Atmospheric Pressure Glow Discharge In Air Research Articles

The impact of large volume atmospheric pressure air glow discharge plasma on enhancing denim fabric (textile) sewing process

A direct-current large-volume atmospheric pressure air glow discharge plasma (APAGDP) was developed to enhance the sewing process of denim fabric. The generated plasma was characterized optically, electrically, and spectroscopically. The generated plasma presents a positive electric resistance behaviour. The plasma emission spectra are dominated by the nitrogen second positive system. Its intensity increases with the applied voltage. The generated plasma was used as a pre-treatment to enhance the sewing of the denim fabric at different exposure times, from 5 to 600 s. The scanning electron microscopy images showed no damage to the surface morphology of the denim fabric after plasma treatment. The sound pressure level (SPL) was used to verify the plasma effect on the denim fabric as compared to the untreated fabric. The SPL decreases with plasma exposure time. This result indicates that the plasma improves the sewing performance of the denim fabric.

Modelling of an Atmospheric–Pressure Air Glow Discharge Operating in High–Gas Temperature Regimes: The Role of the Associative Ionization Reactions Involving Excited Atoms

A model of a stationary glow-type discharge in atmospheric-pressure air operated in high-gas-temperature regimes (1000 K < Tg < 6000 K), with a focus on the role of associative ionization reactions involving N(2D,2P)-excited atoms, is developed. Thermal dissociation of vibrationally excited nitrogen molecules, as well as electronic excitation from all the vibrational levels of the nitrogen molecules, is also accounted for. The calculations show that the near-threshold associative ionization reaction, N(2D) + O(3P) → NO+ + e, is the major ionization mechanism in air at 2500 K < Tg < 4500 K while the ionization of NO molecules by electron impact is the dominant mechanism at lower gas temperatures and the high-threshold associative ionization reaction involving ground-state atoms dominates at higher temperatures. The exoergic associative ionization reaction, N(2P) + O(3P) → NO+ + e, also speeds up the ionization at the highest temperature values. The vibrational excitation of the gas significantly accelerates the production of N2(A3∑u+) molecules, which in turn increases the densities of excited N(2D,2P) atoms. Because the electron energy required for the excitation of the N2(A3∑u+) state from N2(X1∑g+, v) molecules (e.g., 6.2 eV for v = 0) is considerably lower than the ionization energy (9.27 eV) of the NO molecules, the reduced electric field begins to noticeably fall at Tg > 2500 K. The calculated plasma parameters agree with the available experimental data.

Exploration to generate atmospheric pressure glow discharge plasma in air

Atmospheric pressure glow discharge (APGD) plasma in air has high application value. In this paper, the methods of generating APGD plasma in air are discussed, and the characteristics of dielectric barrier discharge (DBD) in non-uniform electric field are studied. It makes sure that APGD in air is formed by DBD in alternating current electric field with using the absorbing electron capacity of electret materials to provide initial electrons and to end the discharge progress. Through designing electric field to form two-dimensional space varying electric field and three-dimensional space varying electric field, the development of electron avalanches in air-gap is suppressed effectively and a large space of APGD plasma in air is generated. Further, through combining electrode structures, a large area of APGD plasma in air is generated. On the other hand, by using the method of increasing the density of initial electrons, millimeter-gap glow discharge in atmospheric pressure air is formed, and a maximum gap distance between electrodes is 8 mm. By using the APGD plasma surface treatment device composed of contact electrodes, the surface modification of high polymer materials such as aramid fiber and polyester are studied and good effect of modifications is obtained. The present paper provides references for the researchers of industrial applications of plasma.

Transfer of Liquid Cathode Components to the Gas Phase and Their Effect on the Parameters of the Atmospheric Pressure DC Discharge

The transfer of solvent and components of dissolved substances from aqueous solutions to the gas phase under the action of atmospheric pressure air glow discharge was experimentally studied. solutions of NaCl, KCl, CuCl2, MgCl2, CaCl2, SrCl2, BaCl2, NaNO3, KNO3, Ba(NO3)2, Na2SO4, K2SO4, CuSO4 with concentrations of 0.1–0.5 mol/L were used as the cathodes of DC discharge at a current of 10–70 mA. The influence of the solution composition on cathode voltage drop and the electric field strength in plasma has been shown. Plasma emission spectra showed the appearance of metal atoms in the plasma requires threshold discharge current or threshold power input to the liquid cathode by ion bombardment. The threshold power values depend on the mass of hydrated cations and their concentration in solution. The efficiency of the transfer processes was characterized by transfer coefficients—the number of particles transferred from the liquid to the gas phase per one ion bombarding the cathode. Dependences of the transfer coefficients on the power dissipated in the cathode region and on the hydration energy of the cations were obtained. Experimental data on the rate of condensate accumulation in the special trap were used to estimate the concentrations of water molecules in the plasma.

