The use of silica aerogels as host matrices for chemical species: Different ways to control the permeability and the mechanical properties

Different sets of silica aerogels (classical aerogels, partially densified aerogels, and composite aerogels) have been studied for their prospective use as host matrices for chemical species. Two relevant parameters, the mechanical properties and permeability, are measured and compared in order to discuss the advantages and drawbacks of the three different synthetic approaches. Mechanical resistance is measured by the static bending technique and permeability by an impregnation method. By adjusting the mechanical resistance and especially the mean pore-size, it is possible to control impregnation of liquid within the porous network of the aerogel. Facile liquid impregnation into mechanically durable aerogels allows one to synthesize different composites and multi-phase materials after soaking, drying and sintering. Three examples of applications are detailed: doped glass for the Faraday effect, glass-ceramics for nuclear waste containment, and liquid crystals in confined media.