Design, formation, and property of high emissivity WSi2-Si-glass hybrid coating on fibrous ZrO2 ceramic for reusable thermal protection system

The objective of this research was to develop a high emissivity coating on the low thermal conductive insulation for reusable thermal protection system. The design principles including high emissivity, match of the coefficients of thermal expansion and excellent high temperature stability were proposed for the first time. A novel WSi2-Siglass hybrid coating with optimized composition was successfully prepared on fibrous ZrO2 ceramic insulation by slurry dipping and subsequent high temperature rapid sintering method. The total emissivity of the as-prepared coating is up to 0.92 in wavelength of 0.3-2.5 pm. After oxidation at 1673 K for 100 h and 1773 K for 20 h, the total emissivity values of the coatings are still as high as 0.89 and 0.87. A competitive mechanism between the "defects formation" caused by aging stress, the CTE mismatch stress and the volatilization of low melting point oxides and the "defects healing" resulted from self-healing phases during the different oxidizing conditions was discussed.