Loose porous Cr2O3−Al2O3 aerogels with lightweight, flame retardancy, and rapid cooling properties: Fabrication and mechanism analysis

Background Advanced aerogels with lightweight, flame retardant and rapid cooling properties are urgently needed as thermal insulators in harsh environments. Method The Cr2O3−Al2O3 aerogels were fabricated by simple method and freeze-dried process. A large number of pores were produced in the microstructure of samples by carbonization of soluble starch during calcination. Findings The porous structure makes the density of prepared Cr2O3−Al2O3 aerogel as low as 0.0060 g·cm−3 and the thermal conductivity as high as 0.30 W m−1·K−1, which indicates that the sample has good thermal dissipation and rapid cooling performance. The effect of calcination temperature on cooling rate was studied. The results show that material cooling can be divided into two stages, the second stage is the speed control step. With the increase of the calcination temperature, the cooling rate of sample improves and the cooling time decreases. The prepared Cr2O3−Al2O3 aerogels have good flame retardancy and cannot ignite upon exposure to the burner for 2 min. The flame retardancy and rapid cooling mechanism of the sample was also studied. The Cr2O3−Al2O3 aerogels have the advantages of lightweight, flame retardancy and rapid cooling, which has potential application prospects in the field of flame retardant cooling coatings.