抄録
Silicon nitride whiskers were obtained by the heat treatment of porous bodies at 1373 to 1773K in nitrogen stream, which were produced by polymerization and drying of polymerizable W/O-type emulsions containing polycarbosilane and milled carbon fibers. The whiskers were deposited on the surface and inside of the porous bodies. At 1473K the whiskers were apparently observed as rod-like ones. The tape-like whiskers were observed beside the rod-like ones at 1573K and the tape-like ones were mainly observed at 1673K. Scanning electron microscopic analysis revealed that the rod-like whiskers were formed via the vapor-liquid-solid (VLS) process, and grow in a preferential direction via the vapor-solid (VS) process, resulting in the formation of the tape-like ones. It was found that the whiskers were mainly α-type Si3N4 and that the α-phase content of the whiskers obtained at 1673K was 96.7% by X-ray diffraction analysis. It was proved by infrared spectroscopy and chemical analysis that Si3N4 whiskers grew remarkably with decreasing Si-O bondings. It can therefore be presumed that the formation mechanism of Si3N4 whiskers was analogous to that of the silica-carbothermal reduction-nitridation and that the optimum temperature for the formation of Si3N4 whiskers was around 1673K.
