Thermionic return currents in contact electrification

Abstract

It is demonstrated that the contact electrification process is generally a nonequilibrium phenomenon. The electrochemical potential is considered for the case of ion transfer between insulators. It is shown that the thermionic return currents are significantly dependent on the physical separation and the dielectric constants of the materials. A nonequilibrium chemical kinetics formulation is presented in which dielectric constants and surface separation rates are explicitly accounted for. The predictions of the theory are shown to correlate with electrification experiments performed on various glass, lead zirconate, and aluminum oxide beads rolled in an aluminum oxide coated rotating cylinder.