The percolation exponents for electrical and thermal conductivities and the permittivity and permeability of binary composites

A comprehensive review and analysis of experimental measurements of the conductivity sigma(m) (phi), the thermal conductivity mu(m) (phi) and the magnetic permeability lambda(m) (phi) in various composites/mixtures is presented. The Two Exponent Phenomenological Equation TEPPE is a function of the volume fraction (phi) which has five parameters, including the percolation exponent t, is used to analyse the results. In bonded/contiguous samples the conducting and non-conducting materials are self-contiguous. Here t is found to be about 2. In granular composites the high component grains have angular structures, which give intergranular point contacts. Here conductivity measurements give a t from about 2 to 5, while the permeability and thermal conductivity measurements give t values less than 1. Hence, experimental data can be used to obtain information about the structure and bonding of composites/mixtures. A possible qualitative explanation for the observation of the two values of t, in the cases of electrical conductivity and of permeability measurements, respectively, is proposed.

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This study provides a comprehensive review and analysis of experimental measurements of conductivity, thermal conductivity, and magnetic permeability in various composites and mixtures. The experimental data can be used to obtain information about the structure and bonding of composites/mixtures, and a possible qualitative explanation is proposed for observing two values of t in electrical conductivity and permeability measurements.