Gas Discharge Research Articles

Ion Chemistry in Dielectric Barrier Discharge Ionization: Recent Advances in Direct Gas Phase Analyses.

Dielectric barrier discharge ionization (DBDI) sources, employing low-temperature plasma, have emerged as sensitive and efficient ionization tools with various atmospheric pressure ionization processes. In this review, we summarize a historical overview of the development of DBDI, highlighting key principles of gas-phase ion chemistry and the mechanisms underlying the ionization processes within the DBDI source. These processes start with the formation of reagent ions or metastable atoms from the discharge gas, which depends on the nature of the gas (helium, nitrogen, air) and on the presence of water vapor or other compounds or dopants. The processes of ionizing the analyte molecules are summarized, including Penning ionization, electron transfer, proton transfer and ligand switching from secondary hydrated hydronium ions. Presently, the DBDI-MS methods face a challenge in the accurate quantification of gaseous analytes, limiting its broader application in biological, environmental, and medical realms where relative quantification using standards is inherently complex for gaseous matrices. Finally, we propose future avenues of research to enhance the analytical capabilities of DBDI-MS.

Investigation of highly efficient CO2 hydrogenation at ambient conditions using dielectric barrier discharge plasma

The increasing utilization of CO2 for synthesizing high-value fuels or essential chemicals is a potentially effective approach to mitigating global warming and climate change. Compared to thermal catalytic CO2 conversion under hash operating conditions (400∼500°C, 10 MPa), non-thermal plasma can overcome kinetic barriers and trigger reactions beyond thermal equilibrium at ambient temperature and pressure. In this study, the effects of operating conditions (discharge frequency, input power, and gas flow rate) and geometrical parameters (discharge length, discharge gap, and dielectric materials) have been extensively analyzed using typical cylindrical dielectric barrier discharge (DBD) plasma. The discharge characteristics changed by operating conditions (including waveforms of applied voltage and current) are compared, indicating higher applied voltage and lower gas flow rate can strengthen the filamentary discharges. The results demonstrate CO2 conversion rate increases with the increase of applied voltage and the decrease of CO2/H2 ratio, achieving its maximum value of 43.0% at 20 mL/min. The highest energy efficiency of 3771.9 μg/kJ for CO generation is obtained at the applied voltage of 5.5 kV and gas flow rate of 40 mL/min, respectively. Besides, the constructure of plasma reactor also impacts the performance of CO2 conversion. On the one hand, the discharge gap has a significant role in the variation of CO2 conversion and product selectivity, which is attributed to the electric field density and corresponding electron-induced reaction. On the other hand, the circulating water-cooling jacket was used to find out the influence of reaction temperature, which switched the product from CO to CH4. This work will pave the way for a sustainable alternative towards future CO2 conversion and utilization.

High-performance insulating materials with high breakdown strength and low permittivity for eco-friendly electrical equipment

High-performance insulating materials are essential for developing lightweight, compact, and green offshore wind power equipment. It has been shown that nanoporous structures can limit the development of electron avalanche, leading to a significant increase in the breakdown electric strength of dielectrics. Hence, we fabricated a polysiloxane nanoporous biopolymer insulating material (PNBIM) with the nanoporous structure that presents exceptionally high electrically insulating properties. Under a CO2 atmosphere, the breakdown electric strength of the PNBIM was remarkably improved, exhibiting 761.01 % enhancement relative to that of the pure gas gap. Moreover, the PNBIM demonstrates excellent dielectric performance, with a low dielectric constant (1.63) and dielectric loss (0.014), as well as high hydrophobicity and excellent thermal stability. The investigations revealed that the nanopores inside the material can effectively suppress gas discharge and improve the breakdown electric strength. This study widens our understanding of conventional insulating materials and provides a promising approach for exploring high-performance insulating materials provide valuable insights.

Study of TaN and Ta2O5 coatings obtained by sputtering with non-self-sustained gas discharge for biomedical implant modification

Tantalum nitride (TaN) and tantalum oxide (Ta2O5) coatings were manufactured by using sputtering with sustained gas discharge in Bulat-type facility. Characteristics of the obtained coatings, including surface morphology, nanohardness, surface wettability, Young's modulus, and biocompatibility, were investigated. Different surface roughness of TaN and Ta2O5 made the main contribution to the transition to hydrophobic surface properties, which led to different conditions for cell adhesion. According to the test results, the average value of the elastic modulus for the sample coated with TaN was 426.1 GPa and Ta2O5 - 172.4 GPa, respectively. The maximum nanohardness was obtained for the TaN nitride coating and reached 37.8 GPa. The biocompatibility of the samples was assessed in vitro by the susceptibility of the surface of the material to cells, since cell attachment and proliferation are closely related to the surface characteristics of the implant. The Ta2O5 coating has shown appropriate biocompatibility profile, as it provides an ideal environment for Mesenchimal Stem Cells (MSC) adhesion from day 1, followed by cell proliferation until the end of the experiment. The TaN coating did not support cell attachment and proliferation during the experiment.

