Electric Arc Research Articles

Influence of Submerged Arc Welding Current Intensity on the Mechanical Properties and Microstructure of Pressure Vessel P355N Steel.

This article presents a study on the influence of the intensity of the welding current on the properties of the mechanical strain strength of welded joints made by using submerged arc welding technology. The influence of the welding current on the microstructure of the welded joints was also observed in different regions of the cross-section of the welding seam. Also subject to observation was the mode of influence of the welding current on the geometry and dimensions of the welding seams. The welded samples were obtained using five different welding regimes whose main variable was the intensity of the welding current, which had values between 300 A and 700 A. The criterion used as a reference for comparing the effects produced by the studied welding regimes was a standard welding regime that is used in the industry for welding railway tank wagons, with a welding current intensity of 480 A. The base material used in the experiments was a fine-grained carbon steel specially intended for the manufacture of pressure vessels identified as P355 N; the semi-finished product from which the samples were made consisted of 6 mm thick laminated sheets used in the manufacture of the covers of the vessels that make up the railway tank wagon. The aim of this study was to highlight the differences that may appear through varying the current welding parameter and identify welding regimes that can provide welded joints with superior mechanical properties compared to what is currently employed in the industry. This study focused on the most widespread technology of welding pressure vessels: the submerged electric arc welding method.

Model of non-equilibrium near-cathode plasma layers for simulation of ignition of high-pressure arcs on cold refractory cathodes

The introduction of secondary ion-electron emission into an approximate model of non-equilibrium plasma layers on hot (thermionic) cathodes of high-pressure arc discharges allows extending the model to low cathode surface temperatures. Analysis of evaluation results shows that the extended model describes glow-like discharges on cold cathodes and thermionic arc discharges on hot cathodes, as it should. In the course of glow-to-arc transitions on cold cathodes, a transient regime occurs where a hot arc spot has just formed and a significant fraction of the current still flows to the cold surface outside the spot, so that the near-cathode voltage continues to be high. The power input in the near-cathode layer is very high in this regime, and so is the electron temperature in the near-cathode region. The mean free path for collisions between the atoms and the ions in these conditions exceeds the thickness of the layer where the ion current to the cathode is generated. A new method for evaluation of the ion current under such conditions is implemented. The developed model is applicable for cathode surface temperatures below the boiling point of the cathode material and may be used for multidimensional simulations of ignition of high-current arcs on refractory cathodes.

Synthesis of chromium carbide powder by vacuum-free electric arc plasma method

Chromium carbide powders were synthesized by vacuum-free electric arc method using pure chromium and carbon powder as starting components. The powders obtained in the experimental series were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), laser diffraction and differential thermal analysis. In the experiments, electrical parameters were recorded, and the thermal field generated in the reaction zone was measured using an infrared camera and tungsten‑rhenium thermocouples. The study results show the feasibility of plasma arc discharge synthesis of chromium carbide compounds Cr3C2 and Cr7C3 within 60 s at current intensity of 200 A. SEM analysis of the resulting powder shows that it consists of acute-angled particles of ∼9 to ∼50 μm in size. An updated design of the discharge circuit employed in the study significantly increases the purity of the final product. Vacuum-free electric arc synthesis of chromium carbide has been studied for the first time.

New Certified Reference Material of Tungsten Concentrate for Developing Multielement Analysis Techniques

A new multielement certified reference material of tungsten concentrate (GSO 11541–2020) – wolframitehubnerite concentrate (hard-alloyed), KVG(T) was developed. Its metrological characteristics were established via results of interlaboratory experiment. The analytical results were obtained at the testing laboratories of 13 scientific and manufacturing organizations of Russia, Belarus, Kazakhstan, and Uzbekistan using single-element chemical analysis methods (gravimetric, spectrophotometry, atomic absorption spectrometry, etc.), as well as modern multielement methods (atomic emission spectrometry with arc discharge or inductively coupled plasma, inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry). The mass fraction values for ten elements certified; for eleven elements recommended; and for 39 elements, as well as hygroscopic and crystallization water, are given as information data. This CRM is intended for certification and validation of single and multielement methods, as well as quality assurance in analysis of the ores and products of their processing in mining, metallurgical, and chemical industries and in scientific research. The information potential of GSO 11541–2020 is higher than that of imported reference materials.

