Electrophoretic Aerosol focusing for Soot Particle Analysis

In this work, a focused deposition technique was developed and applied to soot particles produced in a laminar premixed flame of ethylene and air. Particles were collected by means of an Electrostatic Precipitator (ESP), coupled with a Corona charger device used for unipolar charging of particles. Charged aerosol particles were electrostatically focused on a mica muscovite disks positioned on the ESP electrode by an electrically grounded metal mesh. Particle dimensions were measured by means of a Scanning Mobility Particle Sizer system, constituted by a nano-Differential Mobility Analyzer (DMA) and an Ultrafine Condensation Particle Counter (CPC). The collection efficiency of the system constituted by the corona charger and the ESP was calculated to be 99%, by measuring particle concentration exiting the ESP when the voltage is applied, and comparing it to particle concentration exiting the ESP when no voltage is applied. The focusing method was tested with an optical microscope observing focused carbonaceous nanoparticles in spots of tens of microns in dimension. This method can be used as an effective sampling procedure for ex-situ analysis of carbonaceous nanoparticles, since it allows obtaining reduced sampling times and enhanced analysis resolutions.