Preparation of composites of nickel ferrites dispersed in silica matrix

Composites of nickel ferrite particles dispersed in porous silica matrix (NiFe2 O-4/SiO2) have been prepared by sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of ferrite. Wet samples prepared in monolithic form have been dried at 110 degreesC for 24 h and thermally treated for 2 h at various temperatures. NiFe2 O-4 particles were formed in the matrix pores and the nucleation of these particles was observed with the increase in the drying temperature. The structural and magnetic changes of these xerogels have been studied and compared with the properties of nickel ferrites obtained by coprecipitation process. The composites presented magnetic susceptibility values two orders of magnitude higher than that of ferrite prepared by coprecipitation. (C) 2001 Elsevier Science B.V. All rights reserved.