DC Arc Discharge Research Articles

Energy regulation of impulse current generator modulated DC arc discharge

AbstractThis paper proposes a method of impulse current generator modulated DC arc by combining the advantages of pulse and the RF to solve the low electron energy problem of direct current arc. Through experimental analyzing the electrical, spectral, and optical characteristics of the arc, the effect of impulse current generator (ICG) on improving electron energy is discussed. The results show that the ICG consumes more energy to enhance the strength of arc discharge, and therefore electron energy is increased in a microsecond scale. In addition, it is found that the electron energy of the arc discharge can be adjusted by varying inductance, capacitance, and discharge tube: increasing the inductance or capacitance can increase the electron energy firstly and then decrease it. In adjusting the three adjustable components, adjusting the inductor is the most effective method, followed by adjusting the capacitor, and adjusting the repetition frequency has the least effect. The reason is discussed, and it is believed that the results are related to leakage inductance and distributed capacitance.

Synthesis of NbC@C(Nx) nanoparticles using DC arc discharge plasma for highly efficient oxygen reduction reaction

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(Nx) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N1.36) NPs showed an onset potential (Eonset) of 0.89 V (vs. RHE) and a half-wave potential (E1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (Eonset = 0.90 V, E1/2 = 0.80 V), and its diffusion-limited current density (JL) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (Te) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR.

Experimental study on the full cycle evolution of high-intensity atmospheric dc arc discharge from breakdown to extinguishment.

In this study, the spatiotemporal evolution of full cycle of high-intensity dc argon arc discharge at atmospheric pressure is investigated by using a transferred arc device, which is easy to be directly observed in the experiment. Combining the voltage and current waveforms with high-speed images, the full cycle evolution process of high-intensity atmospheric dc arc can be divided into five different stages: breakdown pulse stage, cathode heating stage, current climbing stage, stable arc discharge stage, and finally arc extinguishing stage. The characteristics of each different stage are analyzed in detail through the electrical properties, high-speed pictures, and spectroscopic measurements. The results show that the strong luminescence region develops from the vicinity of cathode and anode to the middle in the breakdown pulse stage, which is explained from the spatiotemporal evolution of distributions of excited argon atom and ions. The development velocity of emission intensity of argon ions is mainly determined by the dominant stepwise ionization process. Then the cathode heating stage appears with many bright and nonuniformly distributed light spots on the cathode surface, and the electron emission mechanism of cathode gradually changes to the thermionic emission as the surface temperature rises. With the increase of arc current, the discharge channel significantly expands, then becomes stable due to the increment of the Lorentz force. The characteristics of arc extinguishing stage are clarified in terms of the decay of charged particles density.

Experimental study of CO2 dissociation in an expanding dc arc discharge at atmospheric pressure with multiple pin-to-pin electrodes

In the following study, we examine the performance of a new design of the classic gliding arc discharge (GAD) with diverging electrodes between dielectric walls at atmospheric pressure. In the present design, a tungsten pin-to-pin electrode pair ladder replaces the standard curved diverging electrodes. A major problem with the classic GAD design is the surface erosion of the electrodes, which leads to bad repeatability and issues with long-term usage. The new construction provides controlled electrode wear at well-defined points of arc attachment. This ensures stable operation while retaining the arc expansion effect. This new configuration of the discharge is being developed for gas treatment. In the current work, the device was applied for CO2 dissociation. The most significant quantities for this application of the GAD, the CO2 conversion rate and energy efficiency, are measured at different gas flow rates (2–12 Ln/min) and arc currents (50–210 mA). The results are analyzed and compared with previous measurements using the classic GAD at the same conditions.

(Invited) Atmospheric-Pressure Reactive Thermal Plasma Jet Technology for Decarbonization of Semiconductor Manufacturing

