Effect of mullite content on microstructure and ablation behavior of mullite modified C/C-SiC-HfC composites

Mullite modified C/C-SiC-HfC composites were prepared via precursor infiltration and pyrolysis (PIP). The effects of mullite modification with different contents on the composition, microstructure, and ablation behavior of the composites were investigated. Results showed that inadequate and excessive mullite limited the improvement of the ablation resistance. At 8.88 wt% mullite, the composites exhibited relatively good ablation resistance with mass and linear ablation rates of 0.44 mg/s & BULL;cm2 and 6.39 & mu;m/s. The addition of moderate mullite content promoted the formation of a dense Hf-Si-O multiphase oxide layer on the ablated surface without causing an excessive increase in surface temperature.