Redox synthesis of magnetite powder under mixing-grinding of metallic iron and hydrated iron oxide

Redox synthesis of magnetite powder from metallic iron and FeO(OH) under mixing-grinding with the assistance of H2O2 as an oxidizing reagent has been proposed. Deformability of the metal–oxide system induces the kneading of am-FeO(OH) into metallic iron to activate, while the iron is oxidized to Fe(OH)2 and/or FeO by H2O2 contained in the grinding liquid (acetone). Only the reaction product, γ-Fe3O4, is obtained. The adhesivity of the powder system due to iron reduces with the progress in synthesis reaction forming non-deformable magnetite powder to result in its dispersion into acetone. The primary particle size of the γ-Fe3O4 powders formed is less than 100 nm. The saturation magnetization of the synthesized γ-Fe3O4 is 9.24×10−5 Wb m g−1, which is about 90% of the commercially available fine γ-Fe3O4 powders with needle-like shapes.