Abstract View
Modeling Nanoparticle Charge Distribution in the Afterglow of Non-thermal Plasmas and Comparison with Measurements
Vikram Suresh, LI LI, Joshua Redmond Go Filipe, Ranganathan Gopalakrishnan, The University of Memphis
Abstract Number: 31
Working Group: Nanoparticles and Materials Synthesis
Abstract
A modeling approach to investigate the charge distribution of aerosol particles exiting flow-through non-thermal plasmas and the afterglow region is presented. Understanding the effect of plasma concentration, discharge parameters, plasma temperature, diffusivity of the charged species, and reaction rate constants on the resulting particle charge distribution, is critical in relevant applications, notably in materials synthesis and processing. In this work, collision kernel (βpi) models developed in prior work by analyzing particle-ion trajectories calculated using Langevin Dynamics based simulations, are incorporated into species transport equations for ions, electrons, and charged particles in the afterglow. The developed collision rate constant models are validated by comparing predictions of particle charge against measured values in stationary, non-thermal DC plasma from past PK-4 campaigns (published in Phys. Rev. Lett. 93(8):085001 and Phys. Rev. E 72(1): 016406). The comparisons reveal excellent agreement within ±35% for particle of radius 0.6,1,1.3μm in the gas pressure range of ~20 – 150 Pa. The atmospheric-pressure flow-through plasma experiments by Sharma et al. (J. Physics D: Appl. Phys. 53(24): 245204) to probe particle charge distributions are modeled using the experimentally validated particle-ion collision rate constant models and the calculated charge fractions are compared with measurements. The comparisons reveal that the ion/electron concentration and gas temperature in the afterglow critically influence particle charge and the predictions are generally in qualitative agreement with the measurements. Modeling assumptions and challenges will be highlighted. Situations where particle charge states at the entry of the afterglow region are in the order of ~1000e- require a different computational treatment and this research is afoot. Published in the J. Physics D: Applied Physics (doi: https://iopscience.iop.org/article/10.1088/1361-6463/abf70c). Funding for this work was provided by US National Science Foundation (NSF) PHY Grant Award Number 1903432 and US Department of Energy Office of Science Grant Award Number DE-SC0021206.