Barrier Discharge In Air Research Articles

Emission Dynamics of the Molecular Nitrogen Bands by Barrier Discharge in Air: Computer Modeling of the Experimental Procedure

Computer modeling is used to reproduce emission dynamics of (0-0) bands of the second positive and the first negative molecular nitrogen systems by a microdischarge channel in barrier discharge in atmospheric-pressure air. This gives a possibility to test the computational model and to evaluate the spectroscopic procedure of the electric field strength determination by the extended relative intensity technique. Computer modeling of the experimental procedure shows that averaging in space and time in experimental measurements may be the reason for the differences in the calculated and experimentally estimated values of E/N ; the last are considerably lower.

Discharge Formation in Air at Atmospheric Pressure in Surface Barrier Microdischarge Arrangements

Surface barrier discharges in air at atmospheric pressure are investigated in different needle electrode arrangements suited for the repetitive generation of single microdischarges. The microdischarge inception takes place at the tip of a needle electrode, and the pathways of discharge channels are determined by the initial electric field configuration even when microdischarges should have accumulated surface charges on the dielectric.

Nanosecond Repetitively Pulsed Dielectric Barrier Discharge in Air at Atmospheric Pressure

Dielectric barrier discharge (DBD) between two cylindrical glass containers with salt water generated by a nanosecond repetitively pulsed power generator is reported. The electrical parameters, luminous images and spectrum diagnosis are presented. It is shown that the DBD possesses a large discharge current and an intense optical emission from the nitrogen second positive system below 400 nm. The gas temperature remains very close to room temperature regardless of pulse polarity. Luminous photographs with a short exposure time down to 2 ns indicate that no filament is observed and the discharge is homogeneous.

Improvement of Polytetrafluoroethylene Surface Energy by Repetitive Pulse Non-Thermal Plasma Treatment in Atmospheric Air

Improvement of polytetrafluoroethylene surface energy by non-thermal plasma treatment is presented, using a nanosecond-positive-edge repetitive pulsed dielectric barrier discharge generator in atmospheric air. The electrical parameters including discharging power, peak and density of micro-discharge current were calculated, and the electron energy was estimated. Surface treatment experiments of polytetrafluoroethylene films were conducted for both different applied voltages and different treating durations. Results show that the surface energy of polytetrafluoroethylene film could be improved to 40 mJ/m2 or more by plasma treatment. Surface roughness measurement and surface X-ray photoelectron spectroscopy analysis indicate that there are chemical etching and implantation of polar oxygen groups in the sample surface treating process, resulting in the improvement of the sample surface energy. Compared with an AC source of 50 Hz, the dielectric barrier discharges generated by a repetitive pulsed source could provide higher peak power, lower mean power, larger micro-discharge current density and higher electron energy. Therefore, with the same applied peak voltage and treating duration, the improvement of polytetrafluoroethylene surface energy using repetitive pulsed plasma is more effective, and the plasma treatment process based on repetitive pulsed dielectric barrier discharges in air is thus feasible and applicable.

Phase resolved cross-correlation spectroscopy on surface barrier discharges in air at atmospheric pressure

Microdischarges in a surface barrier discharge with special asymmetric needle-needle arrangement were investigated by means of cross-correlation spectroscopy (with sub-ns and sub-mm resolution) and an intensified CCD camera equipped with a far field microscope. The surface barrier discharge was driven at conditions (overvoltage) resulting in several microdischarges per half period of the applied sinusoidal voltage. At these conditions and in this arrangement regular patterns of microdischarges between the two electrodes points are formed due to local charging of the dielectric surface. The cross-correlation spectroscopy setup enables the recording of microdischarge development for different phases of the applied voltage. Distinct differences in the microdischarge development between the subsequent phase channels in the positive half period can be observed, while the first channel shows similar behavior as in the single-microdischarge mode which was conducted recently.

