Air DBD Research Articles

Surface DBD in moist air for nitrogen fixation: a comparative study of pulsed versus amplitude-modulated AC powered discharge

Surface DBD (SDBD) discharge maintained in moist air in the immediate vicinity of the water surface is an effective source of reactive species for the production of plasma-activated water (PAW). In this work, we investigated the water activation process for two different DBD energization methods; i.e. using periodic HV pulses with nanosecond risetimes and amplitude-modulated HV AC. We combined UV–vis–NIR ICCD spectroscopy with electrical characteristics to determine the basic characteristics of SDBD microfilaments. Formation of N2O5/NO2/N2O/H2O2/NO2 −/NO3 − species was followed and the production yields of species generated in PAW (H2O2/NO2 −/NO3 −) were determined in a flow-through reactor under well-defined and stable discharge conditions. Both energization methods reached comparable energy efficiencies of nitrogen fixation in the range of 1–6 g kWh−1 with minimal concentrations of H2O2 (10 s μM). However, the AC-powered SDBD produced mainly NO3 − with minimal NO2 − (1/10 of NO3 −), while in the case of pulsed SDBD the better-balanced NO2 −/NO3 − ratio was achieved.

Inactivation of Diutina catenulata Isolated from Longan Fruit Using Atmospheric Pressure Cold Plasma DBD in Argon, Air, and Argon-Air Mixture

Inactivation of Diutina catenulata Isolated from Longan Fruit Using Atmospheric Pressure Cold Plasma DBD in Argon, Air, and Argon-Air Mixture

Atmospheric plasma treatment effect on shear strength of GFRP-Aluminum adhesively bonded lap joints

The objective of this study is to investigate the effect of air (dielectric barrier discharge) DBD plasma treatment on the bonding strength of adhesively bonded glass fiber-reinforced epoxy composite-aluminum lap joints. The bonding performance of lap joints produced by the plasma treatment was compared with that of untreated and peel-ply surface treatments. Water contact angles of the substrates were measured for untreated, peel-ply, and plasma surface-treated substrates. Experimental results showed that plasma-treated aluminum and GFRP substrates increased the wettability properties and thus shear strength of adhesively bonded GFRP-Al joints increased. After the shear tests, the fracture surfaces of the substrates were visually examined and three different damage modes were observed, including light fiber tear failure, adhesive failure, and thin layer cohesive failure modes.

Surface modification of nylon 6 by 50 Hz dielectric barrier discharge Produced in air and argon at atmospheric pressure

This paper reports the use of dielectric barrier discharge (15.65 kV, 50 Hz) produced in an air and argon environment at atmospheric pressure to modify the surface of Nylon 6. Power dissipation in air and argon DBD was determined to be 14.60 W and 12.00 W, respectively. Similarly, the average density and temperature of an electron in air DBD were found to be 1.74 ×1011 cm-3 and 1.31 eV, respectively, while the values were 2.50 ×1011 cm-3 and 0.68 eV in argon DBD. The water contact angle (WCA) was measured to confirm the enhancement in wettability. On treating the sample with air DBD for 15 minutes, the contact angle reduced from 134.07° ± 3.20° to 89.11° ± 3.06° while it was reduced to 82.74° ± 4.20° within 1 minute using argon. The study found that treating a hydrophobic sample of Nylon 6 with DBD for a certain period of time transformed it into a hydrophilic one, and extending the treatment time further enhanced its wettability. The use of argon DBD was found to be more effective than air DBD in altering the surface properties of the sample, as the sample became hydrophilic after only one minute of treatment with argon DBD and completely wettable after three minutes. The findings suggest that air and argon DBD have potential applications in modifying the surface properties of Nylon 6, which could have practical implications in the production of textiles, membranes, and other materials.

