Structural, magnetic and Raman study of CoFe2O4@C core–shell nanoparticles

Abstract

The synthesis of CoFe2O4@C core–shell nanoparticles (NPs) was performed using a two-step method, including reverse micelle and thermo-chemical vapor deposition (TCVD). The water to surfactant molar ratio (W) was selected as 8 and 10. The diameter and crystallite size of the as-prepared CoFe2O4 NPs were lower than 10nm. Acetylene gas (C2H2) was used as a carbon precursor and coating was performed for 1, 2, and 3h. After coating, the core size was below 30nm and the thickness of the shell was below 8nm. The composition, structure, and morphology of the fabricated NPs were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and selected area diffraction (SAD) pattern. The vibration sample magnetometer (VSM) was also used to investigate the magnetic properties. It was found that carbon shell has a significant effect on the growth and magnetic properties of the core NPs. To study the coated carbon, micro-Raman spectroscopy was used and it was approved that the deposited carbon consists of graphite, MWCNTs and diamond-like carbon (DLC). By increasing the coating time, the ratio of the amorphous peak intensity to the ordered peak intensity IDIG was decreased, causing to an enhancement in the crystalline size of graphite.