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Optical emission spectroscopy studies of vanadium plasma in a cathodic-arc discharge in a nitrogen atmosphere have been carried out. Spectral lines of neutral atoms and ions of the cathode material V, V1+, and V2+, and nitrogen N2 and N2+ were observed in the discharge plasma. Analysis and comparison of the intensity of vanadium and nitrogen spectral lines as a function of nitrogen pressure showed that in vacuum excited ions V2+ and V+ are registered, with increasing pressure, the lines V+*, N2*, and N2+* are observed, and at pressures above 0.5 Pa, the neutral vanadium lines are additionally registered. The electron temperature of Te decreases from 5.9 to 3–4 eV with increasing pressure. Studies of cross-sectional scanning electron microscopy images of VN coatings deposited at different nitrogen pressures have shown that a dense, homogeneous, fine-grained microstructure is formed in the coating when the number of neutral V in the plasma is low, while in the presence of a large number of neutrals, the coating structure changes to a dense structure with columnar growth. [ABSTRACT FROM AUTHOR]

Transpolar arcs (TPAs) are often cusp‐aligned. Especially when multiple TPAs appear simultaneously, they join at the auroral signature of the cusp. Here we investigate the dayside connection point of TPAs using Defense Meteorological Satellite Program measurements and identify three cases where the tip of the TPA ends in a localized brightening. One is a typical cusp spot with a TPA attached. The cusp appears just poleward of the oval with a near circular shape. In the second case, multiple cusp spots are observed over a 3 MLT wide region, each connected to a TPA. In the third case, the brightening at the tip of a TPA is identified as high‐latitude dayside aurora (HiLDA). Cusp aurora appears between the HiLDA and the duskside oval. Plasma flows and particle characteristics indicate a lobe origin of the HiLDA. Our results indicate a more complicated connection between TPAs and dayside aurora than previously anticipated. Plain Language Summary: Transpolar arcs are large‐scale auroral structures that span the polar cap, often connecting the nightside with the dayside part of the auroral oval. In case multiple transpolar arcs appear simultaneously in one hemisphere, they typically join at an auroral intensification on the dayside, which is believed to be the auroral signature of the magnetospheric cusp. In this study, we investigate the dayside region where transpolar arcs connect to auroral intensifications with the help of particle data and semi‐global auroral images from the Defense Meteorological Satellite Program's four satellites (F16, F17, F18, F19) in those cases where the satellites pass right through that region. In this study, we focus on three distinctly different cases. The first two differ in shape, but coincide with cusp aurora, as indicated by strong proton precipitation. The third case consists of arcs connected with a HiLDA (High Latitude Dayside Aurora), which by definition consists of a monoenergetic electron population and a lack of ions. We show for the first time a TPA located in the middle of the polar cap, where the tip of the arc connects with a HiLDA. Key Points: We present three distinct cases of bright dayside oval connection points of transpolar arcs, using DMSP particle data and plasma flowsThe arc connection point is in case I a typical cusp spot, in case II two cusp spots each connected to an arc, and in case III a HiLDAWe show that not only oval‐aligned arcs but also transpolar arcs in the middle of the polar cap can be attached to HiLDA [ABSTRACT FROM AUTHOR]

Lightning protection of large‐scale photovoltaic power stations and grid‐connected lines has gradually become a difficult problem with more and more large‐scale photovoltaic power stations connected to the State Grid. In order to enable large photovoltaic power station to continue and stably operate, this paper targeted the grid‐connected transmission line and designed the spiral multi‐pair blowing device. The device leads the plasma arc to take on a spiral path, and the energy of plasma arc is sprayed out at the convection fracture of the unit and continuously consumed. Experiment results show that the device can extinguish lightning current in 2.1 ms and restore the transmission voltage to the normal level. The lightning protection device has the effectiveness of arc extinguishing, and it is beneficial to reduce lightning trip rate of transmission line of large‐scale photovoltaic power stations. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The paper is devoted to investigation of spectral parameters of constricted arc plasma, as a foundation for further development of basic approaches to controlling of plasma-arc technologies of material treatment and welding. The relevance of application of spectrometric analysis of the welding arc consists in obtaining the possibility of sufficiently accurate control of its temperature and energy input into the product being welded, recording initiation of weld defects (internal pores), determination of atmospheric oxygen ingress into the weld pool, etc. The spectral composition, temperature and concentration of the constricted welding arc plasma were determined in the paper to more precisely define its physical characteristics at 80 and 100 A currents, in order to establish the further applicability of dynamic spectral analysis of a constricted plasma arc in control of welding processes. As modern spectrometers with CCD-detectors of the spectral range of 200 ÷ 1100 nm have the resolution of the order of 0.35 nm, which 2-3 times exceeds the quantization step by the measured wavelength, and may lead to considerable errors, an approach is proposed to increase the accuracy of spectrometric measurements to acceptable values. Radiation spectra of the constricted welding arc measured in the wavelength range of 650 ÷ 1000 nm allowed within the model of local thermodynamic equilibrium calculating the excitation temperature of the main spectral range components: Ar I and O I. It was established that the excitation temperature of electron levels of Ar atoms in the welding arc plasma only weakly depends on the discharge current, and it is equal to 13500 ± 500 K. Excitation temperature of O I electron levels was equal to 10000 ± 500 K at arc current of 100 A and to 7200 ± 500 K at 80 A current. Electron density of high-current welding arc plasma was measured by Stark broadening of Ar I lines (696.543; 772.4; 912.3 nm). It was found that with the rise of current of the constricted welding arc by 20%, an increase of charge concentration in the arc plasma by 1.5 times and of its temperature by 1.2 times are observed. [ABSTRACT FROM AUTHOR]

ABSTRACT It is imperative to develop the simulation of vacuum arcs as a tool to aid electrode design in vacuum circuit breakers. Although the development of electromagnetic thermo‐fluid simulations for vacuum arcs has been reported, most of them do not take cathode sheath phenomena into account and have not been able to reproduce vacuum arc phenomena, especially cathode spots. As the first step, the cathode sheath voltage, cathode surface electric field, and temperature and field (T‐F) electron emission current were analyzed numerically on the basis of the space charge in the cathode sheath. In this study, the cathode sheath was assumed to exist when the charge density induced on the cathode surface is positive, and the temperature and density of vacuum arc plasma and cathode temperature, which are physical quantities obtained by electromagnetic thermo‐fluid simulation, were used as parameters of the analysis. As a result, the cathode sheath voltage, electric field, and electron emission current density can be calculated from the vacuum arc plasma temperature, density, and cathode temperature. Numerical results show that the electron emission current density has a dominant effect on the presence or absence of the cathode sheath. [ABSTRACT FROM AUTHOR]

