Nonlinear electrical conduction in percolating systems induced by internal field emission

We identify the mechanism of internal field emission responsible for nonlinear electrical conduction behavior of percolating systems. The nonlinear conduction induced by internal field emission, in combination with linear conduction contributed by a conducting network, are responsible for the whole electrical conduction process in the percolating system. Based on these two types of conduction, we put forward an elegant electrical model, demonstrating the system exposed to an external field behaves as two resistors in parallel. Moreover, we also analyze the crossover current density where significant electrical nonlinearity occurs. Although our conclusion is based on high density polyethylene (HDPE)–carbon nanofiber (CNF) system, it can be extended to other systems such as HDPE–graphite, polyvinylidene fluoride (PVDF)–CNF, and PVDF–graphite.

Research highlights
► Percolating high density polyethylene (HDPE)-carbon nanofiber (CNF) composite.
► The electrical behavior under an applied field (E) is described by linear and nonlinear conduction.
► Nonlinear conduction in percolating HDPE-CNF composite results from internal field emission.
► The current density (j) is j(E) = σ0E + AEnexp(−B/E) where A, B are constants and n an exponent.
► A model is proposed for percolating composite system, consisting of two resistors in parallel.