High-entropy carbide ceramics with refined microstructure and enhanced thermal conductivity by the addition of graphite

Aiming at the refined microstructure and enhanced thermal conductivity of high-entropy carbide (HEC) ceramics for high-temperature applications, the addition effect of graphite was comprehensively investigated in this study. HEC ceramics incorporated with different contents of graphite were solidified by spark plasma sintering (SPS) using self-synthesized high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C powder and graphite as starting materials. The results demonstrate that the incorporated graphite removed the oxygen impurity in the mixed powders, decreased the oxygen content and increased the lattice parameter of the HEC phase, and improved the densification behavior of HEC ceramics. On the other hand, the addition of graphite brings a refinement of HEC grains and improves the mechanical properties. More importantly, the thermal conductivity of the HEC ceramics was significantly increased owing to the removing effect of oxide impurity by the added graphite. It is considered that the lattice purified HEC grains with low oxygen content contribute to the improvement in thermal conductivity of the ceramics.

Automated summary

The study comprehensively investigated the addition effect of graphite on high-entropy carbide (HEC) ceramics, showing that graphite added removed oxygen impurity, increased lattice parameter, improved densification behavior, refined HEC grains, and enhanced mechanical properties of the ceramics. Importantly, graphite addition significantly increased thermal conductivity due to the removal of oxide impurity, leading to improved thermal conductivity of the ceramics.