Arc Discharge In Water Research Articles

Arbitrary Lagrange-Eulerian 기법을 활용한 액중 방전 성형의 해석적 연구

Abstract Electrohydraulic forming (EHF) is a high-speed forming process that uses an electric arc discharge in water. Shock waves resulting from the electric arc discharge are propagated to the blank through water and the blank moves toward the die. Advantages of EHF include improved formability due to the high-speed process and reduction of the bouncing effect. In the current study, a numerical simulation of EHF was developed using LS-DYNA. In the simulation, the model for the electric arc was assumed as an adiabatic gas expansion and an Arbitrary Lagrange-Eulerian (ALE) multi material formulation was used to describe the interaction between the electric arc and the water. In order to model the Fluid-Structure Interaction (FSI), a coupling mechanism was used. The blank of Al 1100-O was simulated using shell elements. The results of the simulation showed that the blank was deformed due to the pressure propagation of water and the bouncing effect did not affect the formability of blank.

The Effect of Dissolved Oxygen in Arc Medium on Crystal Structure and Optical Properties of Iron Based Nanoparticles Prepared via Dc Arc Discharge in Water

Electrical arc discharge in liquid is a fast, cost-effective and an environmentally benign way for synthesis of nanomaterials. In this research iron based nanoparticles were synthesized via DC arc discharge submerging in deoxidized water and the effect of dissolved oxygen in arc discharge medium on morphology, crystal structure and optical properties of nanoparticles were studied. For nanoparticle synthesis a discharge current of 40 A was applied between pure iron electrodes which were submerged in deoxidized water and kept about 8cm below the surface of water. Dissolved oxygen removal was performed by nitrogen gas bubbling for long time before arc discharge. Furthermore during synthesis a pressurized stream of nitrogen gas was directed perpendicular to the surface of deoxidized water. In addition, a sample was prepared in water without deoxidization under the same synthesis condition. The nanoparticles were characterized by X-ray diffraction (XRD), UV-visible spectroscopy and scanning electron microscopy (SEM). SEM results revealed that the particles were spherical with aspect ratios of about one. The average size of nanoparticle is below 30nm in both samples. It was concluded that the reaction of dissolved oxygen molecules available in deionized water with iron nanoparticles leads to oxidation of nanoparticles during nucleation, nanoparticles formation and especially after synthesis. Therefore the oxygen atom in water molecules and oxygen ions in arc plasma do not have a significant effect on oxidation of nanoparticles. These results demonstrate the importance of oxygen removal of water in arc discharge method for preparation of pure metallic nanoparticles without considerable oxidation.

The Effect of Surfactant on Colloidal Stability, Oxidation and Optical Properties of Aluminum Nanoparticles Prepared via Dc Arc Discharge in Water

Aluminum nanoparticles can be used in different applications such as high energetic materials and hydrogen producing. In this research aluminum nanoparticles were synthesized using DC arc discharge, and colloidal stability, oxidation and optical properties of the particles with and without the presence of surfactant were investigated. The liquids were deionized water without any surfactant, and 0.1M, 0.02M and 0.004M solutions of Sodium Dodecyl Sulfate (SDS) in deionized water. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy, were employed for characterization of particles size, shape, crystal structure and optical properties respectively. Solving the surfactant in water, resulted to a notable increase in the stability of the particles for 48hours after synthesis. The particles size were decreased from 37nm, to 35nm, 28nm and 24nm respectively in pure water, 0.1M, 0.02M and 0.004M solutions of SDS in deionized water. Moreover optical extinction spectra show, oxidation rate was decreased by increasing the SDS concentration. Adding the surfactant to arc discharge media, provides a simple and effective approach to control the size, colloidal stability and oxidation rate of the nanoparticles in this fast synthesis method.

Optical Properties of Ag-Cu Alloy Nanoparticles Synthesized by DC Arc Discharge in Liquid

Alloy nanoparticles are much interesting because their properties are flexible and can be very distinct with the particles of their constituents. Optical properties of alloy nanoparticles can differ by size effects and composition of their pure components. The aim of this article is studying the alloying and optical properties of Cu-Ag nanoparticles prepared via DC arc discharge in water with two different experimental procedures. Arc discharge was ignited between two pure silver and copper electrodes and two types of sample productions were held. The first one was based on using copper and silver wire with 99.99% purity as an anode and cathode electrodes and at the same 3mm diameter in each part by two different 40, 50 A current. Second one was using reversed sited electrodes. Optical properties, size and crystal structure of nanoparticles were characterized by UV-visible spectroscopy, Field Emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) respectively. SEM images show the nanoparticles are spherical with the average size of lower than 30nm for all samples. XRD results shows there are some displacements in Bragg diffraction angles of silver XRD peaks which is due to the positioning of Cu atoms among silver atoms and synthesis of Ag-Cu alloy nanoparticles. However some Ag-Cu alloy peaks were also observed. In comparison with the optical extinctions of pure copper and silver nanoparticles the optical extinctions of samples have the characteristic optical extinction of Ag-Cu alloy nanoparticles with extinction peak due to surface plasmon resonance that was observed between silver and copper nanoparticles extinction peaks. In addition optical properties of Ag-Cu alloy are more adjustable with arc current when using copper and silver wire as anode and cathode electrode respectively. The results provide a simple and flexible method for preparation and tuning optical properties of Ag-Cu nanoparticles.

