Nitrogen Glow Discharge Research Articles

Assessing Apparent Secondary Electron Yields from Current–Voltage Characteristics of Low-Pressure DC Glow Discharges in Nitrogen

Assessing Apparent Secondary Electron Yields from Current–Voltage Characteristics of Low-Pressure DC Glow Discharges in Nitrogen

Nitrogen plasma treated cotton fabrics coated with SiO2 followed by RGO deposition for water purification process

Experimental investigations have been carried out to modify the surface properties of Cotton fabrics using low temperature DC glow discharge nitrogen plasma. Plasma treatment is an eco-friendly, dry and clean process over wet chemical methods and does not suffer from any environmental and health concerns [1]. The important plasma parameters such as power and working pressure are kept constant with various treatment times (5, 15, 30, and 60 mins). The plasma-treated cotton fabrics are optimized by XRD, FTIR, and SEM. A comparative study has been done for the untreated and different treated fibers. Pure SiO2 is coated on untreated and nitrogen plasma treated cotton fabrics by sputtering method. The samples are coated for different sputtering times (10 and 30 min). Finally, Reduced Graphene Oxide (RGO) is coated on plasma treated SiO2 deposited fabrics. RGO is prepared by modified hummers methods [2]. Our results provide a way to develop a filter for water purification.

PIC/MCC simulation for a ns-pulsed glow discharge in nitrogen at sub-atmospheric pressure and analysis of its quasi-steady state physics

The present study investigates the physics of a nanosecond-pulsed microplasma operated at a pressure of 200 mbar with the help of a particle-in-cell simulation with Monte Carlo treatment of collision (PIC/MCC) and (semi-)analytical models. The discharge is ignited in a 1 mm gap between two parallel molybdenum electrodes by applying a voltage in the kV-range for several tens to hundreds of nanoseconds. A PIC/MCC simulation code is developed in order to describe the experiment performed under identical conditions. The simulation includes the external electrical circuit to perform ab-initio calculations of the complete experimental setup. Notable features of the PIC/MCC are (i) the adjustment of super-particle weights to reduce the computational load during drastic changes of the plasma density, which reaches values up to a few , and (ii) the inclusion of dissociative recombination of the ions, which is the key loss process for the charge carriers in the plasma bulk regions. The current and voltage waveforms obtained from the simulation are compared to the experimentally measured ones and good agreement is found. After ignition, the discharge establishes a quasi-steady state exhibiting spatial features similar to a conventional DC glow discharge. Using the PIC/MCC results, reasonable approximations are identified, which allow the development of various analytical fluid models for the individual plasma regions. These models are able to reproduce the key features of the discharge in agreement with the PIC/MCC results. The simplified models for the different discharge regions can be combined to describe the global behaviour of the discharge and—in a next step—might be used to develop computationally efficient global chemistry models that account for the different power dissipation mechanisms along the discharge gap.

The effect of cold glow discharge nitrogen plasma treatment of sisal fiber (Agave Sisalana) on sisal fiber reinforced epoxy composite

PurposeThe incompatibility of natural fibers with polymer matrices is one of the key obstacles restricting their use in polymer composites. The interfacial connection between the fibers and the matrix was weak resulting in a lack of mechanical properties in the composites. Chemical treatments are often used to change the surface features of plant fibers, yet these treatments have significant drawbacks such as using substantial amounts of liquid and chemicals. Plasma modification has recently become very popular as a viable option as it is easy, dry, ecologically friendly, time-saving and reduces energy consumption. This paper aims to explore plasma treatment for improving the surface adhesion characteristics of sisal fibers (SFs) without compromising the mechanical attributes of the fiber.Design/methodology/approachA cold glow discharge plasma (CGDP) modification using N2 gas at varied power densities of 80 W and 120 W for 0.5 h was conducted to improve the surface morphology and interfacial compatibility of SF. The mechanical characteristics of unmodified and CGDP-modified SF-reinforced epoxy composite (SFREC) were examined as per the American Society for Testing and Materials standards.FindingsThe cold glow discharge nitrogen plasma treatment of SF at 120 W (30 min) enhanced the SFREC by nearly 122.75% superior interlaminar shear strength, 71.09% greater flexural strength, 84.22% higher tensile strength and 109.74% higher elongation. The combination of improved surface roughness and more effective lignocellulosic exposure has been responsible for the increase in the mechanical characteristics of treated composites. The development of hydrophobicity in the SF had been induced by CGDP N2 modification and enhanced the size of crystals and crystalline structure by removing some unwanted constituents of the SF and etching the smooth lignin-rich surface layer of the SF particularly revealed via FTIR and XRD.Research limitations/implicationsChemical and physical treatments have been identified as the most efficient ways of treating the fiber surface. However, the huge amounts of liquids and chemicals needed in chemical methods and their exorbitant performance in terms of energy expenditure have limited their applicability in the past decades. The use of appropriate cohesion in addition to stimulating the biopolymer texture without changing its bulk polymer properties leads to the formation and establishment of plasma surface treatments that offer a unified, repeatable, cost-effective and environmentally benign replacement.Originality/valueThe authors are sure that this technology will be adopted by the polymer industry, aerospace, automotive and related sectors in the future.

