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.

Automated summary

To reduce cost and preparation time, uneven-density C/C composites are designed and prepared using thermal gradient CVI process, followed by local modification of ZrC-SiC composite ceramics to enhance anti-ablation performance. Ablation tests demonstrate that the microstructure of ZrO2 grains can be influenced by adjusting ablation temperature and ZrO2 grains' melting point. Optimum performance is achieved with approximately 20 wt% SiC content in the ZrC-SiC composite ceramics and improves the uneven C/C composites prepared. Additionally, the dense C/C matrix prevents liquid ZrO2-SiO2 phase runoff and allows for protection of carbon fibers and the dense C/C matrix beneath.