Anisotropic electrical conductivity of lotus-type porous nickel

We studied the anisotropic electrical conductivity of lotus-type porous nickel, with cylindrical pores aligned unidirectionally. We measured the electrical conductivities in the directions parallel and perpendicular to the longitudinal axis of the pore with four-probe method. The electrical conductivity of lotus nickel shows the anisotropy that reflects the anisotropic porous structure and can be summarized with a well-known power-law formula (Archie's law); the conductivity in the direction parallel to the pore decreases linearly with increase in porosity, and that in the perpendicular direction decreases steeply with porosity increase, in agreement with Archie's power-law formula. Furthermore, we constructed the effective-mean-field (EMF) theory to predict the effective electrical conductivity of composites. The electrical conductivity of lotus nickel, evaluated by this theory, is consistent with measurement data, and this EMF theory can fully simulate Archie's power-law formula.