A Non-Alkoxide Sol-Gel Method for the Preparation of Magnetite (Fe3O4) Nanoparticles

Magnetite (Fe3O4) nanoparticles in the interval of 9∼12nm have been synthesized by an non-alkoxide sol-gel method. Through this simple technique, sol-gel materials were prepared from ethanolic solutions of metal chlorides without the need for alkoxides, polymeric gel agents, or elaborate reaction schemes. The gel formation has been studied, and the research shows that gel formation appears to be driven primarily by the formation of an Fe(III)-based network which incorporates Fe(II) into its nanoscale solid domains. The research of the annealing process indicates that magnetite (Fe3O4) nanoparticles can be obtained by annealing only under vacuum, but not in air. Future, Fe3O4 can be oxidized to Fe2O3, as evidenced by XRD, and VSM. The phase structures, morphologies, and particle sizes of Fe3O4 nanoparticles were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The results indicate that magnetite (Fe3O4) nanoparticles are homogeneous and have near-spherical shape with a narrow distribution in particle size. Finally, an investigation of the possible mechanism of Fe3O4 nanoparticles formation was performed. Both TG-DTA and X-ray Diffraction (XRD) studies suggest that the reaction of the decomposition of the precursor under vacuum conditions leads to Fe3O4 nanoparticles, while the precursors in air atmosphere is directly oxidized to gamma iron oxide. In addition, this approach may suggest a general route to produce complex multicomponent metal oxide in which the nanoscale oxide is stabilized and spatially distributed.