NiO@C and Ni@C Nanoparticles: Synthesis, Characterization and Magnetic Properties

Carbon-coated nickel oxide nanoparticles (NiO@C) were synthesized by near-critical hydrothermal method using starch and nickel nitrate as precursors. Also,carbon-coated Ni nanoparticles (Ni@C) were obtained by annealing NiOUC nanoparticles in hydrogen atmosphere. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, simultaneous thermal analysis (STA) and physical property measurement system (PPMS). The average sizes of the NiO and Ni nanoparticles were 18 nm and 15 nm according to the XRD analysis, respectively. Raman spectroscopy and thermogravimetric analysis demonstrated that the carbon shells of NiOUC and Ni@C nanoparticles were composed of amorphous and partially graphitized carbon. The formation mechanism of NiOUC and Ni@C nanoparticles was briefly discussed. The N@C nanoparticles have enhanced coercive force than bulk nickel, and their coercive force has shown a linear dependence on the square root of temperature.