The effect of carbon source addition order during sol-gel process on the properties of C/C–ZrC–SiC composites

Abstract Sol-gel is a promising technology to prepare the C/C–ZrC–SiC composites. However, carbon fiber erosion caused by carbothermal reduction severely degrades properties of the composites. At present study, the addition order of carbon source during sol-gel process was optimized to improve the microstructure, mechanical property and ablation resistance of the composites. Results show that adding phenolic resin before gelation combined with deposited pyrocarbon interlayer around the carbon fibers can greatly alleviate the degradation of the C/C–ZrC–SiC composites by reducing the carbon fiber erosion. The composites thus prepared delivered the flexural strength, mass and linear ablation rates are 162.58 MPa, 0.147 mg/(cm2⋅s) and 0.0098 mm/s, respectively, which are 449% higher, 9.26% lower and 38.36% lower than those of the counterpart that added phenolic resin after gelation. The excellent performance is attributed to little erosion of the carbon fibers and the dense matrix of ZrC–SiC ceramics obtained from adding carbon source before gelation during the sol-gel process.