SiC polycrystalline fibre and its fibre-bonded ceramic

Abstract

A type of SiC polycrystalline fibre (SA fibre) obtained by sintering an amorphous Si-Al-C-O fibre precursor at 1900 ° C in Argon atmosphere is described. A sintered SiC fibre-bonded ceramic (SA-Tyrannohex), which was synthesized by hot-pressing piled sheets of the amorphous Si-Al-C-O fibre precursor prepared from an organosilicon polymer, is also introduced. The former, SA fibre, which contains a very small amount of aluminium, has a high tensile strength and modulus, and shows no degradation of strength or change in composition on heating up to 2000 °C in inert atmosphere and up to 1000 °C in air for a time longer than 2000 hours. Moreover, SA fibre shows better high-temperature creep resistance in air at 1300 °C than commercial counterparts. We also found that the mechanical properties of the fibre were markedly improved by a decrease in the fibre diameter. On the other hand, the latter, SA-Tyrannohex, consists of a highly ordered, close-packed structures of very fine hexagonal columnar fibres with a thin interfacial carbon layer. The interior of the fibre element was composed of sintered SiC crystals. This material shows high strength, fibrous fracture behaviour, excellent high-temperature properties, and high thermal conductivity (even at temperatures over 1000 °C). It was also found that the initial strength of the SA-Tyrannohex, which was prepared from thinner starting fibre, was perfectly preserved up to 1700 °C in air.