Structure and magnetic properties of nanoparticles encapsulated in carbon shells

Ni2Y and Nd-Fe-Nb-B catalysts were used for the processing of nanoparticles by arc discharge between graphite electrodes. The products were collected from the cathode (deposit and collar) and reactor walls (soot). The ferromagnetic nanoparticles have size in the range of 10-50 nm and are encapsulated in carbon shells. The chemical composition, structure and magnetic properties of the nanoparticles have been studied. For the Ni2Y catalyst we found that the arc discharge results in decomposition of the intermetallic Ni2Y phase and formation of Ni nanoparticles encapsulated in carbon shells in the collar and soot, whereas yttrium oxide was found in the deposit. For the Nd-Fe-Nb-B catalysts the magnetic properties depend on the collection place and erosion rate. Fe and Fe-Nd-Nb nanoparticles were found in the soot and deposit, respectively.