On the electrical conductivity of particulate composites

Two new equations are developed for effective electrical conductivity of concentrated particulate composites using a differential scheme along with the solution of an infinitely dilute dispersion of particles in a continuous matrix. The proposed equations are evaluated using 16 sets of experimental data on the electrical conductivity of two-phase particulate systems. The following model developed in the paper describes the experimental data very well: (sigma/sigma(m))(1/3) (sigma(d)-sigma(m))/(sigma(d)-sigma)=(1-phi/phi(m))(-alpha phi m) where sigma,sigma(m) and sigma(d) are electrical conductivities of composite, matrix, and dispersed phase (filler) respectively, phi is volume fraction of filler, phi(m) is the maximum packing volume fraction of filler, and alpha is a constant of the order of unity. In the special case of alpha = 1 and phi(m) = 1, this model reduces to the well-known Bruggeman equation for the electrical conductivity of two-phase particulate systems. The predictions of the proposed model are significantly different from the predictions of the existing general effective media (GEM) model.