Alfalfa biomass as a green source for the synthesis of N,S-CDs via microwave treatment. Application as a nano sensor for nifuroxazide in formulations and gastric juice

BackgroundResearchers have investigated different techniques for synthesis of carbon dots. These techniques include Arc discharge, laser ablation, oxidation, water/solvothermal, and chemical vapor deposition. However, these techniques suffer from some limitations like the utilization of gaseous charged particles, high current, high temperature, potent oxidizing agents, non-environmentally friendly carbon sources, and the generation of uneven particle size. Therefore, there was a significant demand for the adoption of a new technology that combines the environmentally friendly aspects of both bio-based carbon sourcing and synthesis technique. ResultsMedicago sativa L (alfalfa)-derived N, S-CDs have been successfully synthesized via microwave irradiation. The N,S-CDs exhibit strong fluorescence (λex/em of 320/420 nm) with fluorescence quantum yield of 2.2 % and high-water solubility. The produced N,S-CDs were characterized using TEM, EDX, Zeta potential analysis, IR, UV–Visible, and fluorescence spectroscopy. The average diameter of the produced N, S-CDs was 4.01 ± 1.2 nm, and the Zeta potential was −24.5 ± 6.63 mv. The stability of the produced nano sensors was also confirmed over wide pH range, long time, and in presence of different ions. The synthesized N, S-CDs were employed to quantify the antibacterial drug, nifuroxazide (NFZ), by fluorescence quenching via inner filter effect mechanism. The method was linear with NFZ concentration ranging from 1.0 to 30.0 μM. LOD and LOQ were 0.16 and 0.49 μM, respectively. The method was applied to quantify NFZ in simulated gastric juice (SGJ) with % recovery 99.59 ± 1.4 in addition to pharmaceutical dosage forms with % recovery 98.75 ± 0.61 for Antinal Capsules® and 100.63 ± 1.54 for Antinal suspension®. The Method validation was performed in compliance with the criteria outlined by ICH. Significance and noveltyThe suggested approach primarily centers on the first-time use of alfalfa, an ecologically sustainable source of dopped-CDs, and a cost-effective synthesis technique via microwave irradiation, which is characterized by low energy consumption, minimized reaction time, and the ability to control the size of the produced CDs. This is in line with the growing global recognition of the implementation of green analytical chemistry principles.

Mathematical optimization modeling for scenario analysis of integrated steelworks transitioning towards hydrogen-based reduction

To reduce carbon dioxide emissions from the steel industry, efforts are made to introduce a steelmaking route based on hydrogen reduction of iron ore instead of the commonly used coke-based reduction in a blast furnace. Changing fundamental pieces of steelworks affects the functions of most every system unit involved, and thus warrants the question of how such a transition could optimally take place over time, and no rigorous attempts have until now been made to tackle this problem mathematically. This article presents a steel plant optimization model, written as a mixed-integer non-linear programming problem, where aging blast furnaces and basic oxygen furnaces could potentially be replaced with shaft furnaces and electric arc furnaces, minimizing costs or emissions over a long-term time horizon to identify possible transition pathways. Example cases show how various parameters affect optimal investment pathways, stressing the necessity of appropriate planning tools for analyzing diverse cases.

Effect of laser-assisted irradiation on plasma electrolytic oxidation of titanium alloys: Arc spot evolution characteristics and photoelectric synergistic mechanisms

Laser irradiation can be employed as an auxiliary energy field to optimize functional plasma electrolytic oxidation (PEO) coatings. Herein, the mechanism of the effect of laser-assisted irradiation on the morphology and composition of ceramic coatings prepared by PEO of titanium alloys in electrolytes with sodium tetraborate-based is discussed from the perspective of plasma arc spot evolution and photoelectric synergistic effect. X-ray diffraction (XRD), transmission electron microscopy (TEM), Mott-Schottky (M-S), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to analyze the coating characteristics. The results showed that laser-assisted irradiation promoted the oxidation of the coatings, accelerated the conversion of the anatase phase to the rutile phase, reduced the oxygen vacancy defects and formed the "ant nest" porous microstructure. Monitoring of the voltage, electric field, and plasma discharge arc spot indicated that laser-assisted irradiation restricted the electric field diffusion on the anode surface, reduced the termination voltage, and significantly increased the intensity (maximum discharge percentage increased from 14.238 % to 20.358 %) and uniformity of distribution of the plasma discharge. Instantaneous photoresponse curves and electrochemical impedance spectroscopy confirmed that the PEO coatings exhibited fast and sustained photoelectric response under simultaneous laser irradiation, progressively enhanced with increasing laser irradiation energy. The photogenerated electrons excited by the semiconductor TiO2 coating under the simultaneous irradiation of laser can be used as the initial carriers of the electron avalanche, which induces the generation of a plasma on the surface of the anode and thus enhances the plasma discharge behavior, which is the fundamental reason for the optimization of the coating characteristics.

