Glow Dielectric Barrier Discharge Research Articles

Influence of Cold Plasma Processing on the Stability of Phenolic Compounds of Araça-Boi (Eugenia stipitata) Juice

Knowledge of the chemical changes caused during plasma treatment is essential to enhance food quality. In this work, the influence of two cold plasma technologies, dielectric barrier discharge plasma and glow discharge plasma, on the phenolic profile of araça-boi (Eugenia stipitata) juice was investigated and assessed by gas chromatography coupled to mass spectrometry. Eight phenolic compounds were identified in araça-boi, with cinnamic acid being the major phenolic compound of the fruit juice, followed by protocatechuic acid. The effects of excitation frequency and plasma flow rate were evaluated because these are the main operating conditions that can be set for plasma treatments. The phenolic profile slightly changed due to the reaction of the phenolics with the reactive plasma species produced during the treatment, with the highest increase in phenolic content observed in the dielectric barrier discharge plasma operating at 1000 Hz. Both plasma systems increased the bioavailability of phenolic compounds in the juice, which could be increased by up to 201% using the dielectric barrier discharge plasma. Plasma application increased the concentration of cinnamic, hydrocinnamic, benzoic, and p-coumaric acids. Overall, plasma treatment improved the bioavailability of the phenolic compounds and resulted in slight changes to the phenolic profile of araça-boi juice. Thus, the technology showed a positive effect on araça-boi juice. This work advanced our further understanding of the changes induced by cold plasma treatment on phenolic compounds and characterization of araça-boi (Eugenia stipatata).

Influence of atmospheric and vacuum plasma processing on the organic composition of araça-boi (Eugenia stipitata) juice

Cold plasma is a novel non-thermal technology that is still under development. Cold plasma treatment of food products induces a wide range of chemical changes in food compounds, several of which can improve nutritional quality. Understanding the chemical changes caused during plasma treatment is essential to enhance food quality and avoid the formation of undesired compounds. This investigation addressed the influence of two cold plasma technologies, glow discharge plasma and dielectric barrier discharge plasma, on the organic composition of araça-boi (Eugenia stipitata) juice, which is rich in sugars, organic and amino acids. The chemical composition of the juice was assessed by 1H nuclear magnetic resonance coupled with chemometrics. The effects of excitation frequency, processing time, and plasma flow rate were investigated. Glow discharge plasma and dielectric barrier discharge plasma application tended to decrease the concentration of glucose (33%), fructose (31%), malic acid (25%), and amino acids while increasing sucrose content (23%). Overall, plasma processing changed the juices’ alcohol, sugar, and amino acids content, primarily by reducing the concentration of cysteine (33%), alanine (42%), and methionine (43%). However, the dielectric barrier discharge plasma tended to slightly increase the amino acid content (up to 9%) when operating at 200 Hz.

Comparative study of two cold plasma technologies on apple juice antioxidant capacity, phenolic contents, and enzymatic activity

Cold plasma technologies are being developed as an alternative to thermal processes aiming toward preservation while retaining or improving several quality parameters. This research evaluates the use of dielectric barrier discharge (DBD) plasma and glow discharge plasma on browning enzyme activity, antioxidant capacity, and total phenolic content of apple juice. This work evaluated the effects of the main DBD plasma operating conditions, such as excitation frequencies (50–900 Hz), and glow plasma discharge operating conditions, such as air plasma flow rates (10–30 ml/min) and processing time (10–30 min). Both plasma systems partially inactivated the enzymes polyphenol oxidase and peroxidase and consequently increased apple juice's total phenolic content and antioxidant activity. DBD plasma technology presented better efficacy in increasing apple juice's total phenolic content and antioxidant capacity. DBD plasma and glow discharge plasma have the same effectiveness in inactivating browning enzymes in apple juice. Novelty impact statement This work compares two cold plasma technologies for apple juice processing. The results showed that different plasma technologies lead to different outcomes and that the right choice of technology should be made for a given goal.

