Advanced Ablation-Resistant HfC 0.76 N 0.24 at 3000℃ with Record Melting Point Over 4400k

Today's demand for hypersonic vehicles is facing a bottleneck with developing ultra-high-temperature ceramics(UHTCs) that are able to effectively resist the severe thermal ablation and structural stresses produced by elevated speeds. Here we design and synthesize the HfC0.76N0.24 compound that possesses an unprecedented high melting point at 4419 ± 37K, realizing a huge jump of existing highest melting temperature. Besides, it exhibits exceptional ablation resistance at 3000 ℃ with significant drop of the ablation loss rates(~0.061mg/cm2∙s, 0.001mm/s) by 89.1% and 90.9% compared with conventional HfC(~0.561mg/cm2∙s, 0.011mm/s). Such superb performance is the result of the coordination effect of optimized N, modifying the nearest neighbor surrounding of the central metal atom, which leads to much stronger metal-nonmetal bonds and better oxidation resistance. Thus, the oxidation of hafnium could be obstructed owing to the enhanced competition of neighboring carbon and nitrogen in the system. From this respect it provides new insights of ultra-high-temperature ceramics towards ablation resistance mechanisms, as the finely regulated ablation property by adjusting its atomic configuration with electronic feature through tailoring of a new composition space.