In-situ formation of the BSG bubbles toward SiC/SiC composites protection mechanisms under thermal shock treatment

The thermal shock protection of SiC/SiC composites have become pivotal challenges in promoting their application in a heat field environment. This study presents a borosilicate glass (BSG) coating was fabricated successively by slurry brushing-sintering for SiC/SiC composites. The results show that the coated SiC/SiC composites exhibit excellent thermal protective resistance with a rather light mass change (<0.59%) at 1200 °C (ΔT = 1000 °C) for 750 cycles. All tested samples possess a high residual strength of more than 95.71% retention. Moreover, the protection mechanisms of the coated SiC/SiC composites are analyzed that the relevance involves the BSG bubbles in-situ formation and dynamic filling. The bubbles are possibly due to generation and pressure of CO and CO₂ at the SiC-BSG interface during the rapid heating and cooling. The oxidation kinetics is controlled by diffusional mechanisms, and the growth rate constant and kinetic exponent were 0.23 and 0.37 for the BSG@SiC/SiC composites. The internal structure was not oxidized, indicating that the BSG coating has excellent protection.