Regulating the phase ratio between austenite and ferrite in welded joints is crucial for welding super duplex stainless steel. Nitrogen plays a significant role in maintaining an optimal phase ratio. In this study, the focusing gas channel of gas-focused plasma arc welding was utilized to introduce nitrogen into the arc plasma, which was then transferred to the weld pool. Experiments with and without nitrogen addition were designed and conducted to examine the effects of nitrogen on the microstructure and properties of SDSS 2507 weld joints. The results show that nitrogen addition increased the austenite content in the weld metal from 22.2% to 40.2%. Nitrogen also altered the microstructure of the austenite, changing it from thin grain boundary austenite and small intragranular austenite to a large volume of coarse, side-plate Widmanstätten austenite. The ferrite in the weld metal exhibited a preferred orientation during growth, while the austenite showed a disordered orientation. Additionally, the maximum texture intensity of the ferrite decreased with nitrogen addition. Nitrogen addition led to an increase in the microhardness of the austenite in the weld metal, attributed to the solid solution strengthening effect of nitrogen and increased dislocation tangling, while it decreased the microhardness of the ferrite. This study enhances the welding theory of 2507 super duplex stainless steel and guides the practical application of gas-focused plasma arc welding for 2507 super duplex stainless steel. [ABSTRACT FROM AUTHOR]

Plasma technology is based on a simple physical principle. When more energy enters the gas, it ionizes and becomes the fourth state of matter, the energy-dense plasma. The studies carried out within the scope of this study were designed to create microchannels on lamellar glass using an improved redesign of the current plasma arc device, which is the main subject of the paper. The created microchannel is examined at the microscale. Experimental analysis was conducted considering the effect of plasma on the effect of microchannel quality. We performed an experimental design study to determine the optimal parameter levels for improving microchannel quality. The predicted results have been validated with the experimental results. An experimental design study provides useful results, such as information about the distance between the probes, pulse duration, and material temperature, which enhances the channel dimensions. The improved device can be utilized effectively to establish microchannel processing in practice. [ABSTRACT FROM AUTHOR]

Electrical and fast imaging measurements are performed on an experimental device designed to study the dynamics of electric arcs in the DC regime. The work presented here investigates the relationship between electrical fluctuations and material ejection from the electrode surface. Cross-analysis of the electrical and imaging data reveals a significant correlation between electrical fluctuations in the kHz range and particle emission from the electrode surface. Different types of ejection are presented and a study of the dynamics of the ejected particles is carried out through the analysis of a statistically significant number of trajectories. [ABSTRACT FROM AUTHOR]

Background: Silver nanoparticles are extensively researched for their antimicrobial properties. Cold atmospheric plasma, containing reactive oxygen and nitrogen species, is increasingly used for disinfecting microbes, wound healing, and cancer treatment. Therefore, this study examined the effect of water activated by dielectric barrier discharge (DBD) plasma and gliding arc discharge plasma on the antimicrobial activity of silver nanoparticles from Alborzia kermanshahica. Methods: Silver nanoparticles were synthesized using the boiling method, as well as biomass from Alborzia kermanshahica extract grown in water activated by DBD and GA plasma. The physicochemical properties of the synthesized nanoparticles were evaluated using UV-vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), zeta potential analysis, transmission electron microscopy (TEM), and gas chromatography-mass spectrometry (GC-MS) analysis. Additionally, the disk diffusion method was used to assess the antimicrobial efficacy of the manufactured nanoparticles against both Gram-positive and Gram-negative bacteria. Results: The spectroscopy results verified the presence of silver nanoparticles, indicating their biosynthesis. The highest amount of absorption (1.049) belonged to the nanoparticles synthesized by boiling under GA plasma conditions. Comparing the FTIR spectra of the plasma-treated samples with DBD and GA revealed that the DBD-treated samples had more intense peaks, indicating that the DBD method proved to be more effective in enhancing the functional groups on the silver nanoparticles. The DLS results revealed that the boiling method synthesized silver nanoparticles under DBD plasma treatment had a smaller particle size (149.89 nm) with a PDI of 0.251 compared to the GA method, and the DBD method produced nanoparticles with a higher zeta potential (27.7 mV) than the GA method, indicating greater stability of the biosynthesized nanoparticles. Moreover, the highest antimicrobial properties against E. coli (14.333 ± 0.47 mm) were found in the DBD-treated nanoparticles. TEM tests confirmed that spherical nanoparticles attacked the E. coli bacterial membrane, causing cell membrane destruction and cell death. The GC-MS results showed that compounds like 2-methylfuran, 3-methylbutanal, 2-methylbutanal, 3-hydroxy-2-butanone, benzaldehyde, 2-phenylethanol, and 3-octen-2-ol were much higher in the samples that were treated with DBD compared to the samples that were treated with GA plasma. Conclusion: The research indicated that DBD plasma was more efficient than GA plasma in boosting the antimicrobial characteristics of nanoparticles. These results might be a cornerstone for future advancements in utilizing cold plasma to create nanoparticles with enhanced antimicrobial properties. [ABSTRACT FROM AUTHOR]

A unified one-dimensional model of an arc plasma in air, between copper electrodes, that includes the change of the gap distance is presented. The occurrence of multiple reversals of the electric field and the anode voltage drop is observed. The evolution of the spatial distribution of the electron and heavy particle temperatures with the gap distance and the opening speed is also studied. The model quantitatively predicts a number of plasma properties under conditions that are relevant to the contact separation in low-voltage switching devices. [ABSTRACT FROM AUTHOR]

Low-cost micromanufacturing technique for forming copper foils into desired micro-parts plays an important role in facilitating the widespread application of copper foil. Here, the pulsed arc plasma generated by the pulsed voltage was used as a heat source to achieve thermal stress–induced bending of copper foil in an electrical discharge machining (EDM) machine. Metallic foil with a thickness of 0.1 mm and a cylindrical rod with scanning motion were used for the first time as tool electrodes in the EDM bending of workpieces. The effect of various processing parameters, such as polarity, machining time, discharge current, duty factor, and discharge frequency, on the bending angle was investigated by optical microscopy. The main factors affecting the bending angle and their working mechanisms were analyzed in depth. Experimental results showed that the bending angle of the copper foil increases with the increase of the discharge energy, which was mainly attributed to the increasing thermal gradient along the thickness direction of the copper foil. When the copper foil was used as the anode, the carbon deposition phenomenon in the copper foil effectively reduced the material removal caused by the pulsed arc plasma, which contributes to the surface integrity and performance of the copper foil. Furthermore, several typical bend-formed parts, including curved, sawtooth, and S-shapes, were formed using pulsed arc plasma. This work proves that pulsed arc plasma is a reliable and cost-effective heat source for achieving thermal stress–induced bending of copper foil. [ABSTRACT FROM AUTHOR]

