Preparation of iron particles coated with silica

A method is described for coating fine iron particles (similar to 1 mu m) with a uniform silica layer, produced by the hydrolysis of tetraethyl orthosilicate. The presence of a small amount of gelatin on the surface of the iron particles facilitates this process. X-ray photoelectron measurements indicate that the gelatin interacts with the surface of the iron particles through both nitrogen (in -NH2 groups) and oxygen (in -COOH groups) and then binds to the silica. The silica coating increases the resistance of the iron particles to oxidation on heating in air, raising the temperature at which a detectable oxidization occurs from 330 to 400 degrees C. (C) 1999 Academic Press.