Dielectric Barrier Discharge Plasma Research Articles

Electro-optical characterization of a novel surface DBD plasma actuator operating in typical gas rarefaction conditions of near-space applications

The present work provides an experimental investigation of a novel surface dielectric barrier discharge plasma actuator consisting of a 0.3 mm-thick alkali-free quartz substrate as dielectric barrier material and titanium-tungsten electrodes. The device is manufactured using ultraviolet lithography and CMOS processes, and experiments are conducted under sinusoidal plasma actuation in a vacuum chamber with pressure ranging from 20 kPa to 0.01 Pa. Intensified high-speed visualizations of the plasma discharge and electrical signals (current/voltage/power) define the diagnostic toolbox. Results highlight that at 20 kPa the plasma discharge is driven by the formation of micro sparks on the inner edge of the exposed electrode, propagating downstream in larger current structures. At 1 kPa, the plasma discharge becomes more glow-type with negative current regimes longer than the positive ones, while the voltage signals preserve their sinusoidal shape. In such a plasma regime, the discharge extends over the entire region covered by the electrodes, suggesting the use of larger grounded electrodes to further enlarge the actuation region. Furthermore, the momentum action of the plasma discharge is not anymore unidirectional as it acts on the whole device plane. At pressure between 50 Pa and 2.5 Pa, the plasma discharge is unstable exhibiting a fast modification of the plasma discharge. Below 2.5 Pa, it becomes a volumetric full glow-type, extending its action mainly upstream with a higher plasma density on the exposed electrode. The establishment of the new plasma regime at a pressure below 2.5 Pa affects the electrical dissipated power and asymmetry of voltage and current signals.

Effects of oxygen species in perovskite catalysts on the partial oxidation of methane in a low temperature plasma bed

Lanthanum-based perovskites have been employed as catalysts for the partial oxidation of methane in a dielectric barrier discharge plasma bed at ambient temperature. The reaction performance could be improved when a perovskite catalyst and non-thermal plasma were simultaneously used. X-ray photoelectron spectroscopy (XPS) analysis determined that the surface oxygen species of the perovskite catalysts were found to play a crucial role. During the activity tests, methane conversion, H2 selectivity, and CO selectivity of LaAlO3 were 12.3%, 20.9%, and 26.3% higher than those obtained in a test with α-Al2O3. To elucidate the effects of the lattice oxygen transfer capability on the performance further, Sr-doped LaAlO3 catalysts were also investigated. Owing to the enhanced O2 transfer capability, the H2 selectivity was significantly improved (increased by 18.3%), and the CO selectivity was slightly higher (increased by 1.9%) than that of the original LaAlO3. Density functional theory calculations were also performed to identify the active intermediate species and elucidate the reaction pathways, including the rate-determining step. LaAlO3 showed smaller activation energy (1.54 eV) than that of α-Al2O3 (2.89 eV) at rate-determining step, which demonstrated higher catalytic activity of LaAlO3.

The changed multiscale structures of tight nut (Cyperus esculentus) starch decide its modified physicochemical properties: The effects of non-thermal and thermal treatments

Non-thermal dielectric barrier discharge plasma (DBDP) and four thermal treatments, including baking (BT), high pressure cooking (HPC), radio frequency (RF) and microwave (MW) were applied to modify the structural and physicochemical properties of Cyperus esculentus starch (CES). The results showed that the thermal treatments remarkably disordered the crystalline structures of CES through weakening the double-helix conformation of amylopectin, while DBDP caused much more gentle influence on the starch structures than them. Specifically, MW induced the high-frequency displacement of polar molecules and intensive collisions between starch and water molecules, causing the largest stretching and swelling extents of amylopectin, resulting in the highest pasting and rheological viscosity of CES in four thermal treatments. As DBDP did not favor the aggregation of amylopectin chains, the deaggregated starch chains promoted the hydration effects with water molecules, boosting the final pasting viscosity, apparent rheological viscosity, freeze-thaw stability and digestion velocity of CES. Besides, the gelatinization-retrogradation process in the thermal treatments regulated starch digestion velocity and produced type III resistant starch in CES. Conclusively, the modified physicochemical properties of CES resulted from the altered molecular structures of starch by the applied treatments.

