Bi₄Ti₃O₁₂-PbTiO₃ micro-composite particles, Bi₄Ti₃O₁₂ core particles covered with PbTiO₃ particles with an epitaxial relationship, were synthesized. Bi₄Ti₃O₁₂ particles with a plate-like morphology were prepared by a molten salt technique and used as core particles. The Bi₄Ti₃O₁₂ particles were coated with titania by the hydrolysis of Ti-alkoxide. The thickness of the titania coating layers was easily controlled between 0.1 and 0.5μm by the concentration of Ti-alkoxide. The composite particles were prepared by the hydrothermal treatment of the titania-coated Bi₄Ti₃O₁₂ in alkali solutions containing Pb. The formation of PbTiO₃ depended both on temperature and on the concentration of Pb in the solution. The PbTiO₃ particles with the sizes of 0.1-1μm were formed on the surfaces of the Bi₄Ti₃O₁₂ core particles at temperatures≥160°C in the solutions with the excess Pb of 4-6mmol. The combined results of SEM and TEM observations revealed that there was an epitaxial relationship between Bi₄Ti₃O₁₂ and PbTiO₃ of a composite particle, such that {100} or {001} PbTiO₃//pseudotetragonal {001} Bi₄Ti₃O₁₂.

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Si₃N₄/SiC composites containing 0-30 vol% SiC were fabricated by pressureless sintering and sinter-post-HIPing method using fine Si₃N₄ and nano-sized SiC powders. Specimens reached full density (>96% theoretical density (th.d.)) except the composites made by pressureless sintering which contained a small amount of sintering additives or a large amount of SiC. All composites with 10 mass% sintering additives reached full density (-99% th.d.) by sinter-post-HIPing. The addition of SiC particles greatly influenced the grain morphology of the Si₃N₄ matrix. The average grain thickness, length and aspect ratio decreased with increasing SiC content because of grain boundary pinning by SiC particles. Also the mechanical properties were markedly dependent upon the fraction of SiC particle reinforcement, as well as matrix grain size and porosity. When the materials were pressureless sintered, the strength of the composite increased with SiC additions below 20 vol%. Further increase in the SiC content resulted in a corresponding decrease in strength. Maximum strength of 1150MPa was attained at 20 vol% SiC addition. The increase in strength by addition of SiC is due to decrease of grain size of Si₃N₄ matrix grain size, and the decrease by further increase in SiC content is caused by porosity and SiC agglomerate. On the other hand, toughness decreased monotonically with SiC content. The strength of all samples was enhanced by sinter-post-HIPing without any change in fracture toughness. The strength of sintered samples with 10-15 vol% SiC increased by -20% to 1260MPa by post-HIPing. The increase in strength by post-HIPing was interpreted as being due to a decrease flaw size.

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NdFe_0.5Co_0.5O₃, a trimetallic perovskite-type oxide, was prepared by thermal decomposition of a synthesized heteronuclear complex of Nd[Fe_0.5Co_0.5(CN)₆]⋅4H₂O. Using XRD, the perovskite-type phase was detected in the sample heated at 500°C and the complex was completely decomposed to NdFe_0.5Co_0.5O₃ at 700°C. Distribution of the elements Nd, Fe, and Co on the surface of the complex that decomposed at 800°C were homogeneous according to Auger electron spectroscopy (AES) analysis, For a solid-state reaction method using a mixture of single oxides (Nd₂O₃, Fe₂O₃ and CoO), a high heating temperature (>1000°C) is needed to form a single phase of the perovskite-type oxide. Fe-rich and Co-rich regions on the surface were clearly detected even in a mixture calcined at 1100°C. Surface concentration and structure of samples obtained by both methods were investigated by X-ray photoelectron spectroscopy (XPS). For both samples, XPS revealed that the (Fe+Co)/Nd ratio was less than unity.

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Electronic structure in the conduction band of CaTiO₃ was examined by the bremsstrahlung isochromat spectroscopy (BIS), X-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS). Two broad bands were observed at 2 and 7eV above the Fermi energy in the BIS spectrum. The features of the XAS spectra for Ca L_{2, 3}, Ti L_{2, 3}, and O K edges were almost the same as those of the EELS spectra, and the XAS spectrum for each element was in reasonable agreement with its partial density of states estimated by an energy band calculation. A trial spectrum was synthesized by the sum of the XAS spectra, and it was found that the feature of the synthesized spectrum is similar to that of the BIS spectrum. From the comparison between XAS and BIS spectra, the two broad bands at 2 and 7eV in the BIS spectrum were assigned to Ti 3d bands and Ca 4s bands, respectively.

