Low-pressure Glow Discharge Research Articles

Plasma-assisted surface modification of MXene/carbon nanofiber electrodes for electrochemical energy storage

Inferior ion diffusion and relatively low electrochemically active sites of MXene-based electrodes make them becoming a major challenge to develop advanced electrode. Surface modification of electrodes using non-thermal plasma is a great way to suppress these challenges through providing more space for energy storage and facilitating the diffusion of electrolyte ions. Herein, the effect of nitrogen and oxygen plasma treatments on MXene/carbon nanofiber electrode is reported to enhance the electrochemical performance. In this work, Ti3C2Tx MXene/CNF composites were fabricated using a hybrid needleless electrospinning/plasma method for the electrochemical energy storage. Surface modification of the composites was performed by a DBD plasma reactor under N2 and O2 gases at low-pressure glow discharge as a two-step plasma treatment process. The results revealed that total pore volume and the surface area of the plasma-treated Ti3C2Tx/CNF composite increased considerably due to the N2 and O2 plasma treatments. It was found that the electrochemical active surface area of the N2/O2-plasma-treated Ti3C2Tx/CNF electrode enhanced by approximately two times compared to the non-treated one, leading to the specific capacitance of 162 F/g at 1 A g−1 in a 2 M KOH electrolyte. The increase in electrochemical activity arises from separate doping of N2 and O2 plasma, which not only improves the pore structure and wettability, but also modifies the electrical conductivity and capacitance of the electrode. The N2/O2-plasma-treated Ti3C2Tx/CNF electrode achieved excellent cycling stability with 124 % capacitance retention after 10,000 cycles, while the capacitance retention of the pure N2 and O2-plasma-treated Ti3C2Tx/CNF electrodes as well as the non-treated one were 111 %, 105 % and 98 %, respectively. Additionally, an asymmetric supercapacitor N2/O2-plasma-treated Ti3C2Tx/CNF//AC based on the N2/O2-plasma-treated Ti3C2Tx/CNF as a positive electrode and activated carbon (AC) as a negative electrode was successfully constructed, which demonstrated an energy density of 26.3 Wh kg−1 with a power density of 750 W kg−1 at the current density of 1 A g−1 with excellent capacitance retention (102 %) after 5000 cycles. This work provides a highly efficient method for the surface modification of MXene-based electrodes through non-thermal plasma treatment.

Dyeing jute-cotton blended fabric with natural dyes: A chemical-free approach of LPGD plasma technology using O2 and N2 gases

In response to growing environmental concerns in the textile industry, this study investigates the effects of a low-pressure glow discharge (LPGD) plasma with oxygen (O2) and nitrogen (N2) gases on the dyeing process of jute-cotton (JC) blended fabrics, using coffee extract as a natural dye source. The hydrophilic properties of all the JC blended fabric samples were enhanced due to plasma treatments. The contact angles of the samples were significantly decreased from 131° to 52° (O2) and 55° (N2) after 20 minutes of plasma treatment. Compositional analysis revealed new functional groups e.g., CO and N−H, on the fabric's surface after plasma treatment. Surface morphology analysis indicated that the surface roughness of the treated fabric was increased with plasma treatment time. The improvement of the wicking properties of the fabric with contact time was also observed. All the plasma-treated fabric samples exhibited good colour strength (k/s), wash fastness, and rubbing fastness. After plasma treatment with O2 gas for 20 minutes, the k/s value had increased from 3.6 to 4.9. Washing and rubbing (dry) color fasting ratings were enhanced from 1 to 3 and 2–4, respectively, following a 20-minute plasma treatment with O2 gas. Although both O2 and N2 plasma treatment showed a significant impact on the dyeing properties of JC blended fabric, O2 gas provided better results compared to N2 gas plasma treatment.

