SiAlON composites composed of Y-α′-SiAlON and β′-SiAlON were fabricated by hot-pressing mixtures of Y-α′-SiAlON and α-Si₃N₄. The amount of Y-α′-SiAlON decreased during sintering. The lattice constant (solubility) of Y-α′-SiAlON after sintering depended on the initial amount of Y-α′-SiAlON and was lower than that before sintering. On the other hand, the lattice constant (solubility) of β′-SiAlON remained constant. It is thought that Y-α′-SiAlON with lower solubility was formed by the reaction between the Y-α′-SiAlON and α-Si₃N₄.

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The thermal conductivity of an AlN-and an alumina-particulate-filled epoxy resin was investigated as a function of their volume content ratios. AlN composite exhibited thermal conductivity of 7.15W/m·K at 68.5vol% filler content but that of alumina composite was lower than 2.68W/m·K even if the filler content was as much as 63.8vol%. The thermal conductivity of the composites is strongly dependnt on that of the filler. In the AlN filler properties, the particle size of the filler used affected the thermal conductivity of composites, and composites with higher thermal conductivity could be obtained by using filler with large particle size. The thermal conductivity of composites is governed by the number of resin layers on the surface of an AlN particle. The composite thermal conductivities decreased with increasing the oxygen content of the filler. The thermal conductivity of an AlN particle depends on the oxygen content of the particle itself and the decrease of the composite thermal conductivity with the increase of the oxygen content of the filler is due to the increase of the aluminum oxide layer thickness produced on the surface of particles. In the thermal conductivity model, the measured thermal conductivity of AlN-ground-powder-filled composites disagreed with the ones calculated using Bruggeman's expression. However the measured values of aluminaspherical-powder-filled composites agreed with the calculated ones. It is considered that the results depended on the sphericity of the used powder.

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Ab-initio molecular orbital calculations have been performed on the cluster modeling the medium-range structure of TeO₂ glass at the Hartree-Fock level. The calculations have reasonably reproduced a neutron radial distribution function and Raman spectrum observed for TeO₂ glass. The calculated results have also demonstrated that the short- and medium-range structures of TeO₂ glass cannot be interpreted in terms of the structural unit of either α-TeO₂ or β-TeO₂ crystal, suggesting that TeO₂ glass has an inherent structure that can not be found in the corresponding crystals.

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A new method for preparing titanium dioxide fibers using sodium alginate has been developed, Titanium dioxide fibers were obtained by heating alginic acid fibers containing titanium dioxide particles (precursors) in air, which were produced from titanium dioxide sol and sodium alginate as starting materials. X-ray microanalysis (EPMA) of the cross section of the precursors showed that titanium dioxide particles were homogeneously distributed from the surface to the center of the precursors. When the precursors were heated (holding time: 1h, temperature: 900°C), phase transition from anatase to rutile was observed. In addition, the pores between particles became very small as heating temperature was increased above at 900°C, which indicates that the particles become densely distributed.

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The translucent and colorless calcium and strontium hydroxyapatite (Ca, Sr)-HAp ceramics with compositions of (Ca_10-10xSr_10x)(PO₄)₆(OH)₂, where x=0-0.8, were successfully prepared by hot isostatic pressing (HIP). The physical properties of obtained samples with x=0-0.8 were investigated. The lattice constants and hexagonality, c/a, of (Ca, Sr)-HAp samples gradually increased with increasing Sr content and were in good agreement with the data listed in JCPDS cards. The relative density for all samples HIP-treated was in the range of 96.4 to 99.7%. The values of Vickers hardness, H_V, for all samples were almost constant in the range 5.5-5.9GPa regardless of the change in x, exhibiting the good approximation to the H_V values of natural teeth. From the FE-SEM observations, the obtained samples had almost pore free microstructures consisting of about 1.6-1.9μm HAp grains. Judging from FT-IR measurements, there is the possibility that the (Ca, Sr)-HAp ceramics HIP-treated are applicable to special uses such as optical matched filters.

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Variations of piezoelectric properties and compressive strengths of PZT ceramics with the strength and the direction of poling were investigated. With increasing the applied electric field, the coupling constant, k₃₃, increased constantly and the volume fraction of grain boundary fracture also increased. This suggests that the rearrangement and the anisotropic stretching of domains during the poling process led to weakening the grain boundaries. Anisotropical compressive and tensile internal stresses of 137MPa and 76MPa were induced perpendicular and parallel to the poling direction, respectively. The isotropic compressive strength of 52MPa was found in the unpoled PZT specimens. The change of internal stress of poled PZT by electrical field was coincident with that of compressive strength. The compressive strength of the specimen revealed to be higher in parallel to the poling direction, but the internal stress in parallel to the poling direction was smaller than the internal stress in perpendicular.

