Air Dielectric Barrier Discharge Research Articles

Quasi-stationary numerical model of the dielectric barrier discharge

Abstract The aim of this paper is to present a numerical algorithm for investigating the dynamic characteristics of a simple model of the dielectric barrier discharge in air. The proposed algorithm is based on the finite element method and is capable of determining the distribution of electric field intensity and space charge density in the point-plane geometry, when the plane is covered with a thin dielectric layer and the needle is energized with a sinusoidal voltage. The simulation results show the behavior of corona current and space charge density for a few values of the input voltage and frequency. The aim of this parametric study is to investigate the effect of voltage, and frequency on the time variation of the discharge.

Atmospheric pressure dielectric barrier discharges interacting with liquid covered tissue

The interaction of plasmas with liquids is of increasing importance in biomedical applications. Tissues treated by atmospheric pressure dielectric barrier discharges (DBDs) in plasma medicine are often covered by a thin layer of liquid, typically a blood serum like water with dissolved gases and proteins up to hundreds of micrometres thick. The liquid processes the plasma-produced radicals and ions prior to their reaching the tissue. In this paper, we report on a computational investigation of the interaction of DBDs in humid air with a thin water layer covering tissue. The water layer, 50–400 µm thick, contains dissolved O2aq (aq means an aqueous species) and alkane-like hydrocarbons (RHaq). In the model, the DBDs are operated with multiple pulses at 100 Hz followed by a 1 s afterglow. Gas phase reactive oxygen and nitrogen species (RONS) intersect the water-vapour saturated air above the liquid and then solvate when reaching the water. The photolysis of water by plasma-produced UV/VUV plays a significant role in the production of radicals. Without RHaq, , , and hydronium dominate the water ions with determining the pH. The dominant RONS in the liquid are O3aq, H2O2aq, and HNOxaq. Dissolved O2aq assists the production of HNO3aq and HOONOaq during the afterglow. With RHaq, reactive oxygen species are largely consumed, leaving an R·aq (alkyl radical) to reach the tissue. These results are sensitive to the thickness of the water layer.

Effects of dielectric barrier discharge in air on morphological and electrical properties of graphene nanoplatelets and multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) have been functionalized by dielectric barrier discharge (DBD) in air. The extent of functionalization of MWCNTs and GNPs reaches a maximum at the delivered discharge energy of 720 and 240Jmg−1, respectively. Further exposure to plasma leads to reduction of functional groups from the surface of the treated nanomaterials. It has also been demonstrated that DBD plasma does not produce dramatic structural changes in MWCNTs, while flakes of the treated GNPs become thinner and smaller in the lateral size. Conductive thin films, obtained by drop casting a solution of the treated nanomaterials in N-methyl-1-pyrrolidone on poly(methyl methacrylate) substrate, show significantly lower sheet resistance.

A Non‐thermal Plasma Seed Treatment Method for Management of a Seedborne Fungal Pathogen on Rice Seed

ABSTRACTSeeds contaminated with pathogens are the primary inoculum for plant diseases in many food crops. Conventional treatments for seedborne diseases use hot water, chlorine or fungicide applications. A novel seed treatment method based on non‐thermal plasma generated by an air dielectric barrier discharge (DBD) device was evaluated in this study as an alternative to these conventional treatments. The non‐thermal plasma at atmospheric pressure and room temperature consisted of partially‐ionized gases that are chemically reactive. The antimicrobial activity of non‐thermal plasma was evaluated against an important seedborne pathogen, Gibberella fujikuroi, that causes bakanae disease in rice. Non‐thermal plasma treatments effectively inhibited the growth of G. fujikuroi on nutrient growth medium and reduced the number of fungal colony forming units (CFU) on the rice seed surface by > 92% after 120 s exposure. Effective exposure times to 50% (ET50) and 90% (ET90) control of G. fujikuroi CFU on the seed surface were 9 and 76 s, respectively. Ten minutes of non‐thermal plasma treatment on seeds infested with G. fujikuroi significantly reduced disease development. No adverse effects were detected on the seedling emergence and height when non‐infested seeds were treated with non‐thermal plasma for up to 20 min. The treated seeds germinated and grew similarly compared with non‐treated non‐infested seeds. This study indicates that non‐thermal plasma had antifungal activity and showed potential as an effective disinfection technique to reduce the contamination of seedborne fungal pathogens from seed surfaces without compromising seed health.