Physics-informed neural networks based on source term decoupled and its application in discharge plasma simulation

In recent years, the artificial intelligence computing paradigm represented by physics-informed neural networks (PINNs) has received great attention in the field of plasma numerical simulation. However, the plasma chemical system considered in related research is relatively simplified, and the research on solving the more complex multi-particle low-temperature fluid model based on PINNs is still blank. In more complex chemical systems, the coupling relationship between particle densities and between particle densities and mean electron energy become more intricate. Therefore, the applicability of PINNs in dealing with sophisticated reaction systems needs further exploring and improving. In this work, we propose a general PINN framework (source term decoupled PINNs, Std-PINNs) for solving multi-particle low-temperature plasma fluid model. By introducing equivalent positive ions and replacing each particle transport equation with the current continuity equation as a physical constraint, Std-PINN splits the entire solution process into the training processes of two neural networks, realizing the decoupling of the source term of the heavy particle transport equation from the electron density and mean electron energy, which greatly reduces the complexity of neural network training. In this work, the application of Std-PINNs to solving multi-particle low-temperature plasma fluid models is demonstrated through two classic discharge cases with different complexity of reaction systems (low-pressure argon glow discharge and atmospheric-pressure helium glow discharge) and the performance of Std-PINN is compared with that of conventional PINN and finite element method (FEM). The results show that the training results output from the traditional PINN are completely incorrect due to the strong coupling correlation of each physical variable through the source terms of each particle transport equation, while the <i>L</i><sub>2</sub> relative error between Std-PINN and FEM results can reach up to ~10<sup>–2</sup> , thus verifying the feasibility of Std-PINN in simulating multi-particle plasma fluid model. Std-PINN expands the application of deep learning method to modeling complex physical systems and provides new ideas for conducting low-temperature plasma simulations. In addition, this study provides novel insights into the field of artificial intelligence scientific computing: the mathematical form that describes the state of a physical system is not unique. By introducing equivalent physical variables, equations suitable for neural network solutions can be derived and combined with observable data to simplify problems.

Numerical Study of the Influence of Pressure on the Dynamics and Complex Bifurcation Processes of the Low-Pressure DC Glow Discharge

Numerical Study of the Influence of Pressure on the Dynamics and Complex Bifurcation Processes of the Low-Pressure DC Glow Discharge

Chemical constitution of coatings deposited remotely by activation of hexamethyldisiloxane in positive column plasma of glow discharge in argon flow

The present work deals with the chemical constitution of coatings deposited by plasma activation of hexamethyldisiloxane in positive column plasma of a low-pressure DC glow discharge in an argon flow (mass flow rate 230 mg/min). X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) are used to analyze deposit chemistry. The substance is complex and consists of many constitutional units forming branched and cross-linked irregular macromolecules. Chemical constitution depends on both discharge current (10–60 mA) and monomer flow rate (1–10 mg/min). Using the specific energy (SE) and Arrhenius-like approach, the threshold energy for the plasma polymerization of HMDSO has been estimated to be 12 ± 1 eV. Two regimes of the plasma chemical system have been identified. At SE near the threshold energy (from 5 to 40 eV/molecule), polymethylsiloxane-like coatings are deposited and variation of SE practically does not lead to changes in chemical constitution, but significantly affects the mass yield of deposit. At specific energies much higher than threshold energy, polymethylhydroxysiloxane-like coatings are formed; the coating structure is strongly SE-dependent, while the mass yield of the deposit does not change.

Experimental investigation of the period-adding bifurcation route to chaos in plasma.

