Solid-state synthesis of α-Fe and iron carbide nanoparticles by thermal treatment of amorphous Fe2O3.

Thermal treatment of amorphous iron(III) oxide nanopowder (2–3 nm) in various atmospheres is presented as a simple route towards α-Fe and iron carbides nanoparticles. The chemical composition and size of nanoparticles can be controlled using the reaction temperature, annealing time and atmosphere (hydrogen, carbon monoxide, hydrocarbons). To monitor the structure, phase composition, size, morphology and magnetic properties of nanoparticles, XRD, Mössbauer spectroscopy, and magnetic measurements were carried out. The measurements of temperature dependence of magnetic moment yield information on the critical temperatures of magnetic and phase transformations. Application of hydrogen atmosphere results in the formation of α-Fe, while iron carbides (∼Fe₃C) can be obtained in atmospheres of carbon monoxide or hydrocarbons. [ABSTRACT FROM AUTHOR]