Synthesis and Characterization of Air-Stable Iron Nanocrystalline Particles Based on a Single-Step Swelling Process of Uniform Polystyrene Template Microspheres

Polystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. These template particles dispersed in aqueous solution have been used for entrapping Fe(CO) 5, by a single-step swelling process of methylene chloride emulsion droplets containing Fe(CO) 5, within these particles. The influence of different swelling parameters, such as the volume ratio [CH 2 Cl 2 /[Fe(CO) 5 ], on the size and size distribution of the swollen template particles was elucidated. Air-stable Fe/Fe 3 C nanocrystalline particles have been prepared by thermal decomposition of the Fe(CO) 5 swollen template particles at 600 °C in an inert atmosphere. Characterization of these air-stable Fe/Fe 3 C nanocrystalline particles has been accomplished by light microscopy, TEM, XRD, TGA, XPS, elemental analysis, and magnetic susceptibility measurements. These nanocrystalline particles have a core−shell structure where a coating of Fe 3 C and carbon protects the core body-centered cubic Fe from oxidation.