Semiconductor market continues to grow and is expected to hit a trillion dollar in 2030. On the other hand, CO2 emission from semiconductor industry has been anticipated to become one of the serious issues regarding carbon neutral commitments. Organic solvent, which is used for cleaning and wet etching processes, is one of the sources to emit CO2 during device manufacturing. They are recycled and reused, nevertheless, huge amount is disposed. Replacing the wet etching by dry process is a quite effective approach, however, the etching rates by conventional plasma etchings are quite low compared to that of organic solutions (~30 µm/s). In this work, we propose an introduction of atmospheric-pressure reactive thermal plasma jet (R-TPJ) to perform rapid heating and etching reaction simultaneously, which markedly enhances the etching rate of photoresist(PR).In the experiment, n-type Si(100) wafer was treated by RCA cleaning and HF, HMDS solutions and PR (TOKYO OHKA KOGYO CO., LTD. TSMR iP-3300 17cP) were spin coated at 4400 rpm and baked at 130 °C for 2 min to from ~ 900-nm-thick PR layer. The R-TPJ was generated by DC arc discharge under atmospheric pressure with a supply current (I) of 20 A between a W cathode and a metal anode separated by electrode spacing (ES) of 2.0 mm. Ar flow rate (f Ar) was varied from 1.0 to 2.0 L/min, and O2 flow rate (f O2) was varied from 0.3 to 3.0 L/min. The samples were linearly moved by a motion stage in front of the R-TPJ with a scanning speed (v) ranging from 20 to 260 mm/s. The working distance (d) was varied from 0.5 to 3.0 mm. The nozzle diameter is 1 mm.An emission line from atomic oxygen radicals was observed at 777nm and its intensity increased with increasing O2 flow rate, accordingly, the etching rate of PR increased in a similar manner. An etching rate of 6.3 µm/s was obtained with the f Ar of 1.0 L/min, f O2 of 1.0 L/min, and d of 1.0 mm. Moreover, by decreasing the working distance d, etching rate increased with an exponential manner, and an etching rate as high as 61.5 µm/s was obtained when d was set at 0.5 mm, as shown in the figure. It is assumed that millisecond heating of PR surface and simultaneous supply of reactive species have realized an ultra-fast etching of PR. The activation energy for PR etching has been reported to be 0.53 eV [1,2], and according to the experimental fitting on Arrhenius plot, the temperature corresponding to the etching rate of 61.5 µm/s is estimated to be ~820 K. In addition, we conducted a heat diffusion simulation considering PR/Si layer structure annealed by R-TPJ. It was suggested that the annealing temperature reached as high as ~800K with the annealing duration of 4ms. These results suggest that ultra-fast etching of PR by R-TPJ offers a new etching concept in millisecond time regime.In conclusion, R-TPJ provides millisecond thermal etching and is a candidate to replace conventional wet etching and will contribute to the decarbonization of semiconductor device manufacturing.[1] K. Yamakawa, M. Hori, T. Goto, S, Den, T. Katagiri, and H. Kano, J. Appl. Phys. 98, 043311 (2005).[2] A. Granier, D. Chereau, K. Henda, R. Safari, and P. Leprince, J. Appl. Phys. 75, 104 (1994). Figure 1

Synthesis of Mo2C-based material in DC arc discharge plasma under ambient air conditions

Molybdenum carbide is a well-known material, which properties makes it good candidate for replacing platinum in hydrogen production by electrolysis. Mo2C phase shows the best characteristics among other molybdenum carbide phases in HER. In this paper Mo2C-based powder material has been synthesized by non-vacuum DC arc discharge method. The main advantage of the method is the synthesis under ambient air conditions, which leads to low cost and more effectiveness of the process. We carried out several series of experiments to determine the optimal synthesis parameters that ensure the dominance of the Mo2C phase in the synthesis product. Carbon nanofibers (CNFs) obtained via catalytic pyrolysis of ethylene on Ni–Cu alloy were used as a carbon source. CNFs were characterized by SEM and low-temperature adsorption/desorption of N2. According to XRD analysis, the optimal ratio of the initial components C:Mo is 1:16 wt, arc current is 200 A, and plasma exposure time is 30 s. In this paper, for the first time the oxidation behavior of the Mo2C-based material, obtained in DC arc discharge plasma under ambient air conditions, was investigated by TG/DTA. The noble metal free HER electrocatalyst with the synthesized material as precursor was prepared for investigation of electrocatalytic activity.

Magnetorheological properties of Fe–Co nanoparticles with high saturation magnetization and low coercivity

Fe–Co alloys exhibit an excellent saturation magnetization, which makes them become a potential candidate for the high property magnetic particles in magnetorheological fluids (MRFs). How to decrease their coercivity and residual magnetization without sacrificing the saturation magnetization is a crucial problem to be solved. In this study, Fe–Co nanoparticles were prepared by DC arc discharge and further disposed through low temperature annealing in Ar atmosphere. The successful synthesis of Fe–Co nanoparticles was proved by x-ray diffraction and EDS. The vibrating sample magnetometer results revealed that the prepared Fe–Co nanoparticles had a saturation magnetization of 208 emu g−1, while the coercivity and remanent magnetization were 58 Oe and 5.8 emu g−1, respectively. The MR properties of Fe–Co nanoparticles based MRFs (FeCoNP-MRFs) with 10% particles by volume fraction were systematically investigated. The FeCoNP-MRFs showed up to 4.61 kPa dynamic shear stress at 436 kA m−1 magnetic field and an excellent reversibility. The MR properties of FeCoNP-MRFs were fitted well by Bingham and power law model, and described by Seo-Seo and Casson fluid model. Meanwhile, the sedimentation ratio of FeCoNP-MRFs was still 87.3% after 72 h, indicating an excellent sedimentation stability.

