Self-healing behavior of Sc2Si2O7/SiC composites for environmental barrier coatings

The high-temperature oxidation and self-healing behavior of promising environmental barrier coating material Sc2Si2O7 containing 10 vol% SiC dispersed nanoparticles is reported for oxidation times up to 10 h at temperatures of 1100 and 1300°C. Sc2Si2O7/SiC nanocomposites were prepared by spark-plasma sintering. Artificially induced surface cracks did not fully recover after 10 h at 1100°C but did fully recover after heat treatment at 1300°C for 5 h in air. The mechanism of self-healing is attributed to the volume expansion resulting from oxidation of SiC to SiO2 at elevated temperature. The oxidized zones within the composites were confirmed to be thicker after heating at 1300°C than at 1100°C, their depths following a parabolic rate law with constants of 6.2 × 10-11 and 1.9 × 10-12 m2/s, respectively. The results show that Sc2Si2O7/SiC nanocomposites exhibit self-healing properties, and thus may be attractive for propulsion applications when considering their lower specific gravity and good corrosion resistance.