Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications

Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications

Bibliographic Details
Main Author: Gulko, Ilya Dmitrievich
Language:English
Published: The Ohio State University / OhioLINK 2020
Subjects:
Energy
Engineering
Environmental Engineering
Chemistry
hybrid plasma combined discharge raman spectroscopy diode laser absorption spectroscopy fourier transform infrared spectroscopy optical diagnostics plasmacatalysis catalysis synthesis ammonia
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=osu1598271986860656
id ndltd-OhioLink-oai-etd.ohiolink.edu-osu1598271986860656
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Energy
Engineering
Environmental Engineering
Chemistry
hybrid plasma combined discharge raman spectroscopy diode laser absorption spectroscopy fourier transform infrared spectroscopy optical diagnostics plasmacatalysis catalysis synthesis ammonia
spellingShingle Energy
Engineering
Environmental Engineering
Chemistry
hybrid plasma combined discharge raman spectroscopy diode laser absorption spectroscopy fourier transform infrared spectroscopy optical diagnostics plasmacatalysis catalysis synthesis ammonia
Gulko, Ilya Dmitrievich
Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
author Gulko, Ilya Dmitrievich
author_facet Gulko, Ilya Dmitrievich
author_sort Gulko, Ilya Dmitrievich
title Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
title_short Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
title_full Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
title_fullStr Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
title_full_unstemmed Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications
title_sort ns pulse / rf hybrid plasmas for plasma chemistry and plasma assisted catalysis applications
publisher The Ohio State University / OhioLINK
publishDate 2020
url http://rave.ohiolink.edu/etdc/view?acc_num=osu1598271986860656
work_keys_str_mv AT gulkoilyadmitrievich nspulserfhybridplasmasforplasmachemistryandplasmaassistedcatalysisapplications
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-osu15982719868606562021-09-21T05:10:35Z Ns Pulse / RF Hybrid Plasmas for Plasma Chemistry and Plasma Assisted Catalysis Applications Gulko, Ilya Dmitrievich Energy Engineering Environmental Engineering Chemistry hybrid plasma combined discharge raman spectroscopy diode laser absorption spectroscopy fourier transform infrared spectroscopy optical diagnostics plasmacatalysis catalysis synthesis ammonia Non-self-sustained hybrid plasmas are formed by the overlap of two separate voltage waveforms with significantly different reduced electric field values (E/N), one of them below the ionization threshold, to produce excited species and radicals selectively. In this work, a stable, capacitively coupled ns pulse – RF waveform hybrid discharge is operated in nitrogen and mixtures of nitrogen with other molecular gases at 50 – 100 Torr pressure, using a single pair of electrodes mounted externally to the reactor cell. The purpose of the ns pulse discharge is to generate ionization and electronic excitation of the mixture components, while the below-breakdown RF voltage couples additional energy to the vibrational modes of the mixture components. Based on the broadband plasma emission imaging, the plasma volume appears to be enhanced by the RF waveform, compared to ns pulse discharge, due to the drift oscillations of electrons induced by the RF waveform. Coherent Anti-Stokes Raman Spectroscopy (CARS) measurements in the hybrid discharge operated in nitrogen show that the RF waveform significantly enhances the vibrational excitation of N2 in the ground electronic state, populating vibrational levels up to at least v=3, and increasing the vibrational temperature of N2 from TV = 1210 ± 110 K in the ns pulse train plasma to TV = 1810 ± 170 K in the ns-RF hybrid discharge. The translational- rotational temperature at these conditions remains low, TR = 315 ± 15 K. To evaluate the potential of this plasma to operate in other gas mixtures, 1% of H2 is added to nitrogen. CARS measurements reveal a moderate N2 vibrational relaxation by hydrogen, reducing the vibrational temperature in the hybrid plasma to TV = 1700 ± 150 K and increasing in the translational-rotational temperature to TR = 396 ± 10 K. Time-resolved measurements of the number density of the first electronically excited state of nitrogen, N2(A3Σ), obtained using Tunable Diode Laser Absorption Spectroscopy (TDLAS) in nitrogen and 1% H2-N2 mixture, indicate a rapid quenching mechanism of N2(A3Σ), likely via energy pooling, as well as the accumulation of a rapid quenching species, most likely N atoms produced by electron impact dissociation in the ns pulse train discharge. Additionally, a significant amount of H atoms generated by electron impact dissociation in the ns pulse discharge and reactive quenching of electronically excited N2 is detected. The RF waveform results in only a modest, ~20% increase in the number density of N2(A3Σ), which suggests that N2 vibrational excitation by the RF discharges is produced selectively, without significant additional electronic excitation. These results show a potential to isolate the role of different excited species (i.e. vibrationally and electronically excited N2, as well as N and H atoms) in plasma chemical formation of ammonia, NH3, and potentially as an effective means for selective plasmachemical catalysis, to enable efficient NH3 synthesis in low- temperature plasmas. To evaluate the potential of the hybrid plasma sustained in other reacting molecular gas mixtures, the ns-RF discharge is operated in 1% CO-N2 and 0.1% CO2-N2 flows. Fourier Transform Infrared (FTIR) emission spectroscopy measurements show that the RF waveform dramatically enhances the CO vibrational level populations in the CO-N2 mixture, populating levels up to at least v=10, at CO vibrational temperature of TV = 3330 K. In the mixture with CO2, the CO2 fundamental infrared emission intensity is dramatically enhanced by the RF waveform, with the CO2 vibrational mode (symmetric stretch / bending and the asymmetric stretch) temperatures of T12 = 760 K and T3 = 1725 K, significantly exceeding the translational- rotational temperature, T = 570 K. The number density of CO product, inferred from ex-situ FTIR absorption spectra downstream of the ns-RF hybrid plasma, increases by a factor of two with the addition of the RF waveform, which indicates a significant role of CO2 vibrational excitation for its dissociation in the plasma, and suggests the potential for using the hybrid plasma for efficient conversion of CO2 to other value-added chemicals. 2020 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1598271986860656 http://rave.ohiolink.edu/etdc/view?acc_num=osu1598271986860656 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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