Pressure Dielectric Barrier Discharge Research Articles

Importance of plasma discharge characteristics in plasma catalysis: Dry reforming of methane vs. ammonia synthesis

Plasma catalysis is a rapidly growing field, often employing a packed-bed dielectric barrier discharge plasma reactor. Such dielectric barrier discharges are complex, especially when a packing material (e.g., a catalyst) is introduced in the discharge volume. Catalysts are known to affect the plasma discharge, though the underlying mechanisms influencing the plasma physics are not fully understood. Moreover, the effect of the catalysts on the plasma discharge and its subsequent effect on the overall performance is often overlooked. In this work, we deliberately design and synthesize catalysts to affect the plasma discharge in different ways. These Ni or Co alumina-based catalysts are used in plasma-catalytic dry reforming of methane and ammonia synthesis. Our work shows that introducing a metal to the dielectric packing can affect the plasma discharge, and that the distribution of the metal is crucial in this regard. Further, the altered discharge can greatly influence the overall performance. In an atmospheric pressure dielectric barrier discharge reactor, this apparently more uniform plasma yields a significantly better performance for ammonia synthesis compared to the more conventional filamentary discharge, while it underperforms in dry reforming of methane. This study stresses the importance of analyzing the plasma discharge in plasma catalysis experiments. We hope this work encourages a more critical view on the plasma discharge characteristics when studying various catalysts in a plasma reactor.

Surface activation of viscose textiles via air, argon, and oxygen dielectric barrier discharge plasma: Influence of peak voltage

Abstract This paper discusses the use of atmospheric pressure dielectric barrier discharge (DBD) plasma treatment to enhance the surface qualities of viscose fabrics. The study explores the effects of different plasma gases, discharge voltages, and exposure times on the treated fabrics. The findings emphasize the importance of optimizing the plasma's peak voltage to achieve desired surface treatment outcomes. The document also presents data on color strength, wettability, color fastness, and tensile strength of the treated fabrics, as well as SEM analysis of surface morphology and chemical analysis using FTIR and EDX. The results show that treatment at a peak voltage of 11.83 kV is more efficient, except for the tensile strength which is enhanced at a peak voltage of 8.92 kV. The oxygen plasma treatment significantly improves the color strength, which exhibits an increase from 11 to 18. The intensified color was attributed to the significant influence of electrostatic interactions between the charged hydroxyl groups of the oxygen plasma treated viscose textiles and the dye molecules, which enhance the printability. The oxygen dielectric barrier discharge plasma exhibits a higher ability to enhance the properties of textiles when compared to air and argon plasmas. This study presents a sustainable, economical, secure, and ecologically friendly approach to explore new fabrics for specific uses.

Tailoring the structural, morphological, surface wettability and hardness features of Makrofol HS for surface applications: effect of DBD treatment

ABSTRACT In current research, Makrofol HS polymeric films have been utilized to evaluate the alterations in the surface properties under an atmospheric-pressure dielectric barrier discharge (DBD) plasma source. Upon DBD plasma exposure with various exposure durations ranging from 10 min to 120 min, the structural, surface wettability, surface free energy, surface roughness, and hardness features of Makrofol HS films have been studied and analyzed using different techniques. The FTIR spectra demonstrated that small changes in the band intensities correspond to the C-O-C as well as C=O bonds. Further, the changes in the absorption bands are correlated to the treatment time, leading to two critical processes, degradation, and crosslinking. The results of surface wettability displayed that the liquids' contact angle decreased from 84 ± 3o, 77 ± 3o and 62 ± 2o for water, glycerol, and dimethyl to 45 ± 1o, 42 ± 1o, and 36 ± 1o for untreated and treated samples at the highest treatment time, respectively. Also, the surface free energy significantly amended with increasing plasma exposure time. This modification in the treated surface indicates the increase in the polar groups on the treated surfaces, which then become hydrophilic surfaces. The samples' surface roughness parameters Ra, Rq, and Rz increased from 0.057 ± 0.003, 0.084 ± 0.004 and 0.366 ± 0.02 mm for untreated samples to 1.463 ± 0.073, 1.707 ± 0.085, and 6.839 ± 0.34 mm for treated samples at the highest treatment time, respectively. The Vickers hardness measurements showed an increase in the Vickers hardness from 12.31 ± 0.61 kgf/mm2 for the untreated sample to 44.89 ± 2.24 kgf/mm2 for the treated sample at the highest duration.

