Experimental Investigation of Electrostatic Effects in the Adhesion of Dry Dusts

It is supposed that in two-stage electrostatic precipitation, electrostatic forces arising from contact potential differences are important in the adhesion of talc, silica, flyash, and similar materials. ThiS idea is based on observation indicating that these particles have surfaces with different work functions. If these electrostatic forces are dominant, a rough correlation should exist between adhesive force and charge transfer during a contact, and the magnitude of the charge transferred should be sufficient to account for the measured forces. Described are the design and construction of an apparatus to measure the adhesive force between small particles and the charge transferred during that contact, and the results of those measurements. Adhesive forces of 1O-9 N and charges of 11 electrons can be measured. Adhesive forces for a specific set of materials vary over an order of magnitude. Charge transfer is usually only tens of electrons except for some tests with gallium arsenide. No material tested shows any correlation between force and charge transfer, and in some cases the charge is too small to account for the measured force. The charge transferred during an adhesive contact does not appear to affect the adhesion in the materials tested.