A novel co-continuous Si–Zr hybrid phenolic aerogel composite with excellent antioxidant ablation enabled by sea-island-like ceramic structure at high temperature

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO 2 , SiC and ZrO 2 ) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials.