Corrosion behavior of molten silicon on SiC fibers with various coatings

This work investigates the corrosion behavior of silicon carbide (SiC) fibers with various surface coatings during the melt infiltration (MI) process. Uncoated SiC fibers were corroded entirely and reformed into large SiC grains in molten silicon . In contrast, SiC fibers coated with boron nitride (BN) exhibited significantly reduced corrosion. When coated with multiple layers of BN, carbon (C), and silicon nitride (SiN x ), the SiC fibers and the inner BN layer were well protected throughout the MI process. A new BN coating, approximately 30 nm thick, was in-situ formed on the top of surficial carbon layer due to boron precipitation from the molten silicon and nitrogen migration from the inner SiN x coating. The release of nitrogen is believed to result from the crystallization of nitrogen-rich SiN x into α-Si 3 N 4 at high temperatures. These BN/C/SiN x /C multiple layers demonstrate excellent corrosion resistance to molten silicon, highlighting their potential as an interphase for MI-SiC/SiC composites.