Experimental research on closed plasma discharge and spectral diagnosis excited by high voltage and high frequency power supply

This paper proposes a design for developing a closed plasma generator based on the low-pressure multilayer dielectric barrier discharge and glow discharge, and the discharge excited by the high-voltage and high-frequency power supply. The closed plasma generator forms the core equipment for the application of closed plasma stealth technology. The traditional plasma stealth experiments are intended for generating the plasma in the vacuum chamber. The discharge experiment has been carried out in two closed discharge chambers with dimensions 8 × 8 × 2 cm3 and 30 × 30 × 2 cm3, using a high-voltage high-frequency power supply. The influence of multiple excitation parameters on the gas discharge has been studied, the emission spectrum data have been measured to obtain the plasma parameter distribution in the cavity, and the factors affecting the plasma parameter distribution in the closed discharge cavity have been analyzed. The amplitude of the discharge current of the multilayer dielectric barrier discharge method has been found negligible, and the range of the plasma parameters is limited. However, by using a nanosecond pulsed glow discharge, the uniformity of plasma distribution has been significantly improved. Further, it is conducive for the adjustment of the plasma parameters corresponding to the cavity.

Pressure broadening of 772.376 and 772.421 nm argon lines and kinetics of argon metastable atoms

Tunable diode laser absorption spectroscopy is used for recording the spectrally mixed profiles of argon 772.376 nm (2p7–1s5) and 772.421 nm (2p2–1s3) lines at different argon background pressures between 0.3 and 1 atmosphere. The absorbing atoms in the Ar*(1s5) and Ar*(1s3) metastable states are produced in a plane-to-plane dielectric barrier glow discharge operating at 20 kHz. The pressure broadening coefficient w and wavelength shift, s of the lines, deduced from the analysis of their variation versus pressure of recorded profiles, are w1=28.3 ± 2.0 pm (14.2 ± 1.0 GHz) and s1=11.5 ± 0.8 pm (-5.8 ± 0.4 GHz) for 772.376 nm line and w2=36.3 ± 0.5 pm (18.2 ± 0.3 GHz) and s2=12.8 ± 0.7 pm (-6.4 ± 0.4 GHz) for 772.4207 nm line, at 1 bar and 300 K. The progressive enhancement with argon pressure of the peak densities ratio [Ar*(1s3)]/[Ar*(1s5)], reaching 0.3 at 1 bar, reveals the importance of Ar-induced collisions for the population transfer from resonant 1s2 to the metasTable 1s3 state. Also, the time variation of Ar*(1 s) densities indicates the presence of a weak excitation channel outside the discharge current pulse initiated by the breakdown. This channel results from the heating of electrons by the electric field seen by the gas in the DBD gap.

Modeling the Parameters of an Atmospheric Pressure Dielectric Barrier Discharge Controlled by the Shape of the Applied Voltage

In this work, a 1-D extended fluid model is built to investigate the effects of the electric waveform supplying a dielectric barrier microdischarge plasma. Three symmetric waveforms (sine, square, and triangle) are used in this study in addition to one asymmetric waveform (positive ramp). The results of numerical experiments show that the discharge activity is strongly affected by the applied voltage waveform, where the dielectric-barrier glow discharge (DBD) in case of the sine and triangle waveforms is more filamentary (with series of narrow current density peaks) when compared with the square waveforms. Although the discharge period of the sine and triangle waveforms is high, the rms value of its current is lower than that in the case of the square waveforms.

NMR evaluation of apple cubes and apple juice composition subjected to two cold plasma technologies

This study evaluated the effects of two cold plasma technologies, glow discharge plasma and dielectric barrier discharge plasma (DBD), on the chemical composition of apple cubes and apple juice analyzed by 1H NMR coupled with chemometrics. The effects of different technologies (glow discharge and DBD) and operating conditions (processing time, gas flowrate, and excitation frequency) were evaluated on the concentration of sugars and organic acids of apple juice and apple cubes. Changes in sugars and organic acids were observed after the application of both plasma technologies. Glow discharge plasma application induced the decrease in sucrose content and the increase in glucose, fructose, and malic acid. Dielectric barrier discharge plasma induced sugar reduction and increased malic acid content. Cold plasma technology depolymerized sucrose into glucose and fructose by cleavage at the ether bond. DBD plasma further induced glucose and fructose consumption, most probably through the phenylpropanoid mechanism. Cold plasma technology could be used to modulate apple products' sensory characteristics, altering both sweetness and sugar-acid ratios.

