Hydrogen Arc Research Articles

Exploring Extreme Voltage Events in Hydrogen Arcs within Electric Arc Furnaces

This study highlights the potential utilization of hydrogen gas in electric arc furnaces for achieving cleaner and more sustainable steel production. The application of hydrogen offers a promising path for reducing carbon emissions, enhancing energy efficiency, and advancing the concept of “green steel”. This study employs a 2D axisymmetric induction-based model to simulate an electric arc under atmospheric pressure conditions. We conducted numerical simulations to compare compressible and incompressible models of an electric arc. The impact of compressibility on hydrogen arc characteristics such as arc velocity, temperature distribution, and voltage drop were investigated. Additionally, different applied current arcs were simulated using the compressible model. When compared to an incompressible arc, the compressible arc exhibits a higher voltage drop. This higher voltage drop is associated with lower temperatures and lower arc velocity. A rise in applied current results in an upward trend in the voltage drop and an increase in the arc radius. In addition, the increased applied current increases the probability of voltage fluctuations. The voltage fluctuations tend to become more extreme and exert more stress on the control circuit. This has an impact on emerging electric arc technologies, particularly those involving the use of hydrogen. These fluctuations affect arc stability, heat output, and the overall quality of processes. Thus, the precise prediction of voltage and the ability to stabilize the operation is critical for the successful implementation of new hydrogen technologies.

Electrical and Optical Investigation of an Electric Arc in Hydrogen for short gaps

Hydrogen or mixtures containing hydrogen represent attractive gases for low-voltage switching devices because of increased arc quenching behaviour. However, fundamental electrical properties of arcs in hydrogen are still not well known. In this paper, first results of a study of a DC switching arc in pure hydrogen at 1 bar between graphite electrodes are presented for low currents of 8 and 16 A. The arc voltage and current are measured during contact separation. High-speed images of the arc are processed to determine the arc length considering the high arc dynamics with erratic elongations and jumps of the electrode attachment. The arc voltage dependence on the length results in a typical sheath voltage of approximately 23 V and mean electric fields in the arc column of 18.7 V/mm at 8 A and 10.8 V/mm at 16A.

Hydrogen arc plasma promotes the purification and nanoparticle preparation of tungsten

As an important refractory metal, tungsten (W) has unique physical-chemical properties, and the applications of high-quality tungsten NPs with uniform particle size, high purity, and good particle dispersion in industrial fields are highly desirable. Herein, the integration of tungsten metallurgical purification and nanoparticle preparation is achieved by the hydrogen arc plasma method. In the process of purification, on the condition of arc current of 250 A, hydrogen concentrations of 30 vol%, purification time of 40 min, and gas pressure of 60 kPa, the highest impurity removal rate is achieved. The active H+ is able to react with impurities to generate metal hydride (MH, M = Al, Cr, Mg, and Fe), which promotes the removal rate of impurity elements. During the preparation of nanoparticles (NPs), the as-prepared tungsten NPs with an average particle size of 44.1 nm have a regular spherical structure, high purity, and a relatively uniform particle size distribution. When the hydrogen concentration is controlled at 50 vol%, the extremely high temperature promotes the evaporation of tungsten. Meanwhile, the active H+ reacts with tungsten to form tungsten hydride (WH), further increasing the evaporation rate of tungsten. According to the above results, the hydrogen arc plasma promotes the simplification of the production process steps of high purity tungsten NPs and reduces the industrialized production cost of high-quality refractory metal NPs.

Hydrogen Arc Plasma Promotes the Purification and Nanoparticle Preparation of Tungsten

Hydrogen Arc Plasma Promotes the Purification and Nanoparticle Preparation of Tungsten

Simulation and Experimental Analysis of DC Arc Characteristics in Different Gas Conditions

The structures of high-voltage direct current (HVDC) relays are compact. In order to extinguish the arc, the external magnetic field is applied near the contact. HVDC relays with a large capacity are also filled with gas medium to enhance the ability of arc extinguishing. The research on the characteristics of the arc in different gases under different pressures is of great significance to improve the reliability and the lifetime of the HVDC relays. The characteristics of the arc in nitrogen, hydrogen, and nitrogen–hydrogen mixtures and that of the arc root motion in the magnetic field are simulated by means of magnetohydrodynamics (MHD). The arcing processes in N2 and air are tested by a high-speed camera, and the arc root coordinates are calculated by the image processing method, and the simulation models are verified. The result shows that under the same condition, the hydrogen arc voltage is the highest, and the moving speed of the arc root is the fastest, so that the arc extinguishing performance of the hydrogen is the best. Nitrogen–hydrogen mixture is also a superior arc extinguishing gas, and the higher the proportions of H2, the better the performance. With the increase of the pressure, arc voltage increases. Except H2, increasing the pressure of the gas is beneficial for arc motion.

