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 Fe 3 O 4 /Fe nanocomposite powder starting from Fe 2 O 3 and Fe powders. Up to 120 min of milling, the powder is a composite material of Fe 2 O 3 /Fe. The Fe and Fe 2 O 3 phases react after 120 min of milling leading to the formation of Fe 3 O 4 phase. The amount of Fe 3 O 4 progressively increases upon increasing the milling time up to 600 min. After 600 min of milling, the powder is a nanocomposite material of Fe 3 O 4 /Fe type with a mean crystallites size of 8 nm for Fe 3 O 4 phase and 19 nm for Fe phase. The particles size and specific surface area are changing upon the formation of Fe 2 O 3 /Fe composite and during transformation of this into Fe 3 O 4 /Fe. The Fe 3 O 4 /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 Fe 2 O 3 /Fe composite particles are formed. For further milling, as a result of the Fe 3 O 4 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 Fe 3 O 4 . The magnetisation of Fe 3 O 4 /Fe nanocomposite is reduced as compared to the theoretical one due to the presence of a residual Fe 2 O 3 phase and surface defects.