Silica aerogel-iron oxide nanocomposites: structural and magnetic properties

Magnetic nanocomposites formed by iron oxide particles hosted in silica aer ogels pores have been synthesized by sol-gel processes and supercritical ev acuation of the solvent. Two iron-containing salts have been essayed: (A) F e(NO3).9H2O and (B) FeNa(EDTA).2H(2)O. The synthetic routes made use of the gel pores as nanoreactors. Structural and magnetic properties have been st udied by combining X-ray diffraction (XRD), N-2 adsorption isotherms, trans mission electron microscopy (TEM), Fe-57 Mossbauer spectroscopy and vibrati ng sample magnetometry (VSM). The nanocomposites properties, i.e., phase of the iron oxide, monolithic integrity, particle size distribution and magne tic phase dilution vary with the chosen synthetic path. The use of EDTA com plex as a nanoparticle precursor increases the average pore diameter of the matrix. The nanocomposites are good candidates for applications in the fie ld of magneto-optical sensors and magnetic devices due to their attractive properties, including soft magnetic behavior, low-density and electric resi stivity. (C) 2001 Elsevier Science B.V. All rights reserved.