Nanosized Hf6Ta2O17 particles reinforced HfC ceramic coating for high temperature applications.

There is an urgent need for the thermal protection of carbon/carbon composites to increase their service span in aerospace field. As members of ultra-high temperature ceramics, HfC and ZrC are thought to be alternative materials, but their poor oxidation behavior and fracture toughness at temperature over 2000 ℃ prevent them from taking full advantages. Herein, we synthesized nanosized Hf 6 Ta 2 O 17 powders and introduced them into HfC ceramic to tackle the above problems. Plasma-sprayed HfC coatings with Hf 6 Ta 2 O 17 varied from 0 to 15 mol.% (0, 1.25, 2.5, 5, 15) were exposed to an oxyacetylene torch with a heat flux of 2.38 MW/m2. The one with 2.5 mol.% Hf 6 Ta 2 O 17 showed the best ablation resistance. Smaller doping was unable to effectively hinder oxygen diffusion given the inadequate compactness of the formed scale, conversely substantial humps and ruptures formed on the samples with higher amounts, acting as straightforward paths for oxygen. • Nanosized Hf 6 Ta 2 O 17 powders were synthesized using sol-gel method. • HfC coatings with various Hf 6 Ta 2 O 17 amounts were fabricated on carbon/carbon composites by plasma spraying. • The sample containing 2.5 mol.% Hf 6 Ta 2 O 17 was supposed as the one with the best ablation resistance. • The ablation mechanisms of the samples were proposed based on the microstructure changes. [ABSTRACT FROM AUTHOR]