A Composite of Metal and Polymer Films: Thin Nickel Film Coated on a Polypropylene Film after Atmospheric Plasma Induced Surface Modification

Polymeric films of high chemical stability and mechanical strength covered with a thin metallic film have been extensively used in various fields as electric and electronic materials. In this study, we have chosen polypropylene (PP) as the polymer due to its outstanding chemical resistance and good creep resistance. We coated thin nickel film on PP films by the electroless plating process. The surfaces of PP films were pre-treated and modified to increase the adhesion strength of metal layer on PP films, prior to the plating process, by an environment-friendly process with atmospheric plasma generated using dielectric barrier discharges in air. The surface morphologies of the PP films were observed before and after the surface modification process using a scanning electron microscope (SEM). The static contact angles were measured with deionized water droplets. The cross-sectional images of the PP films coated with thin metal film were taken with SEM to see the combined state between metallic and PP films. The adhesion strength of the metallic thin films on the PP films was confirmed by the thermal shock test and the cross-cutting and peel test. In conclusion, we made a composite material of metallic and polymeric films of high adhesion strength.

Surface Treatment of TiO2Electrode for Dye-Sensitized Solar Cells Using Low-Temperature and Low-Energy Dielectric Barrier Discharge in Air

A low-temperature and low-energy plasma surface treatment of nanoporous titanium oxide (TiO2) electrode for dye-sensitized solar cells (DSCs) is proposed using pulsed dielectric barrier discharge (DBD) under room air condition. When the treatment time is 10 min with the discharge voltage at 21.5 kV, the short-circuit current and the energy conversion efficiency are increased by 10% by the DBD treatment. The DBD treatment has advantages over previously studied plasma treatments of the TiO2 electrode of DSCs using a plasma jet or a low-pressure O2 plasma: (i) it requires no gas flow and no vacuum equipment, (ii) it is low-temperature treatment causing no damage on glass and plastic substrates, and (iii) it requires only a very low energy consumption. The DBD treatment is simple and cost-effective, having a strong potential for promoting the development of high-performance DSCs.

Surface Treatment of TiO2 Electrode for Dye-Sensitized Solar Cells Using Low-Temperature and Low-Energy Dielectric Barrier Discharge in Air

A low-temperature and low-energy plasma surface treatment of nanoporous titanium oxide (TiO2) electrode for dye-sensitized solar cells (DSCs) is proposed using pulsed dielectric barrier discharge (DBD) under room air condition. When the treatment time is 10 min with the discharge voltage at 21.5 kV, the short-circuit current and the energy conversion efficiency are increased by 10% by the DBD treatment. The DBD treatment has advantages over previously studied plasma treatments of the TiO2 electrode of DSCs using a plasma jet or a low-pressure O2 plasma: (i) it requires no gas flow and no vacuum equipment, (ii) it is low-temperature treatment causing no damage on glass and plastic substrates, and (iii) it requires only a very low energy consumption. The DBD treatment is simple and cost-effective, having a strong potential for promoting the development of high-performance DSCs.

A diffusive air plasma in bi-directional nanosecond pulsed dielectric barrier discharge

In this study, a diffuse dielectric barrier discharge in air is generated by a bi-directional nanosecond pulsed power supply using a needle–plate electrode configuration at atmospheric pressure. Time-resolved spectra of N2(C 3Πu → B 3Πg, 0–0, 337.1 nm) for both positive and negative pulse discharges are recorded under severe electromagnetic interference. It is found that the lagged time of the photocurrent pulse compared with the voltage pulse in the negative pulse discharge is about 50 times longer than that in the positive pulse discharge at 16 kV pulse peak voltage and becomes shorter with an increase in pulse peak voltage. In addition, the gas temperature of the air plasma is determined to be approximately 395 K by measuring the optical emission spectra of the first negative band of , 0–0, 391.4 nm).

Concentric-roll pattern in a dielectric barrier discharge in air

Concentric-roll pattern in a dielectric barrier discharge in air at pd value 29.3 hPa cm is observed in the presence of circular boundary and studied by an optical method for the first time. The weak correlation between microdischarges in concentric-roll patterns indicates that the concentric roll is a spatiotemporal chaos although the space integral of microdischarges is quasiperiodic in time. Spatiotemporal measurements of microdischarges suggest that the effective electric field near the boundary is weaker than that in the interior region. The bifurcation of concentric-roll patterns with the increase of voltage and selection of characteristic wavelength are also studied.

