Effect of SiC Nanowires on the Mechanical and Oxidation Protective Ability of SiC Coating for C/C Composites

摘要

To protect carbon/carbon (C/C) composites against oxidation, a SiC nanowire-toughened SiC coating with homogeneously dispersed nanowires within the coating was successfully prepared on C/C composites by a simple and low cost two-step technique of chemical vapor deposition and pack cementation. The SiC nanowires effectively increased the mechanical properties of the coating, decreased the size of the defects in the coating, and improved the oxidation protection effectiveness of the coating. The results showed that, after introducing the SiC nanowires, the hardness, elastic modulus, and fracture toughness of the SiC coating were increased by 5%, 19%, and 48%, respectively. The mass loss of the coated C/C samples was reduced from 8.10% to 5.21% after thermogravimetric analysis in air from 873 to 1773 K. Moreover, the mass loss of the SiC nanowire-toughened SiC coated sample was only 14.33% and 2.68% after isothermal oxidation at 1173 K for 39 h and 1773 K for 44 h in air, whereas the mass loss of the pure SiC coated sample was up to 16.12% and 7.00% after isothermal oxidation at 1173 K for 15 h and 1773 K for 20 h in air.