Argon Dc Glow Discharge Research Articles

Plasma immobilization of azobenzene dye on polyamide 6 polymer

Plasma treatment of polymeric materials is a cost-effective and efficient technique to modify the surface and change the constituent unit configuration. This research investigates the effects of argon DC glow discharge plasma on pure and DR1 dye-loaded polyamide 6 polymer films and stabilization of dye on the surface. Plasma breaks some bonds and activates the surface through creating reactive structures such as free radical sites on the surface and increases tertiary amides on the surface of polymer. Besides, this process alters surface topographical characteristics and conformation of azobenzene dye which are effective on the durability of the dye on the surface. Plasma causes interactions of the dye with the polymer and immobilizes the dye on the polymer. On the other hand, these interactions lead to changes in the dye's optical and geometric isomeric activity and stability. This work studies the chemical and morphological changes of polyamide 6 by plasma with AFM and spectroscopic methods. Furthermore, the aging of nylon 6 films loaded with DR1 dye is measured, and the conformational changes of the dye are investigated. Plasma stabilizes the dye on the polymer surface through making changes of chemical and physical properties on the surface components.

Study of the Effect of Cathode Graphite on I-V Characteristics of Argon DC Glow Discharge

In this paper, the electrical properties of the glowing Argon discharge were studied for the purpose of knowing the parameters of the stable plasma work. The Argon plasma generated from the DC glow discharge has been examined. The glowing discharge system consists of two electrodes , The cathode is made of graphite with a disk of 8cm diameter and 1.7cm thickness. The anode is made of aluminum material with a disk of 8.8cm diameter and 1.1cm thickness. The electrical electrodes are enclosed in a glass cylinder made of pyrex containing argon gas.
 Several parameters which affect on the state of electric discharge, including gas pressure and the distance between electrodes.(I-V) curves of electrical discharge were measured at different pressures(0.075,0.32,0.65,0.75 and 1.12 torr) and distance between electrodes(2,4,6 and10 cm). By observing the electrical properties (I-V), it is concluded that the electric discharge of the plasma argon gas works within the abnormal glow area and is an important parameter in the deposition process. The higher discharge current of the argon plasma increases with increased pressure, the higher deposition rate was achieved.

Experiment and modeling of the pulsed lasing in a diode-pumped argon metastable laser

Diode-pumped metastable rare gas lasers are showing their potential for high-energy laser systems with intensive investigations carried out to understand their lasing characteristics. Here, we demonstrated pulsed lasing of a diode-pumped argon metastable laser based on a pulsed DC glow discharge in argon and helium mixtures for different discharge voltages and pressures. A transient rate equation model was established and solved to explain the cause of the pulsed lasing in our experiment. The insufficient production rate of argon metastable atoms (1s5) and the slow transfer rate out of the 1s4 state in the plasma during the lasing process were found to be the key reasons. This work may shed some light on the future design of plasma sources that have higher metastable atom production rates to achieve highly efficient continuous wave lasing.

Controlled photo-discharge of dust in a complex plasma

One of the limitations in studying dusty plasmas is that many of the important properties of the dust (like the charge) are directly coupled to the surrounding plasma conditions rather than being determined independently. The application of high-intensity ultraviolet (UV) sources to generate discharging photoelectric currents may provide an avenue for developing methods of controlling dust charge. Careful selection of the parameters of the UV source and dust material may even allow for this to be accomplished with minimal perturbation of the background plasma. The Auburn Magnetized Plasma Research Laboratory (MPRL) has developed a ‘proof-of-concept’ experiment for this controlled photo-discharging of dust; a high-intensity, near-UV source was used to produce large changes in the equilibrium positions of lanthanum hexaboride ( $\textrm {LaB}_6$ ) particles suspended in an argon DC glow discharge with negligible changes in the potential, density and temperature profiles of the background plasma. The shifts in equilibrium position of the dust are consistent with a reduction in dust charge. Video analysis is used to quantify the changes in position, velocity and acceleration of a test particle under the influence of the UV and Langmuir probes are used to measure the effects on the plasma.

