E0247 – Mechanical Activation of Spinel and Pyrochlore Phases in ZnO Based Varistors
Mixtures of ZnO, Sb2O3 and Bi2O3 powders corresponding to the stoichiometric compositions of Zn7Sb2O12 (spinel) and Zn2Bi3Sb3O14 (pyrochlore) were milled in a shaker mill (SPEX) up to 180 minutes. The influence of the mechanical activation of the powders, as a result of the milling, was determined by Differential Thermal Analysis, Thermogravimetric Analysis and X-ray Diffraction. Additionally, in order to compare to commercial recipes the mixture ZnO + 2.7 wt% Sb2O3 + 4.5 wt% Bi2O3 was milled in a shaker mill up to 180 minutes. Varistor devices were fabricated with both milled and unmilled mixtures. The devices were characterized by I-V studies, Scanning Electron Microscopy and X-ray Diffraction. Mechanical activation on the system ZnO-Bi2O3-Sb2O3 produced a chemical reaction and amorphization in the powder mixture. The weight loss due to volatilization of Bi2O3 and Sb2O3 that occurrs in both ZnO-Sb2O3 and ZnO-Sb2O3-Bi2O3 systems at temperatures below 1200°C is reduced by milling the powder mixtures.
E0246 – Sintering of tricalcium phosphate–fluorapatite composites by addition of alumina
The effect of alumina (Al2O3) addition on the densification of tricalcium phosphate–26.52 wt% fluorapatite composites was investigated. The sintering behaviour was investigated using X-ray diffraction, scanning electron microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. The composites sintering alumina additives have been tested in order to enhance their sinterability. When small amount of Al2O3 was added, densification of the tricalcium phosphate–26.52 wt% fluorapatite composites was markedly enhanced. The densification of the pure
tricalcium phosphate–26.52 wt% fluorapatite composites was about 87%, whereas it reached 91% with 2.5 wt% Al2O3 at 1300 8C. High temperatures were not very efficient conditions. About 1400 8C, grain growth becomes important and induces an intragranular porosity which is responsible for decrease in density. The 31P and 27Al MAS-NMR analysis of tricalcium phosphate–26.52 wt% fluorapatite composites sintered with Al2O3 additives reveals the presence of tetrahedral P and octahedral Al sites.
E0245 – Phase Equilibria of the Constituent Ternaries of the Mg-Al-Ca-Sr System
Thermodynamic modeling of the Al-Ca-Sr, Mg-Ca-Sr, Mg-Al-Ca and Mg-Al-Sr systems was conducted using the modified quasichemical model. A self-consistent database has been established for these systems. Mg-Al-Ca and Mg-Al-Sr ternary systems were studied experimentally through microstructure characterization, phase identification, and thermal analysis and
thermodynamic modeling based on these experimental fi ndings. It has been observed that the intermetallic compounds in the Mg-Ca, Mg-Sr, Al-Ca, and Al-Sr binary systems dissolve the
third component in the respective ternary phase diagrams. In addition, two ternary compounds, Mg56Al40Sr4 and Mg2Al4Ca3, have been reported.
E0244 – Strontium oxide doped quaternary glasses: effect on structure, degradation and cytocompatibility
This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by P2O5–Na2O–CaO–TiO2. The following four different glass compositions were manufactured: 0.5P2O5–0.17Na2O–0.03TiO2–(0.3-x)CaO–xSrO where x = 0, 0.01, 0.03 and 0.05. Structural characterisation revealed glass transition temperatures in the range 427–437°C and the presence of sodium calcium phosphate as the dominant phase in all the glasses. Degradation and ion release studies conducted over a 15-day period revealed
that the Sr-containing glasses showed significantly higher degradation and ion release rates than the Sr-free glass. Cytocompatibility studies performed over a 7-day period using MG63 cells showed that the addition of 5 mol% SrO yielded glasses with cell viability nearly equivalent to that observed for quaternary TiO2 glasses.
E0243 – Estimation of Liquidus Temperatures for Multicomponent Silicates from Activation Energies for Viscous Flow
This article considers the viscous-flow phenomenon in molten silicate melts in the vicinity of their liquidus temperatures. An agglomeration of ionic species occurs in the liquid slag with decreasing temperatures and results in an increase in the viscosity and the activation energy for viscous flow. The latter was found to be nonlinear, increasing rapidly as the temperature is approached wherein a solid phase is likely to separate from the liquid. The second derivative of the activation energy for viscous flow with respect to temperature was found to show a discontinuity in the vicinity of the liquidus temperature. This has been verified in the case of viscous flow for both pure water and CaOSiO2 melts. Experimental data for the viscosities of complex silicate melts and mold fluxes have also demonstrated the occurrence of a discontinuity in the second-derivative function, which is in accordance with the liquidus temperature as determined by differential thermal analysis (DTA). Thus, the second derivative offers a useful way of estimating the liquidus temperatures of multicomponent silicates, which are often difficult to determine due to supercooling effects.
E0242 – Stabilization of Thermosolutal Convective Instabilities in Ni-Based Single-Crystal Superalloys: Carbide Precipitation and Rayleigh Numbers
The influence of carbide precipitation on grain-defect formation during unidirectional solidification of experimental single-crystal Ni-based superalloys has been assessed over a wide range of compositions with large variations in Re, W, and Ta. In all instances, carbon additions of up to 0.15 wt pct were determined to be statistically significant with respect to stabilizing against the formation of grain defects, such as freckle chains, during solidification. Assessment of the segregation behavior of the constituent alloying additions via a Scheil-type analysis enabled estimation of critical Rayleigh numbers denoting the onset of thermosolutal convection. Precipitation of Ta-rich MC carbides near the liquidus temperature of the alloy was found to interact strongly with the mechanisms associated with freckle formation. Segregation analyses and phase-transformation temperature measurements were used to assess the corresponding Rayleigh numbers for the experimental alloys and to modify the Rayleigh criterion to account for carbide precipitation. Mechanisms pertaining to the interaction of carbides with the onset of thermosolutal convection are discussed.
E0252 – Microstructure effect on the properties of a commercial low-fusing dental porcelain
The aim of this study was to investigate the effect of firing cycle on a dental porcelain microstructure in order to correlate microstructure changes with mechanical and thermal properties. A commercial low-fusing dental porcelain powder (Omega 900, Vita) was investigated for this purpose. The powder was treated at different temperatures in the range 750±1000° C. The fired samples were characterized in terms of their morphology and microstructure, and their mechanical and thermal properties were evaluated. The results showed that firing temperature affects porcelain microstructure influencing significantly in this way both the mechanical properties and the thermal expansion coefficient of the fired objects. Firing at 800° C led to a homogeneous structure. After treatment at this temperature, the leucite crystals exhibit their maximum concentration and they are well dispersed into the glassy phase. As a consequence the optimum mechanical strength and the maximum thermal expansion coefficient are observed in these samples.
E0241 – Structural, dielectric and multiferroic properties of Er and La substituted BiFeO3 ceramics
Erbium (Er) and lanthanum (La) substituted BiFeO3 (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi(0.9–x) La0.1Erx FeO3 (x = 0.05, 0.07 and 0.1) (BLEFOx = 0.05, 0.07,0.1) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFOx = 0.1.
E0251 – Thermal analysis and in vitro bioactivity of bioactive glass–alumina composites
Bioactive glass–alumina composite (BA) pellets were fabricated in the range 95/5–60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 °C. Control
(unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al2O3 can be successfully applied in bioactive glass composites without obstructing their bioactive response
E0250 – Characterization of nanostructured magnetite thin films produced by sol–gel processing
Nanocrystalline films of magnetite have been prepared by a novel sol–gel route in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. Annealing temperature was selected between 291 and 350 °C by DTA analysis in order to obtain magnetite films. In-plane grazing angle XRD and TEM studies showed that magnetite phase was present upon annealing the films at 300 °C. The films had crack free surfaces and
their thicknesses varied between *10 and 200 nm. UV–Vis spectrum results showed that transmittance of the films increases with decreasing annealing temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900–1,100 nm. Vibrating sample magnetometer measurements indicated that magnetite thin films showed ferromagnetic behavior and the saturation magnetization value was found as ~35 emu/cm3.
E0249 – Influence of vermiculite on the formation of porous cordierites
Porous cordierites were prepared from mixtures of talc, kaolinite and vermiculite with alumina or aluminum hydroxide by sintering in an argon atmosphere at 1300 °C for 1 h (porous cordierites of Group I) and 2 h (porous cordierites of Group II). Group I and Group II were different in pore size distribution, quantitative content of mineral phases and cordierite structure parameters. The crystalline phases identified in porous cordierites prepared without vermiculite were cordierite (69–88 vol.%), protoenstatite (25–13 vol.%) and corundum (3–10 vol.%). Vermiculite increased the content of cordierite (84–90 vol.%) and Mg–Al spinel (4–15 vol.%) at the expense of protoenstatite. The calculated unit cell parameters of cordierites were between those of orthogonal and hexagonal cordierites (Group I) and corresponded to disordered orthorhombic rather than hexagonal cordierites (Group II). Group I cordierites had pore size maxima at about ~35 ?m or ~20 ?m, while Group II had maxima at about 35 ?m, 25 ?m and 18 ?m. Porous cordierites prepared fromalumina admixture had slightly lower pore volumes than those prepared fromgibbsite. Cordierites prepared from mixtures rich in vermiculite and gibbsite showed the highest porosity (63% and 57%).
E0259 – Thermodynamic Assessment of the Cu-Fe-O System
The system Cu-F-O was assessed with CALPHAD technique using computerized optimization procedure (PARROT). Two solid phases CuFe2O4 and Fe3O4 forming solid solution at high
temperatures were modeled with compound energy formalism. Presence of Cu1+ on tetrahedral sites in the samples with compositions close to CuFe5O8 reported in the literature was taken into account. The second ternary compound, CuFeO2, was modeled as a stoichiometric phase. For the liquid phase, an ionic two-sublattice model was used. In total 17 adjustable parameters were optimized (9 for the spinel phase, 2 for the delafossite and 6 for the liquid phase) to describe the experimental data. The consistent dataset, which gives a description of the properties from 923 to 1273 K, was obtained.
E0258 – Liquidus Projection and Reaction Scheme of the Co-Al-Nb System
By metallographic observation of the as-cast microstructures, determination of the liquidus temperatures and the temperatures of invariant reactions by differential thermal analysis, and mea-
surement of the compositions of the primary phases and the eutectic residuals by electron probe miroanalysis, a liquidus projection for the Co-Al-Nb systemhas been established for the first time. The binary Co-Nb intermetallic phases have a large solid solubility for Al and their melting temperatures increase markedly by the addition of Al. The only ternary compound, the Heusler
phase NbCo2Al, melts incongruently at about 1485 °C. ByCALPHADmodelling the consistency of the experimental data has been checked. Calculated and experimentally determined temperatures of the invariant reactions are in good agreement and are summarised within a reaction scheme.
E0257 – Phase equilibria in the oxide system Nd2O3-K2O-P2O5
A phase equilibria diagram of the partial system NdPO4-K3PO4-KPO3 has been developed as part of the research aimed at determining the phase equilibriumrelationships in the oxide system Nd2O3-K2O-P2O5. The investigations were conducted using thermoanalytical techniques, X-ray powder diffraction analysis and reflected-light microscopy. Three isopleths existing between: K3Nd(PO4)2-K4P2O7, NdPO4-K5P3O10 and NdPO4-K4P2O7 have been identified in the partial NdPO4-K3PO4-KPO3 system. Previously unknown potassium-neodymium phosphate “K4Nd2P4O15” has been discovered in the latter isopleth section. This phosphate exists in the solid phase up to a temperature of 890°C at which it decomposes into the parent
phosphates NdPO4 and K4P2O7. Four invariant points: two quasi-ternary eutectics, E1 (1057°C) and E2 (580°C) and two quasi-ternary peritectics, P1 (1078°C) and P2 (610°C), occur in the NdPO4-K3PO4-KPO3 region.
E0256 – Phase equilibria in the partial system CePO4–K4P2O7–KPO3
The CePO4–K4P2O7–KPO3 portion of the oxide Ce2O3–K2O–P2O5 system has been investigated using thermoanalytical methods, powder
X-ray diffraction, XPS and IR spectroscopy. The phase diagram with liquidus isotherms and isothermal section at room temperature of the
system CePO4–K4P2O7–KPO3 has been determined. One section, CePO4–K5P3O10, which is quasi–binary only in the subsolidus region (below
560°C), have been found. The system contains one double phosphate K4Ce2P4O15, which exists only in solid state, below 880°C.
