Bulletin of the American Physical Society
73rd Annual Gaseous Electronics Virtual Conference
Volume 65, Number 10
Monday–Friday, October 5–9, 2020; Time Zone: Central Daylight Time, USA.
Session QW4: Gas Phase Plasma ChemistryLive
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Chair: Osamu Sakai, Univ. Shiga Prefecture |
Wednesday, October 7, 2020 3:00PM - 3:30PM Live |
QW4.00001: Further development of plasma-assisted inkjet printing Invited Speaker: Tsuyohito Ito Further development of plasma-assisted inkjet printing, where inks during flight and after landing on a substrate are irradiated by atmospheric-pressure nonequilibrium plasma, will be presented. When the ejected ink was exposed to plasma, reactive species from the plasma as well as rapid and local heating are expected to promote various reactions. Thus plasma-assisted inkjet printing could provide various advantages to inkjet printing, such as less pre- or post-treatments, low-temperature and rapid sintering/reduction, narrower pattern width, and/or on-site polymerization. In the case with silver patterning using silver-nanoparticle-dispersed ink [1], compared with heat treatment, narrower line width could be achieved with low substrate temperature and a short single-step process. Furthermore, with poly(3,4-ethylenedioxythiophene) (PEDOT) pattern fabrication using 3,4-ethylenedioxythiophene (EDOT) monomer stock solution ink [2], plasma-assisted polymerization during printing process was demonstrated. Fabrication of gold patterns using particle-free aqueous chloroauric acid solution ink [3] was also achieved to demonstrate plasma-assisted reduction of ions to fabricate metallic patterns. Further details will be presented at the conference. [1] M. Tsumaki, K. Nitta, S. Jeon, K. Terashima, T. Ito, J. Phys. D: Appl. Phys. 51, 30LT01 (2018). [2] K. Nitta, M. Tsumaki, T. Kawano, K. Terashima, T. Ito, J. Phys. D: Appl. Phys. 52, 315202 (2019). [3] K. Nitta, K. Ishizumi, Y. Shimizu, K. Terashima, T. Ito, to be submitted. [Preview Abstract] |
Wednesday, October 7, 2020 3:30PM - 3:45PM Live |
QW4.00002: Tailoring OH and O production in an atmospheric-pressure plasma in Helium with O$_2$ and H$_2$O admixtures Erik Wagenaars, Alexandra Brisset, Sandra Schroeter, Kari Niemi, Deborah O'Connell, Jean-Paul Booth, Andrew R. Gibson Reactive oxygen species (ROS), including OH and O, are key in many applications of atmospheric-pressure plasmas. Controlled delivery of known amounts of ROS is important for the efficiency and safety of plasma-based treatments. Adding molecular admixtures such as O$_2$ and H$_2$O to the plasma feed gas, rather than relying on ambient diffusion, enhances control of ROS production. Here, we investigated the kinetics of OH and O in an RF atmospheric-pressure plasma in Helium with H$_2$O+O$_2$ admixtures. The density of OH was measured by UV absorption spectroscopy. A 0D plasma-chemical kinetics model was used to compare the experimental results and understand the reaction pathways. Increasing densities of OH in the order of 10$^{14}$~cm$^{-3}$ were measured for increasing H$_2$O content. The addition of O$_2$ did not significantly increase the OH density, despite the fact that the OH production, mainly through O and O* species, increases by a factor of ten, because the destruction pathways also depend on O and O*, and increase accordingly by roughly the same factor. This means that admixtures of H$_2$O+O$_2$ allow independent control of OH, through H$_2$O content, and O, through O$_2$ content, allowing more detailed control of ROS delivery in applications. [Preview Abstract] |
Wednesday, October 7, 2020 3:45PM - 4:00PM Live |
