Debonding at the fiber/matrix interface and subsequent frictional sliding considerably affect the fracture toughness of fiber-reinforced ceramic composites. In this study, the interfacial shear properties of a Si-Ti-C-O fiber-bonded composite were investigated both at room temperature and at elevated temperatures. A jig suitable for punch-out experiments was newly designed for this purpose. Punch-out experiments were performed at room temperature, 700 and 1400°C for various exposure times. It was found that the interfacial shear properties significantly depended on the oxidation behavior of the Si-Ti-C-O fiber-bonded material. At 700°C, a turbostratic carbon layer at the fiber/matrix interface is prone to oxidation, which weakens the interfacial shear properties in a catastrophic manner. At 1400°C, the quick formation of a silica layer protects the carbon from oxidation, resulting in an enhanced interfacial shear strength.

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New porcelain bodies, which exhibit lightweight and relatively high-strength, were fabricated using only nonplastic raw materials, such as glass microspheres, quartz and aluminous cement. Their mechanical properties were investigated. While the α-quartz and CaAl₄O₇ phases did not change with hydration time in the green body, the CaAl₂O₄ phase diminished and, finally, disappeared after 24h hydration. A new phase, CaAl₂ Si₂O₈. 4H₂O formed but only at hydration times between 24 and 48h, which exhibits maximum green strength. Green strength decreased slightly with increasing the content of glass microspheres at a constant aluminous cement content of 20mass%. This decrease of green strength is attributed to the decreased bulk density and the relative decrease of aluminous cement volume, due to the larger volume of glass microspheres. The phases formed in the fired body were α-quartz, α-cristobalite, anorthite, glass and a small amount of α-Al₂O₃. The addition of larger amount of glass microspheres (60mass%) led to large pores in the fired body, due to low viscosity of glassy phase during the firing process. However, the addition of a small amount of glass microspheres, such as 20mass%, hampered vitrification and sintering in the fired body. The increased flexural strength at an intermediate composition containing 40mass% glass microspheres was attributed to a strong prestress induced by the mismatch in thermal expansion coefficient between the glass matrix and the α-quartz grains during the cooling process. Fewer fracture origins, a smaller water absorption and a higher density due to the appropriate vitrification process were also indicated as potential factors leading to the strengthening effect.

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BaTiO₃ semiconducting ceramics were fired according to a reduction-reoxidation method, and a fraction of the Ba ions were complexly substituted with both Ca and (Sr_0.5Pb_0.5). The effects of the complex substitution on the microstructure and electrical properties were experimentally investigated. The optimum fraction of the complex substitution was fixed from the viewpoints of small grain size, small resistivity at room temperature and large magnitude of resistivity jump above the Curie point. Using the optimum composition, a prototype multilayer sample with iridium foils as the internal electrodes was fabricated by reduction-reoxidation firing, and evaluated focusing on the formation of the internal electrodes and the electrical properties.

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A suitable relationship between oxide ion polarizability, cation polarizability, optical basicity and O1s binding energy in XPS spectra has been searched on the basis of experimental and calculated data reported in the literature for numerous simple oxides. It has been established that O1s binding energy decreases with increasing oxide ion polarizability, cation polarizability and optical basicity. The observed O1s chemical shift to lower binding energy from 533.5eV to 528.2eV could be explained with an increase in electron charge density of the oxide ions, due to an increase in their electronic polarizability. Increased oxide ion polarizability means stronger electron donor ability of the oxide ions and vice versa. That is why O1s binding energy can be used for the construction of common basicity scale of different amorphous and crystalline materials. On this basis the simple oxides have been separated into three groups according to the values of their oxide ion polarizability, optical basicity and O1s binding energy.

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Thermal decomposition of barium titanyl oxalate tetrahydrate was investigated in air and nitrogen atmospheres, respectively. Decomposition process is divided into four steps; dehydration, decomposion, crystallization and the production of BaTiO₃. In air atmosphere, after dehydration and the decomposition of barium titanyl oxalate, a small amount of BaCO₃ and TiO₂ is formed through the reaction between the decomposition product and the generated CO₂ gas in air atmosphere, while the other large part of the decomposition product crystallizes out as intermediate phase (Ba₂Ti₂O₅CO₃) in intermediate process of decomposition. In nitrogen atmosphere, however, BaTiO₃ is only formed through decomposition of intermediate phase.

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In order to make a quantitative evaluation of stress-enhanced corrosion on glass surface in aqueous solutions, an indentation method was adopted. Using this technique, the stress corrosion limit, K_SCC, was measured in three different glasses, a soda-lime silicate glass and two kinds of alumino-silicate glasses. Influence of a surface active agent on the stress corrosion limit of soda-lime silicate glass was also estimated using soda kaplinate acid solution. The present results can be summarized as follows: (1) The indentation method can be generally used provided that a median/radial crack can be introduced on the glass surface, and it enables to distinguish subtle differences in the extent of the corrosion process. (2) Accurate K_SCC data can be obtained within a 3% standard deviation. (3) By the indentation method the K_SCC can be estimated in small specimens or at localized parts.