Ethanol conversion in a DC atmospheric pressure glow discharge

Conversion of ethanol-water mixture into syngas in a DC atmospheric pressure air glow discharge with a plasma cathode has been investigated experimentally and theoretically. The electric power of discharge was varied from 100 W up to 250 W. Novel diagnostics based on the absorption infrared spectroscopy was developed and used to determine the syngas composition and the conversion parameters. The main components of syngas were: hydrogen, carbon monoxide, methane, ethylene and acetylene. The achieved degree of conversion to hydrogen was about 90%, with hydrogen content in conversion products being equal to 40%. A method for numerical simulation of the conversion process has been developed under an assumption that the role of discharge in the conversion process is purely thermal in nature. The experimental and numerical data were found to be in a good agreement.

In situ coupling of chitosan onto polypropylene foils by an Atmospheric Pressure Air Glow Discharge with a liquid cathode

Atmospheric air plasma treatment of chitosan solutions leads to degradation of chitosan molecules by OH radicals and is accompanied by a predominant cleavage of glycosidic linkages and by a decrease of the molecular weight. The degradation proceeds via first order kinetics with the rate constant of (5.73±0.22)×10−6s−1 and the energetic yield of chitosan bond scission of (2.4±0.2)×10−8mol/J. Products of degradation together with intact chitosan molecules adsorb and form coatings on polypropylene foils immersed into the solution that is being plasma treated. The plasma treatment results in strong binding of chitosan to polypropylene due to the formation of covalent bonds between the activated polymer surface and chitosan molecules. Plasma-driven crosslinking is responsible for the accumulation of compressive stress which leads to the development of buckling instabilities in the chitosan coatings.

Study on Glow Discharge Plasma Used in Polyester Surface Modification

To achieve an atmospheric pressure glow discharge (APGD) in air and modify the surface of polyester thread using plasma, the electric field distribution and discharge characteristics under different conditions were studied. We found that the region with a strong electric field, which was formed in a tiny gap between two electrodes constituting a line-line contact electrode structure, provided the initial electron for the entire discharge process. Thus, the discharge voltage was reduced. The dielectric barrier of the line-line contact electrodes can inhibit the generation of secondary electrons. Thus, the transient current pulse discharge was reduced significantly, and an APGD in air was achieved. We designed double layer line-line contact electrodes, which can generate the APGD on the surface of a material under treatment directly. A noticeable change in the surface morphology of polyester fiber was visualized with the aid of a scanning electron microscope (SEM). Two electrode structures - the multi-row line-line and double-helix line-line contact electrodes - were designed. A large area of the APGD plasma with flat and curved surfaces can be formed in air using these contact electrodes. This can improve the efficiency of surface treatment and is significant for the application of the APGD plasma in industries.

On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime

Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V and a current density at the cathode surface of about 11 A/cm2, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium.

Characteristics of a glow discharge in atmospheric pressure air over the water surface

The current-voltage characteristics, the amount of cathode fall, and the spectra of plasma radiation from different spatial domains are presented versus the molecular band intensity of products arising in an atmospheric-pressure air glow discharge over the distilled water surface. The plasma electron temperature is also reported. The distance to a liquid cathode or anode is varied from 1 to 10 mm at a discharge mean current of 10–36 mA.

A source of noncarcinogenic ultraviolet radiation with glow-discharge pumping in a metal needle-water surface electrode system

The results of optimization of a gas-discharge source of noncarcinogenic ultraviolet radiation, which is based on electron-oscillation transitions of products of the dissociation of water and nitrogen molecules (or small clusters), are presented. The lamp was pumped with an atmospheric-pressure glow discharge in air above the surface of distilled water.

