Calcined powders were prepared for sintering of cubic Cs_0.9Al_0.9Si_2.1O₆ by calcining a mixture of Al₂O₃/SiO₂ fine powder and CsNO₃ powder at temperatures of 798 to 1123K for 20h in air. The amorphous phase produced in the case of a lower calcination temperature, while the crystallinity of the calcined powder increased with increasing calcination temperature. Densification of the Cs_0.9Al_0.9Si_2.1O₆ green body was significantly enhanced using the amorphous calcined powder. The relative density of the Cs_0.9Al_0.9Si_2.1O₆ sintered body reached 94.5% when the green body of the amorphous calcined powder, including a slight amount of CsNO₃, was sintered at 1673K for 20h in air. The dense cubic Cs_0.9Al_0.9Si_2.1O₆ sintered body showed linear thermal expansion without hysteresis, resulting in a thermal expansion rate of ca. 0.13% at 1273K.

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The pore structure and permeation properties of kaolin-silica (quartz)-alumina (corundum) ceramics have been investigated using kaolin, SiO₂ and Al₂O₃ powders as staring materials. The Al₂O₃ powders used are of different particle sizes, 0.8 and 4.0μm. Mullite phase appears at approximately 1373K and mullite phase content in the sintered samples increases with the increase in sintering temperature from 1373 to 1573K for 1h. Open porosity decreases from 48.4 and 46.8% to 32.3% for the 0.8- and 4.0-μm Al₂O₃ powders, respectively. The maximum average pore sizes have been noted to be 0.51- and 0.63-μm for the 0.8- and 4.0-μm Al₂O₃ powders as-sintered at 1473K, respectively. The maximum penetrating porosity is 24.1% for the 0.8-μm Al₂O₃ powder as-sintered at 1473K; it decreases with the increase in temperature for the 4.0-μm Al₂O₃ powder. The tortuosity of the 0.8-μm Al₂O₃ powder does not change significantly, but that of the 4.0-μm Al₂O₃ powder decreases from 0.85 to 0.29 with the increase in sintering temperature. Seemingly, the mullite-based filtration material has been shown to be more efficient and durable than conventional polymeric and diatomite materials.

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High temperature thermoelectric properties of Ca_1-xDy_xMnO_2.98 (x=0, 0.05, 0.10, 0.15, 0.20) have been measured in the temperature range from 300 to 1273K. Ca_1-xDy_xMnO_2.98 (x=0.10, 0.15, 0.20) exhibited the metal-insulator transition in the relation between electrical resistivity and temperature, and the transition temperature increased with increasing x. Electrical resistivity in the metallic region decreased with increasing x content, reflecting the increase of Mn³⁺ ions, and the absolute value of Seebeck coefficient (α) also decreased. Thermal conductivity (λ) did not considerably change with increasing x content. Among substituted CaMnO₃, the highest figure of merit of Z=1.05×10^-4K^-1 was obtained for x=0.05 and 0.10 at 773K, while a Z=1.63×10^-4K^-1 was obtained for x=0.20 at 1273K.

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Fabrication of dense and highly textured ceramics is significantly important for the improvement of their anisotropic properties by the templated grain growth (TGG) method. Monte Carlo simulation based on the Potts model was carried out through computation for the design of TGG processing, in which anisometric template particles are mixed with fine matrix particles and organic binder and aligned by tape casting before heat treatment. Thus, four initial parameters affecting the microstructure after sintering with isotropic grain growth were investigated; 1) mixing ratio of template/matrix particles, 2) size and 3) aspect ratio of the template particles, and 4) initial porosity (caused by the removal of binder). The fraction of oriented grains in the simulated microstructure was found to increase with increasing template/matrix mixing ratio and aspect ratio of template, and with decreasing template size and initial porosity. The residual porosity was shown to decrease with decreasing template/matrix mixing ratio and template size, and with decreasing initial porosity. The study suggests that computational design would give a guiding principle in terms of the initial preparation conditions for the ceramics having both a large fraction of oriented grains and low residual porosity.

