Discharge Plasma System Research Articles

低毒性一液式推進剤を用いた1N級放電プラズマスラスタの燃焼室圧力評価

Green monopropellant thrusters, such as HAN-based and ADN-based monopropellant thruster, have been continuously developed as replacement for conventional hydrazine thrusters. A green monopropellant reaction system by utilizing discharge plasma of swirling noble gas has been proposed in substitution for the solid catalyst. Objective of this study is to evaluate the thrust performance of HAN-based monopropellant thruster with discharge plasma system by the measurement of combustion chamber pressure under vacuum. As a result, stable operations were confirmed by the measurement of combustion chamber pressure and internal pressure of argon-tube. At argon mass flow rate of 0.13g/s, HAN-based monopropellant mass flow rate of 0.31g/s and nozzle expansion ratio of 1, power consumption, c-star efficiency and rising time of combustion chamber pressure were 484W, 54% and 597ms, respectively. In addition, predicted thrust and specific impulse by the measured combustion chamber pressure were 282mN and 93s, respectively.

Magnetron Sputtering System for Deposition of Multinanolayered Coatings With Reactive Gas Activation in Microwave Discharge

The design of a dual gas magnetron system for ion sputtering of two source materials with an activation of a reactive gas in the remote microwave (MW) discharge for the deposition of multinanolayered coatings is presented. The design of the reactive gas activator with the electron cyclotron resonance was realized on the basis of the analysis of possible schemes for the formation of MW gas discharge plasma systems. The vacuum electron magnetron is used as a MW generator (2.45 GHz and ~800 W). Geometry of the electrodynamic part of the activator was selected by means of simulation with Comsol Multiphysics. The practical examination of the dual sputtering system was carried out by sputtering of Ti and B 4 C targets, while nitrogen was used as the reactive gas. The characteristics of the multinanolayered Ti-B-C-N coatings were studied and it was determined that the deposited coatings had the nc-TiN x /(a-BN+a-C) structure. The Knoop hardness of the coatings was found to be ~45 GPa, while the nanohardness was lower than Knoop ones by ~20%-30%. The presented sputtering system could be recommended for deposition of wear-resistant and protective coatings.

Effect of Nitriding Time on the Structural Evolution and Properties of Austenitic Stainless Steel Nitrided Using High Power Pulsed DC Glow Discharge Ar/N2 Plasma

A high power pulsed DC glow discharge plasma (HPPGDP) system was employed to perform fast nitriding of AISI 316 austenitic stainless steel in Ar and N2 atmosphere. In-situ optical emission spectroscopy and Infrared pyrometer measurements were used during the plasma nitriding to investigate the effect of dynamic plasma on the nitriding behaviour. SEM and EDX, XRD, Knoop indentation, and tribo-tests were used to characterise microstructures and properties of the nitrided austenitic stainless steel samples. HPPGDP produced high ionization of both Ar and N2 in the plasma that corresponded to dense ion bombardment on the biased steel samples to induce effective plasma surface heating and to form high nitrogen concentration on the biased steel surfaces, and therefore fast nitriding (> 10µm/hour) was achieved. Various phases were identified on the nitrided stainless steel samples formed from a predominantly a single phase of nitrogen supersaturated austenite to a multi-phase structure comprising chromium nitride, iron nitride and ferrite dependent on the nitriding time. All the nitrided AISI 316 austenitic stainless steel samples were evaluated with high hardness (up to 17.3 GPa) and exceptional sliding wear resistance against hardened steel balls and tungsten carbide balls.