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Delamination cracks in ceramic composite materials may be bridged by misaligned or inclined fibers at a shallow angle. The in situ observation of delamination cracks in a Si-Ti-C-O fiber-bonded ceramic composite material reveals that the bridging fibers are subjected to increasing tensile stresses as the crack opening displacement becomes larger. These stresses cause a crack closure pressure that is considered to contribute to steady state transverse fracture toughness. To relate the crack closure pressure to the material properties of fibers, matrix and their interface, a two-dimensional FEM model of a misaligned fiber bridging the crack wake at a shallow angle was constructed. Crucial mechanisms such as fiber debonding and frictional sliding along the debonded interface as well as matrix chipping were included. The crack closure pressure was simulated as a function of COD and the influences of these mechanisms were discussed. The toughening effect of bridging fibers was estimated and the obtained results were compared to the experimental data for a Si-Ti-C-O fiber-bonded ceramic composite material.

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Fine-grained and adherent diamond coating was obtained by the two-stage microwave plasma chemical vapor deposition (CVD) in the CO-H₂ system on a tungsten wire substrate mounted horizontally 2mm upward on pyrophyllite susceptor. The susceptor was placed parallel to the irradiation direction of microwave. The nucleation density of diamond was found to increase with increasing the microwave power up to 1000W. The first stage CVD conditions for fine-grained diamond coating on tungsten wire were determined as microwave power: 900W, pressure. 2kPa and CO concentration: 5 vol%. On the other hand, the second stage CVD conditions for higher growth rate of diamond film were determined as microwave power: 550W, pressure: 4kPa and CO concentration: 10 vol%. Homogeneous and adherent diamond coating with a thickness of 16μm was prepared by the two-stage CVD process for a total treatment time of 10h (the first stage of 3h and the second stage of 7h) on tungsten wire of 1.0-mm diameter. A WC interlayer was formed during the CVD process.

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Electron back scattered diffraction (EBSD) method was applied to examine the crystallographic orientation of ceramics, microstructure on a large scale. This method is given in altermotive to transmission electron microscopy, which gives information limited to a narrow portion of the specimen. To prove that the EBSD method can be applied to analyze the crystallographic orientation of ceramics, we have verified the crystallographic orientation of single crystal ceramics of cubic and corundum structures using a field emission scanning electron microscopy (FE-SEM) coupled with an orientation imaging microscopy analysis device. Then, also the crystallographic orientation of in situ Si₃N₄ composite was analyzed by the EBSD method. Results of the EBSD characterization showed that in Si₃N₄ ceramics of hexagonal structure the elongated Si₃N₄ particles grew in the alignment direction of seed grains. The growth direction and the side planes of the elongated Si₃N₄ particles were influenced by both the alignment of seed grains and by the hotpressing pressure.

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The most suitable condition to prepare a hardened hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) body from amorphous calcium phosphate (Ca₃(PO₄)₂⋅nH₂O, ACP) was investigated to develop a bioxnaterial for the repair of bony defects. The hardened HAp bodies were prepared by mixing dicalcium phosphate dihydrate (CaHPO₄⋅2H₂O, DCPD), various carboxylic acid solutions and amorphous tricalcium phosphate (ATCP) obtained by heating ACP at 500°C. The properties of the hardened HAp bodies were characterized by measuring compressive strength and X-ray diffraction. The compressive strength of the hardened bodies depended on the amount of DCPD, types of carboxylic acids, concentrations of carboxylic acid solutions, water/solid weight ratios, aging time and temperature. Particularly, the type of carboxylic acid considerably influenced the compressive strength. For example, utilization of glycine as a carboxylic acid showed a value of 5.5MPa in compressive strength at maximum although that of maric acid showed a value of only 3.0MPa. The values of compressive strength were positively correlated to the first dissociation constant. Glycine was found to be effective to increase the compressive strength of the hardened bodies.

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Cadmium telluride (CdTe) was synthesized by thermal decomposition of metal alkoxide at temperatures as low as 300°C. The influences of alkoxide species and their atmosphere of decomposition have been investigated. Thermal decomposition was carried out in three different atmospheres: Air, N₂ and H₂. CdTe double alkoxides, which were prepared by the reaction of Te-alkoxide in the presence of Na-alkoxide with cadmium acetate, produced CdTe powders by its thermal decomposition in H₂ atmosphere. The primary particle size of the powders obtained was submicron, and however, particles agglomerated to several micrometers in diameter. When the CdTe double alkoxides were decomposed in Air or N₂ atmosphere, CdTeO₃ was obtained. The Cd-alkoxide was insoluble in toluene solution of Te-alkoxide even at a refluxing condition. Thermal decomposition of the supernatant after reacting solid Cd-alkoxide with Te-alkoxide in toluene for 20h yielded Te metal with a small extent of CdTe in H₂ atmosphere. The formation of CdTe was also discussed based on thermodynamic data.