QW4.00003: Evaluating Chemical Kinetic Schemes for a CO\textlnot 2 Microwave Reactor: Using the Afterglow with Forethought Floran Peeters, Gonçalo Raposo, Juehan Gao, Alex van de Steeg, Pedro Viegas, Luca Vialetto, Elizabeth Mercer, Pieter Willem Groen, Tim Righart, Bram Wolf, Waldo Bongers, Paola Diomede, Gerard van Rooij, Richard van de Sanden Chemical kinetic modelling is the most important tool in the study of complex molecular plasmas. In plasmas for chemical conversion, ionization degrees are low, and neutral densities and gas temperatures high, making neutral-neutral interactions a leading contributor to the chemistry. At DIFFER, microwave plasma in pure CO$_{\mathrm{2}}$ is developed for production of carbon-neutral synthetic fuels, but can also find application in in-situ resource utilization in the CO$_{\mathrm{2}}$-rich Martian atmosphere. Both applications benefit from a thorough understanding of the underlying chemistry. In this contribution, an overview will be given of the most important ground-state chemical reactions in CO2, revealing a considerable uncertainty in reaction rate coefficients. By comparing a 2D-axisymmetric model with measured afterglow emission from our CO2 microwave plasma, we establish effective rate coefficients for the case of highly dissociated CO2 at reduced pressure. Increased certainty in neutral-neutral rate coefficients then allows us to improve models of the plasma itself, where the same reactions predominate and indirectly affect the electron kinetics. [Preview Abstract] |
Wednesday, October 7, 2020 4:00PM - 4:15PM Live |
QW4.00004: Student Excellence Award Finalist:Reconsidering the importance of vibrations and translations:a new perspective on efficient plasma activation of CO$_{\mathrm{2}}$ A.J. Wolf, F.J.J. Peeters, P.W.C. Groen, T.W.H. Righart, W.A. Bongers, M.C.M. van de Sanden Vibrational non-equilibrium conditions are frequently put forward as a prerequisite for energy-efficient chemical conversion of CO$_{\mathrm{2\thinspace }}$in moderate to high-pressure plasma sources. The merits and mechanisms of non-equilibrium plasma reactivity are, however, still subject to debate as key literature results remain to be reproduced experimentally. Furthermore, the consequences of pressure-related discharge contraction and gas-dynamic transport are often disregarded, despite being essential in a comprehensive interpretation of plasma-chemical experiments. In this contribution, plasma contraction and transport are consolidated for the first time using 2D thermal chemical kinetics modeling of the flow reactor. By incorporating experimentally obtained non-uniform power deposition profiles, gas temperatures, and approximations for axial and radial transport, a holistic but straightforward description of the CO$_{\mathrm{2\thinspace }}$microwave plasma emerges: we find that the reactor performance is adequately described by plasma-induced thermal chemistry. However, the predominance of turbulent transport of plasma species towards colder regions may induce strong (vibrational) non-equilibrium conditions in the plasma periphery, irrespective of the quasi-thermal nature of the plasma itself. Leveraging the reactivity of O radicals with CO$_{\mathrm{2}}$ in a non-equilibrium plasma periphery may make possible energy efficiencies of over 70{\%}, warranting further investigation into post-discharge kinetics and transport. [Preview Abstract] |
Wednesday, October 7, 2020 4:15PM - 4:30PM Live |
QW4.00005: Transport and chemistry in CO$_{\mathrm{2}}$ microwave plasma unraveled by \textit{in-situ} laser scattering. Alex van de Steeg, Pedro Viegas, Floran Peeters, Ana Sovelas da Silva, Paola Diomede, Richard van de Sanden, Gerard van Rooij Efficient dissociation of CO$_{\mathrm{2}}$ to CO for fuel and chemicals production is studied in a vortex-stabilized microwave plasma reactor. Unprecedented detail in spatial distributions of temperature, internal energy, and species concentrations is obtained with \textit{in-situ} spontaneous Raman in scans of pressure (\textasciitilde 0.1 bar) and flow (10-20 slm) at 1 kW power. Dissociation fractions were typically lower compared to the chemical equilibrium for the measured core temperatures that ranged from 4500K to 6000K, which suggests particle replacement times as fast as several microseconds in plasma core. Peaking of oxygen molecules upstream from the region of atomic oxygen production indicates a central recirculation zone. Analysis of chemistry rates reveals minimal CO back reactions in the reactor and confirms quenching with CO$_{\mathrm{2}}$ is the dominant O loss mechanism. Comparison of radial profiles of dissociation with global CO yield demonstrates where flow lines start to connect with the exhaust. These measurements demonstrate the importance of multidimensional transport for optimization of the plasma reactor. [Preview Abstract] |
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