E0266 – Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics
Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al2O3, BaTiO3, CaTiO3, TiO2, ZrO2, MgO and SiO2 were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al2O3, BaTiO3, CaTiO3 and MgO samples demonstrated crystalline phases, CaAl2Si2O8, BaAl2Si2O8, CaTiSiO5 and CaMgSi2O6, respectively, as a result of firing at 850 °C. For the sample containing CaTiO3 filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO2. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO2. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.
E0255 – New intermetallic compounds in the Ce–Pt system
The Ce-rich part of Ce–Pt phase diagram has been investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD), optical and electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Two new intermediate phases, Ce5Pt3 and Ce5Pt4, have been discovered and found to crystallize with tetragonal Pu5Pd3-type structure and orthorhombic Ge4Sm5-type structure, respectively. All the Ce-rich compounds of the system were found to crystallize with a peritectic type formation. We have determined the temperatures of the
peritectic plateaus and established the liquidus curves up to 1500°C.
E0265 – A new experimental phase diagram investigation of Cu–Sb
The binary system Cu–Sb is a constituent system that is studied in investigations of technically important ternary and quaternary alloy systems (e.g., casting alloys and lead-free solders). Although this binary system has been thoroughly investigated over the last century, there are still some uncertainties regarding its high-temperature phases. Thus, parts of its phase diagram have been drawn with dashed lines in reviews published in the literature. The aim of this work was to resolve these uncertainties in the current phase diagram of Cu–Sb by performing XRD, SEM-EDX, EPMA, and DTA. The results from thermal analysis agreed well with those given in the literature, although some modifications due to the invariant reaction temperatures were necessary. In particular, reactions located on the Cu-rich side of the nonquenchable high-temperature b phase (BiF3-type) left considerable scope for interpretation. Generally, the structural descriptions of the various binary phases given in the literature were verified. The range of homogeneity of the e phase (Cu3Ti type) was found to be higher on the Sb-rich side. Most of the
reaction temperatures were verified, but a few had to be revised, such as the eutectoid reaction ? ? ? + ? at 440 °C (found to occur at 427 °C in this work) and the eutectoid reaction ? ? (Cu) + ? at 400 °C (found to occur at 440 °C in this work). Further phase transformations that had previously only been estimated were confirmed, and their characteristic temperatures were determined.
The structural and surface stabilities of two experimental ?-Ni+ ?'-Ni3Al-base alloys containing Pt or Ir were investigated. These alloys are representative of alloys currently being developed to
occupy a unique domain with a good combination of high-temperature strength and resistance to oxidation and hot corrosion. Structural characterization included differential thermal
analysis (DTA), transmission synchrotron X-ray analysis, precipitate morphology evolution, phase-partitioning behavior, transmission electron microscopy (TEM), dislocation analysis, and
isothermal precipitate-coarsening behavior. Electron microprobe investigations showed that Pt partitions largely to the ?' phase, while Ir partitions more to the c phase. As a consequence, the
influence of these two elements on the ?-?' lattice-parameter mismatch was quite different. Specifically, synchrotron X-ray analysis confirmed a positive ?-?' misfit in both the Pt- and
Ir-modified alloys in the temperature range 700 °C to 1200 °C; however, the Pt partitioning to the ?' phase resulted in a much larger misfit. The coarsening kinetics of both alloys followed a
cubic time dependence and Pt addition was more effective than Ir in slowing the coarsening rate. Thermodynamic predictions about elemental partitioning and about the solidus, liquidus, and ?' solvus temperatures were made using the software package PANDAT; the results of these predictions were compared with experimental measurements.
E0264 – Possible stibnite transformation at the friction surface of the semi-metallic friction composites designed for car brake linings
After a friction process several changes in phase composition of friction composites are often registered. High temperature, accompanied by high pressure induced during braking can cause initiation of chemical reactions which do not run at room or elevated temperatures under the atmospheric pressure. Most of the studies in the field of tribochemistry at friction surfaces of automotive semi-metallic brake linings deal with phenolic resin degradation and corrosion of metallic components. The paper addresses the formation of elemental antimony as well as the alloying process of iron with antimony observed on the surface of laboratory prepared semi-metallic friction composites containing stibnite. The role of alumina abrasives in the process of stibnite transformation is also discussed and mechanism of stibnite transformation was outlined.
E0253 – Chromia-Assisted Decarburization of W-Rich Ni-Based Alloys in Impure Helium at 1273 K (1000 °C)
The microstructure and surface stability of two experimental W-rich Ni-based alloys have been studied at 1273 K (1000 °C) in an impure-He environment containing only CO and CO2 as
impurities. The alloy Ni-2.3Al-12Cr-12W contained 0.08 wt pct carbon in solution, whereas the second alloy Ni-2.3Al-3Mo-12Cr-12Co-12W contained M6C carbides at the same carbon level.
Both alloys, which were preoxidized with ~2.3 lm Cr2O3 layer, were decarburized completely within 50 hours of exposure to the helium gas mixture at 1273 K (1000 °C) via the following
chromia-assisted decarburization reaction: Cr2O3 (s)+3Calloy (s) fi 2Cr (s)+3CO (g). Microstructural observations, bulk carbon analysis, and microprobe measurements confirmed
that the carbon in solid solution reacted with the surface chromium oxide resulting in the simultaneous loss of chromia and carbon. The Cr produced by the decomposition of the Cr2O3
diffused back into the alloy, whereas CO gas was released and detected by a gas chromatograph. Once the alloy carbon content was reduced to negligible levels, subsequent exposure led to the uninterrupted growth of Cr2O3 layer in both alloys. In the preoxidized alloys, chromia-assisted decarburization rates were slower for an alloy containing carbides compared with the alloy
with carbon in solid solution only. The formation of Cr2O3 is shown to be the rate-limiting step in the chromia-assisted decarburization reaction. Exposure of as-fabricated alloys to the
impure-He environment led to the formation of a thin layer of Al2O3 (<1 lm) between the substrate and surface Cr2O3 oxide that inhibited this decarburization process by acting as a
E0263 – Microsegregation and Secondary Phase Formation During Directional Solidification of the Single-Crystal Ni-Based Superalloy LEK94
A multicomponent phase-field method coupled to thermodynamic calculations according to the CALPHAD method was used to simulate microstructural evolution during directional solidification of the LEK94 commercial single-crystal Ni-based superalloy using a two-dimensional unit cell approximation. We demonstrate quantitative agreement of calculated microsegregation profiles and profiles determined from casting experiments as well as calculated fraction solid curves with those determined in differential thermal analysis (DTA) measurements. Finally, the role of solidification rate on dendrite morphology and precipitation of the secondary phases is investigated and a new measure of the dendrite morphology is presented to quantify the effect of back diffusion on the amount of secondary phases.
E0262 – Application of a modified Pechini method for the synthesis of Ln2MGe4O12 (Ln 5 Y, Eu; M 5 Ca, Zn, Mn) optical hosts
A modified Pechini method followed by conventional and microwave heating was used to synthesise the new promising Ln2MGe4O12 (Ln = Y, Eu; M = Ca, Zn, Mn) optical hosts. Comparison between solid-state and Pechini synthesis methods showed that the latter reduces the temperature required for cyclo-tetragermanate formation. The highest yield of cyclo-tetragermanates for both methods is observed at 1,000–1,100 °C, with significantly shorter time of annealing in the case of the Pechini synthesis. Compositional, structural and morphological characterisations of the samples obtained by both routes were carried out using X-Ray powder diffraction, thermogravimetry, electron spin resonance spectroscopy, energy-dispersive X-Ray spectroscopy and scanning electron microscopy.
E0261 – Phase Equilibria in the Fe-Nb System
A review of the literature revealed that recently published phase diagrams of the Fe-Nb system show considerable discrepancies regarding phase equilibria with the melt and the homogeneity
ranges of the intermetallic phases, specifically of the Laves phase Fe2Nb. Therefore the system has been reinvestigated by metallography, electron probe microanalysis (EPMA), and differ-
ential thermal analysis (DTA). Temperatures of invariant reactions were determined and the homogeneity ranges of the two intermetallic phases, Fe2Nb Laves phase and Fe7Nb6 l phase,
which both exist within a wide composition range, were established.
E0260 – New solid-state glass electrodes by using zinc oxide thin films as interface layer
Novel glass electrodes for the determination of cations with reversible internal solid contact are introduced. They are based on a semiconducting zinc oxide layer with a maximum thickness of 1 ?m in contact with ion selective glasses on one side and with a metal layer on the other side. The metal oxide layer is thereby generated either by ultrasonic spray pyrolysis from zinc acetate solution, by electrochemical deposition from zinc nitrate solution or by spin coating from a dispersion of ZnO in an organic binder. A following activation in a palladiumchloride solution
allows the chemical reductive deposition of NiP as electronic conductor. Dipping-type and flow through electrodes as well as planar glass electrodes in thick film technology fabricated in the above-mentioned method are described. In this case gold electrodes are applied by screen printing on isolated steel substrates. The zinc oxide layers, created in different manners,
are covered afterwards with cation selective glasses in thick film technology. They cause a stabilisation of the half-cell potentials of the all solid state indicator electrodes proved by suitable measurements.
E0270 – Does the degree of pectin esterification influence aluminium sorption by the root apoplast?
This study investigates the influence of the degree of pectin esterification (DE) on the sorption of aluminium (Al) by plant roots. Ca-pectates, with varying degrees of esterification, are major constituents of the soil–root interface and of the root apoplast. Ca-pectate networks (Ca–PG and Ca–Al–PG) were formed at three DEs (0%, 26%, 65%) with custom-made cells and used as a model system for the root cell wall. Sorption of Al was conducted for 24 h at a range of oxalic acid concentrations (0–500 ?M) at pH 4.50 to examine two different metal resistance mechanisms of plants. In fact, plants release organic acids either to desorb or to complex metals to prevent their sorption by plant roots.Thermal analysis showed that Al sorption
did not seem to affect the stability of the pectate gels and the presence of hydrophobic groups (–CH3) at DE>0% seemed to even increase the stability of the gels decreasing thermal decomposition. Results suggest two potential Al tolerance mechanisms: (a) high oxalic acid concentrations (500 ?M) were able to desorb almost 100% and 72% at DE 65 and 0%, respectively; (b) high oxalic acid concentrations (500 ?M) and thus molar ratios of 5:1 (oxalate/Al) reduced Al sorption by 98% and 86% at DE 65 and 0%, respectively. In conclusion, both mechanisms indicate that high degrees of esterification as 65% are much more efficient in excluding Al from the apoplast and might therefore contribute to Al resistance in plants.
E0280 – Thermal studies for preparation of Nb10Hf1Ti Alloy
The aim of this work is to evaluate the feasibility of preparation of Nb10Hf1Ti alloy by magnesiothermic reduction of its oxides. DTA studies were conducted to identify the reduction temperature for coreduction of the mixed oxides of Nb2O5, HfO2, and TiO2 by magnesium under reducing atmosphere. Based on DTA analysis, experiments were carried out to prepare Nb10Hf1Ti alloy by magnesiothermic reduction of their oxides at 750 °C. The reduced product was analyzed for its phases by X-ray diffraction. The excess Mg was leached out, the alloy mixture was vacuum dried, pelletized, sintered, and electron beam melted to get a consolidated alloy of the required composition. The alloy was characterized using different techniques such as optical microscopy, scanning electron microscopy, and chemical analysis. Microstructural observations revealed the formation of coarse grain structure in the consolidated alloy. The alloy product was also evaluated for its micro hardness.
E0269 – Reaction Sequences in the Formation of Silico-Ferrites of Calcium and Aluminum in Iron Ore Sinter
Complex silico-ferrites of calcium and aluminium (low-Fe form, denoted as SFCA; and high-Fe, low-Si form, denoted as SFCA-I) constitute up to 50 vol pct of the mineral composition of fluxed iron ore sinter. The reaction sequences involved in the formation of these two phases have been determined using an in-situ X-ray diffraction (XRD) technique. Experiments were carried out under partial vacuum over the temperature range of T = 22°C to 1215°C (alumina-free compositions) and T = 22°C to 1260°C (compositions containing 1 and 5 wt pct Al2O3) using synthetic mixtures of hematite (Fe2O3), calcite (CaCO3), quartz (SiO2), and gibbsite (Al(OH)3). The formation of SFCA and SFCA-I is dominated by solid-state reactions, mainly in the system CaO-Fe2O3. Initially, hematite reacts with lime (CaO) at low temperatures (T ~ 750 °C to 780 °C) to form the calcium ferrite phase 2CaO.Fe2O3 (C2F). The C2F phase then reacts with hematite to produce CaO.Fe2O3 (CF). The breakdown temperature of C2F to produce the higher-Fe2O3 CF ferrite increases proportionately with the amount of alumina in the bulk sample. Quartz does
not react with CaO and hematite, remaining essentially inert until SFCA and SFCA-I began to form at around T = 1050 °C. In contrast to previous studies of SFCA formation, the current results show that both SFCA types form initially via a low-temperature solid-state reaction mechanism. The presence of alumina increases the stability range of both SFCA phase types, lowering the temperature at which they begin to form. Crystallization proceeds more rapidly after the calcium ferrites have melted at temperatures close to T = 1200 °C and is also faster in the higher-alumina-containing systems.
