Continuous SiC-based model monofilaments with a low free carbon content. Part II : From the pyrolysis of a novel copolymer precursor

Quasi stoichiometric model SiC monofilaments (C/Si atomic ratio ≈ 1.02) with still some free carbon (≈3 mol%) and residual oxygen have been produced from a novel copolymer precursor, itself prepared from methylphenyldichlorosilane and 2,4-dichloro-2,4-disilapentane. The continuous green fibre was melt spun at 230°C, cured by electron-beam irradiation, and pyrolysed under argon at temperatures, Tp, in the range 1000–1600°C. The fibre remained nanocrystalline at high temperature with the SiC grain size growing from 1.5 nm to 7.3 nm when Tp was raised from 1400°C to 1600°C. Its Young's modulus continuously increased as Tp was raised (with E=320 GPa for Tp=1400°C), whereas its tensile strength at room temperature underwent a maximum for Tp=1200°C (σR≈1850 MPa for L=10 mm and d≈20 μm).