Study On The Electrical Properties Of Carbon Nanofibers/polymer Nanocomposites

In this paper,the carbon nanofibers(CNFs)were synthesized by chemical vapor deposition method and surface-metallized by microwave assisted chemical nickel plating.Modified CNFs were introduced into polymer to form CNFs/polymer nanocomposites.Effect of CNFs incorporation and orientation on CNFs/polymer nanocomposites electrical properties was studied.The paper focuses on three areas:1.CNFs were synthesized by chemical vapor deposition method and surface-metallized by microwave assisted chemical nickel plating.Linear CNFs were synthesized by chemical vapor deposition method and successfully surface-metallized by simple and convenient microwave assisted chemical nickel plating.The results show that experiment conditions,such as pre-treatment processes and reaction time,have great effect on morphologies of CNFs and its surface coating.After microwave assisted chemical nickel plating,a uniform layer of 30 nm nickel particles was synthesized on CNFs surface.The number of nickel particles increase and the coating becomes thicker with the extension of reaction time.Because of the nickel coating,CNFs have certain magnetism and could successfully orient along the direction of magnetic field.2.Surface-metallized CNFs were introduced into polymer to form CNFs/polymer nanpcomposites.CNFs/polymer nanocomposite samples were successfully prepared by mechanical blending method.Magnetic field was applied on both ends of the mold when in high temperature,molding process can make CNFs orient to form anisotropy composites.CNFs have good dispersion,compatibility and interface bonding with EVA and LDPE.Clear cross-linked network structures of CNFs/LDPE nanocomposites can be observed after etching process.Not-oriented CNFs destroy the ordered structure of LDPE macromolecules and reduce the crystallinity of CNFs/LDPE nanocomposites.While oriented CNFs could improve the regularity and crystallinity of nanocomposites to some extent.3.Effect of CNFs incorporation and orientation on the electrical properties of CNFs/polymer nanocomposites was studied.At room temperature,the increasing of CNFs content makes the bulk resistance of oriented CNFs/LDPE nanocomposites reduce rapidly and then gradually become gentle.CNFs content 0.01-0.1% could cause the percolation phenemena of composites.Not-oriented CNFs can not change the transport of carriers in CNFs/LDPE insulation sample.While oriented CNFs can change the carriers transport and make the transport perpendicular to the thickness direction easier,this can effectively suppress carriers' injection along thickness direction and accumulation of space charge in medium.Semi-conductive layer can undermine the applied electric field along thickness direction,weaken the interface field between semi-conductive layer and insulation,reduce the amount of space charge injected by the cathode;not-oriented CNFs could gradually change the conductive mechanism of CNFs/LDPE semi-conductive layer,oriented CNFs can enhance the weakening effect of the semi-conductive layer to applied electric field,and reduce the amount of space charge injected into insulation.The add of oriented CNFs/LDPE semi-conductive layer can change the carrier transport and suppress the space charge injecting from the electrode to insulation successfully.CNFs incorporation concentration has great impact on the dielectric constant of CNFs/EVA,and it reaches the minimum when the content of CNFs is 0.5 wt%,while CNFs incorporation concentration has little effect on the dielectric loss.The orientation of CNFs can change the dielectric constant and would not increase the dielectric loss of the composites.