Lithium ion-conducting perovskite-type oxides, e.g., La_2/3-xLi_3xTiO₃ show high ionic conductivities as high as 10^-5-10^-3 Scm^-1 at room temperature. Their high conductivities are attributed to the percolation-controlled diffusion of lithium ions via vacancies in the A-site-deficient perovskites (general formula of perovskite-type oxide: ABO₃). The strong correlation between structure and percolation-controlled diffusion in the perovskites is primarily referred to the arrangement of A-site ions, and the “bottleneck” square-surrounded by four oxygen ions. The bottleneck size, i.e., the repulsion for lithium ions by the electronic clouds of oxygen ions, is dependent on the distortion and tilt of the BO₆ octahedra, which relate to the difference of skeletal ions, Aand Bcations, i.e., tolerance factor and their chemical characters, and is the predominant factor of the activation energy for ion migration. These findings were confirmed by powder X-ray and neutron structural refinements, composition, temperature and hydrostatic pressure dependences of ionic conductivities, and molecular dynamics simulations.

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A porous material having near zero thermal expansion (NZTE) around room temperature was developed. This material was prepared by sintering a mixture of SiC, vitrified bonding material (VBM) and LiAlSiO₄ at 850°C. LiAlSiO₄ was added in different weight proportions, and it was found that a change in the amount of LiAlSiO₄ leads to a material with NZTE at room temperature, porosity around 50%, and Young's modulus around 14 GPa. Through X-ray diffraction (XRD) and scanning electron microscopy (SEM) it was determined that no reaction occurred between SiC and LiAlSiO₄ during sintering, and they are joined by the VBM, which melted at the sintering temperature. In conclusion, the addition of LiAlSiO₄ and VBM to SiC, allowed the development of porous SiC materials having NZTE at room temperature.

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The ball-milling for amorphous calcined powder in a PMMA solution, prepared by heating a mixture of nitrates, γ-Al₂O₃, and amorphous SiO₂ powders were effective for the fabrication of Ca-substituted leucite porous bodies with almost homogeneous pore-size distributions. Especially, when the amorphous powder calcined at 1073 K was ball-milled for 48 h, the pore size decreased to 0.159 μm and porosity increased in the porous body fabricated using the amorphous calcined powder. The FT-IR spectroscopy revealed that the amorphous calcined powder is composed of fine particles having a network of (Si, Al)O₄ tetrahedra similar to the aluminosilicate framework of the leucite compounds. The fabricated porous body showed a low linear thermal expansion coefficient of 1.405×10^-6/K in the temperature range of 298 to 1273 K.

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SnO₂ layers were prepared using an electrospraying pyrolysis method from a SnCl₂-ethanol solution, where the effect of the preparation condition on the morphology was investigated. A substrate temperature and a precursor concentration were the determining factors in the morphology. Cracked films were obtained below 250°C. A unique network structure appeared at 281°C, which resulted from the melting of the SnCl₂ and the gas release with the pyrolysis on the substrate surface. Layers prepared above 281°C were composed of~100 nm particles. These particles were formed from the electrosprayed droplets during the flight. The electrostatic force affected the accumulation manner of the particles. The preferential landing of arriving particles on those previously deposited on the substrate resulted in dendrite-type thick layers. When the concentration was 5×10¹ mol m^-3 and above, shells were formed during the vaporization of the solvent. It brought about unshaped layers embedded with hollow particles.

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Silicide-particle-reinforced Si₃N₄ composites with a crystallized grain boundary phase of Yb₂Si₂O₇ were synthesized in-situ by hot-pressing Si₃N₄ with the metal oxides M_pO_q (silicide-forming oxides), which can react with Si₃N₄ to form silicide, and Yb₂O₃ as sintering additives. The reaction between Si₃N₄, silicide-forming oxide (Ta₂O₅ or MoO₃) and Yb₂O₃ at high temperatures generated silicide (Ta₃Si or Mo₅Si₃) particles and a grain boundary phase, Yb₂Si₂O₇, simultaneously. The silicide particles mainly existed at the grain boundaries, but a small amount of Ta₃Si particles were detected from Si₃N₄ grains. Ta₃Si particle grew up to a polyhedron shape, but Mo₅Si₃ particle to a spherical shape. To obtain the crystallized grain boundary phase of RE₂Si₂O₇, the molar ratio of Yb₂O₃ to M_pO_q should be adjusted to q/4 (q: the number of oxygen atoms in M_pO_q). However, because a small amount of oxygen was included in Si₃N₄ powder and existed on the surface of Si₃N₄ as SiO₂, the excess SiO₂ reacted with Si₃N₄ to generate a trace of Si₂N₂O grain. In the silicide-Yb₂Si₂O₇-Si₃N₄ composites, the grain boundary phases were crystallized, but thin amorphous films with a thickness of 1 nm were detected from the interfaces between the silicide particle, Si₃N₄ grain, and the grain boundary phase of Yb₂Si₂O₇. The dense silicide particles reinforced Si₃N₄ matrix composites can be obtained by using this in-situ synthesis method, and the flexural strength and fracture toughness of Ta₃Si-Yb₂Si₂O₇-Si₃N₄ composite were 1209 MPa, and 6.0 MPa•m^1/2, respectively.

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Low-temperature decomposition of sprayed-on asbestos was studied in the presence of flon-decomposition products or CaCl₂-CaCO₃ mixtures. In a reaction system to which flon-decomposition products were added, chrysotile and its decomposition product, forsterite, maintaining the needle form underwent destruction by heating at 800°C for 2 h. The optimum mixing ratio of the sprayed-on asbestos to the flon-decomposition product was obtained when the content of the latter was very slightly larger than that for the asbestos/flon-decomposition product ratio 2/1 by weight. When the sprayed-on asbestos mixed with the CaCl₂ was heated at 700°C, forsterite as well as chrysotile in the material were completely decomposed.

