Nonlinear DC response in high-density polyethylene/graphite nanosheets composites

In this paper, the nonlinear conduction behavior of high-density polyethylene (HDPE)/graphite nanosheets composites above the percolation threshold was investigated. For some samples, the I–V curves are smooth and the nonlinear term is cubic, rather than quadratic. However, for other samples, the onset of nonlinearity is accompanied by the appearance of steps in I–V curves. Furthermore, the crossover current Ic for two types of curves at which nonlinearity occurs scales with the linear conductance 1 as I c ∼ x 1, with x ≈ 1.28. And the second-order conductance, 2, also scales with 1 as 2 ∼ y 1, with y ≈ 1.00. Two classical models, NLRRN (nonlinear random resistor network) and DRRN (dynamic random resistor network), cannot fully explain our experimental results. It is likely that a combination of these two models may account for the nonlinear feature better. C 2006 Springer Science + Business Media, Inc.