Dynamics of NO, N2O, and ONOOH in atmospheric-pressure air dielectric barrier discharge: decoupling energy density and gas temperature effects varying with discharge voltage

The dose regulation of reactive nitrogen species is crucial for biomedical applications. In this study, we develop a global chemical kinetics model comprising 92 species and 1018 reactions to investigate the regulatory dynamics of three types of reactive nitrogen species, i.e. NO, N2O, and ONOOH, which vary with the discharge voltage in an air coaxial dielectric barrier discharge. Based on the experimental results, the model can describe the density variations of NO, N2O, and ONOOH. The simulation results indicate that the O, NO3− , NO2− , and O3 are essential intermediate species related to NO generation; N, NO2, O-, N2*, and O(1D) are essential intermediate species related to N2O generation; and O2− , NO, NO2, OH, O4− , and O3 are essential intermediate species related to ONOOH generation. The individual and comprehensive effects of the energy density and gas temperature on the densities of NO, N2O, and ONOOH and the corresponding intermediate species are quantified under increasing discharge voltages. The simulation results indicate that the energy density is the primary factor affecting the number density of NO, N2O, and ONOOH, whereas the gas temperature exerts a completely different effect on these three species. These insights are valuable for plasma applications in biomedicine, where the selective and controlled production of reactive nitrogen species is key for achieving the desired plasma performance.

Spatially differentiated crystalline inorganic coatings deposited by an atmospheric pressure dielectric barrier discharge with immobilized filaments

The one-step deposition of spatially differentiated crystalline vanadium oxide coatings (V2O5) using an atmospheric pressure dielectric barrier discharge is reported. This feasibility study uses an original combination of immobilized filaments inside the plasma and an inductive heating device. Preliminary results show that thick crystalline deposits are achieved under the immobilized filaments, whether the interfilament spacing leads to much thinner deposits, with a different chemical composition. The gas flow inside the reactor, combined to the filament reactivity, leads to local depletions of reactants.

Rapid Synthesis of Noble Metal Colloids by Plasma-Liquid Interactions.

The interactions between plasma and liquids cause complex physical and chemical reactions at the gas-liquid contact surface, producing numerous chemically active particles that can rapidly reduce noble metal ions. This study uses atmospheric-pressure surface dielectric barrier discharge (DBD) plasma to treat ethanol aqueous solutions containing noble metal precursors, and stable gold, platinum, and palladium colloids are obtained within a few minutes. To evaluate the mechanism of the reduction of noble metal precursors by atmospheric-pressure surface DBD plasma, the corresponding metal colloids are prepared first by activating an ethanol aqueous solution with plasma and then adding noble metal precursors. It is found that the long-lived active species hydrogen peroxide (H2O2) plays a dominant role in the synthesis process, which has distinct effects on different metal ions. When HAuCl4 and H2PdCl4 are used as precursors, H2O2 acts as a reducing agent, and AuCl4- and PdCl42- ions can be reduced to metallic Au and Pd. However, when AgNO3 is the precursor, H2O2 acts as an oxidising agent, and Ag+ ions cannot be reduced to obtain metal colloids because metallic Ag can be dissolved in H2O2 under acidic conditions. A similar phenomenon was also observed for the preparation of Pd colloid-PA with a plasma-activated ethanol aqueous solution using Pd(NO3)2 as a Pd precursor.

