirements (mechanical and chemical stability, long working life) the structural behaviour of the host perovskite structure disturbed by the Ln/RE substitution and the presence of protonic species have to be well determined as a function of severe operating conditions. Ex situ neutron diffraction and thermal expansion as well as in situ high water pressure Raman studies were performed on non-protonated, protonated and deprotonated high dense SrZr0.9Yb0.1O2.95 ceramics. The results show that the proton doping (SrZr0.9Yb0.1O2.95H0.003) induces long range order structural modifications, weak enough to guaranty the stability during the high water pressure–high temperature cycling.
L0175 – Sintering Behavior ofMagnesium-Substituted Fluorapatite Powders Prepared by HydrothermalMethod
Magnesium-substituted fluorapatite powders were synthesized by hydrothermal method, and their sintering behavior was investigated by dilatometry in the temperature range 25–1100°C. Analysis of the obtained powders by X-ray diffraction and 31P NMR spectroscopy showed that the powders consisted of a single apatite phase and no amorphous phase has been formed. Compared to pure fluorapatite, the shrinkage of the substituted samples occurred in two steps and the temperature at which the sintering rate was maximum is lower. In addition, the shrinkage was interrupted by an expansion of the samples due to the formation of a liquid phase. The latter phase led to the crystallization of needle-crystals by a dissolution-diffusion-reprecipitation process.
T0037 – Weak solid-solid transitions in pharmaceutical crystalline solids detected via thermally stimulated current
To demonstrate the ability of thermally stimulated current (TSC), normally used to study amorphous systems, in detecting weak solid-solid transitions in crystalline pharmaceutical compound. Methods: Polymorphs of a new chemical entity, LAU254, were generated and characterized using conventional and hot plate X-ray diffraction, DSC and TSC. Equilibration of 50:50 mixtures of the different polymorphs and solubility studies were conducted in aqueous and organic solvent at 25 and 50°C and then analyzed by X-ray and DSC. Results: Four crystalline forms (A-D) were isolated. Form B showed one single endotherm at 180°C while the other forms showed lower melting endotherms, a crystallization exotherm and eventually a final melting endotherm corresponding to that of form B (180°C). The heat of fusion of form B was the highest. In contrast, solubility as well as mixture equilibration studies resulted in all forms converting to form A. TSC analysis revealed a well-defined reproducible peak with a maximum at 130°C which was suspected to be a solid-solid transition. This was confirmed by hot plate X-ray diffraction where careful probing around 120-130°C revealed three different forms; form A (the initial form), a second form that appears above 150°C, melts, crystallizes and produces form B. Careful inspection of larger sample sizes in DSC showed a small endotherm at 130°C. Conclusions: TSC, normally used to study amorphous systems, proved to be useful in detecting weak solid-solid transitions in crystalline pharmaceuticals, an application that has never been explored or reported previously. This resulted in identifying a form, obtainable only at temperatures above the transition temperature (related enantiotropically to the form that is most stable at ambient temperatures) and in reconciling the DSC and solubility data. TSC can be very useful in detecting and probing those transitions that occur in the solid state due to subtle dipolar motion and are not associated with large changes in global motion and heat capacity that is needed for detection by DSC and therefore can be complementary to DSC in obtaining a more complete assessment of the polymorphism behavior of crystalline solids.
T0026 – Thermally stimulated measurements on polycrystalline Pbl2 layers
Thermally stimulated current measurements have been performed on polycrystalline layers of lead iodide grown from solution. Several TSC peaks or bands have been observed at temperatures of 100 K, 195-220 K, 230-240 K and 270-300 K. Comparison with PbI 2 single crystal shows that the polycrystalline structure of the material introduces additional defects. In contrast the defect currently found in single crystal and attributed to the lead vacancy has not been clearly evidenced in the polycrystalline layers. The position and relative intensity of the peaks can be modified by Ag doping and thermal annealing. On the other hand, only small differences resulting from the anisotropy of the material have been observed depending on the orientation of the electric field with regards to the grains orientation.
T0015 – Comparison of chemical treatments on the chain dynamics and thermal stability of bovine pericardium collagen
A new approach for the replacement of heart
valves consists of obtaining an acellular matrix from animal
aortic valves that performs mechanically, is nonantigenic,
and is free from calcification and fibroblast proliferation.
Novel biochemical treatments must be developed for this
purpose. In this work, we focus on the characterization of
collagen in acellular bovine cardiovascular tissues, fresh or
glutaraldehyde treated, and stored in different solutions
[phosphate-buffered saline (PBS), ethanol, octanol, and glutaraldehyde],
to determine whether the resulting fibrous
material is structurally preserved. The preservation of the
triple helical structure of collagen is checked by differential
scanning calorimetry (DSC), which is a well suited technique
to analyze thermal transitions in proteins, such as denaturation.
To get insight into the molecular dynamics of collagen
in the nanometric range, we used thermally stimulated currents,
a dielectric technique running at low frequency, that
measure the dipolar reorientations in proteins submitted to
a static electrical field. The combined use of these two techniques
allowed us to evaluate the physical structure and
conformation of collagen after the different chemical treatments.
We have found that the glutaraldehyde treatment
followed by octanol storage preserves the triple helical conformation
of the polypeptidic chains of collagen, contrary to
the ethanol and PBS storage that induce drastic changes in
the thermal and dielectric behavior of the protein. Moreover,
this particular chemical treatment stabilizes the collagen
structure (shift toward high temperature of the collagen denaturation
and stiffening of the chains by a cross-linking
action) when compared to the control sample, and so could
provide interesting fibrous material for the conception of
bioprosthetic heart valve.