Ni-WC composite coating was prepared on Q235 steel substrate by plasma transfer arc (PTA) with welding current ranging from 70 A to 85 A. The results show that the dissolution behaviour of WC particles and the elemental diffusion at the interface promoted by the increased welding current promote the formation and evolution of precipitates, including M 7 (B, C) 3 and M 6 C. The increased current reduced the volume fraction of WC particles in the coating, but increased that of the precipitates. At welding currents of 75 A and 80 A, dendritic-like M 7 (B, C) 3 presented a regular distribution at the bottom of the coating. At a welding current of 80 A, M 6 C phase began to form at the bottom of the coating. When the welding current reached 85 A, the dendritic structure was broken, and the M 6 C phase aggregated and grew. The Ni-WC coating had visible delamination. WC particles at the upper part of the coating dissolved more severely compared to those at the middle and bottom of the coating. Ni 3 Si compound was formed at the upper and middle of the coating, and it had a crystal orientation relationship of [011] Ni3Si ∥[011] γ-Ni , (11-1) Ni3Si ∥(11-1) γ-Ni , (−200) Ni3Si ∥(-200) γ-Ni , (-11-1) Ni3Si 1.3° from (-11-1) γ-Ni with γ-Ni. The average hardness of the coating decreased slightly due to the dissolution of WC, but the hardness at the interface increased, showing an improved bonding of the interface. The newly formed high hardness precipitates can share the load coming from the friction paired ball, thus reducing CoF and wear loss of the coating. [ABSTRACT FROM AUTHOR]

This study investigated the influence of printing parameters and strategies on the morphological characteristics of austenitic stainless steel beads deposited on carbon steel substrates, using plasma directed energy deposition (DED). The experimental setup varied the welding current, wire feed speed, and torch travel speed, and we analyzed three printing strategies: simple-linear, overlapping, and oscillating. Moreover, advanced 3D scanning and computational analysis were used to assess the key morphological features, including bead width and height. The results showed that the computational model developed by using parabolic assumptions accurately predicted the geometric outcomes of the overlapping beads. The oscillating printing strategy was the one that showed improved morphological uniformity and bead substrate wettability, so these features were used for multi-layer component manufacturing. The use of equivalent wavelength–amplitude values resulted in maximum combinations of bead height and width. Moreover, cost-effective carbon steel substrates were feasibly used in microstructural and elemental analyses, with the latter ones confirming the alignment of the bead composition with the wire-fed material. Overall, this study provides practical insights for optimizing plasma DED processes, thus enhancing the efficiency and quality of metal component manufacturing. [ABSTRACT FROM AUTHOR]

In the present study, 3D non-woven needle-punched preform (NPP) Cf–SiCm composite with 7.5 pct volume fraction of carbon fiber is prepared via liquid silicon infiltration technique and characterized for microstructure, phase formation and mechanical behaviors. Additionally, the composite is subjected to plasma arc jet tests for evaluation of ablation resistance under ultra-high temperature oxidation environment. The dense composite (density ~ 2.5 to 2.6 g/cm3) contains β-SiC phase due to the reaction between infiltrated molten silicon and carbon matrix surrounding the carbon fibers. The resultant Cf–SiCm composite shows high hardness and high abrasion resistance due to a higher proportion of hard SiC matrix as well as exhibits various toughening mechanisms from the carbon fiber reinforcement causing a delay in fracture. It also contains excellent resistance to thermal shock and thermo-oxidative erosion resistance during plasma arc jet ablation test without any visible crack or damage on the exposed surface. [ABSTRACT FROM AUTHOR]

Electric arcs are a necessary heat source in many industrial processes that take place in Submerged Arc Furnaces (SAFs). Arcs exhibit non-linear electrical characteristics and behave in a complex manner. Therefore, an improved understanding of their behavior enables better control of furnace operation. Modeling of industrial arcs is a multiphysics process that involves simultaneously solving several coupled physical phenomena, such as electromagnetics, fluid dynamics, and heat transfer, including a radiative heat transfer from the plasma arc. Coupling fluid dynamics and electromagnetics is known as Magnetohydrodynamics (MHD). For practical applications, however, there are also simpler approaches to arc modeling, either based on simplified physical principles or empirical behavior. In this paper, a combined Cassie–Mayr model (CMM) and a channel arc model (CAM) are implemented and coupled with a submerged arc furnace electrical circuit model. The complete circuit model parameters such as resistances and inductances are estimated using modeling of a full size furnace, and then, actual measurements from a SAF are used to validate the models by comparing current and voltage waveform. Both models are then used to estimate harmonic distortion in a SAF for different arc current ratios, which should help operators to estimate the arc current in real time thus be able to lower and raise the electrode to keep operating conditions constant. [ABSTRACT FROM AUTHOR]

Modeling analysis of underwater pulsed arc discharge can predict the characteristics of plasma channels, providing theoretical guidance for the practical application of underwater pulsed discharge. Due to the complexity of experimental diagnostics for 'kA'-level underwater pulsed discharge, there is currently a lack of precise experimental data to support the initial value selection and result optimization of the modeling. This paper established a plasma channel model for underwater pulsed arc discharge. In conjunction with the Saha ionization equilibrium equation, the model was capable of simulating the current, pressure, temperature, and electron density of the channel after gap breakdown. By utilizing spectroscopic diagnostic data and a multi-objective optimization algorithm, the initial values and key parameters of the model were reasonably determined. The simulation results were in good agreement with the experimental diagnostic results, reasonably representing the trends in electron density and blackbody radiation temperature. Moreover, the model was applicable for reasonably explaining the emission spectral mechanism of the arc channel and shock waves prediction under different discharge conditions. [ABSTRACT FROM AUTHOR]

Heterostructure engineering has been proposed as a promising approach to construct high-efficiency bifunctional electrocatalyst for overall water splitting. Integrated transition metal and metal oxide heterointerfaces with carbon nanomaterials are designed to facilitate electrocatalytic performance toward overall water splitting. Fe/MnO heterostructures are fabricated on graphene using a one-step DC arc plasma technology. In this way, increased electrochemically active specific areas, accelerated charge transfer, and proper interfacial electronic structure can be achieved. Benefiting from the synergistic effect of multiple materials, fabricated Fe/MnO/graphene heterointerfaces can make the redistribution of electrons between heterointerfaces, which effectively optimizes adsorption/desorption energy of the reaction intermediates. Fe/MnO/graphene delivers excellent catalytic activity with only 362 mV and 339 mV overpotential to reach current density of 10 mA cm−2 for OER and HER and exceptional long-term stability in alkaline solution. As electrocatalyst at both the cathode and the anode of an alkaline electrolyzer simultaneously, Fe/MnO/graphene electrocatalyst requires a cell voltage of 1.987 V at a current density of 10 mA cm−2 for overall water splitting. Therefore, this work offers a feasible route to construct hierarchically nanohybrids as bifunctional electrocatalysts by combining transition metal and metal oxide with carbon nanomaterials. • Fe–MnO/C nanocomposite with heterointerfaces is prepared by arc-discharge method. • The heterogeneous nanostructures exhibit prominent performance of water splitting. • The coupling and synergistic effects reduce the kinetic barriers of HER and OER. [ABSTRACT FROM AUTHOR]