KINETIC FEATURES OF PLASMA-CHEMICAL MODIFICATION OF POLYCARBONATE IN PLASMA IN ARGON - OXYGEN MIXTURE

This paper presents the results of experimental study of the processes of destruction and changes in the composition of the surface layer of a Lexan 8010 polycarbonate (PC) film during treatment in a positive column of a DC glow discharge in argon, oxygen, and their mixtures. The mass loss rates of the polymer samples were measured depending on the parameters of the discharge and the composition of the plasma-forming gas. The IR spectra of the polymer films after plasma exposure were analyzed. It was shown that the most noticeable changes in the sample destruction rate and the chemical composition of the surface layer occur when the oxygen content in the mixture is up to 20%. With a further increase in the O2 content in the plasma-forming mixture, the changes are insignificant. The main gaseous products of PC destruction in the plasma of an argon-oxygen mixture are H2, CO, and H2O molecules. In the first second after the discharge is turned on, H2 molecules are released at maximum rate and at a lower CO rate. The formation of carbon monoxide and hydrogen molecules occurs without the direct participation of oxygen under the action of active particles of argon plasma without the participation of active oxygen. Exposure to argon plasma leads to an increase in the oxygen content on the sample surface. In this case, the destruction of С – О, О–С(=О)–О bonds, which are part of the structure of the polycarbonate elementary unit, and the formation of new oxygen-containing bonds are observed. Etching of the polymer with active plasma particles leads to a change in the micro relief of the sample surface. A change in roughness and an increase in the concentration of polar functional groups increases the wettability of the PC film surface. A discussion of the possible mechanisms of the processes is made, which allows us to describe the observed results.

Influence of Nitrogen Admixture on Plasma Characteristics in a dc Argon Glow Discharge and in Afterglow

The present paper is based on the materials of the Invited Lecture presented at 29th Summer School and International Symposium on the Physics of Ionized Gases (28 August 2018–1 September 2018, Belgrade, Serbia). In the paper, the effect of nitrogen admixture on various characteristics of a dc glow discharge in argon (the volt-ampere characteristic, rate of plasma decay in the afterglow, discharge constriction condition, and formation of a partially constricted discharge) is considered.

Dusty plasma of a dc glow discharge in different noble gases

A self-consistent non-local model of the positive column of a dc glow discharge in helium, neon and argon with dust particles is presented. A kinetic Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions and dust particles, the Poisson equation for electric field were calculated self-consistently for different discharge conditions. The radial distributions of the discharge plasma and the dust particles parameters were obtained for different discharge gases. The influence of the buffer gas sort is revealed and discussed.

Cleaning Away the Oleic Acid Contaminant from Glass Surface by Negative Glow Plasma

Glass surfaces are contaminated by exposure to overheated oleic acid vapor and then cleaned by low-pressure plasma of a dc glow discharge in either air or argon. In this study, the oleic acid is used as model for hydrophobic organic contaminant and glass as a model for inorganic hydrophilic substrate. The processes of contamination and plasma cleaning are studied by atomic force microscopy (AFM), which revealed formation of oleic acid nanodroplets during contamination and, then, their removal during a few minutes of plasma cleaning. Water contact angle measurements show a much faster effect of plasma cleaning treatment, the contaminated surface changing from slightly hydrophobic to superhydrophilic in less than 30 s. This effect can be attributed to oxidation and hydroxylation of the oleic acid, as indicated by infrared absorption measurements. Also, the AFM indentation of the oleic acid nanodroplets after short plasma treatment indicates solidification of the remnant contaminant material.

Electrical Characteristics of an Argon Glow Discharge in the Presence of Metastable Atom Density

The paper deals with numerical modelling studies of DC glow discharge in argon with metastable atom density. The values of pressure is between 133.32 Pa and 330 Pa, and voltage ranges from 250 to 400 V in the case of input data taken from the Boltzmann equation in multi term approximation. In the frameworks, an analysis of glow discharge characteristics is carried out in the case of input data obtained from BOLISG+ code. As conclusion of these different input data in the same gas the output results are different and they appear in the cathode region. The spatio-temporal distributions of electron and ion densities, the potential and electric field, the mean electron energy and the metastable atom density are shown. A 1D fluid model is used to solve self-consistently the first three moments of the Boltzmann equation coupled with the Poisson's equation. The results are validated with those obtained by recent papers.

