High thermally insulating and lightweight Cr2O3 − Al2O3 aerogel with rapid–cooling property

Advanced aerogel materials with lightweight, flame retardant, and rapid cooling properties are urgently needed as thermal insulators in harsh environments. Herein, Cr2O3 − Al2O3 aerogels (CrAAs) were fabricated through a simple method and an ambient pressure drying process. A large number of pores were produced in the microstructure of the sample by the carbonization of soluble starch during calcination. The porous structure decreases the density of the prepared CrAA (Cr2O3 − Al2O3 aerogel) to as low as 0.143 g cm−3, and increases the thermal conductivity to as high as 0.125 W m−1 K−1, indicating the good thermal dissipation and rapid cooling performance of the sample. The prepared CrAAs possess a variety of composite properties such as good flame retardancy, rapid cooling, and colour restore after flame is extinguished. Moreover, after being subjected to flame treatment at ∼ 1300 °C using a butane blowtorch for 5 min, the CrAAs can be rapidly cooled to about 39.2 °C in about 1–2 min. The mechanism of the rapid cooling property was herein analysed, and we anticipate the potential application of CrAAs in flame–retardant cooling coatings.