Simulation of glow and arc discharges in nitrogen: effects of the cathode emission mechanisms

Experimental evidence in the literature has shown that low-current direct current nitrogen discharges can exist in both glow and arc regimes at atmospheric pressure. However, modelling investigations of the positive column that include the influence of the cathode phenomena are scarce. In this work we developed a 2D axisymmetric model of a plasma discharge in flowing nitrogen gas, studying the influence of the two cathode emission mechanisms—thermionic field emission and secondary electron emission—on the cathode region and the positive column. We show for an inlet gas flow velocity of 1 m s−1 in the current range of 80–160 mA, that the electron emission mechanism from the cathode greatly affects the size and temperature of the cathode region, but does not significantly influence the discharge column at atmospheric pressure. We also demonstrate that in the discharge column the electron density balance is local and the electron production and destruction is dominated by volume processes. With increasing flow velocity, the discharge contraction is enhanced due to the increased convective heat loss. The cross sectional area of the conductive region is strongly dependent on the gas velocity and heat conductivity of the gas.

Modification of Paschen's Law for Electrodes with Different Shapes and Materials using DC Nitrogen Glow Discharge

Modification of Paschen's Law for Electrodes with Different Shapes and Materials using DC Nitrogen Glow Discharge

Cold glow discharge nitrogen plasma treatment of banana and sisal fiber for mechanical and surface characterization improvement

Cold glow discharge nitrogen plasma treatment of banana and sisal fiber for mechanical and surface characterization improvement

Room-Temperature Synthesis of Titanium Nitride Using Metastable Nitrogen

The room-temperature synthesis of titanium nitride (TiN) is presented using the reaction of metastable nitrogen (MSN) with a titanium metal surface. The MSN is generated in a nitrogen glow discharge with plasma-ion filtering using a commercial direct analysis in real time (DART) source. The MSN is flowed over a titanium substrate at ambient pressure producing TiN surfaces that are ultra-clean and suitable for plasmonic applications. This is demonstrated using surface-enhanced infrared absorption spectroscopy (SEIRA), producing a 100-fold signal enhancement. Nitriding using MSN could find general applications in producing nitrided surfaces with small-scale structures.

Cold nitrogen plasma treated glass fiber warp knitted structural composites: mechanical properties and response surface analysis

This study reveals the characterization and mechanical properties of glass fiber warp knit structural fabric/vinyl ester resin composites treated by cold nitrogen glow discharge plasma. The effects of nitrogen plasma treating parameters (including power, flow rate, and time) on tensile and bending properties of glass fiber warp knit structural composites were investigated. It was shown that nitrogen plasma treatment enhanced the tensile and bending property of the glass fiber warp knit structural composites. SEM, FTIR and AFM characterized etching existing on the surface, C-N and N-H groups were introduced, and varying degrees of roughness. The response surface analysis represented that the nitrogen plasma treated glass fiber warp knit structural composites obtained optimized bending properties with the power ranging from 130 W to 160 W, the flow rate ranging from 8sccm to 9sccm, and the time ranging from 100s to 110s.

Effect on Physical and Thermal Properties of Corn Starch Treated by Energetic N₂ Extracted From Glow Discharge Plasma

In a typical nitrogen glow discharge plasma, a large number of energetic neutrals, N₂, are generated inside the cathode sheath. In this work, we are presenting a technique for the extraction of this energetic N₂ for the treatment of starch. The energetic neutrals N₂ were generated by the application of −500 V on a transparent cathode. On reaching the cathode, N₂^+ ions are absorbed; however, it is transparent to energetic N₂ neutrals molecules generated inside the sheath by charge exchange collisions, as the energetic N₂ neutrals are unaffected by the electric field and pass through the transparent cathode. The sample for treatment was placed below the transparent cathode and thus exposed to the energetic N₂ neutrals extracted from glow discharge plasma for a duration of 30 min. The impact of energetic N₂ neutral extracted from glow discharge plasma results in modification of physical and thermal properties of corn starch (maize starch). The physicochemical and morphological properties of treated and untreated samples were studied. The surface roughness of the plasma-treated corn starch increased significantly in comparison to the untreated sample. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) spectra confirmed that there is a considerable reduction in the semicrystalline nature and the polymer structure morphology of the corn starch. Scanning electron microscope (SEM) micrographs of samples show a substantial change in surface morphology and in size of the grains between the plasma-treated and untreated corn starch samples. The room-temperature thermal properties of the plasma-treated corn starch samples are measured using differential scanning calorimetry (DSC). The results confirm that the starch treated with energetic N₂ molecules has a lower gelatinization temperature and could be applied in food processing industries.

Damage evolution behavior of cold plasma treated glass fiber/vinyl ester resin composites under bending load by acoustic emission

This study reveals the preparation and mechanical characterization of cold plasma treated glass fiber/vinyl ester resin composites. The surface characteristics and bending failure mechanism of composites treated by oxygen, argon and nitrogen glow discharge plasma were studied by acoustic emission. The results showed that the bending resistance of argon plasma treated glass fiber reinforced composites exhibited highest. The composite treated by oxygen plasma produced AE signals with a frequency of more than 300 kHz, indicating that the fiber was damaged and the material was brittle, which reduced the strength and plasticity of the material. The bending stress in warp direction was greater than that in weft direction. The bending resistance of the cold plasma treated glass fiber/vinyl ester resin composites was the highest under the conditions of power 150W, flow rate 10sccm and time 120s.

Striations in moderate pressure dc driven nitrogen glow discharge

Plasma stratification has been studied for more than a century. Despite the many experimental studies reported on this topic, theoretical analyses and numerical modeling of this phenomenon have been mostly limited to rare gases. In this work, a one-dimensional fluid model with detailed kinetics of electrons and vibrationally excited molecules is employed to simulate moderate-pressure (i.e. a few Torrs) dc discharge in nitrogen in a 15.5 cm long tube of radius 0.55 cm. The model also considers ambipolar diffusion to account for the radial loss of ions and electrons to the wall. The proposed model predicts self-excited standing striations in nitrogen for a range of discharge currents. The impact of electron transport parameters and reaction rates obtained from a solution of local two-term and a multi-term Boltzmann equation on the predictions are assessed. In-depth kinetic analysis indicates that the striations result from the undulations in electron temperature caused due to the interaction between ionization and vibrational reactions. Furthermore, the vibrationally excited molecules associated with the lower energy levels are found to influence nitrogen plasma stratification and the striation pattern strongly. A balance between ionization processes and electron energy transport allows the formation of the observed standing striations. Simulations were conducted for a range of discharge current densities from ∼0.018 to 0.080 mA cm−2, for an operating pressure of 0.7 Torr. Parametric studies show that the striation length decreases with increasing discharge current. The predictions from the model are compared against experimental measurements and are found to agree favorably.

Effect of N-doping, exfoliation, defect-inducing of Ni-Fe layered double hydroxide (Ni-Fe LDH) nanosheets on catalytic hydrogen storage of N-ethylcarbazole over Ru/Ni-Fe LDH

Ultrafine Ru nanoparticles (RuNPs) supported on N-doped exfoliated Ni-Fe layered double hydroxide (LDH) nanosheets (Ru/Ni-Fe LDH) are prepared by nitrogen glow discharge plasma without adding any chemical stabilizers or reducing agents. The Ru/Ni-Fe LDHs were characterized by FT-IR, XPS, XRD, AFM, TEM, SEM and N2 physical adsorption–desorption analysis methods. The results show that the glow discharge plasma is not only able to reduce Ru3+ to Ru, but can also exfoliate Ni-Fe LDH into nanosheets and produce defects and dope N into the layered structure of Ni-Fe LDH. RuNPs with an average particle size of 1.81 nm were successfully obtained and well dispersed on the surface of N-doped exfoliated Ni-Fe LDH nanosheets. The experimental results from the catalytic hydrogenation of N-ethylcarbazole (NEC) over Ru/Ni-Fe LDH show that the NEC conversion is 100%, the dodecahydro-N-ethylcarbazole (12H-NEC) selectivity is 97.43%, and the mass hydrogen storage capacity is 5.74 wt% under the reaction temperature and pressure of 120 °C and 6 MPa for 80 min. The apparent activation energy is 44.86 kJ/mol.

