US Patent 7897648 Silica aerogels

This invention relates to silica aerogels and to a method for their preparation from rice husk. Rice husk is very rich in silica, and its ash can contain up to 92-97% of amorphous silica. The rice husk ash is prepared by burning the rice husk on a heating plate with excess air until the white ash is obtained. Silica from rice ash husk is in a very active form and has been found to be a very potential starting material for silica aerogels.