Low-temperature sintering of single-phase, high-entropy carbide ceramics

Dense (Hf, Zr, Ti, Ta, Nb)C high-entropy ceramics were produced by hot pressing (HP) of carbide powders synthesized by carbothermal reduction (CTR). The relative density increased from 95% to 99.3% as the HP temperature increased from 1750 degrees C to 1900 degrees C. Nominally phase pure ceramics with the rock salt structure had grain sizes ranging from 0.6 mu m to 1.2 mu m. The mixed carbide powders were synthesized by high-energy ball milling (HEBM) followed by CTR at 1600 degrees C, which resulted in an average particle size of similar to 100 nm and an oxygen content of 0.8 wt%. Low sintering temperature, high relative densities, and fine grain sizes were achieved through the use of synthesized powders. These are the first reported results for low-temperature densification and fine microstructure of high-entropy carbide ceramics.