Low-temperature, carbon-free reduction of iron oxide

We report here that iron oxide can be reduced completely to elemental iron, through a carbon-free and low-temperature reaction. Nanoparticles of Fe₂O₃ are completely reduced, resulting in the formation of nanoparticles of Fe, on the surfaces of Si or Ge, at ∼740 and ∼440 °C respectively. We show that this phenomenon is due to the oxygen atoms changing the bonding partner from Fe to Si or Ge, followed by the desorption of the respective monoxides. Therefore, the reduction temperature is dictated by the desorption temperatures of SiO or GeO molecules. The nanoparticles thus formed are magnetic and are of uniform size and shape. On graphite surfaces, however, Fe₂O₃ retains the original stoichiometry even after annealing at higher temperatures.