An Easy One-step Route to Carbon-encapsulated Magnetic Nanoparticles

An easy one-step fast route that utilizes simple and low-cost starting reactants for the synthesis of carbon-encapsulated magnetic nanoparticles (CEMNPs) is presented. The synthesis process is based on the thermolysis of a NaN3/C6Cl6 mixture with the addition of a pure (elemental) metal to be encapsulated (Fe, Co and Ni). This autothermal process generates a few grams of product in a single run and is completed within 1-2 seconds. The product consists of CEMNPs with diameters between 30 and 80nm and amorphous carbon nanoparticles. X-ray diffraction (XRD) revealed that the encapsulated particles are crystalline and possess low lattice strain (less than 1%). The crystallinity of the carbon phase was evaluated by XRD, Raman spectroscopy and by investigating its resistance to thermal oxidation. Magnetic measurements showed that the as-obtained CEMNPs have soft ferromagnetic properties with coercive forces ranging between 49 and 224 Gs. In addition, CEMNPs can be obtained at temperatures below the vaporization point of the metal in question.