Preparation and characterisation of aerogels and their use as nanocomposites with magnetic and catalytic applications

Aerogels are materials with unique properties which stem from their highly extended and open porosity, very low densities and high inner surface areas. They are prepared by the sol-gel process through special drying techniques which avoid the capillary forces at the liquid/vapor interface which are responsible for shrinkage and cracking, therefore preserving the original porous structure of the alcogels.
The majority of the studies in this field have been devoted to single metal oxide aerogels, and in particular the most investigated system is SiO₂. Multicomponent oxide aerogels can also be obtained by co-gelation of different metal precursors; in this case the preparation can lead either to homogeneous mixed metal oxide aerogels or to heterogeneous products, depending on the precursor reactivity. Heterogeneous aerogels containing nanoparticles dispersed in a highly porous matrix are of great interest because such nanocomposites combine individual properties of the constituent phases giving rise to new functional materials.
Results on the preparation and characterization of different nanocomposite aerogels will be presented. Particular attention will be devoted to nanocomposites containing iron-cobalt alloy nanoparticles dispersed into SiO₂, which are used as catalysts for the production of carbon nanotubes (CNTs), and to nanocomposites containing ferrite nanoparticles dispersed into SiO₂ with interesting magnetic properties. The capability of X-ray Absorption Spectroscopy to study in detail the structural characteristics of such mulicomponent materials will also be explored.