Ta_xHf_1-xB₂-SiC multiphase oxidation protective coating for SiC-coated carbon/carbon composites

A Ta_xHf_1-xB₂-SiC coating was prepared by in-situ reaction method on SiC coated C/C composites. Ta_xHf_1-xB₂ phase is the form of solid solution between TaB₂ and HfB₂. Isothermal oxidation behavior at 1773K and ablation behavior of the coated C/C were tested. Ta_xHf_1-xB₂-SiC/SiC coating could protect the C/C from oxidation at 1773K for 1480h and ablation above 2200K for 40s. During oxidation, oxides of Ta and Hf atoms exist as "pinning phases" in the compound glass layer consisted of outer Ta-Si-O compound silicate layer and inner SiO₂ glass layer, which was responsible for the excellent oxidation resistance.