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Crack growth measurement was performed in order to study the effect of pH of solution and the amount/nature of dissolved metal ions on stress-enhanced corrosion of glass. The testing conditions were systematically changed from the viewpoint of surface chemistry. The data of stress corrosion limit, K_SCC, can be described in terms of pH of solution. The presence of metal ions dissolved in the solution at a specific pH suppressed the stress-enhanced corrosion. At this specific pH metal ions react with the glass surface. It was also found that the same effect was promoted at a constant pH when the concentration of metal ion increased. These results demonstrate that, although a complicated relation exists between concentration and nature of dissolved metal ions, crack growth data can be rationalized by taking the pH of solution as the parameter having the predominant effect.

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More than 60mol% Zr⁴⁺ ion (ZrO₂/(Al₂O₃+ZrO₂)) is soluble into anhydrous Al₂(SO₄)₃ crystal lattice. The apparent crystallite size decreases with increasing Zr⁴⁺ content, and the thermal decomposition temperature reduces at contents of zirconia >20mol%. Alumina/zirconia composite powders, in which an amorphous zirconia phase is dispersed in a matrix of fine η-alumina particles, are obtained by thermal decomposition of the sulfate solid solution. Tetragonal phase of zirconia crystallizes at 1100°C and the crystallinity increases with increasing the temperature of the heat-treatment. When mono-dispersed ultra fine particles of zirconia are added to η-alumina formed by thermal decomposition of pure anhydrous aluminum sulfate, the η→α phase transformation of alumina is suppressed, and the effect increases with increasing the amount of the additive. On the contrary, a small quantity of ZrO₂<1mol% drastically suppresses the phase transformation of alumina formed by decomposition of sulfate solid solution. But, when ZrO₂ content is more than 1mol%, the η→α phase transformation of alumina is accelerated. The acceleration effect becomes larger with increasing the content of ZrO₂.

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Nanocrystalline anatase suspensions with various formative ratio of anatase (A_f in mass%) were synthesized through hydrolysis and hydrothermal treatment of titanium tetraisopropoxide, and were used for preparation of coating films. Films were dip-coated on glass plates with a withdrawal speed of 50cm/min, followed by heating at 500°C for 1h. Crack-free and transparent TiO₂ films could be prepared from the suspensions with about 85% A_f. However below about 85% A_f, cracks and island texture were observed in the films. It was found that the area shrinkage of films proportionally decreases with increasing A_f. The critical thickness for obtaining crack-free films from the suspension of about 100% A_f was approximately 1μm and porosity of the film was about 55%. The high photocatalytic activity of the prepared films was demonstrated from oxidation and removal of NO under UV irradiation.

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Plasticity and packing structure of clay and alumina dough, and of alumina mixed with water-soluble and non-water-soluble plasticizers were investigated. It was found that both plastic clay dough and alumina dough with plasticizers showed a two-peak pore population. When the larger-sized pores increased in volume, the fluidity of the dough was improved. On the otherhand, when the smaller-sized pores decreased in volume, a high rigidity was showed. An aggregate structure was observed in the clay and the dough mixed with water-soluble plasticizer like methyl cellulose. Plasticity was generated when the aggregates were deformed by using the larger-sized pores among each aggregate. The non-water-soluble curdlan did not dissolve in the dough and remained in gel. The larger-sized pores were formed by the gel, whose deformation produced plasticity. It was understood that plasticity is generated when either the aggregates or the gel act as a buffer in the dough and enhance deformation of the dough.

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Ultrafine silver monodispersed particle were prepared by wet chemical process. To decrease the reduction speed, an important factor in generating monodispersed particles is to control the following three factors: synthesis temperature, concentration of aggregation-relaxing agent added, and concentration of silver nitrate solution. Synthesis of monodispersed spherical Ag particles, used as metal powders for electrode, became possible using the nucleus growth reaction method. This process also allowed the control of the diameter of the powder particles. The silver particles were distributed in a narrow particle diameter range with on average of 0.5μm. Transmission electron microscopy (TEM) revealed that single-crystalline silver particles were prepared by the present method.

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Non-destructive evaluations of initial damage and damage mechanism were conducted in plasma sprayed coating, ZrO₂-8 mass%Y₂O₃/NiCoCrAlY onto stainless steel by atmosphere plasma sprayed method by thermal acoustic emission (AE) method and ultrasonic C-scope. The materials was subjected to thermal shock cycle. Initial damage generation occurred on colony pores at the ceramic/bond layer interface, where delamination was generated by the coalescence of initial thermal stress damages following damage nucleation. The damage mechanism was cracking of the ceramic layers by thermal tensile stress. AE detected the initial defects and the damage, and damage mechanism in according to an analysis of AE location and amplitude with correspondence to thermal history. Ultrasonic C-scope evaluation provided a high resolution view for damage detection, combining the results of AE location.

