Heat-resistant, strong alumina-modified silica aerogel fabricated by impregnating silicon oxycarbide aerogel with boehmite sol

In order to overcome the fragility and sintering behavior of silica aerogel at high temperature, heat-resistant and strong alumina-modified silica aerogel was fabricated by impregnating silicon oxycarbide (SiOC) aerogel with industrial boehmite sol. The partial sintering of SiOC aerogel during its pyrolysis endowed alumina-silica aerogel its high strength. Meanwhile, the carbon in SiOC can also act as a pore former due to oxidation with O2 during the subsequent calcination in air. This approach is straightforward and economical. The as-prepared composite aerogel exhibited high surface area (278 m2/g) and compressive strength of up to 2.17 MPa. Compared to SiO2 aerogel prepared using the same method, the composite aerogel was found to be more heat resistant. After being heated to 1000 °C and 1200 °C for 2 h, the surface area of composite aerogel reached up to 183 and 22 m2/g, respectively. On the other hand, the corresponding values for linear shrinkage were as low as 6.93% (for 1000 °C) and 18.90% (for 1200 °C). The XRD patterns indicated that amorphous SiO2 and γ-Al2O3 remained in the composite aerogel after heat-treatment at 1200 °C.