Local Anti-Ablation Modification of Uneven-Density C/C Composites with the ZrC-SiC Composite Ceramics

To lower the cost and preparation period of C/C-ZrC-SiC composites, the uneven-density C/C composites (with a high density in the inner region and low density in the surface region) are designed and prepared by thermal gradient CVI process, followed by local modification of ZrC-SiC composite ceramics by precursor infiltration -pyrolysis (PIP) mothed to improve the anti-ablation performance. The ablation tests show that the SiC con-tents have a great influence on the microstructure of ZrO2 grains at the ablation center by adjusting the ablation temperature and the melting point of ZrO2 grains. Results prove that about 20 wt% SiC is optimum for the ZrC-SiC composite ceramics to perform best during the ablation and modify the uneven C/C composites prepared in this work. Besides, the dense C/C matrix would stop the liquid ZrO2-SiO2 phase from running off, and in return, the dense ZrO2-SiO2 phase would sink into the surface within the ablated region, which could protect the carbon fibers of the surface region and the dense C/C matrix beneath.