E0279 – Thermal analysis and SANS characterisation of hybrid materials for biomedical applications
Silicate hybrid materials were prepared by the sol–gel process with the addition of x mass% of zirconium propoxide (x = 0 and 1). The thermal behaviour as well as the influence of Zr addition was studied by thermal gravimetric analysis and differential thermal analysis. The microstructure evolution with temperature was investigated by X-ray diffraction and small-angle neutron scattering. It was found that the beginning of polymer degradation occurs at a higher temperature in the material prepared with addition of Zr than in the one prepared without. At the nanometric scale, the materials prepared without Zr show smooth interfaces, whereas those with Zr present a mass fractal structure. This structure is also observed in the material without Zr after thermal treatment at 200 °C. The results showed that bioactivity is favoured by mass fractal structures in comparison with one consisting of smooth surfaces.
E0268 – Processing, characterisation, and biocompatibility of zinc modified metaphosphate based glasses for biomedical applications
Bulk and structural properties of zinc oxide (0 up to 20 mol%) containing phosphate glasses, developed for biomedical applications, were investigated throughout this study using differential thermal analysis (DTA), differential scanning calorimetry, X-ray powder diffraction and 31P and 23Na MAS NMR. Surface wettability and MG63 viability were also considered for surface characterisation of these glasses. The results indicated that incorporation of zinc oxide as a dopant into phosphate glasses produced a significant increase in density; however,
the thermal properties presented in glass transition, and melting temperatures were reduced. NaZn(PO3)3 was detected in the X-Ray Powder Diffraction Analysis (XRD) trace of zinc containing glasses, and the proportion of this phase increased with increasing zinc oxide content. NaCa(PO3)3 as a second main phase and CaP2O6 in minor amounts were also detected. The 31P and 23Na MAS NMR results suggested that the relative abundances of the Q1 and Q2 phosphorus sites, and the local sodium environment were unaffected as CaO was replaced by ZnO in this system. The replacement of CaO with ZnO did seem to have the effect of increasing the local disorder of the Q2 metaphosphate chains, but less so for the Q1 chain-terminating sites which were already relatively disordered due to the proximity of modifying cations. Glasses with zinc oxide less than 5 mol% showed higher surface wettability, while those with 5 up to 20 mol% showed comparable wettability as zinc oxide free glasses. Regardless of the high hydrophilicity and surface reactivity of these zinc oxide containing glasses, they had lower biocompatibility, in particular 10–20 mol% ZnO, compared to both zinc free glasses and Thermanox1. This may be associated with the release of significant amount of Zn2+ enough to be toxic to MG63.
E0278 – Phase transition temperatures of Sn–Zn–Al system and their comparison with calculated phase diagrams
The Sn–Zn–Al system was studied in connection with the possible substitution of lead-based solders for temperatures up to 350 °C. Ternary alloys with up to 3 wt% of aluminium were prepared. The investigated alloys lie close to the monovariant line (eutectic valley) of the Sn–Zn–Al system. The temperatures of phase transitions of six binary Sn–Zn reference alloys and fourteen ternary Sn–Zn–Al alloys using DTA method were investigated in this paper. DTA experiments were performed at the heating/cooling rate of 4 °C min-1 using Setaram SETSYS 18TM experimental equipment. The temperatures of phase transitions in the ternary Sn–Zn–Al system were obtained, namely, the temperature of ternary eutectic reaction TE1 (197.7 ± 0.7 °C), temperature of ternary transition reaction TU1 (278.6 ± 0.7 °C), temperatures of liquidus and other transition temperatures for studied alloys. Temperatures obtained during DTA heating runs were used as authoritative. DTA curves obtained during cooling enabled realising better differentiation of the obtained overlapped heat effects (peaks) during heating. Theoretical isopleths of the Sn–Zn–Al phase diagram were calculated using the Thermocalc software and MP0602 thermodynamic database. Experimental data were compared with the calculated temperatures, and a good agreement was obtained.
E0267 – Interactions of organic and inorganic chromium species with Ca-polygalacturonate
This study investigated the interactions of CrIII and CrVI present as free metal ions or as organic CrIII (Cr-L) with a Ca-polygalacturonate (Ca-PG) network. Ca-PG networks were treated with solutions of chromium (CrIII and CrVI) at different concentrations at three different pH values. The Cr-L complex were obtained by water extraction of hydrolysed leather. The CrVI had almost no interaction with the Ca-PG networks, whereas CrIII as a free metallic ion was strongly retained by the network. The calculated Langmuir adsorption isotherms showed a twofold increase in maximum CrIII adsorption but a decrease in the affinity of the metal with the Ca-PG networks. This would indicate that the different chromium species, i.e. CrIII and its hydrolytic species, interact in a different way with the polygalacturonate chains. In addition, thermal analysis showed that CrIII sorption modified the structure of the network. These modifications were reduced, and thermal stability increased if Ca-PG adsorbed Cr-L or L. Furthermore, the treatment of Ca-PG with hydrolysed leather water extract-reduced CrIII sorption by 94%. The hydrolysed
leather fraction immobilized onto the Ca-PG networks probably consisted of peptides and could therefore represent an important source of organic N.
E0277 – Experimental study of Fe–C–O based system below 1000 °C
The paper deals with the study of phase transformation temperatures of Fe (Fe–C–O) basedmetallic alloys. Six model alloyswith graded carbon and oxygen contentwere used for experimental investigation. Low-temperature region (<1000 °C) was the investigated area. Phase transformation temperatureswere obtained using Differential thermal analysis and Setaram Setsys 18TM laboratory system. Controlled heating was conducted at the rates of 2, 4, 7, 10, 15, 20 °C min-1. Region of eutectoid transformation (Fe?(C) + Fe3C ? Fe?(C)), alpha–gamma (Fe?(C) ? Fe?(C)) and transformation Fe?(O) + Fe0.92O ? Fe?(O) + Fe0.92O was studied. New original data (phase transformation temperatures) were obtained in this study. The relationship between shift of phase transformation temperatures and chemical composition (mainly carbon and oxygen content) is investigated in this paper. To achieve good approximation to the equilibrium conditions, the extrapolation of the obtained phase transformation temperatures to the zero heating rate was performed. The influence of experimental conditions (heating rate) on temperatures of phase transformations was studied as well. Comparison of the obtained experimental data with the data presented in the accessible literature and IDS calculations (Solidification Analysis Package)was carried out. It follows fromliterature search that there is a lack of thermo-physical and thermo-dynamical data on Fe–C–O system.
The crystallisation kinetics of experimental glasses in 3 different systems: (A) Li2O–SiO2, (B) Li2O–Al2O3–SiO2 and (C) Li2O–K2O–Al2O3–SiO2 were studied under non-isothermal conditions. The DTA results revealed a stronger tendency to crystallisation of binary compositions in comparison to the ternary and quaternary compositions comprising Al2O3 and K2O which present the lower crystallisation, i.e. the crystallisation propensity follows the trend A[B[C. The devitrification process in theLi2O–SiO2 andLi2O–Al2O3–SiO2 systems began earlier and the rate was higher in comparison to that of glasses in the quaternary Li2O–K2O–Al2O3–SiO2 system. Thus, addition of Al2O3 and K2O to glasses of Li2O–SiO2 system was demonstrated to promote glass stability against crystallisation. However, the activation energy for crystallisation was shown to depend also on the SiO2/Li2O ratio with the binary systemshowing a decreasing trendwith increasingSiO2/Li2O ratio,while the opposite tendencywas being observed for compositions with added Al2O3 and K2O.
E0275 – Determination of thermophysical properties of high temperature alloy IN713LC by thermal analysis
The presented paper deals with the study of thermophysical properties of cast and complex alloyed nickel based on superalloy Inconel 713LC (IN713LC). In this work, the technique of Differential Thermal Analysis was selected for determination of the phase transformation temperatures and for the study of the effect of varying heating/cooling rate at these temperatures. The samples taken from as-received state of superalloy were analysed at heating and cooling rates of 1, 5, 10, 20 and 50°C min-1 with the help of the experimental system Setaram SETSYS
18TM. Moreover, the transformation temperatures at zero heating/cooling rate were calculated. The recommended values for IN713LC after correcting to a zero heating rate, are 1205°C (Tc0,solvus), 1250°C (solidus) and 1349°C (liquidus). Influence of heating/cooling rate on shift of almost all temperatures of phase transformations was established from the DTA curves. Undercooling was observed at the cooling process. T
E0274 – Experimental study of Fe–C–O based system below 1000°C
The paper deals with the study of phase transformation temperatures of Fe (Fe–C–O) based metallic alloys. Six model alloys with graded carbon and oxygen content were used for experimental investigation. Low-temperature region (1000°C) was the investigated area. Phase transformation temperatures were obtained using Differential thermal analysis and Setaram Setsys 18TM laboratory system. Controlled heating was conducted at the rates of 2, 4, 7, 10, 15, 20°Cmin-1. Region of eutectoid transformation (Fe?(C) + Fe3C ? Fe?(C)), alpha–gamma (Fe?(C) ? Fe?(C)) and transformation Fe?(O) + Fe0.92O ? Fec(O) + Fe0.92O was studied. New original data (phase transformation temperatures) were obtained in this study. The relationship between shift of phase transformation temperatures and chemical composition (mainly carbon and oxygen content) is investigated in this paper. To achieve good approximation to the equilibrium conditions, the extrapolation of the obtained phase transformation temperatures to the zero heating rate was performed. The influence of experimental conditions (heating rate) on temperatures of phase transformations was studied as well. Comparison of the obtained experimental data with the data presented in the accessible literature and IDS calculations (Solidification Analysis Package) was carried out. It follows from literature search that there is a lack of thermo-physical and thermo-dynamical data on Fe–C–O system.
E0273 – Phase transition temperatures of Sn–Zn–Al system and their comparison with calculated phase diagrams
The Sn–Zn–Al system was studied in connection with the possible substitution of lead-based solders for temperatures up to 350 C. Ternary alloys with up to 3 wt% of aluminium were prepared. The investigated alloys lie close to the monovariant line (eutectic valley) of the Sn–Zn–Al system. The temperatures of phase transitions of six binary Sn–Zn reference alloys and fourteen ternary Sn–Zn–Al alloys using DTA method were investigated in this paper. DTA experiments were performed at the heating/cooling rate of 4 C min-1 using Setaram SETSYS 18TM experimental equipment. The temperatures of phase transitions in the ternary Sn–Zn–Al system were obtained, namely, the temperature of ternary eutectic reaction TE1 (197.7 ± 0.7 C), temperature of ternary transition reaction TU1 (278.6 ± 0.7 C), temperatures of liquidus and other transition temperatures for studied alloys. Temperatures obtained during DTA heating runs were used as authoritative. DTA curves obtained during cooling enabled realising better differentiation of the obtained overlapped heat effects (peaks) during heating. Theoretical isopleths of the Sn–Zn–Al phase diagram were calculated using the Thermocalc software and MP0602 thermodynamic database. Experimental data were compared with the calculated temperatures, and a good agreement was obtained.
E0272 – Synthesis and Sintering of Bi2Ti4O11
The conditions of Bi2Ti4O11 formation are studied. It is shown that the process is diffusion-controlled and depends significantly on the heating rate. The optimal conditions for producing Bi
2Ti4O11 ceramics are determined. Cold pressing of Bi2Ti4O11 ceramic powder at high pressures is shown to influence the unit-cell parameters and volume, positional parameters of Bi and Ti, and bond distances in the ferroelectric ceramics produced by subsequent sintering. The ferroelectric transition temperature decreases steadily with increasing densification pressure.
