Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session WF3: Dielectic Barrier Discharges |
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Chair: Anne Bourdon, Ecole Polytechnique Room: 305 AB |
Friday, October 16, 2015 3:30PM - 4:00PM |
WF3.00001: Controlling the Porosity in Silica-like Moisture Barriers Processed in a High Current Dielectric Barrier Discharge Invited Speaker: Hindrik de Vries The high current dielectric barrier discharge was operated in the bi-axial cylindrical electrode geometry. Silica-like films were deposited as a function of the dynamic deposition rate and subsequently characterized by ATR-FTIR and moisture permeation analysis. The relation between microstructure and permeation behaviour with deposition rate is tentatively explained by the presence of an interconnected nano-porous structure facilitating the moisture transport through the films. To overcome the moisture barrier limitations a bi-layer architecture was developed. It was shown that dense silica thin films grown on a porous silica layer can yield excellent effective moisture barrier values less than $\sim$ 1 $\times$ 10$^{-3}$ g/m$^{2}$ day.\\[4pt] In collaboration with Sergey Starostin, FOM institute DIFFER. [Preview Abstract] |
Friday, October 16, 2015 4:00PM - 4:30PM |
WF3.00002: Surface functionalization with atmospheric pressure DBD Invited Speaker: Francesco Fracassi Intense research efforts have been recently made to develop a large variety of deposition processes for the direct and remote DBD deposition of thin films from monomers in gas, vapor and aerosol form. In this contribution, the preparation of organic-inorganic nanocomposite coatings by DBD fed with helium and the aerosol of a dispersion of ZnO nanoparticles in hydrocarbon solvent will be described. The nanocomposite coatings show multifunctional behavior and specifically combine the photocatalytic properties of ZnO with superhydrophobicity. The DBD jet co-deposition of acrylic acid and ethylene to obtain stable coatings containing carboxylic functionalities will be also presented. Results from X-ray photoelectron spectroscopy (XPS) in conjunction with chemical derivatization, and scanning electron microscopy demonstrate the chemical and morphological stability of these coatings upon immersion in water. Finally our recent work on the plasma-enhanced chemical vapor deposition of fluoropolymers on complex three-dimensional (3D) porous substrates, such as polyurethane foams, will be shown. During the deposition, the DBD is ignited inside the porous 3D network of the foams and allows obtaining a uniform coating within their interior. [Preview Abstract] |
Friday, October 16, 2015 4:30PM - 4:45PM |
WF3.00003: Modeling of a packed bed dielectric barrier discharge plasma reactor Koen Van Laer, Annemie Bogaerts The dielectric barrier discharge (DBD), as a source of non-thermal plasma, has been of interest for environmental applications for quite some time. Indeed, plasma can be an interesting alternative for conventional thermal methods, because the input energy solely goes to heating up the electrons, while the rest of the plasma particles (i.e. radicals, ions, neutrals) stay at room temperature. However, the feasible energy efficiency appeared to be on the low side. In order to overcome this, a dielectric packing was introduced in the gas gap of the reactor, forming a so-called packed bed plasma reactor (PBPR). Using COMSOL's built-in plasma module, two different complementary 2D axisymmetric fluid models are used to study the intrinsic 3D problem. As a first step, helium is used as discharge gas, at atmospheric pressure and room temperature. It was found that the contact points between the packing beads are of direct importance to initiate the plasma. Indeed, at low applied potential, the discharge is initiated directly at the contact points and stays in this region. However, when a high enough potential is applied, the plasma will be able to travel through the gaps in between the beads, spreading from one wall to the other. [Preview Abstract] |
Friday, October 16, 2015 4:45PM - 5:00PM |
