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Mode Transition of Filaments in Packed-Bed Dielectric Barrier Discharges

1
Department of Physics, Wuhan University of Technology, Wuhan 430070, China
2
Research group PLASMANT Department of Chemistry University of Antwerp, B-2610 Wilrijk-Antwerp, Belgium
3
School of Physics Science and Technology, Anshan Normal University, Anshan 114007, China
4
Shanghai Bright-Tech Information Technology Co. Ltd., Shanghai 201206, China
*
Author to whom correspondence should be addressed.
Catalysts 2018, 8(6), 248; https://doi.org/10.3390/catal8060248
Received: 15 May 2018 / Revised: 12 June 2018 / Accepted: 13 June 2018 / Published: 15 June 2018
(This article belongs to the Special Issue Plasma Catalysis)
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Abstract

We investigated the mode transition from volume to surface discharge in a packed bed dielectric barrier discharge reactor by a two-dimensional particle-in-cell/Monte Carlo collision method. The calculations are performed at atmospheric pressure for various driving voltages and for gas mixtures with different N2 and O2 compositions. Our results reveal that both a change of the driving voltage and gas mixture can induce mode transition. Upon increasing voltage, a mode transition from hybrid (volume+surface) discharge to pure surface discharge occurs, because the charged species can escape much more easily to the beads and charge the bead surface due to the strong electric field at high driving voltage. This significant surface charging will further enhance the tangential component of the electric field along the dielectric bead surface, yielding surface ionization waves (SIWs). The SIWs will give rise to a high concentration of reactive species on the surface, and thus possibly enhance the surface activity of the beads, which might be of interest for plasma catalysis. Indeed, electron impact excitation and ionization mainly take place near the bead surface. In addition, the propagation speed of SIWs becomes faster with increasing N2 content in the gas mixture, and slower with increasing O2 content, due to the loss of electrons by attachment to O2 molecules. Indeed, the negative O2 ion density produced by electron impact attachment is much higher than the electron and positive O2+ ion density. The different ionization rates between N2 and O2 gases will create different amounts of electrons and ions on the dielectric bead surface, which might also have effects in plasma catalysis. View Full-Text
Keywords: plasma catalysis; mode transition; packed-bed dielectric barrier discharge; particle-in- cell/Monte Carlo collision method; surface filament; gas composition plasma catalysis; mode transition; packed-bed dielectric barrier discharge; particle-in- cell/Monte Carlo collision method; surface filament; gas composition
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Gao, M.; Zhang, Y.; Wang, H.; Guo, B.; Zhang, Q.; Bogaerts, A. Mode Transition of Filaments in Packed-Bed Dielectric Barrier Discharges. Catalysts 2018, 8, 248.

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