A sol-gel strategy of constructing nanosized Hf₆Ta₂O₁₇ encapsulated graphite flakes and its enhancement on the ablation property of carbon/carbon composites

Herein, nanosized Hf₆Ta₂O₁₇ encapsulated graphite flakes were firstly constructed using the sol-gel method, then deposited on the surface of carbon/carbon (C/C) composites by plasma spraying technique to prolong their service span in critical environments. Nanoindentation results affirmed the active influence of graphite flakes on elevating the toughness of the Hf₆Ta₂O₁₇ coating. Besides, after being exposed to the oxyacetylene torch with a peak temperature of about 2000 °C, the sample achieved near zero ablation (0.06 mg/s), meanwhile its porosity and mass ablation rate showed 39.5 % and 60.0 % reduction when compared to pure Hf₆Ta₂O₁₇ sample. During exposure, the external Hf₆Ta₂O₁₇ served as an oxygen barrier for internal graphite flakes, inversely internal graphite flakes provided a “pinning” effect on external Hf₆Ta₂O₁₇, which accounted for its exceptional ablation performance. This work offers a new insight into the design of surface modification of C/C composites and other high-temperature structural materials. 

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