Tailored Csf/HfC0.76N0.24 composites for superior ablation resistance at 3000°C

Ultra-high temperature materials are desirable to withstand the severe aero-thermochemical environments of hypersonic flight, paving the groundworks for flight speeds exceeding Mach 5. Here, we present a novel ultra-high temperature composite with superior ablation resistances up to 3000 ​°C for 900 ​s, utilizing a tailored ultra-high melting point HfC_0.76N_0.24 matrix reinforced with short carbon fibers. The ablation-resistant capability of this composite is over 14 times greater than that of HfC at 3000 ​°C. Furthermore, this research presents the first comprehensive investigation into the internal mechanisms governing thermal oxidation evolution of HfC_0.76N_0.24 matrix through a combination of experimental results and theoretical simulations. The mechanistic details of these complex oxidation processes are elucidated in terms of chemical bonding and clusters evolutions, along with their relationship to cooperative oxygen atoms and molecules. Notably, nitrogen atoms do not directly generate gas and escape from the composites, rather, they interact with hafnium atoms to form Hf-C-N-O clusters with robust bonding for enhanced viscosity during ablation. These findings provide valuable insights into the transition from micro to macro scales, which will be the paradigm of inspiring and accelerating materials discovery in this field, as well as taking advantage of their full potential in the application of hypersonic aircraft and spacecraft vehicles.