In situ preparation of Pd nanoparticles on N-doped graphitized carbon derived from ZIF-67 by nitrogen glow-discharge plasma for the catalytic dehydrogenation of dodecahydro-N-ethylcarbazole

To date, liquid organic hydrogen carrier technology has been generally considered to be one of the most promising solutions for the storage and transportation of hydrogen. Addressing several issues, including high hydrogen release temperature and low initial release rate, is key to this technology. Pd catalysts (Pd/NpGC) supported on porous N-doped partially graphitized ZIF-67-derived carbon (NpGC) were prepared in situ using nitrogen glow discharge plasma. The structure, composition, and morphology of the prepared catalysts were characterized by XRD, Raman spectroscopy, TEM, XPS, and N2 adsorption–desorption. During the calcination of ZIF-67, porous N-doped carbon was formed and partially graphitized under the influence of Co. The Pd nanoparticles (Pd NPs) of the Pd/NpGC catalysts had an average size of 3.2 nm with higher dispersion and a higher fraction of Pd (111) facets. In the process of Pd2+ reduction, NpGC was doped twice with N simultaneously. The synergy between highly active Pd NPs and N-doped partially graphitized carriers (NpGC) reduced the electronic binding energy of Pd and improved the catalytic performance of Pd/NpGC for hydrogen production from dodecahydro-N-ethylcarbazole (H12-NEC). The results showed that the amount of hydrogen released in the dehydrogenation reaction at 180℃ was 4.06 wt% after 1 h and 5.76 wt%, after 10 h. The H12-NEC conversion rate was 100%, the selectivity of N-ethylcarbazole (NEC) was 98.72%, and the final dehydrogenation reached 99.20%.

Key chemical reaction pathways in a helium-nitrogen atmospheric glow discharge plasma based on a global model coupled with the genetic algorithm and dynamic programming

Determination of the key chemical reaction pathways in cold atmospheric plasmas (CAPs) is of great importance not only for understanding the spatiotemporal evolutions of the key plasma parameters during discharges but also for improving the plasma materials processing qualities. In this paper, a novel chemical reaction reduction method (CRRM) is proposed by using the global fluid model coupled with the genetic algorithm and the dynamic programming technique. With the aid of this newly developed CRRM, the key chemical reaction pathways can be automatically screened with a high computational efficiency under a pre-set critical calculation accuracy for the atmospheric pure helium and helium–nitrogen glow discharge plasmas. By comparing the calculated key plasma parameters, e.g., the species number densities, electron temperatures, voltage–current characteristics, based on the simplified models and their corresponding full models with those of the experimentally measured data, the reliability of the CRRM itself and the established key chemical reaction database for the atmospheric pure helium and helium–nitrogen CAPs are validated. This research also provides a general method for screening the key chemical reaction pathways for various low-temperature plasma sources.

Strong-Field-Induced Air Lasing in Nitrogen Glow Discharge PlasmaSupported in part by the National Natural Science Foundation of China (Grant Nos. 61625501 and 62027822), and the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM).

We investigate air lasing at 391 nm, induced by strong laser fields in a nitrogen glow discharge plasma. We generate forward air lasing on the – transition at 391 nm by irradiating an intense 35-fs, 800-nm laser in a pure nitrogen gas, finding that the 391-nm lasing quenches when the nitrogen gas is electrically discharged. In contrast, the 391-nm fluorescence measured from the side of the laser beam is strongly enhanced, demonstrating that this discharge promotes the population in the state. By comparing the lasing and fluorescence spectra of the nitrogen gas obtained in the discharged and laser-induced plasma, we show that the quenching of lasing is caused by the efficient suppression of population inversion between the and states of , in which a much higher population occurs in the state in the discharge plasma. Our results clarify the important role of population inversion in generating air lasing, and also indicate the potential for the enhancement of lasing via further manipulation of the population in the state in the discharged medium.