In this paper, the laser and arc are shifted laterally to change the position and energy distribution of arc discharge, which provides a new idea and theoretical basis for solving the narrow gap welding defects of titanium alloy thick plate. In this study, the effect of transverse offset distance between laser and arc (DLAP) on the discharge characteristics of hybrid heat source coupling and the flow characteristics of molten pool was studied by using the welding method of plate surfacing. The dynamic behavior of the arc plasma, the molten pool, and the keyhole was monitored in real time, and the plasma spectral information was collected to analyze its energy distribution characteristics. The results show that under different DLAP conditions, the charged plasma of the hybrid heat source has two different states: strong coupling state and separation state. When DLAP = 2 mm, the plasma at the center of the keyhole has the strongest spectral intensity, the lowest electron temperature, and the highest electron density, which are 15174, 9546 K, and 1.88 × 1017/cm3, respectively. At this time, the weld pool and keyhole have the maximum arc pressure and Marangoni force, resulting in an increase in the flow velocity of the weld pool and an increase in the area of the weld pool. [ABSTRACT FROM AUTHOR]

NiAl intermetallic-based hardfacing coatings were processed by in situ synthesis from elemental Ni and Al powders mixtures, by Directed Energy Deposition - Plasma Transferred Arc (DED-PTA). The exothermic nature of NiAl synthesis promotes the formation of columnar grains, which do not contribute to mitigate the low toughness of the material at room temperature, limiting its use. Refining the microstructure is a path to overcome this limitation and the approach used took advantage of tungsten carbide nanoparticles (WC-NPs) to limit grain growth during solidification. During preparation of powder mixtures, the adhesion of 1 wt.%WC-NPs to the surface of Ni particles (which act as carriers) helps to reduce the tendency to agglomeration. However, this approach proved to be ineffective for the in situ synthesis of NiAl, since the NPs form a film of molten material on the Ni particle surface as they cross the plasma arc, limiting the interdiffusion of Ni and Al, compromising the synthesis of the aluminide alloy. The present study assessed this challenge by investigating the amount of NP carriers, i.e, the proportion of Ni particles that carry the NPs, that allows both for the synthesis of NiAl, and grain refining due to the WC-NPs. Results show that β-NiAl phase was successfully formed in multi-layer coatings, processed in situ by DED-PTA. Powder mixtures containing 50% and 70% NP carriers promoted a progressive reduction in grain size by the addition of 1 wt.% WC-NPs in the Ni+Al powder mixture, followed by an increase in hardness. [ABSTRACT FROM AUTHOR]

Theoretical investigation for cathodes of different metals, including hafnium (Hf), niobium (Nb), tungsten (W), and molybdenum (Mo) were used. It was noticed that the plasma energy at the cathode (Hf) has a higher value than that at the cathode metal because the energy losses of electrons for (Hf) are less due to inelastic collisions. As for the energy of electrons, their value for the metal (Hf) is also higher than of the other metals, and the reason is that the energy is proportional to the temperature according to the equation: (E = 3/2 KT). It was also noted that the energy of ions for all metals is almost equal at temperature (Tw≅4000K) due to energy losses due to elastic and inelastic collisions, this leads to a state of saturation. There is a large decrease in the voltage barrier accompanied by an increase in the current density, differences occur in the values of the voltage barrier due to the difference in the work function which varies according to the metal. [ABSTRACT FROM AUTHOR]

The mixing process of the cathodic jets is an important connection between the metal surface and the plasma arc column, which helps to understand the diffusion mechanism of the vacuum arc and guides the vacuum switch design. The interaction process of double cathode jets is simulated using a 3D magnetohydrodynamic method. This study analyzes the evolution of plasma parameters as the double cathode jets transition from a separated state to a mixed state. The results indicate that a mixed single-peaked jet ultimately forms at the exit when the double cathode jets are present at the inlet of the cathode surface. The transition from the separated state to the mixed state occurs further away from the cathode surface as the inlet current density of the jets increases from 3 to 5 × 109 A/m2. Additionally, the asymmetry in the current density of the double cathode jets causes the peaks of the mixed single-peak current density and ion temperature to be skewed toward the direction of the lower inlet current density. In cases where the inlet current direction is asymmetric, the peaks shift toward the direction where the inlet current is perpendicular to the cathode surface. Furthermore, the outward expansion acceleration trend of the plasma aligns well with the results from single-jet numerical simulations. [ABSTRACT FROM AUTHOR]

The paper investigates the structure and properties of the surface layers of AA5056 and AA2024 aluminum alloy plates 35 to 40 mm thick after reverse-polarity plasma cutting. It is shown that for alloys with varied parameters of the heat capacity, plasma cutting conditions are the same. At the best plasma cutting parameters, the cut geometry shows the lowest distortion. It is found that the cutting surface distortion occurs in exceeding the optimum heat input of the plasma arc. Conversely, at the reduced heat input, the alloy plate cannot be cut to its full thickness. Most of cutting modes provide the higher surface roughness, while the roughness of the upper edge cut reduces relative to the central and lower areas. [ABSTRACT FROM AUTHOR]

This investigation conducted an experimental study of flow control in a Mach 2.5 cavity combustor using arc plasma energy deposition (APED), implemented both with and without injection. APED was produced by a pulsed arc discharge plasma actuator at frequencies of 5, 10, 15, and 20 kHz. The objective is to elucidate the influence and underlying mechanisms of APED on the flow dynamics by statistically evaluating time-resolved schlieren images and monitoring pressure fluctuations throughout the control process. The findings indicate that APED significantly modifies the energy distribution across unsteady modes and alters the pressure distribution within the flow field. In scenarios without injection, high-frequency discharge triggers oscillations in the shear layer; the impact of precursor shocks and thermal bubbles diminishes the magnitude and fluctuations of both shear layer-induced and internal shocks. Conversely, in the injection scenario, high-frequency discharge, in conjunction with oscillations of the boundary layer and bow shocks, amplifies the oscillation amplitude and frequency of jet vortex shedding. Additionally, APED intensifies the pulsation and penetration depth of the jet, which is essential for enhancing the mixing efficiency of the incoming flow with fuel. The effectiveness of the control is positively correlated with the actuator's discharge frequency, or its average power, within the confines of this study. [ABSTRACT FROM AUTHOR]

