Preparation of carbon-coated Co and Ni nanocrystallites by a modified AC arc discharge method

A modified AC arc discharge method was used to prepare carbon-coated cobalt and nickel nanocrystallites under He atmosphere. The metal content of the magnetic nanomaterials were remarkably enhanced by increasing metal loading ratio and modifying experimental apparatus. The powder was separated from the soot by magnetic separation and acid (HCl) treatment. Structure and morphology were examined by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The metal content was determined by thermogravimetric analysis (TG). The magnetic properties of the powder were measured by a vibrating sample magnetometer (VSM). The size of the wrapped metal particles was between 10 and 100 nm. XRD profiles showed peaks associated with major peaks of graphite and single phase of fcc β-Co and cubic Ni with no evidence of metal carbides. With the Co metal content ranging from 28.8 to 57.5 wt.%, the corresponding Bs ranged from 210.6 to 758.2 G. The Bs of the carbon-coated Ni powder ranged from 90.7 to 205.0 G while the Ni metal content ranged from 34.6 to 64.5 wt.%.