Синтез порошка карбида гафния в атмосферной дуговой плазме

The paper presents a method, implemented for the first time, for the thermal synthesis of hafnium carbide powder using a DC arc discharge initiated in the open-air atmosphere. Based on the results of the series of experiments, the dependences of the current strength of the power source and the time of thermal treatment on the phase composition of the resulting powder product were established. Required parameters have been determined to ensure the synthesis of a powder containing ~ 98 wt. % of the cubic phase of hafnium carbide: heat treatment of the initial mixture containing the stoichiometric ratio of hafnium to carbon for 60 s at a current of 220 A. The size, shape, and substructure of particles of the synthesized carbide are characterized. The differential thermal analysis carried out in an oxidizing medium showed that the obtained hafnium carbide powder is oxidized most intensively at a temperature of ~700°C.

Numerical Evaluation of Melting and Breaking Characteristics of Return Conductor Strands of 200kV HVDC Overhead Transmission Line Struck by Lightning

In March 2021, the Shin-Shinano Substation of TEPCO Power Grid, Inc. was connected to the Hida Convertor Station of Chubu Electric Power Grid Co., Inc. by HVDC transmission system with an interconnection capacity of 900MW in order to increase the interconnection capacity between the eastern and the western areas in Japan. The 200kV HVDC overhead transmission lines have a pair of energized conductors and a return conductor. It has been investigated that TACSR (410mm2 [AC410], 610mm2 [AC610], 810mm2 [AC810]) would be used as the return conductor. However, as the return conductor plays the role of a ground wire, the melting and breaking of TACSR strands due to lightning strike was concerned. Therefore, in this paper, numerical evaluations of melting and breaking characteristics of the return conductor strands were carried out supposing the return conductor was struck by DC arc discharge simulating lightning whose maximum current was 400kA. As a result, the number of breaking strands of AC610 was more than that of AC410 and AC810 because the diameter of strands of AC610 was smaller than that of AC410 and AC810. The remaining rate of cross-section area of strands of AC410 decreased more than AC610 and AC810 as DC arc current increased.

PECULIARITIES OF INTERACTION OF Cu-W COMPOSITE MATERIALS WITH THERMAL ARC DISCHARGE PLASMA

This work is a part of acomplex investigation of the interaction of Cu-W composite materials with thermal electric arc discharge plasma. The plasma of 3.5 A DC arc discharge between novel Cu-W composite materials, fabricated by shock pressing technology at the temperature of 750°C, was studied at this stage. Spectra of such plasma emission were registered and treated to determine the radial distributions of plasma temperature in three different cross-sections of the plasma channel, namely in near-cathode, near-anode and middle cross-sections.

Ash and Slag Waste Processing in Self-Shielded Atmospheric DC Arc Discharge Plasma.

In this paper, we report the experimental results obtained in slag waste processing by direct current arc discharge initiated in ambient air. The method does not employ vacuum and gas equipment, therefore increasing the energy efficiency of processing. Plasma processing of coal slag was performed at different arc exposure times: 5, 10, 15, 20, and 25 s. The obtained materials contained a significant amount of graphite, which was removed through combustion. The micropowder based on silicon carbide and aluminum nitride was obtained and then sintered by spark plasma. The bulk ceramic samples based on silicon carbide with the hardness of ~10.4 GPa were finally fabricated.

Ignition kernel development in a reactive flow for nanosecond-pulsed high-frequency and DC arc discharges

