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INVESTIGATION OF PARTICULATE MATTER MONITORING USING CONTACT ELECTRICITY
Citation:
John, W., G. Reischl, W. Devor, AND J. Wesolowski. INVESTIGATION OF PARTICULATE MATTER MONITORING USING CONTACT ELECTRICITY. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-78/212 (NTIS PB289565), 1978.
Description:
To better understand the contact electrification monitor for particulate matter, charge transfer by aerosol particles impacting on metal surfaces has been investigated. Monodisperse, uniformly charged or neutral aerosol particles (1-5 micrometer diameter) from a vibrating orifice or fluidized bed generator were bounced on a metal probe. The transfer of precharge from the particles were found to be sensitive indicators of the probe surface condition. A surface preparation procedure was developed which yielded linear charge transfer curves. Measurements were made of methylene blue, potassium biphthalate, sodium chloride and aluminum particles impacting on stainless steel, Inconel, titanium and platinum probes. For insulating materials, the transfer of precharge was independent of particle size while the contact charge was proportional to the cube of particle diameter and directly proportional to impact velocity. The magnitude of the contact charge was strongly dependent on the electrical resistivity of the material. A theoretical model was found to account semi-quantitatively for all aspects of the data. A major remaining difficulty is the lack of knowledge of the contact potential. The implications of these findings for monitoring applications is discussed in detail and the advantages and disadvantages of the monitor are assessed.