Sol-gel preparation and characterization of Ni-SiO2 nanocomposites

A series of Ni-SiO2 composites, in the range 7-80 mol% of nickel, were prepared by two gelation methods with tetraethylorthosilicate (TEOS) and nickel(II) nitrate as starting materials. In the first method an aqueous solution of the salt was used while the second employed an alcoholic solution. The methods also differed in the intermediate thermal treatments of the gels. All the systems were reduced at temperatures around 500 degrees C in flowing hydrogen and were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nanometre sized nickel par tides, homogeneously dispersed over the silica support, were observed in the samples with the smaller Ni content obtained by both methods, but only the one which made use of the alcoholic solution was successful in providing nanometre sized particles with size increasing with increasing concentration. (C) 1998 Elsevier Science B.V. All rights reserved.