Morphology and microstructure of 2.5 dimension C/SiC composites ablated by oxyacetylene torch

SiC ceramic matrix composites reinforced by 2.5 dimension carbon fibers were prepared by low-pressure chemical vapor infiltration. The ablation performance of the composites was characterized by an oxyacetylene torch. The morphology and microstructure of the as-ablated composite were examined by scanning electron microscopy. The composition of the new phase was confirmed by energy dispersive spectroscopy and X-ray diffraction. Three clear annular regions appeared on the surface of the as-ablated sample and each region had different ablation mechanism. Sublimation was the main ablation behavior in the centre region. Oxidation was the main ablation behavior in the middle region. Silica particles mainly resulted from the oxidation and deposition of Si and SiO gas from the centre to the outer region. The ablation mechanism of the C/SiC composites under oxyacetylene flame was a combined effect of thermo-physicals attack and thermo-chemicals ablation.