Oxidation Behavior Of C/C Composites With B4c-Sic-Zrc-Zrb2 Coating Prepared By Infiltration And Pyrolysis

Polycarbosilane, B-Si and B-Si-Zr modification coal tar pitch were used as impregnate agent for infiltration and pyrolysis formation of carbon/carbon (abbreviated as C/C) composites with B4C-SiC-ZrC-ZrB2 coating. The density of the composites was examined to be 1.0 g center dot cm(-3), 1.4 g center dot cm(-3) and 1.8 g center dot cm(-3), respectively. The phase compositions, surface morphologies and element distributions of the coating were analyzed by X-ray diffraction (XRD) scanning electron microscopy (SEM) and energy dispervive spectroscopy (EDS), respectively. The result showed that the two composites with a density of 1.4 g center dot cm(-3) and 1.8 g center dot cm(-3) displayed compact microstructures. The oxidation behavior of the composites was studied by oxidation in air at temperatures from 800 to 1,550 degrees C for 1 h. The composites with a density of 1.8 g center dot cm-3 exhibited a lower weight loss of 1.8 % after oxidation. B4C-SiC-ZrC-ZrB2 coating was found to provide the best protection by the precipitated B2O3, SiO2 and ZrO2 on the surface of the composites during the oxidation process, which were characterized by self-healing and antioxidation. The C/C composites with B4C-SiC-ZrC-ZrB2 coating performed well at high temperatures with the formation of complex oxides glass film that prevented oxygen from further spreading into the matrix.