Atmospheric air and liquid-film DBD plasma using sine AC excitations for purpose of improving the hydrophilicity of PTFE

In this paper, the hydrophilic properties of PTFE were improved by using liquid-film DBD at atmospheric pressure and compared with air DBD. Results obtained indicate that the liquid-film DBD can produce more active species and have a more stable discharge pattern, and its gas temperature is only 450 K which is lower than that of air DBD (580 K). When the treatment time is 10 s, a water contact angle (WCA) of 65.3° was obtained after liquid-film DBD plasma treatment, which was much lower than that treated by air DBD plasma (75.1°). The liquid-film DBD plasma treated PTFE exhibited no damage with the increasing treatment time in the SEM analysis. Chemical analysis by FTIR and XPS spectrum for the untreated and liquid-film DBD modified PTFE did not show a change in their chemical structure and introduced more N- and O-containing functional groups on the PTFE surface. And this result was also verified by TEM/EDX.

Treatment of Polymeric Films Used for Printed Electronic Circuits Using Ambient Air DBD Non-Thermal Plasma.

This study aims to present the properties of the polymeric films after being subjected to DBD plasma treatment in atmospheric conditions. Three different commercial films of polyester (Xerox Inkjet transparencies and Autostat CUS5 Clear film) and polycarbonate (Lexan™ 8010 MC) have been considered for the tests. The surface wettability has been evaluated based on static water contact angle (WCA) for different treatment times varying between 0.2 s and 30 s, the results revealing a maximum WCA decrease compared to a pristine of up to 50% for Xerox films, 75% for Autostat and 70% for Lexan. The persistence of the hydrophilic effect induced by the plasma treatment has also been verified for up to 72 h of storage after treatment, the results indicating a degradation of the treatment effects starting with the first hours after the treatment. The WCA stabilizes to a value inferior to the one corresponding to pristine in the first 24 h after plasma treatment. The adhesion forces, as well as preliminary surface morphology evaluations have been determined for the considered films using atomic force microscopy (AFM). The adhesion forces are increased together with the prolongation of the plasma treatment application time, varying from initial values of 165 nN, 58 nN and 204 nN to around 390 nN, 160 nN and 375 nN for Xerox, Autostat and Lexan films, respectively, after 5 s of DBD treatment. For the considered materials, the results revealed that the plasma treatment determines morphological changes of the surfaces indicating an increase in surface roughness.

Degradation of Tattoo Inks by Cold Atmospheric Plasma Treatment: A Proof-of-Concept Study

Tattoos have been a part of the culture and a way of expression for a remarkable portion of society throughout history. However, different dissatisfactions related to tattoos lead people to tattoo removal procedures that can be carried out in various ways. Among them, laser tattoo removal is the most common technique. However, laser tattoo removal could have downsides; thus, novel technologies that either support or replace conventional methods are needed. In the present study, the degradation of red, yellow, green, blue, black and white tattoo inks by plasma treatment was evaluated for possible future use of cold plasma in tattoo removal. Tattoo inks were treated with DBD air plasma in the aqueous form and in the agarose gel. Furthermore, also tattoo pigments were exposed to plasma-treated water. The Kl-starch reagent was used to correlate the oxidative strength of plasma-treated water with the degradation of tattoo inks. Degradation of tattoo inks was determined by reflectance measurements and was measured as color change with respect to plasma treatment time. Color changes of tattoo inks were represented using the CIELAB color system and CIE xyY color space. Our results suggest that air DBD plasma treatment and plasma-treated water are capable of degrading tattoo inks. The color change of tattoo inks due to degradation by plasma was clearly distinguishable by the naked eye, and the maximum value corresponding to color change was measured for red tattoo ink.

The effects of the tube diameter on the discharge ignition and the plasma properties of atmospheric‐pressure microplasma confined inside capillary

With plasma penetration into a capillary and the assistant of an air DBD, an ac‐driven Ar microplasma plume having a length of several cm is generated inside the capillary. The inner diameter of the capillary ranges from 4 to 100 µm. When the tube diameter decreases, the length of the microplasma plume decreases, and while the ignition voltage, the current density, and the electron density increase significantly. For the tube diameter of 9 µm, the current density and the electron density measured from the Stark broadening of Hα line reach as high as 109 A m−2 and 11 × 1016 cm−3, respectively. The microplasma plume is of high degree of ionization and remains non‐thermal. Rather than monotonically increasing, the propagation velocity of the microplasma plume decreases and then keeps almost unchanged after the tube diameter reaches 20 µm.