Regeneration of Activated Carbon Spent with Phenol and Formation of Hydrogen Peroxide in a Pulsed Discharge Plasma System

A pulsed discharge plasma (PDP) system with a multineedle-to-plate geometry electrode was applied in this paper to investigate the regeneration of granular activated carbon (GAC) spent with phenol in the PDP system. Regeneration percentage of the GAC under different conditions of initial solution conductivity and pH values was studied to clarify the regeneration of the GAC by the PDP. Formation of hydrogen peroxide (H2O2) with the same solution conditions was also investigated in this paper. The obtained results show that there was the same changing trend of GAC regeneration and H2O2 formation under different solution conditions, which clarify the critical effect of •OH on the GAC regeneration in the PDP system. The methods of scanning electron microscope (SEM), Brunauer–Emmett–Teller, Boehm titration, and Fourier transform infrared spectroscopy (FTIR) were used in this paper to demonstrate the medication of the GAC by the PDP treatment. The obtained results show that the regenerated GAC could recover a partial pore structure compared with the original GAC by the SEM analysis. The surface area, micropore volume, and total pore volume of the regenerated GAC increased, while the mesopore volume and the macropore volume decreased on the regenerated GAC; comparing with the original GAC, there was higher amount of acidic functional groups and lower amount of basic functional groups on the surface of the regenerated GAC; the intensities of O–H, C=C, C=O, and C–O enhanced significantly by the FTIR analysis.

Investigation of the decolorization efficiency of two pin-to-plate corona discharge plasma system for industrial wastewater treatment

In this article, a dual pin-to-plate high-voltage corona discharge system is introduced to study experimentally the gap distance, the contact time, the effect of pin and plate materials, the thickness of ground plate and the conductivity on the amount of Acid Blue 25 dye color removal efficiency from polluted water. A study for the optimum air gap distance between dual pin and surface of Acid Blue 25 dye solution is carried out using 3D-EM simulator to find maximum electric field intensity at the tip of both pins. The outcomes display that the best gap for corona discharge is approximately 5 mm for 15-kV source. This separation is constant during the study of other factors. In addition, an investigation of the essential reactive species responsible for oxidation of the dye organic compounds (O3 in air discharge, O3 in water, and H2O2) during the experimental time is conducted. Three various materials such as: stainless steel, copper and aluminum are used for pins and plate. The maximum color removal efficiencies of Acid Blue 25 dyes are 99.03, 82.04, and 90.78% after treatment time 15 min for stainless steel, copper, and aluminum, respectively. Measurement results for the impact of thickness of an aluminum ground plate on color removal competence show color removal efficiencies of 86.3, 90.78, and 98.06% after treatment time 15 min for thicknesses of 2, 0.5, and 0.1 mm, respectively. The increasing of the solution conductivity leads to the reduction of decolorization efficiency. A kinetic model is used to define the performance of corona discharge system. The models of pseudo-zero-order, pseudo-first-order, and pseudo-second-order reaction kinetics are utilized to investigate the decolorization of Acid Blue 25 dye. The rate of degradation of Acid Blue 25 dye follows the pseudo-first-order kinetics in the dye concentration.

Influence of negative bias voltage on structural and mechanical properties of nanocrystalline TiNx thin films treated in hot cathode arc discharge plasma system

Ti thin films were grown by DC sputtering on a glass substrate and then nitrided in a hot cathode arc discharge plasma system, which is an effective approach to independently monitoring the plasma and nitriding parameters. The hardness of pristine Ti thin film is found to be ~3.06GPa, which increases upto ~16.08GPa with an increase in negative bias voltage to −140V and then decreases to ~15.05GPa for higher of −240V bias voltage. Similar kind of variation has been observed in crystallite size and surface roughness. Crystallite size is found to increase from 11.1nm (pristine Ti) to 14.8nm (for −140V) and then reduces to 11.9nm for –240V. Surface roughness increases from 2.78nm (pristine) to 6.84nm (for –140V), which is found to be 4.14nm for –240V. Optical and electrical measurements also reveal the strong impact of negative bias voltage on the bandgap and resistivity of the films. Above results are understood on the basis of diffusion of nitrogen ions for lower voltages and saturation of nitrogen ions in the host lattice for high voltages.

