Amorphous silicoboron carbonitride monoliths resistant to flowing air up to 1800 °C

The oxidation resistance of amorphous Si-B-C-N monolith was investigated at 1500-1800 degrees C. The oxide products are amorphous SiO2 and cristobalite underlying amorphous oxide scale. The release of gases including CO, COB, N-2 and evaporation of B2O3 result in formation of bubbles and loose, porous oxide scale at 1600 degrees C. Si-B-C-N monolith exhibits oxidation resistance superior to SiC and Si3N4 above 1600 degrees C, and retains significant resistance to oxidation up to 1800 degrees C. The formation of dense, passivating surface layers of N-containing amorphous SiO2, the ternary chemical bonds and capsule-like structures are primarily responsible for the oxidation resistance. (C) 2016 Elsevier Ltd. All rights reserved.