Inhibitory effects of non-thermal atmospheric plasma on Yersinia enterocolitica and Staphylococcus aureus in the Korean traditional non-fermented kimchi “Geotjeori”

Food-borne bacteria have frequently been detected in kimchi, a representative and traditional fermented ethnic food of Korea. This study investigated the effect of atmospheric dielectric barrier discharge (DBD) plasma treatment (1.1 kV, 43 kHz, N2: 1.5 m/s, 5–60 min) on reduction of Yersinia enterocolitica and Staphylococcus aureus and on quality parameters in Geotjeroi, a non-fermented kimchi. A decrease of 0.12/0.09, 0.19/0.19, 0.34/0.45, 0.64/0.72, and 1.13/1.12 log10 CFU/g was observed by 5, 10, 20, 30, and 60 min of DBD plasma, respectively. D-value of 52.83 and 51.95 min was determined for Y. enterocolitica (R2 = 0.99) and S. aureus (R2 = 0.98) using the first order kinetics model. The quality parameters (pH, Brix, and hardness) were not significantly different (P > 0.05) between treated and untreated Geotjeori. Moreover, a decrease of >1 log10 CFU/g, for both bacteria was observed without any change in the quality of Geotjeori. These findings imply that DBD plasma treatment enhances Geotjeori safety and protects product from microbial risk.

Treatment with Dielectric Barrier Discharge (DBD) plasma restricts Aspergillus niger growth isolated from wheat grain

Microbiological contamination by fungi impacts the quality and safety of wheat grain storage. This study aimed to evaluate the efficacy of cold plasma in restricting the growth of the fungus, Aspergillus niger, which was isolated from wheat grains. A dielectric barrier discharge (DBD) operating at atmospheric pressure generated cold plasma that was used to treat the fungus, and the impact of this treatment was investigated at various periods 1, 2, 4, 6, and 15 minutes. The results revealed a highly significant decrease in the growth and number of spores of Aspergillus niger compared to the controls. This study revealed an efficient technique for enhancing wheat grain storage that could be a foundation for further large-scale studies.

Effect of Plasma-Enhanced Low-Temperature Chemistry on Deflagration-to-Detonation Transition in a Microchannel

This study examines low-temperature chemistry (LTC) enhancement by nanosecond dielectric barrier discharge (ns-DBD) plasma on a dimethyl ether (DME)/oxygen (Ar) premixture for deflagration-to-detonation transition (DDT) in a microchannel. It is found that non-equilibrium plasma generates active species and kinetically accelerates LTC of DME and DDT. In situ laser diagnostics and computational modeling examine the influence of the ns-DBDs on the LTC of DME and DDT using formaldehyde () laser-induced fluorescence (LIF) and high-speed imaging. Firstly, high-speed imaging in combination with LIF is used to trace the presence of LTC throughout the flame front propagation and DDT. Then, competition between plasma-enhanced LTC of ignition and reduced heat release rate of combustion due to plasma-assisted partial fuel oxidation is studied with LIF. Observations of plasma-enhanced LTC effects on DDT are interpreted with the aid of detailed kinetic simulations. The results show that an appropriate number of ns-DBDs enhances LTC of DME and increases formation and low-temperature ignition, accelerating DDT. Moreover, it is found that, with many ns-DBDs, concentration decreases, indicating that excessive discharges may accelerate fuel oxidation in the premixture, reducing heat release and weakening shock–ignition coupling, inhibiting DDT.

