Abstract: Carbon/carbon (C/C) composites are one of the most important high temperature structure materials; Which are oxidized remarkably above 400℃ in oxidative atmosphere. In order to improve the oxidation resistance of C/C composites, suspension mixtures prepared by mixing B₄C, SiC and Al₂O₃ powders and phosphoric acid solution were used as precursors to modify the C/C composites by a novel hydrothermal treatment. The influences of the hydrothermal treatment temperature on the phase, microstructure and antioxidation property of the as-modified composites were investigated. The asmodified C/C composites were characterized by X-ray diffraction, scanning electron microscope (SEM), energy dispersive spectroscope (PDS) and X-ray photoelectron spectroscopy (XPS) techniques. Results show that the surface of the C/C composites is covered by a coating composed of molten B₂O₃, HPO₃ and microcrystalline Al(PO₃)₃ after modified by the hydrothermal treatment, and their oxidation resistance is effectively improved in the temperature range from 120℃ to 200℃. The anti-oxidation property of the treated C/C composites is improved with increasing hydrothermal treatment temperature. The mass of the modified C/C composites losses only 2.31% after oxidized at 700℃ in air for 10h.

Key words: carbon/carbon composites, oxidation, hydrothermal, matrix modification