Oxidation protection of ultra-high temperature ceramic Zr_xTa_1-xB₂-SiC/SiC coating prepared by in-situ reaction method for carbon/carbon composites

To improve the oxidation protection effect of Si-based coatings containing ZrB₂ or TaB₂ ceramics, ZrO₂, Ta₂O₅, B₂O₃, Si and C powders were used as raw materials to prepare the outer Zr_xTa_1-xB₂-SiC coating by in-situ reaction method on SiC coated C/C composites. Zr_xTa_1-xB₂ phase was obtained by co-reducing ZrO₂ and Ta₂O₅ using B₂O₃ and C in the heat-treatment process at 2373K. Isothermal oxidation test at 1773K and TGA test from room temperature to 1773K were used to evaluate the oxidation protection effect of the coated C/C composites. During oxidation, an "inlaid structure" Zr-Ta-Si-O compound glass layer forms on the surface of the Zr_xTa_1-xB₂-SiC coating. The Zr_xTa_1-xB₂-SiC/SiC coating not only can protect C/C from oxidation at 1773K for 1412h with only 0.1wt.% loss, but also can provide an effective protection for C/C at a wide range of temperature from room temperature to 1773K.