Doping of partially densified aerogels: Impregnation by solution or by xerogel

The silica partially densified aerogels (PDA) are structures constituting good host materials. The choice of specific weight, that is the choice of pore volume useful for doping, is large: 0.8–1.6 g·cm−3. In this work two ways of doping are compared: the first uses an in situ gelation, the second, an alcoholic solution. The gelating solution is composed of tetramethoxysilane and iron acetylacetonate. After gelation, it becomes a silica-iron oxide mixed xerogel inside the pores of the PDA. The second solution uses iron acetylacetonate in alcohol. The evolution of the environment of the iron atom is carried out by Visible spectrometry. The transformation of doped PDA into glass is only possible in the case of the impregnation by the xerogel.