Since the characteristic timescales of the various transport processes inside the discharge plasma span several orders of magnitude, it can be regarded as a typical fast-slow system. Interestingly, in this work, a special kind of complex oscillatory dynamics composed of a series of large-amplitude relaxation oscillations and small-amplitude near-harmonic oscillations, namely, mixed-mode oscillations (MMOs), was observed. By using the ballast resistance as the control parameter, a period-adding bifurcation sequence of the MMOs, i.e., from L^{s} to L^{s+1}, was obtained in a low-pressure DC glow discharge system. Meanwhile, a series of intermittently chaotic regions caused by inverse saddle-node bifurcation was embedded between the two adjacent periodic windows. The formation mechanism of MMOs was analyzed, and the results indicated that the competition between electron production and electron loss plays an important role. Meanwhile, the nonlinear time series analysis technique was used to study the dynamic behavior quantitatively. The attractor in the reconstructed phase space indicated the existence of the homoclinic orbits of type Γ^{-}. In addition, by calculating the largest Lyapunov exponent (LLE), the chaotic nature of these states was confirmed and quantitatively characterized. With the decrease in the ballast resistance, the return map of the chaotic state gradually changed from the nearly one-dimensional single-peak structure to the multibranch structure, which indicates that the dissipation of the system decreased. By further calculating the correlation dimension, it was shown that the complexity of the strange attractors increased for higher-order chaotic states.

From Basics to Frontiers: A Comprehensive Review of Plasma-Modified and Plasma-Synthesized Polymer Films.

This comprehensive review begins by tracing the historical development and progress of cold plasma technology as an innovative approach to polymer engineering. The study emphasizes the versatility of cold plasma derived from a variety of sources including low-pressure glow discharges (e.g., radiofrequency capacitively coupled plasmas) and atmospheric pressure plasmas (e.g., dielectric barrier devices, piezoelectric plasmas). It critically examines key operational parameters such as reduced electric field, pressure, discharge type, gas type and flow rate, substrate temperature, gap, and how these variables affect the properties of the synthesized or modified polymers. This review also discusses the application of cold plasma in polymer surface modification, underscoring how changes in surface properties (e.g., wettability, adhesion, biocompatibility) can be achieved by controlling various surface processes (etching, roughening, crosslinking, functionalization, crystallinity). A detailed examination of Plasma-Enhanced Chemical Vapor Deposition (PECVD) reveals its efficacy in producing thin polymeric films from an array of precursors. Yasuda's models, Rapid Step-Growth Polymerization (RSGP) and Competitive Ablation Polymerization (CAP), are explained as fundamental mechanisms underpinning plasma-assisted deposition and polymerization processes. Then, the wide array of applications of cold plasma technology is explored, from the biomedical field, where it is used in creating smart drug delivery systems and biodegradable polymer implants, to its role in enhancing the performance of membrane-based filtration systems crucial for water purification, gas separation, and energy production. It investigates the potential for improving the properties of bioplastics and the exciting prospects for developing self-healing materials using this technology.

Investigation of Kinetics of Fast Electrons and Parameters of Negative-Glow Plasma in a Low-Pressure Glow Discharge in Helium

Investigation of Kinetics of Fast Electrons and Parameters of Negative-Glow Plasma in a Low-Pressure Glow Discharge in Helium

Numerical simulation of the hysteresis of the transition from the stationary to oscillatory regime in the low-pressure DC glow discharge

As a typical highly nonlinear medium, laboratory plasmas can exhibit abundant nonlinear phenomena. It is well known that the presence of negative differential conductivity can cause the system to exhibit temporal chaotic oscillations when a DC glow discharge is operated in the subnormal glow discharge regime. In addition, for a nonlinear system, the hysteresis often occurs due to the coexistence of multiple attractors. In this work, a two-dimensional plasma fluid model based on the drift-diffusion approximation is developed to study the hysteresis phenomenon of the nonlinear dynamical behaviors of the low-pressure DC glow discharge. The results demonstrate that the initial discharge conditions selected in calculations will influence the nonlinear dynamical behaviors significantly that the system exhibits. Hysteresis can be observed from the voltage waveform when the applied voltage is altered to allow the system to work between the stationary discharge regime and the oscillatory discharge regime. In the hysteresis region, the system exhibits bi-stable characteristics. Near the critical point, the dynamical behaviors of the system will jump from the stationary state to the oscillatory state under small perturbations and the reverse adjustment of control parameters will not immediately restore the original stationary state, which is a typical characteristic of the subcritical Hopf bifurcation.