Air DBD plasma treatment on three-dimensional braided carbon fiber-reinforced PEEK composites for enhancement of in vitro bioactivity

Surface treatment for bio-inert PEEK and its composites is required to broaden their applications in biomedical fields. In this work, a dielectric barrier discharge (DBD) plasma treatment in ambient air was performed on the surface of a three-dimensional braided carbon fiber-reinforced PEEK (C3D/PEEK) composite. The changes in surface chemistry and topography after DBD treatment were examined using water contact angle measurement, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Apatite formation on the DBD-treated C3D/PEEK composite was assessed using SEM after immersion in a simulated body fluid (SBF) to determine its in vitro bioactivity. It was shown that DBD plasma treatment led to a significant decrease in water contact angle, an increase in roughness and the creation of new oxygen related functional groups on C3D/PEEK composite. These changes were found to result in a significant improvement in its in vitro bioactivity. The results presented here clearly indicate that DBD plasma treatment in air is capable of modifying the surface of C3D/PEEK composite such that the treated surface changes from bio-inert to bioactive.

Investigation of Ozone Generation Performance by a Homogeneous Dielectric Barrier Discharge in Air and Oxygen at Atmospheric Pressure

Investigation of Ozone Generation Performance by a Homogeneous Dielectric Barrier Discharge in Air and Oxygen at Atmospheric Pressure

A study of flow induced by laser induced breakdown-enhanced dielectric barrier discharges in air

The flow induced by an asymmetric dielectric barrier discharge (DBD) actuator in air together with laser induced breakdown (LIB) near the exposed electrode is investigated using particle image velocimetry. In this approach, the electrodes, driven by alternating current (8 kHz, 14 kVp-p) serve primarily to accelerate the ions generated by the laser pulse (532 nm, 15 mJ per pulse, and 2 Hz). The mean velocity fields suggest that this hybrid scheme leads to a significant enhancement in the wall-jet velocity and momentum flux generated by actuation.

A Comparative Study of Water Electrodes Versus Metal Electrodes for Excitation of Nanosecond-Pulse Homogeneous Dielectric Barrier Discharge in Open Air

Atmospheric pressure low-temperature plasmas produced by dielectric barrier discharge (DBD) provide a promising approach for civilian application of pulsed power technology. In this paper, repetitive nanosecond pulses were generated using a magnetic compression solid-state pulsed power generator, and the rise time and pulse duration of the nanosecond pulse are ~30 and 70 ns, respectively. The DBD in open air is created using two kinds of electrodes, i.e., water and metal electrodes. The electrical, luminous, and optical characteristics of the DBDs under these two electrodes are studied and compared. The experimental results show that no filaments are observed and the discharge is homogeneous when water electrodes are used. The DBD still behaves in a filamentary mode when the discharge gap is extended to 4 cm in the case of metal electrodes. The results are validated by fast images taken by an intensified charge-coupled device camera. In addition, some discussion about the experimental results is presented. Improvement of discharge uniformity is due to the effect of resistive stabilization using water electrodes.

The removal of impurities from gray cotton fabric by atmospheric pressure plasma treatment and its characterization using ATR-FTIR spectroscopy

Gray cotton fabric shows hydrophobic characteristics due to presence of non-cellulosic impurities in outermost layers of cotton fiber. In the present study, atmospheric pressure plasma treatment for the removal of the non-cellulosic impurities from gray cotton fabric is investigated. Gray cotton fabric is treated with air dielectric barrier discharge at different time interval, and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Different species formed in plasma are identified using optical emission spectroscopy. The results clearly show that the plasma treatment improves wettability of gray cotton which is due to the removal of non-cellulosic impurities and due to the formation of polar carboxylate group. Removal of wax after plasma treatment is clearly reflected in ATR-FTIR spectra as disappearance of symmetric and asymmetric stretching of alkyl group at 2852.24 and 2917.81 cm−1. Further, ATR-FTIR spectroscopy provides a fast and satisfactory assessment of removal of impurities from cotton surface when untreated and plasma-treated cotton fabric is exposed to HCl vapor and subsequently spectra are collected. We observed a strong carboxyl peak is induced at 1749 cm−1 in case of untreated cotton. While for plasma-treated cotton fabrics substantial variation in the intensity of 1641 and 1749 cm−1 peak is observed with increase in plasma treatment time. The morphological changes observed by SEM are in accordance with ATR-FTIR results. The results are compared with conventionally (alkaline scouring) treated cotton fabric. The study reveals that atmospheric pressure plasma has potential to become dry and environment friendly process to improve wettability of gray cotton fabric.

Experimental Study of ZnO-Coated Alumina DBD in Atmospheric Pressure Air

An investigation on the discharge characteristic of a dielectric barrier discharge (DBD) device was carried out using bare and ZnO-coated alumina dielectric layer in atmospheric pressure air. Highly conductive ZnO film was first deposited on the alumina surface, and the characteristics of the dielectric barrier discharge were examined and compared. Experimental result shows that discharge behavior was definitely improved in the case of ZnO-coated dielectric barrier discharge. Relevant explanation is offered to describe its discharge physics.

Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure

In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3Πu→B3Πg 1–3) and N2 (C3Πu→B3Πg 0–2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

Kinetics of tomato peroxidase inactivation by atmospheric pressure cold plasma based on dielectric barrier discharge

Abstract Atmospheric pressure cold plasma technology is an emerging nonthermal food technology for microbiological decontamination of food and bio-materials. This study demonstrates the applicability of in-package cold plasma technology as a novel means to inactivation of enzymes. The kinetics of inactivation of tomato peroxidase as a model enzyme was studied at 30, 40 and 50 kV, for up to 5′ of atmospheric air dielectric barrier discharge plasma treatments. The enzyme activity was found to decrease with both treatment time and voltage, the former variable exhibiting a more pronounced effect. Kinetic models viz. first-order, Weibull and logistic models were fitted to the experimentally observed data to numerate the model parameters. The enzyme inactivation kinetics was found to be best described by the sigmoidal logistic function. Industrial relevance In-package cold plasma processing is a novel and innovative approach for the decontamination of foods with potential industrial application. This paper provides evidence for reduction of tomato peroxidase activity using cold plasma from a dielectric barrier discharge. It also demonstrates that the sigmoidal shaped logistic model adequately describes the enzymatic inhibition. The work described in this research is relevant to the processing of fruits, vegetables and their products, wherein enzyme activity leads to quality deterioration.

Characterization of millimetre magnitude atmospheric pressure streamer discharge in pin-to-plane dielectric barrier discharge

The streamer regime of pin-to-plane dielectric barrier discharge in air was studied by means of fast photography, electrical measurement and photoelectricity. The fast photographs of positive streamer were obtained by CCD camera with micro lens. The exposure time is one microseconds. The images illustrate that the streamer is non-axisymmetric because of some random factors, such as surface charge position, space charge distribution, gas liquidity and so on. In fact, the streamer propagates along bend discharge channel. The bending degree increases with the electric field strengthen. By surveying a mass of images, the diameter of streamer, height of surface charge effect and scope of surface charge was estimate used to describe the shape of streamer.

Ozone correlates with antibacterial effects from indirect air dielectric barrier discharge treatment of water

Ambient-condition air plasma produced by indirect dielectric barrier discharges can rapidly disinfect aqueous solutions contaminated with bacteria and other microorganisms. In this study, we measured key chemical species in plasma-treated aqueous solutions and the associated antimicrobial effect for varying discharge power densities, exposure times, and buffer components in the aqueous medium. The aqueous chemistry corresponded to air plasma chemistry, and we observed a transition in composition from ozone mode to nitrogen oxides mode as the discharge power density increased. The inactivation of E. coli correlates well with the aqueous-phase ozone concentration, suggesting that ozone is the dominant species for bacterial inactivation under these conditions. Published values of ozone-water antibacterial inactivation kinetics as a function of the product of ozone concentration and contact time are consistent with our results. In contrast to earlier studies of plasma-treated water disinfection, ozone-dependent bacterial inactivation does not require acidification of the aqueous medium and the bacterial inactivation rates are far higher. Furthermore, we show that the antimicrobial effect depends strongly on gas-liquid mixing following plasma treatment, apparently because of the low solubility of ozone and the slow rate of mass transfer from the gas phase to the liquid. Without thorough mixing of the ozone-containing gas and bacteria-laden water, the antimicrobial effect will not be observed. However, it should be recognized that the complexity of atmospheric pressure plasma devices, and their sensitivity to subtle differences in design and operation, can lead to different results with different mechanisms.

On the possibility of generating volume dielectric barrier discharge in air at atmospheric pressure

A homogeneous volume dielectric barrier discharge (DBD) in air at atmospheric pressure and natural humidity has been obtained. Conditions ensuring generation of a homogeneous DBD are described. It is shown that a determining influence on the homogeneity of DBD is produced by the rate of electric field strength growth in the discharge gap.

Effect of Particle Size on Silver Nanoparticle Deposition onto Dielectric Barrier Discharge (DBD) Plasma Functionalized Polyamide Fabric

AbstractThe effect on the deposition of three different size silver nanoparticles (AgNPs) onto a polyamide 6,6 (PA) fabric pre‐treated using air dielectric barrier discharge (DBD) plasma was investigated. The SEM, EDS, and XPS analysis confirm that the smaller is the diameter of AgNPs, the higher the amount of adsorbed NPs on the PA. The DBD treatment on PA induces a threefold increase in Ag adsorption. The result confirms a dual effect on the wettability of the plasma treated PA substrate. AgNPs slightly enhance hydrophobicity of the PA surface and, at the same time, protect it against the plasma aging effect. magnified image