A novel plasma reactor is being investigated for green NOx production, crucial for nitrate‐based fertilizer manufacturing. Various parameters, including air flow rates, gas ratios, ozone, and catalyst effects are explored for NO → NO2 conversion. NOx concentrations reach ~0.6 vol%, with a total production of ~9.7 gr/h and energy cost of ~3.0 mJ/mol, notably favorable for atmospheric gliding arc plasma. Selectivity (~75%) towards NO2 is achieved with ozone addition or catalytic treatment, pivotal for nitrate fertilizer and HNO3 production. [ABSTRACT FROM AUTHOR]

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The main goal was to investigate the ability of a non-thermal plasma reactor with gliding arc discharge to remove diesel exhaust particulates (DEPs). A conventional knife-shaped LTP GA (low-temperature plasma gliding arc) reactor was utilized. The following three cases were studied: 140 L/min, 70 L/min, and 14 L/min of air drawn through the reactor, and diesel exhaust fumes were sampled continuously. They were assayed in terms of concentration and number particle size distribution. The higher the residence times, the higher the energy input that may be utilized for DEPs' removal. The reactor performance definitely lowered the concentration of DEPs (250–580 nm) and altered their number size distribution. There was no effect on the number concentration, nor the particle size distribution, of DEPs of 10–250 nm in size. Regarding the effectiveness of DEPs' removal, decreasing the flow rate from 140 L/min to 70 L/min somehow altered the values. Achieving the airflow of 14 L/min led to a substantial improvement (even to a fourfold increase for 300–480 nm particles). Non-thermal plasma reactors with gliding arc discharge may be successfully adapted to the process of DEP treatment. Their performance may be optimized by adjusting the airflow at the inlet of the reactor to guarantee the longest aerosol residence times and the highest removal efficiency. [ABSTRACT FROM AUTHOR]

Fluorinated gases, e.g., CF3I, C3F8, C4F8, C4F7N, and C5F10O, show potential to replace SF6 in power industry due to their high dielectric strength and low global warming potential. However, particle condensation from arc plasmas of these compounds may reduce dielectric performance. We perform a systematic investigation of particle condensation in two-temperature (2T) arc plasmas of various SF6 replacements mixed with CO2, N2, and O2, by the Gibbs free energy minimization and entropy maximization methods. The influences of buffer gases, non-equilibrium degree, and gas pressure on particle condensation are discussed in various cases. The results indicate that O2 is necessary to prevent graphite formation in carbon–fluorine gaseous arcs, and specific mixing ratios of CO2 and N2 are required to avoid graphite and iodine crystals in CF3I arc plasmas. The relationship between condensation temperature and non-equilibrium degree is complex, with peaks and valleys observed for graphite and iodine crystal condensation temperatures. Moreover, different calculation methods (Gibbs free energy minimization versus entropy maximization) show varying sensitivity of condensation temperatures to pressure changes. All the above findings highlight the importance of considering non-equilibrium effects and multiple condensed species in evaluating arc plasma compositions of SF6 replacements. [ABSTRACT FROM AUTHOR]

According to the control mechanism of surface arc discharge plasma actuation on the flow and combustion of flameholder, the applicability of the phenomenological model of surface arc discharge is verified. And, the effects of different actuation positions and actuation intensities on the flow field structure, fuel atomization, ignition delay and flame stability in the flameholder are systematically analyzed. The results show that different actuation positions have a significant impact on the flow field structure, especially when the actuation energy is effectively concentrated and a strong actuation region is formed, which leads to the expansion of the recirculation zone, which in turn promotes fuel atomization, slows down the ignition delay and increases the average flame temperature. At the same time, with the increase of actuation intensity, the length of the recirculation zone, the mixing efficiency and the combustion efficiency increased linearly. [ABSTRACT FROM AUTHOR]

This investigation reports the influence of Ti–C and Ti–W cathode composition on an industrial-scale dc vacuum arc plasma source. Further, we analyze the influence of plasma generation and plasma properties on the resulting cathode surface after the operation and on basic film properties. The results are compared with previous work focused on Ti–Al and Ti–Si compound cathodes. For all Ti–X compound cathodes (X = W, C, Al, and Si), a direct correlation between plasma ion energy/charge and the cohesive energy of the cathode was demonstrated, with a small number of exceptions to a limited set of specific cathode compositions. Hence, the "velocity rule" and effects from different electron temperatures were suggested to be important for gaining a more detailed understanding of plasma properties. A discrepancy was found between the cathode and plasma ion composition, though the difference was reduced in a corresponding comparison between the cathode and the deposited film composition. A significant contribution of a flux of neutrals and/or macroparticles to the final film composition was, therefore, suggested. The effect of the melting point of the cathode phase composition on the intensity of macroparticle generation and the smoothness of the cathode surface operation was also investigated. The presented results contribute to the fundamental understanding of vacuum arc plasma generation and transport and are of importance for further development and applicability of Ti-based coatings from arc deposition. [ABSTRACT FROM AUTHOR]

This paper compares the microstructure and corrosion performance of Alloy 625 weld cladding deposited using Top Wire Feeding GTAW (TWF-GTAW) and Plasma Transferred Arc with Powder (PTA-P). The analysis indicated higher dilution values for TWF-GTAW, with 27.5% for a single layer, whereas in PTA-P, the dilution was 5.1% for a single layer. Both single and double layers presented similar dilution for the different welding conditions because the second deposited layer only partially melted the first layer. The Fe content was higher in TWF-GTAW compared with PTA-P welding. Micrographic characterization showed the formation of micropores in welding using the PTA-P process, with a predominance of Laves phase formation as an interdendritic precipitate. In contrast, TWF-GTAW welding showed the formation of Laves phases and carbide without the presence of micropores. Corrosion resistance was superior for TWF-GTAW weld cladding, with slightly better performance observed for the double layer. In the PTA-P process, interdendritic corrosion was observed, which can be associated with the presence of micropores. [ABSTRACT FROM AUTHOR]

Changes in the interfacial structures of the amorphous silicon (a-Si) anode/organic electrolyte interfaces in lithium-ion batteries were investigated using highly dense a-Si films fabricated by cathodic arc plasma deposition as a model electrode. Raman spectroscopy, transmission electron microscopy (TEM), and X-ray reflectivity revealed that the Si films were grown in an amorphous state with an atomically flat surface. The a-Si films exhibited lithium alloying and de-alloying reactions, with a large irreversible capacity during the first cycle. The irreversible capacity was derived from the formation of a solid electrolyte interphase (SEI) along with an incompletely de-alloyed Li-Si phase, as confirmed by ex situ TEM and X-ray photoelectron spectroscopy observations. The discharge and charge capacities of the Si films gradually decreased in the subsequent cycles, despite the fact that no further SEI formation or cracking of the Si layer occurred. Scanning electron microscopy observations combined with energy-dispersive X-ray spectroscopy revealed the miniaturization of the a-Si film in the surface region to generate domains measuring less than a few hundred nanometers. These results suggest that delamination and miniaturization of the a-Si nanodomains from the electrode surface are partly responsible for degradation of the a-Si anode. [ABSTRACT FROM AUTHOR]

