Preparation of carbon-encapsulated iron nanoparticles in high yield by DC arc discharge and their characterization

Carbon-encapsulated iron nanoparticles (CEINPs) were prepared by DC arc discharge under nitrogen atmosphere of high temperature. The products were characterized by transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectroscope, and X-ray photoelectron spectroscope (XPS), and their magnetic properties were measured by physical property measurement system (PPMS). The product BI, obtained from the anode I, contains the nanoparticles of iron and iron carbide, and carbon coating with imperfect and disordered layer structure. The product BII, obtained from the anode II, mainly consists of CEINPs, whose cores mainly consist of iron and iron carbide and shells contain about 3–7 graphitic layers. The iron contents in the products BI and BII are 44.8 and 82.6 wt.%, respectively. The products BI and BII have similar phase composition which includes carbon, iron, iron carbide, ferrous and ferric oxide, iron nitride, and carbon nitride. The saturation magnetization (Ms) of the products BI and BII are 29.35 and 88.66 emu/g and their coercivity (Hc) are 220 and 240 Oe, respectively. The total yields of all the products formed in the arc discharge chamber from anodes I and II, except for the cylinder-shaped deposits formed on the top of the cathode, are 25.8 and 22.3 wt.%, respectively. The possible process of formation of CEINPs is briefly discussed on the foundation of our results and other related published work. The results show that the homogeneous composition of anode is very important for the formation of CEINPs with good core–shell structure.

► CEINPs with core–shell structure and high Fe content were prepared in high yield by DC arc discharge.
► The anode II with a mass ratio of total iron to carbon 8:1 was used in DC arc discharge.
► The possible process of formation of CEINPs is briefly discussed.
► The uniformity of composition of anode is very important for the formation of CEINPs.
► The MEF and MMF of iron element may also play an important role in the formation of CEINPs.