Silver incorporation on viscose and cotton fibers after air, nitrogen and oxygen DBD plasma pretreatment

Dielectric barrier discharge (DBD) pretreatments in air, nitrogen and oxygen plasma of viscose and cotton fabrics with subsequent immobilization of silver were studied. Surface activation of treated fibers was evaluated through subsequent sorption of silver from aqueous AgNO3 solution, after which changes in the surface morphology were monitored and quantity of silver deposition on fabric was measured. The plasma treatment was done in volume DBD discharge with the gap distance between electrodes of 0.5 and 2 mm. Depending on the gas used in pretreatment, significant difference in the way silver bonds to the textile surface was found. Nitrogen plasma pretreatment with gap distance of 0.5 mm led to the homogeneous fiber coating by silver nanoparticles with average size up to 300 nm estimated by SEM, while fibers treated in oxygen plasma adsorbed silver in a form of ions. The plasma pretreatment in air leads to changes that contain features of fibers treated in both nitrogen and oxygen DBD plasma. Distinct difference of used configuration of the plasma source is a use of gap distance 0.5 mm, which is in order of textile thickness. Observed results allow us to report a new way how to immobilize silver nanoparticles onto textile fibers using plasma pretreatment with subsequent sorption of silver from aqueous solution.

ABOUT INCREASE OF EFFICIENCY OF PLASMA MULTI-ACTUATOR SYSTEM FOR BOUNDARY LAYER CONTROL

The numerical simulation of spatial-periodic systems of electrogasdynamic actuators (plasma actuators), using the dielectric barrier discharge (DBD) for a volumetric force impact on a gas flow was carried out. Both the typically used design of actuators and the advanced design with an additional screening electrode are considered. The mathematical model of the dielectric barrier discharge in air was formulated in the drift-diffusion approximation without accounting for convective transfer of the charged particles. The following volumetric reactions are taken into consideration, namely, the ionization of nitrogen and oxygen by electron impacts, the attachment of electrons to oxygen, the detachment of electrons from negative ions, and the ion-ion and the electron-ion recombination. The two types of boundary conditions were considered at the open dielectric surface, namely, the model of instantaneous recombination and the model of finite rates of recombination and electron desorption. The numerical simulation both for the typical and for the advanced actuator systems was done with the same set of problem parameters. It was shown that the advanced scheme provides the better energy efficiency of the system of DBD actuators. It was also found that the main integral characteristics of the DBD actuator weakly depend on the type of boundary conditions used on the dielectric surface. The new simplified design of a system of DBD actuators was proposed.

Formation of hydrophobic coating on PMMA surface using unipolar nanosecond-pulse DBD in atmospheric air

Abstract Dielectric barrier discharge (DBD) can modify the material surface and result in complicated physical and chemical reactions to improve the surface hydrophilicity, which is proved to be an effective method for surface modification. Compared with the traditional ac-excitation DBD, the DBD using unipolar pulses can avoid local overheat of microdischarges and can improve discharge efficiency under some conditions. In this paper, DBD excited by repetitive unipolar nanosecond generator was used to improve the hydrophobicity of Plexiglass (PMMA) surface by means of the interaction between air plasma and silicone oil. The output voltage had a rise time of 40 ns and a full width at half maximum of about 70 ns. The surface hydrophobicity of the PMMA, before and after the surface modification, was evaluated via the contact angle measurement under different experimental conditions. The values of the contact angle shown in this paper were the average of eight measured values, and the standard deviations were also calculated. The surface energy including polar and dispersion components was calculated using the measured average contact angles of distilled water and polyethyleneglycol. The results showed that, as the increase of the discharge voltage, the contact angle increased but the surface energy decreased. With the increase of treatment time, the water contact angle of the modified surface increased at the beginning, and it would reach to a maximum at 7.5 min treatment, and then decreased. The effect of pulse frequency on the modification results was different at various treatment times. In addition, the possible physical and chemical reaction among the DBD plasma, silicone oil and the PMMA surface was discussed.

G. stearothermophilus Spores' Inactivation by a Single Dielectric Barrier Discharge in Air at Atmospheric Pressure

In this paper, we present some results of a plasma source developed at the Plasma Laboratory of the University of Brasilia for sterilization studies at atmospheric pressure. This source was primarily conceived to produce a corona-type discharge to be used on pollutant control experiments. We used ordinary air as the precursor gas. Our apparatus consists of two coaxial cylindrical tubes with different radii connected to a high-voltage power source. We used G. stearothermophilus spores as the biological indicators. We counted the viable spores after the exposure to the plasma with the pour plate technique. Finally, we studied the biocide mechanisms of the plasma and related the inactivation of the microorganisms to plasma-induced chemical and physical processes.