Multicomponent (Hf_0.25Zr_0.25Ti_0.25Cr_0.25)B₂ ceramic modified SiC–Si composite coatings: In-situ synthesis and high-temperature oxidation behavior

High-entropy ceramics, a novel type of multicomponent materials with broad application prospects, have stirred up world-wide interests for over a decade. In the current work, in-situ high-entropy (Hf_0.25Zr_0.25Ti_0.25Cr_0.25)B₂ ceramic modified SiC–Si (HETMB₂-SiC-Si) coating was deposited on carbon/carbon (C/C) composites via gaseous reactive infiltration of Si assisted slurry painting (GRSI-SP) method, to improve the oxidation protective ability of C/C composites at 1973 K. The formation and oxidation mechanisms of the coating was explored by first-principles simulation, experiment and thermodynamic analyses. The coating prepared at 2373 K shows dense mosaic structure filled with HETMB₂-rich Si-based multiphase. This coating adheres well with the C/C substrate, which is ascribed to the formed zigzagged SiC–Si transition layer. This coating protected C/Cs from oxidation for more than 205 h at 1973 K. The enhanced oxidation protective ability is mostly ascribed to the subsequently generated compact and stable Hf-Zr-Ti-Cr-Si-O composite oxidation scale. This research will start up novel research ares of developing high-entropy materials modified coatings with improved protective ability under extreme environments.