Novel refractory high-entropy ceramics: Transition metal carbonitrides with superior ablation resistance

A novel high-entropy material as well as ultra-high temperature ceramic (Ta0.2Hf0.2Zr0.2Ti0.2Nb0.2)C0.8N0.2 was synthesized from ten kinds of transition metal carbides and nitrides, via high-energy ball-milling and spark plasma sintering. Besides, the ablation behavior of high-entropy ceramic was first studied by oxy-acetylene torch system at 2500 K. The results showed that optimized nitrogen substituted in sublattice could remarkably improve the ablation resistance by an impressive 57±1 % and 72 ±1 % in mass ablation rate and linear ablation rate compared to high-entropy carbides, since the highly dense multiple oxides scale with large Hf-Zr-rich grains skeleton surrounded by continuous secondary-phase in the boundaries that was able to retard the diffusion of oxygen.