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

Ytterbium silicate (Yb 2 Si 2 O 7 ) and lanthanum zirconate (La 2 Zr 2 O 7 ) ceramic powders were synthesized by the sol–gel method. A novel tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /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 Yb 2 Si 2 O 7 and La 2 Zr 2 O 7 ceramic powders had extremely high purity and were accompanied by a large number of nanoparticles. The tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /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 Yb 2 Si 2 O 7 middle and La 2 Zr 2 O 7 outer coatings during the oxidation process at 1773 K, indicating that the tri-layer La 2 Zr 2 O 7 /Yb 2 Si 2 O 7 /SiC coating had better oxidation stability in 1773 K air environment.