Assessment of the gas discharge characteristics during gas recovery by hydrate decomposition

Hydrate-based gas separation is a novel approach for the capture and recovery of hydrofluorocarbons. The gas discharge characteristics during hydrate decomposition need to be clarified for the efficient recovery of hydrofluorocarbons. In this study, we investigated the mass transfer characteristics during the gas recovery from hydrate particles by decomposing the HFC134a hydrates. First, the volumetric mass transfer coefficient was estimated from the gas recovery rate during the HFC134a hydrate slurry. The hydrate particles enhanced the gas recovery performance of the overall apparatus. Next, the mass transfer coefficient between hydrate and liquid was calculated. Ascending bubbles and the resulting change in the dispersion state of the particles significantly affected the mass transfer. Finally, we developed a mass transfer correlation equation between the solid and liquid phases by dimensionless numbers based on Kolmogorov’s theory. The experimental equation predicted the Sherwood number with ±40 % accuracy and an average absolute relative error of 19.0 %. The dispersion state of the hydrate particles was a significant factor in the estimation.

Movable VOC Removal System

In this study, we develop a mobile VOCs gas removal system that can remove volatile organic compound (VOCs) emissions from petrochemical facilities, metal painting factories, and surroundings of life, and can efficiently cope with situations occurring in the field. Regular repairs to petrochemical plants and semiconductor plants are carried out for a month every four to five years, and work such as replacing old pipes and repairing aging facilities, cleaning, removing residual gas, checking pipe connections and valves, and improving processes are carried out while the plant is shut down. During regular maintenance, a large-scale accident occurs in which gas remaining in the facility leaks or explodes due to rising pressure, and even after internal gas discharge and purge work is performed, it is scattered by the characteristics of raw materials remaining inside the pipe and reactor and discharged into the atmosphere. Therefore, there is always a possibility of causing safety accidents, and such accidents have a great socioeconomic impact as they are directly connected to the safety of workers as well as the safety of local residents. This system is designed to be adaptable according to the size of a number of outlets, and it is proposed to minimize the impact of VOCs harmful gases on the surroundings by developing it as a mobile type. The efficiency of collecting scattered VOCs gas is more than 90%, and the integrated operating system is demonstrated for 50 CMM class movable VOCs adsorption device, 5 CMM class treatment gas recirculation type non-flame waste heat recovery adsorbent regeneration treatment device, and two or more business sites.

Data-driven discovery of a model equation describing self-oscillations of direct current discharge

Data-driven techniques developed in recent years for the discovery of equations describing complex physical phenomena open unique opportunities for plasma physics. These methods allow getting insights into the processes difficult for analytical description. Since gas discharges can be represented as complex electrical circuits consisting of impedances and capacitances, it looks natural to use the data-driven techniques to study their complex dynamics. In the present paper, the sparse identification of nonlinear dynamics (SINDy) method is applied to analyze the self-oscillations of direct current discharge in argon. It is obtained that the third order polynomials describe best the oscillations of the discharge voltage and current. They allow an accurate capturing of the oscillations amplitudes as well as the harmonics of these oscillations. To understand the physical meaning of each term, an analytical model is presented which describes the discharge self-oscillations.

Methodology for measuring the energy characteristics of two-electrode gas discharge plasma switches in the picosecond range using the reflectometry method

This research proposes a new technique for measuring the energy characteristics (losses of energy in the spark gap, related to light radiation, ionization, excitation, and heating of the working gas during the development of plasma; discharge power) of two-electrode gas dischargers in the subnanosecond range. The work examines the voltage waveforms across the discharge gas gap and the discharge current waveform obtained by the reflectometry method in the subnanosecond range. To do this, the traditional technique for measuring such characteristics was modified. This allows us to restore the back edge of the voltage pulse across the discharge gap at the breakdown delay and the breakdown stages, which is usually lost in the subnanosecond range when measuring such waveforms. For modification, calculated data on the ionization frequency were used. This allows us to replace the plasma of the discharge gap with a constant resistor in those sections of the voltage waveform where the characteristic ionization time is more than an order of magnitude longer than the duration of the voltage pulse applied to the gap. The waveforms of the voltage across the discharge gap and the discharge current obtained in this way allowed us to calculate the power dynamics and total energy introduced into the gas discharge plasma. These parameters are important both for calculating the efficiency of gas switches and for other applications of gas discharge plasma, in particular laser pumping.