Feasibility and mechanism of recycling carbon resources from waste cyanobacteria and reducing microcystin toxicity by dielectric barrier discharge plasma

Recycling carbon resources from discarded cyanobacteria is a worthwhile research topic. This study focuses on the use of dielectric barrier discharge (DBD) plasma technology as a pretreatment for anaerobic fermentation of cyanobacteria. The DBD group (58.5 W, 45 min) accumulated the most short chain fatty acids (SCFAs) along with acetate, which were 3.0 and 3.3 times higher than the control. The DBD oxidation system can effectively collapse cyanobacteria extracellular polymer substances and cellular structure, improve the biodegradability of dissolved organic matter, enrich microorganisms produced by hydrolysis and SCFAs, reduce the abundance of SCFAs consumers, thereby promoting the accumulation of SCFAs and accelerating the fermentation process. The microcystin-LR removal rate of 39.8% was obtained in DBD group (58.5 W, 45 min) on day 6 of anaerobic fermentation. The toxicity analysis using the ECOSAR program showed that compared to microcystin-LR, the toxicity of degradation intermediates was reduced. The contribution order of functional active substances to cyanobacteria cracking was obtained as eaq− > •OH > 1O2 > •O2− > ONOO−, while the contribution order to microcystin-LR degradation was eaq− > •OH > •O2− > 1O2 > ONOO−. DBD has the potential to be a revolutionary pretreatment method for cyanobacteria anaerobic fermentation.

Applications in Biomedicine and Fabrication Using Plasma and Nanomaterials

A comprehensive analysis of the individual plasma characteristics and the physical processes involved in the organization of nanoscale solid-state systems throughout a wide spectrum of elemental composition, structural configuration, and dimensionality is presented here. As a result of these phenomena, it may be possible to localize and regulate matter and energy at the nanoscale and to create self-organized nanosolids with exceptional and unique properties. The introduction of a unified conceptual framework that is based on the regulation of the creation, transport, and self-organization of precursor species is followed by the explanation of a number of plasma-specific nonequilibrium and kinetics-driven phenomena that occur over a wide range of temporal and geographical scales. When the plasma is brought down to dimensions of micrometers and nanometers, new emergent phenomena come into play. Examples include chirality-controlled single-walled carbon nanotubes, semiconducting quantum dots and nanowires, ultra-fine manipulation of graphenes, nanodiamonds, and organic matter, as well as nanoplasma effects and nanoplasmas of various states of matter. Over the last several years, there has been intense research into the use of plasma medicine. Due to the vast range of cancer cell selectivity, treating every form of cancer is still a challenging endeavor for medical professionals. Plasma jets and dielectric barrier discharges are two examples of the many varieties of nonthermal plasma devices that have been developed as a result of research in more sophisticated forms of plasma physics. When nonthermal plasma is brought into contact with biological material, a great number of charged particles and reactive species are produced. The primary components consist of plasma ultra-violets, reactive nitrogen species, and reactive oxygen species. These species may be employed alone or in combination with nanomaterials in a variety of biomedical applications that aim to improve human health. They may also be used in the synthesis of nanomaterials with physiological significance. Several different biomedical applications are described in relation to the synergy that may be achieved between plasma and nanomaterials in this study, along with new developments in plasma-based synthesis of physiologically relevant nanomaterials.

Dielectric barrier discharge plasma treatment of catalysts and the effect on isomerised rice bran oil

SummaryDielectric barrier discharge (DBD) plasma is an emerging technology applied in multiple industries in recent years. In this work, DBD plasma was used instead of a traditional heating activation catalyst and applied in the field of rice bran oil (RBO) conjugation. Linoleic acid (LA) in rice bran oil generated a series of compounds with π‐double bonds at the basic site of the catalyst and finally shed with the catalyst to produce conjugated linoleic acid (CLA). Ru‐Pd/USY was prepared by the primary wet impregnation method, and Ru‐Pd/USY was treated at a power of 180 W, a discharge time of 150 s and an electrode spacing of 2.5 cm. The Ru‐Pd/USY morphology and internal composition were analysed by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The catalyst was isomerised with RBO in a supercritical CO2 environment, and the conversion of linoleic acid (LA) in Pd‐Ru/USY RBO after DBD treatment reached 67.4 ± 0.8%, and the finished oil met the edible standard.