Dynamics contraction of DC glow discharge in argon

The article presents the results of modeling the dynamics contraction of DC glow discharge. The proposed model can be an important tool in the calculation of devices based on glow discharge plasma at high (up to atmospheric) pressure. Furthermore, the model can be used.

Experimental and theoretical study of the radial distribution of Ar(3P0) metastable atoms in a dc glow discharge in argon

Radial distributions of the number density of metastable Ar(3P0) atoms in the positive column of a dc glow discharge in argon were studied both experimentally and theoretically in a wide range of gas pressures (0.1–7 Torr) and discharge currents (10–50 mA). In experiments, glass discharge tubes 4 cm in diameter with clean inner surfaces and surfaces covered with a carbonitride or carbon film were utilized. Measurements were performed using an optical absorption technique known as the method of two identical tubes. Theoretical studies of the discharge plasma parameters under experimental conditions were carried out in the framework of a 1D (along the tube radius) discharge model. By a comparison of radial profiles measured and calculated at a gas pressure of 0.1 Torr the probability of elastic (without quenching) reflection of Ar(3P0) atoms from the tube wall was estimated. For a clean tube wall, this probability is about 0.5 ± 0.3, whereas for a wall covered with a carbonitride or carbon film, it is about zero.

Determination of the coefficient of reflection of metastable argon atoms from the discharge tube wall

Radial profiles of the density of metastable atoms Ar(3P2) in the positive column of a dc glow discharge in argon were measured. Gas-discharge glass tubes with clean inner surfaces and surfaces covered with a carbonitride or carbon film were utilized. The parameters of the discharge plasma under experimental conditions were calculated in the framework of a one-dimensional (along the tube radius) discharge model. The coefficient K of reflection of Ar(3P2) atoms from the tube wall was estimated by comparing the measured and calculated density profiles. It is found that, for a clean tube wall, the coefficient of reflection is K = 0.4 ± 0.2, whereas for a wall covered with a carbonitride or carbon film, it is K < 0.2.

Two-dimensional fluid modeling of DC glow discharge in argon at low pressure

The modeling of DC glow discharge in argon at the pressure p = 1.5 Torr and inter-electrode distance d = 1 cm was performed for different voltages and glow currents. For the first time, argon glow discharge is modeled using a two-dimensional (2D) fluid model with non-local ionization. A detailed numerical procedure for 2D fluid modeling is given. The 2D profiles of particle number densities and electric potential obtained from the fluid model with non-local ionization and the simple fluid model are presented and compared.

Memory effect and time correlations in breakdown initiation of DC glow discharge in argon and synthetic air

The memory effect and correlations of the statistical and formative time delay in argon and synthetic air DC glow discharge at low pressure were studied. The memory coefficients and ratios and Pearson's and Spearman's correlation coefficients were determined, ranging from about unity at low relaxation times and vanishing at the saturation region of the memory curves (determined by the background ionization). It was shown that the statistical ts and the formative time delay tf are correlated variables and the positive correlation between them was confirmed experimentally and theoretically.

Measurements and models of transient and stationary regimes of glow discharge in argon

The experimental and theoretical analyses of different regimes of argon DC glow discharge are reported. The experiments were carried out on the argon gas tube with a plane- parallel electrode system made from OFHC (oxygen-free high thermal conductivity) copper. Modelling of the static breakdown voltages was performed by simple fluid model. The applicability of fluid models for modelling of I - U (current-voltage) characteristics at different values of pd (pressure times inter-electrode distance) is tested. The formative time delays are determined from experiment and compared to modeled values obtained by [1D] and [2D] fluid models. The memory curve t̄d (τ) (the dependence of the mean value of breakdown time delay on the relaxation time) is presented and the main processes responsible for the memory effect were determined by applying the analytical and numerical models.

