Magnetite Formation and Its Surface Reaction in Aqueous Solution

Abstract

When a Fe₃O₄ film deposited on a stainless steel was soaked in a Fe(OH)₂ suspension bubbled with air, Fe₃O₄ grew on the film. Its surface reaction was investigated. When iron(II) ions adsorbed on the film were oxidized, a γ-FeOOH-like layer was formed and transformed to Fe₃O₄ through further adsorption of iron(II) ion. A γ-FeOOH film deposited on a stainless steel by anodic oxidation was transformed to a Fe₃O₄ film through adsorption of iron(II) ion. Moreover, it was found that the surface of the Fe₃O₄ formed in the course of the air oxidation was composed of a γ-FeOOH-like layer and the iron(II) ion adsorbed on the layer. A surface reaction mechanism that the γ-FeOOH-like layer is formed on the surface by oxidation of the adsorbed iron(II) ion and transformed to the new Fe₃O₄ layer is speculated on the basis of the above results. A ferrite formation mechanism in solution was also discussed.