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The effect of SiC-CVD coating on the flexural strength of metal boride particle dispersed SiC was investigated. Compressive residual stress was detected in the CVD-SiC coating on the TiB₂/SiC specimen. The compressive residual stress was thought to arise during the cooling process from the CVD processing temperature, i. e., from 1300°C to an ambient temperature because of the larger coefficient of thermal expansion of TiB₂/SiC as compared to CVD-SiC. The compressive residual stress increased with the volume fraction of TiB₂. The CVD coating layer fractured and separated from TiB₂/SiC at volume fractions of TiB₂≥35 vol%. The compressive residual stress stored in the SiC-CVD coating affected the flexural strength of CVD coated TiB₂/SiC. The flexural strength increased by the CVD coating from 583 to 767MPa at room temperature. The flexural strength was decreased by the SiC-CVD from 767 to 610MPa at 1450°C. The change of flexural strength of SiC-CVD coated TiB₂/SiC with temperature was thought to be related to the evolution of thermal residual stress. At lower temperature than the CVD processing temperature, the compressive residual stress induced on the surface of CVD coating enhanced the flexural strength of TiB₂/SiC. On the other hand, higher temperatures than the CVD processing temperature, tensile stress was induced on the surface CVD coating and the flexural strength of TiB₂/SiC decreased.

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Dispersion effect of polyoxyethylene-type surfactants on aggregation of alkoxide-derived SrTiO₃ particles in water as well as the influence of these surfactants for preparation of SrTiO₃ ceramic sheets were studied. Seven kinds of surfactants were examined. Among these surfactants, a surfactant having carboxyl group was effective on dispersing aggregated of SrTiO₃ particles. This surfactant was soluble in water. The surfactant solution behaved as a Newtonian fluid. The density and viscosity of the 7.5 mass% surfactant solution were 1.0411g⋅cm^-3 and 2.3mPa⋅s. The green sheet could be prepared using a SrTiO₃ particles-water system suspension in which aggregation of SrTiO₃ particles was controlled by addition of the surfactant. This green sheet was composed of fine particles with a diameter of less than 1μm. These constituent particles of the green sheet were finer than that in the green sheet formed without the addition of surfactant. SrTiO₃ ceramic sheets could be obtained with successive sintering of the green sheets at 1300°C.

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The effects of shape, crystallinity and specific surface area of ZnO powder on antibacterial activity were studied by measuring the change in the electrical conductivity with bacterial growth. From the results, it was clarified that the antibacterial activity increased with the increase of powder concentration in the physiological saline. The antibacterial activity against Escherichia coli strongly depended on the specific surface area of the powder; the activity increased with the increase of the surface area, irrespective of the shape and the crystallinity of their powders. In the case of Staphylococcus aureus, however, it was found that there was no difference in the activity according to the characteristic of the powders. The appearance of antibacterial activity was found to be due to the generation of H₂O₂ from the surface of ZnO powder.

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An attempt was made to produce lead titanate particles with a sol-gel process which adopted the hydrolysis and condensation reactions of complex alkoxide prepared from Pb (O-i-C₃H₇)₂ and Ti(OC₂H₅)₄. The synthetic reactions of the complex alkoxide were carried out in octanol for 2-72h at 70°C, and the successive hydrolysis and condensation reactions were performed at water concentrations of 0.1-2.3mol/dm³ at an ambient temperature in octanol-butanol solvents containing acetonitrile as a cosolvent. Size distributions of the lead titanate particles formed were measured with dynamic light-scattering. Selection of reaction conditions enabled the synthesis of spherical particles with average diameters less than 100nm in ranges of water concentrations of 0.5-2.0mol/dm³ and acetonitrile concentrations of 15-20 vol% at a total monomer concentration of 0.05mol/dm³. The particles were subjected to heat treatment at various temperatures. The particles started to crystallize into a tetragonally perovskite structure at 200°C, and transformed into a single phase at 750°C. Dielectric constants of the particles heat-treated at 500-750°C were close to that of bulk, whereas the crystallite sizes in the particles were similar to the sizes of the particles produced in the reactions.

