Advance in Research of High Temperature Resistant Aerogel Used as Insulation Material

Heat transfer via the solid backbone is low for aerogel due to its ultrahigh porosity,and heat transfer via gaseous phase is inhibited due to its network structure consisting of mesopores(2-50nm)and nanoparticles.The incorporation of so-called infrared opacifiers decreases the radiative heat transfer through reflecting,absorption and scattering processes.Thus,aerogel possesses a quite low thermal conductivity,thus can be used as efficient thermal insulation.Aerogels can be classified into three different categories,i.e.oxide aerogels,carbon aerogels and carbide aerogels,according to their constituents.Oxide aerogels possess relatively low thermal resistance due to their phase changes and particles sintering,but they obtain rather low thermal conductivity.Carbon aerogels have controllable densities and rather high thermal resistance(3000℃)under vacuum or inert atmosphere.The thermal conductivity at2000 ℃ under argon atmosphere is only 0.601W·m-1·K-1,however carbon combustion easily happens in oxidizing atmosphere.This can be solved by coating with some oxidation resistance coatings on the surface of carbon aerogels.There are insufficient studies for carbide aerogels,which mainly concern over SiC aerogel and concentrate on their preparation methods and characterizations,while little attention is paid to their thermal properties of carbide aerogels.Herein,the advances in research of the three different kinds of aerogels are presented,followed by outlook of these high temperature resistant aerogel insulations.