Study on the Design and Application of the Three-electrode Ionization Particle Sensor

Accurate detection is the foundation of haze governance. The existing particle concentration detection methods and instruments have many shortcomings, such as complex structure, high cost, easy blockage, short life, and significant impact of environmental changes. Therefore, this paper proposes a silicon micropillar three-electrode ionization particle sensor based on the gas discharge principle and studies the sensor's sensitivity to PM2.5 particles. Three-electrode comprises a cathode with micro silicon pillars grown on the surface, an extracting electrode, and a collecting electrode. It shows that the cathode current of the sensor increases linearly with extraction voltage and nonlinearly with temperature. As the cathode material of the sensor, the silicon micropillar is compared with the carbon nanotube to solve the burn problem of the nanotube rising from positive ions bombardment during gas discharge. The collecting current of the sensor shows a decreasing trend with the increase in particle concentration. The collecting current and sensitivity of the sensor are much higher in radio frequency excitation than in direct current excitation. The sensor developed in this paper displays the advantages of simple technology, high integration, low cost, and high sensitivity, and it exhibits great application potential.

Plasma-mediated mercury vapor generation after microwave-induced combustion of fish tissue with detection by atomic absorption spectrometry

Mercury determination in fish tissues by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) was performed using microwave-induced combustion (MIC) for sample preparation, and plasma-mediated vapor generation (PMVG) in a tubular dielectric barrier discharge (DBD) as a sample introduction system. The main goal was to develop a method for Hg determination using very low amount of reagents being at the same time virtually free of interferences. The operational parameters of the PMVG step in the DBD reactor were optimized as follows: 70 mL min−1 Ar as the discharge gas, 20 mm electrode distance, primary voltage at 60 V and 50 μL as digested sample volume (in 0.1 mol L−1 HNO3 matrix). The effect of HNO3 concentration on the PMVG efficiency was studied. No differences in signal intensity were observed for HNO3 concentration up to 0.1 mol L−1, while a signal decrease by 25 % and 40 % was observed when the acid concentration increased to 1 and 5 mol L−1, respectively. Accuracy of the proposed method was evaluated using certified reference material (CRM) of dogfish liver (DOLT-4) and by Hg spikes on the sample prior to MIC. By using 500 mg of sample (or 250 mg of CRM) and 6 mL of 0.5 mol L−1 HNO3 as absorbing solution in MIC, recoveries of 104 % and 97 % were observed for spikes and CRM values, respectively. A limit of detection of 0.16 μg g−1 Hg (160 pg Hg absolute) was obtained. A comparison of the results for Hg determination in the CRM by PMVG-AAS and chemical cold vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS) was performed with no significant differences in the results. Finally, an efficient, low-cost and low-volume reagent consumption sample introduction system for Hg determination by AAS was successfully combined with the advantages of MIC and subsequent PMVG by DBD.

The effect of a constant electric field in an undisturbed plasma on the stability of the electron beam–gas discharge collisional plasma system

This work is devoted to the study of a fast non-relativistic electron beam–gas discharge plasma system within the framework of the kinetic theory of stability. The influence of a constant electric field, collinear beam velocity, on the stability of the system in an undisturbed plasma is studied. It is shown that even a relatively small electric field, which does not significantly affect the energy of the electron beam, can lead to significant changes in the parameters of harmonic disturbances propagating in the electron beam–plasma system in the region of its instability. It was found that the reason for such changes is the drift of plasma electrons, which, as a consequence, leads to a change in the frequency of disturbances in the coordinate system associated with the plasma due to the Doppler effect. The results obtained are demonstrated by calculations based on the kinetic theory of perturbation parameters in a low-voltage beam discharge in rare gases, which is used in the development of plasma electronics devices. The effect of electron-atomic collisions on the stability of the electron beam–plasma system is investigated and compared with the results of other authors' works.

