Effect of polycarbosilane content on microstructures and mechanical properties of short-carbon-fibre-reinforced SiC composites

Short-carbon-fibre-reinforced SiC composites were prepared by precursor pyrolysis-hot pressing with Polycarbosilane (PCS) as precursor polymer and MgO-Al2O3-Y2O3 as sintering additives. The effects of PCS content on microstructures and mechanical properties of the composites were investigated. The results showed that, the composites could be densified at a relatively low temperature of 1800 degrees C via the liquid-phase-sintering mechanism and the highest mechanical property was obtained for the composites with 20 wt.% PCS content. During sintering, Y2O3, Al2O3 reacted with the pyrolysis products from PCS and formed amorphous interphase, which was benefit of densification of the composites and avoidance of degeneration of the carbon fibres. The nano PCS-derived SiC almost tied on the surface of the particle of starting powder beta-SiC, which could play a role of filling up the void and improve the relative density of the composites.