Low-density phenolic-modified silica-aluminum aerogel composites for high-temperature thermal protection above 1300 °C

Lightweight ablation–resistant materials prepared by organic–inorganic hybridization are of great importance for aerospace thermal protection materials. The organic–inorganic hybrid Phenolic Resin (PR)/SiO 2 /Al 2 O 3 composite aerogels (PSA) were fabricated through sol–gel. The PSA composite aerogels showed fascinating properties, resulting in high specific surface (517.07–731.65 m 2 /g), low density (0.104–0.139 g/cm 3 ), and low thermal conductivity (0.032–0.043 W/(m·K)). Especially, the PSA composite aerogels exhibited an ultra–high specific surface (285.07 m 2 /g), when the heat treatment was at 1300 °C in the Ar atmosphere for 5 h. The carbon fiber reinforced PSA aerogels (PSA/CF) indicated a low density (0.212–0.240 g/cm 3 ), low thermal conductivity (0.067–0.0717 W/(m·K)), high compressive strength (2.64–5.20 MPa). The PSA/CF composites exhibited effective thermal insulation when exposed to a 1300 °C butane torch for 60 s, with the back surface temperature at the center point ranging from 152.1 to 167.0 °C. The PSA/CF composites are promising for ablation–resistant thermal insulation, high–temperature resistance, and thermal protection applications.