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The influence of particle size distributions of submicron high-purity α-alumina powders on forming and sintering behavior in an agglomerate-free condition were investigated. Nine kinds of alumina powders with the same median diameter (d_PM50=0.53 μm) and different geometrical standard deviations (σ=1.2-2.0) in lognormal particle size distributions were prepared by blending spherical-like commercial α-alumina powders, and were also adjusted to near ideal distributions so that σ of a mass distribution was comparable with one of the number distribution. In order to prevent the agglomerate and contamination of the impurities, forming was performed by means of the colloid process, i.e., the slip casting method using the porous alumina molds. Relative densities of green compacts and bodies sintered at up to 1300°C increased with increasing σ, but densities of bodies sintered at 1500°C or more increased with decreasing σ. The width of the grain size distributions of those bodies increased with increasing σ. The abnormal grains over 30 μm of the grain size generated at more than 1.7 of σ for alumina bodies sintered at 1700°C and those grains contained many pores. The powder with a narrow distribution in size is better to fabricate a translucent material.

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Tungsten carbide including cobalt, WC-Co, shows good performance for high temperature toughness and is expected when applying to a high temperature mold but it is difficult to cut into ultra-fine precision because of its brittleness. In this study, WC-Co surface is treated by a pulsed laser irradiation to softening and cleaning in a machining liquid and cutting test by Vickers indenter. Under the case of Methyl n-Nonanoic acid, the surface wetness shows same behavior for with and without laser cleaning. In this case, the surface fracture by the cutting is extended and a lot of damages are generated along the cutting track for both as polished surface and laser cleaning surface. Under the case of n-Undecyl Alcohol and Palmitic acid n-Butyl Ester, the surface wetness is improved by the laser cleaning and the surface fracture is inhibited by the laser cleaning. As results of the FT-IR measurements of Palmitic acid n-Butyl Ester on the WC-Co surface, the peak position of C-H stretching mode (2900-2950 cm^-1) shifted from a lower wavenumber (on the surface of as polished) to a higher wavenumber (on the laser cleaning surface). This result indicates that the Palmitic acid n-Butyl Ester interacts with the WC-Co surface and influences to the surface fracture of the laser cleaning WC-Co surface, where it is restrained by the surface adsorption.

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Detoxification of crocidolite particles in sprayed crocidolite was performed by a combination of heating and grinding treatment. Crocidolite crystal was detected XRD analysis in the sample heated at temperatures below 800°C for 3 h, but not after heating at 900°C for 3 h. Although crocidolite crystal remained in the sample heated at the temperatures over 500°C, the crocidolite particles could be easily ground using a mortar to smaller than several micrometers in size, which is safe for the human body (below 8 μm). However, crocidolite crystals could not be detected using phase-contrast microscope after heating at temperatures higher than 500°C for 3 h.

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The water vapor oxidation behavior below 1000°C for porous silicon carbide ceramics with and without additive alumina was investigated. The relationship between the microstructure of porous SiC and vapor oxidation was examined. The varied microstructures, such as pore size and particle size were found to affect the water vapor oxidation behavior of porous SiC. The porous SiC without alumina showed a good stability for water vapor. This was due to the microstructure of large particles and pores in the undoped SiC. In contrast, the porous SiC with alumina after vapor oxidation showed the microstructural changes such as the increase of pore size and particle size, and the disappearance of fine particles, because the porous SiC with alumina was composed of fine particles and small pores.

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Perovskite-type oxyfluoride systems, ABO₃-BaLiF₃ (A=Ba, Ca and B=Ti, Zr) were investigated. In the Ba(Ti_1-xLi_x)O_3(1-x)F_3x system, cubic phases appeared in the range, 0.2≦x≦0.4. In the (Ca_1-xBa_x)(Zr_1-xLi_x)O_3(1-x)F_3x system, orthorhombic phases different from CaZrO₃ appeared in the range, 0.4≦x≦0.5. The lattice volumes of the new phases were larger than those of the respective end-members. On the other hand, the Ca_1-xBa_xTi_1-xLi_xO_3(1-x)F_3x samples showed two phases of CaTiO₃ and BaLiF₃, of which lattice constants were almost independent of the composition.

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The influences of oxidation treatment on the microstructure and strength retention of a Mo₅Si₃ particle reinforced Si₃N₄ composite with a crystallized grain boundary phase of Yb₂Si₂O₇ were studied. When the Mo₅Si₃-Yb₂Si₂O₇-Si₃N₄ composite was oxidized at 1400°C, an oxide layer containing cristobalite and Yb₂Si₂O₇ was created on the surface. The thickness of the oxide layer increased with oxidation time, but was only 1.8 μm when oxidized at 1400°C for 100 h. The formation of the oxide layer caused the weight gain of the composite, and a parabolic weight gain with respect to oxidation time was observed. After 100 h of oxidation at 1400°C in air, the weight gain of the Mo₅Si₃-Yb₂Si₂O₇-Si₃N₄ composite was 0.07 mg/cm², is considerably less than that of other Si₃N₄-based materials. The crystallization of the grain boundary phase and the incorporation of the submicrometer Mo₅Si₃ particles into the grain boundaries decreased the driving force for the diffusion of oxygen and the additive cation, and contributed to the high oxidation resistance of Si₃N₄.

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