High Entropy Boride-SiC Composite: Synthesis, Characterization and Thermo-oxidative behaviour

Silicon carbide reinforced multicomponent high entropy diboride-based particulate composites (HEB-SiC) were fabricated by spark plasma sintering at 1800°C using diboride powders prepared from boro-carbothermal reduction method to investigate the influence of the addition of SiC (SiC content = 20, 40 vol%) on the microstructural evolution, oxidation, and exposure to arc-jet behaviour was reported. SiC has been found to improve the densification of pristine diboride, with attainment of a maximum of ~ 98% relative density for SiC content of 40 vol%. A percolating network of SiC grains in the HEB matrix was observed in the case of composites with 40% volume fraction of SiC. The oxidative behavior at 1400°C in air revealed excellent improvement of oxidation resistance of 20 vol% SiC reinforced composite as compared to other sintered specimens. Arc-jet testing on 20 vol% SiC reinforced composite revealed no structural deformity with very minute-scaled formation of surface oxide layers. These results indicate that the addition of 20 vol% SiC in a diboride matrix can contribute to the optimal preparation of high entropy diboride-based ceramics with balanced mechanical properties with improved oxidation resistance.