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Thermally induced phase transitions in Fe/Fe3O4 mixed nanopowders

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Ovidiu Crisan, Radu Nicula, Alina-Daniela Crisan and Eberhard Burkel

Editorial: Institute of Physics Publishing, Journal of Physics D: Applied Physics, p.submitted, 2007.

Rezumat:

Fe / Fe3O4 (magnetite) powders obtained by ball milling at room temperature, undergo an incomplete redox reaction with formation of FeO. This reaction is favored due to the high energy developed during the milling and alloying. Concurrential effects of the milling, such as grain refinement down to the nanometric scale lead at the end of the milling processes to a mixed multiphased nanopowder, with a homogeneous dispersion of Fe and Fe oxide grains. Such ferromagnetic – antiferromagnetic systems are extensively studied due to their exchange bias properties, extremely useful in technological applications. We study the phase transformation that leads to a multiphased metal / oxide microstructure with an energy-dispersive in-situ X-ray diffraction experiment using the synchrotron radiation. This study allows direct collection of X-ray spectra after few minutes exposure, at selected temperatures, ranging between 20°C and 1000°C.

Cuvinte cheie: mixed nanopowders, ball milling, redox solid state reaction