Introduction and verification of FEDM, an open-source FEniCS-based discharge modelling code

This paper introduces the finite element discharge modelling (FEDM) code, which was developed using the open-source computing platform FEniCS (https://fenicsproject.org). Building on FEniCS, the FEDM code utilises the finite element method to solve partial differential equations. It extends FEniCS with features that allow the automated implementation and numerical solution of fully coupled fluid-Poisson models including an arbitrary number of particle balance equations. The code is verified using the method of exact solutions and benchmarking. The physically based examples of a time-of-flight experiment, a positive streamer discharge in atmospheric-pressure air and a low-pressure glow discharge in argon are used as rigorous test cases for the developed modelling code and to illustrate its capabilities. The performance of the code is compared to the commercial software package COMSOL Multiphysics® and a comparable parallel speed-up is obtained. It is shown that the iterative solver implemented by FEDM performs particularly well on high-performance compute clusters.

Influence of the Percentage of Argon in the Ar–N2 Gas Mixture on the Relative Number of Ar+, N2+, N, and N+ Particles in the Plasma of a Non-Self-Sustained Low-Pressure Glow Discharge With a Hollow Cathode

Influence of the Percentage of Argon in the Ar–N2 Gas Mixture on the Relative Number of Ar+, N2+, N, and N+ Particles in the Plasma of a Non-Self-Sustained Low-Pressure Glow Discharge With a Hollow Cathode

Comparison between 1D radial and 0D global models for low-pressure oxygen DC glow discharges

This work focuses on the comparison between a zero-dimensional (0D) global model (LoKI) and a one-dimensional (1D) radial fluid model for the positive column of oxygen DC glow discharges in a tube of 1 cm inner radius at pressures between 0.5 Torr and 10 Torr. The data used in the two models are the same, so that the difference between the models is reduced to dimensionality. A good agreement is found between the two models on the main discharge parameters (gas temperature, electron density, reduced electric field and dissociation fraction), with relative differences below 5%. The agreement on other species average number densities, charged and neutral, is slightly worse, with relative differences increasing with pressure from 11% at 0.5 Torr to 57% at 10 Torr. The success of the 0D global model in describing these plasmas through volume averaged quantities decreases with pressure, due to pressure-driven narrowing of radial profiles. Hence, in the studied conditions, we recommend the use of volume-averaged models only in the pressure range up to 10 Torr.

INFLUENCE OF THE MAGNETIC FIELD OF THE CURRENT PASSING THROUGH THE ANODE ON A GLOW DISCHARGE IN A COAXIAL SYSTEM

To study the influence of the magnetic field on the normal low-pressure glow discharge, an electrode coaxial system with a meshy tubular cathode and an internal anode was used. A current was passed through the anode to obtain the azimuthal magnetic field crossed with electric field. Oscillography of the signals from the electric probe and photodiode, together with video recording, made it possible to establish the movement of the discharge luminous region along the electrodes. When AC current with a frequency of 50 Hz was passed through the anode, the discharge movement was oscillatory – from one end of the system to another.

Characterization of hexamethyldisiloxane plasma polymerization in a DC glow discharge in an argon flow

This work aims to study hexamethyldisiloxane (HMDSO) plasma polymerization in a low-pressure glow discharge in a gas flow. HMDSO was activated in a plasma-chemical reactor with a DC glow discharge in an argon flow. The argon flow (the mass flow rate was 230 mg/min) was injected in the direction of the anode from the cathode. HMDSO vapors were injected into the plasma-chemical reactor either through the hollow cathode or through the inlet located between the cathode and the anode. Polymer coatings were deposited on the substrates located in a vacuum chamber. Plasma polymerization was characterized based on the mass of coatings deposited under varying external conditions: the HMDSO mass flow rate (1–10 mg/min), the average discharge current (6–60 mA), and the discharge power (6–30 W). The operation modes of the plasma-chemical system were determined. The chemical structure of the coatings was analyzed using the infrared spectroscopy. The processes occurring in different regions of the glow discharge and at the interface near the substrate surface are proposed. A DC glow discharge in a gas flow can be used for local deposition of polymer coatings on the surface of dielectric or conductive materials.