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Transparent monolithics of poly(tetramethylene oxide) (PTMO)-modified CaO-TiO₂ hybrids were obtained by hydrolysis and polycondensation of triethoxysilane end-capped poly(tetramethylene oxide) (Si-PTMO), tetraisopropyltitanate (TiPT) and calcium nitrate. Under the constant ratio of (Si-PTMO)/(TiPT)=2/3 in mass, the molar ratio of (Ca(NO₃)₂)/(TiPT) was varied from 0 to 0.15. The hybrid samples were subjected to the evaluation of the apatite-forming ability in a simulated body fluid (SBF) and to the mechanical property measurements in air by three-point bending. The apatite-forming ability in SBF remarkably increased with increasing CaO content. The hybrid samples with (Ca(NO₃)₂)/(TiPT)=0.10 and 0.15 in mol formed an apatite on their surfaces within only one day. Although the Young's modulus and bending strength decreased with increasing CaO content, all the values were within the range of those of human cancellous bone. The failure strains were found to be in the range of about 13 to 25%. Thus, the hybrids exhibiting both high apatite-forming ability and high capability for deformation were successfully synthesized. These hybrids may be useful as new kind of bioactive bone-repairing materials.

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This paper reports on the reaction, microstructures and mechanical properties of model ceramic ware produced using nonplastic raw materials of feldspar, alumina and silica. The feldspar of median size 2.60μm and γ-alumina of 34nm or α-alumina of 0.2 or 0.6μm, were mixed with tetraethyl orthosilicate at the composition of feldspar/alumina/silica=38.3/16.6/45.1 (mass%). After hydrolysis of tetraethyl orthosilicate with HCl solution, the dried powders were compacted and sintered at 1200-1300°C for 1-10h. Fine γ-alumina particles reacted with feldspar and silica to produce mullite whiskers of 1μm length, cristobalite and a liquid phase rich in silica. Cristobalite formed by the crystallization of silica component in the liquid phase during the cooling process. In the ceramic ware using submicrometer-sized α-alumina particles of median sizes 0.2 and 0.6μm, little α-alumina particles dissolved in the liquid phase, indicating the formation of metastable phases of α-alumina-liquid. Crystallization of silica component from the liquid during the cooling process was disturbed by the presence of α-alumina particles. These samples contained spherical air bubbles of 10-80μm in diameter in the glassy matrix. In the sample with 34nm-γ-alumina (30mass%) and 0.6μm-α-alumina (70mass%), both stable and metastable phases of mullite-α-alumina-liquid were produced. The ceramic ware of metastable phases (α-alumina-glassy matrix) including air bubbles showed a lower Young's modulus and a larger strain at fracture than the rigid ceramic ware of stable phases (mullite-cristobalite-glassy matrix) with interlocking mullite whiskers. However, the flexural strength was comparable between samples of the stable and metastable phases. Vickers hardness was higher for the sample with mullite whiskers than for the sample with α-alumina particles because of an increased resistance by the interlocking of mullite whiskers to the applied Vickers load.

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ZrO₂-pillared fluorine micas were prepared from synthetic highly layer-charged expandable fluorine mica and an aged zirconyl chloride solution under different conditions, with or without using poly(vinyl alcohol) (PVA) as a template agent. The effect of preparation conditions on the formation and properties of the pillared micas have been studied. The basal spacings and the specific surface areas of the ZrO₂-pillared fluorine micas obtained by the template method were larger than those obtained by the direct intercalation method without PVA. The specific surface area of the pillared micas synthesized by the template method using PVA depended on preparation conditions, such as washing conditions and intercalation temperatures. The washing process of the initial complexes was a key step in controlling the specific surface area of pillared micas at lower heat treatment temperatures. The pillared mica obtained by the template method at the optimal intercalation temperature of 25°C gave a maximum BET specific surface area of 240m²·g^-1 and a basal spacing of 2.1nm following a heat treatment at 500°C. Machinable sintered bodies of ZrO₂-pillared fluorine micas retaining micropores were obtained by firing powder compacts of pillared mica precursors at 600-700°C without binders.

