Polymer Derived SiAlCN for Environmental Barrier Coatings

Silicon-based ceramics and composites are one of the most promising candidates for high temperature structural components in next generation gas turbines due to their excellent thermo-mechanical properties. However, these materials severely degraded when used in high temperature oxidizing environments, particularly, in the presence of corrosive species such as alkali elements or water vapor. Currently, the most promising approach with near-term benefits is to employ environmental barrier coatings (EBCs) that prevent direct contact between silicon-based materials and aggressive environments exist in turbine engines. Previous work on EBCs has primarily focused on using oxide coatings because oxides are in general more resistant to corrosive environments than Silicon-based ceramics. In this study, we propose to develop polymer-derived SiAlCN amorphous ceramics for EBC applications. Our research revealed that the oxidation rate of the SiAlCN ceramics is about 10 times lower than the lowest values observed on chemical vapor deposition (CVD) silicon carbide/nitride. Furthermore, the SiAlCN also exhibited good corrosion resistance to alkali salt at elevated temperatures.