New type of SiC-sintered fiber and its composite material

This paper deals with a new type of sintered SiC fiber with excellent heat-resistance and mechanical properties, and a unique composite material composed of only the sintered SiC fiber. We report here that the sintered SiC fiber containing a very small amount of Al showed high-strength, high-modulus, excellent high temperature stability and prominent alkali-resistance. Moreover, the fiber showed excellent creep resistance at very high temperatures compared with well-known SiC-bascd fibers. This sintered SiC fiber was synthesized at a very high temperature (over 2073K) using an amorphous Si-Al-C-O fiber as the starting material. Its high strength over 2 GPa was maintained up to 2273K in Ar atmosphere and very little weight loss (only 1.8wt%) was observed up to 2473K. On the basis of this technology, we have also succeeded in developing a toughened fiber-bonded composite, consisting of perfectly close-packed sintered SiC fibers with a hexagonal transformed cross-section. At the interface between the hexagonal-columnar fibers a very thin interfacial carbon layer uniformly exists to obtain fibrous fracture pattern. The sintered fiber-bonded composite, having very high fiber volume fraction (similar to 100%), showed excellent oxidation resistance up to 1873K in air and perfectly maintained the initial high strength even at that high temperatures.