Abstract
Silica-supported maghemite was prepared by the pyrolysis of a ternary composite of poly (vinyl alcohol) (PVA), iron (III) hydroxide and silica gel, and was characterized by X-ray diffraction, infrared spectroscopic and BET surface area measurements. Particles of maghemite in silica were of <10nm in diameter and stable up to 800°C. The formation mechanism of maghemite in silica was proposed as follows: Iron oxide formed by the dehydration of iron (III) hydroxide was reduced at elevated temperature to magnetite by either PVA itself or its degraded residue, and then the magnetite was oxidized gradually to maghemite.
