Fabrication of porous SiC_y (core)/C (shell) fibres using a hybrid precursor of polycarbosilane and pitch

摘要

Porous SiC_y (core)/C (shell) composite fibres have been fabricated using a simple KOH con-trolled-activation of SiC_x fibres, which were pyrolyzed from polycarbosilane-pitch blend fibres. Effects of activation conditions and pyrolysis temperatures were studied. There are distinctive interfaces observed on the cross-sections of the co-axial fibres, where Si content varies gradually from the core to the shell. The etching of Si follows a slow "core-reducing" process in N2, while in CO2, cracks are frequently observed on the shells due to the accelerated activations. V-shaped Si-free carbon fibres could be obtained when a lower pyrolysis temperature was used to produce the SiC_x fibres.