Selective stabilization of chromium and sustainable treatment of stainless steel slags

Selective stabilization of chromium and sustainable treatment of industrial stainless steel electric arc furnace slags was investigated. The crystallization and phase distribution of stainless steel slags after equilibration at 1500 °C with varying basicity between 1.8 and 1.0 using quartz sand were studied. Results showed chromium in the slag can be fully stabilized into the Cr-spinel phase, which accumulate at the crucible bottom under the influence of gravity at a basicity of 1.2. The top liquid portion corresponding to about 72 % of the total slag can be quenched to an amorphous phase after a slag discharge treatment with the bottom residual solid portion in the form of a Cr-spinel enriched slag. The leaching experiments of the two separated slags were implemented according to the standard HJ/T 301–2007, and the Cr leaching concentrations were 0.059 mg/L and 0.136 mg/L, respectively. This was within the national comprehensive utilization standard of Cr-bearing solid wastes. Furthermore, the feasibility analysis of operation and potential application to the stainless steel industry was also addressed to provide the fundamentals for industrial scale utilization of stainless steel slags.

Carbon Nanotubes: A Review of Synthesis Methods and Applications

Carbon nanotubes (CNTs) are cylindrical-shaped materials composed of hexagonally arranged hybridized carbon atoms with versatility in synthesis methods and diverse applications. This review is focused on the fabrication, physicochemical and spectroscopic characterization, and industrial applications of CNTs. This review discusses some promising synthesis methods for the preparation of CNTs such as catalytic chemical vapor deposition, arc discharge, and laser ablation. A comparative discussion is made between these synthesis methods in terms of strengths, opportunities and challenges. Furthermore, functionalization and purification of CNTs’ surface leading to improved functionality has also been highlighted in this article. Finally, the analytical techniques employed to shed light on the physicochemical and morphological properties of CNTs are described.

The relationship between power of arc discharge in transformer oil and peak value of the shock wave

The relationship between power of arc discharge in transformer oil and peak value of the shock wave

Impact of different phase structure nano Al2O3 arc discharge prepared on MB dye removal

Nanocrystalline ceramic materials have great importance in the field of nanotechnology. Nano-sized materials have properties superior to bulk materials, including improved surface area-to-volume ratio and high strength and toughness. Nano alumina products were prepared in two different phases with different sizes, and shapes via a solid–liquid plasma reactor. Both yields were prepared in identical circumstances, but with different conditions that lead to produce different shapes, and phase structures (γ-Al2O3-NPs with a spherical shape, and δ-Al2O3-Nano-structure rhomboid shape). In this regard, 1.6 million tons of dyes are consumed each year. Trace of dyes in water may cause diseases if it exceeds the WHO limits. This paper describes the adsorption of methylene blue (MB) from aqueous solutions by two different nano structure alumina nano-adsorbents. The optimum contact time, adsorbent mass, and pH were determined, and adsorption isotherms were obtained using concentrations of MB ions ranging from 5 to 50 mg/L. The adsorption process shows significant differences of the coefficient of determination factor R2 for both yields for pseudo-first-order reaction kinetics, as well as Freundlish and intraparticle, film diffusion adsorption isotherms. Our results demonstrate that the adsorption process was spontaneous and exothermic under natural conditions. The maximum capacity of adsorbent for γ-Al2O3-NPs and δ-Al2O3-Nano-structure were 31.56 and 29.49 mg/g, respectively. This study revealed that nano structure γ-alumina was an effective adsorbent for removal of these ions from aqueous solutions.

