Experimental and molecular dynamics studies on thermal insulation at high-temperature of SiO2/Al2O3 composite aerogel

SiO2 aerogels have attracted significant attention due to numerous merits and unique physiochemical properties. However, it is challenging to work at high temperatures due to the weak thermal stability. Here, SiO2 aerogels enhanced by Al2O3 particles were prepared by sol-gel method in order to improve its thermal insulation property. The resulting SiO2/Al2O3 composite aerogels possessed porous three-dimensional pores and nano network skeleton structure. Due to the effective amalgamation of silicon and aluminum systems, the weight loss of SiO2/Al2O3 composite aerogels is less than 20% with the increase of temperatures, indicating that thermal stability is improved compared with the original SiO2 aerogels. By investigating temperature changes of specimens during heating processes, SiO2 aerogels with higher Al2O3 contents presents lower average temperature and slowly increase in temperature. This phenomenon illustrates that the Al2O3 particle in SiO2 aerogels can act as a barrier to insulate heat transfer. The effects of temperature, Al2O3 content, and strain on thermal insulation properties of SiO2/Al2O3 composite aerogels are calculated by molecular dynamics simulation method. Based on a series of computional experiments, the increases of temperature and strain have a negative influence on thermal insulation, however, Al2O3 content have a positive impact on this property which is well agreed with the experimental results. The deep understanding of the effects of the introduction of Al2O3 in SiO2 aerogels provides a method for creating excellent thermal insulation materials in heat protection field.