Effect of SiO2 deposition on thermal stability of Al2O3-SiO2 aerogel

The SiO2-deposited Al2O3-SiO2 aerogel (Si-ASA) with high thermal stability and mechanical properties was synthesized by silica deposition method during aging. Compared with the ASA without silica deposition, the Si-ASA maintains higher specific surface areas after being calcined at 1000 °C (384.0), 1100 °C (245.5), and 1200 °C (124.2 m2/g). When the heating temperature exceeds 1000 °C, the mullite phase begins to appear, and the crystallization activation energy of the Si-ASA (1019.24 kJ/mol) is higher than that of the ASA (975.95 kJ/mol). The results show that silica deposition can restrain viscous flow between particles and increase skeleton strength by particles growth and skeleton coarsening, and it can restrain the growth of γ-Al2O3 by forming more SiOAl bonds in the system. This work is of great significance to the design of super thermal insulation materials with high thermal stability.