Self‐Generating High‐Temperature Oxidation‐Resistant Glass‐Ceramic Coatings for C–C Composites Using UHTC s

Carbon–carbon (C–C) composites are ideal for use as aerospace vehicle structural materials; however, they lack high‐temperature oxidation resistance requiring environmental barrier coatings for application. Ultra high‐temperature ceramics ( UHTC s) form oxides that inhibit oxygen diffusion at high temperature are candidate thermal protection system materials at temperatures >1600°C. Oxidation protection for C–C composites can be achieved by duplicating the self‐generating oxide chemistry of bulk UHTC s formed by a “composite effect” upon oxidation of ZrB 2 – SiC composite fillers. Dynamic Nonequilibrium Thermogravimetric Analysis ( DNE ‐ TGA ) is used to evaluate oxidation in situ mass changes, isothermally at 1600°C. Pure SiC ‐based fillers are ineffective at protecting C–C from oxidation, whereas ZrB 2 – SiC filled C–C composites retain up to 90% initial mass. B 2 O 3 in SiO 2 scale reduces initial viscosity of self‐generating coating, allowing oxide layer to spread across C–C surface, forming a protective oxide layer. Formation of a ZrO 2 – SiO 2 glass‐ceramic coating on C–C composite is believed to be responsible for enhanced oxidation protection. The glass‐ceramic coating compares to bulk monolithic ZrB 2 – SiC ceramic oxide scale formed during DNE ‐ TGA where a comparable glass‐ceramic chemistry and surface layer forms, limiting oxygen diffusion.