Modeling of ac dielectric barrier discharge

The qualitative electrodynamic field of the dielectric barrier discharge in air is studied by a three-component, drift-diffusion plasma model including the Poisson equation of plasmadynamics. The critical media interface boundary conditions independent of the detailed mechanisms of surface absorption, diffusion, recombination, and charge accumulation on electrode or dielectrics are developed from the theory of electromagnetics. The computational simulation duplicates the self-limiting feature of dielectric barrier discharge for preventing corona-to-spark transition, and the numerical results of the breakdown voltage are compared very well with data. According to the present modeling, the periodic electrodynamic force due to charge separation over the electrodes also exerts on alternative directions from the exposed to encapsulated electrodes over a complete ac cycle as experimental observations.

Effect of dielectric barrier discharge on semiconductor Si electrode surface

Electrode materials and shapes affected the discharge modes. Meanwhile, the discharge has influence upon electrode surface. In order to study the effect of discharge on semiconductor electrode, the experiments were carried out using single crystal Si wafer as high voltage electrode of atmospheric pressure dielectric barrier discharge in air. The effects of dielectric barrier discharge on Si electrode surface are analyzed by means of field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). The results show that surface roughness and oxidation increase with discharge time, while surface nitridation is not observed on Si electrode surface. It is different from Cu electrode. The difference is due to different chemical reactions between electrode surface and air plasma but could also be ascribed to the different analysis techniques used.

A comparative study of three different types of barrier discharges in air at atmospheric pressure by cross-correlation spectroscopy

Microdischarges in a barrier discharge with an asymmetric electrode arrangement (‘metal–dielectric’) were investigated with fine temporal (down to 10 ps) and spatial (down to 10 µm) resolution by the technique of cross-correlation spectroscopy. The discharge was operated in dry air at atmospheric pressure. The spatio-temporal distributions of the light intensities of the 0–0 transitions of the second positive (λ = 337.1 nm) and first negative (λ = 391.5 nm) systems of molecular nitrogen were compared with the corresponding experimental results for a symmetric electrode arrangement (‘dielectric–dielectric’) and for the coplanar barrier discharge. For all the discharge types being considered, the mechanism of electrical breakdown was found to consist of the Townsend pre-breakdown phase, the phase of ionizing wave propagation and the decay phase. Despite the qualitative similarity of the microdischarge development in different electrode arrangements, a detailed comparison of certain discharge characteristics (ionizing wave velocity, spatially or temporally integrated light intensity) enables us to reveal the influence of the electrode configurations on the process of electrical breakdown.

Treatment of PET and PU polymers by atmospheric pressure plasma generated in dielectric barrier discharge in air

Plasma treatments are frequently employed to modify surface properties of materials such as adhesivity, hydrophobicity, oleophobicity etc. Present work deals with surface modification of common commercial polymers such as polyethylene terephthalate (PET) and polyurethane (PU) by an air dielectric barrier discharge (DBD) at atmospheric pressure. The DBD treatment was performed in a plain reactor in wire-duct geometry (non-uniform field reactor), which was driven by a 60 Hz power supply. Material characterization was carried out by water contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The plasma-induced modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. The AFM analysis reveals that the plasma treatment roughens the material surface. Due to these structural and morphological changes the surface of DBD-treated polymers becomes more hydrophilic resulting in enhanced adhesion properties.

Effect of water adding on kinetics of barrier discharge in air

This work presents the results of theoretical and experimental studies on the effect of air humidity on the kinetics of plasma-chemical processes in a plasma-chemical reactor consisting of 16 volume barrier discharges and an 80 L volume working chamber. The component content of active species both in the discharge gap and in the working chamber was calculated under the conditions of the use of dry (RH = 20%) and wet (RH = 80%) ambient air, a specific discharge power of 1.5 W cm−3, a temperature of the gas medium in the discharge of 300–500 K and various residence times of the species in the discharge volume. The calculations were performed for the steady-state effective electric field in the discharge gap equal to 20 kV cm−1. It is found that, in spite of the difference between the rotational temperatures of nitrogen molecules in discharges in dry and wet air (≈400 K and ≈440 K, respectively), the best agreement between the calculations and the experiments for both the RH values is observed for the same calculated temperature of the gas medium in the discharge (≈425 K). In most cases, the calculated concentrations of O3, HNO3, HNO2, N2O5 and NO3 in the discharge gap and in the working chamber are in fairly good agreement with the respective measured data.