Full-scale modeling and experimental study of a gas neutron tube with a Penning ion source

This paper studies full-scale gas neutron tube modeling, including the following processes: gas discharge combustion in a Penning ion source, particle motion in an ion optical system, and modeling the in-target processes, such as sputtering, diffusion, thermal desorption of hydrogen isotopes, and nuclear reactions. Plasma modeling in quadrupole electric and axial magnetic fields was based on the electrostatic particle-in-cell method with molecular kinetic processes. The TechX Vsim software package was used. The neutron tube element sputtering by ions was simulated using SRIM/TRIM software based on Monte–Carlo methods. The OpenFOAM, as an open integrated platform for numerical simulation in continuum mechanics, was used to calculate the hydrogen thermal desorption activated by ion irradiation. The time-dependent neutron yield modeling was performed using the Geant4 software based on Monte–Carlo methods with CHIPS-TPT VNIIA-developed library. In addition, an experimental study of a gas neutron tube with a Penning ion source was conducted here as well. Details are given on the experiment and measurement technique used in this study. The operating characteristics for the gas neutron tube, including amplitude-time characteristics of current flashes (discharge and extraction currents), were determined. The neutron flux dependencies on the discharge current at various accelerating voltages were also obtained. Finally, a comparison between the experimental and calculated results is presented.

Development and application of carbon dioxide direct mineralization technology and emission reduction device

Abstract This study analyzes the principles and methods of carbon dioxide mineralization fixation to address the challenges posed by global climate and ecological changes, achieve carbon neutrality goals, and solve carbon utilization issues in the development of the fluorosilicon new material industry. The research focuses on the direct mineralization reaction system of carbon dioxide flue gas and the development of a carbon dioxide emission reduction device utilizing wet mineralized gas treatment technology. To implement alkaline waste management for industrial solid waste. The research shows that the wet carbon dioxide mineralization and emission reduction device can make the alkaline solution better mineralize carbon dioxide, avoid the gas discharge too fast and affect the reaction rate. At the same time, the solution is mixed and the exhaust linkage is carried out to further improve the reaction rate, and provide a reference for the development of large-scale carbon dioxide utilization technology suitable for high energy consumption industries.

Efficient evolution mechanism of electrolytic gas products from laser-assisted electrolyte jet machining

Efficient evolution of electrolytic gas products is one of the mechanisms for increased material removal rate in laser-assisted electrolyte jet machining. However, the evolution mechanism of electrolytic gas products with multiple energy fields in laser-assisted electrolyte jet machining is not clear. In order to quantitatively characterize the laser-assisted facilitation of the evolution of electrolytic gas products, a gas quantification and detection device was designed and built in this paper. Compared to traditional electrolyte jet machining, laser-assisted electrolyte jet machining of 2024-T3 aluminum alloy increased the gas production by 52 % in 180 s. For the anode, the surface modification induced by laser texturing reduces the oxygen evolution potential and surface free energy and promotes gas nucleation and detachment. In addition, laser-induced conductive plasma can enhance transient currents for electrolyte jet machining and cause machining vibrations. The cathodic gas discharge phenomenon was characterized in conjunction with interelectrode gap visualization experiments and cathodic nozzle damage. Experimental results show that cathodic gas discharge depends on strong electric field and high laser pulse fluence. In summary, laser temperature rise, anode surface modification, laser-induced plasma, plasma recoil and cathode gas discharge can all contribute to the evolution of electrolytic gas products.

Karl George Emeléus and Physics in Belfast 1927–66

AbstractKarl George Emeléus (1901–1989) was educated at Cambridge and after a short period at King’s College, London, he spent the remainder of his career as lecturer (1929–33) and then professor (1933–66) of physics at Queen’s University, Belfast. At Queen’s, he set the direction of experimental research in gas discharge and plasmas for a generation and oversaw the growth of the department. He also acted as a spokesman for physics in Northern Ireland and was involved in public responses to concerns about the use of nuclear weapons and nuclear energy in the late 1940s and 50s. This paper summarises Emeléus’s life and work and sets it in the context of physics at Queen’s University in the mid-twentieth century.

Removal of dichloromethane from gas streams by droplet triggered gas discharge

The removal of dichloromethane (DCM) from gas streams by a novel gas discharge reactor triggered by solution droplets was experimentally investigated. The influences of operation parameters such as input energy, gas flow rate, oxygen concentration, droplet dropping frequency, and the solution composition of droplets on the effectiveness of reactor operation and DCM removal efficiency were examined. Experimental results showed that DCM in the gas stream can be effectively degraded, and the removal of DCM decreased with the increase of the initial DCM concentration in the gas stream. With the increase of droplet dropping frequency, the removal of DCM experiences a process from increase to decrease, and the optimal droplet dropping frequency is around 0.5–1 drop·s−1. It was also found that the oxygen concentration in the range of 5–10 % in the gas stream is better for DCM decomposition, and the use of alkaline solution as droplets can effectively improve the removal of DCM. The final gas phase products of DCM degradation were mainly CO2 and O3 with the presence of O2 in the gas stream, and the liquid phase products were chloride (Cl-) and hypochlorite (ClO-) ions.