E0271 – Stabilization of Thermosolutal Convective Instabilities in Ni-Based Single-Crystal Superalloys: Carbon Additions and Freckle Formation
The effect of carbon additions on the solidification characteristics of single-crystal Ni-based superalloys has been studied over a range of composition with large variations in Re, W, and Ta. Under constant processing conditions, nominally similar experimental alloys containing additions of 0.1 wt pct C exhibited a decreased tendency to develop grain defects, such as freckle chains. The carbon additions resulted in the formation of Ta-rich MC carbides with three distinct morphologies: blocky, nodular, and script. These carbides all precipitate near the liquidus temperature of the alloy. Intentional carbon additions also affected the segregation behavior of the constituent elements. Comparison of experimentally measured distribution coefficients assessed via application of a Scheil-type analysis revealed reduced segregation of Re,W, and Ta in experimental single-crystal alloys containing carbon. The mechanisms by which carbon additions influence freckle formation are considered.
E0281 – Isothermal section of the Er–Cu–Ga ternary system at 973 K
Phase relations in the Er–Cu–Ga ternary system have been established at 973 K by means of powder X-ray diffraction complemented by energy dispersive spectroscopy coupled to scanning electron microscopy. The isothermal section of the phase diagram comprises eight extensions of binaries into the ternary system, ErCu1?xGax (x ? 0.5), ErCu2?xGax (x ? 1.1), ErCu5?xGax (x ? 0.5), Er5CuxGa3?x (x ? 0.60), Er3CuxGa2?x (x ? 0.24), ErCuxGa1?x (x ? 0.10), ErCuxGa2?x (x ? 0.30) and ErCuxGa3?x (x ? 0.35), as well as six ternary intermediate phases, ErCuxGa2?x (0.4 ? x ? 0.7), Er14Cu51?xGax (5.5 ? x ? 11.0), ErCu5?xGax (0.8 ? x ? 2.3), Er2Cu17?xGax (4.9 ? x ? 8.0), ErCu12?xGax (5.7 ? x ? 6.7) and Er3CuxGa11?x (1.5 ? x ? 4.4), all deriving from binary structure-types.
E0291 – Structural and thermal characterization of CaO–MgO–SiO2–P2O5–CaF2 glasses
The influence of varying the CaO/MgO ratio on the structure and thermal properties of CaO–MgO–SiO2–P2O5–CaF2 glasses was studied in a series of eight glass compositions in the glass forming region of diopside (CaMgSi2O6)–fluorapatite [Ca5(PO4)3F]–wollastonite (CaSiO3) ternary system. The melt-quenched glasses were characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus tends to coordinate in orthophosphate environment. The sintering and crystallization parameters of the glasses were obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass–ceramics were analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite crystallized as the main crystalline phases in all the glass–ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. The implications of structure and sintering behaviour of glasses on their bioactivity were discussed.
E0290 – Apatite-structured compounds: Synthesis and high-temperature investigation
The phase transitions and thermal expansion of apatite-structured compounds with the general formula MII5(AVO4)3L (MII = Ca, Sr, Cd, Ba, Pb; AV = P, V, Cr, Mn; L = OH, F, Cl, Br, I) have been studied by high-temperature X-ray diffraction and differential thermal analysis. Polymorphic transition nature was explained on the basis of the structure data. Connection between thermal stability and peculiarities of thermal expansion, which were explained in assumption of composition and structure of apatites was ascertained.
E0289 – Phase relations in the ZrO2–Nd2O3–Y2O3–Al2O3 system: Experimental study and thermodynamic modeling
The Nd2O3–Al2O3 and ZrO2–Nd2O3–Al2O3 systems were simultaneously re-assessed to reproduce experimental data from present study and literature. Phase relations in the Nd2O3–Y2O3–Al2O3 system were investigated by XRD, electron microscopy and DTA for the first time. Invariant reaction in solid phases B + YAM = NdAlO3 + C was determined to occur at 1863 K. The eutectic reaction liquid = YAG + NdAlO3 + Al2O3 was determined to occur at 2042 K and composition Al2O3–10 mol.% Nd2O3–13 mol.% Y2O3. The obtained data were used to assess thermodynamic parameters of this system. Isothermal sections were calculated in the range 1523–1923 K. Liquidus surface of the Nd2O3–Y2O3–Al2O3 system was calculated. The derived databases were combined with already available descriptions of the ZrO2–Nd2O3–Y2O3 and ZrO2–Y2O3–Al2O3 systems into four-oxide database.
E0299 – New types of lead-free solders on the base of tin and their properties
The aim of the work is an experimental study of binary, ternary and quaternary systems on the base of tin alloys. 22 alloys with different ratios of individual elements Ag, Cu, In, Sb,
Bi, and Sn were prepared experimentally. In addition, 6 alloys of lead-free solders produced commercially (Kovohut? P?íbram nástupnická, a.s.) were used and the Pb-Sn solder served as
a comparative etalon. The following characteristics were studied: temperatures and enthalpies of phase transformations (DTA, TG, DSC) of individual solders at the rates of re-heating and
cooling of specimens of about 4?Cmin?1, microstructural analysis (optical metallography) and microhardness of specimens, chemical analysis, microanalysis of individual phases in the
structure of solders (WDX, EDX), measurement of surface tension and density of solders in dependence on the temperature, test of wettability with or without use of fluxes, measurement
of corrosion properties, measurement of electrical resistivity
E0288 – Correlation between structure and photoluminescence of the europium doped glaserite-type phosphate Na2SrMg(PO4)2
A new phosphate Na2SrMg(PO4)2 has been synthesized and investigated by X-ray diffraction, DTA, 31P NMR spectroscopy and photoluminescence measurements. This compound crystallizes in the space group P21/a of the monoclinic system with the cell parameters: a = 9.158(1) Å, b = 5.267(1) Å, c = 13.498 (1) Å, ? = 90.01(1)° and four formula units per cell. Its structure is closely related to that of the mineral glaserite K3Na(SO4)2 and thus it can be described by the general formula XY2M(TO4)2. The X, Y, M and T sites are fully occupied by Sr2+, Na+, Mg2+ and P5+ cations, respectively. The anionic framework is consisted by the stacking along the  direction of two kinds of alternating [MgP2O84?]? mixed layers parallel to the (a, b) plane and resulting from a corner-sharing between MgO6 octahedra and PO4 tetrahedra. The Sr2+ cations are located within the interlayer space, while those Na+ are found in large cavities bounded to the layers. The DTA analysis showed a congruent melting of this compound at 1374 K. The 31P NMR spectroscopy confirmed the presence of two distinct phosphors sites in the structure. Optical studies were performed on the Na2SrMg(PO4)2 compound doped with Eu3+ and Eu2+. The trivalent europium was used as a local probe, replacing strontium and sodium, what gives complementary and consistent results to the crystallographic analyses. The divalent europium was used to analyze preliminary the potentiality for this compound to be integrated as phosphor in Light Emitting Diode (LED).
E0298 – Study of physical and mechanical applications on ceramics of the lateritic and alluvial clayey mixtures of the Yaoundé region (Cameroon)
Ceramic products were prepared by mixing lateritic and alluvial clayey materials of Yaoundé (Cameroon) in the humid tropical region, with 20, 50 and 80 wt.% of alluvial clay respectively in lateritic clay. Samples were grounded and sieved and powders obtained were shaped by uniaxial pressing of wet granules and fired under low temperatures between 350 and 1050 °C. Open porosity, bulk density and flexural strength were the principal properties characterised. Results indicates that a maximum of 80 wt.% of alluvial clayey material must be added to lateritic clays of Yaoundé, to obtain weakly porous ceramics and to attain the bulk density ranging from 1.56 to 1.97 g/m3 and a flexural strength of 6–19.85 MPa would be equivalent alluvial clay ceramics. But ceramics with lesser amount of alluvial clayey materials also have interesting flexural strengths in the range of 5–16 MPa, thus higher than porous lateritic clay ceramics.
E0287 – Investigations of the non-isothermal crystallization of Bi4Ge3O12 (2:3) glasses
Amorphous Bi4Ge3O12 glass samples were produced by melt quenching procedure stating with Bi4Ge3O12 (BGO) powder, obtained by solid state reaction between oxides. The kinetics of non-isothermal crystallization of BGO nano-crystals has been investigated. Differential Thermal Analysis (DTA) can give the main parameters of crystallization with an exothermic peak from 813 K to 851 K depending on the heating rate, which was assigned to the crystallization of cubic BGO in the amorphous matrix and compared with the X-Ray Diffraction (XRD) patterns. The nano-crystal dimensions were calculated from the XRD patterns by using the Debye–Scherrer method and were compared with Transmission Electron Microscopy (TEM) images. It was shown that the Ozawa model is most suitable for describing the behavior of non-isothermal crystallization of BGO nano-crystals within the glass matrix. Experimental results suggest a disk-shape type growth mechanism for the Bi4Ge3O12 nano-crystallites. The Flynn–Wall–Ozawa method has shown that the average activated energy value is 385 ± 14 kJ/mol which was computed within the same model and agrees very well with the activation energy of the crystallization.
E0297 – Characteristic free volume change of bulk metallic glasses
The free volume change ?Vf(T) of bulk metallic glasses (BMGs) relative to a hypothesized amorphous reference state was measured using the thermal dilatation method. The characteristic free volume change, i.e., the free volume released in structural relaxation ?Vf-sr, was identified quantitatively from the ?Vf(T) curve. For a Fe-based BMG, it was found that ?Vf-sr increases with decreases in the sample diameter and heating rate. ?Vf-sr measured under the same sample diameter and heating rate conditions allowed the convenient comparison of different BMGs. The comparison revealed that the glass-forming ability (GFA) enhancement of each of two Pd-, Mg-, Cu-, Zr-, Ti-, and Fe-based BMGs can be sensitively reflected in the decrease in ?Vf-sr and the narrowing of the difference between the peak temperature of the thermal expansion coefficient and the end temperature of the glass transition process. In addition, for these twelve typical BMGs, there is a good linear relationship between ?Vf-sr and LogDc2 or LogDc, where Dc is the critical diameter. ?Vf-sr is thus sensitive to and has a close correlation with GFA. Furthermore, the ?Vf-sr measurement results are in good agreement with the free volume change measured with the specific heat capacity, room temperature density, and positron annihilation lifetime methods. In the study of the relationship between the structure and properties of BMGs, ?Vf-sr thus plays an important role given its comparability and convenience.
E0286 – The microstructure of erbium–ytterbium co-doped oxyfluoride glass–ceramic optical fibers
Oxyfluoride transparent glass–ceramics combine some features of glasses (easier shaping or lower than single crystals cost of fabrication) and some advantages of rare-earth doped single crystals (narrow absorption/emission lines and longer lifetimes of luminescent levels). Since the material seems to be promising candidate for efficient fiber amplifiers, the manufacturing as well as structural and optical examination of the oxyfluoride glass–ceramic fibers doped with rare-earth ions seems to be a serious challenge. In the first stage oxyfluoride glasses of the following compositions 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–11PbF2–3ErF3 and 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–10PbF2–3YbF3–1ErF3 (in molar%) were fabricated from high purity commercial chemicals (Sigma–Aldrich). The fabricated glass preforms were drawn into glass fibers using the mini-tower. Finally, the transparent Er3+ doped and Er3+/Yb3+ co-doped oxyfluoride glass–ceramic fibers were obtained by controlled heat treatment of glass fibers. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. X-ray diffraction examination (XRD) at each stage of the glass–ceramic fibers fabrication confirmed the undesirable crystallization of preforms and glass fibers has been avoided. The fibers shown their mixed amorphous–crystalline microstructure with nano-crystals of size even below 10 nm distributed in the glassy host. The crystal structure of the grown nano-crystals has been determined by XRD and confirmed by electron diffraction (SAED). Results obtained by both techniques seem to be compatible: Er3FO10Si3 (monoclinic; ICSD 92512), Pb5Al3F19 (triclinic; ICSD 91325) and Er4F2O11Si3 (triclinic; ICSD 51510) against to initially expected PbF2 crystals
E0296 – Microstructure, geotechnical and mechanical characteristics of quicklime-lateritic gravels mixtures used in road construction
Microstructure of quicklime-lateritic gravels mixes, containing up to 8 wt.% quicklime, was investigated by using X-ray diffraction, infrared spectrometry, differential thermal analysis, scanning electron microscopy and energy dispersive spectrometry. Geotechnical and mechanical properties of the mixtures were also measured. Quicklime additions resulted of reduction of clayey fraction, plasticity index, methylene blue value and maximum dry density and the increasing of optimum moisture content. The results showed also that quicklime admixtures resulted in the formation of calcium silicate hydrate type I (C–S–H (I)), portlandite and calcite. This CSH (I) was formed through the pozzolanic reaction between a part of the kaolinite and hydrated lime in the basic medium. Moreover, C–S–H (I) marked crystallization with curing time and observed for the quicklime amounts (?3 wt.%), contributed to the improvement of mechanical properties. These lime modified lateritic gravels are convenient for base course in road geotechnical applications.
