On the nature of droplet production in DC glows with a liquid anode: mechanisms and potential applications

Journal Article · Wed Nov 09 00:00:00 EST 2022 · Plasma Sources Science and Technology

DOI:https://doi.org/10.1088/1361-6595/ac9c8e· OSTI ID:2346110

Yang, Zimu ^[1]; Kovach, Yao ^[1]; Wang, Zhehui ^[2]; Foster, John ^[1]

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1. Univ. of Michigan, Ann Arbor, MI (United States)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

The interactions between plasma and liquid solutions give rise to the formation of chemically reactive species useful for many applications, but the mass transport in the interfacial region is usually limited and not fully understood. In this work, we report on the observation and explanation of droplet ejection at the plasma–liquid interface of a one-atmosphere glow discharge with the liquid anode. The impact of droplets emission on plasma properties is also analyzed by spectroscopy. The process, which is an efficient mass and charge transport mechanism, apparently occurs during discharge operation and thus constitutes a feedback vehicle between the discharge and the liquid. Distinctive from the well-known Talyor cone droplets associated with liquid cathodes, the observed droplets originate from the bubbles due to electrolysis and solvated air which does not require strong electric field at liquid surface. Instead, the droplets are ejected by bubble cavity rupture at the plasma–liquid interface and their size, initial speed are strongly dependent on the gravity, inertia and capillarity. Further, the droplets emerge near the plasma attachment and are subsequently vaporized, emitting intense UV and visible light, which originated from excited OH radicals and sodium derived from the liquid electrolyte. Spectroscopy analysis confirmed that the bursting droplets generally reduce the gas temperature while their effects on electron density depend on the composition of the liquid anode. Results also show that droplets from NaCl solution increase the plasma electron density due to the lower ionization potential of sodium. These findings reveal a new mechanism for discharge maintenance and mass transport as well as suggest a simple approach to dispersing plasma-activated liquid into the gas phase and thus enhancing plasma–liquid interaction.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: 89233218CNA000001; SC0018058
• OSTI ID: 2346110
• Report Number(s): LA-UR--24-23065
• Journal Information: Plasma Sources Science and Technology, Journal Name: Plasma Sources Science and Technology Journal Issue: 11 Vol. 31; ISSN 0963-0252
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
interfacial mass transfer
optical emission spectroscopy
plasma-aerosol
plasma-liquid interactions