Investigation of Hot Cathode and Hollow Anode of Argon Glow Discharge Plasma

Hot cathode and hollow anode argon DC glow discharge plasma at different pressures of (0.04, 0.05, 0.06, 0.07, 0.09, 0.2, 0.4, and 0.8 mbar) has been investigated. The experiments were carried out under the influence of pressure and filament cathode current on voltage – current characteristics of glow discharge and its breakdown voltage. Plasma parameters have been measured and obtained using single probe method at fixed discharge current (Id=1.88 mA) and hollow anode diameter. A computer MATLAB program is performed for this purpose. It was shown that the discharge voltage – current characteristics curve has a positive resistance and represents an abnormal glow region at pressure (0.04 and 0.06) mbar for different filament current. The breakdown voltage increases as the filament current is increased. In different pressure, electron temperature shows different behavior with increasing filament current. Electron density varies nearly inversely with the filament current, but it is increase due to increase of pressure from (1 to 3 mbar), then tends to decrease for the higher pressure. There are two groups of electrons according to the two peaks of (EEDFs), and the peaks amplitude decrease, with the increases of both filament current and gas pressure.

Influence of ion drag force on radial distribution of dust particles and void formation in a DC glow discharge

A model of the positive column of a DC glow discharge in argon with dust particles is presented. The model is based on the solution of the non-local Boltzmann equation for the electron energy distribution function (EEDF), the drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particles density in a dust cloud is calculated according to an equilibrium Boltzmann distribution in the electrostatic field and under the action of the ion drag force. It is shown that if in the center of the discharge tube the ion drag force is larger than the electrostatic force, a dust-free region (void) in the central part of the dust cloud is formed. Otherwise (for a smaller ion drag force) the dust cloud is formed around the axis of the discharge tube without a void. In both cases, in the region of the dust cloud the ionization and recombination rates become almost equal to each other, and the radial component of the electric field is expelled from the dust cloud.

Spatial Evolution of the Dust-Acoustic Wave

Over the past twenty years, the dust-acoustic wave (DAW) has been a subject of intense study. In this paper, high-speed video imaging is employed to measure the evolution of wavefronts of a propagating DAW as it propagates through a weakly coupled dusty plasma system in an argon dc glow discharge plasma. In particular, measurements of the growth, saturation, and, then, damping of the wave mode as the wave propagates through the cloud are reported. It is observed that the wave amplitude initially exhibits rapid growth while the wavefront compresses. After this initial growth, the width of the wavefront remains relatively constant, while the amplitude of the wavefront evolves like the background dust medium. In some cases, it is also observed that the wave amplitude can decay more quickly than the background dust medium.

Energetic neutrals in the cathode sheath of argon direct-current discharges

We recently reported on the direct measurements of the energy distribution of energetic neutrals incident onto the cathode of an argon dc glow discharge [T. Ito and M. A. Cappelli, Appl. Phys. Lett. 90, 101503 (2007)]. In this paper, we provide a more extensive report of the experimental data, as well as direct comparisons to Monte Carlo simulations in which neutral-neutral and ion-neutral collision processes are modeled with differential scattering cross sections. The experimental results, which are limited to relatively small forward angle sampling in our present configuration, are found to be in excellent agreement with Monte Carlo simulations. The simulations reveal that high energy neutrals are striking the cathode with a wide range of angles, while ions are more anisotropic. Therefore, it is difficult to predict the neutral energy distribution with commonly used simple analytical models that do not consider scattering of neutrals within the sheath. We propose the use of an extended analytical model in this paper, which seems to provide reasonable energy distributions over the range of discharge voltage studied.

Hysteresis transition between diffuse and constricted modes of dc discharge in argon

The results of theoretical studies of hysteresis transition between the diffuse and constricted modes of a dc glow discharge in argon are presented. It has been shown that the experimentally observed hysteresis of the current voltage characteristic (CVC) at the transition from the constricted to the diffuse mode is caused by the nonlocal formation of the electron energy distribution function (EEDF) while taking into account the heterogeneity of radial fields, namely, the diffusion of high-energy electrons capable of producing gas ionization from the central (constricted) region. The effect of the non-local formation of the EEDF has been described approximately by introducing the effective temperature of the high-energy part of the EEDF and solving the equation for the radial profile of the high-energy part of the EEDF.