Characterization of particle charging in low-temperature, atmospheric-pressure, flow-through plasmas

Girish Sharma, Nabiel Abuyazid, Sukrant Dhawan, Sayali Kshirsagar, R. Mohan Sankaran, Pratim Biswas

Research output: Contribution to journalArticlepeer-review

Abstract

While plasmas are now routinely employed to synthesize or remove nano-to micron-sized particles, the charge state (polarity and magnitude) of the particles remains relatively unknown. In this study, charging of nanoparticles was systematically characterized in low-temperature, atmospheric-pressure, flow-through plasmas previously applied for synthesis. Premade, charge-neutral nanoparticles of MgSO4, NaCl, and sea salt were introduced into the plasma to decouple other effects such as the reactive vapor precursor, and MgSO4 was selected as the focus because of its stability (i.e., no evaporation) in the plasma environment. The charge fraction and distribution of the particles was examined at the reactor outlet for different particle diameters (10-250 nm) as a function of plasma power and two types of power source, alternating current (AC) and radio frequency (RF). We found that the overall charge fraction increased with increasing plasma power and diameter for the RF plasma. A similar increasing trend was observed for the AC plasma with increasing particle diameter in the range of 50-250 nm, but the charge fraction increased with decreasing particle diameter in the range of 10-50 nm. The charge distribution was revealed to be bipolar, with particles supporting multiple charges for both the RF and AC plasmas, but the RF plasma produced a higher fraction of multiple charges. Differences in the characteristic timescales for particle charging in the AC and RF plasmas are a possible explanation of the trends observed in the experiments.

Original languageEnglish (US)
Article number245204
JournalJournal of Physics D: Applied Physics
Volume53
Issue number24
DOIs
StatePublished - Jun 10 2020
Externally publishedYes

Keywords

  • charging mechanism
  • dusty plasma
  • electrostatic precipitators
  • particle charging
  • tandem differential mobility analysis

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films

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