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Porous carbon/carbon composites were infiltrated by mixed Si-Mo-Ti powder with different Ti content below 1600℃ to produce an ablative C f /C-(Mo,Ti)Si 2-SiC composite. Microstructure， mechanical properties and ablation properties of the infiltrated composites were investigated. Results show that composites infiltrated by mixed powders with 14%wt Ti content have dense gradient structure and good mechanical properties. Three different kinds of typical morphologies can be distinguished on the surface of infiltrated composites according to the distribution of MoSiTi solid solutions. Formation mechanisms of the three kinds of typical morphologies are also analyzed. Ablation resistance improvement is attributed to the dense and continuity ceramic phases which distribute from inside to surface of the composites. Composites infiltrated with 14%wt Ti have the best ablation resistance due to the protective oxide layer formed by type I and type III morphologies during the ablation process. Linear and mass ablation rates of such composites are 0.002mm/s and 0.01mg/s, respectively.

To improve anti-ablation property of C/C-ZrC-SiC composite, a novel design of Al-Cr alloy surface sealing was performed by liquid melt impregnation. Results show that Al 8 Cr 5 formed on the surface which could effectively seal the holes and cracks. The cooperation of metal and ceramics contribute a better anti-ablation performance to the obtained composite, and its mass and linear ablation rates decrease by 98.3% and 81.2% respectively. This special surface structure evolves into a highly dense oxide scale comprising various solid solutions(including Al-Cr-O, Al-Si-O, Cr-Si-O) and ZrO 2 , which could significantly improve the anti-ablation performance of C/C-ZrC-SiC composite.

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