Atmospheric pressure glow discharge plasma in air at frequency 50 Hz

Homogeneous atmospheric pressure discharge using a dielectric barrier discharge in air at 50 Hz was investigated. Porous alumina ceramic sheets were used as a dielectric barrier. In this paper we compare the filamentary discharge initiated by using glass sheets as a dielectric and the glow discharge obtained by the porous alumina sheets as a dielectric.Generally, the discharge in a dielectric barrier arrangement consists of a large number of filaments. Using porous alumina sheets Al2O3, an atmospheric pressure glow discharge (APGD) plasma has been obtained. This APGD discharge is characterized by a homogeneous profile of long lifetime (∼5 ms) and the current is one pulse per half cycle of the power supply. The electrical measurements and the emission spectrum confirm that the discharge has been formed in the glow mode.

Development of a Barrier Discharge in Air in Highly Nonhomogeneous Electric Field Caused by the Residual Dielectric Surface Charges

The prebreakdown phases of a barrier discharge in a short gap in atmospheric-pressure air are investigated by numerical modeling. A highly nonhomogeneous electric field caused by residual charges deposited on the dielectric surfaces is taken into account. The simulation results of barrier discharge radiation are compared with experimental data.

Polyethylene Terephthalate Surface Modification by Filamentary and Homogeneous Dielectric Barrier Discharges in Air

In this paper, polyethylene terephthalate (PET) films are modified using nonequilibrium plasma generated by homogeneous dielectric barrier discharges (DBDs) in air at medium pressure, and the results are compared to those treated by using filamentary DBDs in air at atmospheric pressure. The characteristics of homogeneous DBDs are studied and compared with those of filamentary DBDs by measuring their electrical discharge parameters and observing their light-emission phenomena, and the surface properties of PET films before and after the treatments are studied using contact-angle and surface-energy measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy. It is found that the homogeneous DBD is quite homogeneous and stable in the whole gas gap, which differs from the filamentary DBD, and the plasma treatments modify the PET surface in both morphology and composition. The PET films modified in both treatments show a remarkable decrease in water contact and a remarkable increase in surface energy due to both the introduction of oxygen-containing polar groups onto the surface and the improvement in surface roughness. It is found that the homogeneous DBD is more effective in PET surface modification than the filamentary DBD as it can make the contact angle decline to a lower level by introducing more oxygen-containing groups, and the possible reason for this effect is discussed.

Influence of surface charges on the structure of a dielectric barrier discharge in air at atmospheric pressure: experiment and modeling

Dielectric barrier discharges (DBD) in air at atmospheric pressure and at low frequency are mainly constituted of thin transient plasma filaments (or microdischarges) with radii of a few hundreds of micrometers. In this work, we consider a point-to-plane geometry with the dielectric covering the plane electrode. Plasma filaments are initiated by streamers, starting from the high-field region close to the point electrode. The plasma filaments deposit charges on the dielectric plate which screen the electric field and lead to an extinction of the discharge filaments. In this work we experimentally demonstrate the synchronous start of several filaments in a time range of less than a few tens of nanoseconds and we show that the charges deposited on the dielectric have a strong impact on the discharge structure. This is validated using a simple electrostatic model. Then, the dynamics of the 2D streamer propagation in the gas gap and its interaction with the dielectric plane is calculated. The influence of space charges and surface charges on the discharge structure are discussed and compared with the experiment.

Effects of Airflows on Dielectric Barrier Discharge in Air at Atmospheric Pressure

Effect of airflow on the dielectric barrier discharge in ambient air at atmospheric pressure is presented. The influence of airflow on the spatial distribution and intensity of a discharge were investigated experimentally. A critical frequency of 1 kHz was found. With the frequency above 1 kHz, when a fast airflow was introduced into the discharge gap, the discharge patterns varied from filaments to curved stripes and the curvature degree rose with an increase in the airflow speed. At the same time, the discharge intensity decreased. However with the discharge frequency below 1 kHz, the discharge intensity would get greater with an increase in the airflow speed.