Spray freeze-dried monolithic silica aerogel based on water-glass with thermal superinsulating properties

•Monolithic silica aerogels were prepared by spray freeze drying.•Tert-butyl alcohol is in favor of optimizing the pore structure.•Prepared aerogels possess low thermal conductivity and high thermal stability. In this study, silica aerogels were prepared using water-glass precursor based on two drying strategies, namely conventional freeze drying (C-FD) and spray freeze drying (S-FD). It was known that the pore structure of silica aerogel can be optimized uniformly based on S-FD method when tert-butyl alcohol is directly utilized as a solvent. As a result, silica aerogels obtained by the S-FD method are monolithic with high thermal stability and low thermal conductivity, showing a great potential of thermal insulation materials for high-temperature environment.