Microwave hydrothermal synthesis of maghemite nano-particles as a precursor of magnetic fluids

S. Cuvanova , M. Lovas , M. Matik , M. Vaclavikova

Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, SK-043 53 Kosice, Slovakia

Abstract
The objective of this study is to explore the microwave hydrothermal (MH) synthesis of γ-Fe₂O₃ powders and to characterize the products obtained by microwave hydrothermal processing. Maghemite particles were prepared by co-precipitation of Fe(III) and Fe(II) in the presence of NH₄OH. The suspension was being irradiated for 30 minutes by MW irradiation at the frequency 2.45 GHz (500 W). Finally, the suspension was decantated using deionized water to approximately pH 6.5 and dried. In order to compare the conventional method and the MH method, the same co-precipitation technique was used to prepare a maghemite sample at room temperature. The clear samples were then collected for further analysis. Mössbauer measurements were performed by transmission geometry using a microcomputer-controlled spectrometer in a constant acceleration mode using a ⁵⁷Co/Rh γ-ray source. Surface morphology and particle size were characterized by scanning electron microscopy (SEM). The presence of maghemite particles was confirmed in the spectrum of a sample prepared in a microwave reactor and at room temperature as well. Tables 2, Figs 4, Refs 3.