Force and current in a contact gap between single highly resistive particles: experimental observations

Abstract

In case of electrical conduction through highly resistive dust layers, the generation of electrostatic adhesion force is strongly coupled to the mechanism of electrical (current) transport in the solid. High field strengths lead to a significant increase of the adhesive force. Here, more insight into the underlying mechanisms is given by experiments on the microscopic scale. An experimental arrangement is described which allows to study a particle pair subject to a strong electric field. Both the current and the force between the particles (150 μm) can be measured as a function of voltage and gap distance. The results show an extremely complex behaviour of the contact for the case of highly resistive particles. For current transport, both gas discharges and thermionic field emission are observed, depending on the width of the contact gap and the field strength. For both the force and the current across the gap, a strongly non-linear behaviour with pronounced time effects is observed.But additional problems are found with highly resistive dusts in electrostatic precipitators (ESPs). With dust resistivities beyond 10 11 Ω-cm, the precipitation process itself is disturbed by so called back corona (Masuda in [2,(3)(4)(5)). The current interpretation is that the current has to pass through the dust layer on the precipitation electrode. With high dust resistivity, a given current density will cause a strong voltage-drop across the dust layer and hence a strong electric field inside the dust layer. When a critical field strength is surpassed, an electric breakthrough occurs.

Formation of highly resistive SiO2 nanoparticle layers from the aerosol by electrostatic precipitation at 200 °C: observations on back corona and nanoparticle layer structure

“…Experimental investigations on current transport across narrow gaps between dielectric (glass) particles (Vora et al 2019) have shown that self-sustaining or self-amplifying gas discharges cannot develop (in air at ambient pressure) with pore sizes below about 2 µm. With dielectric materials, the supply of electrons is limited due to the high resistivity of the material.…”

“…Second, the deposited NPs might be seen as a dielectric material which nevertheless allows a certain amount of current transport by injected electrons or holes. Possibly the behavior of such materials can resemble to the behavior of conductive particles (Vora et al 2019). This allows the build-up of high fields which allow either the thermionic field emission of free electrons (on the cathode side only) or the development of microscopic, intermittent gas discharges.…”