Large scale continuous synthesis of carbon-encapsulated magnetic nanoparticles

Fe, Fe3C and NdC2 nanoparticles, encapsulated within carbon cages, were continuously produced during the induction thermal plasma processing of Fe14Nd2B, in the presence of methane or acetylene. The product morphology was studied by means of SEM. Further structural details were obtained from TEM, HRTEM, Raman spectroscopy and x-ray powder diffraction studies. The so-produced nanostructures have core-shell structure, with inner cavity diameters varying between 10 and 30 nm. The carbon coatings were composed of between 5 and 25 graphene layers. The carbon cages were built from sp(2) carbon atoms, which protected the encapsulated nanoparticles from both oxidation and agglomeration. The plasma generated products were ferromagnetic, with maximum values of coercivity field of 600 G s, and saturation magnetization values of up to 40 emu g(-1).