DLC Films Grown On Steel Using An Innovator Active Screen System For PECVD Technique

In this work, an active screen plasma discharge system based technology was incorporated in a PECVD reactor for DLC films growth, making it a new development in DLC films deposition. In this case, the active screen system is used to seek better electrons confinement, which might result in high ions density due to the collisions number increase, leading to a possible increase in ionization. DLC films were grown on steel substrates, using two variations of this system. In order to enhance adhesion between coating and substrate, a silicon interlayer was deposited, using different bias voltages. Morphological and structural characterization was performed by scanning electron microscopy, optical profilometry and Raman scattering spectroscopy. Tribological tests were performed by nanohardness, scratch and wear tests. Results showed that the plasma confinement promoted good films adhesion, which may be related to a high sub-implantation. This might be a consequence of the pressure decrease, as well as, to the ions energy distribution narrowing.

Remediation of PAH-contaminated soil by pulsed corona discharge plasma

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants of great environmental and health concern. PAHs are very persisted in soils and sediments which make it very difficult to remove them from soil. Therefore, remediation of PAH-contaminated sites has become an important environmental issue. The objective of this work was to study PAH degradation by pulsed corona discharge plasma system. Phenanthrene (Phe) was used as the model pollutant. The Phe-contaminated soil samples were prepared by adding appropriate amount of Phe dichlormethane solution (200 mg/L) into a given amount of pretreated soil, and Phe distributed uniformly in the soil at about 100 mg/kg. The experimental system mainly consisted of a pulse high-voltage power supply and a reactor vessel. The high-voltage electrode comprised of six stainless-steel needles and the ground electrode was a stainless-steel plate. The concentration of Phe was determined by HPLC system after being extracted out from soil. Effect of run parameters such as pulse voltage, pulse frequency, air flow rate, gas atmosphere, and initial concentration of Phe on Phe degradation was investigated, and the consumption of ozone during discharge process was also studied. The results showed that degradation efficiency of Phe (initial concentration 100 mg/kg) approached approximately 70 % after 40 min of discharge treatment under the conditions of pulse voltage 18 kV, pulse frequency 70 Hz, and air flow rate 0.8 L/min, which increased with the pulse voltage and pulse frequency due to the enhancement of input energy. An optimal air flow rate of 0.8 L/min was observed to obtain a maximum Phe degradation efficiency. Oxygen atmosphere favored Phe degradation due to high concentration of generated O-reagents, and ozone was found to act on Phe degradation. The concentration of Phe had influence on remediation capacity that increased with the amount of Phe in soil. The results confirmed that pulsed corona-discharge plasma was a potential method for remediation of PAH-contaminated soil. This study offered a viable treatment option for remediation of Phe-contaminated soil, which was expected to remove PAHs other than Phe from soil with further development.

Biosurfactant assisted synthesis of Fe3O4@rhamnolipid@BiOBr and its behaviour in plasma discharge system

A novel Fe3O4@rhamnolipid@BiOBr (FRB) was synthesized via a modified precipitation method and applied in the plasma discharge system. Rhamnolipid was used as biosurfactant to modify Fe3O4 by interacting with Fe3O4 via its aliphatic chain. The results show that the prepared FRB magnetic photocatalyst exhibited excellent photocatalytic activity and Fenton reaction behavior in the plasma discharge system. Meanwhile, the addition of FRB could improve energy efficiency of defluorination by 21.29 mg kW−1 h−1.

