Synthesis of Fe3O4/Fe nanocomposite powder from Fe2O3 and Fe powder by mechanosynthesis. Structural, thermal and magnetic characterisation

Mechanosynthesis was used for the obtaining of Fe3O4/Fe nanocomposite powder starting from Fe2O3 and Fe powders. Up to 120 min of milling, the powder is a composite material of Fe2O3/Fe. The Fe and Fe2O3 phases react after 120 min of milling leading to the formation of Fe3O4 phase. The amount of Fe3O4 progressively increases upon increasing the milling time up to 600 min. After 600 min of milling, the powder is a nanocomposite material of Fe3O4/Fe type with a mean crystallites size of 8 nm for Fe3O4 phase and 19 nm for Fe phase. The particles size and specific surface area are changing upon the formation of Fe2O3/Fe composite and during transformation of this into Fe3O4/Fe. The Fe3O4/Fe composite is stable up to a temperature of 540 °C, independent on milling time. The magnetisation decreases in the first stage of milling when the Fe2O3/Fe composite particles are formed. For further milling, as a result of the Fe3O4 phase formation, the magnetisation increases. The magnetisation increases continuously upon increasing the milling time from 120 up to 600 min as a result of the progressive formation of Fe3O4. The magnetisation of Fe3O4/Fe nanocomposite is reduced as compared to the theoretical one due to the presence of a residual Fe2O3 phase and surface defects.