Magnetic compounds as coatings on polymer particles and magnetic properties of the composite particles

Spherical micron-sized polymer particles coated with magnetite have been prepared by a new method consisting of a two step process, in which iron compounds are coated on a micron-sized polymer core by controlled hydrolysis of FeCl3 in the presence of urea, poly(vinylpyrrolidone) and hydrochloric acid. The thickness of the coating layer could be altered by adjusting the amount of FeCl3 added to the system. Magnetic particles were obtained by treating the coated powders with hydrogen at moderate temperatures. The chemical composition and morphology of the coating layer, and the resulting magnetic properties varied with the calcination conditions.