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Sb-S binary glass samples with a batch composition of Sb_33.3S_66.7 could be obtained by a melt-quenching method using a vacuum-sealed silica ampoule. The glass transition temperature of Sb_33.3S_66.7 glass was 163°C. Two series of Ge-Sb-S ternary glasses, namely GeS₂-SbS_1.5 and GeS₂-SbS₂ were also prepared. The Ge-Sb-S glasses at 20-40mol% SbS₂ possess relatively-high thermal stability with the difference between glass transition and onset crystallization temperatures over 200°C. The compositional dependence of molar volume calculated from measured density was evaluated for Ge-Sb-S glass samples. Raman spectroscopy revealed that Ge-Sb-S glasses consist mainly of GeS₄ tetrahedra and SbS₃ pyramids and the SbS₂ glass is composed of SbS₃ pyramids. Additionally Ge-Sb-S glasses at 20-50mol% SbS₂ in a series of GeS₂-SbS₂ contain S-S bonds.

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The internal friction of K₂O-Na₂O-B₂O₃-Al₂O₃-SiO₂ and Na₂O-SrO-B₂O₃-Al₂O₃-SiO₂ glasses was measured by a free damping method, and the minimum alkali content for exhibiting the mixed alkali or mixed cation effect was determined. In the former glasses, two independent peaks at lower temperatures caused by the movement of K and Na ions were observed for glasses containing less than 4mol% alkali content. In the latter system, similar peaks were recognized for glasses containing less than 7mol% total cation contents. These results confirmed that no mixed alkali effect appears for glasses containing a small content of alkalis and that the effect of mixed cation effect is less pronounced than the mixed alkali effect.

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Frictional properties of Fe₅Si₃ dispersed Si₃N₄ were investigated using polyolester and normal oil with additives as lubricants; the following results were obtained: 1) when polyolester was used, Fe₅Si₃ dispersed Si₃N₄ showed obviously lower friction coefficient than cast iron while friction coefficient of both materials were almost the same under normal oil testing conditions; 2) chemical analysis proved that a relatively high amount of calcium-sulphonate as detergent-dispersant existed on wear track of Fe₅Si₃ dispersed Si₃N₄, while oiliness-agent was not detected. Those results suggested that adhering of calcium-sulphonate to the surface of Fe₅Si₃ dispersed Si₃N₄ reduced oiliness and raised the friction coefficient.

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Zirconia balloons were molded from a formamide/benzene/formamide (F/B/F) emulsion. Balloons of several tens μm in size could be fabricated by dispersing 1.5mol·l^-1Zr(OC₄H₉ ⁿ)₄ benzene solution into formamide at 8000rpm. The size of the obtained zirconia balloon precursors ranged from 1μm to 50μm and its mean diameter was 20μm. Upon heat-treating at 1300°C zirconia balloon precursors transformed to zirconia balloons. The size distribution of heat-treated balloons was in the range between 1 and 45μm with a mean value of 10μm in diameter. The percentage of unflawed balloons was 91% after heat-treatment. The crust microstructure of the zirconia balloon changed with crust thickness. For thicknesses >1.5μm, the crust was constructed of about 0.3μm grains in diameter and had dense inner and outer surface layers. Pores were observed between these surface layers. For thicknesses between 0.3 and 0.9μm, the balloon crust was constructed by one to three 0.3μm grains in diameter. Decreasing crust thickness to less than 0.3μm, a single plate like grain was observed.

