Preparation of high-temperature resistant aluminum-doped silica aerogel from aluminum sol source by ambient pressure drying

The preparation of aluminum-doped silica aerogel (ASA) typically utilizes alumina alkoxides or inorganic aluminum salts as precursors usually hindered by high cost or precursor instability. In this study, we prepared a high-temperature resistant ASA via the sol-gel and atmospheric pressure drying (APD) method, utilizing an inexpensive aluminum sol as the aluminum source, tetraethyl orthosilicate (TEOS) and basic silica sol as the composite silicon source. The effects of the Al/Si molar ratio and calcination temperature on the structure, morphology, and thermal stability of ASA were investigated. The results revealed that ASA-0.2 (with an Al/Si molar ratio of 0.2) exhibited a specific surface area of 616.3 m2/g at room temperature, whereas ASA-0 was 508.2 m2/g. After calcination at 1000 °C for 2 h, ASA-0.2 maintained a significantly higher specific surface area (290.0 m2/g) compared to ASA-0 (23.9 m2/g). Mechanism analysis indicated that adding aluminum sol not only improved the strength of the aerogel skeleton but also inhibited the phase transition of silica, effectively enhancing the high-temperature resistance of the aerogel. The utilization of inexpensive and stable aluminum sol as a precursor presents a promising approach for the industrial production of heat-resistant aerogels.