Electro-arc machining (EAM) is a new electrical discharge machining method based on thermal energy. A large amount of thermal energy is released during arc formation to melt and vaporize the workpiece material. Many factors affect arc machining performance, such as electrical parameters (peak current, etc.), non-electrical parameters (flushing pressure, etc.), workpiece and electrode shape, and material parameters. The electrode shape influences the machining performance. Single-factor, single-pulse arc discharge experiments are carried out to evaluate the effect of the electrode's shape. The polarity effect is verified, and the following results are obtained. For the same workpiece conditions, the arc pit diameter is larger for positive polarity than for negative polarity, suggesting that the arc machining performance is also better for positive polarity. The radius of curvature of the crater has a larger influence than the crater diameter. If a larger etching volume is required, the radius of curvature can be increased, but the etching depth is slightly reduced. The positive and negative polarity also affect the arc plasma characteristic. The compression-expansion effect of the plasma is more pronounced when the direct current is large and positive polarity is used. Waveform analysis shows that the processing stability is higher for positive polarity, whereas negative polarity is more likely to result in bridges and short circuits. As the radius of curvature increases, the processing time, processing instability, and the height of the crater wall increase. The height of the crater wall is higher for positive polarity than for negative polarity. [ABSTRACT FROM AUTHOR]

Plasma‐based CO2 conversion has attracted increasing interest. However, to understand the impact of plasma operation on post‐plasma processes, we studied the effect of adding N2, N2/CH4 and N2/CH4/H2O to a CO2 gliding arc plasmatron (GAP) to obtain valuable insights into their impact on exhaust stream composition and temperature, which will serve as feed gas and heat for post‐plasma catalysis (PPC). Adding N2 improves the CO2 conversion from 4 % to 13 %, and CH4 addition further promotes it to 44 %, and even to 61 % at lower gas flow rate (6 L/min), allowing a higher yield of CO and hydrogen for PPC. The addition of H2O, however, reduces the CO2 conversion from 55 % to 22 %, but it also lowers the energy cost, from 5.8 to 3 kJ/L. Regarding the temperature at 4.9 cm post‐plasma, N2 addition increases the temperature, while the CO2/CH4 ratio has no significant effect on temperature. We also calculated the temperature distribution with computational fluid dynamics simulations. The obtained temperature profiles (both experimental and calculated) show a decreasing trend with distance to the exhaust and provide insights in where to position a PPC bed. [ABSTRACT FROM AUTHOR]

The European Green Deal has set a target for Europe to achieve net-zero greenhouse gas emissions by 2050, necessitating a transition to more sustainable energy sources. Hydrogen gas (H 2) has emerged as a promising solution, with methane pyrolysis presenting a viable method for its production. This study explores the optimization of methane plasma pyrolysis for hydrogen and high-quality carbon production. Employing a statistical approach by a design of experiment software, critical process parameters are systematically analyzed to predict their impact within a defined range. Additionally, the paper conducts comprehensive characterization of the solid carbon produced during pyrolysis using imaging, spectroscopic and elemental analysis, and gas sorption analysis methods. The experimental investigation was conducted using a thermal plasma reactor with several settings of influential parameters including methane gas (CH 4) content in the plasma gas, electric current, and arc length. The DC-transferred plasma arc is formed using a variable gas mixture of argon gas (Ar) and CH 4, with a constant flow rate of 5 Nl/min. Thirteen tests were designed, evaluating responses such as power input, process stability, and H 2 yield. The H 2 yield indicates the hydrogen produced from CH 4 , with 100% representing total conversion. While the process exhibited inconstancy, attributed to reactor design constraints, a high H 2 yield of 67%–100% was achieved. The results indicate that a higher CH 4 content in the plasma gas and extended arc lengths disturb the plasma arc, hence reducing the H 2 yield. Increased power input, achieved through higher amperage levels, and a wider reaction zone eased by extending the arc length both led to an improved H 2 yield. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) revealed microstructural differences, with carbon samples from the filter exhibiting finer textures and carbon samples from the reactor larger sizes and dendritic particles. Raman spectroscopy confirmed crystalline graphitic-like structures with low defect concentrations, a finding supported by X-ray diffraction (XRD) analysis. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis confirmed high-purity carbon with slight impurities from initial filter contamination. Brunauer-Emmett-Teller (BET) specific surface area calculations based on gas sorption analysis showed significant variations, with filter-collected samples exhibiting 40–170 m2/g and reactor-collected ones showing 7–30 m2/g. [Display omitted] • This study investigates a unique approach to optimizing the thermal plasma pyrolysis of methane. • A H 2 yield of 67%–100% was achieved utilizing a DC-transferred plasma arc furnace and an Ar and CH 4 mixture plasma gas. • A lower CH 4 content in the plasma gas and an optimized arc length improve the plasma arc and the H 2 yield. • The carbon shows crystalline graphitic-like structures with low defect concentrations. [ABSTRACT FROM AUTHOR]

Excessive alternating current (AC) arcs generated in electric systems will accumulate heat and easily cause fire. This paper studies the thermal characteristics of different numbers of AC arc plasma generated in a short gap of copper-cored wires in the air. The number of AC arcs is controlled in the AC arc experiment and an infrared thermal imager measures the temperature change at the specified position. Based on magnetohydrodynamics (MHD), a two-dimensional axisymmetric AC arc discharge numerical simulation model is established. The volt-ampere characteristic of the AC arc is used to solve the MHD simulation model to obtain the same 'zero current' characteristics as the real AC arc in the experiment. A large amount of heat accumulates in the electrode gaps when the arc generation, and then the heat dissipates in the 'zero current' stage. The continuously generated arc makes the temperature higher. The volume of the space area with a temperature higher than 10,000 K increases with the arc current, but is unrelated to the number of arcs. The volume of the space area with a temperature higher than 524.15 K and the temperature on the electrode are both positively correlated with the number of AC arcs and arc current. The results of this study can provide a reference for the detection standard of AC arc faults and the prevention of electrical fire. [ABSTRACT FROM AUTHOR]

