Synthesis and characterization of carbon-encapsulated magnetite, martensite and iron nanoparticles by high-energy ball milling method

Carbon-encapsulated magnetic nanoparticles were synthesized by high energy ball milling of dopamine and ferric nitrate. Different kinds of magnetic nanoparticles can be prepared by simply adjusting the relative amount of dopamine. With the increase of the dopamine content, carbon-encapsulated magnetite, martensite and iron nanoparticles can be synthesized sequentially. The structure, morphology and magnetic properties of the carbonen-capsulated magnetic nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and vibrating sample magnetometer. The sizes of the carbonen-capsulated magnetic nanoparticles are in ten-nanometer scale and have narrow distributions. The carbon encapulation is amorphous. And the carbon content in the carbon-encapsulated magnetic nanoparticles increase with the relative amount of dopamine used in high energy ball milling. The synthetic mechanism of the carbonen-capsulated magnetic nanoparticles is discussed. The high local effective temperature during the high energy ball milling process is thought to be crucial for the carbonization of dopamine. And the local effective temperature also promotes the reduction of Fe3+ ions by dopamine and the formation of the magnetic nanoparticles.