Synthesis and Surface Characterization of PMMA Polymer Films in Pure Oxygen, Argon, and Nitrogen Glow Discharge Plasma

The anticorrosion effect and biocompatibility property of Poly (methyl methacrylate) (PMMA) materials have been used in a variety of commercially available products and medical devices for many years. In this work, the treatment of surfaces prepared PMMA films by oxygen, argon and nitrogen plasma, requires understanding the effect of low energy ions on the surface modification of the film of PMMA. Due to this, the samples of prepared PMMA were exposed to three different gases at the same discharge conditions. Changes within the morphology and surface hydrophilicity of the treated samples were characterized by optical microscope images and the measurements of contact angle. Treatment of PMMA with O2, N2, Ar gases displayed a decreasing in the contact angle that results in increasing surface free energy. Oxygen –plasma treatment of PMMA films leads to high aspect ratio topography, with increased roughness for (5-30) minute process durations.

In situ preparation of highly dispersed Pd supported on exfoliated layered double hydroxides via nitrogen plasma for 4-nitrophenol reduction.

In this work, a simple and environmental-friendly nitrogen glow discharge plasma reduction method has been developed for synthesizing palladium nanoparticles (PdNPs) supported on exfoliated Mg-Al-layered double hydroxide (Pd/LDH) catalysts. The as-prepared catalysts were characterized by means of characterizations methods, which contain X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared (FT-IR). Highly dispersed ultrafine PdNPs were supported on exfoliated, defect-induced LDHs uniformly without agglomeration. The effects of treatment time of nitrogen plasma and Pd loading amount on structure, morphology, and catalytic performance of Pd/LDHs were investigated. The comparisons of structure and morphology between LDHs and Pd/LDHs were also discussed. The average particle size of as-synthesized PdNPs with face-centered cubic structure is 2.01 nm, which ranges from 1.18 to 3.01 nm. Nitrogen plasma cannot only reduce Pd2+, but also exfoliate LDHs, introduce defects, and even destroy the structure of LDHs. The Pd/LDH catalyst with 1 wt% Pd loading under nitrogen plasma treatment for 60 min showed the best catalytic performance in 4-nitrophenol reduction. The turnover frequency (TOF) of as-prepared catalyst is 20-fold higher than that of commercial Pd/C catalyst.

Determination of Electron Excitation Temperature in an RF-DC Hollow Cathode Nitrogen Plasma

An RF-DC nitrogen glow discharge generated inside a rectangular hollow cathode was investigated as a source of nitrogen atoms. The plasma was produced at a frequency of 2 MHz at a low-pressure condition at the range of 30 to 100 Pa. The power generator was controlled at the RF voltage of 150 V and DC bias voltage of -500 V. The atomic nitrogen species have been detected by employing an optical emission spectroscopy technique. The use of a rectangular hollow cathode proves that the increase of nitrogen atoms species at a wavelength range of 700-900 nm was produced from the dissociation process of molecular nitrogen species. The present work aims to determine the electron excitation temperature based on the OES spectra. The excitation temperature was calculated by using the Boltzmann plot method. The result is the excitation temperature determined at the range of 0.59 to 0.71 eV. The excitation temperature in the hollow cathode was decreased with the increasing pressure.

In situpreparation of ultrafine Ru nanocatalyst supported on nitrogen‐doped layered double hydroxide by nitrogen glow discharge plasma for catalytic hydrogenation ofN‐ethylcarbazole

Ultrafine Ru nanoparticles (RuNPs) supported on nitrogen‐doped layered double hydroxide (Ru/LDH) werein situprepared by nitrogen glow discharge plasma (nGDP) without adding any chemical reducing agents or stabilizers. The as‐synthesized Ru/LDH catalysts were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. During treatment with nGDP, the reduction of Ru3+and nitrogen doping were carried out simultaneously. The resulting RuNPs has a narrow particle size distribution of 1.41–2.61 nm, an ultrafine average particle size of 1.86 nm, and were uniformly dispersed on nitrogen‐doped LDH. The complexation of RuNPs and O/N‐containing functional groups on LDH improve the catalytic activity and stability of Ru/LDH. The catalyst exhibited excellent properties for the hydrogenation reaction ofN‐ethylcarbazole (NEC). The conversion of NEC and the selectivity of 12H‐NEC were 100% and 99.06% for 1 hr at 120°C and 6 MPa H2, respectively. The mass hydrogen storage capacity was 5.78 wt%. The apparent activation energy was 35.78 kJ/mol.