Preparation of Ultralow Density Porous SiO_2 Doped With GeO_2

SiO 2/GeO 2 binary aerogels with density ranging from 5 kg/m 3 up to 300 kg/m 3 are prepared via sol gel process followed by a supercritical drying technique. SEM, BET nitrogen adsorption method, X ray photoluminescence analysis and Rutherford back scattering analysis are used to characterize the structure and the contents of the binary aerogels. The GeO 2 concentration of the binary aerogels can be ranging from 0% up to almost 80%. But with the increase of GeO 2 concentration, the strength and transparency of the binary aerogel decrease dramatically. The specific surface, pore distribution as well as the network structures are also changing with the change of the GeO 2 content. This preparation method can also be used to prepare all kinds of other binary aerogels. For the alkoxides having quite different reactivity, this method is quite satisfactory.