Effect of milling time on the synthesis of magnetite nanoparticles by wet milling

In this study, nanosize magnetite (Fe3O4) particles have been prepared directly from metallic iron (Fe) powder within distilled water (H2O) by using a planetary ball mill, and the effect of milling time has been investigated. According to Rietveld refinement result obtained from X-ray diffraction (XRD) analyses, the amount of Fe decreases from 98.2% to 0.0%, and it is transformed into Fe3O4, from 1.8% to 100.0%, with the increasing milling time from 1 to 48 h. Due to similar crystal structure of the magnetite and maghemite (γ-Fe2O3), FTIR and Raman spectroscopies as well as a chemical analysis method was used to verify the magnetite structure. FTIR spectra have clearly revealed absorption peaks around 628, 581 and 443 cm−1, which are in good agreement with the characteristic absorption peaks of Fe3O4. In addition Raman analysis verified the formation of magnetite phase with a clear main band peak at 671 cm−1. Chemical analyses have shown that the total amount of Fe in the milled sample for 48 h is 73.04%, which contains 24.10% Fe2+ and 49.34% Fe3+. These results are consistent with the theoretically estimated values of the magnetite. It has been observed that the saturation magnetization decreased from 146.02 to 63.68 emu/g with increasing milling time due to the formation of the ferrimagnetic magnetite phase.