Regeneration and purification of water-soluble cutting fluid through ozone treatment using an air dielectric barrier discharge

Abstract Cutting fluids are essential for cutting performance and rust prevention in metalworking processes. Among cutting oils, the usage of water-soluble cutting fluids is increasing rapidly because they afford excellent cooling performance and ensure fire safety. However, water-soluble cutting fluids also offer a favorable environment for the growth of a wide variety of microorganisms. The growth of microorganisms can lead to various problems such as deterioration of the cutting fluids and odor generation. Thus, technologies for purifying the waste of water-soluble cutting fluids are required. In this study, we developed an ozone treatment technology that uses an air DBD plasma system. Furthermore, sterilization experiments were performed with K. pneumoniae, P. aeruginosa, E. coli, and P. vulgaris as representative microorganisms. The system offers the advantages of low power consumption and simple structure. Approximately 1000 ppm of ozone could be stably generated under optimized conditions, and the ozone was injected into the reactor as micro-bubbles for improving reactivity and inactivation rate. The sterilization experiments confirmed that the water-soluble cutting fluid was sterilized by 99.99%. As a result, the turbidity, pH, and odor of water-soluble cutting fluid have been improved.

Study of a dielectric barrier discharge burner for plasma assisted combustion

In this short communication we report the results of measurements of the number densities of O3, NO and NO2 in the afterglow of a dielectric barrier discharge. Detailed modelling of plasma processes in a DBD is a challenging task and this data is necessary for verification of numerical model. The DBD in air produced only [O3] up to ~1016 cm-3 and [NO] up to ~5×1014 cm-3 that increased with discharge power linearly. In air fuel mixtures [O3] was an order of magnitude smaller, it decreased with [CH4]. In methane-air mixture NO was not detected, but [NO2] up to ~1015 cm-3 appeared instead.

The chemical product mode transition of the air DBD driven by AC power: A plausible evaluation parameter and the chemical behaviors

The chemical products of air plasma generated by dielectric barrier discharge were investigated in this paper, which played a key role in its applications. The results showed that the high applied voltage and low flow rate contributed a transition from ozone to nitric oxide mode. In order to investigate the relationship between the physical characteristic and a chemical product, the real energy density based on the ICCD image and Lissajous figure, a plausible parameter, was proposed. It was found that when the energy density increased beyond a critical value (∼10 mJ·cm−2), the mode transition occurred, which illustrated that the high value of energy density was favorable for the generation of nitrogen oxides but not for the ozone generation. The N2O density increased and the O3 density decreased at the flow rate of 480 L/h with the increase in energy density. When the flow rate was fixed at 60 L/h, the NO density increased with the increase in energy density while other parameters changed slightly and irregularly. The time required for the development of products in a closed cavity was also studied. It showed that the NO gradually disappeared and O3 slightly decreased as the time goes on. In this paper, it was proved that the real energy density, correlating the physical and chemical characteristics, was an effective parameter to distinguish the mode transition of the chemical products.

