Synthesis of ferromagnetic core-shell nanofibers

A rapid, solvent-less RAPET (reactions under autogenic pressure at elevated temperature) approach is described for the fabrication of 1-D core-shell nanostructures. Ferromagnetic FeS and FeSe nanomaterials are covered in situ in a multiwalled carbon shell by the one-step thermolysis of Fe(CO)₅ in the presence of either S or Se powders in a closed reactor at 700°C for 30 min under autogenic pressure in an inert atmosphere. SEM measurements revealed the 1-D morphology of FeS or FeSe wires coated with carbon as having a 80-100 nm diameter with a micrometer length. XRD measurements were consistent with a hexagonal phase of FeS and a tetragonal crystal structure of FeSe. HR-TEM images confirmed the 1-D core-shell morphologies of FeS or FeSe with carbon (MX/C; MX = metal chalcogenide) as the shell. The ferromagnetic characteristics of these MX/C samples were investigated using a vibrating sample magnetometer. Nitrogen gas adsorption on the surface of MX/C nanostructures was determined by BET surface area analysis. A plausible mechanism for the formation of magnetic cores (FeS or FeSe) with a carbon shell is suggested.