Instrumentation and data analysis techniques for the crystal structure analysis using SR and laboratory X-ray powder diffraction data have been described. The SR powder diffractometer with the MDS has been developed, and it has been used for obtaining high-resolution powder diffraction intensity data at the PF in Tsukuba. The whole-powder-pattern decomposition method, incorporating the sophisticated profile function, has been developed, and integrated intensities of individual reflections could be extracted easily from complex powder patterns. The integrated intensity data sets thus obtained were used for solving crystal structures ab initio by direct methods and/or direct-space methods. At a final stage of crystal structure analysis of crystalline powder, structural parameters are refined by the Rietveld method. Accuracy of the refined structural parameters has been greatly improved by the introduction of the new weight function into the least-squares refinement. Developments of both the instrumentation and the analysis techniques operate complementarily in order to surmount the difficulty intrinsic in the powder diffraction method

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Lithium zirconate (Li₂ZrO₃) has been developed for application as a novel CO₂ absorbent. This material reacts immediately with CO₂ in the temperature range of 450 to 550°C. Moreover, the products react and revert reversibly to Li₂ZrO₃ at temperatures above 650°C. The possibility of a CO₂ separation system utilizing this reaction and operating at around 500°C is suggested. The absorption is ascribed to the mechanism whereby lithium oxide in the Li₂ZrO₃ crystal structure reacts reversibly with CO₂. However, this material has the disadvantages of heavy weight and high cost due to the use of ZrO₂. On the basis of the above mechanism, a series of lithium silicates were considered as candidates for new CO₂ absorbents, and their CO₂ absorption properties were evaluated by TG analysis. Furthermore, in order to confirm the reaction, phase analysis was conducted by XRD.

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BaTiO₃ thin films were prepared on Pt/Ti/SiO₂/Si substrates in a water-methyl alcohol mixed bath, nearly saturated with barium nitrate, by potentiostatic electrochemical deposition. Weights and compositions of the as-grown films were controlled by regulating electrochemical parameters such as the electrode potential, the quantity of electricity, and the concentrations of Ti (IV) peroxo complexes in the electrolysis bath. Ba/Ti ratios in the as-grown films were constant along the depth direction. No impurity in the as-grown films was detected. The as-grown films were amorphous, and Ba²⁺ ions in them were present mainly as barium nitrate. Polycrystalline BaTiO₃ thin films were obtained by annealing above 500°C for 1h in air. The BaTiO₃ thin films were crystallized at a relatively low temperature of approximately 500°C due to easy decomposition of barium nitrate to barium oxide and nitrous gas during annealing.

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Details of α→β Si₃N₄ phase transformation, microstructural development and mechanical properties of SiC reinforced-Si₃N₄ matrix nanocomposites were investigated. Two sintering aid systems were used: 7.5mass% MgAl₂O₄+7.5mass%ZrO₂ (MA-Z) and 10mass%Y₂O₃+4mass%Al₂O₃ (Y-A). The MA-Z system enhanced α→β phase transformation at low temperatures (1400-1550°C), which was interpreted to arise from nucleation of β-Si₃N₄ upon the SiC addition. This phenomenon was not observed in composites added with the Y-A system. Due to a large number of β-Si₃N₄ nuclei, microstructure of Si₃N₄/SiC nanocomposites added with the MA-Z system exhibited a reduced grain growth and high flexural strength.

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Transition metal oxide (TiO₂, ZrO₂, Nb₂O₅ and Ta₂O₅) tubes were synthesized by using organic crystal with needle-like form i.e. ammonium dl-tartrate as a template in sol-gel reaction. First, ammonium dl-tartrate crystals were precipitated and rapidly grown to needle-like form when concentrated ammonia was added to ethanol solution containing dl-tartaric acid. Next, the transition metal oxide was deposited only on the side faces of the template crystals when corresponding metal alkoxide was added into the ethanol solution containing the crystal templates and stirred. After deposition of the oxide layer on the side faces of the crystals, the central templates were removed by washing with water to form hollow tubes with rectangular outer shapes and inner channels. The size of the thus formed tubes were ca. 40-200μm in length, 1.3-5.9μm in width, 1.0-4.9μm in channel width and 0.2-0.7μm in wall thickness. It was found from FT-IR and powder XRD that every kind of tube was present as amorphous oxide gel. The specific surface areas and pore size distribution of as-prepared tubes significantly varied depending on the kind of alkoxides. The uniformity of hydrolytic polycondensation of alkoxides and the amount of hydrated water in gel might affect the microporous structure of the tubes. The present template method using water-soluble ammonium dl-tartrate crystal could be effective for synthesizing micron-submicron sized transition metal oxide tubes according to a simple process.

