Microstructure and dielectric property evolution of self-healing PDC-SiBCN in static air

The amorphous PDC-SiBCN was oxidized at 900–1100 °C in static air. Borosilicate glass formed from the reaction between B₂O₃ and SiO₂, the cracks were healed by liquid-like glass phase in PDC-SiBCN. The content of B element decreased with the rising oxidation temperature resulting from the volatilization of B₂O₃. The dense SiO₂ scale with the thickness of 2–3 μm can be observed by TEM after oxidation at 1100 °C, some B, C, and N atoms distributed in SiO₂ scale. Cristobalite generated around the boundary between the oxide scale and substrate. With the protection of outer oxide scale, the inner retained amorphous SiBCN phase. The tendency of mass change was firstly decreased, then essentially unchanged, finally increased. The low permittivity was measured in as-fabricated PDC-SiBCN, then it decreased with the consumption of dielectric phase. PDC-SiBCN is a promising material as oxidation resistance and electromagnetic wave transparent matrix in ceramic matrix composite.