Abstract

FeCo–SiO₂ nanocomposite aerogels were prepared by high temperature supercritical drying of alcogels obtained using tetraethoxysilane, iron nitrate and cobalt nitrate as precursors. The structural evolution of the samples at the various stages of the preparation was studied by thermal analysis, transmission electron microscopy, nitrogen physisorption measurements and X-ray diffraction. Different experimental conditions of the supercritical drying process give rise to different porous structures in the silica matrix which have a strong influence on the formation of the FeCo alloy nanoparticles. Bcc FeCo alloy nanoparticles of the expected composition are obtained in the microporous samples while in the mesoporous samples a bcc alloy with a lower Co content is obtained which is accompanied by pure fcc Co.