Optimization of Discharge Plasma Reactor for Dry Reforming of Methane using Response Surface Methodology

This research provides a study of the dry reforming of methane (DRM), which converts two main greenhouses gases (CO2 and CH4) to synthesis gas (H2 and CO) by a Dielectric Barrier Discharge (DBD) plasma reactor at atmospheric pressure. The Box-Behnken Design (BBD) method based on the Response Surface Methodology (RSM) was applied to determine the optimum experimental conditions on the plasma stability and the synthesis gas production. The synergistic effects of input power (P), CO2/CH4 ratio (R), and flow rate (FR) on the CO2, CH4 conversions, H2, CO yields, and the syngas ratio of H2 to CO were studied. With the desirability value of 0.97, the optimum values of 10.05 W (P), 1.03 (R), and 1.58 L.min−1 FR were identified with CO2 conversion of 48.56% and CH4 conversion of 86.67%; H2 and CO yields of 45.87% and 39.43% respectively; and syngas ratio of H2 to CO of 0.88. The study shows that both P and FR have a major significant effect on the reactant conversions and syngas ratio, followed by R. Meanwhile, the value of R has a significant impact on the H2, CO yields followed P and FR. In contrast, the synergistic effects between P-R, P-FR, and R-FR had a weak significant on the CO2 and CH4 conversions, H2 and CO yields, and H2 to CO ratio respectively. The quadratic term coefficients of P, R, and FR had a remarkable effect on all responses. Thus, the synergistic effect of the most important parameters improves the process efficiency. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Tailoring of Mg and MgLi thin-film corrosion rates with dielectric barrier discharge plasma treatment

Magnesium and magnesium alloys such as magnesium-lithium are of great interest for the application as biodegradable implants. To control the degradation, a tailoring of the corrosion rate is needed. In this study, the effect of a short (5–20 s) dielectric barrier discharge plasma treatment in ambient air on the corrosion rate of magnetron sputtered Mg and MgLi thin films is presented. The treatment with atmospheric plasma of as sputtered samples leads to a decrease of the corrosion rate of 45%−50% in Hanks’ balanced salt solution. The higher corrosion resistance is influenced by a change in surface structure and a formation of an MgCO3 containing film.

Dielectric barrier discharge plasma-modified chitosan flocculant and its flocculation performance

The flocculation performance of chitosan can be enhanced by grafting modification to overcome its disadvantages of poor water solubility. In this study, chitosan was modified by dielectric barrier discharge plasma and polymerized with acrylamide and aluminum chloride to synthesize a new chitosan-based flocculant, namely, chitosan–acrylamide–aluminum chloride (CA-PAC). After optimizing the synthesis conditions of CA-PAC, the best conditions were as follows: discharge time of 3 min, discharge power of 50 W, polymerization temperature of 60 °C, polymerization time of 3 h, total monomer concentration of 100 g/L, and m(AlCl3):m(CA) ratio of 2:1. Characterization was performed through SEM, XPS, FTIR, XRD, TG and 1H NMR. Results showed that the preparation of CA-PAC was successful. The influences of flocculant dosage, pH, and stirring intensity on flocculation efficiency were investigated. The removal efficiency of turbidity was 94.1 %. The investigation of the flocculation mechanism revealed that CA-PAC mainly relied on charge neutralization or the synergic action of electric neutralization, bridging, and roll–sweep under acidic and neutral conditions, but it depended on the joint action of adsorption bridging and net sweeping under alkaline conditions. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

Preparation of rGO/NiO nanocomposites by AC and nanosecond pulsed DBD

Graphene/transition metal oxide composites combine the energy-storing mechanisms of pseudo-capacitance and double layer capacitance, and are considered as preferred electrode materials for supercapacitors. For the composites' complex structure and components, it is important to develop a method with good controllability to monitor the structure and component of the nanocomposites, which is critical for the electrochemical performance optimization and the further industrial application. In this paper, graphene oxide (GO) and nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O) were used to prepare reduced graphene oxide/nickel oxide (rGO/NiO) nanocomposites utilizing dielectric barrier discharge (DBD) plasmas with AC and nanosecond (ns) pulse power supplies. The scanning electron microscope (SEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) are used to study the nanocomposites created under various discharge conditions. It shows the splitting and delamination of the prepared composites surface, a rise in ID/IG, and the reduction of GO after plasma treatment result in an excellent connection with the electrode material surface and electrolytic solution, and good capacitor performance. The rGO/NiO nanocomposites prepared by AC DBD have better charge transfer resistance, conductivity, and electrochemical capacitance retention rate than the materials prepared by ns pulsed DBD, which is analysed by power deposition and thermodynamics. The work contributes to reveal the mechanism of plasma material preparation, which will give new impetus to the development of environmental-friendly method for electrode materials preparation.

