Reusable, high specific surface areas, and excellent thermal stability Al2O3–SiO2 aerogel composites as high-temperature thermal insulators for radome applications

In this study, monolithic Al 2 O 3 –SiO 2 aerogels with excellent thermal stability and high specific surface area were synthesized using boehmite nanorods (L=20–30 nm, D=3–5 nm). The high specific surface area of aerogels was maintained after calcination at 800 °C (663.54 m 2 /g), 1000 °C (486.91 m 2 /g), and 1100 °C (230.76 m 2 /g). The anti-sintering mechanism of the Al 2 O 3 -SiO 2 aerogels was discussed. Thanks to the composite of Al 2 O 3 -SiO 2 aerogel and mullite fibers, the disadvantages of brittleness and low strength of aerogel are overcome. The thermal conductivity of the composite is extremely low at 0.034 W/(m·K)-0.089 W/(m·K) (25 °C-1000 °C). Five muffle cycle back-temperature tests at 1000 °C and a butane blowtorch back-temperature test at 1350 °C also proved that the composites have excellent thermal insulation properties. Composites with excellent thermal insulation properties combined with lightweight, thinness, machinability, and good dielectric properties meet the need for high-temperature thermal insulating-wave transmitting integrated materials for hypersonic missile radomes.