Effects of high voltage nanosecond pulsed plasma and micro DBD plasma on seed germination, growth development and physiological activities in spinach

In this study, we analyzed seed germination, seedling growth, and physiological aspects after treatment with high voltage nanosecond pulsed plasma and micro DBD plasma in spinach (Spinacia oleracea L.), a green leafy vegetable known to have low germination rate. Both germination and dry weight of seedlings increased after high voltage pulse shots were applied to spinach seeds. However seeds treated with many shots (10 shots) showed a decrease in germination rate and seedling growth. Seeds treated with air DBD plasma exhibited slightly higher germination and subsequent seedling growth than those treated with N2 plasma. Seed surface was degenerated after treated with high voltage pulsed plasma and micro DBD plasma but no significant difference in the degree of degeneration was observed among micro DBD plasma treatment time. Level of GA3 hormone and mRNA expression of an amylolytic enzyme-related gene in seeds were elevated 1 day after treatment with high voltage pulsed plasma. The relative amount of chlorophyll and total polyphenols in spinach seedlings grown from seeds treated with air DBD plasma was increased in 30 s, 1 min, and 3 min treatments. Taken together, our results suggest a possibility that plasma can enhance seed germination by triggering biochemical processes in seeds.

Characterization of Reactive Oxygen/Nitrogen Species Produced in PBS and DMEM by Air DBD Plasma Treatments

Characterization of Reactive Oxygen/Nitrogen Species Produced in PBS and DMEM by Air DBD Plasma Treatments

Atmospheric cold plasma process for vegetable leaf decontamination: A feasibility study on radicchio (red chicory, Cichorium intybus L.)

Cold plasma is an emerging non-thermal processing technology that could be used for large scale leaf decontamination as an alternative to chlorine washing. In this study the effect of an atmospheric cold plasma apparatus (air DBD, 15 kV) on the safety, antioxidant activity and quality of radicchio (red chicory, Cichorium intybus L.) was investigated after 15 and 30 min of treatment (in afterglow at 70 mm from the discharge, at 22 °C and 60% of RH) and during storage. Escherichia coli O157:H7 inoculated on radicchio leaves was significantly reduced after 15 min cold plasma treatment (−1.35 log MPN/cm2). However, a 30 min plasma treatment was necessary to achieve a significant reduction of Listeria monocytogenes counts (−2.2 log CFU/cm2). Immediately after cold plasma treatment, no significant effects emerged in terms of antioxidant activity assessed by the ABTS and ORAC assay and external appearance of the radicchio leaves. Significant changes between treated and untreated radicchio leaves are quality defects based on the cold plasma treatment. Atmospheric cold plasma appears to be a promising processing technology for the decontamination of leafy vegetables although some criticalities, that emerged during storage, need to be considered in future studies.

Plasma-Induced Degradation of Polypropene Plastics in Natural Volatile Constituents of Ledum palustre Herb

Polypropene (PP) plastics can be effectively degraded by natural volatile constituents from Ledum palustre catalyzed by atmospheric air dielectric barrier (DBD) plasma. The electron spin resonance (ESR) result indicates that the volatile constituents produce radicals in aerobic condition energized by power sources such as light, UV, plasma and so on. The degradation is a novel chemically oxidative way and it is initiated by a series of radical reactions. Lots of active and oxidative species, radicals, products and high energy electromagnetic field in plasma aggravate the degradation process. The results about PP maximum tensile strength (σbmax) confirm this conclusion. PP plastic heavily loses its extensibility, mechanical integrity and strength in a short time after suffering a synergetic treatment of the herb extract and air DBD plasma with no toxic residues left. The components of herb extract keep almost unchanged and may be reused. This study offers a new approach to manage and recycle typical plastics.

Stimulating living cells with air DBD plasma

ABSTRACTCells positioned at the bottom of a Petri dish were exposed, in a home-made plasma source, to pulsed Dielectric Barrier Discharges operated in air in order to investigate the effect of the plasma species on their viability and growth. Processes with different number of pulse, respectively 1,3,9 and 27 pulse, were performed to study the influence on viability and cell growth of two different cell lines, Saos 2 and NHDF. Atmospheric air discharges applied on the two selected cell lines have shown an effect strongly dependent on cell type. At certain doses we have measured increased activity of the NHDF fibroblasts cell line. On the other side, an inhibition of cell adhesion and growth on the Saos 2 osteoblastoma cell line, directly dependent on the plasma doses, was clear. This study shows that by properly tuning the dose of exposure of cells to air plasma it is possible to induce both positive and negative effects on cell growth, that would be useful in several branches of Medicine.