Multi-physical field coupling modeling of microwave heating and reduction behavior of zinc oxide

Microwave heating provides a cleaner pyrometallurgical method for separating zinc from electric arc furnace dust (EAFD, a solid waste generated during steel production with excellent dielectric properties). Despite its undisputed heating efficiency, the impact of microwave heating characteristics on the zinc removal process from EAFD remains unclear. This paper focuses on ZnO, one of the primary components of EAFD, and develops an electromagnetic-thermal-chemical reaction model to analyze the effects of microwave power and graphite addition on heating behavior, reduction reactions, field distributions, and reaction kinetics. The results indicate that the heat generated from the interaction between microwaves and materials exhibits inherent non-uniformity, leading to the localized thermal effect and making the error of general temperature measurement methods. Increasing microwave power and adding graphite enhance heating efficiency and promote the reduction reaction but also result in significant internal-external temperature disparity and worse temperature distribution. At 1000 W, with 1.2 times the stoichiometric amount of graphite addition, the temperature measurement error reaches approximately 200 °C, potentially affecting the kinetic results to a certain degree. The non-isothermal kinetics results from simulations indicate that the localized thermal region exhibits a lower average activation energy of 47.5 kJ/mol compared to experimental results, suggesting that the lower activation energy of the ZnO reduction reaction during microwave heating is primarily caused by the localized thermal effect rather than the non-thermal effect. Additionally, in the energy distribution, the higher proportion of return loss during heating underscores the importance of a well-designed microwave heating system.

Growth of metal nanoparticles in hydrocarbon atmosphere of arc discharge

A direct current (DC) arc discharge is a widely used method for large-scale production of metal nanoparticles, core–shell particles, and carbon nanotubes. Here, the growth of iron nanoparticles is explored in a modified DC arc discharge. Iron particles are produced by the evaporation of an anode, made from low-carbon steel. Methane admixture into argon gas serves as a carbon source. Electron microscopy and elemental analysis suggest that methane and/or products of its decomposition adhere to iron clusters forming a carbon shell, which inhibits iron particle growth until its full encapsulation, at which point the iron core growth is ceased. Experimental observations are explained using an aerosol growth model. The results demonstrate the path to manipulate metal particle size in a hydrocarbon arc environment.

Antibacterial efficacy of decorated carbon nanotubes by nano silver against pseudomonas aeruginosa

Carbon nanotubes (CNTs) are considered as a promising nanomaterial for a variety of applications. It has desirable physicochemical characteristics of high surface area, superior mechanical and thermal strength, and electrochemical activity. In this study, CNTs decorated with silver nanoparticles (AgNPs) were manufactured by an arc discharge technique. As a result, etching produces stable AgNPs-CNTs aqueous suspensions of pure silver and carbon electrodes in ethanol vapor condensed in water. UV- visible photometer, x-ray Diffraction, transmission electron microscope, and energy dispersive x-ray characterized the synthesized AgNPs-CNTs. The synthesized AgNPs-CNTs crystals showed CNTs formation of an average 9.5 nm, with intermediate length position of about 75.8 nm decorated by homogeneous spherical AgNPs of average size 15.2 nm. The antibacterial efficiency of AgNPs-CNTs against Pseudomonas aeruginosa was established at a series of concentrations (45 g ml−1: 0.0879 g ml−1) while values for the MIC and MBC were determined. The MIC and MBC levels were found to be (>5.625 μg ml−1) and (>11.25 μg/ml) respectively. The bacteria cytotoxicity was evaluated through LDH and protein leakage levels. Treated samples with 3.2 μg ml−1 AgNPs-CNTs revealed significant injuries in the cell membrane by two times greater in LDH and protein leakage levels than samples treated by 5.0 μg ml−1 AgNPs. Results in this work substantiate the synergistic effect of combining AgNPs with CNTs to enhanced antibacterial properties and performance compared to AgNPs alone. The efficiency of using synthesized AgNPs-CNTs showed high antibacterial potential against Pseudomonas aeruginosa in a concentration-dependent manner. The arc discharge method can be adapted to incorporate different materials or change the synthesis conditions, allowing for the production of AgNPs-CNTs with tailored properties for specific applications.