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Alpha-Si₃N₄ containing 8mass% Y₂O₃ was hot-pressed at 1750°C (SN1) and then heat-treated at 1900°C for 2h (SN2). The microstructure of the sintered materials was observed using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Both SN1 and SN2 had the microstructure composed of Si₃N₄ grains and grain boundary phases located at two-grain junctions and multi-grain junctions. Heat treatment promoted grain growth of β-Si₃N₄; SN2 had a larger grain size than SN1. The number of multigrain junctions decreased by heat treatment, whereas the size of multi-grain junctions increased. The average width of the two-grain junction film increased by heat treatment, suggesting that the composition of films changed. Crystalline phase was observed at the multi-grain junctions of SN1, whereas those of SN2 were amorphous. The bend strength of SN2 at high-temperatures was lower than that of SN1 because of amorphous phase at multi-grain junctions and the composition change of thin films.

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Molybdenum disilicide (MoSi₂) is considered as a candidate material for high temperature structural applications, particularly in oxidizing environments. In the present study, SiC-whisker reinforcement has been applied to improve the mechanical properties such as fracture strength and fracture resistance at room temperature as well as creep resistance at elevated temperature. Almost dense SiC-whisker-reinforced MoSi₂ composites containing up to 20vol% whisker were fabricated by hot-pressing at 1750°C. Due to the well-dispersed composite structure with fine grained matrix, the composites showed much higher bending strength than unreinforced materials; the average 4-point bending strength increased from 350MPa for MoSi₂ to 870MPa for MoSi₂-20%SiC_w. The fracture resistance also considerably improved by the SiC-whisker reinforcement. The composites exhibited increasing R-curve behavior and the plateau values were about 23-34% higher compared to that of the unreinforced materials. Crack bridging was found to be mainly responsible for the toughening contribution. Creep resistance was remarkably increased by the suppression effect of SiC-whisker on the grain boundary sliding, which was confirmed to be an important deformation mechanism in MoSi₂ polycrystals.

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Effect of surface ion-exchange of Georgia kaolin on the dispersion characteristics and the rheological properties were studied. The ion-exchange was carried out individually with mono-valent cations (Li⁺, Na⁺, K⁺), divalent cations (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Co²⁺), and tri-valent cations (Al³⁺, Fe³⁺), using corresponding chloride solution. The zeta potential increased positively from -30 to +7mV by the ion-exchange in the order of mono-<di-<tri-valent cations and simultaneously the viscosity of the slip increased, while the pH decreased from 6.2 to 3.7. Therefore, the zeta potential was considered to be strongly affected by the pH of slurry, but not by absorbed cations on the kaolinite particle. The water film thickness was evaluated by both the measurement of weight loss from 40 to 100°C for the green body and the DSC measurement. A positively linear relationship was observed on the values between the former and the later measurement, excluding trivalent cations, though the later values are about four-times higher than the former values. The water film thickness was increased by the ion-exchange with di-valent cations rather than mono-valent cations. The water film thickness is found to be related with the hydration energy of ion-exchangeable cations.

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The elimination of Pb²⁺ ion from aqueous solution was performed by adding calcium hydroxide solution or ammonium phosphate solution to a solution containing Pb²⁺ ion. The concentration of the filtrate was measured and the data were compared with those of the ferrite formation method. In the case of Ca(OH)₂ addition, the concentration of Pb²⁺ ion in the filtrate was affected by the Ca²⁺/Pb²⁺ ratio. The minimum concentration of 0.58mg/dm³ was obtained when the Ca²⁺/Pb²⁺ ratio was 1, where pH of the solution was 11.74. In the case of (NH₄)₃PO₄ addition, ill-crystallized Pb-hydroxyapatite was precipitated, and the concentration of Pb²⁺ ion in the filtrate was 0.01mg/dm³. The well-crystallized Pb-hydroxyapatite was obtained by the hydrothermal treatment of ill-crystallized one by using solution with pH of 12 at 150°C for 1h. This Pb-hydroxyapatite has lower solubility than lead hydroxide over a wide pH range. It is concluded that the method for elimination of Pb²⁺ ion from aqueous solution by using calcium hydroxide or ammonium phosphate were more effective than the ferrite formation method.

