Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session SR51: Atmospheric and High Pressure Plasmas: Chemistry and Others |
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Chair: Charles Durfee, Colorado School of Mines Room: GEC platform |
Thursday, October 7, 2021 4:00PM - 4:30PM |
SR51.00001: Plasma-catalytic hydrogenation of CO2: elucidating thermodynamically- or kinetically-limited step Invited Speaker: Tomohiro Nozaki CO2 conversion to useful chemicals attracts keen attention. Particularly, the use of electricity to drive catalytic conversion of CO2 is recognized as key decarbonizing technology because renewable energy is used directly to activate stable molecules. Low-temperature catalysis, due to electron-driven chemistry, is critically important to mitigate overall CO2 emission because the high-temperature heat is no longer necessary and thus eliminates the combustion process from the system. Nonthermal plasma catalysis becomes one of the feasible chemical conversion technology in addition to photocatalysis, electrochemistry, and a combination of those. |
Thursday, October 7, 2021 4:30PM - 4:45PM |
SR51.00002: Behavior of Atomic Oxygen in Pulsed Barrier Discharge in Sub-atmospheric Pressure Oxygen Yusuke Nakagawa, Yuta Iwata, Fumiyoshi Tochikubo Atmospheric-pressure cold plasma (APCP) exhibits high chemical reactivity and valuable applicability to various targets including liquids and living materials. APCP produces high-density radicals, whereas the radical's lifetime is short due to a frequent collisional deactivation. To address this issue, we focus on the plasma under sub-atmospheric pressure, which is slightly reduced pressure from the atmosphere. In sub-atmospheric pressure plasma, the radical's lifetime will be extended maintaining the variety of the targets. In this study, we measured the behavior of atomic oxygen (O) in needle-to-sphere pulsed barrier discharge in sub-atmospheric pressure oxygen, using TALIF spectroscopy. The half-value period of atomic oxygen was extended by a factor of 10 by reducing pressure from 95 kPa to 20 kPa, whereas the peak O density at 20 kPa was 70% of that at 95 kPa. Therefore, radical flux in sub-atmospheric pressure plasma will be significantly higher than that in the atmospheric-pressure. The relatively high production rate of O compared with atmospheric-pressure indicates that the electron energy enhancement owing to reducing pressure led to an increase in the O2-dissociation rate, in spite of small amount of electrons and feedstock O2 gas in the reduced pressure. |
Thursday, October 7, 2021 4:45PM - 5:00PM |
SR51.00003: Chemical Modifications of Cysteine treated by Ar- and He- based Dielectric Barrier Discharges with Varying O2 and H2O content Niklas Nawrath, Friederike Kogelheide, Bastian Hillebrand, Peter Awakowicz, Andrew Gibson The interactions between biological samples and atmospheric pressure plasma sources are very complex and still not understood in detail. In general, these interactions are driven by reactive oxygen and nitrogen species (RONS), such as •OH, O₂− and NO. A major factor affecting RONS is the gas mixture the plasma is formed in. To understand their influence on the chemical modifications of biological targets, the biomolecule Cysteine is used as simplified target and treated with Argon- and Helium-based plasmas with varying H₂O and O₂ content. As plasma source, we use a well-characterized dielectric barrier discharge at atmospheric pressure in a chamber to control the exact operating conditions. The Cysteine samples are analysed by FTIR spectroscopy. With increasing molecular admixture, several molecular structures in the Cysteine molecule change in intensity and new structures are produced. The decrease in signal intensity of hydrogen containing groups is directly associated to an intensity increase of the corresponding oxygen containing groups. To provide insights into the underlying mechanisms, plasma parameters (e.g. gas temperature and UV flux) are measured by optical emission spectroscopy. |
Thursday, October 7, 2021 5:00PM - 5:30PM |
SR51.00004: Plasma Streamer Propagation in the Gas Phase, Catalyst Pores and Surface DBD Invited Speaker: Quan-Zhi Zhang Streamer discharges at atmospheric pressure have been widely used for various environmental applications, such as hydrocarbon reforming, air pollution control, greenhouse gas conversion, and nitrogen fixation. However, the propagation mechanism and the interactions between the plasma streamer and dielectrics/catalysts are rather complicated and still far from being well understood. On one hand, depending on the polarity of the applied voltage, either a negative or positive streamer can be generated, and its propagation behavior and interactions with material surfaces are very distinct. On the other hand, the discharge structure could be very different, including the gas phase, packed dielectric-barrier discharge (DBD) with catalysts, internal space in catalysts and surface DBD (SDBD). |
Thursday, October 7, 2021 5:30PM - 5:45PM |
SR51.00005: Ar metastable kinetics: Role of photoemission in a LF and LF-RF DBD in Ar-NH3 at atmospheric pressure Raphaël Robert, Gerjan Hagelaar, Nader Sadeghi, Romain Magnan, Luc Stafford, Françoise Massines The population of metastable argon atoms (1s3 and 1s5 in Paschen notation) are recorded in an atmospheric pressure Ar-NH3 DBD at 50 kHz (LF) and 5 MHz+50 kHz (RF+LF). A 1D fluid model is used to compare the kinetics of Arm in these discharges. From the comparison between measurements and calculations, it is shown that the evolution of metastables in the model is too slow and does not fit the temporal evolution measured during a LF cycle. By adding a photoemission process via the dissociation of an argon dimer to the model, the kinetics is improved, and the model reproduces the various physical phenomena experimentally observed in both LF and LF + RF discharges. After a preliminary study, it seems that photoemission is an essential mechanism driving the discharge kinetics in homogeneous DBDs at atmospheric pressure. |
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