Simulation and Experimental Study for Degradation of Organic Dyes Using Dual pin‐to‐plate Corona Discharge Plasma reactors for Industrial Wastewater Treatment

AbstractThis work researches the possibility of increasing the dye removal efficiency from wastewater using nonthermal plasma. A study for the optimal air gap distance between dual pin and surface of Acid Blue 25 dye solution and thickness of ground plate is carried out using 3D‐EM simulator to find maximum electric field intensity at the tip of both pins. The consequences display that the best gap for corona discharge is approximately 5 mm using 15 kV source. In addition, the optimum plate thickness is 0.1 mm. These distance and thickness were mentioned are constant during the study of other factors. Dual pin‐to‐plate high‐voltage corona discharge plasma system is presented to investigation experimentally the gap distance, thickness of ground plate, initial dye concentration, pH solution and conductivity on the amount of Acid Blue 25 dye color removal efficiency from wastewater. There is a large consensus among the simulation and experimental work in the air gap and thickness of ground plate. Where the decolorization for air gap 5 mm is 95.74 at time 35 min compared with 91% and 17% for 1 mm and 20 mm gap distance respectively. Also, the discharge energy at each air gap are calculated. Measurement results for the impact of thickness of an Aluminum ground plate on color removal competence showed color removal efficiencies of 86.3%, 90.78% and 98.06%, after treatment time 15 min for thicknesses of 2, 0.5 and 0.1 mm respectively. The decolorization behavior utilizing dual pin‐to‐plate corona discharge plasma system display 82% pigment evacuation proficiency inside 11min. The complete decolorization was accomplished within 28min for distinctive examined introductory color focuses 5 ppm up to 100 ppm. Likewise, the impacts of conductivity by utilizing diverse salts as AlCl3, CaCl2, KCl and NaCl and with distinctive focuses have been explored. The rising of the solution conductivity leads to the reduction of decolorization efficiency. The decolorization efficiency and discharge energy are calculated at different concentration molarity for AlCl3, CaCl2, KCl and NaCl. It was observed that the presence of salts at the same concentration level substantially decreased the rate and the extent of decolorization. The results indicate that the optimum pH for the decolorization of Acid Blue 25 dye is in the range between 3 and 6. Furthermore the conductivity and discharge energy were measurement at each value of pH. Energy yield for decolorization and Electrical Energy per Order (EE/O) under different initial pH value were calculated. A kinetic model is used to define the performance of corona discharge system under different value of pH. The model of pseudo ‐zero, pseudo‐first order, and pseudo‐second order reactions kinetic are utilized to investigate the decolorization of Acid Blue 25 dye. The rate of degradation of Acid Blue 25 dye follows the pseudo‐first order kinetics in the dye concentration. Energy consumption requirements for decolorization was considered. The outcomes will be useful for designing the plasma treatment systems suitable for industrial wastewaters. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Decomposition of Aqueous Anatoxin-a Using Underwater Dielectric Barrier Discharge Plasma Created in a Porous Ceramic Tube

This work investigated the decomposition of aqueous anatoxin-a originated from cyanobacteria using an underwater dielectric barrier discharge plasma system based on a porous ceramic tube and an alternating current (AC) high voltage. Plasmatic gas generated inside the porous ceramic tube was uniformly dispersed in the form of numerous bubbles into the aqueous solution through the micro-pores of the ceramic tube, which allowed an effective contact between the plasmatic gas and the aqueous anatoxin-a solution. Effect of applied voltage, treatment time and the coexistence of nutrients such as , and glucose on the decomposition of anatoxin-a was examined. Chemical analyses of the plasma-treated anatoxin-a solution using liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC) were performed to elucidate the mineralization mechanisms. Increasing the voltage improved the anatoxin-a decomposition efficiency due to the increased discharge power, but the energy required to remove a given amount of anatoxin-a was similar, regardless of the voltage. At an applied voltage of 17.2 kV (oxygen flow rate: ), anatoxin-a at an initial concentration of (volume: 0.5 L) was successfully treated within 3 min. The chemical analyses using LC-MS and IC suggested that the intermediates with molecular weights of 123~161 produced by the attack of plasma-induced reactive species on anatoxin-a molecule were further oxidized to stable compounds such as acetic acid, formic acid and oxalic acid.

