Low-cost and fast synthesis of nanoporous silica cryogels for thermal insulation applications

Nanoporous silica cryogels with a high specific surface area of 1095 m² g^-1 were fabricated using tert-butyl alcohol as a reaction solvent, via a cost-effective sol-gel process followed by vacuum freeze drying. The total time of cryogel production was reduced markedly to one day. The molar ratio of solvent/precursor, which was varied from 5 to 13, significantly affected the porous structure and thermal insulating properties of the cryogels. The silica cryogels with low densities in the range of 0.08-0.18 g cm^-3 and thermal conductivities as low as 6.7 mW (m·K)^-1 at 100 Pa and 28.3 mW (m·K)^-1 at 10⁵ Pa were obtained using this new technique.