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 the improvement of the ablation performance, with the coating preparation process typically necessitating high-temperature heat treatment.This procedure will increase the thermal conductivity of C/CA and reduce its thermal insulation ability.In this study, a series of ceramic-resin coatings were fabricated on C/CA through a simply slurry brushing-drying approach at room temperature.The effects of phenolic resin content on the coating structure, residual stress, thermal shock, and oxidation behavior 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 the fracture strength of the substrate and a residual compressive stress of 0.853 GPa, which is beneficial for resisting thermal shock cracking.However, excessive resin content (PR-10) was found toinduce 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 C/100 min; 8.15% at 1000 C/120 min; 3.15% at 1200 C/120 min) versus uncoated C/CA's 44.60% loss at 800 C/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.