RESEARCH-AND-DEVELOPMENT ON CARBON CERAMIC COMPOSITES IN JAPAN

Recent topics related to carbon/ceramic composites in Japan are reviewed. The successful uses of chopped carbon fibers (pitch-based, general-purpose grade) in cladding tile panels for the Al Shaheed monument in Bagdad and in curtain walls of the Ark Hills office building in Tokyo are mentioned. Only a 2 to 4 vol% addition of chopped carbon fibers to the cement mortar makes the mechanical strength two to three times larger and also increases toughness. These composites (CFRC) have a high durability and high dimensional stability in an atmosphere with high temperature and high humidity. By using continuous carbon fibers and thin sheets of carbon fiber mat, fundamental studies on mechanical properties and electrical shielding effects were performed. Cables of carbon fiber-resin composites were used in the prestressed concrete instead of steel wire. Carbon/metal carbide composites are prepared by hot-press sintering of powder mixtures of calcined coke and different carbides such as B4C, and also by a pressureless sintering using raw coke. These composites have much a higher bend strength up to 1700-degrees-C and higher electrical resistivity than conventional carbon materials. The carbon/B4C composites prepared by hot pressing have excellent oxidation resistance in air and also corrosion resistance in molten aluminum. The pressureless-sintered composites of carbon/SiC/B4C have a high oxidation resistance at temperatures as high as 1200-degrees-C in air. Impregnation by borosilicate glass makes the graphite blocks oxidation resistant and gas impermeable.