Degradation of dyes using reactive species of atmospheric pressure dielectric barrier discharge formed by a pencil plasma jet

The dye degradation efficacy of the cold plasma pencil jet is presented in the present investigation. Dye degradation studies were performed using air plasma, six different types of selected dyes (erythrosine, metanil yellow, sudan I, crystal violet, rhodamine B, and Indigo). The degradation of dyes is analyzed using UV visible spectroscopy, total organic carbon, and chemical oxygen demand. The results showed complete degradation of all types of dyes in UV visible analysis with minimum time for indigo (3 min) and maximum time for erythrosine (45 min). Moreover, erythrosine (k = 1.08 mg l−1 min−1), sudan I (k = 3.46 mg l−1 min−1), rhodamine B (k = 3.955 mg l−1 min−1), and Indigo (k = 18.915 mg l−1 min−1) follows approximate zeroth-order degradation kinetic, and metanil yellow (k = 0.094 min−1) and crystal violet (k = 0.25 min−1), closer to first-order degradation kinetics. Additionally, a substantial enhancement in mineralization and reduction in chemical oxygen demand of all the dyes occurs after plasma treatment. In this study, air plasma is produced in the cylindrical coaxial dielectric barrier discharge configuration. Electrical characterization of plasma is performed and the plasma species are identified using optical emission spectroscopy. The toxicity of plasma degraded dyes solutions toward freshwater algae species (Chlorella Sorokiniana and Chlorella Pyrenoidosa) are significantly low compared to virgin dyes solutions. The study reveals that pencil plasma jet substantially degrades dyes as well as converts the dyes solutions non-toxic.

Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films

In this study, the DBD plasma reactor has been constructed, characterized, and tested to be employed in material treatment for use in different applications. A neon power source with an output of 10 kV, 30 mA, with a frequency of 20 kHz is used to drive the DBD reactor in an atmospheric-pressure environment. The investigation covered the analysis of many parameters of the dielectric barrier discharge (DBD) reactor, including its discharge voltage, current, capacitance, consumption energy, and the light emission of the produced plasma. Also, to examine the generated DBD plasma effect, the photoemission, optical, and electrical characteristics of untreated/treated polycarbonate films were investigated using photoluminescence spectroscopy, UV/Vis spectroscopy, and electrical spectroscopy. The results demonstrated the appearance of two modes in the DBD discharge: filamentary and homogeneous. Moreover, the DBD reactor's power consumption has been measured to be 20 mW at a supplied voltage of 6.5 kV peak-to-peak, operated in atmospheric–pressure. The photoluminescence emission results emphasized that the treated films are modified particularly with increasing DBD treatment time. The UV–Vis spectra demonstrated a notable displacement of the absorption edge towards higher wavelengths as the duration of DBD exposure increased. This is indicative of the reduction of the band gap energy, thus improving the electric conductivities. The optical parameters of the treated polycarbonate films were enhanced in comparison to the untreated sample. Through the used frequency range, measurements of dielectric loss, dielectric constant, as well as AC electrical conductivity, are sensitive parameters to the modifications in electrical behaviors due to DBD plasma treatment.

Ammonia synthesis using atmospheric pressure fluidized bed plasma

In recent years, extensive research has been conducted on ammonia synthesis using catalysts under mild conditions and by combining plasma with the catalysts. Increasing the contact area between the catalyst surface and atmospheric pressure dielectric barrier discharge (DBD) is crucial for improving the ammonia synthesis efficiency. In this study, we present a fluidized bed dielectric barrier discharge (FB-DBD) method that can be used to form FB-DBD plasma through the electrohydrodynamics of DBD discharge without a feed gas. We performed ammonia synthesis experiments using our FB-DBD reactor. The results indicate that the FB-DBD plasma can achieve an energy yield of 5.9 g-NH3/kWh, which is about twice higher than that of conventional DBD plasma. Consequently, it can be implemented in various applications as a new reaction field between solids and gases where surface reactions are predominant.

Spatio-temporal dynamics of electrons and helium metastables in uniform dielectric barrier discharges formed in He/N2

A uniform atmospheric pressure dielectric barrier discharge is operated in helium with an admixture (0.45%) of nitrogen. The discharge is ignited in the gas gap between a driven and a grounded electrode and propagates along the dielectric surface outside the gap. Plasma conditions are characterised with current and voltage measurements and by application of absolutely calibrated optical emission spectroscopy, with a focus on nitrogen molecular emission. Plasma parameters, namely electron density and reduced electric field, are determined with spatial and temporal resolution in the frame of a collisional-radiative model using a calibrated charge coupled device camera and Abel inversion of measured images. The density of an effective helium metastable state is calculated using the measured plasma parameters and compared with values of the state density measured with tunable diode laser absorption spectroscopy.

