NANOSTRUCTURED IRON OXIDE POWDERS BY MICROWAVE ASSISTED SYNTHESIS

Abstract

A range of nanostructured oxides with excellent properties is used in technology and science for applications in several fields: catalysis, gas detection, biomedical applications. The most studied forms of oxides are hematite, maghemite and magnetite. In this study, microwave-assisted hydrolytic synthesis and microwave-assisted coprecipitation synthesis are described for the preparation of undoped and doped iron oxide powders using iron (III) chloride (FeCl3), potassium chloride (KCl) as precursors and sodium hydroxide (NaOH) solution as a hydrolysis agent. Microwave-assisted hydrolysis was performed at different concentrations of FeCl3 precursor: 0.1 M, 0.4 M, 0.7 M to which a constant concentration of hydrolysis agent was added, and the synthesis to obtain potassium-doped powders consisted of co-precipitation of 0.1M FeCl3 and 0.025M KCl precursor solutions in the presence of 2M NaOH hydrolysis agent. The developed powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The novelty is the use of potassium as a doping element for iron oxide, for potential application as catalyst. Hematite doped with 5% K was obtained by microwave-assisted coprecipitation synthesis. The presence of K was evidenced by EDS, while XRD spectra indicate successful doping of iron oxide with potassium, either interstitially or by substitution. By microwave synthesis, an increase in particle size was observed with increasing calcination temperature. The formation of the crystalline hematite phase was not obtained in the microwave heating process but following calcination of the powder