Preparation and molding of ultralow-density silica aerogels

The two-step（acid-base）sol-gel process was used to prepare SiO2 aerogels, with TEOS as the precursor. The influence of catalyst, water and solvent on the sol-gel process was investigated to optimize the experimental conditions. Ultralow-density silica aerogels with densities as low as 3.4 mg/cm3, solid cylinders and shells at various densities(10～50 mg/cm3) were made. Scan electron microscope, pore size distribution techniques were used to characterize the morphology and pore structure of the silica aerogel. The results show that the ultralow-density silica aerogel has good nanostructure with average pore size of 18.9 nm and specific surface area of 898.9 m2/g.