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Discs of typical engineering ceramics such as silicon carbide, alumina, zirconia and SiAlON were tested in the ball-on-disc type rolling contact fatigue mode using steel balls under lubricated conditions. The fatigue life of the ceramics increased in the order described above. By calculating the maximum tensile stress generated on the edge of a Hertzian contact area in the ceramic discs and comparing with the inherent strength of the material, it was possible to estimate whether the fracture mode depends on the Hertzian cracks or not. Although the cracks occurred in silicon carbide and alumina, no Hertzian cracks appeared in SiAlON materials in both the pressureless sintered and HIPed states for a stress level of 5.88GPa. It is also clarified that HIP treatment improves the fatigue life two orders of magnitude.

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Tl₂Ba_1.6Sr_0.4Ca₂Cu₃O_10+y(Tl-2223) superconductor coatings on Ag substrates were prepared using the electrophoretic deposition method. The Tl-2223 single phase was obtained by applying a high Tl composition of superconducting powder at the proper sintering conditions in order to prevent evaporation of Tl during the sintering process. Nominal Tl compositions of the superconducting powders were 2.00-2.50, which were stoichiometric and excess compositions. Electrophoretically deposited coatings using these superconducting powders were buried in the superconducting powder and sintered at 815°C for 6h in air. For the case of the nominal Ti compositions of 2.20-2.30, superconducting powders were used for the electrophoretic deposition, the Tl compositions of sintered superconductors were 1.80-1.87, the critical temperature (T_{c, zero}) was 110-112K, and these samples were almost single phase. On the other hand, Ag₂O powder was electrophoretically deposited onto the Tl-2223 electrophoretic deposition coating. After heat treatment at 315°C for 2h, the Tl-2223 pre-sintered superconductor coating was coated with silver. It was then sintered at 815°C for 6h. Although they were not buried during the sintering process, the Tl compositions of the obtained samples were 1.81-1.83 with a T_{c, zero} of 111-113K. This silver coat acts to restrain Tl evaporation and protects the coating of the superconducting layer. Moreover, the critical current density (J_c) of silver coated superconductor coating was 67A/cm² (77K, 0T) when a nominal Tl composition of 2.30 superconducting powder was used for the electrophoretic deposition.

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Amount of lead release from porcelain tableware, changes of the lead concentration distribution and the structure in the surface layer of the porcelain tableware during overglaze decoration firing in a water vapor atmosphere were investigated. Lead in the surface layer of the porcelain tableware was released by evaporation and surface exchange reaction between lead ions at the surface of the porcelain tableware and proton or hydronium ions in water vapor during firing in a water vapor atmosphere. Then the proton or hydronium ions introduced by the surface exchange reaction were released as water vapor formed by condensation reaction, and the silica-rich layer which contains α-quartz was formed at the surface This silica-rich layer was found to act as a protection layer against lead release.

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The piezoresistive property (gauge factor) of the strain sensor, which mainly consists of RuO₂/glass thick-film piezoresistor and a porcelain enamel substrate covered with partially crystallized glass, was investigated. The piezoresistive property of the piezoresistor on the enameled substrate was less than that on alumina. It was considered that the difference of the properties was caused by the interfacial reaction between the piezoresistor and substrate materials (crystallized glass and alumina). The interfacial reaction was recognized between piezoresistor and porcelain enamel substrate by scanning electron microscopy and thermal analysis (DTA). The piezoresistive property was improved with increasing of the thickness of the piezoresistor and Pb content (PbO/SiO₂ molar ratio) of glass composition. It is concluded that the degradation of the piezoresistive property was due to the interfacial reaction between the glass of piezoresistor and the partially crystallized glass covering substrate.

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A solid state electrochemical cell using the K⁺ ionic conductor, K₂O-Sm₂O₃-6SiO₂, as a solid electrolyte was investigated for monitoring carbon dioxide in air. At temperatures of 300 to 500°C, the electromotive force, EMF, of the sensor increased linearly with an increase in the logarithm of carbon dioxide partial pressure, in accordance with the Nernst's law. The slope of the Nernst's equation suggests two electrons reaction of carbon dioxide molecules at the detection electrode. The 90% response time of EMF of the sensor at 500°C was about 4min. The long-term stability of EMF of the sensor was essentially good after the 10th day.

