Synthesis and magnetic properties of Fe3C-C core-shell nanoparticles.

Fe3C-C core-shell nanoparticles were fabricated on a large scale by metal-organic chemical vapor deposition at 700 °C with ferric acetylacetonate as the precursor. Analysis results of x-ray diffraction, transmission electron microscope and Raman spectroscope showed that the Fe3C cores with an average diameter of ∼35 nm were capsulated by the graphite-like C layers with the thickness of 2-5 nm. The comparative experiments revealed that considerable Fe3O4-Fe3C core-shell nanoparticles and C nanotubes were generated simultaneously at 600 and 800 °C, respectively. A formation mechanism was proposed for the as-synthesized core-shell nanostructures, based on the temperature-dependent catalytic activity of Fe3C nanoclusters and the coalescence process of Fe3C-C nanoclusters. The Fe3C-C core-shell nanoparticles exhibited a saturation magnetization of 23.6 emu g(-1) and a coercivity of 550 Oe at room temperature.