| abstract |
A two-step method is described for making transparent aerogels which have a density of less than 0.003 g/cm3 to those with a density of more than 0.8 g/cm3, by a sol/gel process and supercritical extraction. Condensed metal oxide intermediate made with purified reagents can be diluted to produce stable aerogels with a density of less than 0.02 g/cm3 including densities lower than 0.003 g/cm3. High temperature, direct supercritical extraction of the diluted alcogels produces hydrophobic aerogels which are stable at atmospheric moisture conditions. Monolithic, low density homogeneous silica aerogels have high thermal insulation capacity, improved mechanical strength and good optical transparency. |