T0036 – The determination of the activation energy of a relaxational process from thermally stimulated depolarisation currents (TSDC) data: an illustration with the beta-relaxation of maltitol
Three different and independent procedures to obtain the activation energy of a motional process from thermally stimulated depolarisation currents (TSDC) data are reported. One of the procedures requires a single thermal sampling (TS) experiment: the activation energy is calculated from the temperature dependence of the relaxation time associated with this TS peak. The other two procedures are based on the influence of the heating rate on the features of the TS peak namely, on the temperature location Tm and on the intensity of the maximum I(Tm) of the peak. The illustration with the case of an elementary component of the beta-relaxation of maltitol shows that the values of the activation energy provided by these procedures are in good mutual agreement. The fact that the TSDC technique provides different and independent procedures to obtain the kinetic parameters of a motional process is a unique feature in the context of the experimental techniques most often used to study molecular mobility.
T0025 – Thermally stimulated current in SiO2
Thermally stimulated current (TSC) techniques provide information about oxide-trap charge densities and energy distributions in MOS (metal-oxide-semiconductor) capacitors exposed to ionizing radiation or high-field stress that is difficult or impossible to obtain via standard capacitance-voltage or current-voltage techniques. The precision and reproducibility of measurements through repeated irradiation/TSC cycles on a single capacitor is demonstrated with a radiation-hardened oxide, and small sample-to-sample variations are observed. A small increase in Edelta' center density may occur in some non-radiation-hardened oxides during repeated irradiation/TSC measurement cycles. The importance of choosing an appropriate bias to obtain accurate measurements of trapped charge densities and energy distributions is emphasized. A 10 nm deposited oxide with no subsequent annealing above 400°C shows a different trapped-hole energy distribution than thermally grown oxides, but a similar distribution to thermal oxides is found for deposited oxides annealed at higher temperatures. Charge neutralization during switched-bias irradiation is found to occur both because of hole-electron annihilation and increased electron trapping in the near-interfacial SiO2. Limitations in applying TSC to oxides thinner than 5 nm are discussed.
T0014 – Molecular stability of elastin : effect of molecular architecture
The thermal and dielectric properties of elastin and two soluble derivatives ( k-elastin and derived elastin
peptides from enzymatic elastolysis) were investigated in the freeze-dried state in a wide temperature range
(from -180 to +220°C). The glass transition of these amorphous proteins was studied by differential
scanning calorimetry (DSC). The dielectric relaxations of both proteins were followed by thermally stimulated
currents (TSC), an isochronal dielectric spectrometry running at variable temperature, analogous to a lowfrequency
spectroscopy (10^(-3) - 10^(-2) Hz) and by dynamic dielectric spectroscopy (DDS), performed
isothermally with the frequency varying from 10^(-2) to 3 x 10^6 Hz. The combination of TSC and DDS
experiments and the determination of the activation parameters of the relaxation times inform about the
molecular mobility of the proteins, both in the glassy state and in the liquid state. Major differences between
the relaxation behavior of elastin and its soluble derivatives have been discussed and correlated with the
molecular architecture of the proteins.
T0035 – Low frequency chain dynamic of cross-linked poly(acrylic acid)
Cross-linked poly(acrylic acid) (PAA) synthesized by radical polymerization in inverse suspension is a swelling gel. The physical structure of PAA has been analyzed using low frequency chain dynamic given by the analysis of thermo stimulated currents (TSC). The alpha primary dielectric relaxation mode observed around the glass transition temperature (Tg=+38°C) corresponds to the slowest dynamic. The relaxation times of the constituting processes show that it is due to a delocalized cooperative molecular mobility involving nanometric sequences of the hydrocarbon skeleton. The beta secondary dielectric relaxation mode observed at lower temperature (Tbeta=-35°C) corresponds to a higher frequency molecular mobility. It has been assigned to the cooperative mobility of hydrogen bonded COOH groups. In fact, the hydrogen bonded side chains behave as an hydrophilic matrix in which nanometric domains constituted by sequences of the main chain are embedded. Such a picture might explain the specific swelling properties of cross-linked PAA.
T0024 – Thermally-stimulated current and dielectric loss measurement of polypropylene and teflon-FEP films immersed in diarylethane
Some properties of oil/PP (biaxially stretched polypropylene) and oil/FEP (Teflon FEP) composite insulators have been investigated with TSC (thermally stimulated current) techniques. The oil/PP system showed three TSC peaks originating from carriers captured in the swollen surface region of the PP. The TSC spectra depended strongly on the polarity of the poling voltage and on the impregnating temperature. Their analysis yielded information on the carrier traps existing near the PP surface in the oil/PP interface region. On the other hand, the TSC spectrum of the oil/FEP system has a small impregnating temperature dependence and a small effect of the poling voltage polarity. The difference in TSC between oil/PP and oil/FEP systems is closely related to the difference in the oil-polymer interaction. The TSC is a useful method for investigating carrier traps in the surface region and their change due to the oil-polymer interaction. To investigate further the relation between the carrier traps and tan delta, collecting bias TSC was measured on a specimen to which an ac voltage was applied. The results indicate that the decrease in tan(delta) during the ac voltage application depends on the amount of trapped carriers near the polymer's surface or, the decrease in carriers in the oil