E0285 – Effects of addition of nitrogen on bioglass properties and structure
Bioglasses have been developed for use in surgery because of their ability to form a hydroxy-carbonate apatite (HCA) layer on their surface which facilitates bonding to natural bone. However, they do not have sufficient strength for use in load-bearing situations and therefore improving their mechanical properties would allow their use in more robust applications. The purpose of this work was to study the effects of nitrogen addition on the physical and mechanical properties and the structure of oxynitride bioglasses based on the system Na2O–CaO–SiO2–Si3N4. The density, glass transition temperature, hardness and elastic modulus were measured and observed to increase linearly with nitrogen content. These increases are consistent with the incorporation of N into the glass structure in three-fold coordination with silicon which results in extra cross-linking of the glass network. The characterization of these oxynitride bioglasses using solid state nuclear magnetic resonance 29Si MAS NMR and infrared spectroscopy have shown firstly that all the N atoms are bonded to Si atoms and secondly that this increase in rigidity of the glass network can be explained by the formation of SiO3N, SiO2N2 tetrahedra and Q4 units with extra bridging anions at the expense of Q3 units. The oxynitride bioglasses in simulated body fluid form a hydroxy-carbonate apatite (HCA) layer on their surfaces showing that bioactivity is retained
E0295 – Phase equilibria in the system NaAl(WO4)2–NaCr(WO4)2
The phase equilibria in the system NaAl(WO4)2–NaCr(WO4)2 are investigated. Nanopowders are synthesized in the whole concentration region from NaAl(WO4)2 to NaCr(WO4)2 by a co-precipitation method. Using X-ray, DTA, TEM and SEM analyses, three concentration regions in the system are established: single-phase region of NaAl1??Cr?(WO4)2 solid solutions (x is between 0 and 0.08), with monoclinic structure, space group C2/c; single-phase region of NaAl1??Cr?(WO4)2 solid solutions (x is between 0.40 and 1.0) with monoclinic structure, space group P2/c; and two-phase region, where the above mentioned phases crystallize simultaneously (x is between 0.08 and 0.40). The thermal behaviour of the two pure boundary phases, as well as the influence of chromium on the thermal stability and the structural characteristics of the solid solutions are discussed.
E0284 – Crystallization characteristics of La2O3-containing glasses for glass ionomer cement
Glasses with general formula 4.5SiO2 ? 3Al2O3 ? 1.5P2O5?(2.5 ? x)CaO ? xLa2O3 ? 2.5CaF2 (x = 0.0–1.0) for glass ionomer cement have been prepared by conventional melting and water quenching. The influence of substitution of La2O3 for CaO on glass transition temperature (Tg), setting time and crystallization was studied. An increase in La2O3/CaO ratio shifted Tg to higher temperature. Fluorapatite (Ca5(PO4)3F), mullite (3Al2O3 ? 2SiO2), lanthanum aluminum silicate solid solution, and anorthite (CaO ? Al2O3 ? 2SiO2) were identified by XRD in the heat-treated materials; then, their formation was dependent on glass composition and heat-treatment temperature. After heat-treating at 750 °C with glass samples of La2O3/CaO = 0, 0.25 (molar ratio), only fluorapatite phase was precipitated; however, anorthite was additionally formed at 950 and 1050 °C. With further increasing La2O3/CaO ratio and/or heat-treatment temperature, lanthanum aluminum silicate solid solution existed as the major phase
E0294 – Nanosized pure and Cr doped Al2?xInx(WO4)3 solid solutions
For a first time are synthesized nanosized solid solutions with formula Al2?xInxCry(WO4)2 (x = 0–2, y = 0.02–0.1). Co-precipitation method is used for the synthesis. It is established that only by strict maintenance of pH between 2.7 and 2.9 a pure, monophase product of In2(WO4)3 can be obtained. By X-ray powder diffraction and DTA/TG analyses, it is established that at room temperature the solid solutions Al2?xInx(WO4)2 at x value between 0 and 1.1 are orthorhombic and for x value between 1.1 and 2.0 are monoclinic. The phase transition temperatures are defined for different x values. Results from X-ray and TEM analyses show that nanosized pure Al2?xInx(WO4)2 and Cr-doped Al2?xInxCry(WO4)2 with size dimension between 10 and 40 nm can be successfully synthesized by co-precipitation method with subsequent thermal treatment at relatively low temperature (550 °C) for 1 h.
E0283 – The role of K2O on sintering and crystallization of glass powder compacts in the Li2O–K2O–Al2O3–SiO2 system
The effects of K2O content on sintering and crystallization of glass powder compacts in the Li2O–K2O–Al2O3–SiO2 system were investigated. Glasses featuring SiO2/Li2O molar ratios of 2.69–3.13, far beyond the lithium disilicate (LD-Li2Si2O5) stoichiometry, were produced by conventional melt-quenching technique. The sintering and crystallization behaviour of glass powders was explored using hot stage microscopy (HSM), scanning electron microscopy (SEM), differential thermal (DTA) and X-ray diffraction (XRD) analyses. Increasing K2O content at the expense of SiO2 was shown to lower the temperature of maximum shrinkage, eventually resulting in early densification of the glass-powder compacts. Lithium metasilicate was the main crystalline phase formed upon heat treating the glass powders with higher amounts of K2O. In contrast, lithium disilicate predominantly crystallized from the compositions with lower K2O contents resulting in strong glass–ceramics with high chemical and electrical resistance. The total content of K2O should be kept below 4.63 mol% for obtaining LD-based glass–ceramics.
E0293 – Alkali-free bioactive glasses for bone tissue engineering: A preliminary investigation
An alkali-free series of bioactive glasses has been designed and developed in the glass system CaO-MgO-SiO(2)-P(2)O(5)-CaF(2) along the diopside (CaMgSi(2)O(6))-fluorapatite (Ca(5)(PO(4))(3)F)-tricalcium phosphate (3CaO·P(2)O(5)) join. The silicate network in all the investigated glasses is predominantly coordinated in Q(2) (Si) units, while phosphorus tends to remain in an orthophosphate (Q(0)) environment. The in vitro bioactivity analysis of glasses has been made by immersion of glass powders in simulated body fluid (SBF) while chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Some of the investigated glasses exhibit hydroxyapatite formation on their surface within 1-12 h of their immersion in SBF solution. The sintering and crystallization kinetics of glasses has been investigated by differential thermal analysis and hot-stage microscopy, respectively while the crystalline phase evolution in resultant glass-ceramics has been studied in the temperature range of 800-900°C using powder X-ray diffraction and scanning electron microscopy. The alkaline phosphatase activity and osteogenic differentiation for glasses have been studied in vitro on sintered glass powder compacts using rat bone marrow mesenchymal stem cells. The as-designed glasses are ideal candidates for their potential applications in bone tissue engineering in the form of bioactive glasses as well as glass/glass-ceramic scaffolds
E0282 – Effect of K2O on structure–property relationships and phase transformations in Li2O–SiO2 glasses
Glass compositions with formula (71.78 ? x)SiO2–2.63Al2O3–(2.63 + x)K2O–23.7Li2O (mol.%, x = 0–10) and SiO2/Li2O molar ratios far beyond that of stoichiometric lithium disilicate (Li2Si2O5) were prepared by conventional melt-quenching technique to investigate the influence of K2O content on structural transformations and devitrification behaviour of glasses in the Li2O–SiO2 system. The scanning electron microscopy (SEM) examination of as cast non-annealed glasses revealed the presence of nanosized droplets in glassy matrices suggesting occurrence of liquid–liquid phase separation. An overall trend towards depolymerization of the silicate glass network with increasing K2O content was demonstrated by employing magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopy. The distribution of structural units in the experimental glasses was estimated using 29Si MAS-NMR spectroscopy suggesting the appearance of Q2, enhancement of Q3 and diminishing of Q4 groups with increasing K2O contents. X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to assess the influence of K2O on devitrification process and formation of lithium disilicate (Li2Si2O5) and/or lithium metasilicate (Li2SiO3) crystalline phases.
E0292 – Crystallization kinetics, stability and glass forming ability of iron phosphate and cesium loaded iron phosphate glasses
The activation energy of crystallization of iron phosphate glass (IPG) as a function of the fraction of crystallization was evaluated by Kissinger–Akahira–Sunose isoconversional method utilizing crystallization curves obtained from differential thermal analysis (DTA). The crystallization products were identified by using X-ray diffraction technique. Similar crystallization kinetic studies were carried out on IPG loaded with 5.5 mol% Cs2O. The glass stability and glass forming ability of IPG and various cesium loaded IPG were also estimated in terms of the characteristic temperatures obtained from DTA. The characteristic temperatures include glass transition, crystallization and liquidus temperature. The glass forming ability is correlated with the evaluated critical cooling rate of the glasses
E0302 – Is Tl2Ni3S2 a mixed valent compound? Crystal and electronic structure investigations
The crystal and electronic structure of Tl2Ni3S2 is investigated by X-ray structure determination and DFT calculations. The question of charges and possible mixed valences of two different Tl positions in Tl2Ni3S2 is discussed with respect to crystal and electronic structure arguments. Crystal structure parameters were redetermined from single crystal data. A relation is given to typical Tl states in reference compounds like mixed valent Tl2S2, high-pressure TlS, LiTl, and ThCr2Si2 type TlNi2S2. This allows for a comparison of different Tl sites with respect to atomic distances, coordinations, valence, charge, and bonding as well as charge redistribution within layered Ni–S substructures. Complementary methods of charge determination from theory are applied as orbital analysis from precise full potential calculations and charge density analysis by zero flux surface integration according to the AIM theory.
E0312 – Microstructures and mechanical properties of Fe-Al-Ta alloys with strengthening Laves phase
The addition of Ta to Fe–Al alloys results in the formation of a stable Ta(Fe,Al)2 Laves phase with hexagonal C14 structure in the Fe–Al phase at temperatures of 800, 1000 and 1150 °C. It was found that the solubility of Ta in Fe–Al is generally low and the solubility of Ta varies with Al content. Respective isothermal sections of the Fe–Al–Ta system have been established. Particular attention has been given to precipitation in the Fe3Al phase with a small addition of Ta. At intermediate temperatures, 600–750 °C, an additional Heusler-type phase with L21-structure precipitates, which transforms at longer times and high temperatures to the stable C14 Laves phase. The yield stress in compression and the creep behaviour of the Fe–Al–Ta alloys with various microstructures were studied. Due to the presence of the L21-Heusler phase, the yield stress and the creep resistance at temperatures below 700 °C was increased considerably
E0301 – Compositional effects on the properties of high nitrogen content alkaline-earth silicon oxynitride glasses, AE = Mg, Ca, Sr, Ba
A series of alkaline-earth element containing high nitrogen content oxynitride glasses (AESiON), with AE = Mg, Ca, Sr, Ba, were prepared in order to investigate the compositional effects on the physical properties of the alkaline-earth element. The physical properties were found to change linearly with the concentration of AE elements. The density of the glasses increases substantially with an increase in the AE atomic mass and slightly with an increase in nitrogen ratio. Ba containing glasses shows the value of density 4.16 g/cm3. Glass transition temperatures are found to be higher for Mg glasses, ca. 1020 °C, in comparison with Ba glasses, ca. 895 °C. The hardness of Mg containing glasses shows high values, up to 12.2 GPa and decreases for Ca, Sr and Ba containing glasses. Ba, containing glasses shows high values of refractive index in comparison with the Sr, Ca and Mg containing glasses.
E0311 – Phase equilibria in the Al-Mo-Si system
The ternary Al–Mo–Si phase diagram was investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA), electron probe microanalysis (EPMA) and scanning electron microscopy (SEM). Ternary phase equilibria were investigated within two isothermal sections at 600 °C for the Mo-poor part and 1400 °C for the Mo-rich part of the phase diagram. The solubility ranges of several phases including MoSi2 (C11b) as well as Mo(Si,Al)2 with C40 and C54 structure were determined. The binary high temperature phase Al4Mo was found to be stabilized at 600 °C by addition of Si. DTA was used to identify 9 invariant reactions and thus constructing a ternary reaction scheme (Scheil diagram) in the whole composition range. A liquidus surface projection was constructed on basis of the reaction scheme in combination with data for primary crystallization from as-cast samples determined by SEM measurements.
