Preparation of Iron Particles Coated with Silica

A method is described for coating fine iron particles ( approximately 1 µm) 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 -NH(2) 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. Copyright 1999 Academic Press.