Study on remediation of phenanthrene contaminated soil by pulsed dielectric barrier discharge plasma: The role of active species

Polycyclic aromatic hydrocarbons (PAHs), which are detrimental to the environment and human health, are frequently found in soils. A pulsed dielectric barrier discharge (DBD) plasma system was employed for the remediation of phenanthrene (PHE)-contaminated soil. The role of active species was investigated by evaluating the effects of air flow rate and discharge voltage on the removal efficiency for their influence on the formation and transfer of these active species produced during plasma treatment. At an air flow rate of 0.6L/min and a voltage of 110V, the removal rate could reach 87.3% in 20min with an energy efficiency of 0.01mg/kJ. Radicals including O3, O, OH, OH+, N2∗, N2O+, and NO were identified by optical emission spectroscopy (OES). The contribution of ozone towards degradation was investigated by comparing ozone treatment with plasma treatment: ozone treatment was observed to account for 82.8% of the whole oxidation process. Theoretical calculations by Gaussian were employed to understand the degradation processes in combination of FTIR, GC–MS, and IC analysis and a possible degradation pathway of PHE was also proposed. Plasma technology was observed to be able to improve the biodegradability of PHE-contaminated soils. It was suggested that plasma treatment could be followed up by bio-remediation by taking advantage of the fast and effective plasma treatment (83.7% of PHE was removed in 20min) for heavily polluted organic soils.

Effect of activated carbon addition on H2O2 formation and dye decoloration in a pulsed discharge plasma system

A pulsed discharge plasma (PDP) system with circulating solution was established in the paper to investigate the rule of H2O2 formation in the system. The effect of activated carbon (AC) addition on the H2O2 formation and dye decoloration was also studied. H2O2 concentration, which indicated the amount of hydroxyl radical (OH) in a PDP system, under different conditions of electrode gap, peak pulse voltage, air flow rate, initial solution pH value and activated carbon (AC) addition was first investigated. The obtained results show that 8 mm was a better electrode gap condition for the H2O2 formation due to the stronger discharge intensity and faster contact of the active species and the AO7 molecules; the measured H2O2 concentration increased with the increase of peak pulse voltage and air flow rate; higher H2O2 concentration could be got under the condition of neutral solution and 4.0 g AC addition. The addition of AC was in favor for the increase of energy efficiency as well as acid orange 7 (AO7) decoloration, which confirmed the synergistic effect of AC addition in the PDP system.

Enhanced degradation of azo dye in wastewater by pulsed discharge plasma coupled with MWCNTs-TiO2/γ-Al2O3 composite photocatalyst

In order to improve the photocatalytic performance of TiO2 in pulsed discharge plasma systems, easily recycled multi-walled carbon nanotubes (MWCNTs)-TiO2 supported on γ-Al2O3 (MWCNTs-TiO2/γ-Al2O3) composite photocatalyst were prepared. The morphology and physicochemical properties of the prepared catalysts were investigated using XRD, SEM, FTIR and UV–vis spectroscopy. The photocatalytic activity was evaluated by degradation of azo dye acid orange II (AO7) in wastewater under pulsed discharge plasma. The results indicate that the MWCNTs-TiO2/γ-Al2O3 composite catalyst possesses enhanced photocatalytic activity facilitating the decomposition of AO7 compared with TiO2/γ-Al2O3 composite in pulsed discharge plasma systems. Under pulsed discharge plasma, almost 100% AO7 is degraded by the MWCNTs-TiO2/γ-Al2O3 composite after 60 min at optimal conditions. The degradation efficiency of AO7 is also affected by the dosage of the composite catalyst and pulsed discharge peak voltage. As the amount of MWCNTs-TiO2/γ-Al2O3 composite and pulsed discharge peak voltage increases, the degradation efficiency of AO7 increases. The photocatalyst was implemented for 6 cycles and the degradation efficiency of AO7 remains higher than 85% under pulsed discharge plasma. Results indicate that the catalyst displays easy separation and minimal deactivation after several uses. Possible decomposition mechanisms were also investigated. MWCNTs are capable of improving the photocatalytic activity of TiO2/γ-Al2O3 composite in pulsed discharge plasma systems primarily due to the photo-induced-electron absorption effect and the electron trap effect of MWCNTs. The results of this study establish the feasibility and potential implementation of MWCNTs-TiO2/γ-Al2O3 composites in pulsed discharge plasma systems for the degradation of dye wastewater.