Fourier‐transform infrared spectroscopy of ethyl lactate decomposition and thin‐film coating in a filamentary and a glow dielectric barrier discharge

AbstractGlow and filamentary regimes of atmospheric pressure plasma‐enhanced chemical vapor deposition in a planar dielectric barrier discharge configuration were compared for thin‐film deposition from ethyl lactate (EL). EL decomposition in the plasma phase and thin‐film composition were both characterized by Fourier‐transform infrared spectroscopy. EL chemical bonds' concentration along the gas flow decreases progressively in the glow dielectric barrier discharge (GDBD), whereas it drastically oscillates in the filamentary dielectric barrier discharge (FDBD), with values higher than that of the initial mixture. EL decomposition route depends on the discharge regime, as the decrease of the concentration of the different investigated bonds is different for an identical amount of energy provided to EL molecules. CO2 is systematically formed reaching concentrations of 25 and 40 ppm, respectively, in FDBD and GDBD.

Discharge dynamics of a nanosecond pulsed helium/argon nanosecond atmospheric pressure glow discharge

A nanosecond pulsed atmospheric pressure dielectric barrier glow discharge in helium with 1% of argon was studied. The effects of the electric field, frequency, and gas mixture ratio on the temporal behavior of the plasma discharge were captured with an ICCD camera. Special interest was given to the timing and scale of the secondary or return stroke. It was found that the external electric field can control the occurrence of the return stroke in a dielectric barrier discharge. If the electric field is high enough, the return stroke occurs earlier than previously observed in other works. Increasing frequency leads to faster discharge initiation times for both the primary and secondary discharges. Increasing the argon ratio of the mixture leads to an increased intensity of the primary discharge, a decrease in the intensity of the secondary discharge, and a delay in the timing of the primary discharge.

Characterization and Applications of Non-Magnetic Rotating Gliding Arc Reactors - A Brief Review

Gliding arc discharge (GAD) reactors are known for high energy efficiency and good chemical selectivity compared to non-thermal plasmas such as glow discharge, corona and dielectric barrier discharge. Reported literature identified that planar diverging GAD have non-uniform gas treatment (e.g. only 20% of gas processed by plasma depending on electrode configuration). Further requirement of minimum limit gas velocity to drag the arc results in lower gas residence time.
 This paper attempts to investigate the GAD performance and preliminary studies to overcome some of the identified drawbacks, by using only fluid mechanics without magnetic field (rotating gliding arc (RGA)) inside the plasma reactor developed in various research laboratories. This article discusses the applications of GAD and also focuses on bringing out the performance and comparing with the results from the existing non-magnetic rotating gliding arc reactors. The paper also summarizes results from literature in such reactor designs.

Various patterns in dielectric barrier glow discharges simulated by a dynamic model

In this paper, various patterns of dielectric barrier glow discharge simulated by a phenomenological dynamic model are reported. The model is constructed based on the basic dynamic process of dielectric barrier glow discharge and involves the voltage-transfer characteristic as well as the lateral inhibition effect. In simulations, different driving voltage profiles are applied to achieve one or two pulsed discharges in each half-period and the corresponding pattern evolution is investigated. The final stable patterns driven by a rectangular wave voltage organize simply as stationary striations or hexagonal lattices. The patterns driven by a multi-step wave appear to be much more complicated, with complementary striations, concentric rings and square superlattices observed. The evolutions of these patterns from the initial uniform state are described and it is found that the spreading of the inhibition effect plays a key role in these evolutions. The numerical simulations in the present work are in excellent accordance with previous experiments and fluid modeling. This dynamic model proves to be a convenient and promising approach to reproducing different pattern structures and pattern evolutions in dielectric barrier glow discharge systems.

Multimethods and Underlying Mechanism for Realizing Uniform Discharge From Patterned Structures by Varying Controlling Parameters

The uniform gas discharge has long been pursued for realizing or improving some practical applications but is difficult to achieve due to the fact that nonuniform discharges are much easier to be generated in most cases. Usually, achieving uniform gas discharge requires sophisticated devices, and the operation is complicated and time-consuming. In this paper, we introduce simple and flexible multimethods for realizing uniform discharge from patterned structures under dielectric-barrier discharge (DBD) systems by varying experimental controlling parameters, and these methods can be employed in combination. The effects of driving frequency, voltage, duty ratio, and magnetic/electric field on glow DBD structure are investigated. It is found that a uniform glow DBD is obtained when frequency, voltage, and duty ratio are either very high or very low and also by the introduction of strong magnetic/electric field. The underlying physics of these methods is consistent as the elimination of a focusing effect of space electrons. It is concluded that the key of achieving uniform discharge is to uniformize the distribution of space charges.

