The role of carbon and SiC crystallinities in the oxidation and mechanical property improvement of hybrid nano-fibers

In this study, electrospinning was successfully used to fabricate hybrid Carbon-Silicon Carbide (C-SiC) fibers using polyacrylonitrile (PAN) and silicon (Si) nano-particles as precursors. Silicon-to-carbon precursor ratios and heat treatment were optimized to fabricate hybrid nano-fibers with high oxidation resistance. After heat treatment, the nano-fibers showed two-dimensional ordered carbons and SiC nano-phases formation. As a result, a noticeable improvement in mechanical and thermal properties was achieved. Samples with 90 wt% PAN/10 wt % Si showed about four-time improvements in char yield as compared with 100 wt% PAN. In addition, after heat treatment of the fiber at 1250 degrees C, SiC was formed. The SiC phase played a major role in ordering the carbon phase. The carbon and SiC crystallinities had a great impact on the oxidation and mechanical property improvement of hybrid nanofibers. The determination of crystal size was carried out using X-ray results obtained at different temperatures and holding times. The SiC grain growth was predicted using kinetic model and its exponent was found to be around n = 4 with an activation energy around 35 KJ/mol.K. For such growth, the dominant grain growth mechanism was grain boundary diffusion.