The article describes modern methods for controlling and optimizing the energy mode of melting in electric arc furnaces and units for out-of-furnace steel processing using optical emission spectroscopy systems. These systems enable the determination of melt and slag temperatures, plasma temperatures in the arc combustion area, and slag composition, as well as the analysis of emission intensity from the melt and slag surfaces. The analysis revealed that depending on the range of steel to be smelted and the peculiarities of smelting technology at a particular electric arc steel-making furnace, control systems for smelting monitoring can be developed according to the obtained indicators of one or a combination of the abovementioned parameters. [ABSTRACT FROM AUTHOR]

The lifespan of the guide rail is a bottleneck restricting the operational life of electromagnetic railguns. A well‐designed arc extinguishing device can reduce the arcing erosion caused by residual currents within the guide rail. The CuW alloy is widely used in the high‐pressure arc extinction field due to its excellent electrical and thermal conductivity, high strength, and hardness. Based on the theory of equilibrium state arc plasma, a finite element model of the air arc‐CuW electrode coupling in the arc extinction device was established to study millisecond‐level arc initiation, evolution, extinguishing characteristics, and distribution patterns under extreme and harsh operational conditions with a current input of 110 kA. The highest temperature in the arc column region was found to exceed 50,000 K. The study elucidated the influence of arc extinction device parameters on arc evolution, breakdown time, and breakdown voltage. Consequently, it established that the R70 spherical electrode exhibits optimal arc extinguishing characteristics. The aim of this research is to provide theoretical support for optimizing the arc suppression device. Additionally, experiments on high‐speed and high‐current arc extinction device discharges were conducted to validate the finite element analysis results regarding arc diffusion patterns and electrode erosion. [ABSTRACT FROM AUTHOR]

The electrohydraulic effect induced by underwater arc discharge is an efficient way to generate controllable, high-intensity shock waves. However, the development process of underwater arc discharge involves the complex coupling of plasma arc, gas bubble, and liquid medium, of which the evolution mechanism is not well understood. In this paper, the underwater arc discharge process at a millisecond pulse (>50 ms) was investigated by high-speed shadow imaging and colorimetric temperature measurement, and a simulation model of bubble pulsation was proposed to quantitatively estimate the state variation and energy transfer of the gas bubble. The results indicate that the whole arc discharge process can be categorized into three successive stages: short-period oscillation, long-period oscillation, and quasi-steady state. The vapor inside the bubble can reach a supercritical state (827 K and 140 MPa) at the minimum bubble radius. The simulation shows that the light radiation absorption and the heat conduct loss through metal electrodes are the two dominant factors influencing the pulsation of the bubble, and further analysis indicates that the dynamic evolution of the arc determines the bubble pulsation mode. Our findings demonstrate why and how repetitive electrohydraulic shock waves can be generated by a single long pulse underwater arc discharge, providing a low-cost way of shock wave generator based on an AC/DC high-voltage power source. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia hollow spherical powder (YSZ-HOSP) is a widely utilized ceramic material in thermal barrier coatings (TBCs). Within the category of YSZ-HOSP, yttria-stabilized zirconia spherical thin-walled hollow-shell powder (YSZ-STHS) displays immense potential for producing TBCs with minimal inter-lamellar porosity and cracks. Arc plasma torch equipped with flow-shaping nozzle shows promise for preparing YSZ-STHS. However, there is limited research on the impact of the nozzle geometry on plasma flow field characteristics and the resulting effect on the quality of YSZ-HOSP, particularly in terms of spheroidization ratio, hollow-shell powder ratio, and shell thickness. To achieve controllable preparation of YSZ-STHS in arc plasma spheroidization, this paper proposed a novel model for the formation of YSZ-HOSP under different plasma flow characteristics, including high-speed compressing flow field, intermediate-speed critical flow field, and low-speed expanding flow field. These different plasma flow characteristics were achieved by changing the nozzle diameter and investigated by both numerical simulation and experiments in terms of plasma flow characteristics, electro-thermal characteristics, and the quality of the YSZ-HOSP. Results reveal that YSZ-HOSP prepared with high-speed compressing flow field resulted in a low hollow-shell powder ratio, while low-speed expanding flow field led to an over-thick shell. Conversely, the intermediate-speed critical flow field demonstrates relatively high thermal efficiency and enthalpy, along with moderate jet temperature and velocity, resulting in YSZ-STHS with a spheroidization ratio of 96.6 %, a hollow-shell powder ratio of 92.5 %, and a mean shell thickness of 3.49 μm. Therefore, it is evident that manipulating plasma flow characteristics allows for the controlled preparation of YSZ-STHS. [Display omitted] [ABSTRACT FROM AUTHOR]

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The effective welding of a 6 mm thick TA2 pure titanium medium-thickness plate was achieved by laser–arc hybrid welding (LAHW) with helium–argon mixed shielding gas. Conducted research on the influence of helium–argon mixed shielding gas on plasma and arc characteristics during welding, and its further impact on the microstructure, internal porosity defects, tensile properties, and corrosion resistance of welded joints was explored. The study demonstrated that under the shielding gas with 75% helium, the arc width narrowed significantly from 6.96 mm to 2.61 mm, achieving a 63% reduction, which enhanced the concentration of arc heat flux density. Achieved a well-formed weld with no surface spatter and significantly reduced the internal porosity rate from 3.02% to 0.47%, which is an 84% decrease. Tensile fractures are located in the base material, all exhibiting plastic failure. The corrosion resistance of the welded joint initially increased and then decreased with the increase of helium content in the shielding gas, peaking at 75% helium content. [ABSTRACT FROM AUTHOR]

Plasma seed pretreatment is an important means to rapidly improve seed quality. The studies on plasma-generating devices suitable for continuous seed pretreatment at atmospheric pressure have been relatively limited. Gliding arc discharge can generate atmospheric pressure plasma at room temperature, which provides a new way to use plasma to treat seeds at ambient temperature and pressure. By analyzing the influence of structural characteristics, such as gliding arc electrode shape, discharge distance, and electrode opening angle on plasma distribution, a plasma seed treatment method based on negative pressure guidance was proposed, and the electrode structure was optimized. The results show that the reasonable matching of electrode structure parameters can improve the gliding arc guiding ability of the discharge electrode. Comparing the three electrode shapes, it was found that the triangular electrode had the best gliding arc guiding ability, and it had the potential to further increase the plasma size with the increase in the electrode size. The discharge distance and electrode opening angle had a significant impact on the gliding arc guiding ability of the discharge electrode. When the discharge distance was 15 mm and the electrode opening angle was 76°, the structure parameters of the plasma seed treatment electrode were matched with each other, and the best processing capacity was achieved. After 10 s of gliding arc plasma treatment with the optimized triangular electrode structure, the seed germination rate and germination index of Leymus chinensis ((Trin.) Tzvel) increased by 33.3% and 13.8%. This study provides a theoretical basis for the design and optimization of gliding arc electrode structures and serves as a reference for the research and development of plasma generators for continuous seed treatment at atmospheric pressure. [ABSTRACT FROM AUTHOR]

