Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session LW3: Plasmas in Liquids II |
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Chair: Naoki Shirai, Hokkaido University Room: Century III |
Wednesday, October 30, 2019 1:45PM - 2:00PM |
LW3.00001: A volume of fluid (VOF) based approach for modeling plasma discharge in multi-fluid configuration Ali Charchi Aghdam, Tanvir Farouk Despite the large volume of experimental studies on plasma discharges in multi-fluid/multi-liquid configuration there is still no notable modeling effort in simulating the multi-physics problem. In this work, a multi-physics numerical framework is developed to study the plasma discharge in a two-liquid system. The multi-physics model consists of Poisson's equation solver, species solver and, multi-phase fluid flow solver. A Volume of Fluid (VOF) based approach is used to resolve the two-phase flow problem. Properties of liquids and plasma species are updated based on the electric field and phase composition. The evolution of interface as well as plasma discharge pattern is studied as a function of initial interface location, voltage profile, and permittivity ratio of the phases. The VOF method was successful in capturing the evolution of the fluid interface due the presence of the electric field and associated plasma charges. The results show that the discharge profile has a strong dependence on the interface location. Also, it is found that the two-phase configuration has an enhancing effect on the electric field and plasma discharge can be achieved at lower voltages thus proving to be an energy efficient method for practical applications. [Preview Abstract] |
Wednesday, October 30, 2019 2:00PM - 2:15PM |
LW3.00002: Student Excellence Award Finalist: Size control of plasma-activated liquid layer on ice surface by thermodynamic parameters Noritaka Sakakibara, Tsuyohito Ito, Kazuo Terashima Plasma-liquid interactions are attracting a significant attention for wide range of applications from materials synthesis to bio-medical applications. We are now investigating plasma-ice interface as a novel opportunity of plasma-liquid interactions research [1]. Here, we report size control of plasma-activated liquid layer on ice surface, by tuning thermodynamic parameters such as temperature and concentration of aqueous solution [2]. In this study, plasma-induced synthesis of gold nanoparticles film was performed on the frozen gold ions solution. As a result, the thickness of the synthesized film was revealed to be tuned in micrometer scale, depending on temperature of freezing or initial concentration of gold ions solution. This result points the demonstration of size control of plasma-activated liquid layer on the surface of ice, which should give rise to a new insight and novel approach on plasma-liquid interactions. [1] N. Sakakibara and K. Terashima, J. Phys. D: Appl. Phys. 50 (2017) 22LT01. [2] N. Sakakibara et al., Langmuir 35 (2019) 3013-3019. [Preview Abstract] |
Wednesday, October 30, 2019 2:15PM - 2:30PM |
LW3.00003: Nanosecond-pulsed discharges in liquid nitrogen for synthesis of polynitrogen materials Danil Dobrynin, Roman Rakhmanov, Alexander Fridman Low power nanosecond-pulsed discharges in liquids are typically characterized by relatively small sizes (on the order of mm) and high densities (from 10$^{\mathrm{17}}$ to 10$^{\mathrm{20}}$ cm$^{\mathrm{-3}}$ in different experiments) and are believed to be generated, or at least initiated, directly in liquid phase before formation of gaseous voids or bubbles. Although spectroscopic measurements of heavy particles temperature (``gas'' temperature) is extremely difficult in low energy nanosecond-pulsed discharges, especially in the case of water discharges where the emission spectra show broad-band continuum, estimations from OH emission from the secondary ``bubble'' phase of the discharge show that the discharge is actually non-thermal (\textasciitilde 100-200 K increase of associated temperature). In this study we focus on characterization of nanosecond-pulsed discharge in liquid nitrogen, specifically, imaging and estimation of temperature from spectroscopic measurements. First temperature estimations from the molecular nitrogen emission shows maximum temperature increase on the order of 60 K which is advantageous for non-thermal material synthesis in liquid phase. In addition, we report on observations of generation of unstable ``energetic'' material directly from liquid nitrogen, which may be preliminarily identified as a form of polynitrogen compound. [Preview Abstract] |
Wednesday, October 30, 2019 2:30PM - 2:45PM |
