Nanocrystalline/nanosized Fe3O4 obtained by a combined route ceramic-mechanical milling. Effect of milling on the chemical composition, formation of phases and powder characteristics

• Easy accessible precursors have been used for magnetite synthesis.
• Short milling times are favourable for obtaining nanocrystalline/nanosized Fe3O4.
• Iron contamination occurs upon mechanical milling processes.
• Reduction of magnetite with iron provided by contamination occurs.

Magnetite (Fe3O4) has been synthesised via a new combined route, ceramic method and mechanical milling, starting from a stoichiometric mixture of the easily accessible Fe and Fe2O3 precursors. In the first step, well crystallised magnetite has been obtained by heat treatment of the precursor homogenised mixture at lower temperature as compared to the classical route for synthesis of ferrites. In the second step, the as obtained low cost Fe3O4 has been mechanically milled. The powders have been characterised by X-ray diffraction (XRD), magnetic measurements M = f(H), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), laser particle size analyser and differential scanning calorimetry (DSC). The nanocrystalline/nanosized powder is obtained after only 5 min of milling. A powder contamination with Fe occurs during milling and this leads to the formation of a wüstite-FeO phase. The formation of the FeO phase leads to the lattice strain release. The magnetisation decreases upon increasing the milling time due to the formation of the wüstite and structural disorder.

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