Influence of the Content of B_4C on Microstructure and Oxidation Resistance of Carbon/carbon Composites Modified by a Sol-gel/solvothermal Process

摘要

In order to improve the oxidation resistance property of carbon/carbon composites, the C/C matrix was modified with a borate sol precursor and B_4C micro-powders by a sol-gelsolvothermal process. The phase compositions, surface and cross-section microstructures of the C/C matrix modified by different B_4C contents were particularly investigated. Results show that the surface of the modified composites is covered by a coating composed of B_2O_3 and B_4C, meanwhile, the internal micro-holes of the C/C composites are occupied by B_2O_3 and B_4C. After oxidation in air at 973 K, the B_2O_3 glassy phase due to the oxidation of B_4C seals the cracks and holes and effectively prevents C/C composites from oxidation. The weight loss of the modified C/C composites is only 2.21 % after oxidation in air at 973 K for 20 h.