Evolution of the electrical characteristics of an atmospheric pressure dielectric barrier discharge system over one hour operation

In this work, long-time operation of a dielectric barrier discharge (DBD) characterized by a single thin dielectric was investigated. The discharge was operated under nitrogen at atmospheric pressure in a typical filamentary regime. Electrical measurements were performed, i.e. applied voltage, current and charge were retrieved. The Lissajous figure method combined with an equivalent circuit of the DBD was used to calculate the dissipated power, estimate the gas gap voltage , evaluate the deposited charges as well as the capacitances of the discharge cell. The results over a one-hour operation indicated that the total dissipated power remained constant, but a decrease of the gas gap voltage with an increase of the charge deposited was also depicted. For the capacitances, both dielectric and cell capacitances variations were studied from the Lissajous figures. The dielectric capacitance showed a voltage dependency over half a period of applied voltage.

Investigation of the Change in Hydrophobicity of Polycarbonate in Atmospheric Pressure Dielectric Barrier Discharge (APBDB) Generated with a 50 Hz Power Supply

Dielectric Barrier Discharge (DBD) of disc electrodes with diameter 5 cm and thickness 1 cm of each has been used for treatment of the samples. The discharge was produced at fixed inter-electrode gap of 4.5 cm for the study of effectiveness of treatment on the surface of the Polycarbonates (PCs). After the treatment in varying time periods the hydrophobic properties of sample changed to the hydrophilic. To investigate the effect of plasma treatment, contact angle was measured by using goniometer with water as a testing liquid. Effect on the sample due to treatment time, applied voltage and working gas were studied. Treatment carried out in Argon environment produced better wettability compared to atmospheric air. Aging effect was also studied to see the evolution of the wettability after time elapsed by measuring the contact angle up to one month after the treatment. Contact angle was increased from 39.35° C to 56.4° C, which was still very lower than the contact angle 81.2° of untreated sample.

Enhancing microorganism inactivation performance through optimization of plate-to-plate dielectric barrier discharge cold plasma reactors

Atmospheric pressure dielectric barrier discharge cold plasma (CP) is an effective method for inactivating microorganism contamination. However, improving CP inactivation efficiency as affected by CP reactor parameters still remains unstudied. In this study, the effects of discharge voltage, dielectric material and dielectric thickness of CP reactor on inactivation performance were investigated, and their influence mechanisms on plasma discharge were discussed. Results indicated that efficiency was improved using the reactor parameters of a high discharge voltage (17 kV) with a centre frequency (10 kHz) and a high dielectric constant (ceramic) with a small dielectric thickness (1 mm), resulting in higher electron number density and electric field strength, producing more reactive substances for enhancing microorganism inactivation. Under the above conditions, CP treatment for 4 min inactivated 99.6% of Salmonella typhimurium and 96.1% of Listeria monocytogenes. It is hoped that this work could guide the design of commercial CP systems.

Dielectric barrier discharge as bipolar ion source for aerosol charging: Application to filtration, thin film, and aerosol size measurement

We have investigated the potentialities of dielectric barrier discharges (DBD) for aerosol electro-processing with a special focus on ion production and aerosol charging for deposition (filtration and materials) and aerosol measurement tools. The advantages and drawbacks of aerosol injection downstream or upstream of the discharge are compared according to the application. The main parameters that control ion production and transport are investigated based on post-discharge ion current measurements. Post-DBD aerosol chargers are compared for submicron particle size measurements based on aerosol bipolar charging and electrical mobility analysis. Finally, the principle of counterflow extraction of bipolar ion from an atmospheric pressure DBD is established from upstream measurements of positive and negative ion fluxes in air, without neither ozone (<0.1 ppmv) nor nanoparticles.