Excitation and ionization of a diagnosis gas in front of the flexible μ tube plasma and in a diagnosis tube

The noble gases Helium, Argon, Krypton and even Xeon have been applied as discharge gases for the flexible μ tube plasma (FμTP) with comparable ionization efficiencies. It was assumed that a temporally and spatially limited potential plays a major role in the generation of reactant ions responsible for protonation in the surrounding air. However, the excited and ionized species of ambient air cannot be detected directly by emission spectroscopy because there is no known emission wavelength within the detectable range. In this work, a diagnosis gas was introduced as a substitute for the surrounding air to understand the excitation and ionization outside the discharge capillary. It was found that with Ne, Ar, Kr, Xe as plasma gases the diagnosis gas He can be excited during the positive half cycle. The emission of He 706 nm and N2+ 391 nm propagate with and against diagnosis gas flow directions in case of He and Ne driven plasmas. In case of Ar, Kr, and Xe driven plasmas, the emission of both species mainly develops against the diagnosis gas and the shapes of He 706 nm are wide. Further on, the diagnosis gas He is also excited even though there is a glass wall between the plasma gas flow and diagnosis gas flow. These findings demonstrate that the transient potential is responsible for the excitation of the diagnosis gas, not penning ionization or charge transfer between discharge plasma and diagnosis gas.

On the Energy Cost for Nitrogen Fixation in DC Glow Discharges in Atmospheric‐Pressure Air

ABSTRACTModeling of the production of nitrogen oxide molecules in DC discharges in laminar longitudinal flows of atmospheric‐pressure air is performed. Two‐dimensional nonequilibrium discharge model includes the system of gas dynamic equations and balance equations for various plasma components. Simulations are performed for the discharge currents 50–600 mA and gas flow velocities 1–10 m/s. In considered conditions, the gas temperature in the discharge core varies in the range of 3000–6000 K. Spatial profiles of the densities and fluxes of produced species are obtained, both inside the discharge and in the afterglow region. The energy cost for the production of nitrogen oxides is calculated, depending on the discharge current, gap length, and gas flow velocity. The results of the simulation are compared with available experimental data.

Effect of atmospheric pressure cold plasma (ACP) treatment on technological characteristics of chia (Salvia hispanica L.) seeds

The highly nutritious nature of chia seeds drives its increased utilization by the consumer and industries. This study is done to investigate the impact of atmospheric pressure cold plasma (ACP) based on air gas and dielectric barrier discharge (DBD) design. ACP treatment as an emerging non-thermal processing at different time (3 and 8 min) and voltage (6.5 and 8.5 kV) on technological characteristics of chia seeds including physicochemical, rheological, thermal, textural and morphological characteristics which are generally induced by carbohydrate and protein fraction. Results indicated an increase in water absorption index (10.36 ± 0.10 g/g), swelling power (10.43 ± 0.94 g/g) and decrease in gelatinization enthalpy (313.7 ± 0.9 J/g) at samples treated for 8 min at 8.5 kV. The lowest hardness (1390.5 ± 50.4 g) and highest peak temperature (94.79 ± 0.5 °C) is also observed at samples treated for 3 min at 8.5 kV. Changes in technological properties observed through ACP treatment are generally determined by the interaction of plasma activated species with molecular components, their depolymerization and cross-link formation as verified by FTIR analysis. Regarding, ACP treatment influences the structure of protein and carbohydrate macromolecules on the basis of its intensity.

Effect of feeding amount on tail gas and waste salt obtained from molten salt oxidation process of cation exchange resins

ABSTRACT The effective treatment of spent radioactive ion exchange resins generated during the operation of nuclear facilities is of great significance to reduce its potential hazards to the environment. This work innovatively provides a simple and low-cost molten salt oxidation (MSO) system includes air intake, feeding, waste salt discharge and exhaust gas treatment and analysis system for disposal of spent cation exchange resins (CERs). By studying three feeding amounts that injection of 25 g, 125 g and 1250 g CERs in 10 times under air conditions, the oxidation efficiency of CERs in MSO system was further evaluated. The scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) results indicated the sulfur can be trapped in the melt. Sulfur in functional group can be converted to Na2S and KLi(SO4) via Li2CO3-Na2CO3-K2CO3, which is proved by XRD patterns. The experimental results presented that degradation rates of CERs are 99.31%, 99.80%, and 99.91% in different feeding amounts, respectively. Furthermore, the volume reduction of residue gathered by feeding 1250 g CERs in 10 times was the highest, which can reach 9.19. Therefore, the bench-scale MSO system is a potential and promising treatment for spent CERs volume reduction.