Nanocrystalline/Nanosized Fe3O4 Powder Obtained by Mechanosynthesis

Nanocrystalline/nanosized magnetite - Fe3O4powder was obtained by mechanical milling of well crystallized magnetite obtained by ceramic method starting from stoichiometric mixture of commercial hematite - Fe2O3and iron - Fe powders. The mean crystallites size of the magnetite is decreasing upon increasing the milling time down to 6 nm after 240 minutes of milling. After 30 minutes of milling an undesired hematite phase is formed in the material. The amount of this phase increases upon increasing the milling time. In the early stage of milling (up to 30 minutes) the existence of nanometric particles (mean size below 100 nm) is noticed. The d50median diameter decreases first (up to 5 minutes of milling) and after that, an increase follows for milling times up to 120 minutes. Saturation magnetization decreases upon increasing the milling time and is more difficult to saturate. X-ray diffraction, laser particle size analysis and magnetic measurements have been used for powder characterization.