Influence of metal ions on the structure of poorly crystallized iron oxide rusts

Abstract The poorly crystallized steel rusts have been prepared by hydrolysis of aqueous solutions dissolving Fe(III) and different metal ions such as Ti(IV), Cr(III), Ni(II) and Cu(II) at varied atomic ratios in metal/(Fe+metal). The precipitates formed by the hydrolysis were frozen with liquid N 2 to inhibit crystallization and particle growth. The rusts produced were poorly crystalline and nanosized particles with sizes of 4–10 nm and the rust formed without adding metal ions was assigned to ferrihydrite. The crystallite size decreased from 1.1 to 0.7 nm with increasing the added metal ions. It was shown by extended X-ray fine structure and Mossbauer spectroscopy that the short-range structure of poorly crystalline rusts was disturbed by adding Ti(IV).