Hard Carbon Films Synthesized By Atmospheric Pressure Filamentary Dielectric Barrier Discharge

To synthesize hydrogenated amorphous carbon (a‐C:H) films, filamentary dielectric discharge (FDBD) is used to improve their mechanical properties compared to the films synthesized by glow dielectric barrier discharge (GDBD), which is generally used for atmospheric pressure‐plasma‐enhanced chemical vapor deposition. The discharge form transitioned from GDBD to FDBD when the gap between the electrodes is increased from 1 to 4 mm. The hardness of the films increased from 3.7 to 11.9 GPa by using FDBD. The results indicate that hard a‐C:H films can be synthesized at room temperature by atmospheric pressure using FDBD.

Numerical simulation of the multi-pulse phenomena in atmospheric-pressure dielectric barrier glow discharges in He/N2mixture

To further understand the formation mechanism of multi-pulse phenomena in atmospheric He/N2dielectric barrier glow discharge, the influence of nitrogen content on the multi current pulse phenomena is studied by a one-dimensional plasma fluid model. As nitrogen content increases, the first discharge current in the multi-pulse glow discharge becomes larger, and the gas gap voltage drop and the charges transported during the first discharge pulse are also increased, leading to the decrease of subsequent discharge current. When the increasing applied voltage cannot overcome the gas gap voltage drop in the first discharge pulse, the multi-pulse discharge mode will transit into a single pulse discharge mode. The numerical simulation results also show that the changes of discharge characteristics are mainly attributed to the Penning ionization between molecules of nitrogen and metastable atoms of helium.

Synthesis of diamond-like hydrocarbon films by atmospheric pressure filamentary dielectric barrier discharge

Diamond-like hydrocarbon (DLHC, a-C:H) films were synthesized under atmospheric pressure filamentary by dielectric discharge (FDBD) to improve their mechanical properties compared to the films synthesized by glow dielectric barrier discharge (GDBD). GDBD is generally used for atmospheric pressure-plasma-enhanced chemical vapour deposition. The discharge form transitioned from GDBD to FDBD by increasing the gap between electrodes from 1 to 4 mm. The hardness of the films increased from 3.7 to 11.9 GPa by using FDBD. The results indicate that hard DLHC films can be synthesized at room temperature and on a large area under atmospheric pressure using FDBD.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air.

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (∼0.28 W/cm2) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (∼50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Conference Proceedingon Nanomaterials and Nanochemistry Hard Carbon and Silica based Films Synthesized under Atmospheric Pressure

Atmospheric pressure-plasma enhanced chemical vapor deposition (AP-PECVD) method using a dielectric barrier discharge (DBD)is a cost-effective process because of no need of vacuum process. In this study, we synthesized silicabased films (SiO:CH) and hydrogenated amorphous carbon films (A-C:H) by AP-PECVD method. We synthesized SiO:CH films from tetramethoxysilane (TMOS) and O2 diluted with N2 and investigated the effect of the substrate temperature and the TMOS flow rate on hardness of the films. The hardness increased from 4.0 to 6.9 GPa as the substrate temperature increased from 80 to 300°C. To synthesize a-C:H films, filamentary DBD (FDBD) was used to improve the hardness compared to the films synthesized by glow DBD (GDBD), which is generally used for APCVD.The hardness of the films increased from 3.7 to 11.9 GPa by using FDBD.

Observation of the stratified glow mode in helium/argon gas-confined barrier discharge at atmospheric pressure

A diffuse He gas-confined barrier discharge insulated by an Ar gas layer instead of a solid dielectric is reported for the first time. It is unexpected to observe that the diffuse Ar plasma attached to the electrode is generated along with the He plasma. The Ar/He/Ar plasma layers with diffuse appearance are visually separated by dark space and thus form the stratified glow. The presence of the stratified mode is largely dependent on the applied voltage, the Ar flow rate and the diameter of the helium gas flow. As the diameter of the helium gas flow decreases from 2.5 mm to 0.9 mm, the discharge mode transits from a stratified glow to filamentary with the amplitude of the discharge current increasing from 0.28 mA to 3.8 A. High-speed photographs of the stratified glow show that the plasma is ignited at the He/Ar gaseous interface, and then expands uniformly towards both the He and Ar gas layers. After the plasma front in He gas layer is quenched at the opposite gaseous interface, the plasma volume starts expanding towards the periphery of the electrode, similar to the dielectric barrier glow discharge.