The development of energy efficient combustion systems is a critical technical objective in the engine and power generation industries. This pursuit often prompts using conditions at the limits of capability, dictating the need to expand the envelope of robust and reliable operation. Nanosecond-pulsed high-frequency discharges (NPHFD) have proven to be effective in extending ignition limits in both quiescent and flowing environments. However, limited research has been conducted comparing the kernel growth behavior in a flowing environment of a train of discrete nanosecond discharges to that of a conventional DC arc discharge. Therefore, this work focused on comparing these two types of discharges by matching the total energy deposited, total deposition time, and average power. For each system, three average power conditions (100, 180, and 400 W) were tested, each including five total discharge times (0.05, 0.15, 0.25, 0.50, and 1.00 ms) at two inter-electrode gap distances of 1 and 2 mm. The 1 mm gap distance results showed that the NPHFD system produced larger ignition kernel areas than the conventional system at the highest average power (therefore, highest pulsation frequency) setting. At all other average power conditions, the NPHFD system produced equivalent or smaller ignition kernels than the conventional system due to a lack of pulse-to-pulse coupling. At the 2 mm inter-electrode gap distance, the NPHFD ignition system produced larger kernels at all conditions except at the lowest average power and discharge duration setting. At the highest average power and longest discharge duration setting, the NPHFD kernel was nearly twice as large in area as the kernel produced by the conventional system at 5 ms after discharge. The larger kernel area created by the NPHFD system at the larger gap distance, higher average power, and longer total discharge duration conditions could be explained by the high level of pulse-to-pulse coupling and discharge-induced jetting behavior. The jetting behavior was a function of electrode polarity and mainly extended the reactive region of the kernel in the spanwise direction.

Synthesis of Submicron Boron Carbide by the Non-Vacuum Method with Indirect Supply of the Thermal Energy of a DC Arc Discharge

The results of experimental studies demonstrating the possibility of obtaining boron-carbide powder by treating a mixture of carbon and amorphous boron containing a small amount of boron oxide with DC arc discharge plasma are presented. A feature of the applied nonvacuum electric-arc method for the synthesis of boron carbide is its implementation in an open air environment due to achievement of the effect of screening the reaction zone with gaseous oxide and carbon dioxide. In this case, the initial reagents are heated to the required temperatures by a DC arc discharge plasma burning in the immediate vicinity of the initial-material mixture in the cavity of the graphite crucible. The resulting material contains particles of boron carbide with a size in the submicron range, which are characterized by the “shell–core” type structure. The scheme of the discharge circuit of a laboratory reactor with horizontal arrangement of electrodes and an indirect supply of thermal energy to the initial reagents described in the paper makes it possible to significantly increase the content of the boron-carbide phase and reduce the content of the graphite impurity phase.

Synthesis of transition metal carbides and high-entropy carbide TiZrNbHfTaC5 in self-shielding DC arc discharge plasma

The paper shows the feasibility of synthesizing micro- and nano-sized particles of binary metal carbides (Me–C) and high-entropy carbide (HEC) TiZrNbHfTaC5 by vacuum-free electric arc method. The method is based on the effect of self-shielding of the reaction volume from atmospheric oxygen by carbon monoxide CO, which is generated during arcing in air. The synthesis results in a solid solution with a NaCl-type carbide with a cubic lattice, which simultaneously contains atoms of titanium, zirconium, niobium, hafnium, tantalum, and carbon. The lattice parameter of the HEC TiZrNbHfTaC5 phase is ∼4.532 Å that is in line with the known data on this compound. The synthesis product contains micro-sized particle agglomerates of transition metal carbides. The synthesis products also contain nano-sized particles with a shell-core structure, in which the core can consist of metal carbide (TiC, ZrC, NbC, HfC, TaC) or HEC TiZrNbHfTaC5, and the shell is a graphite phase.

Using equilibrium thermodynamics to study thermochemical processes in arc discharges used in atomic emission spectral analysis (review)

Until the beginning of the 21st century, the arc discharge was the main source of excitation of the atomic spectra of elements during routine atomic emission spectral analysis. The wide application of this spectral source at the same time aroused great interest of analysts in the study of complex thermochemical processes occurring at its electrodes and in the discharge plasma. This was due to the need to improve the metrological and informational characteristics of the analysis. Equilibrium thermodynamics has often been used to carry out such studies. It is shown that three levels of the thermodynamic approach can be distinguished here, differing in the complexity of the applied apparatus of thermodynamics and the information content of the results obtained. Numerous examples of the application of these levels of approach to the study of thermochemical processes occurring in the electrode or in the discharge plasma are given. The main advantages and disadvantages of the approaches used, which provide only qualitative information about the ongoing processes, are noted. The main disadvantage is the impossibility of predicting the composition of the arc plasma from the initial composition of the condensed sample. The most informative is the generalized thermodynamic model of thermochemical processes in a DC arc discharge from the sample surface and from the electrode crater. The model is based on the division of a non-stationary non-equilibrium system of an arc discharge into successive quasi-stationary subsystems. They correspond to the stage of sample evaporation and thermochemical transformation of its components in the discharge plasma. According to the model, the total equilibrium composition of the evaporated sample is initially calculated. This determines the initial composition of the arc plasma. Then, the total equilibrium composition of the arc plasma is calculated and the transition to the intensities of the spectral lines of the analytes is performed. The correctness of the generalized model, which gives semi-quantitative results, is confirmed by comparison with experimental data.

