▎ 摘　　要

Highly aligned graphene-polymer nanocomposite foams are of great interest due to their excellent electrical conductivity and dielectric permittivity along the aligned direction while maintaining flexibility and lightweight, but no theory seems to exist to quantify their frequency-dependent phenomena at present. In this work, we develop a two-scale effective-medium theory under the complex setting to study the porosity-dependent percolation threshold and the frequency-dependent electrical properties for such nanocomposite foams over a wide range of alternating current (AC) frequency. The key features of the theory include the maximum distribution angle, graphene volume concentration, percolation threshold, porosity, Maxwell-Wagner-Sillars polarization, electronic tunneling, and the frequency-dependent Dyre electron hopping and Debye dielectric relaxation at the interface. We highlight the developed theory with a direct comparison to experimental data of highly aligned graphene/epoxy nanocomposite foam over the frequency range from 10(2) to 10(6) Hz. It shows that the graphene percolation threshold decreases markedly with respect to porosity. In addition, the effective electrical conductivity and dielectric permittivity of highly aligned graphene-polymer nanocomposite foam, including the in-plane and out-of-plane ones, increase and decrease with respect to AC frequency, respectively.