AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Studying the Charging Characteristics of Flame Generated Particles below 3 nm with a Condensation Particle Counter Battery (CPCB)
YANG WANG, Jiayu Li, Jiaxi Fang, Nathan Reed, Pratim Biswas, Washington University in St Louis
Abstract Number: 247 Working Group: Nanoparticles and Materials Synthesis
Abstract Flame synthesis is a dominant method for producing nanoparticles in large quantities. The charging characteristics of nanoparticles in flames significantly affect the nucleation, coagulation, and further growth of nanoparticles. For sub-3 nm particles generated in flames, the charging mechanism is not resolved due to the complex interaction of diffusion charging, thermionization, chemical ionization, and the interference of flame-generated ions (Jiang et al., 2007). Conventional instruments for determining charge distributions rely on external chargers that may introduce contaminant ions below 3 nm, further complicating the determination of charge distributions (Wang et al., 2014). Recent advances in modifying the working conditions of condensation particle counters (CPCs) achieved a shift in the cutoff size for detecting nanoparticles, thus enabling the measurement of particles below 3 nm. Information on particle size distribution and composition can be obtained through a condensation particle counter battery (CPCB), which operates CPCs with different cutoff sizes and working fluids in parallel. This study used a CPCB composed of three CPCs with different cutoff sizes below 3 nm to investigate the size distribution and charging characteristics of freshly nucleated particles generated from a premixed flat flame. The CPCB detected high concentrations of sub-3 nm particles, possibly formed through chemical ionizations in the flame. The concentrations of neutral particles were measured when we applied a charged particle remover (CPR) before particles entered the CPCB, through which the charging efficiencies of sub-3 nm particles were obtained. The effects of introducing synthesis precursors into the flame, the precursor loading rate, and the flame equivalence ratio on the size distributions and charging characteristics of flame-generated particles below 3 nm will be presented.
References:
Jiang, J., Lee, M.-H., Biswas, P. (2007). Journal of Electrostatics 65:209-220.
Wang, Y., Fang, J., Attoui, M., Chadha, T. S., Wang, W.-N., Biswas, P. (2014). Journal of Aerosol Science 71:52-64.