NTC effect and the adjustment in nano Ni-C/ER composites

Epoxy resin (ER) composites filled with aligned carbon coated nickel (Ni-C) nanoparticle were prepared by use of magnetic field assisted curing process，and the electrical properties were tested. The higher the content of nanoparticles，the greater the magnitude of the magnetic field applied，the lower the resistivity of the composites obtained. I-U characteristic of the composites is tested nonlinear，indicating that the electrical conduction depends on the tunneling transport of electron cross the adjacent Ni-C nanoparticles. The resistivity of the composites exhibits negative temperature coefficient (NTC) effect above the room temperature，and can be adjusted by varying the filler content and the magnitude of magnetic field. A modified quantum tunneling model was developed to understand the origin of NTC effect in the composites， which shows that the NTC effect is attributed to the dominant thermal activation tunneling of electron，and to the low thermal expansivity of the epoxy resin matrix.