Effect of Carbon Shell on the Structural and Magnetic Properties of Fe3O4 Superparamagnetic Nanoparticles

Carbon-encapsulated iron oxides (Fe3O4/C) with a core/shell structure have been successfully synthesized by using a simple two-step hydrothermal method at 180 C-a similar to. Fe3O4 core nanoparticles were prepared by coprecipitation under two conditions. Synthesized nanoparticles were characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. TEM images and FTIR results prove that carbon coated iron oxide is formed and the estimated size for most of them is below 11 nm, which was consistent with the XRD result. The Williamson-Hall (W-H) method has been used to calculate crystallite sizes and lattice strain based on the peak broadening of the Fe3O4 and Fe3O4/C nanoparticles. The results of VSM imply that the Fe3O4 core and core-shell nanoparticles are superparamagnetic. The saturation magnetization of Fe3O4 and Fe3O4/C are 49 emu/gr and 40 emu/gr, respectively. The magnetic behaviors reveal that the amorphous carbon shell can decrease the saturation magnetization of Fe3O4 nanoparticles due to core-shell interface effects and shielding.