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.