Facile Fabrication of Ceramic-resin Coatings on C/CA Composites for Oxidation Protection at Medium Temperatures

Carbon fiber-reinforced carbon aerogel (C/CA) composites are one of the most promising candidates for applications requiring both thermal insulation and load bearing capabilities. The preparation of anti-oxidation coatings on C/CA to address its susceptibility to oxidation is a feasible approach to promote its application in oxidative environments. However, the currently reported coatings on C/CA mainly focus on improving the ablation performance and coating preparation process typically necessitating high-temperature heat treatment. This procedure can increase its thermal conductivity and reduce its thermal insulation ability. In this study, a series of ceramic-resin coatings were fabricated on C/CA through a simple slurry brushing-drying approach at room temperature. The effects of phenolic resin content on the coating structure, residual stress, thermal shock, and oxidation behaviors were investigated. Due to the adhesive properties and curing-induced shrinkage, the PR-7.5 coating (containing 7.5% (in mass) phenolic resin in the slurry) exhibits bonding strength close to fracture strength of the substrate and residual compressive stress of 0.853 GPa, which is beneficial for resisting thermal shock cracking. However, excessive resin content (PR-10.0 containing 10.0% (in mass) phenolic resin in the slurry) induces tensile stress due to uneven curing shrinkage, thereby leading to thermal shock cracking. Meanwhile, oxidation tests reveal significantly reduced weight losses for PR-7.5 (17.46% at 800 ℃/100 min, 8.15% at 1000 ℃/120 min, 3.15% at 1200 ℃/120 min) versus uncoated C/CA’s 44.60% loss at 800 ℃/20 min. This work provides a brand-new and simple approach to improving the anti-oxidation performance of C/CA and expands its application in mild oxidative environments.