A Facile Method to Fabricate Al₂O₃-SiO₂ Aerogels with Low Shrinkage up to 1200 °C

Monolithic Al₂O₃-SiO₂ composite aerogels were synthesized by using inexpensive aluminum chloride hexahydrate (AlCl₃·6H₂O) and tetraethyl orthosilicate (TEOS). By adjusting the molar ratio of Al and Si, the best ratio of high-temperature resistance was found. The resultant aerogels (Al:Si = 9:1) exhibit high thermal performance, which can be identified by the low linear shrinkage of 5% and high specific surface area (SSA) of 283 m²/g at 1200 °C. Alumina in these aerogels mainly exists in the boehmite phase and gradually transforms into the θ-Al₂O₃ phase in the process of heating to 1200 °C. No α-Al₂O₃ is detected in the heating process. These Al₂O₃-SiO₂ composite aerogels are derived from a simple, low-priced and safe method. With their high thermal performance, these aerogels will have a wide application in high-temperature field.