Abstract
Polycarbosilane fibers were irradiated with electron beam in a stream of He gas and the crosslinking between polycarbosilane molecules proceeded with doses, and then the polycarbosilane fibers were cured. The cured polycarbosilane fibers were heat-treated at temperatures of 1200, 1400 and 1500°C and then SiC(E) fibers were prepared. Their tensile strengths were 2.90, 19.2 and 1.49 GPa, respectively. For comparison, thermal oxidation-cured polycarbosilane fibers were heat-treated at temperatures of 1200, 1400 and 1500°C and then SiC(O) fibers were prepared. Their tensile strengths were 2.61, 0.68 GPa and almost null, respectively. The tensile strengths of SiC(O) fibers dropped quickly with the heat treatment temperatures, and those of SiC(E) fibers decreased gradually. On the other hand, electron irradiation-cured polycarbosilane fibers were heat-treated in a stream of NH3 gas and then Si3N4 fibers were prepared. Their fibers were colorless and semi-transparent for visible light. The electron irradiation curing process is considered to be promising in order to prepare SiC fibers with high strength at higher temperature or to prepare new Si3N4 fibers.