High-yield growth of multi-walled carbon nanowires by magnetic field controlled arc technique

Multi-walled Carbon nanowires (MWCNWs) made of long linear carbon chains inside multi-walled carbon nanotubes (LLCC@MWCNTs) have been successfully prepared by magnetic field enhanced hydrogen arc discharge. It has been found that introducing a static magnetic field into the conventional hydrogen arc discharge method can not only improve the growth yield but also expand the range of preparation parameters of MWCNW samples. Combining with the characterization and simulation, it can be summarized that the magnetic field helps to increase the arc plasma temperature which play an important role in the growth process of MWCNWs. The work presents a new convenient and practical approach to enhance the preparation of MWCNWs and will contribute to the further researches on the new one-dimensional allotrope.

Investigation of the Arc Characteristics of Switching DC Arcs on Hydrogen Containing Gas Mixtures

The characteristics of switching DC current arcs in hydrogen containing gas mixtures under pressure were investigated using a model chamber. The switching device consists of an electro-mechanic double breaker unit with copper contacts. High-speed imaging and spectroscopy were used to observe and to characterize the switching arc. The experiments indicate how the dynamic interaction of an external magnetic field with a high-pressure discharge causes an elongation and twisting of the arc-channel and consequently a voltage increase. Comparative measurements with and without external magnetic field indicate a strong influence of this factor. Cu and N lines together with strongly broadened H lines were observed.

Preparation of long linear carbon chain inside multi-walled carbon nanotubes by cooling enhanced hydrogen arc discharge method.

Long linear carbon chains with sp hybridization inside multi-walled carbon nanotubes (LLCC@MWCNTs) can be prepared in the cathode deposits obtained by hydrogen arc discharge. In this work, a cooling system was introduced into the hydrogen arc discharge method to improve the growth yield of LLCC@MWCNTs samples, as indicated by the corresponding stronger Raman peaks between 1780 cm-1 and 1880 cm-1, compared with conventional systems. Moreover, the cooling largely expanded the narrow scope of suitable conditions for the preparation of LLCC@MWCNTs, and high purity samples were easily produced. Qualitative analysis of arc discharge process helped conclude that cooling helps to increase the temperature of arc plasma, which is beneficial to improve both the growth yield of LLCC@MWCNTs and the purity of MWCNTs. This work provides a new approach to improve the growth yield of LLCC@MWCNTs and will benefit further studies and future applications of this new one-dimensional allotrope.

A simplified model for the determination of current-voltage characteristics of a high pressure hydrogen plasma arc

This paper focuses on the modeling of a hydrogen arc column at very high pressure (20 bar). The problem is solved from Elenbaas-Heller equation where the radiation is carefully considered with the net emission coefficient. The absorption spectrum requires the integration of background continuum, molecular bands, and line spectra. This work directly aims to predict the electric current-voltage characteristics which is key for the design of new processes. We propose also a new analytic solution which generalizes the channel model of electric arc to the case when the volume radiation makes a significant contribution to the energy balance. The presented formalism allows a better determination of the plasma thickness parameter Rp for net emission coefficient method in cylindrical arcs and gives satisfactory results in comparison to earlier experimental works on high pressure hydrogen plasma.

Separating Technology of Pure Zirconia from Zircon-Sand by the Ar-H<sub>2</sub> Arc Plasma Fusion and the Microwave Leaching

Zirconia (ZrO2) has excellent properties such as high toughness, high strength, thermal stability and high corrosion resistance. Thus, recent zirconia has been spotlighted as a dental material. Most of pure zirconia has been separated from zircon sand (ZrSiO4) by wet refining process which is very complex and not an environmental. The arc plasma fusion method has the advantages as a sustainable process that can easily and quickly get very good fine and high pure powders from the original materials compared with traditional wet method. In this study, zircon sand is separated into zirconia and silica by using the Ar-H2(hydrogen) arc plasma refining. And then silica is removed from it by the microwave leaching method to produce a high pure zirconia. Argon gas, hydrogen gas, copper anode and tungsten cathode are used for the plasma arc generation. To facilitate zirconia and silica separation, carbon of 1-3molar ratios are added with zircon sand. Plasma melting were sequentially conducted two processes. After a reduction process using Ar gas only, it was refined using a mixed gas of Ar-H2. After melting and water cooling in chamber, the solid phases composed with zirconia and silica were obtained at 240 ̊C, and 20% sulfuric acid solution was used as the leaching materials to obtain a high purity zirconia (more than 99%).