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Two kinds of alumina powders, having different particle size and impurity level, were centrifuged and effects of powder characteristics on the compaction process studied. The powder having a larger particles size and higher impurity level could be dispersed to a higher solid loading (maximum 60% solid loading) with a smaller amount of dispersant addition than the powder having a smaller particle size and lower impurity (maximum 44% solid loading). After centrifugation, a higher packing density was attained for a slip with higher solid loading up to 56%, beyond which the packing density dropped slightly. Mass segregation was negligible in the compact obtained from slips of high solid loadings, namely the 56vol.% suspension for the coarse powder and the 44vol.% suspension for the fine powder, respectively. However, a packing density gradient was observed in the green compacts, where the density decreased linearly from bottom to top of the cakes, but the gradient was smaller for the fine powder. The fine powder showed superior sintering and mechanical behaviors as compared to that of the coarse powder.

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We studied the characteristics of Ni paste used for internal electrodes of multilayer ceramic chip capacitors (MLCCs). The effect of the addition of BaTiO₃ resinate into Ni paste on the green density and sintering characteristics of Ni electrode films were evaluated. The green density of electrode films exhibited the maximum value, 5.7g/cm³, at 1mass% addition of BaTiO₃ resinate and further addition caused a decrease. From the measurement of sintering shrinkage of the electrode film, it was observed that shrinkage of electrode films increase with an increase in the amount of BaTiO₃ resinate. Similar results were measured on the surface of sintered electrode films by SEM observation.

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Although there is a strong need to understand the chemical corrosion resistance of aluminum nitride (AlN) ceramics for their applications as structural parts in semiconductor processes, there is insufficient information on chemical corrosion. We examined two kinds of commercial AlN ceramics with high thermal conductivity (170 and 200Wm^-1K^-1) in both acid and basic aqueous solutions, such as KOH, NaOH, HNO₃ and H₂SO₄, using different concentrations. Weight changes, phases present, and microstructures on the surfaces before and after testing were evaluated. Basic aqueous solutions corroded AlN ceramics in exactly the same way as acid aqueous solutions. Although secondary phases, such as yttrium aluminate, were mainly dissolved in acid aqueous solutions, AlN itself was corroded in basic aqueous solutions. Furthermore, we observed that the weight loss of AlN ceramics with higher thermal conductivity exceeded that of lower thermal conductivity. It seems that oxygen dissolved in AlN grain influences on corrosion of AlN ceramics.

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Trace amounts of chromium (-6.4mass ppm of Cr(VI) and 58.4mass ppm of total Cr) in ordinary Portland cement was monitored in hydration process using XAFS (X-ray absorption fine structure). Our XAFS data indicated the hexavalent chromium (Cr(VI)) in cement was decreased as the hydration of cement proceeds. Little divalent iron contained in cement was assumed to act as a reducing agent, and a technique to prevent the elution of chromium was proposed in this connection.

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The application of a β-Al₂O₃/LaAlO₃ eutectic-based composition for high temperature combustion catalysis has been investigated. Substitution of Al sites by Mn in the β-Al₂O₃/LaAlO₃ eutectic structure occupied 5at% of the total Al sites with no trace of impurity phases. The substitution of Al by Mn in the β-Al₂O₃ phase was more predominant than in the LaAlO₃ phase. The perovskite phase was easily removed by chemical etching and single crystal like porous β-Al₂O₃ was successfully prepared.

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Carbon spheres containing ZnO were prepared through carbonization of a resin ion-exchanged by Zn²⁺ ions. Candida albicans was used as a test fungus, and the antifungal activity of the obtained carbon samples was studied by a colony count method. The amount of ZnO in carbon spheres decreased with increasing carbonization temperature, whereas the specific surface areas increased with decreasing temperature. Antifungal activity was recognized in all carbon samples and increased with increasing the powder concentration in medium. At powder concentration above 25mg·cm^-3, the antifungal activity of carbon samples was found to decrease with increasing carbonization temperature. Below 25mg·cm^-3, however, the increase in carbonization temperature did not affect the decrease in antifungal activity; that is, there was no difference among the antifungal activity of different carbon sample.

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