Theoretical Analysis of Magnetic Pinch Glow Discharge Plasma at Low Pressure

In the process of electron beam and plasma interaction, the angular magnetic field produced by the electron beam affects the physical parameters of the plasma. In this paper, first, the Thomson ionization coefficient under the condition of cross field is derived. Second, based on a magnetohydrodynamics method, the axial distribution of plasma density in the positive column of low-pressure glow discharge under the magnetic field is deduced, and the effect of the angular magnetic field on glow discharge plasma is studied. Finally, the above results are verified by numerical simulation. The results show that when the pressure is 10 Pa, the plasma density first increases and then decreases with the increase of magnetic field. When the pressure is 0.1 Pa, the plasma density decreases with the increase of magnetic field.

Operating modes in a low-pressure glow discharge with hollow cathode

The paper deals with investigations of the discharge in hydrogen in conditions close to those for the trigger units of pseudospark switches. The following modes of discharge sustaining are classified: the Townsend discharge, the suppressed glow discharge with hollow cathode, the intermediate mode of the gradual transition from the suppressed discharge to the ordinary glow discharge, and the ordinary discharge in which the negative glow plasma occupies the whole depth of the cathode cavity. As applied to the ordinary discharge, the theoretical model that offers a possibility to estimate the negative glow parameters is developed. In the current range 1.6–10 mA the electron densities in the negative glow region are 1.7–8.7 108 cm−3. The interpretation for the mechanism of the current passage to the anode is also proposed based on the model. In particular, the explanation is given for the fact that the region of the positive column plasma near the flat anode appears at a low discharge current.

Modeling of CO2 conversion in low-pressure glow discharges in CO2-N2 mixtures

An approach for evaluation of plasma parameters and conversion factor in glow discharges in CO2–N2 mixtures at low pressures is presented. In the framework of this approach, analytical expressions relating plasma characteristics (the electric field, the gas temperature) in discharges in the mixtures with those in pure CO2 have been obtained. It is shown that dissociation of CO2 molecules in collisions with electronically excited N2 molecules gives substantial contribution to the conversion rate. Obtained dependences of the plasma parameters and conversion factor on the nitrogen molar fraction agree with available experimental data.

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.

Mechanism Analysis of the Effect of Axial Magnetic Field on Low Pressure Glow Discharge

The effect of axial magnetic field on glow discharge parameters at low pressure is studied in this article. First, Paschen&#x2019;s law under axial magnetic field is modified. The results show that under the same conditions, the magnetic field will increase the breakdown voltage of glow discharge. The experimental results are consistent with the theoretical analysis, but the experimental value is higher than the theoretical value. Second, the physical model of parallel field glow discharge is established, and the plasma density of glow discharge under different pressure, discharge spacing, and magnetic field is studied. The results show that the plasma density increases with the increase in magnetic field at low pressure; at high pressure, the larger the magnetic field, the smaller the plasma density. At the same position, the plasma density increases with the increase in discharge spacing in weak magnetic field, and it decreases with the increase in discharge spacing in strong magnetic field. When the surface area of the magnet is only 20&#x0025; of the surface area of the anode and cathode, the radial nonuniformity of the magnetic field makes the plasma density reach the maximum when the radial <inline-formula> <tex-math notation="LaTeX">$r =0$ </tex-math></inline-formula>.

Numerical study of nitrogen bulk dissociation in DC magnetron discharge in Ar+N2 mixture

The effect of the composition of the gas feed mixture on the dissociation rate constant of molecular nitrogen is examined by numerical solving the Boltzmann equation written in a two-term approximation for conditions corresponding to nitride aluminum films deposition. By solving of macroscopic balance equations in volume occupied with plasmas of stationary low-pressure glow discharge in a nitrogen-argon mixture the atomic nitrogen density was determined. It’s shown that there is a maximum of atomic nitrogen density at certain stoichiometry of gas feed mixture.