Synthesis and characterization of iron, iron oxide and iron carbide nanostructures

• Thermal decomposition at 300 °C of a mixture of PVP and Fe(CO)5 leads to the formation of magnetic nanoparticles of different phases and shapes.
• Changing the annealing time period and the ([PVP]/[Fe(CO)5]) (w/v) ratio allowed control of the nanoparticles different properties.
• H2 reduction of the former magnetic nanoparticles leads to the formation of almost pure Fe nanospheres phase.

Magnetic iron oxide (Fe3O4 and γ-Fe2O3) and iron carbide (Fe3C) nanoparticles of different geometrical shapes: cubes, spheres, rods and plates, have been prepared by thermal decomposition of a mixture containing the metal precursor Fe(CO)5 and the stabilizer polyvinylpyrrolidone (PVP) at 300 °C in a sealed cell under inert atmosphere. The thermal decomposition process was performed for 4 or 24 h at ([PVP]/[Fe(CO)5]) (w/v) ratio of 1:1 or 1:5. Elemental iron nanospheres embedded within a mixture of amorphous and graphitic carbon coating were obtained by hydrogen reduction of the prepared iron oxide and iron carbide nanoparticles at 450 °C. The formation of the graphitic carbon phase at such a low temperature is unique and probably obtained by catalysis of the elemental iron nanoparticles. Changing the annealing time period and the ([PVP]/[Fe(CO)5]) ratio allowed control of the composition, size, size distribution, crystallinity, geometrical shape and magnetic properties of the different magnetic nanoparticles.