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Transparent gels were obtained from concentrated polyhydroxoaluminum solutions having different [OH/Al] ratios of 2.00-2.53. These gels were transformed into activated alumina and α-alumina by heating at 500-900°C and above 1000°C, respectively. Activated alumina thus obtained consisted of γ-alumina as the main phase and χ-alumina as the sub-phase: the content of γ-phase increased with increasing [OH/Al] ratio. Activated alumina exhibited two kinds of pores, i.e., smaller pores of 3-4nm and larger pores of 4-30nm in diameter. The amount of the smaller pores increased with increasing [OH/Al] ratio. The diameter of the smaller pores was almost unchanged with increasing [OH/Al] ratio and heat-treatment temperature while that of the larger pores changed: The diameter of the larger pores decreased with increasing [OH/Al] ratio but it increased with increasing heat-treatment temperature. The formation of the smaller pores probably originates from lamellar polymers of polyhydroxoaluminum ions, which have loosely oriented stacking sequence in the gel structure since XRD patterns of the gels having the higher [OH/Al] ratios showed broad reflections of long spacings. Generally, the surface area of the activated alumina increased with increasing [OH/Al] ratio while the pore volume decreased. These dependencies on the [OH/Al] ratio can be explained by changes in pore size distributions for the activated aluminas formed.

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Polycrystalline cerium oxide was prepared by sintering and used for oxygen diffusion experiments by the gas phase analysis. Lattice constant measurements confirmed the stoichiometric condition of the sample. Although Si was contained in the specimens as an impurity, it was considered that point defects were not created by Si, because both Si and Ce have the same valence. The oxygen diffusion coefficient obtained in the present work could be represented by the equation: D_oxy=0.364exp(-322kJ⋅mol^-1/RT)m²⋅s^-1. This result is similar to the oxygen self-diffusion coefficients in other stoichiometric oxides with fluorite structure. This agreement with literature values was considered to be a confirmation that the diffusion coefficient obtained in this work is actually that of oxygen in a stoichiometric CeO₂ lattice.

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Elastic and viscoelastic shear strains induced in test specimens with double-shear geometry are measured by extending the conventional uniaxial speckle extensometry. The test results for soda-lime glass give excellent agreements with the shear modulus G at room temperature and the shear viscosity η reported in the literature at temperatures from 530 to 555°C. The G and η values are also in agreement with those measured by a strain-gage foil and by an electro-optical extensometer, respectively. This agreement confirms that the proposed technique and analysis for the measurement of shear strain with a uniaxial laser speckle strain meter are not only applicable for characterizing the mechanical properties of brittle materials in a small scale deformation, but also provide a powerful tool for studying the high-temperature deformation and flow of engineering materials in a large scale deformation. The issue of affine transformation of polycrystalline materials with local heterogeneity and anisotropy is also discussed by comparing the test results of speckle and electro-optical extensometries.

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In the analysis of oxygen and nitrogen in raw ceramic powders by the inert gas fusion method, differences in the sampling procedure carried out by separate individuals is thought to be a primary factor in the reproducibility. We introduced a press machine for sealing nickel capsules in the sample molding process and confirmed that it was effective in decreasing these differences. Sample molding using a press machine requires pressures above 14.7kPa. As a result of the helium purging test, it was clarified that some pressed 0.5g capsules gave high blank values for residual air inside pressed capsules.

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Thick titania films were prepared by the modified electrophoretic sol-gel deposition method. The titania particles prepared by the sol-gel method were hydrothermally treated at 250°C under 5MPa and then calcined at 600°C in air. The particles crystallized by the hydrothermal treatment showed no aggregation during the calcination and were easily re-dispersed in a mixture of ethanol and water to form stable titania sol. Thick titania films of ca. 20μm in thickness were obtained on stainless steel sheets by electrophoretic deposition of the sol.

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CuCl microcrystals-doped SiO₂ glass thin films were successfully prepared by rf (radio frequency)-sputtering method. The formation of CuCl microcrystals in the glass thin films has been explored by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The quantum size effect in CuCl was found from the blue shift of exciton absortion peaks. Although some influence of the matrix on the temperature dependent linewidth of the exciton peaks was observed, the relationship between the amount of blue shift of the absorption edge and the diameter of the CuCl microcrystals satisfied the theory for the quantum-size confinement of the exciton.

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Superplastic elongation of β-SiAlON was investigated in tensile deformation condition. The test was conducted under 0.1MPa nitrogen atmosphere at 1580°C, and under a constant crosshead speed of 0.078mm/min (the initial strain rate was 1.3×10^-4s^-1). The β-SiAlON exhibited 470% superplastic elongation, and this value was the largest in Superplasticity of silicon nitride based ceramics reported previously. It was demonstrated that a suitable condition was necessary to achieve larger superplastic elongation.

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