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Continuous SiC fiber (Nicalon^TM) fiber-reinforced glass matrix composite was studied on microdamage evolution process by repeated thermal shocks at ΔT=700 and 800K. The composite was subjected to the shock up to five times. The multiple matrix crackings perpendicular to the fiber axis were observed at the surface and the number of crackings increased with the number of cycles, however, their depths were unchanged. The damage did not occurred at ΔT=700K while damage occurred at ΔT=800K and this temperature difference was about 400K higher than the damage initiation temperature difference of a monolithic glass matrix. Cracks parallel to through the thickness direction were also observed and the number of cracks increased with the increase of N. The characteristics of damage evolution process of the composite were discussed based on a set of the experimental evidences.

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This paper discusses the effect of addition of granulated blast furnace slag on the tensile strength of solidified concrete wastes using a hydrothermal hot-pressing method. Blast furnace slag of 0-100mass% was added to the concrete waste and NaOH solution was used as alkali-activator. Hydrothermal hot-pressing tests were carried out at 250°C with the water content of 10-30mass% under the pressure of 20MPa, The tensile strength of solidified bodies was determined by Brazilian test. It was shown that the formation of tobermorite and C-S-H compound improved the strength. The tensile strength reached at 13MPa under the following conditions; slag content: 50mass%, water content: 20mass%, NaOH addition: 1.75mass%.

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The effect of the addition of Ga₂O₃, a conditional glass former, on the glass-forming ability and superconducting properties of samples with Bi_2-xGa_xSr₂Ca₂Cu₃O_y (x=0-1.5) compositions has been investigated. The quantity T_x-T_g increases from 54 to 68K, indicating an improvement in the glass forming ability of the samples, where T_g and T_x are glass transition and crystallization temperatures, respectively. The superconducting properties deteriorate due to the migration of Ga ions into the 2212 phase: the superconducting critical temperature of the 2212 phase decreases from 85K for Ga-free sample to 72K for the sample with x=0.5, and the sample with x=1.5 shows semiconducting properties. The c-axis length of the 2212 phase decreases from 3.081nm for Ga-free sample to 3.074nm for the sample with x=0.5, but a-and b-axis lengths remain constant. A new Ga-compound formed in Ga-added samples was identified to be GaSr_0.55Ca_1.05Cu_0.5O_x. Superconducting phases of the Ga-based system are not formed even in Ga-rich samples.

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Silica-encapsulated palladium particles were formed from a palladium nitrate solution containing ultrafine SiO₂ particles by ultrasonic spray pyrolysis. The mechanism of the formation of the encapsulated particles was investigated. A precursor particle formed below 700°C in the drying stage was composed of the homogeneous mixture of the nano-sized SiO₂ and PdO⋅xH₂O particles. When PdO is decomposed above 700°C, metallic palladium particles are formed in the matrix of silica. Because of the high surface free energy, the metallic palladium particles coagulate and condense to the composite particle interior. As a result of the relocation within the composite particle, SiO₂ is forced out of the particle towards the surface to form a silica-encapsulated palladium particle.

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Carbon disulfide liquid was irradiated by Hg lamp at room temperature. Solid phase was obtained by the photochemical reaction of ultraviolet light, which was analyzed by EPMA, TENT, FT-IR and XPS. (1) It was photo-polymerized compound of carbon and sulfur rather than a mere mixture of products of photolis. (2) It was nano-crystalline or almost amorphous. (3) The bonding manner was different from other CS₂ solids prepared by high-pressure, plasma-polymerizing and anion catalyst techniques.

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Optically transparent MgIn₂O₄ thin films were prepared on SiO₂ glass substrates by a radio-frequency sputtering method. Direct current conductivity of the as-sputtered film was lower than 10^-9S·cm^-1. Lithium ions were implanted to the films at room temperature to a total fluence of 2×10¹⁵cm^-2. Carrier electrons were generated by the implantation. Conductivity of the as-implanted film was 8×10^-2S·cm^-1 and the carrier-generation-efficiency was -2%. By the post-annealing at 300°C, the efficiency drastically increased to -80% and the conductivity increased to 3S·cm^-1. These results indicate that the inactive Li⁺ ions in the asimplanted films are incorporated into the electrically active lattice sites during the post-annealing.

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