Au microcrystals embedded in glass have a high potential use as nonlinear optical materials. In order to increase the content of Au in glass, sol-gel method was applied. Using tetraethoxysilane and sodium tetrachloroaurate as starting materials, Au-doped silica glass films were deposited on silica substrates by dip-coating method. Average radius of Au microcrystals in the glass films is 40Å. Heat treatment of this film at 900° or 1000°C shifted the absorption peak around 530nm to the shorter wavelength and changed the bandwidth of this peak broader, which indicates the decrease in crystal radius.

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A new method of apatite coating on yttria partially stabilized zirconia plate was studied. Firstly, calcium metaphosphate was heated and fused onto 3mol% yttria partially stabilized zirconia plate to form an interlayer. Then a mixture of calcium metaphosphate and tetracalcium phosphate was applied on the zirconia plate, followed by heating in the presence of water vapor. Apatite and tricalcium phosphate formed on the surface of the zirconia plate by heating at 1100°C while calcium pyrophosphate and tricalcium phosphate but apatite formed above 1200°C. The products of the coated layer were discussed in relation to the reaction at the interface between zirconia plate and coated layer.

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Dense Cr₃C₂ ceramic and its composite with 10 and 25wt% TiC were fabricated without additives by the gas-pressure combustion sintering. Their densities reached over 99% of theoretical density and no grain growth occurred because of a rapid sintering. The hardness, flexural strength and fracture toughness, thermal expansion coefficient and thermal conductivity of the Cr₃C₂ ceramics were 18GPa, 625MPa, and 5.6MPa.m^1/2, 10.3×10^-6/K and 0.14W/cmK, respectively. These properties are close to those of sintered one by normal sintering and post-HIPing. However, no further improvement of these properties was observed by forming composites.

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Alumina ceramics containing Y₂O₃ and a small amount of MgO were sintered and their physical properties, such as bulk density, bending strength, and shrinkage, and microstructure were investigated comparing with alumina ceramics containing 3Y-ZrO₂ and a small amount of MgO. The results are as follows: (1) The bending strength of the Al₂O₃-Y₂O₃-MgO sintered composite showed a relatively high value of 330MPa when it contained 10wt% Y₂O₃. (2) In the Al₂O₃-Y₂O₃-MgO sintered composite containing 30 to 60wt% Y₂O₃, a great number of pores were generated. (3) Identification of the Al₂O₃-Y₂O₃-MgO sintered composite by XRD revealed that the composites containing 10 to 30wt% Y₂O₃ were composed of α-Al₂O₃ and 3Y₂O₃⋅5Al₂O₃. It was also clarified that the composite containing 60wt% Y₂O₃ consisted of 3Y₂O₃⋅5Al₂O₃ and 2Y₂O₃⋅Al₂O₃. (4) Comparison of the Al₂O₃-Y₂O₃-MgO sintered composites with the Al₂O₃-Y₂O₃-ZrO₂-MgO ones showed that the latter were more advantageous in high physical properties and fine grained structure than the former.

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Zirconia (3mol% Y₂O₃) composite ceramics reinforced with 10, 20 and 40vol% α-alumina whiskers were prepared by hot-pressing at 1500°C under 30MPa for 30min, and the mechanical properties were measured. The α-alumina whiskers were fabricated by thermal decomposition of aluminum borate (9Al₂O₃⋅2B₂O₃) whiskers at 1500°C for 72h in air. Almost full dense composites (>99%) were obtained by 1500°C hot-pressing. Improvement of room temperature bending strength was observed because of the whiskers. In fracture tests at 1200°C, monolithic zirconia showed plastic deformation and bent, while the composite had a strength of around 300MPa. Elastic modulus and hardness increased linearly with increasing whisker content. As the whisker content increased, fracture toughness also increased due to crack deflection by whiskers and pull-out of whiskers, and showed a maximum value (around 5.4MPa⋅m^1/2) at the whisker content of 40vol%, which was 1.4 times as large as that of monolithic zirconia.

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Si₃N₄/10vol% TiN particulate composites with six TiN particle size distributions (average size: 0.3-13.6μm) were sintered at 1850°C for 4h in 0.9MPa N₂ atmosphere, and Young's modulus, fracture toughness and microstructure of the composites were examined. Although all the composites were densified up to >98% theoretical density, Young's modulus of the composites with larger TiN particles decreased due to the pre-existing microcracks. Fracture toughness of the composites showed a maximum value at the particle size of TiN of about 4μm, which is smaller than the predicted critical size. It is suggested that the presence of the grain-boundary phases in the composite favors the formation of microcracks at smaller TiN particles.

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Interaction between fiber and glass matrix has been observed during crack bridging process in a continuous fiber-reinforced glass matrix composite. The crack growth of the matrix was strongly affected by the presence of the fiber. Crack bowing was clearly recognized when the crack front approached the fiber. Complex stress field caused the rough surface of the matrix crack around the fiber instead of smooth surface as it appears in the general fracture of the glass matrix. The result also indicated a possibility of toughness increase by the crack bowing process.

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Organic dyes of stilbazolium group, such as 4′-dimethylamino-N-methyl-4-stilbazolium iodide (DMSI) and 4′-diethylamino-4-stilbazolium propylsulfate (DESPS) having large third-order nonlinear succeptibility χ⁽³⁾ values, were incorporated into a low melting PbF₂-SnF₂-SnO-P₂O₅ glass system with a conventional melting- and quenching technique. The dyes were mixed with the glass melts around 300°C. From the optical and infrared absorption spectroscopy, it was found that the original structure of each dye was maintained even in the glass. The χ⁽³⁾ of the dye-doped glass was evaluated from third-harmonic generation, and that of the glass containing DESPS was nearly twice as large as that of the base glass.

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