engleski

Synthesis of magnetite nanoparticles by the gamma-irradiation of water-in-oil microemulsion

Magnetite, (Fe3O4), has a great importance due to its unique electric and magnetic properties at room temperature with application in catalysis, medicine, ceramics processing, magnetic data storage, magnetic separation, protection against microwave radiation and many others. Magnetite can be produced by solid-state reaction or by “ wet-chemistry” methods. Alkaline precipitation from the solution of mixed Fe(II)/Fe(III) salts, oxidation of Fe(OH)2 gel, sol-gel, sonochemical, non-hydrolytic and microemulsion synthesis are often utilized. The method of water-in-oil microemulsion offers a very good control over particle size, morphology and phase composition of the final product. In the present work, a synthesis route that combines both a water-in-oil microemulsion and gamma-irradiation techniques was utilized in order to obtain magnetite nanoparticles. In the first experiment iron precursor was Fe(III) chloride and Fe(II) sulphate aqueous solution with the initial molar ratio of 3:2, while the precipitating agent was a strong organic alkali, tetramethylammonium hydroxide (TMAH). The ageing of microemulsion at room temperature without the  -irradiation produced only non-magnetic iron phase (poor crystalline goethite, a-FeOOH).  -irradiation of the same micro-emulsion at the dose 466 kGy produced almost pure nanosize particles of sub-stoichiometric magnetite (Fe3-xO4). At doses below 466 kGy a mixtureof goethite and magnetite was formed. In the second experiments the microemulsion containing only Fe3+ ions as iron precursor and TMAH as precipitate agent was gamma-irradiated at doses up to 400 kGy. The amount of magnetic phase (g-Fe2O3/Fe3-xO4) increased with the applied gamma-ray dose. This finding confirm that gamma-irradiation created strong reductive conditions in the microemulsion that was able to produce nanosize magnetite nanoparticles starting from pure Fe3+ iron precursor. The results of the present work showed new potentials in the synthesis of magnetic iron oxides nanoparticles by using gamma-irradiation.

micro-emulsion; gamma-irradiation; goethite; magnetite; Si-ferrihydrite

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