Enhancement of the oxidation resistance of interfacial area in C/C composites. Part I: oxidation resistance of B–C, Si–B–C and Si–C coated carbon fibres

Carbon fibre preforms were coated with B–C, Si–B–C and Si–C deposits obtained by chemical vapour deposition in order to limit their oxidation rate. B–C and B-rich Si–B–C coatings oxidize rapidly and lead to the formation of a glassy film that protect carbon fibres from oxidation. Oxidation occurs by oxygen diffusion through this glassy film. Si–C and Si-rich Si–B–C deposits oxidize slowly and protect efficiently carbon fibre from oxidation. Oxygen accesses to the carbon fibre surface only occurs through cracks of the deposit. Thin deposits (≈30 nm) are less efficient than thicker deposits because the oxygen can progress between SiC crystallites. Deposits thicker than 100 nm efficiently protect carbon fibres from oxidation.