Optimization of the plasma parameters for the high current and uniform large-scale pulse arc ion source of the VEST-NBI system

A large-scale hydrogen arc plasma source was developed at the Korea Atomic Energy Research Institute for a high power pulsed NBI system of VEST which is a compact spherical tokamak at Seoul national university. One of the research target of VEST is to study innovative tokamak operating scenarios. For this purpose, high current density and uniform large-scale pulse plasma source is required to satisfy the target ion beam power efficiently. Therefore, optimizing the plasma parameters of the ion source such as the electron density, temperature, and plasma uniformity is conducted by changing the operating conditions of the plasma source. Furthermore, ion species of the hydrogen plasma source are analyzed using a particle balance model to increase the monatomic fraction which is another essential parameter for increasing the ion beam current density. Conclusively, efficient operating conditions are presented from the results of the optimized plasma parameters and the extractable ion beam current is calculated.

Mechanism of Enhanced Vaporization from Molten Metal Surface by Argon–Hydrogen Arc Plasma

A DC arc with hydrogen addition is one of the promising routes to prepare nanoparticles with high productivity. The purpose of this study is to investigate the mechanism of vaporization enhancement of a particular metal from a molten metal mixture by the DC arc method with hydrogen addition. The selective enhanced vaporization of Sn from a Sn–Ag molten mixture by an Ar–H2 arc was confirmed. Spectroscopic measurements were conducted to investigate the vaporization mechanism on the anode boundary region. The obtained results indicated that Sn was mainly vaporized as SnH from the molten Sn–Ag mixture, which decomposed to H and Sn vapor soon after SnH was vaporized. The mechanism of the vaporization enhancement of particular metal from a molten metal mixture by an Ar–H2 arc is mainly attributed to the formation of the metal hydride.

Pt–Fe catalyst nanoparticles supported on single-wall carbon nanotubes: Direct synthesis and electrochemical performance for methanol oxidation

Single-wall carbon nanotubes (SWCNTs) supported Pt–Fe nanoparticles have been prepared by one-step hydrogen arc discharge evaporation of carbon electrode containing both Pt and Fe metal elements. The formation of SWCNTs and Pt–Fe nanoparticles occur simultaneously during the evaporation process. High-temperature hydrogen treatment and hydrochloric acid soaking have been carried out to purify and activate those materials in order to obtain a new type of Pt–Fe/SWCNTs catalyst for methanol oxidation. The Pt–Fe/SWCNTs catalyst performs much higher electrocatalytic activity for methanol oxidation, better stability and better durability than a commercial Pt/C catalyst according to the electrochemical measurements, indicating that it has a great potential for applications in direct methanol fuel cells.

Synthesis of coaxial nanocables of single-walled carbon nanotubes sheathed with amorphous silicon oxide

Coaxial nanocables of single-walled carbon nanotubes (SWCNTs) sheathed with amorphous silicon oxide were directly synthesized by a hydrogen arc discharge method. As-prepared nanocables are usually tens of microns in length and about 10–30 nm in diameter. The sheath of the nanocables is amorphous silicon oxide, while the core is high quality SWCNTs. Each cylinder-shaped nanocable contained one to several SWCNTs. The growth mechanism of the nanocables is proposed. These SWCNT/amorphous silicon oxide nanocables may have potential applications in field effect transistors and other related nanodevices.

Deoxidation of bulk metallic glasses by hydrogen arc melting

Hydrogen arc melting (HAM) was conducted to investigate the deoxidization effects of HAM on Zr-based alloys. The effects of the hydrogen percentage and melting duration on the oxygen content and glass-forming ability of Zr55Cu30Ni5Al10 alloys were studied. Because of the increase in the hydrogen percentage and the melting duration, the oxygen content of the alloys greatly decreased after HAM, which alleviated the detrimental effect of oxygen and improved the glass-forming ability. Thus, HAM-deoxidation may provide an effective and simple method to remove the oxygen from Zr-based metallic glasses, which can improve the prospects for widespread applications of Zr-based metallic glasses.

