Composites of Al2O3 and Y2O3 partially‐stabilized ZrO2 were isostatically hot‐pressed using submicrometer powders as the starting material. The addition of Al2O3 resulted in a large increase in bending strength. The average bending strength for a composite containing 20 wt% Al2O3 was 2400 MPa, and its fracture toughness was 17 MN·w−3/2

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The temperature dependence of bending strength, fracture toughness, and Young's modulus of composite materials fabricated in the Zr02(Y203)-A1203 system were examined. The addition of A1203 enhanced the high-temperature strength. ISOstatically hot-pressed, 60 wt% Z r 0 2 (2 mol% Y203)/40 wt% A1203 exhibited an extremely high strength, 1000 MPa, at 1000°C. 20,-PARTrALLY-stabilized ZrO, (YyPSZ) has attracted considerable interest as the new structural material because of its high toughness and high strength.',' These features arc attributed to the stress-induced transformation of the tetragonal phase. However, the strength and toughness of Y-PSZ decrease markedly with incrcasing temperature. A decrease in the strength and fracture toughness at high temperature was also observed for zirconia-toughened ceramics such as Mg-PSZ and AI2O,/ Zr02.,-' According to transformation toughening theory, the low values of hightemperature strength are due to the CONl~KIRUTIN(i EDITOK-w. R. CANNON

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Nitration, amination, chlorination and sulfonation of polycarbonate were studied. 1) Nitrated polycarbonate (NPC) was obtained by reacting with the nitric acid. Amino and diazo-polycarbonate were derived from NPC.2) It was observed that substitution chlorination to the nucleus was carried out by using the catalyst in darkness . 3) Sulfonation of polycarbonate was carried out with chlorosulfonic acid , sulfuric acid and sulfuryl chloride. The polymers were soluble and/or swelled in the water . 4) Nitrobisphenol was obtained by hydrolysis of NPC, and aminobisphenol was prepared * Tokuyama Refinery , Idemitsu Kosan Co. Ltd. (Shingu-cho, Tokuyama, Yamaguchi) from nitrobisphenol. Tetrachlorobisphenoland dichlorobisphenol were isolated from the hydrolysis products of chloropolycarbonate.5) Copolymerization of bisphenol-A and its derivatives were carried out in pyridine and in water-methylene chloride with the use of trimethyl benzyl ammonium chloride as the catalyst.