Iron nanoparticles prepared from natural ferrihydrite precursors: kinetics and properties
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Natural ferrihydrite was used as the precursors for the preparation of the nanocrystalline alpha-Fe powder using heat treatment in hydrogen atmosphere. Transformation temperatures were estimated from the temperature dependences of magnetic moment. Structure and phase composition of the precursors and the final powders were characterized by X-ray diffraction and Mössbauer spectroscopy. Magnetic properties were characterized according to hysteresis loop parameters. The kinetics of the transformation was described using Avrami relation applied on the data of the isothermal time dependence of magnetic moment measurements and subsequently the activation enthalpy of transformation was estimated using Arrhenius plots of their parameters. Comparison of the changes of activation enthalpies derived from a different temperature ranges indicates effects of different processes on formation of alpha-Fe nanoparticles.
KeywordsIron nanoparticles Ferrihydrite Reduction Hydrogen Magnetic moment Activation enthalpy
This work has been supported by the projects of the Ministry of Education of the Czech Republic (1M619895201) and Grant Agency of the Czech Republic (106/08/1440).
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