Hydrothermal assisted synthesis of heat resistant, well-crystallized aerogels constructed by boehmite nano rods

Abstract

Alumina aerogels in previous studies which are generally weakly-crystallized tend to experience framework coarsening and corundum formation above 1000 °C. In this work, a straightforward strategy, including hydrothermal treatment and supercritical drying, is developed for tailoring the crystallinity of boehmite colloid and for synthesizing heat resistant, well-crystallized alumina aerogels. Thermal evolution of the aerogel and factors influencing the thermal stability were investigated and discussed in detail. Compared to reported pristine alumina aerogels, the aerogel after calcination at 1300 °C for 2 h shows quite high specific surface area (95 m2/g) and pore volume (0.28 cm3/g), which are 38% and 61% of the corresponding maintenance of the samples at 300 °C, respectively, with α-Al2O3 transition significantly retarded. These findings represent a general rule towards the improvement of heat-resistance of alumina aerogels.