WF3.00004: Self organization in dielectric barrier discharge and control of hexagonal structures Seiji Mukaigawa, Takuya Kameyama, Tomohiro Kudoh, Atsuya Yokota, Kosuke Jumonji, Koichi Takaki Symmetric self organized discharge filaments have been observed in the 140$\mu$m microgap dielectric barrier discharge between two parallel glass plates. The spatial distribution of these discharge filaments were revealed by a discharge experiment in which the thickness of dielectric barrier and pressure were changed. An image of the discharge in nano seconds was obtained using an intensified charge-coupled device (ICCD) camera. The diameters of the self-organized filaments, and the distance between them were obtained using the ICCD images. We found that if the dielectric barrier is thinner then the lattice spacing (the distance between the filaments) are smaller. In addition, the lattice spacing at 760 Torr was smaller than that at 380 torr. Numerical calculation showed the same tendency for lattice spacing as the hexagonal pattern structures in the discharge experiments. Therefore, the lattice spacing of hexagonal patterns can be controlled by manipulating the control parameters in an experiment. [Preview Abstract] |
Friday, October 16, 2015 5:00PM - 5:15PM |
WF3.00005: Surface dielectric barrier discharges generated in CO$_{2}$ exhibiting field emission at high pressure David Pai, Sven Stauss, Kazuo Terashima For dielectric barrier discharges (DBDs) generated at atmospheric pressure or less, field emission has generally not been considered as a possible mechanism of electron emission. At higher pressures, however, gas-phase ionization may only become significant at electric fields that are comparable to the threshold field for field emission. Surface DBDs are studied experimentally in CO$_{2}$ from atmospheric pressure up to supercritical conditions ($T_{c}=$304.13 K, $p_{c}=$7.4 MPa). Two discharge regimes are generated using 10-kHz AC excitation. The ``standard'' regime is similar to previously studied surface DBDs in terms of onset voltage as a function of pressure, as well as electrical and optical emission characteristics. However, a ``field-emitting'' regime emerges starting from 0.7 MPa that exhibits constant onset voltage up to 7.9 MPa, purely continuum emission spectra in the visible/near-infrared range, and current waveforms similar to an atmospheric-pressure Townsend discharge. The maximum amount of negative charge deposited as a function of the applied voltage amplitude is consistent with the Fowler-Nordheim equation, demonstrating the presence of field emission. This behavior cannot be attributed to the Townsend or streamer ionization mechanisms, secondary electron emission, or non-discharge processes. No field-emitting structures are specially added to the electrodes. The onset voltage of the field-emitting regime does not follow the modified Paschen's law for field emission-assisted breakdown. [Preview Abstract] |
Friday, October 16, 2015 5:15PM - 5:30PM |
WF3.00006: The influence of reactor walls surface conductivity on carbon dioxide discharge properties in DBD Igor Belov, Sabine Paulussen, Annemie Bogaerts This work examines the properties of a dielectric barrier discharge (DBD) reactor, build for CO$_{2}$ decomposition, by means of electrical characterization, optical emission spectroscopy and gas chromatography. Several features of electric waveforms specific for CO$_{2}$ discharges in the DBD systems were observed (asymmetry, high-current sparse peaks). Current waveforms revealed the difference in the microdischarge development of the positive and the negative half-cycles of the applied voltage. It was found that the discharge current is highly promoted in configurations (i.e. in certain half-cycles) with a conductive cathode. The transition from an asymmetric current waveform to a symmetric one was investigated during tests on CO$_{2}$ decomposition and subsequent conductive carbon film deposition on the reactor walls. The double dielectric (DD) and metal-dielectric (MD) configurations were compared in terms of discharge properties and conversion efficiency. The same effect of discharge current enhancement was observed when a conductive film was deposited on the outer dielectric in the DD configuration. Consequently, also conversion efficiency was found to increase. In addition, optical emission spectroscopy confirmed the strong correlation of plasma reactivity with the presence of a conductive coating on one of the electrodes. This way it is possible to control the process efficiency and modify the microdischarge activity in the DD reactor without using elaborated dielectric materials. [Preview Abstract] |
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