Construction of g-C3N4/Fe-MOFs Type-Ⅱ heterojunction promotes photo-Fenton degradation of doxycycline

A type-II heterojunction photo-Fenton catalyst g-C3N4/Fe-MOFs was synthesized with the utilization of waste PET by dielectric barrier discharge (DBD) plasma. The coupling of Fe-MOFs enhanced the visible-light absorption regions of g-C3N4, and induced the formation of type-II heterojunction, which inhibited the recombination of photo-generated electrons and holes. g-C3N4/Fe-MOFs exhibited a much higher photo-Fenton catalytic performance, which was 4.42 and 3.30 times higher than that of g-C3N4 and Fe-MOFs for the degradation of doxycycline (DOX), respectively. The enhanced photo-Fenton catalytic performance could be attributed to the synergistic electron transfer interface between g-C3N4 and Fe-MOFs, thus inhibiting the recombination of photo-generated electrons and holes. The possible mechanism of photo-Fenton degradation of DOX with g-C3N4/Fe-MOFs was proposed based on the radical trapping experiments, as well as the characterization of EPR and Mott-Schottky. This research could provide an efficient and green method for the utilization of waste PET and the treatment of antibiotic wastewater.

Highly effective removal of perfluorooctanoic acid (PFOA) in water with DBD-plasma-enhanced rice husks

Adsorption is regarded as an efficient method to eliminate per- and polyfluoroalkyl substances from an aqueous solution. In the present investigation, an adsorbent based on rice husks (RHs) was successfully prepared by phosphoric acid (PA) activation and dielectric barrier discharge (DBD) plasma treatment, and it was used to adsorb perfluorooctanoic acid (PFOA) from water. The electrodes employed in the experiment were planar type. This research investigated RH surface properties and adsorption capacity before and after modification using DBD plasma. The results revealed that the He–O2 plasma modification introduced oxygen-containing functional groups and increased the PFOA removal efficiency. Increasing the oxygen content and total gas flow rate to 30 vol.% and 1.5 L/min, respectively, with 10 min of RH plasma treatment time at 100 W plasma discharge power enhanced the PFOA removal efficiency to 92.0%, while non-treated RH showed the removal efficiency of only 46.4%. The removal efficiency of the solution increased to 96.7% upon adjusting the pH to 4. The adsorption equilibrium isotherms fitted the Langmuir model, and the adsorption kinetic followed the pseudo-second-order model. The maximum adsorption capacity was 565 mg/g when the Langmuir isotherm model was applied.

Compensation of Heat Effect in Dielectric Barrier Discharge (DBD) Plasma System for Radar Cross-Section (RCS) Reduction.

In this study, the problems encountered in radar cross-section (RCS) measurement experiments utilizing a dielectric barrier discharge (DBD) plasma system are examined and an effective solution is proposed. A DBD plasma system generates heat due to the high bias voltage required for plasma generation. The thermal-induced structural deformation of the DBD structure caused by this high voltage and its impact on RCS measurements are analyzed. In addition, techniques for minimizing the thermal-induced deformation and compensation methods for addressing the minimized deformation are proposed. Furthermore, RCS measurements are conducted on two kinds of DBD structures using the proposed method to experimentally demonstrate the improved agreement between the simulation and measurement results. For both structures, the RCS experimental results are in very good agreement with the simulation results, which enables accurate plasma characterization. In conclusion, it can be expected that the proposed method can be used to provide more accurate RCS measurements on various DBD structures that generate high heat.

