Super Thermal Insulating SiO2 Cryogels Prepared by Vacuum Freeze Drying
Traditionally, silica aerogels with low thermal conductivity are prepared by supercritical drying, however, the process is expensive and hazardous due to it run in autoclaves. In order to overcome these disadvantages, a cheaper and safer process, drying at ambient pressure has been developed for decades, but tedious repetitive gel washing and solvent exchange steps are involved. Therefore, in the present study, a novel vacuum freeze-drying was utilized to prepare the super thermal insulating SiO2 cryogels. The wet gels were synthesized via acid-base catalysis using tetraethoxysilane (TEOS) as a silica precursor and ethanol as a solvent. After vacuum freeze drying, nanoporous SiO2 cryogels with low density in the range of 0.08-0.15 g/cm3 were obtained.
Wei Pan and Jianghong Gong
L. F. Su et al., "Super Thermal Insulating SiO2 Cryogels Prepared by Vacuum Freeze Drying", Advanced Materials Research, Vols. 105-106, pp. 851-854, 2010