Plasma plume enhancement of a dual-anode vacuum arc thruster with magnetic nozzle

Vacuum arc thruster (VAT) is a type of pulsed electric propulsion device that generates thrust based on vacuum arc discharges, it has great candidate for micro-newton force applications in orbit. To improve both the thrust and longevity of the VAT, a novel dual-anode structure, comprising a central anode and a ring anode, was developed. We conducted an investigation into the plasma discharge and acceleration process within the influence of a magnetic nozzle. The dual-anode architecture resulted in a reduction in the initial plasma impedance, thereby enhancing ion current and velocity. Analysis of surface parameters during discharge revealed a synergistic mechanism between the two insulator-conducting films, enabling a co-cyclic distribution of energy and resistance fluctuations within the discharge. Consequently, the dual-anode setup demonstrated a lifespan extension of at least twofold. Comparative analyses of arc energy, plasma velocity, ion current, and thrust variations with magnetic field strength were conducted between the dual-anode and single-anode configurations under magnetic nozzle influence. Results showed that the dual-anode structure increased ion current and velocity when subjected to magnetic nozzle influence, resulting in a thrust increase of up to 303%. Additionally, we developed a theoretical model for the diffusion coefficient to elucidate the adaptive splitting phenomenon of the arc within the dual-anode structure under magnetic field influence. This model suggests that the dual-anode structure can achieve a more significant enhancement in beam current from the magnetic nozzle compared to the single-anode configuration.

Study on the properties of deuterium ions in a composite cathode vacuum arc discharge

A vacuum arc discharge with a metal-deuteride cathode can generate a supersonic deuterium ion jet, which finds important applications in vacuum arc ion sources. In this study, a 1D3V spherical particle-in-cell direct simulation Monte Carlo cathode spot model with a titanium-deuteride cathode is developed to investigate the ionization and acceleration of deuterium ions from vacuum breakdown to the steady-arc stage. The effects of cathode deuteration concentration on the deuterium ion fraction and kinetic energy are also analyzed. The results show that the released deuterium atoms start to be ionized at around tens of nanometers from the cathode and then become fully ionized at about 0.4μm as the cathode potential drop gradually builds up. The proportion of deuterium ions in the plasma is slightly higher than the proportion of deuterium atoms in the cathode material. Velocity separation of deuterium and titanium ions occurs due to the acceleration of the electric field during the vacuum breakdown stage; however, the predominant ion–ion Coulomb collisions wipe out this separation in the steady-arc stage. Shifting the deuterium atom concentration in the cathode under a constant arc burning voltage produces an approximately equal current density, and increases the velocities of all ion species. A higher ion kinetic energy is gained by reducing the ohmic heating dissipation, facilitated by the lower plasma resistivity under the increased deuterium ion density.

A New Electric Arc Furnace Model Based on Current Waveform Synthesis From Distributions of DFT Amplitudes and Power System Frequency

A New Electric Arc Furnace Model Based on Current Waveform Synthesis From Distributions of DFT Amplitudes and Power System Frequency

Leaching behavior and compressive strength in the immobilization of Cs-137 contaminated electric arc furnace dust via doping with activated carbon

This study evaluated the potential of an immobilization technique to inhibit the migration and dispersion of Cs-137 contaminated electric arc furnace dust (EAFD) into the environment, by investigating its compressive strength and leaching characteristics. The EAFD was employed to replace ordinary Portland cement (OPC) in varied ratios, ranging from 0 % to 50 % by weight. The replacement was done using various water-binder ratios of 0.35, 0.40, 0.45, and 0.50. Furthermore, the use of activated carbon (AC) has been shown to minimize radionuclide and heavy metal discharge related to its high porosity. AC was added at weight concentrations of 0.5 %, 1.0 %, 1.5 %, and 2.0 %. Compressive strength and leaching tests are used to assess the long-term stability of waste forms and the effectiveness of immobilizing radioactive wastes, which is beneficial for storing and disposing of radioactive waste. The compressive strength is affected by the amount of EAFD, water-to-binder ratios, the addition of AC, and the duration of curing. Measurements of specific surface area, pore size, pore volume, and porosity were also carried out under various conditions. The research results indicate that the addition of AC improves the compressive strength and decreases the release of Cs-137 and heavy metals from the specimen. The mixture of 45 % EAFD and 1.5 % AC is appropriate for efficiently immobilizing Cs-137 contaminated EAFD.

Study of Voltage Flicker Mitigation Using Emulated Electric Arc Furnace

Study of Voltage Flicker Mitigation Using Emulated Electric Arc Furnace

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces

Application of a protective coating based on magnesium hydroxide to reduce oxidation of the side surface of graphitized electrodes in electric arc furnaces