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The essential prerequisite for an artificial material to show bone-bonding ability, i.e., bioactivity, is the formation of a bone-like apatite layer on its surface in a body environment. This can be reproduced in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. It is known that some surface functional groups are effective for inducing heterogeneous apatite nucleation in SBF. Niobium is used clinically as a component in titanium alloys to improve their workability. In the present study, in order to investigate whether or not Nb-OH groups are effective for apatite nucleation, sol-gel-derived niobium oxide gels subjected to various heat treatments, and niobium metals subjected to various NaOH treatments were examined for their apatite-forming ability in SBF. The sol-gel-derived niobium oxide gels, both as-prepared, and heat-treated at 600°C, assumed an amorphous structure, and those heat-treated at 800 and 1000°C assumed orthorhombic and monoclinic structure, respectively. Apatite formation was observed on the niobium oxide gels both as-prepared, and heat-treated at temperatures below 800°C in SBF within one week, but not on the gel heat-treated at 1000°C. Niobium metals treated with the NaOH solutions did not form apatite on their surfaces, even after soaking in SBF for two weeks. It was confirmed that niobium metal formed a sodium niobate on its surface after the NaOH treatment, and that the sodium niobate formed a niobium oxide hydrogel by exchange of a Na⁺ ion with the H₃O⁺ ion in SBF. Niobium oxide gels prepared by the sol-gel method have the ability to form an apatite layer on their surfaces in a body environment, when the gel has an amorphous phase structure, or an orthorhombic phase with abundant Nb-OH groups. Apatite deposition is not induced by Nb-OH groups formed on niobium metal after NaOH treatment and subsequent soaking in SBF. A niobium-based bioactive material can be developed through the design of a surface structure that effectively induces apatite nucleation.

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Temperature-dependence of various mechanical properties of Si-Ti-C-O fiber-bonded ceramic is investigated. The material was produced by hot-pressing the laminae of oxidized satin-woven Si-Ti-C-O fibers, and then showed very high fiber-volume fraction (around 0.85) and very little porosity, compared with ordinary ceramic matrix composites. The in-plain tensile, compressive and inter-laminar shear strengths of the material at room temperature were maintained up to 1400°C, whereas the Young's modulus and the compressive strength of out-plain direction (transverse direction) decreased at 1400°C. The behavior toward the tensile and inter-laminar shear strengths were in good agreement with the changes in fiber pull-out length and delaminating position, respectively. A buckling of the fibers parallel to the stress axis and a large deformation of the specimen were observed in the fracture surface after compression tests of in- and out-plain directions at 1500°C, respectively. From the differences in the mechanical properties and fracture morphologies, it was concluded that the change in the fracture strength at the high temperature was caused by softening of the amorphous SiO₂ phase.

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The purpose of this paper is to interpret the enhancement of T_c and J_c by the replacement of cations and the change of excess oxygen content for Bi-rich 2212 system, (Bi_2.1-xPb_x)Sr_2.0(Ca_0.9Y_0.1)Cu_2.0O_y, especially in overdoping region. The bulk samples were prepared by coprecipitation method. In bulk samples, the c-axis and Bi+Pb valence decrease and Cu valence increases with increasing Pb content, x. T_c(zero) increases with increasing x in the single phase region. On the other hand, the c-axis and Cu valence increase and Bi+Pb valence slightly increases with increasing excess oxygen content, Δy. An optimum excess oxygen content which brought a maximum T_c(zero) was found to exist at each Pb content. Furthermore, in order to elucidate the effects of metal substitution and oxygen content on J_c of the Bi2212 system, the films with the same metal compositions were prepared by the spin coating pyrolysis method. From the results of highly orientated thin films, J_c increases with increasing excess oxygen content, Δy, in the oxygen doping region, while it increases or keeps constant in the oxygen overdoping region. According to the results, the metal composition and oxygen content are very important for obtaining the highest T_c and J_c.

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Metal-graphite composites having two types of microstructure were fabricated by powder metallurgical processing, and their thermal conductivities were measured to design heat spreaders. The microstructures and thermal conductivities of composites fabricated by a pressurized sintering were anisotropic. The inplane thermal conductivity increased from 350 to 443W/mK with increasing graphite content from 50 to 75vol%, which was much higher than the through-plane value from 100 to 63W/mK. The calculated thermal barrier conductance h_c) of the metal-graphite interface in the composites was 1.9 to 2.1×10⁷W/m²K. On the other hand, a composite having a graphite content of 74.8vol%, which was fabricated using a combinated technique of the cold isostatic pressing (CIP) and a infiltration method, had an isotropic thermal conductivity of 265W/mK. Based on the above data, the cooling performance of the anisotropic composite having a graphite content of 75vol% as heat spreaders for a microprocessor unit was calculated using three-dimensional FEM. The calculation indicated that as the thickness of the composite decreased, the cooling performance of the composite approached that of pure Cu heat spreader having the same thickness.

