Preparation and molding of ultralow-density silica aerogels

The two-step(acid-base)solgel process was used to prepare SiO_2 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/cm~3,solid cylinders and shells at various densities(10～50 mg/cm~3) 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 m~2/g.