AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Evolution of Capacitance for Agglomerated Nanoparticles during Sintering
LEO N.Y. CAO, Jing Wang, Heinz Fissan, Sotiris E. Pratsinis, Max L. Eggersdorfer, David Y. H. Pui, University of Minnesota
Abstract Number: 145 Working Group: Aerosol Physics
Abstract Electrical capacitance of aerosol particles is an important property for classification of particles by electrical mobility, precipitation of particles in electrical fields, measurements of morphological parameters of particles by their charging properties, etc. Usually, a minimum potential energy method developed by Brown & Hemingway (1995) is used to calculate the electrical capacitance developed for agglomerates composed of spherical PPs (primary particles). By discretizing a particle, representing it by finite spherical elements in different sizes only on its surface, we extended this method to particles of arbitrary shapes in this work. We applied the method to compute the capacitance of diffusion limited cluster-cluster agglomerates (DLCA) and their spatial charge distribution and found that the capacitance of DLCA is a function of mobility diameter which is measurable and nearly independent of PP diameter. Based on the obtained capacitance, the modeled particle charge for DLCA in continuum regime of charging agrees well with experimental results. We also simulated DLCA’s sintering processes from fractal-like expressed by equivalent PP-diameter and number of PPs to compact structure and investigated the change in their capacitance. The results demonstrated strong effect of particle morphology on the capacitance, with the capacitance decreasing as the structure became more compact and reaching about 40% of the loose agglomerate value when an agglomerate of 128 PPs was coalesced to a sphere.