Investigation on characteristics of millisecond solid-phase crystallized silicon films annealed by atmospheric pressure DC arc discharge micro-thermal-plasma-jet and their application to bottom-gate thin film transistors fabrication

Millisecond solid phase crystallization (SPC) of silicon film induced by micro-thermal-plasma-jet is a potential method for small grain bottom-gate thin-film transistors (TFTs). The characteristics of millisecond SPC films under the conditions of scanning speed (v) from 500 to 900 mm s−1 were investigated. The films show good crystalline quality when formed at a slow v. The crystallinity estimated by micro-Raman spectroscopy is 61% when v was 500 mm s−1. Hall effect measurement results indicate that under v at 500 mm s−1, the resistivity is 1.36 × 10−3 Ωcm, the carrier concentration is 3.41 × 1020 cm−3, and the carrier mobility is 12.2 cm2 Vs−1. Millisecond SPC films surface reduce larger than 76% roughness compared to that of the melted film surface. Bottom-gate TFTs fabricated with millisecond SPC film, which annealed under conditions close to melted condition, show high field effect mobility of 28 cm2 Vs−1 and good uniformity.

Magnetic field stabilization of low current DC arc discharge in cross flow in argon gas at atmospheric pressure—a numerical modelling study

In this work we study the effect of an external magnetic field and gas flow on the properties of a low current DC (gliding) arc discharge in argon at atmospheric pressure. We consider a cross flow configuration, in which argon gas flows perpendicularly to the arc current, while the external magnetic field is perpendicular to both the arc current and the gas flow. The study is based on a 2D numerical fluid plasma model of the discharge, coupled with a gas flow model based on the Navier–Stokes equations and a gas thermal balance equation. In the examined configuration, a stabilized arc is achieved by having the E × B drift acting in opposite direction to the gas flow, i.e. the Lorentz force pushing the arc against the gas flow. The numerical model was implemented into a finite element simulation, using the Comsol Multiphysics® (version 5.3) package. The results proved that a magnetically stabilized arc can be sustained and that the examined configuration can be used for effective gas treatment. The analysis of the simulation data helped to answer multiple questions, related to arc stability, the energy density distribution in the arc, and the macroscopic properties of the system as a whole. The results show a significant influence of the walls on the arc stabilization, while in the case of walls positioned very far from the arc, i.e. unbounded channel, the arc becomes a source of a fluid instability, causing vortex shedding. In general, this study provides insight on the interaction between the gas flow and the arc in a strong magnetic field. The model presented here has the potential to further the understanding of magnetically stabilized discharges and to become a basis for developing similar studies of more complex gases.

Advanced Arc Plasma Synthesis of Biomorphic Silicon Carbide Using Charcoal and Silicon Dioxide in Air

This work presents the results revealing the possibility of obtaining a cubic phase of silicon carbide with features of a biomorphic structure. Renewable plant raw materials were used as a source of carbon, in particular, pyrolyzed sawdust, which is a waste of a timber enterprise. Silicon dioxide powder was used as a source of silicon. The synthesis was realized using DC arc discharge plasma initiated in an open air. In this case, the oxidation of the synthesis products was prevented due to the effect of the reaction volume self-shielding from atmospheric oxygen. It was possible due to the generation of protective gaseous medium predominantly consisting of carbon dioxide and monoxide. The dependences of the product phase composition on the supplied energy and composition of initial components were established. The synthesis product was characterized by a significant excess of carbon, which was a caused by the erosion of the electrodes. After removal of chemically unbound carbon from synthesis product by annealing in an atmospheric furnace at 850 °C, obtained powder was sintered by the spark plasma sintering method. In the result, a bulk ceramic sample was obtained in which the only one crystalline phase of silicon carbide with a lattice parameter of 4.359 Å was identified.

Melting and Breaking Characteristics of Strands of High-strength and High-corrosion-resistant OPGW due to DC Arc Discharge Simulating High-energy Lightning Strike

Melting and Breaking Characteristics of Strands of High-strength and High-corrosion-resistant OPGW due to DC Arc Discharge Simulating High-energy Lightning Strike

Study of Welded Joint Metal Structure under Pulsed Impact on Arc Discharge

The article presents the results of an experimental study of the effect of an additional pulse-quasi-harmonic voltage with a frequency of 40 kHz on the structure of welded joints, the technological properties of a DC arc discharge in manual arc welding with covered electrodes. Obtaining a fine-grained structure of a welded joint is one of the conditions for increasing its technological and strength properties, and the operational reliability of the manufactured product as a whole.