The abiotic synthesis of peptides, widely regarded as one of the key chemical reactions on the prebiotic Earth, is thermodynamically constrained in solution. Herein, a simulation of the lightning phenomenon on the sea surface using bubble bursting and arc plasma under ambient conditions enables dipeptide formation of six amino acids with conversion ratios ranging from 2.6 % to 25.5 %. Additionally, we observed the formation of biologically active tripeptides and investigated the stereoselectivity of the dipeptide formation reaction. By utilizing a mixture of 20 amino acids in the reaction, 102 possible dipeptides were generated. These results establish experimental constructions to mimic achievable prebiotic conditions and provide a credible pathway for endogenous biopolymer synthesis on prebiotic Earth. [ABSTRACT FROM AUTHOR]

At present, research on arc magnetic confinement predominantly focuses on the influence of external magnetic fields (EMF) on traditional free-welding arc. However, studies on magnetic re-confinement of plasma cut arc constrained by mechanical structures remain limited. This study establishes a three-dimensional (3D) electromagnetic model for the confinement device and designs a 3D plasma cutting arc model based on magneto-hydrodynamics. Through a combined simulation approach using Maxwell and ANSYS, we extensively investigated the distribution of the longitudinal magnetic field (LMF) and emphasized its impact on the characteristics of the plasma cutting arc. Within the range of 0 ~ 200 mT, simulations were conducted to analyze the temperature, velocity field, flow field, and arc pressure distribution of the plasma cutting arc under varying LMF intensity. The results indicate that the application of LMF can significantly enhance the current density, temperature, and straightness of the plasma cutting arc, thereby improving the cutting performance. These findings provide valuable theoretical insight for optimizing magnetic re-confinement plasma arc cutting device and process in practical engineering applications. [ABSTRACT FROM AUTHOR]

In gas–metal arc welding (GMAW), the welding quality is influenced by various factors, including the welding conditions and external environment. Achieving a high welding quality requires careful observation and control. Welding monitoring is crucial for validating a planned welding process and assessing its quality. This study introduces a vision system for the online acquisition of clear molten pool images. It uses a small camera equipped with a complementary metal-oxide-semiconductor sensor during GMAW, as well as a method for constructing this system. The proposed vision system does not require triggering using devices such as field-programmable gate arrays, facilitating lower costs and online quality monitoring under various welding conditions during mild-steel GMAW. Accurate measurement of radiation from the weld is essential for clear observation of the molten pool during welding, emphasizing the importance of selecting an optical system with appropriate lenses and filters. In addition, appropriate digital camera parameters must be set for monitoring. High-quality images were successfully captured using the proposed method, and the image quality was evaluated using the blind/referenceless image spatial quality evaluator algorithm. [ABSTRACT FROM AUTHOR]

Precisely assessing plasma parameters holds paramount importance in investigating the arc extinguishing mechanism of semi-sealed splitter plate DC circuit breakers, refining the configuration of splitter plates, and optimizing the overall structural design of circuit breakers. Based on the principle of the Langmuir probe, a double probe diagnostic method is proposed to investigate the air arc plasma in the opening process of a DC circuit breaker. The diagnostic circuit of the probes is designed, and three sets of double probes are arranged to trace the evolution of the plasma density during the opening process. The research reveals that the plasma center density, measured by the diagnostic system during the opening process of the DC circuit breaker, is about 1022 m−3–1023 m−3. This density is compared with the diagnostic results obtained by other methods, confirming the accuracy of the Langmuir double probe for plasma measurements in the DC circuit breaker. The study also revealed an exponential decay behavior of electron density along the radial direction of the arc. A mathematical model was employed to describe this phenomenon, establishing a relationship between the distribution of electron density and arc current. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) production is of global concern for today's food supply security and as future energy vector. Plasma technology can add to supply‐chain resilience of fertilizer production and improve the environmental profile using renewable energy; allowing distributed NH3 production. With the objective to provide process intensification of small‐capacity reactors for local supply, a novel micropyramid‐disk plasma reactor operated in micro‐arc mode was developed. NH3 was synthesized from N2, nitrogen, and H2, hydrogen over Ru/MCM‐41 catalyst at atmospheric pressure. The microplasma brings plasma and catalyst surface close together and intensifies the electric field. The arc plasma elevates temperature, 'nonthermal', releasing high‐energy free electrons, known to be effective in converting low‐reactive molecules. The study demonstrates that microplasma, with reduced electrode‐to‐electrode dimensions and a microstructured reaction environment, enhances the performance of the NH3 synthesis and opens novel process windows. This is detailed on the impact of feed ratio (N2/H2), applied voltage, frequency, electrode gap, and the flow distribution by which the gas is fed in. Optical emission spectroscopy (OES) was used to identify vibrationally and other excited species generated by the microplasma and confirms the catalyst is in symbiosis with the radicals. [ABSTRACT FROM AUTHOR]

CuO nanoparticles obtained in a low-pressure arc discharge plasma followed by annealing in an oxygen atmosphere at 500°C were studied by X-ray diffraction and transmission electron microscopy. The formation of irregularly shaped nanoparticles in the size range of 5–30 nm was found. The Rietveld refinement confirmed the formation of a monoclinic CuO phase with an average crystallite size of ~21 nm. The temperature dependences of the magnetization and permittivity of CuO nanoparticles have been studied. They show antiferromagnetic behavior with a Neel temperature of 230 K and frequency-dependent dispersion behavior in the temperature range of 100–200 K at an external magnetic field induction of 0–1.3 T. The dielectric relaxation mechanism is analyzed and found to follow the Arrhenius behavior. It is shown that hopping conductivity with a variable hop length more accurately describes charge transport in CuO nanoparticles. A magnetodielectric response of about 2.5 was observed at a frequency of 12 kHz at a temperature of 150 K in a magnetic field of 1.3 T. [ABSTRACT FROM AUTHOR]

The effects of cutting speed and current on plasma cut quality were investigated. Regression modeling was used to establish relationship between process parameters and responses. Analysis of variance was performed to determine the significance of independent variables influencing the kerf geometry. The analysis showed that the proposed regression model fits the experimental data fairly well and the selected variables influence kerf length difference and top kerf width substantially. However, while the bottom kerf width was significantly influenced by cutting speed, it was not affected by the current. The analysis results were compared with the experimental data and were found to be in good agreement. The images captured with high-speed camera using appropriate band-pass filter revealed that the plasma flows under the workpiece were affected by the process parameters. The tail length and the direction angle of the plasma flow dictated the shape of the kerf geometry. [ABSTRACT FROM AUTHOR]