Preface

5th International eConference on Frontiers in Materials Engineering and nanoTechnology [ICF-MET-2023] has been held on May 05 – 06, 2023 by Shri Yashwantrao Patil Science College Solankur India. The aim was to provide the common platform for students, professors, researchers and industrialist to present their recent research in the field of Materials Science; Materials Engineering; Mechanical Engineering; Metallurgy; Nanotechnology; Metals, alloys and compounds; Nanofabrication; Properties of Materials; Synthesis, characterization and applications of Materials; Advances in Nanotechnology. It aims at the interaction of knowledge of current and future innovation in the above mentioned field for societal needs. The pandemic situation has taught human beings a lot and now the time to work towards it with new technological ideas. 5th ICF-MET-2023 provides the bridge to fill up the gaps that were essentially found during the pandemic.The response from the scientific community was excellent. The organizers received 95 abstracts; out of which 25 abstracts were rejected. Remaining authors were called to join the conference and share the knowledge with the peers in the field. The five invited talks were arranged where peers from various well known institutions such as KAUST Saudi Arabia; The New College Shivaji University Kolhapur; The LNM Institute of Information Technology Jaipur; Kathmandu University Nepal; participated and all of the participants gave the oral presentations.On the day first, opening ceremony, keynote speech, invited talk and oral presentations took place. Dr. Gholap Sandeep, Senior Scientific Researcher, King Abdullah University of Science and Technology (KAUST), Catalysis Centre, Saudi Arabia gave the keynote on “Iridium Single Atom Catalyst in Glycerol Conversion to Lactic Acid”. It was then followed by an invited talk by Dr. Yadav JB, Scientific Officer, Shivaji University Kolhapur on “Hydrogen a Green Energy Source: Challenges and Opportunities”. The next invited talk was given by Prof (Dr) Subedi DP, Professor of Physics, School of Science, Kathmandu University, Nepal on “Surface Treatment of Handwoven Fabrics by Atmospheric Pressure Dielectric Barrier Discharge”. Then participants gave the oral presentations as per the schedule.The day second was started with the invited talk by Dr. Ashok Chougale, The New College, Shivaji University Kolhapur, India on “Eco-Friendly Nanomaterials: Advancements in Drug Delivery and Wastewater Treatment”. The next invited talk was held by Dr. Unune Deepak, The LNM Institute of Information Technology, Jaipur on “Machining of difficult-to-cut materials using hybrid electrical discharge machining processes: Variants, Capabilities and Research Prospects”. It was further followed by the oral presentations by the participants. At the end, the valedictory ceremony was taken wherein the best presentation awards were also declared.The organizing committee acknowledge the financial and moral support from the Patrons - Hon. A. Y. Patil – Founder & Secretary, SVSPM Solankur; Hon. R. Y. Patil – Chairman, SVSPM Solankur.Beside, we are grateful to Dr. Ashok Chougale, Dr. Vishal More and Dr. Nilesh Pawar, The New College Kolhapur for their expertise and technical assistance.The organizing committee members have taken lot of efforts for this conference.Chairman – Dr Chougale GG;Convener – Dr Patil RB;Coordinator – Dr Tamboli SH;Secretary – Dr Jatratkar AA.The organizers thank all the participants, committee members, experts, reviewers and institute management authority for their mutual understanding and support during the journey of 5th ICFMET-2023. Finally, we would like to take this opportunity to thank the Editorial of IOP: JPCS for their assistance in publishing this issue.

Effects of plasma treatment on surface insulation properties of epoxy composites

The surface of epoxy composite material working in DC electric field for a long time is easy to accumulate charge and cause flashover, which seriously reduces its insulation level and poses a threat to the safe operation of electrical equipment. In this study, SiO x films were deposited on the surface of nano-SiO2/ER nanoparticles by atmospheric pressure dielectric barrier discharge plasma vapor deposition technology using ethyl nor-silicate as a precursor. The effects of different deposition time on the deposition effect and the pressure level of the film surface were studied. Scanning electron microscope and atomic force microscope were used to characterize the surface morphology of the material, and the flashover voltage before and after deposition was measured. The results show that SiO x films of different thicknesses can be formed on the surface of the material at different times of plasma deposition. After extending the deposition time of the film, the film becomes more uniform and dense, the surface roughness of the material decreases continuously, and the electrical conductivity and flashover voltage along the surface increases continuously. After 10 min plasma treatment, the conductivity increased from 1.78×10−16 S to 2.3×10−13 S, while the flashover voltage along the surface increased from 19.29 kV to 22.66 kV, an increase of about 17.5%.