Transient Processes During Formation of a Steady-State Glow Discharge in Air

This paper describes the investigation of an atmospheric-pressure glow discharge in air at a current of 0.05-0.3 A. Before the glow discharge is established, a preliminary nonsteady temporal stage is available in the gap. The principal process, which governs with the nonsteady-state discharge behavior, is the glow-to-spark transition phenomenon. The transition is initiated due to the explosive emission instability in the near-cathode layer of glow-type discharge that results in a microexplosion of the cathode surface and appearing of a spark cathode spot. At a low current, the spot is extinguished, so that the discharge starts burning again in one of the glow modes. After that, a new act of transition occurs and so on. The preliminary nonsteady-state stage ensures two prerequisites. First, an effective gas pressure decreases to a low value. Second, due to microexplosions, conditioning of the cathode surface is provided. Both factors facilitate establishing the normal glow discharge.

Atmospheric-Pressure Air Glow Discharge in a Three-Electrode Configuration

Nonthermal non-self-sustained dc glow discharge in atmospheric-pressure air was developed in a three-electrode configuration. A self-sustained normal dc atmospheric-pressure glow discharge in helium served as a ldquoplasma cathoderdquo for the main discharge in ambient air. Conditions of discharge transfer from helium volume to atmospheric air are under investigation. It is shown that a smooth transfer between the discharges in both volumes takes place only at small gaps between the ldquoplasma cathoderdquo and the third electrode (less than 5 mm) as the voltage applied to the air gap is increased. For larger gaps, this transfer is accompanied by discontinuous changes in both the voltage and current. After the jump, the discharge is contracted. But if the interelectrode gap is increased (more than 10 mm), then two forms of the discharge exist in one discharge space: diffuse and contracted.

Surface oxidation of polyethylene using an atmospheric pressure glow discharge with liquid electrolyte cathode

This study investigated the action of an atmospheric pressure air glow discharge (APGD) with aqueous electrolyte cathode onto the surface of polyethylene (PE) films. Distilled water and aqueous solutions of KCl and HCl were utilized as a cathode. The surface properties of PE were characterized by contact angle measurement followed by surface free energy calculation, Fourier transform infrared by attenuated total reflectance (FTIR-ATR), and XPS. After treating the PE surface, we observed OH groups, C O groups in ester, ketone, and carboxyl groups, and C O groups in unsaturated ketones and aldehydes. For a treatment time of 20 min and a discharge current of 40 mA, atomic concentrations of O and N were 12% and 2%, respectively, under distilled water application. Modification processes were able to improve the surface free energy of PE.

Experimental and Theoretical Studies on the Characteristics of Atmospheric Pressure Glow Discharge with Liquid Cathode

This study investigated the characteristics of an atmospheric pressure air-glow discharge with a liquid cathode. Distilled water was utilized as the cathode. The electric field strength, gas temperature as well as the emission intensity of some N2(C3Πu → B3Πg) and OH (A2Σ+ → X2Π) bands were measured at a discharge current ranging from 15 to 50 mA. Based upon the data obtained, the reduced electric field strength, E/N, and effective vibrational temperatures for N2(C3Πu, X1Σg+) and OH (A2Σ+) were examined. The electron energy distribution function (EEDF) and some electron parameters (average energy, electron density and rate coefficients) were obtained based on a numerical solution of the Boltzmann kinetic equation. The result showed that the EEDF was not in equilibrium and the effective vibrational temperatures for N2(C3Πu, X1Σg+) were essentially higher than the gas temperatures.

Study on the application possibilities of an atmospheric pressure glow discharge with liquid electrolyte cathode for the modification of polymer materials

We investigated the action of an atmospheric pressure air glow discharge (APGD) with aqueous electrolyte cathode onto the surface of polypropylene films and grey cotton fabric. Aqueous solutions of KCl, KBr and KI were utilized as a cathode. The surface properties of PP were characterized by contact angle measurement followed by surface free energy calculation, Fourier Transform Infrared by Attenuated Total Reflectance (FT-IR/ATR) analysis and height of water capillary rise for fabric. After treating PP surface, we observed OH-groups, C=O groups in ester, ketone and carboxyl groups, C=O groups in unsaturated ketones and aldehydes. Modification processes were able to improve the wettability of fabric as well as to accomplish the immobilization of some porphyrins onto PP surface.