Study On The Semiconducive Composite Of CNFS/EVA Used In Hvdc Cable

High-voltage direct current transmission(HVDC)is studied to deal with the long-distance power transmission. And the advanced insulating materials have promoted the development of HVDC. In this paper, the carbon nanofibers(CNFs)doped in polymer were dispersed in orientation,and the dielectric properties were studied. The oriented-dispersion of CNFs aimed to be applied in HVDC cable.Surface metallization of CNFs was obtained by Ni deposition. The characterizations show that Ni coating is about 8nm with small amount of Ni attached to the surface.As the concentration of NiCl₂ rises, Ni nanoparticles adhesion on the surface increases. And dispersion methods also influence the surface morphology of CNFs. Compared with the mechanical stirring, ultrasonic dispersion could make the solution more homogeneous, and leads to less Ni attachment.Oriented CNFs have been observed by microscope after EVA is composited with modified CNFs under the magnetic field. It is known from the analysis of dielectric spectra of CNFs/EVA that the dielectric properties have changed compared with un-oriented CNFs/EVA.When CNFs concentration was 0.1wt% and 0.5wt%, relative permittivity of oriented CNFs/EVA is smaller than that of un-oriented CNFs/EVA. When the concentration rises to 1.0wt% and 5.0wt%, results are completely opposite. The dissipation factor of oriented CNFs/EVA is greater at low frequency and smaller at high frequency than un-oriented CNFs/EVA as CNFs concentration is 1.0wt% and 5.0wt%.