Iron oxide-silica aerogel and xerogel nanocomposite materials

The sol-gel method was used to prepare iron oxide-silica nanocomposite mate rials. Different drying conditions were used in order to obtain aerogel and xerogel materials. The samples were characterized by thermal analysis, X-r ay diffraction (XRD), N-2-physisorption and transmission electron microscop y (TEM) techniques. Aerogel samples have a much higher surface area than th e xerogel samples; moreover, different supercritical drying conditions give rise to a different porous structure. The stabilization of the maghemite p hase in the xerogel nanocomposites depends on the iron content and it is mo re difficult in the aerogel samples. The early sol-gel preparation stages a lso play an important role. (C) 2001 Elsevier Science B.V. All rights reser ved.