Rapid Preparation of SiC Fibers Using a Curing Route of Electron Irradiation in a Low Oxygen Concentration Atmosphere

Polycarbosilane (PCS) fiber was irradiated by electron beam at low dose in a flowing N₂/O₂ mixture with O₂ concentration of 1%. After the pyrolysis of the irradiated precursor fibers, SiC fibers with high strength of 2.4 GPa were obtained. Microstructural evolutions of the resultant fibers were explored. It was found that during the irradiation, free radicals were formed in the PCS and were oxidized by oxygen as Si-OH groups. The Si-OH groups then transformed into Si-O-Si linkage and resulted in further cross-linking of the PCS during pyrolysis. A remarkable structure gradient along the fiber diameter was formed under the coupled effects of irradiation and oxidation. The content of oxygen decreased from the fiber surface to the core, whereas the crystallinity of β-SiC increased in the same direction. The electrical resistivity of the as-prepared ceramic fiber was 80.7 Ω cm, showing good potential for being as electromagnetic wave absorber.