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Photodegradations of gaseous isopropyl alcohol over UV irradiated films prepared from peroxo-modified anatase sol (PA sol) were studied. When the amount of the film formed by PA sol was 0.25mg/cm², the film showed high photocatalytic activities, however, the activities for the films of 0.075mg/cm² and 0.15mg/cm² were low significantly. By use of PA sol added with TiO₂ powder (Degussa P25), the pore size in the film increased, the transmittance of the film decreased over the visible and UV region, and their photocatalytic activities were improved remarkably. In case of coating of 0.075mg/cm², the film prepared from PA sol adding 20mass% of TiO₂ powder showed about twentyfold photocatalytic activities compared with a film without TiO₂ powder. Maximum photocatalytic activity was achieved by use of the sample containing 60mass% of TiO2₂ powder.

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In relation to the joining of aluminium nitride ceramics to metal, the reaction products and the reaction mechanism between AlN and Ni have been investigated under a nitrogen or an argon atmosphere at temperatures of 1273-1673K. Using AlN-Ni powder mixtures, reaction rates were determined by thermogravimetric analysis and the reaction products were examined by X-ray diffraction. The reaction between AlN and Ni occurred above 1250K under both N₂ and Ar atmosphere. Under N₂ atmosphere, the reaction product was only a Ni-Al solid solution. Under Ar atmosphere, at higher temperatures and on prolonged heating, the reaction product was changed in the following order: Ni-Al solid solution, Ni-Al (s.s.)+Ni₃Al, Ni₃Al, Ni₃Al+NiAl and finally NiAl. The initial rates of the reaction obeyed a linear rate law. Under both N₂ and Ar atmosphere, the rate constants and the activation energies (224 and 210kJ/mol) showed comparable values. The reaction rate is thought to be controlled by a chemical process, such as the dissociation of AlN. When the Ni particles were covered with a reaciton layer, the rate obeyed a parabolic rate law. The rate constant under N₂ atmosphere was 2 orders of magnitude lower than that under Ar atmosphere. In the range of stability of Ni-Al(s. s.), the activation energy under N₂ atmosphere (124kJ/mol) was almost identical to that under Ar atmosphere (127kJ/mol). Under Ar atmosphere, the activation energy for Ni₃Al formation was 342kJ/mol. The kinetics are probably determined by solid-state diffusion through the reaction layer.

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Si-Ti-C-O-fiber/SiO₂-glass composite was prepared by oxidation of the fibers at ambient temperature and subsequent hot-pressing at 1750°C (50-70MPa). The matrix was built by a silica layer on the fiber surfaces formed during initial oxidation. High-resolution transmission electron microscopy (HRTEM) revealed the in-situ formation of a graphitic interface with both turbostratic and cellular configuration in addition to TiC crystallites, also precipitated within the silica matrix. Thermodynamic considerations indicate the possibility of active oxidation of SiC in the Tyranno fiber yielding gaseous silicon monoxide and solid carbon.

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Hydroxyapatite whisker and platelet were synthesised by the hydrolysis of alpha-tricalcium phoshate (α-TCP) in H₂O system and etanol/H₂O system at 70°C and atmospheric pressure, thus avoiding severe processing condition, such as in hydrothermal synthesis. The hydroxyapatite prepared by this process was analysed by X-ray diffractometry and transmission electron microscopy observation. The effect of ethanol addition into H₂O on the hydrolysis of α-TCP to hydroxyapatite was also examined. The hydrolysis rate of α-TCP to hydroxyapatite was inhibited in the ethanol/H₂O system. It was found that the morphology and the aspect ratio of hydroxyapatite could be controlled by adding ethanol into H₂O during the hydrolysis reaction of α-TCP.

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Hot-isostatic-pressed (HIP'd) tetragonal zirconia ceramic containing 3mol% Y₂O₃ was soaked in hot water at 95-100°C to evaluate the transformation rate from the tetragonal (T) to the monoclinic (M) phase. The transformation rate differed considerably between the polished surface and the surface cut by a diamond wheel. After about 1000h of soaking in hot water, the volume of the M-phase was 50% in the cut surface and less than 20% in the polished surface. Tetragonal ZrO₂ with polished and cut surfaces were annealed at 1000°C for 2h in air. When the annealed specimens were soaked in hot water, the transformation rate in the cut surface was the same as that before annealing; on the other hand, the M-phase volume in the polished surface increased to 70% after 1000h of soaking. Surface roughness, a rhombohedral phase generated by cutting or machining and orientation of the T-phase crystal due to machining, are thought to be causes of the transformation rate change. However, not one of them on its own could explain all the phenomena without contradiction.

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