Preparation of Al2O3-SiO2 aerogel by ambient pressure drying for thermal insulation application

Al 2 O 3 -SiO 2 aerogel (ASA) was prepared by convenient ambient pressure drying using inexpensive AlCl 3 ·H 2 O as precursor, and silicon was deposited during the aging of aluminum gel. To explore the influence of Chloride ion on the property of ASA, ion exchange technology was used to remove the Chloride ion in the aluminum sol. ASA exhibits a low thermal conductivity of 0.029 W m −1  K −1 at room temperature, and the specific surface area of Cl-free ASA after heat-treated at 1200 °C is 95.2 m 2 /g, which is higher than that of the chlorine-containing aerogel (11.4 m 2 /g), showing enhanced thermal stability of ASA. Analysis of XRD and XPS indicate that the removal of chloride ions makes it more difficult for ASA to establish Al–O–Si groups during the aging process, so the γ-Al 2 O 3 and cristobalite phase do not transform to mullite phase at 1200 °C. Due to the better thermal stability of ASA, it has great potential for high-temperature applications in the fields of insulation, thermal protection materials, and building external wall thermal insulation.