Discharge characteristic of nanosecond-pulse DBD in atmospheric air using magnetic compression pulsed power generator

Dielectric barrier discharge driven by repetitive nanosecond pulses can offer highly efficient non-thermal plasma at atmospheric pressure and is widely used for plasma applications. In this paper, the discharge is generated using a compact pulsed power generator based on one-stage magnetic compression. The output pulse can be up to 30 kV with a rise time of about 40 ns and a full width at half maximum of 70 ns. The electrical characteristics of the discharge parameters are studied by the measurement of voltage and current waveforms. The effects of applied voltage amplitude, voltage polarity, pulse repetition frequency, and barrier dielectric on discharge characteristics are investigated, respectively. The experimental results show that the discharge current, discharge power and electron density increase with the increase of the applied voltage, and the pulse repetition frequency has a slight effect on the electrical parameters. Moreover, the discharge current is influenced by the dielectric barrier, but it is not varied with the polarity of applied pulses.

The sterilization of Escherichia coli by dielectric-barrier discharge plasma at atmospheric pressure

The sterilization of E. coli (ATCC8099) using an atmospheric pressure, air DBD plasma driven by 100 Hz high-voltage power supply was investigated in this paper. The results showed that germicidal efficiency was closely related to the plasma treatment time, the gap spacing, the initial cell density and the surface characters of substrate materials. The germicidal efficiency was 99.999% under the conditions of 5-min plasma treatment, 3-cm gap spacing and on PET films. After plasma exposure for 5 min, the temperature was observed below 43 °C which could not lead to inactivate E. coli. The observation of protein leakage and cell morphology alteration by transmission electron microscopy (TEM) techniques revealed that the etching action on cell membrane by electrons, ions and radicals was primary reason of DBD air plasma sterilization.

The effect of discharge power density on polyethylene terephthalate film surface modification by dielectric barrier discharge in atmospheric air

Polyethylene terephthalate (PET) films are modified using non-equilibrium plasma generated by DBD in atmospheric air, and the effects of discharge power density on the surface modification are studied. It is found that increasing discharge power density can induce more effective treatment of PET films, because this leads to a faster decrease in water contact angle and a faster increase in surface energy due to more creation of polar groups and more obvious etching occurring on the PET surface. So the treatment time needed to achieve the same level of surface treatment can be reduced by increasing the discharge power density.

Surface Treatment of Polyethylene Terephthalate Films Using a Microsecond Pulse Homogeneous Dielectric Barrier Discharges in Atmospheric Air

Drived by a μs pulse high-voltage power supply, a homogeneous DBD in atmospheric air is generated between two plane-parallel electrodes, with PTFE plates as dielectric barriers. The discharge generated shows homogeneous discharge characteristics. The light emission is radially homogeneous and covers the entire surface of the electrodes, and a single current pulse with duration of about 1 s and amplitude of less than 1 A appears in each voltage pulse. The homogeneous DBD is used to treat the polyethylene terephthalate (PET) films to improve their surface hydrophilicity, and as the main operating parameters, the effects of discharge power density of the homogeneous DBD on the surface treatment are also studied. The surface properties of PET films before and after treatments are studied using the following: 1) contact angle and surface energy measurement; 2) attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR); 3) X-ray photoelectron spectroscopy (XPS); and 4) scanning electron microscopy (SEM). The results of contact angle and surface energy measurements reveal that the homogeneous DBD treatment can improve the surface hydrophilicity of PET films, as it can induce a remarkable decrease in water contact and a remarkable increase in surface energy. The results of SEM, XPS, and FTIR shows that improvement of the hydrophilicity due to both the introduction of oxygen-containing polar groups onto the surface and the etching of the surface. It is found that increasing discharge power density of homogeneous DBD can induce more effective treatment of PET films, and less treatment time is needed to achieve the same level of surface treatment by increasing the discharge power density.