Characteristic of the zinc- and nickel-containing iron-oxygen nanophases formed on the steel surface under the rotation-corrosion dispergation conditions

Abstract

The nanosized powders formed on the steel surface contacting with zinc and nickel inorganic water salt solutions under the rotation-corrosion dispergation (RCD) conditions have been studied using an X-ray diffraction method, thermal analytical measurements (TG / DTG, DTA) and scanning electron microscopy. It was shown that the formation of a single mineral phase of a non-stoichiometric spinel ferrite when zinc and nickel nitrate solutions were used as the dispersion medium, but in the presence of chloride-containing salts three mineral phases (spinel ferrite, lepidocrocite, and goethite) were determined in the phase composition of the surface powders. When sulfate solutions were chosen as the dispersion medium the mixed hydroxysulfate layered double hydroxides (LDHs) simultaneously appeared among other components of the powders. Due to exchange of cations Fe(II) and other 3d-metals between the disperse phase and dispersion medium the mixed LDH structures achieved stability against further oxidation and phase transformation. Hence, the presence of mixed LDHs in the phase composition of the powders significantly complicates the obtaining of monomineral phases of spinel ferrites or iron oxides when the RCD method is applied.