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Fine cadmium sulfide (CdS) powder was prepared from metal alkoxide. Using this powder, CdS films were fabricated. The CdS films were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The CdS powder was synthesized by sulfurization of Cd(OR)₂ (R=CH₃, C₂H₅) or Cd(OH)₂, and Cd(OH)₂ was derived from the hydrolysis of Cd(OR)₂. CdS pastes were manufactured by dispersing the resultant CdS powder into a mixture of terpineol and ethylcellulose using a three-roll mill. CdS pastes were screen-printed on glass substrates and dried. The CdS films were heat-treated at 300-600°C in a N₂ atmosphere, and examined by XRD. Preferred orientation in the [002] direction was observed for CdS films obtained from Cd(OH)₂. On the other hand, in the case of CdS films obtained from Cd(OR)₂, no preferred orientation was observed.

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The diffusion characteristics of Ni ion were evaluated in non-doped, Ho-doped polycrystalline and single-crystal barium titanate perovskite (BaTiO₃) using a secondary ion mass spectrometry (SIMS). The volume diffusion coefficients of Ni (1100≤T≤1400°C) were described as follows; non-doped BaTiO₃: D_v[cm²/s]=1.4×10^-6exp(-241.9[kJ/mol]/RT), Ho-doped BaTiO₃: D_v[cm²/s]=4.4×10^-6exp(227.7[kJ/mol]/RT), single-crystal BaTiO₃: D_v[cm²/s]=6.7×10exp(-437.2[kJ/mol]/RT). The difference of diffusion coefficients could be explained through of the defect chemistry. The grain boundary diffusion was also estimated by using the same method. It was indicated that grain boundary diffusion was influenced by the microstructure.

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The relationship between mass loss of Si₃N₄ ceramics during heat treatment and heat treatment temperature was quantitatively examined to elucidate the rate-determining factor of mass loss. Sintered Si₃N₄ ceramics were heat-treated at 1823-2098K under 0.1MPa N₂ and mass loss during heat treatment was measured. The mass loss increased with increasing temperature and the slope of the Arrhenius plot of the mass loss rate was similar to that of the equilibrium gas pressure of SiO generated from the mass loss reaction of Si₃N₄ ceramics. This finding suggests that the rate-determining factor of mass loss is the diffusion rate of SiO to the outside of the sagger.

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The authors evaluated the characteristics of large particle size Ni powder used in the fabrication of internal electrodes of multilayer ceramic chip capacitors (MLCs). The effects of large particle size on the sintering characteristics of Ni powder for use as electrode films have been studied. A high green density was obtained for the increase of pulverized Ni powder of 1.0μm. The experimental results revealed that 1.0μm Ni powders were homogeneously dispersed in the paste. From shrinkage measurements of Ni electrode films with thickness of approximately 200μm, which were formed by an applicator and sintered at temperatures from 400 to 800°C, it was observed that films composed of increased amount of 1.0μm Ni powder showed a smaller shrinkage than that of 0.6μm Ni powder only. A similar result has been observed for the microstructure of sintered electrode films.

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Coal combustion by-product fly ash was converted selectively into faujasite (Y type) zeolite and was used as a catalytic material. The conversion process tried to alleviate the disposal problem of large amounts of fly ash, and turned fly ash into useful materials. Fused fly ash powder and supernatant were used in the synthesis of Y type zeolite. The prepared Na-Y zeolites were characterized and ion-exchanged followed by calcinations to obtain H-Y. The catalytic properties of the solid obtained were evaluated using cumene cracking and compared with those of commercially available (standard) zeolites. It was found that most of the Si and Al components in the fly ash could be effectively transformed into Y type zeolite in the presence of seeds but not the mineral phase, such as mullite. Moreover, the supernatant of the fused powder solution can produce purer faujasites and the sediment can be reused to generate solution for the further preparation of zeolites. Investigation by NMR demonstrated that fusion plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. The H-Y zeolite derived from the supernatant of fly ash solution shows excellent cracking activity compared to that of standard.

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Hydrothermal synthesis of lithium manganese oxide with α-NaFeO₂ structure has been studied. A Li_xMnO₂⋅nH₂O, (Li-birnessite), with rhombohedral symmetry was used as a starting material. When the molar ratio of Mn/Al was smaller than 0.9/0.1, spinel type lithium manganese oxides were obtained. On the other hand, when the molar ratio of Mn/Al was larger than 0.85/0.15, metastable lithium manganese oxides with α-NaFeO₂ structure formed at 80°C, and the capacity fade of the Li-ion cell with cathodes made of these oxides was very small in comparison with that of cathodes made of layered Li-manganese oxides, as previously reported.

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Synthesis of porous silicon nitride (Si₃N₄) by using seed crystals was studied. Seed crystals were prepared by heating a powder mixture of α-Si₃N₄ and sintering aids. Y₂O₃ was the most effective additive for obtaining seed crystals of high aspect ratio. By adding rod-like seed crystals to α-Si₃N₄ starting powder, porous Si₃N₄ with relatively high porosity could be fabricated. In the case of adding 50vol% seed crystal, rod-like grains were well combined, forming a framework. The effect of sintering additives on porosity of the porous body was also studied. By adding 5mass%Y₂O₃ and 2mass%Al₂O₃ as sintering additives, the porosity of sintered body was reduced.

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