LW3.00004: Time-resolved Nanosecond Imaging of Single-electrode Pulsed Plasma Branches in Water Christopher Campbell, Xin Tang, Christopher Limbach, Yancey Sechrest, Jeph Wang, David Staack Pulsed plasmas in liquids present a complex multiphysics environment which challenges conventional fast (ns) imaging techniques. This work focuses on nanosecond-pulsed single-electrode plasma discharge processes in distilled water. Previous work identifies a mode transition from spherical discharges to branched discharges in these types of water plasmas, sensitive to water conductivity and pulse energy. For branched water plasmas generated with 30 kV 5 mJ voltage pulses (rise rate of 2.5 kV/ns), these plasma branches can be up to 5 mm long and $<$10 $\mu$m across. Preliminary results suggest that branch length scales with voltage, and that the propagation speed of these branches is $\sim$20 km/s. Due to the high power densities ($>$10$^{10}$ W/cm$^{3}$) and high electron densities ($>$10$^{18}$ cm$^{-3}$) which occur in multiphase water during short timescales ($<$50 ns), this thermodynamic environment is difficult to model; time-resolved experimental interrogation is therefore necessary. For sufficient time resolution, low-jitter operation was achieved using a laser-triggered (Nd:YAG, 266 nm, 30 mJ/pulse) air spark gap switch as well as a solid-state nanosecond-pulsed power supply. Fast time-resolved imaging results using optical and X-ray techniques are presented and discussed. [Preview Abstract] |
Wednesday, October 30, 2019 2:45PM - 3:15PM |
LW3.00005: Plasma-based Water Treatment: Opportunities and Challenges Invited Speaker: Selma Mededovic Thagard Electrical discharges within and in contact with water produce various reactive species. Despite competitively high concentrations of oxidative OH radicals and reductive solvated electrons formed, plasma-based water treatment has not yet reached a level of development where it can be commercially used. We have found that the performance of plasma reactors used for water treatment depends on multiple factors including the area of the plasma in contact with water, the discharge phase, bulk liquid mass transport, and the type of the compound treated. This work will present two plasma reactors that integrate these design parameters: 1) an enhanced contact plasma reactor for the degradation of surface-active compounds that has been installed into a mobile trailer and demonstrated for the treatment of groundwater and 2) a spinning disc plasma reactor which has been used to treat non-surfactants. The performance of these plasma reactors will be correlated with the fundamental processes occurring at the plasma-liquid interface and in the bulk liquid. Recommendations for plasma reactor scale-up and opportunities in different water treatment market segments will also be given and discussed. [Preview Abstract] |
Wednesday, October 30, 2019 3:15PM - 3:30PM |
LW3.00006: Effect of mixing alcohol source on synthesis of nanographene by in-liquid plasma Hiroki Kondo, Atsushi Ando, Takayoshi Tsutsumi, Keigo Takeda, Takayuki Ohta, Kenji Ishikawa, Makoto Sekine, Masafumi Ito, Mineo Hiramatsu, Masaru Hori High speed synthesis of nanographene materials with high crystallinity can be realized by in-liquid plasma using alcohol sources. In this method, there is a trade-off relationship between synthesis rate and crystallinity depending on molecular-weights of alcohol sources. This is attributed to etching effects of carbon by oxygen or hydroxy species generated from alcohols. In this study, effect of mixing alcohol and hydrocarbon sources on synthesis of nanographene by in-liquid plasma was investigated. The methanol added 1-butanol or n-hexane were used as source liquid. When only the methanol was used, nanographene was hardly synthesized. This also indicated etching effects of carbon by oxygen or hydroxy species. Depending on mixing ratios of methanol to 1-butanol or n-hexane, a trade-off relationship between synthesis rate and crystallinity was found as well as the cases using pure alcohol sources. However, even when different pure and mixture sources with same composition ratio of carbon (C) to oxygen (O) were used, synthesis amount and crystallinity were not same. This result means that they are not determined only by the C/O ratio. The decomposition process of the raw material itself and the generated precursors could further contribute the synthesis rate and crystallinity. [Preview Abstract] |
Wednesday, October 30, 2019 3:30PM - 3:45PM |
LW3.00007: Determination of OH Radical Concentration in High Water Content Low Pressure DC Glow Discharge using Laser Induced Fluorescence Malik Tahiyat, Tanvir Farouk Experimental efforts using laser induced fluorescence (LIF) to quantify OH distribution in plasma discharge have so far involved trace water vapor either present as residual or added at a known trace concentration to a carrier gas. In one of our prior efforts, we conducted spatially resolved optical emission spectroscopy to determine OH, O, H$_{2}$ and H distribution in the interelectrode separation for a dc discharge operating in high water vapor content. In this research effort, LIF technique was employed to obtain spatially resolved measurement of the OH radicals for low pressure (1-15 Torr) dc discharges operating in high water vapor concentration ($>$90\%). The OH distribution for different discharge currents was also determined. For each operating pressure, voltage-current characteristics and current density are determined and optical emission spectroscopy based temperature measurements are performed to identify the discharge regime of operation. These measurements will provide the necessary data for validating plasma kinetic schemes associated with water vapor. [Preview Abstract] |
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