The reaction process of polycarbosilane (PCS) fiber cured by cyclohexene vapor has been studied and compared with that of PCS fiber cured by air. The influence of curing temperature on SiÀ ÀH bond reaction degree and gel content, the structure and composition of PCS were investigated by FTIR, EA, TGA, NMR, and GC-MS. The results showed that, SiÀ ÀH bond in the molecular structure of PCS reacted during cyclohexene curing process and the reaction degree increased when the curing temperature increases. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. SiÀ ÀH radical and SiÀ ÀCH 2 radicals formed SiÀ ÀCH 2 À ÀSi crosslinking of PCS molecules through the agency of cyclohexene. Some cyclohexyls linked to principal chain of PCS, which was proven by 13 C-CPMAS-NMR, and broke off, and cyclohexane and some monosilane are generated as byproducts when temperature increased.

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A new SiC fiber was prepared by the pyrolysis of polycarbosilane (PCS) fiber cured with unsaturated hydrocarbons. The fiber, with oxygen content of 4-6 wt%, offers high tensile strength of 2.5-2.8 GPa. The electrical resistivity of the fiber is only about 0.5 Ω·cm, much lower than general SiC fiber obtained from traditional air curing process. Degradation of mechanical property in argon and air at high temperature is retarded by 200-300°C with respect to the Nicalon NL-202 fiber. The low electrical resistivity of the fiber exhibits excellent thermal stability, it almost remains 0.4-0.8 Ω·cm after thermal exposure test from the room temperature to 1600°C in argon. The low electrical resistivity mainly attribute to an excess carbon layer which is about 50 nm in the circular outer part. polycarbonsilane, SiC fiber, electrical resistivity, excess carbon layer Citation:Wang D Y, Mao X H, Song Y C, et al. SiC fiber with low electrical resistivity and oxygen content.

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A new SiC fiber was prepared by the pyrolysis of polycarbosilane (PCS) fiber cured with unsaturated hydrocarbons. The fiber with oxygen content of 4wt%-6wt%, has high tensile strength of 2.5-2.8GPa. The specific resistance of the fiber is only about 0.5¦¸¡¤cm, which is much lower than general SiC fiber obtained from traditional air curing process. Results show that the fiber has an excess carbon layer with a thickness of about 50nm in the circular outer part, and the layer changes little after thermal exposure in argon. Compared with the ceramic grade fiber Nicalon NL202, thermal resistance to degradation of the fiber¡¯s mechanical property is improved by 200-300¡䬠The low specific resistance of the fiber also exhibits excellent thermal stability, which almost remains at 0.4-0.8¦¸¡¤cm after thermal exposure test from the room temperature to 1600¡䟩n argon.