Conversion of carbon dioxide in atmospheric pressure dielectric barrier discharges with different electrode configurations

The choice of electrode configuration and dielectric material is critical to the discharge process and plasma characteristics of a dielectric barrier discharge (DBD) reactor. In this study, a new electrode configuration of DBD reactor with copper mesh as electrode inserted between dielectrics is proposed, which has a much higher capacitance than the conventional double-dielectric layer DBD reactor. Two materials with different relative dielectric permittivities, alumina and zirconia, are chosen as dielectrics for an experimental comparison of CO2 decomposition. The experimental results show that the conversion rate of CO2 for the reactor with copper mesh inserted between dielectrics are higher than that of the corresponding double dielectric layer reactor under the same discharge power, and the conversion rate of CO2 with zirconia as a dielectric material is higher than the case of alumina as a dielectric. Further analysis of discharge characteristics shows that for the reactor with copper mesh inserted between dielectrics, the applied voltage required for discharge is significantly reduced, the amount of transferred charge is significantly increased, and the number of micro-discharge current pulses as well as the average lifetime during a single voltage cycle are also considerably increased, leading to an increase in the CO2 discharge efficiency and conversion rate.

Electrical and optical characteristics of radio-frequency atmospheric dielectric barrier discharge using anodic alumina barriers

It is widely accepted that dielectrically insulated electrodes can control plasma contraction in radio frequency atmospheric pressure glow discharge at very large currents. It is also known that thin dielectric barriers maximize the permissible discharge current, thus boosting the reactive plasma species and enhancing the application efficacy. An experimental investigation of radio-frequency atmospheric pressure dielectric barrier discharge (rf APDBD) using a thin layer of a novel dielectric, anodic alumina grown by a wet electrochemical process to insulate electrodes is presented in this paper to demonstrate that rf APDBD with anodic alumina barriers remains stable and retains volume without contraction over a wide current range in the γ-mode. The electrical characterization of the rf APDBD is performed using an equivalent electric circuit model based on the measured electrical parameters. In normal glow discharge, the measured impedance data closely matched the simulated data. Optical emission spectroscopy demonstrated that a higher discharge current facilitated active plasma chemistry. The estimated excitation, vibrational, and gas temperatures indicate that rf APDBD with anodized electrodes is well suited for surface treatment and decontamination applications in open air.

A Boltzmann Electron Drift Diffusion Model for Atmospheric Pressure Non-Thermal Plasma Simulations

We introduce a fluid computational model for the numerical simulation of atmospheric pressure dielectric barrier discharge plasmas. Ion and neutral species are treated with an explicit drift diffusion approach. The Boltzmann relation is used to compute the spatial distribution of electrons as a function of the electrostatic potential and the ionic charge density. This technique, widely used to speed up particle and fluid models for low-pressure conditions, poses several numerical challenges for high-pressure conditions and large electric field values typical of applications involving atmospheric-pressure plasmas. We develop a robust algorithm to solve the non-linear electrostatic Poisson problem arising from the Boltzmann electron approach under AC electric fields based on a charge-conserving iterative computation of the reference electric potential and electron density. We simulate a volumetric reactor in dry air, comparing the results yielded by the proposed method with those obtained when the drift diffusion approach is used for all charged species, including electrons. We show that the proposed methodology retains most of the physical information provided by the reference modeling approach while granting a substantial advantage in terms of computation time.

Spatio‐temporal distributions of accumulated charge density in atmospheric pressure dielectric barrier discharges

AbstractThe effect of the secondary electron emission coefficient on accumulated charge density distributions in atmospheric pressure dielectric barrier discharges have been simulated using two‐dimensional fluid model. Spatio‐temporal distributions of accumulated charge density on each side of the dielectric have been examined. The differences of conventional waveforms of accumulated charge density and the simulated results were clarified. And when the dielectrics were negatively accumulated, charges were uniformly accumulated, while positive charges were not. Randomness of streamers' occurrence, and self‐organized structures have been also examined by the accumulated charge distributions.