Boro/carbothermal reduction co-synthesis of dual-phase high-entropy boride-carbide ceramics

Dense, dual-phase (Cr,Hf,Nb,Ta,Ti,Zr)B2-(Cr,Hf,Nb,Ta,Ti,Zr)C ceramics were synthesized by boro/carbothermal reduction of oxides and densified by spark plasma sintering. The high-entropy carbide content was about 14.5 wt %. Grain growth was suppressed by the pinning effect of the two-phase ceramic, which resulted in average grain sizes of 2.7 +/- 1.3 mu m for the high-entropy boride phase and 1.6 +/- 0.7 mu m for the high-entropy carbide phase. Vickers hardness values increased from 25.2 +/- 1.1 GPa for an indentation load of 9.81 N to 38.9 +/- 2.5 GPa for an indentation load of 0.49 N due to the indentation size effect. Boro/carbothermal reduction is a facile process for the synthesis and densification of dual-phase high entropy boride-carbide ceramics with both different combi-nations of transition metals and different proportions of boride and carbide phases.

Automated summary

Dense, dual-phase (Cr,Hf,Nb,Ta,Ti,Zr)B2-(Cr,Hf,Nb,Ta,Ti,Zr)C ceramics were synthesized and densified by boro/carbothermal reduction of oxides and spark plasma sintering, respectively. The high-entropy carbide content was about 14.5 wt%. The pinning effect of the two-phase ceramic suppressed grain growth, resulting in average grain sizes of 2.7+/-1.3 mu m for the boride phase and 1.6+/-0.7 mu m for the carbide phase. Vickers hardness values increased from 25.2+/-1.1 GPa to 38.9+/-2.5 GPa due to the indentation size effect. Boro/carbothermal reduction is a convenient method for synthesizing and densifying dual-phase high entropy boride-carbide ceramics with different combinations of transition metals and different proportions of boride and carbide phases.