Preparation of Ag–Fe-decorated single-walled carbon nanotubes by arc discharge and their antibacterial effect

A simple one-step approach for the preparation of Ag–Fe-decorated single-walled carbon nanotubes (Ag–Fe/SWCNTs) by DC hydrogen arc discharge is presented in this article. The growth of SWCNTs and the attachment of Ag and Fe nanoparticles to the SWCNTs occur simultaneously during the arc discharge evaporation process. It has been confirmed that the Ag and Fe nanoparticles in the diameter range of 1–10 nm are well dispersed and tightly attached to the outer surfaces of SWCNTs. The as-grown Ag–Fe/SWCNTs have been purified by high-temperature hydrogen treatment to remove amorphous carbon and carbon shells. Antibacterial tests show that the antibacterial activity of the purified Ag–Fe/SWCNT hybrid nanoparticles is excellent against Escherichia coli. The percentage of the E. coli killed by 100 μg/ml Ag–Fe/SWCNTs can reach up to 85.1 % at a short residence time of 2 h, suggesting that the purified Ag–Fe/SWCNTs may have potential antibacterial applications.

A simple and universal method for fabricating linear carbon chains in multiwalled carbon nanotubes

Long linear carbon chains (C-chains) have been fabricated inside multiwalled carbon nanotubes (MWCNTs) by a simple method based on high-temperature treatment of MWCNTs with the innermost tube diameters of ~0.7nm. The MWCNTs were prepared by hydrogen arc discharge, and then were fully purified by heat-treatment in air. After the purified MWCNTs were heated at 1500°C in inert atmosphere, the characteristic Raman peak of carbon nanowires (CNWs) were found to appear at ~1855cm−1, showing the formation of C-chain inside MWCNTs, i.e. C-chain@MWCNT. Raman spectra of CNWs prepared by high-temperature treatment of MWCNTs including double-walled carbon nanotubes and by hydrogen arc discharge are compared, and the formation mechanism is discussed.

Synthesis of few-walled carbon nanotube–Rh nanoparticles by arc discharge: Effect of selective oxidation

Abstract Highly crystalline rhodium (Rh) nanoparticles supported on carbon nanotubes were prepared by selective oxidation method. Carbon nanotubes and FeRh nanoparticles were simultaneously generated in hydrogen arc plasma. The as-grown nanomaterials can be purified by heat treatment in open air and by soaking in HCl. X-ray diffraction and selected area electron diffraction results reveal that as-grown FeRh nanoparticles have a typical chemical CsCl-type structure which can be transformed into a face-centered cubic structure by thermal annealing in the purification process. The purification process is selective toward the removal of the amorphous carbon coating the nanoparticles, and transforms Fe to Fe2O3. Fe2O3 can be easily dissolved in hydrochloric acid, leaving carbon nanotubes–Rh nanoparticles. Rh nanoparticles with diameters of 2–60 nm are deposited uniformly on the surface of the carbon nanotube bundles. This simple and selective chemistry offers a new process for synthesizing and controlling Fe content in carbon nanotube–FeRh nanoparticles.

Synthesis of vertically-aligned carbon nanotubes without a catalyst by hydrogen arc discharge

Vertically-aligned carbon nanotubes (CNTs) were prepared by hydrogen arc discharge, using pure graphite powder as carbon source without catalysts added. Scanning and transmission electron microscopy characterizations show that the aligned CNTs have a bamboo-like structure, and their lengths and diameters are about 30μm and 40–60nm, respectively. No metallic impurities can be detected in the samples by careful X-ray photoelectron spectroscopy detection. The activation of hydrogen radicals, the heating effect of the arc, and the electric field surrounding the arc column area are considered to play important roles for the non-catalyst growth of the CNTs.

An all carbon counter electrode for dye sensitized solar cells

This article describes the design and operation of a dye sensitized solar cell with an all carbon counter electrode and plastic electrolyte. For the construction of the counter electrode, the conventional thin platinum catalytic layer was replaced by a novel large-effective-surface-area polyaromatic hydrocarbon (LPAH) film, and the fluorine doped tin oxide substrate was replaced by a graphite film. In this way the internal resistance of the cell was substantially reduced and the cell efficiency can reach nearly 9% using the masked frame measurement technique. To achieve such an efficiency, a series of experiments was carried out to assure that the LPAH layer possesses superior catalytic activity and energy efficiency compared to the commonly used carbon black. To this end a unique LPAH layer synthesis technique was developed. It involved the production of LPAH from a hydrogen arc along with the use of an amphiphilic triblock copolymer (P123) to improve the suspendability of LPAH to form a homogeneous catalytic layer. This layer was then attached to a graphite film to form the counter electrode for the dye sensitized solar cell. Details of the properties of the LAPH and the newly designed solar cell are reported herein.