E0300 – Self-flux growth of large EuCu2Si2 single crystals
Large single crystals of the EuCu2Si2 intermetallic compound have been successfully grown by a high pressure vertical floating zone method with optical heating. The suppression of evaporation of volatile elements and control of the floating zone temperature are the key factors for the stability of the growth process. A low travelling velocity of 3 mm/h and a short length of the floating zone play an important role in phase selection and formation of a EuCu2Si2 single crystal. Measurements of oriented single crystalline EuCu2Si2 samples reveal a non-linear temperature dependence of the magnetic susceptibility attributed to the valence fluctuations in Eu ion. But no magnetic ordering transition occurs at T>2 K. The magnetic susceptibility data display significant anisotropy with a magnetic easy c-axis ([0 0 1]). In contrast to the magnetic susceptibility, the anisotropy in the electrical resistivity for the two different crystallographic orientations is less significant.
E0310 – Re-investigation of phase equilibria in the system Al-Cu and structural analysis of the high-temperature phase ?1-Al(1 ?)Cu
The phase equilibria and reaction temperatures in the system Al–Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase ?1 and the low temperature phase ?2 thus indicating a first order transition. In the ?1/?2 region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between ? and ?1 is very narrow. The results of the current work indicate the absence of the high temperature ?0 phase as well as the absence of a two phase field between ?1 and ?0 suggesting a higher order transition between ?1 and ?0. The structure of ?0 (I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase ?1-Al1??Cu. The phase is orthorhombic (space group Cmmm) and the lattice parameters are a = 4.1450(1) Å, b = 12.3004(4) Å and c = 8.720(1) Å; atomic coordinates are given.
E0309 – Enhancement of cells proliferation and control of bioactivity of strontium doped glass
Bioactivity and chemical reactivity of bioactive glass offer the ability to bond for soft and hard biological tissues. In this work, synthesis was carried out by using melting and rapid quenching. Strontium was introduced as trace element at different contents in the glass matrix, according to its concentration in the bone matrix. This chemical element presents a high interest in the bone metabolism activity. Investigations were conducted on the surface of biomaterials by using in vitro assay after immersion in SBF. Several physico-chemical methods such as SEM, FTIR, NMR, ICP-OES and MTT test were employed to highlight the effects of the Sr. The in vitro experiments showed that after soaking in SBF, the behaviour of pure glass is different compared to glass doped with Sr. NMR analyses showed in the 29Si MAS-NMR that glass matrix undergoes some changes after in vitro assays particularly the emergence of new components attributed to Q3(OH). The presence of Sr slowed down the bioactivity of glass after immersion in SBF. The non toxic character of compounds was confirmed. Introduction of Sr at 0.1 wt % induce an enhancement of cells at about 14.3%.
E0308 – Constitutional and microstructural investigation of the pseudobinary NiAl-W system
Pseudobinary NiAl–W section in the range 0.7–1.8 at% was characterised regarding solidification microstructure and constitution. The existence of eutectic reaction was confirmed and occurs at temperature of 1664 ± 2 °C and the composition of 1.5 at% W. As-cast microstructures indicated that the NiAl–W system is an anomalous eutectic with skewed coupled zone and that the NiAl phase is a preferential phase for eutectic nucleation. Directionally solidified alloy containing 1.5 at% W exhibited entirely eutectic structure characterised by eutectic cells with the average value of 500 ?m, interfibre spacing 3.5 ?m, fibre diameter 300 nm, and volume fraction of the W phase 1.4%. The solubility of W in the intermetallic phase is <0.04 at% and the solubility of Ni and Al in the W phase is negligible. Crystallographic orientation between the constituent phases was established to be cube on cube. Based on the results obtained by DTA, microstructural and compositional analysis, a new isoplethal section NiAl–W of the ternary Al–Ni–W system has been proposed.
E0307 – Phase equilibria in the AleSieV system: The vanadium rich part
The V-rich part of the Al–Si–V phase diagram was determined by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe microanalysis (EPMA). Phase equilibria were investigated at two isothermal sections at 850 and 1300 °C. High temperature DTA was performed to identify the ternary invariant reactions yielding a ternary reaction scheme and the vertical section at 50 at.% V. As cast samples were investigated in order to gain additional information about primary crystallization fields. A liquidus surface projection was constructed for the entire ternary system by combining our experimental data with those from literature.
E0306 – Influence of strontium on structure, sintering and biodegradation behaviour of CaO–MgO–SrO–SiO2–P2O5–CaF2 glasses
The present study investigates the influence of SrO on structure, apatite-forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with the composition (mol.%): (36.07 ? x) CaO–xSrO–19.24MgO–5.61P2O5–38.49SiO2–0.59CaF2, where x varies between 0 and 10. The detailed structural analysis of the glasses is made by infrared spectroscopy and magic angle spinning–nuclear magnetic resonance spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus is found as orthophosphate in all the investigated glasses. The apatite-forming ability of glasses is investigated by immersion of glass powders in simulated body fluid for time durations varying between 1 h and 7 days. While increasing the Sr2+/Ca2+ ratio in the glasses does not affect their structure significantly, their apatite-forming ability is decreased considerably. Further, physico-chemical degradation of glasses is studied in accordance with ISO 10993-14 “Biological evaluation of medical devices – Part 14: Identification and quantification of degradation products from ceramics” in Tris–HCl and citric acid buffer, and the possible implications of the ion release profiles from the glasses in different solutions are discussed. The addition of strontium to the glasses leads to a sevenfold decrease in chemical degradation of glasses in Tris–HCl. The sintering of glass powders renders glass ceramics (GCs) with varying degrees of crystallinity and good flexural strength (98–131 MPa), where the mechanical properties depend on the nature and amount of crystalline phases present in the GCs.
E0305 – Size ratio induced yttrium aluminum garnet formation characteristics in nano-scaled Y2O3–Al2O3 powder systems via fast firing processes
The formation characteristics of YAG phase synthesized by fast-firing Y2O3 and Al2O3 powder mixtures were examined. Y2O3 powders of 100, 350, and 500 nm in D50 were mixed with ?-Al2O3 powder of (D50) 200 nm to obtain starting powders denoted as S0.5, S1.75, and S2.5, respectively. In these mixtures, the two oxides contacted wholly with each other but varied in number of contact points and diffusion length. This study aimed to eliminate the YAM and YAP phases, which normally occur during YAG formation. Examinations were conducted using pressed compacts (bulk density of 0.91 g cm?3) prepared with the three mixtures. After pre-heating at 700 °C for 30 s, the compacts were plunged at temperatures of 1050–1450 °C for 5–60 s and then quenched to room temperature. In the S0.5 system, one-step YAG formation occurred by an interface-controlled mechanism, and intermediates were apparently suppressed. However, YAG formation was divided into two stages in the S1.75 and S2.5 systems. Two stages were defined by the heating duration prior to and after 20 s. The interface-controlled mechanism was dominant in the initial stage, and then the diffusion-controlled mechanism was dominant in the second stage, in which YAG formed sluggishly and substantial amounts of YAM and YAP persisted. However, both stages followed the conversion sequence of YAM to YAP and then to YAG. Accordingly, two YAG formation routes derived from reacted Y2O3 of different sizes are proposed. Finally, a pure YAG phase could be obtained by calcining the S0.5 system at 1200 °C for 60 s.
E0304 – Carburization of W- and Re-rich Ni-based alloys in impure helium at 1000 C
The surface and microstructure stability of experimental W- and Re-rich Ni-based alloys in an impure-helium environment containing only CO and CO2 as impurities (ppm level) have been investigated at 1000 °C. All the alloys carburized during 50 h of exposure, and, depending on the alloy composition, different carbides of the type M6C, M7C3 and M23C6 formed on the alloy surface, in grain interiors and at grain boundaries. Microprobe analysis and Calphad-based calculations indicated that the chromium carbides (particularly Cr23C6) were enriched by rhenium. Extended exposure (225 h) led to the disappearance of surface transient carbides and the growth of surface oxide Cr2O3 occurred.
E0314 – Effect of inclusions in Nd-doped NaY(WO4)2 single crystals
Single crystals of Nd-doped NaY(WO4)2 (Nd:NYW) were grown using the Czochralski technique. Crystal cracking and the presence of inclusions were found to be the main problems associated with the growth of crystals. Thermal expansion measurements were carried out on as-grown crystal samples that were cut perpendicular to the growth direction and had different amounts of inclusions. Differential thermal analysis was also carried out on these same samples. The amount of inclusions present in the Nd:NYW crystal was found to affect the thermal characteristics of the crystal. The role of impurity phases in the Nd:NYW lattice during growth is discussed on the basis of obtained results. The inclusions present in the crystal are found to produce excessive strain in the lattice, which ultimately results in cracking of the crystal.
E0303 – The effect of P2O5 on the structure, sintering and sealing properties of barium calcium aluminum boro-silicate (BCABS) glasses
The effect of P2O5 incorporation on the sintering, flow and crystallization characteristics of BCABS glasses of composition (mol%) 35BaO–15CaO–5Al2O3–(37 ? x)SiO2–8B2O3–xP2O5 (0 ? x ?5) is investigated. It is observed that addition of P2O5, removes cations (Ba2+ and Ca2+) from the silicate network, resulting in an increase in polymerization. This is reflected by a reduction in TEC and an increase in sealing temperature. In addition, the removal of cations for charge compensation causes a change in major crystalline phases formed, from BaSiO3 to Ba(Al2Si2O8). In addition, beyond 3 mol% P2O5, crystallization of phosphate phases is evident. Based upon the flow temperature, glasses with 0, 1 and 2 mol% P2O5 are selected for sealing. In these glasses, conversion of Cr to Cr2O3 is observed, yielding improved adhesion. However, the 2 mol% P2O5 glass showed an increased crystallization tendency, resulting in incomplete sintering. Therefore, 1 mol% P2O5 seems a good compromise for sealing with improved adhesion
E0313 – Experimental investigation of the Cu-Si phase diagram at x(Cu)>0.72
Cu–Si phase equilibria have been investigated at compositions greater than 72 at.% Cu by X-ray diffraction, optical and electronic microscopy, electron probe microanalysis and differential thermal analysis.
The general aspects of the phase equilibria already reported in literature have been substantially confirmed, but selected composition ranges and the nature of a few invariant equilibria have been modified. In particular stability ranges of the ?, ? and ? phases have been slightly modified as well as temperature and nature of the invariant equilibria related to the ? ? ? transformation.
Stability of the ?-(Cu15Si4) phase has been especially investigated concluding that it is thermodynamically stable but kinetically inhibited by nucleation difficulties which become especially effective when samples are synthesized in very high purity conditions.
Crystal structure and composition ranges of the high temperature ? and ? phases, despite difficulties by the non-quenchability of these phases, have been investigated by different methods including high temperature XRD.
E0323 – Effect of iron oxide addition on structural properties of calcium silico phosphate glass/glass-ceramics
Glasses with nominal composition 34SiO2–(45 ? x) CaO–16 P2O5–4.5 MgO–0.5 CaF2–x Fe2O3 (where x = 5, 10, 15, 20 wt.%) have been synthesized by melt quench technique. These have been investigated for structural features by using Fourier transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results have shown an increase in fraction of non?bridging oxygen in glasses with an increase in iron oxide content up to 15 wt.% and subsequently decreases with further increase in iron oxide content to 20 wt.%. These effects are originated by the incorporation of Fe2O3 into the silica network. Iron oxide behaves as a network modifier at low concentration and stabilizes the glass network at higher content. The glass-ceramics exhibit an increase in the formation of magnetite phase with an increase in iron oxide. The glass phase in the glass-ceramics matrix, controls the surface dissolution, which in turn decides the response of the material in-vitro. The glass-ceramics with 15 wt.% iron oxide has shown optimum response in simulated body fluid.
E0322 – The role of strontium and potassium on crystallization and bioactivity of Na2O–CaO–P2O5–SiO2 glasses
The effect of SrO/CaO and K2O/Na2O replacements on the crystallization process of glasses based on Na2O–CaO–P2O5–SiO2 system was investigated. The glasses were thermally treated through controlled heat treatment regimes to obtain glass ceramic materials. Combeite Na2Ca2Si3O9, sodium calcium silicate Na2Ca3Si6O16, wollastonite solid solution, and whitlockite Ca3(PO4)2 were identified as major crystalline phases in the prepared thermally treated glasses. No potassium and strontium-containing phases could be detected in the glass–ceramics; potassium seems to be accommodated in the wollastonite structure, while strontium might be incorporated in the sodium calcium silicate structure.
