Oxidation protection of tri-layer La2Zr2O7/Yb2Si2O7/SiC-coated Cf/SiC composites at high temperature

Abstract

Ytterbium silicate (Yb₂Si₂O₇) and lanthanum zirconate (La₂Zr₂O₇) ceramic powders were synthesized by the sol–gel method. A novel tri-layer La₂Zr₂O₇/Yb₂Si₂O₇/SiC environmental barrier coating was prepared on the surface of C/SiC composites to improve the service temperature of the coating (above the Si melting point, 1683 K). Results show that both Yb₂Si₂O₇ and La₂Zr₂O₇ ceramic powders had extremely high purity and were accompanied by a large number of nanoparticles. The tri-layer La₂Zr₂O₇/Yb₂Si₂O₇/SiC coating can efficiently prevent the oxidation failure of C/SiC composites in 1773 K air environment for more than 100 h with slight weight loss of 5.71 × 10⁻³ g·cm⁻² and the matching weight loss rate of 5.71 × 10⁻⁵ g·cm⁻²·h⁻¹. No significant chemical reaction was observed between Yb₂Si₂O₇ middle and La₂Zr₂O₇ outer coatings during the oxidation process at 1773 K, indicating that the tri-layer La₂Zr₂O₇/Yb₂Si₂O₇/SiC coating had better oxidation stability in 1773 K air environment.