Intervention mechanisms of cold plasma pretreatment on the quality, antioxidants and reactive oxygen metabolism of fresh wolfberries during storage

Fresh wolfberries, a nutritious “super fruit”, face limited marketing potential due to storage difficulties. This study aimed to enhance their storage stability using dielectric barrier discharge plasma (DBD) pretreatment and investigate the intervention mechanism. The results indicated that the optimal condition of DBD pretreatment for fresh wolfberries was 13.64 kV, 70 s and 2.7 kHz, which extended their shelf from 2 to 5 d at room temperature. This pretreatment reduced decay, weight loss, and firmness reduction by inactivating microorganisms and inhibiting respiration. Additionally, the decline of phenols, flavonoids, ascorbic acid, and antioxidant activity was inhibited, while maintaining high content of polysaccharides, titratable acid, and carotenoids. Interestingly, moderate DBD treatment produced reactive oxygen species (ROS) that triggered the defense response of wolfberries' ROS metabolism system and promoted the biosynthesis of flavonoids, thereby enhancing resistance to decay. The findings offer new insight into plasma effects on fruits and vegetables.

Effects of spark dielectric barrier discharge plasma on water sterilization and seed germination

This study investigated the effects of spark dielectric barrier discharge (SDBD) plasma on water sterilization and seed germination using an in-situ treatment method. The plasma diagnostics used I–V characteristics and optical emission spectroscopy. The electron, rotational, and vibrational temperature, as well as electron density were measured. The findings revealed that SDBD plasma treatment caused significant changes in the physicochemical properties of the liquids. In addition, the concentrations of H2O2, NO2− and NO3− were increased after 8 min of plasma treatment to 30, 40, and 100 mgL−1, respectively. The effectiveness of the SDBD plasma treatment was evaluated based on bacterial inactivation and seed germination. After 8 min of plasma treatment, an almost complete removal of E. coli and S. aureus was achieved. Furthermore, the germination of coriander seeds was enhanced when they were treated with SDBD plasma for 5 min. SDBD plasma shows promise for water sterilization, seed germination, and sustainability.

Highly effective CO2 splitting in a plasma-assisted membrane reactor

Membrane reactors offer a promising approach to converting CO2 into chemicals, fuels, and value-added products. However, challenges remain in its high energy input and deactivation of the catalyst. Here, we report a breakthrough strategy that uses dielectric barrier discharge (DBD) plasma to enhance the CO2 splitting in a perovskite-based La0.6Sr0.4Co0.5Fe0.5O3-δ (LSCF) membrane reactor where a traditional catalyst is not required however instead relies on the highly reactive species generated by the CO2 plasma. The CO2 conversion, physical and chemical evolution of membranes at different temperatures, CO2 plasma power, and purging gas were systematically investigated. The maximum CO2 conversion was achieved at 800 °C and 25 W while reaching 10.6%, 20.0%, and 28.0% via helium, complete oxidation of methane, and partial oxidation of methane purging on the permeate side, respectively. The experimental results obtained under low plasma power consumption suggest that the plasma-assisted membrane reactor strategy has the potential to be energy-efficient and sustainable, particularly when combined with renewable energy sources.

Effect of Atmospheric Cold Plasma on the Aroma of Pineapple Juice: Improving Fresh and Fruity Notes and Reducing Undesired Pungent and Sulfurous Aromas

Pineapple aroma is characterized by several esters, which confers its fresh and fruity aroma. However, high concentrations of methyl hexanoate and thioesters bring an undesired pungently sweet aroma and sulfurous notes to pineapple juice. This study investigates the chemical effects of cold plasma on the aroma compounds and descriptors of pineapple juice, evaluating the effects of plasma on its esters and thioesters. Dielectric barrier discharge plasma was applied to pineapple juice, varying the excitation frequency (50 to 1000 Hz) and processing time (10 to 20 min) at constant voltage (20 kV). Plasma treatment induced successive demethylation of esters and the conversion of methyl esters into ethyl esters. Thioesters showed to be more stable under plasma treatment. Proper setting of plasma operating conditions enabled an improvement in the fresh and fruity descriptors of pineapple juice, a reduction of its undesired pungently sweet aroma, but an increase in the influence of sulfurous descriptors. Plasma treatment at 50 Hz reduced the undesired aromas of pineapple while maintaining its fresh and fruity descriptors.