Electric properties of Ni-C and Co-C core–shell nanoparticles in polymer matrix

A number of the nanocarbon-metal Nix-C and Co50-C core–shell structures were obtained from phenol-formaldehyde resin as a carbon precursor using a mechanochemical method and pyrolysis at 1034 °K. The morphology of the obtained core–shell structures was characterized by scanning electron microscopy. The magnetic hysteresis loops of Ni25-C and Co50-C core–shell structures were investigated by using a vibrating sample magnetometer. The work presents the results of investigations of electrical resistivity of nanocarbon-metal Nix-C and Co50-C core–shell structures embedded in polyvinyl acetate (PVA). Electrophysical properties of the composite materials (CMs) have been studied in a wide temperature range: 77–293 K. It was found that morphology and composition (the content of the metal phase and its relation to the carbon phase) of Nix-C core–shell structures embedded in PVA influences the value of electrical resistivity, its temperature dependence ρ(Т) and δρ/ρ parameter of composites. The materials with the higher content of core–shell structures (Ni75-C and Co50-C) are characterized by the lower electrical resistivity, while the materials with the significant content of separate carbon phase in the form of nanotubes are characterized by the weaker ρ(Т) dependence.