Nanoengineering Super Heat-Resistant, Strong Alumina Aerogels

Because of ultralow thermal conductivity, excellent catalytic activity, and better heat resistance than silica aerogel, alumina-based aerogel has drawn great interest as thermal insulators and catalysts. However, it is too fragile and sinters above 1000 °C (it shrinks drastically, >50%, and leaves the surface area as low as 10–70 m2/g at 1300 °C), which badly limits its high-temperature applications. Herein, super heat-resistant, strong alumina aerogels are prepared via a novel acetone-aniline in situ water formation (ISWF) method combined with novel modification techniques: supercritical fluid modification (SCFM) and hexamethyldisilazane gas phase modification. The heat resistance of alumina aerogel is enhanced up to 1300 °C via this method. The shrinkage of the optimized alumina aerogel is reduced to as low as 1 and 5% and the corresponding surface area reaches up to 152–261 and 125–136 m2/g after being heated to 1200 and 1300 °C for 2 h, respectively. The strength is significantly increased by more than 120% through SCFM. It also exhibits excellent thermal insulation properties at temperatures up to 1300 °C. This may significantly contribute to their practical ultrahigh-temperature applications in thermal insulations, catalysts, catalyst supports, etc.