Electromechanics of Precipitated Particulate Layers

A comprehensive analysis is given of the electromechanics of a precipitated particulate layer, modeled as a regular array of resistive spheres, which allows for both volume and surface conduction and takes account of self-compression of the layer. Formulas are derived for the contact radius, the electric field distribution, the compressive stress in the layer, and the apparent electrical resistivity. For typical precipitator conditions the electrical clamping force is found to be remarkably large(10-100 g wt/cm2), and the layer resistivity is found to decrease with increasing current and field as found experimentally. The theory is extended to predict conditions for the onset of back discharge, in the form of intermittent microsparks in the contact regions. Preliminary measurements using glass beads in a resistivity cell show general agreement with the theoretical results.