The surface reactivity of the prepared glass–ceramic specimens was also studied in vitro in Kokobo's simulated body fluid (SBF). EDAX, SEM, inductively coupled plasma ICP, and FTIR were used to examine the formation of apatite layer's surface and characterize the glass ceramic surface and SBF compositional changes. A decrease in the bioactivity of the glass ceramic was observed as Na2O was replaced by K2O. Strontium together with calcium ions in the apatite layer formed was detected with SrO/CaO replacement.
The role played by the glass oxide constituents in determining the crystallization and bioactivity behaviour of the prepared thermally treated glasses was discussed.
E0321 – Performance investigation of Li2O–Al2O3–4SiO2 based glass–ceramics with B2O3, Na3AlF6 and Na2O fluxes
Influence of single fluxes (10 wt.% B2O3), bi-component fluxes (4 wt.% B2O3 + 6 wt.% Na3AlF6), and complex fluxes (4 wt.% B2O3 + 4 wt.% Na3AlF6 + 2 wt.% Na2O) on the thermal kinetic parameters, microstructure, flexural strength and coefficient of thermal expansion (CTE) of Li2O–Al2O3–4SiO2 (LAS) glass–ceramics was investigated through differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that complex fluxes could efficiently decrease transition temperature (Tg) and crystallization temperature (Tp), and accelerate the formation of needle-like ?-spodumene crystals which benefit high flexural strength. The homogeneous LAS glass–ceramic (sample C3) which has a high strength of 132.4 MPa and low CTE (100–650 °C) of 2.74 × 10? 6/°C is obtained by doping of the initial LAS glass by complex fluxes of 4 wt.% B2O3, 4 wt.% Na3AlF6, and 2 wt.% Na2O, nucleating at 630 °C/120 min and then crystallized at 780 °C/120 min. It is worthy of further investigation as a bonder of diamond composite material due to its outstanding prosperities.
E0320 – Challenges in the crystal growth of Li2CuO2 and LiMnPO4
Single crystals of a potential battery material, LiMnPO4, and the spin ladder compound Li2CuO2 are grown under elevated gas pressure in a newly designed vertical floating zone facility with optical heating. Lithium vaporization and its reaction with gases in the growth chamber are principal challenges of the growth process. By applying high argon pressure of 40 bar during Travelling Solvent Floating Zone growth of LiMnPO4 the vaporization was reduced by orders of magnitude. The optical radiation, penetrating the transparent melt, affects the crystal/melt interface curvature during the growth. The growth direction was recognized to be decisive for changing the interface curvature from concave to convex and enabling efficient grain selection. By using an Ar/O2 gas mixture in crystal growth of Li2CuO2 the direct exchange between oxygen in the atmosphere and the floating zone, the oxygen content of the melt and finally the quality of Li2CuO2 crystals are controlled
E0319 – Study of glasses/glass-ceramics in the SrOeZnOeSiO2 system as high temperature sealant for SOFC applications
Glasses having composition (in wt.%) 51SrO-9ZnO-(40?x)SiO2 (SZS), where x represents the additives like B2O3, Al2O3, V2O5, and Cr2O3, were prepared by melt-quench method and transformed into glass-ceramics by controlled crystallization based on differential thermal analysis (DTA) data. Glasses and glass-ceramics were characterized using dilatometry, X-ray diffraction (XRD), microhardness, and Raman spectroscopy. XRD revealed that glass-ceramics are composed of mainly Sr2ZnSi2O7 and SrSiO3 crystalline phases along with residual glassy phase. Raman spectroscopy showed that main constitutes of the glass network are the Q1 and Q2 silicate structural units. With the addition of B2O3 and other additives silicate glass network depolymerizes and concentration of Q1 structural units increases at the expense of Q2 units. Formation of phases during crystallization depends on the presence of different silicate structural units in the glass matrix. B2O3 goes into the glass network as triangular (BO3) borate structural units and at higher concentration of B2O3, only a part of the B2O3 forms tetragonal (BO4) structural units. Investigated glasses and glass-ceramics have thermal expansion coefficient (TEC) in the range of 105–120 × 10?7/°C which matches with TEC of other cell components. B2O3 containing SZS glasses show good adhesion/bonding with YSZ and Crofer 22 APU. Elemental line scans indicate that interdiffusion of Fe, Cr and Si across interface is responsible for good bonding with Crofer 22 APU and interdiffusion of Sr, Si, Y and Zr is responsible for good bonding with YSZ.
E0318 – Parametric optimization of Ti–Ni powder mixtures produced by mechanical alloying
In this study, a set of Ti–50 at.% Ni elemental powder mixtures were processed through mechanical alloying (MA). The objectives were to induce during MA the formation of a lamellar microstructure and to apply a design of experiments, based on the Taguchi method, to optimize the MA parameters. Enthalpy measurements associated to the high temperature reaction between Ni and Ti powders were used to evaluate the effect of the MA parameters. It is known that different ball-impact energies lead to different reaction pathways. The results indicate that milling time affects significantly (74% contribution) the enthalpy of the high temperature reaction while the milling speed has a lower effect (25% contribution). Moreover, whatever the milling conditions, the powder was a mixture of both crystalline phases and an amorphous phase. Their microstructure was composed of a multilayer of alternating Ni and Ti that in some cases was constituted by nanolayers. The oxygen and nitrogen contents of the milled powders ranged between 0.29 and 0.79 wt%, and 0.15 and 0.90 wt%, respectively.
E0317 – Characterization cement pastes degraded in laboratory solutions and physiochemical parameters employed for modeling the process
Previously degradation studies carried out, over a number of different mortars by the research team, have shown that observed degradation does not xclusively depend on the solution equilibrium pH, nor the aggressive anions relative solubility. In our tests no reason was found that could allow us to explain, why same solubility anions with a lower pH are less aggressive than others. The aim of this paper is to study cement pastes behavior in aggressive environments. As
observed in previous research, this cement pastes behaviors are not easily explained only taking into account only usual parameters, pH, solubility etc. Consequently the paper is about studying if solution physicochemical characteristics are more important in certain environments than specific pH values. The paper tries to obtain a degradation model, which starting from solution physicochemical parameters allows us to interpret the different behaviors shown by different composition cements. To that end, the rates of degradation of the solid phases were computed for each considered environment
E0327 – Nanosized pure and Cr doped Al2 xScx(WO4)3 solid solutions
Nanosized solid solutions of the formula Al2?x?yScxCry(WO4)3, where x varies from 0 to 2 and y from 0.02 to 0.1 are synthesized for the first time by the co-precipitation method. X-ray powder diffraction, DTA/TG and TEM analyses demonstrate that the powders are pure solid solution compounds with orthorhombic structure, space group Pnca. Particle sizes between 10 and 70 nm are obtained after thermal treatment of the precipitates at 550 °C for 1 h for all compositions except in the case of Sc1.9Cr0.1(WO4)3. For the last one mean particle size of 64 nm was obtained after thermal treatment at 500 °C. The influence of the concentrations of Sc and Cr as well as of the temperature and duration of the thermal treatment on the particle size and size distribution are established and discussed.
E0316 – Investigation of crystallization kinetic of SrO-La2O3-Al2O3-B2O3-SiO2 glass and its suitability for SOFC sealant
Strontium-lanthanum-aluminoborosilicate (SrO-La2O3-Al2O3-B2O3-SiO2) (SLABS) glass was prepared for sealant material in planar Solid Oxide Fuel Cells (pSOFC). Differential Thermal Analysis of the glass showed the formation of two crystalline phases, first one 807 C and the second phase at 1021 C. Crystallization kinetic of the first crystalline phase was investigated by differential thermal analysis (DTA) and using the JMA-kinetic model.
The activation energy for crystallization was calculated to be 114.04 kJ/mol with frequency factor 5.9 x 103. Coefficient of Thermal Expansion (CTE) of the glass was measured to be 9.72x 10- 6/ C. Optical band gap of the glass was measured to be 3.07 eV. Conductivity measured by Impedance spectroscopy found to be 5.68x 10-7 S cm-1 at 600 C and it increased with temperature to 2.68x 10-6 S cm-1 at 800 C. Activation energy for electrical conduction was measured to be 66.12 kJ/mol. Wetting behavior of the glass on a ferritic steel substrate was investigated under hot stage microscopy. It showed initial deformation
temperature (IDT) 754 C, softening temperature (ST) 840 C, hemispherical temperature (HT) 1108 C and flow temperature (FT) 1279 C.
E0326 – Diopside -Mg orthosilicate and diopside -Ba disilicate glass-ceramics for sealing applications in SOFC: Sintering and chemical interactions studies
Diopside (CaMgSi2O6) based glasses compositions containing magnesium orthosilicate or barium aluminosilicates phases have been appraised for sealing applications in solid oxide fuel cells (SOFCs) and other solid-electrolyte devices. The sintering behavior and crystalline phase evolution of glass powders has been investigated under isothermal and non-isothermal conditions in the SOFC operating temperature range (800–900 °C). All the glass compositions exhibited two-stage shrinkage behavior resulting in well sintered and mechanically strong glass–ceramics with Augite as the primary crystalline phase. The appropriate coefficient of thermal expansion (CTE), long term thermal stability (300 h at 900 °C), high electrical resistivity, good adhesion and minimal reactivity with SOFC components makes the investigated glass–ceramics potential candidates for further experimentation as SOFC sealants.
E0315 – Physical and thermal behaviour of Sr–La–Al–B–Si based SOFC glass sealants as function of SrO content and B2O3/SiO2 ratio in the matrix
A series of SOFC glass sealants with composition SrO (x), La2O3 (15), Al2O3 (15), B2O3 (40 ? x), and SiO2 (30) [x = 10, 15, 20, 25 and 30] (wt.%) [SLABS] are investigated for their structure property correlations at different compositions. Quantitative Fourier transform infrared spectroscopy shows structural rigidity with increasing SrO content, as demonstrate by an increase in the Si–O–Si/O–Si–O bending and B–O–B stretching frequencies. The role of SrO as a modifier dominates the control of the structure and behaviour of glasses compared with the effect of network formers, i.e., the B2O3/SiO2 ratio. Consequent to the structural changes, increasing substitution of B2O3 by SrO the glasses causes increases in the density, glass transition temperature and dilatometric softening point. On the other hand, the crystallization temperatures show a decreasing trend and the coefficient of thermal expansion increases with increase in substitution.
E0325 – The role of Nb in the formation of sulphonic species in SBA-15 and MCF functionalised with MPTMS
Mesoporous silica and niobiosilicate materials of SBA-15 and MCF types were prepared in the presence of MPTMS, i.e. (3-mercaptopropyl)trimethoxysilane and hydrogen peroxide. The samples obtained were characterised by different techniques (N2 adsorption/desorption, XRD, elemental and thermal analyses) and applied as catalysts in glycerol esterification with acetic acid. The role of niobium species on the formation of sulphonic species and stability of organosilane modifier was explored. The most important finding is that the addition of niobium to the synthesis gel improves the efficiency of –SH oxidation by hydrogen peroxide towards sulphonic species. This behaviour is not dependent on the type of structure of mesoporous materials (SBA-15 or MCF). However, the kind of mesoporous solid influences the efficiency of Nb incorporation and on the esterification process. MCF matrix improves the catalytic performance of the MPTMS modified catalyst.
E0324 – On the synthesis conditions for tailoring lithium composition in ramsdellite phases: Application for Li-ion batteries
TiO2 with the ramsdelitte-type (R) structure has a potential use as negative electrode for Li-ion battery due to its high theoretical capacity (335 mAh g?1), a weak irreversible loss during the first cycle and a low polarization. However due to its metastability, TiO2 (R) has been rarely reported. In the present work we report on the carbothermal synthesis of some LixTiO2 delithiated R phases (0 < x < 0.57), from TiO2 to Li2Ti3O7, with ramsdellite-type structure. The variation of the synthesis parameters such as wt% of carbonaceous additive and reductive gas flow has conducted to the formation of poor lithiated LixTiO2 phases and Li2TiO3 as additional phase. Their ratio was found to be strongly dependent on the amount of carbonaceous precursor. These new LixTiO2(R)/Li2TiO3 composites (with (0 ? x ? 0.57)) were characterized by chemical analysis, X-ray diffraction and thermogravimetric analysis and finally by electrochemical tests. High capacities as well as good cycleability have been reached.
E0334 – Laser cladding of bioactive glass coatings
Laser cladding by powder injection has been used to produce bioactive glass coatings on titanium alloy (Ti6Al4V) substrates. Bioactive glass compositions alternative to 45S5 Bioglass® were demonstrated to exhibit a gradual wetting angle–temperature evolution and therefore a more homogeneous deposition of the coating over the substrate was achieved. Among the different compositions studied, the S520 bioactive glass showed smoother wetting angle–temperature behavior and was successfully used as precursor material to produce bioactive coatings. Coatings processed using a Nd:YAG laser presented calcium silicate crystallization at the surface, with a uniform composition along the coating cross-section, and no significant dilution of the titanium alloy was observed. These coatings maintain similar bioactivity to that of the precursor material as demonstrated by immersion in simulated body fluid.
