Influence of novel carbon sources on microstructure and properties of (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C high-entropy carbide ceramic

A set of (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C high-entropy carbide (HEC) ceramic samples were produced via spark plasma sintering (SPS) at a temperature of 1900 degrees C utilizing synthesized carbide powders. The carbide powders were synthesized via carbothermal reduction and derived from various carbon sources including carbon black, carbon microspheres, flake graphite, and graphitic carbon spheres. The impact of the different carbon sources was evaluated, for the first time, on the HEC's phase composition, microstructure, mechanical properties, and oxidation behavior. Results show that the HEC prepared using graphitic carbon spheres had a single-phase rock salt structure, with an average grain size of approximately 770 nm, which was smaller than that of HEC samples derived from the other carbon sources, due to its lower oxygen content, better dispersion, and higher chemical reactivity. Additionally, these HEC samples manufactured using graphitic carbon spheres exhibited 98.9% relative density, 20.39 GPa hardness, 4.5 +/- 0.6 MPa & sdot;m1/2 fracture toughness, and excellent oxidation resistance. Therefore, by optimizing the reactivity and dispersion of carbon sources, high-performance HEC ceramics can be created.