Microstructure, mechanical and anti-ablation properties of Mg-modified C/C–ZrC–SiC composites prepared by sol-gel technology

Abstract

Mg-modified C/C–ZrC–SiC composites were fabricated by a sol-gel process, and the influences of the Mg/(Zr + Si) molar ratio on the microstructure and the mechanical and anti-ablation properties of the composites were investigated. The results showed that Mg addition not only optimized the distribution of surficial ceramic particles but also improved the flexural strength of composites by inhibiting the ceramization of fibres. Fabricated Mg/(Zr + Si) with a molar ratio of 0.040:0.18 increased the flexural strength of the composite from 173.15 MPa to 331.22 MPa, and the elastic modulus ranged from 11.46 GPa to 23.09 GPa. After plasma flame ablation for 180 s, this composite also showed excellent anti-ablation performance with linear and mass ablation rates of 3.91 μm/s and −0.23 mg/s, respectively. The superior ablation property was ascribed to the formation of a consecutive oxide layer constructed by a viscous mixed liquid consisting of liquid Mg–Si–O and Zr–Si–O phases and the robust skeleton of the coarsening ZrO2.