G0011 – High-temperature thermogravimetric analysis. Influence of gas pressure on kinetics of reactions in the solid state
A magnetic balance apparatus has been set up to follow reactions in the solid state under
controlled conditions of pressure and temperature (25-1000°) Magnetic properties are
characteristic of solid structures, and thermomagnetic analysis (T. M. A.) can give the variations
of the sample susceptibility during the course of a reaction (susceptibilities of the new
phases and of initial compounds not yet transformed). By continuous measurement of this
susceptibility with the Faraday method, the conversion degree of the synthesis can be
T. M. A. has been used to study the influence of a gas on a solid-solid reaction in which
no gas can be evolved or consumed. An example is given for iron tungstate synthesis:
Fe203(s) + WO3(s) --> Fe2WO6(s). At 800° the reaction kinetics depends on the nature and
the pressure of the gas.
E0333 – Investigations of the non-isothermal crystallization of CaF2 nanoparticles in Sm-doped oxy-fluoride glasses
Oxyfluoride glass samples in the system SiO2–Al2O3–CaF2–SmF3 were produced by using the melt-quenched technique and the kinetics of non-isothermal crystallization of CaF2 nano-crystals has been investigated. Differential thermal analysis (DTA) has shown an exothermic peak at about 700 °C which was assigned to the CaF2 nano-crystals precipitation within the glass matrix as was identified by X-ray diffraction (XRD) analysis of the annealed glass samples. It was shown the Ozawa model is most suitable for describing the behaviour of non-isothermal crystallization of CaF2 nano-crystals within the glass matrix. The mean value of the Avrami exponent was found 1.16 which indicates the diffusion-controlled growth process of nano-particles in the glass system with zero nucleation rate as the single operative mechanism; the activation energy of the crystallization is Ed = 379 ± 25 kJ/mol (3.93 ± 0.26 eV). The activation energy of the nano-crystals growth was computed within the same model and agrees very well with the activation energy of the crystallization.
E0343 – Investigation of hot cracking resistance of 2205 duplex steel
Austenitic duplex steel of the brand 2205 according to Avesta Sheffield is used for welded constructions (pipelines, tanks) in the petrol industry, chemical industry and food industry. It is important to know the range of high-temperature brittleness in designing welding technology for constructions made of this steel type. There is no data in literature concerning this issue. High-temperature brittleness tests using the simulator of heat flow device Gleeble 3800 were performed. The tests results allowed the evaluation of the characteristic temperatures in the brittleness temperature range during the joining of duplex steels, specifically the nil-strength temperature (NST) and nil-ductility temperatures (NDT) during heating, the strength and ductility recovery temperatures (DRT) during cooling, the Rfparameter (Rf = (Tliquidus – NDT)/NDT) describing the duplex steel inclination for hot cracking, and the brittleness temperature range (BTR). It has been stated that, for the examined steel, this range is wide and amounts to ca. 90 °C. The joining of duplex steels with the help of welding techniques creates a significant risk of hot cracks. After analysis of the DTA curves a liquidus temperature of TL = 1465 °C and a solidus temperature of TS = 1454 °C were observed. For NST a mean value was assumed, in which the cracks appeared for six samples; the temperature was 1381 °C. As the value of the NDT temperature 1367 °C was applied while for DRT the assumed temperature was 1375 °C. The microstructure of the fractures was observed using a Hitachi S-3400N scanning electron microscope (SEM). The analyses of the chemical composition were performed using an energy-dispersive X-ray spectrometer (EDS), Noran System Six of Thermo Fisher Scientific. Essential differences of fracture morphology type over the brittle temperature range were observed and described.
E0332 – Polymorphism of new rubidium magnesium monophosphate
Novel phase RbMgPO4, synthesized by solid state reaction, sustains phase transitions at 169 and 184 °C. The medium (?)- and high- (?) temperature forms (orthorhombic, respectively Pna21 and Pnma, Z=4) are typical stuffed tridymites but the ambient form (?) exhibits an unusual three-fold Pna21 superstructure that results from the change of coordination of one third of the Mg atoms. Cell parameters are as follows: for ?: a=26.535(1) Å, b=9.2926(3) Å, c=5.3368(2) Å; for ?: a=8.7938(3) Å, b=9.3698(3) Å, c=5.3956(1) Å; for ?: a=8.7907(3) Å, b=5.4059(1) Å, c=9.3949(3) Å.
E0342 – Experimental study of the Fe–Ni–Ti system
In this investigation phase relations in the Fe–Ni–Ti system were studied and two isothermal sections at 800 °C and 1000 °C as well as a revised liquidus projection were established. Microstructural characterisation of the as-cast alloys and of samples equilibrated at 800 and 1000 °C was performed by scanning electron microscopy (SEM), chemical compositions of the phases were analysed by electron probe microanalysis (EPMA), and liquidus temperatures were examined by differential thermal analysis (DTA). The experimental results clarify some uncertainties concerning the melting behaviour and the solid-state phase equilibria between the phases (Ni,Fe)Ti2, (Fe,Ni)Ti and ?-Ti. The present data also confirm that the solid solubility of Ti in ?-(Fe,Ni) varies in dependence on the Fe:Ni ratio and decreases with decreasing temperature. The liquidus projection as well as the reaction scheme in the Ti-lean part are modified because two ternaries eutectic E1: L ? ?-(Fe,Ni) + Fe2Ti + Ni3Ti and E2: L ? Fe2Ti + Ni3Ti + (Fe,Ni)Ti are found at 1108 and 1099 °C, respectively.
E0331 – Processing and Properties of Eu3+-Doped Transparent YAG (Y3Al5O12) Nanoglass–Ceramics
An Eu3+-doped novel mother glass in the K2O–SiO2–Y2O3–Al2O3 (KSYA) system was prepared by the melt-quench technique. The transparent Y3Al5O12 (YAG) glass–ceramics were derived from this glass by a controlled crystallization process. The formation of YAG crystal phase, size and morphology with the progression of heat treatment was examined by X-ray diffraction (XRD), transmission electron microscopy, field-emission scanning electron microscopy, and Fourier transformed infrared reflectance spectroscopy. The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range of 35–45 nm. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0?7Fj (j=0, 1, 2, 3, and 4) and its excitation spectra show a charge transfer band around 280 nm. From these emissions, the site symmetry in the vicinity of Eu3+ ions has been found to be Cs or lower than Cs in the nanoglass–ceramics. Absorption and fluorescence spectra reveal that the Eu3+ ions are entering into the YAG nanocrystals of the glass–ceramics. The present study indicates that the incorporation of Eu3+ ions into the YAG crystal lattice enhance the fluorescence performance of the nanoglass–ceramics. We believe that this work would generate new avenues in the exploration of YAG nanoglass–ceramics in particular and other glass–ceramics of very high-temperature melting crystals in general.
E0341 – Cu-based metallic glass particle additions to significantly improve overall compressive properties of an Al alloy
We report the development of a novel light-weight Al (520) alloy-based composite reinforced with particles of a Cu-based (Cu54Zr36Ti10) metallic glass by mechanical milling followed by induction heated sintering. The consolidation of the composite is performed at a temperature in the super-cooled liquid region of the metallic glass just above its glass-transition temperature (Tg). Metallic glasses are a promising alternative reinforcement material for metal-matrix composites capable of producing significant strengthening along with a «friendly» sintering behavior. The mechanical milling procedures were properly established to allow reduction of the size of the metallic glass particles and their uniform distribution in the matrix. Microstructural observation of the composite did not reveal any porosity. The interface between the glassy particles and the matrix remained free of such defects. The fully dense consolidated composite showed a drastic gain in specific yield strength under compression relative to the matrix alloy and appreciable plasticity at fracture.
E0330 – Influence of the morphologic evolution of the eutectic carbides at high temperature on the thermal expansion behavior of refractory cast alloys
Two alloys particularly rich in carbides, a nickel-based one reinforced by chromium carbides and a cobalt-based one strengthened by tantalum carbides were characterized by metallography and their hardness and thermal expansion behavior tested, after alloys had undergone a more or less long aging treatment at high temperature. Aging induces a progressive coarsening and/or fragmentation of these interdendritic carbides, with as first consequence a decrease in hardness. Also due to these morphology changes, aging the alloys on long time leads to a loss of effect of the carbides on the thermal expansion behavior of the alloys. The total thermal expansion, initially lowered by the rigid carbides network, is then free again. Indeed, the high temperature phenomenon of plastic or viscous-plastic deformation in compression of the matrix by the initial continuous carbides network has almost disappeared.
E0340 – Elaboration of porous mullite-based materials via SHS reaction
In order to produce cheaper mullite from kaolinitic clays we worked on the opportunity to use self-propagating high-temperature synthesis (SHS) reaction to obtain this phase. Two ways were explored during the combustion of metals mixed with the clay. The first one concerns the nature of the combustion gas (air or pure oxygen) which was tested on mixtures of clay and metal powders. The second one showed the influence of magnesium addition in clay/Al mixture. Results conclude that to obtain porous mullite at low-cost by SHS process the best conditions are the addition of magnesium powder and combustion in oxygen gas. Because a SHS reaction is always quicker, we compared this process with the traditional reactive sintering in order to explain the structure and the microstructure of the SHS products.
E0329 – The ternary Cr–Al–Nb phase diagram: Experimental investigations of isothermal sections at 1150, 1300 and 1450 ?C
Isothermal sections of the ternary Cr–Al–Nb phase diagram were experimentally investigated for temperatures of 1150, 1300, and 1450 °C by electron-probe microanalysis (EPMA), X-ray diffraction (XRD), differential thermal analysis (DTA) and light-optical (LOM) as well as scanning electron microscopy (SEM). Cr–Al–Nb alloys were prepared by levitation melting and annealed at temperatures between 1150 and 1450 °C for up to 1500 h. The most striking feature of the ternary Cr–Al–Nb phase diagram is the extended phase field of the cubic C15 and the hexagonal C14 Laves phase Nb(Cr,Al)2. With increasing Al content, the Laves phase polytype changes from C15 to C14. Both phase fields are separated by a small two-phase field, which shifts to lower Al contents with increasing temperature. The lattice parameters of both Laves phase polytypes and of all other phases occurring in this system were studied in dependence on composition and the solubilities of ternary elements in the binary phases were established.
E0339 – Nonmagnetic Fe-site doping of BiFeO3 multiferroic ceramics
In this paper, we show that a pure single phase by doping Fe-site of BiFeO3 (BFO) using tetravalent Zr4+ ions can be achieved by introducing cation (Bi3+) vacancies. The structural analysis reveals that the ferroelectric nature of BFO should be weakly affected by 10% of Zr4+ doping as the c/a ratio and the Curie temperature TC remain roughly unchanged compared to that of pure BFO. In contrast, the magnetic properties are affected as a weak ferromagnetism and a change of Néel temperature TN are observed. Beyond the double-exchange interactions arising from the creation of Fe2+, we propose another simple model inducing a local ferromagnetic coupling rather than an antiferromagnetic which considers the replacement of the magnetically active Fe3+, time to time, by a nonactive Zr4+.
E0328 – Experimental determination and thermodynamic modeling of the Ni–Re binary system
The phase diagram of the Ni–Re binary system has been partially reinvestigated by chemical, structural and thermal characterization of the arc melted alloys. The experimental results obtained during the present investigation were combined with the literature data and a new phase diagram of the Ni–Re binary system is proposed. In comparison with the Ni–Re phase diagram proposed by Nash et al. in 1985 , significant differences in the homogeneity domains, freezing ranges and peritectic reaction temperature were evidenced. On the other hand, thermodynamic modeling of the studied system by using the new experimental information has also been carried out with the help of the CALPHAD method. The calculated Ni–Re phase diagram showed a good agreement with the selected experimental information.
E0338 – Silica doped bismuth lead oxyfluoride glass ionic conductors
Doping of bismuth lead oxyfluorides by silica (30 at.%) makes it possible to stabilize a large vitreous domain. The presented study relates to the stability of the vitreous phase and the variation of conductivity versus temperature, as well as composition. DTA heating analyses evidenced the temperature of vitreous transition followed by the material recrystallization. The crystallized phase was identified by high temperature Guinier Lenné pattern. The best conductivity, about 3 × 10? 3 Scm? 1 at 220 °C, was obtained for the fluorine richest material.