Organic compounds removal in soil in a seven-needle-to-net pulsed discharge plasma system

A pulsed discharge plasma (PDP) system (a seven-needle-to-net electrode geometry) was built to degrade pyrene and p-nitrophenol in soil. Pulse discharge time, contents of the pollutants in the soil, the initial pH value of the soil, Kaolin and Cr6+ addition on removal of pollutants was investigated. The obtained results show that 60 min was the better treatment time; removal of organic compounds decreased with the increase of the contents; removal of pyrene was higher at neutral pH condition, while p-nitrophenol has more oxidation in the basic soil; Kaolin and Cr6+ addition has positive effect on the organic compounds degradation.

Removal of toluene in adsorption–discharge plasma systems over a nickel modified SBA-15 catalyst

In situ FT-IR spectra show the toluene adsorption process of SBA and Ni–SBA catalysts.

Comparative study between laboratory and large pilot scales for VOC's removal from gas streams in continuous flow surface discharge plasma

This work investigated the performance of Isovaleraldehyde (3-methylbutanal) removal from gas streams using continuous flow surface discharge plasma at room temperature. The feasibility of pollutant removal using up-scaled reactor was systematically assessed by monitoring removal efficiency and mineralization at different operational parameters, such as specific energy, air flow rate and inlet concentration. Results show that increasing flow rate lead to improve the removal capacity. For example, when flow rate extends two times, the removal capacity varies from 0.6 to 1.1gh−1. Moreover, when specific energy increased, both removal capacity and mineralization were enhanced. Additionally, a comparison between laboratory and pilot scales using surface discharge plasma system was carried out. A methodology of scaling up the surface discharge plasma system was proposed. In this context, removal capacities were compared for different continuous reactors: two reactors at laboratory scale (planar and cylindrical reactor), and pilot unit. The results suggest that the plasma reactor scale-up for pollutant removal can be feasible.

A study on improvement of discharge characteristic by using a transformer in a capacitively coupled plasma

In a plasma discharge system, the power loss at powered line, matching network, and other transmission line can affect the discharge characteristics such as the power transfer efficiency, voltage and current at powered electrode, and plasma density. In this paper, we propose a method to reduce power loss by using a step down transformer mounted between the matching network and the powered electrode in a capacitively coupled argon plasma. This step down transformer decreases the power loss by reducing the current flowing through the matching network and transmission line. As a result, the power transfer efficiency was increased about 5%–10% by using a step down transformer. However, the plasma density was dramatically increased compared to no transformer. This can be understood by the increase in ohmic heating and the decrease in dc-self bias. By simply mounting a transformer, improvement of discharge efficiency can be achieved in capacitively coupled plasmas.

Evaluation of the potentials of humic acid removal in water by gas phase surface discharge plasma

Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process. The mineralization of HA was analyzed by UV–Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment.

Multi-scale dynamics in externally excited glow discharge plasma

Time series analysis of fluctuations excited due to external perturbation in a dc glow discharge plasma system is presented. Analysis shows that the observed data is non-Gaussian in nature and has purely deterministic behavior. The oscillations are bi-periodic in nature without any occurrence of chaos with increasing discharge voltage. Two dominant frequencies 100 KHz and 200 KHz with background noise are observed. The Hurst coefficient is also evaluated for the data sets and is seen to be greater than 0.5 for all the cases. The observed bi-periodic oscillations have their origin due to some nonlinearities in the system. The observed frequencies are found to be due to ionization instability and ion acoustic instability.