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

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 x 10(-3) g center dot cm(-2) and the matching weight loss rate of 5.71 x 10(-5) g center dot cm(-2)center dot 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.