Oxidation protection of ultra-high temperature ceramic ZrxTa1−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 ZrxTa1−xB2–SiC coating by in-situ reaction method on SiC coated C/C composites. ZrxTa1−xB2 phase was obtained by co-reducing ZrO2 and Ta2O5 using B2O3 and C in the heat-treatment process at 2373 K. Isothermal oxidation test at 1773 K and TGA test from room temperature to 1773 K 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 ZrxTa1−xB2–SiC coating. The ZrxTa1−xB2–SiC/SiC coating not only can protect C/C from oxidation at 1773 K for 1412 h with only 0.1 wt.% loss, but also can provide an effective protection for C/C at a wide range of temperature from room temperature to 1773 K.