Effect of glow discharge and dielectric barrier discharge plasma as surface treatment on repaired acrylic denture base resin

Objective: The purpose of this in-vitro study was to investigate the effect of glow discharge and dielectric barrier discharge (DBD) plasma on repaired acrylic denture base resin as regard to shear bond strength and transverse strength. Materials and methods: Eighty specimens were prepared in this study, 30 for shear bond strength and 50 for transverse strength. Shear bond strength specimens are double fused discs. One disc prepared from heat-cured acrylic resin 15 mm × 3 mm. Glow discharge and DBD plasma with consumed energy of 360 and 720 J were used to treat the specimens. The surface of specimen was wetted with methylmethacrylate. The other disc, prepared from self-cured acrylic resin 6 mm × 2 mm, was attached to that surface as a repair material. Shear bond strength was determined using a universal testing machine. Transverse strength specimens were prepared in dimensions of 65 mm × 10 mm × 2.5 mm. Specimens were fractured, treated with plasma, wetted with methylmethacrylate then repaired. Transverse strength was measured by three-point bending test. Data were analyzed using one-way analysis of variance and Tukey's multiple comparison test interval at 0.05 level of significance. Results: There was a significant difference between the mean values of shear bond strength (MPa) and between the mean values of transverse strength (MPa) of repaired acrylic denture base resin (P Conclusion: Using glow discharge plasma at 720 J as a surface treatment could increase the shear bond strength. Also, using DBD plasma treatment at 360 J could increase the transverse strength.

Simulations of the cathode falling characteristics and its influence factors in atmospheric pressure dielectric barrier glow discharge pulse

A fluid model is built in this paper to describe and study the atmospheric pressure dielectric barrier glow discharge pulse in helium. The collision excitation and ionization reactions between electron and helium atom, heavy particles reactions, and Penning reaction between N2 and metastable He are taken into account in the fluid model. It is found that there are cathode falling, negative glow, Faraday dark, positive column and anode glow areas in atmospheric pressure glow discharge pulse, and the ranges of different areas are changing during the current falling edge. The ranges of cathode falling area are defined according to electron production balance position (definition 1, set as dc1) and the electrical field distribution around cathode (definition 2, set as dc2), respectively. Both dc1 and dc2 decreaseas the current grows to its peak in one discharge pulse, which reflects the transition from Townsend discharge to glow discharge. Compared with negative glow peak position, the boundary of cathode falling area by definition 1 is closer to cathode. However, the dc1 cannot reflect the cathode potential falling value and lose its definition after current peak moment. The dc2 can reflect the cathode potential falling value but it causes the overlapping between cathode falling and negative glow areas. At the current peak moment, the glow peak is located at the boundary of cathode falling area according to definition 2 while the glow peak is always located in the cathode falling area during the current falling edge. The cathode falling area characteristics can be influenced by different factors, e. g. applied voltage, secondary electron emission coefficient γ and N2 content. By changing applied voltage, it is found that the electrical potential dropping in cathode falling area increases as the average current density decreases, which indicates that the atmospheric pressure dielectric barrier glow discharge pulse is a subnormal glow discharge, and it is close to the normal glow discharge region. When γ dc1 and dc2 increase sharply with γ decreasing. When γ >0.02, dc1 and dc2 increase slowly with γ increasing. When N2 content is greater than 4 ppm, dc1 and dc2 first decrease and then increase slowly. The electrical potential falling of cathode is changeless with N2 content changing. However, the voltage across the gas gap decreases with N2 content changing because the Penning effect lowers the breakdown voltage of the gas gap. The spatial average current density has a highest value when N2 content is about 35 ppm, which also means that the spatial average charged particle density has the highest value in the same situation. Moreover, when the secondary electron emission coefficient is a constant, both dc1 and dc2 have negative linear relationship with the average current density.