TiO2 nanoparticles immobilized on carbon nanotubes for enhanced visible-light photo-induced activity

CNT–TiO2 nanocomposites were prepared through (i) simple mixing of as prepared CNTs and TiO2 nanoparticles (NPs), (ii) simple mixing of as prepared CNTs and TiO2 NPs followed by heat treatment and (iii) simple mixing of as prepared CNTs and TiO2 NPs followed by UV illumination. The synthesis of CNTs and TiO2 NPs were performed individually by arc discharge in water and sol–gel methods, respectively and characterized by X-ray diffraction (XRD), ultra violet and visible spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The visible-light photocatalytic performance of CNT–TiO2 nanocomposites was successfully demonstrated for the degradation of Rhodamine B (Rh. B) as a model dye at room temperature. It is found that CNT–TiO2 nanocomposites extended the light absorption spectrum toward the visible region and considerably improved the photocatalytic efficiency under visible-light irradiation. The visible-light photocatalytic activities of CNT–TiO2 nanocomposites in which CNTs are produced by arc discharge in deionized (DI) water at 40, 60 and 80A arc currents and combined through three different protocols are also investigated. It was found that samples prepared at 80A arc current and 5s arc duration followed by UV illumination revealed best photocatalytic activity compared with the same samples prepared under simple mixing and simple mixing followed by heat treatment. The enhancement in the photocatalytic property of CNT–TiO2 nanocomposites prepared at 80A arc current followed by UV illumination may be ascribed to the quality of CNTs produced at this current, as was reported before.

Electric discharge technology of production and diagnosis of metallic hydrosols with nanosized particles

A method of producing silver hydrosols by dispersion in an arc discharge in water is proposed. Experiments and model calculations show that the size of the resulting silver nanoparticles of ∼4 nm is close to the minimum possible size of a stable nucleus. The particles become larger over time; however, their average size does not exceed 0.5 μm even after long-term storage. Positive results on the use of silver hydrosols in veterinary medicine are obtained.

Submerged arc discharge technique to explore novel non-carbon nanotubes: Syntheses of nanotubes from ZnO and BaTiO3

A unique reaction field using arc discharge in water can create novel nanostructures, where an extreme temperature drop is observed in bubbles around a hot arc plasma zone. Here, a Mo anode had a hole at its tip, into which ZnO or BaTiO3 powder was stuffed. The cathode received film products on its surface. It was revealed that BaTiO3 nanotubes were firstly synthesized as novel nanotubes when BaTiO3 powder was stuffed in the anode hole. When ZnO powder was stuffed in the anode hole, narrow ZnO nanotubes were synthesized. The diameter of the ZnO nanotubes synthesized was the smallest ever reported.

Electrical characteristics of Al<sub>2</sub>O<sub>3</sub> and Ta<sub>2</sub>O<sub>5</sub> nanoparticles synthesized by DC anodic ARC-discharge in water

Because of the length scale and high specific surface area of nanometer-sized particles, they exhibit novel properties as compared with their bulk counterpart materials. Furthermore, the incorporation of well-characterized nanoparticles in various organic matrices provides dielectrics with improved electrical, mechanical and thermal features. Alumina and tantalum-pentoxide nanoparticles have been proved efficient fillers in such nanocomposites. These specific particles are herein produced by DC anodic arc-discharge immersed in water and they are probed by means of broadband dielectric spectroscopy in a wide temperature range (-100 to 100 °C). Different formalisms (effective dielectric constant, loss factor and specific conductivity) are combined, providing the possibility to determine the frequency and temperature dependence of the dielectric characteristics of the synthesized nanoparticles. The knowledge of the latter should be determinant for potential application of alumina and tantalum-pentoxide fillers to two-phase heterogeneous nanodielectrics.

Electrical characteristics of Al2O3 and Ta2O5 nanoparticles synthesized by DC anodic ARC-discharge in water

Because of the length scale and high specific surface area of nanometer-sized particles, they exhibit novel properties as compared with their bulk counterpart materials. Furthermore, the incorporation of well-characterized nanoparticles in various organic matrices provides dielectrics with improved electrical, mechanical and thermal features. Alumina and tantalum-pentoxide nanoparticles have been proved efficient fillers in such nanocomposites. These specific particles are herein produced by DC anodic arc-discharge immersed in water and they are probed by means of broadband dielectric spectroscopy in a wide temperature range (-100 to 100 °C). Different formalisms (effective dielectric constant, loss factor and specific conductivity) are combined, providing the possibility to determine the frequency and temperature dependence of the dielectric characteristics of the synthesized nanoparticles. The knowledge of the latter should be determinant for potential application of alumina and tantalum-pentoxide fillers to two-phase heterogeneous nanodielectrics.

Influence of Pulse Condition in the Synthesis of Carbon Nanotubes Containing Tungsten by Arc Discharge in Water

Influence of Pulse Condition in the Synthesis of Carbon Nanotubes Containing Tungsten by Arc Discharge in Water

Influence of Pulse Condition in the Synthesis of Carbon Nanotubes Containing Tungsten by Arc Discharge in Water

We studied the one-step synthesis of carbon nanotubes (CNTs) containing metal by arc discharge in water, a technique by which we can synthesize CNTs using a simple device. In this study, we attempted to improve the rate of tungsten (W) inclusion by applying a pulsed arc discharge. By this technique, we found that the quantity of CNTs containing W increased compared with the results of using DC arc discharge. Furthermore, after investigating the effect of the correlation between pulse width and duty cycle on the rate of formation of CNTs containing W, it was determined that the maximum rate (30%) was achieved when the pulse width was 5 ms and the duty cycle was 50%.

Synthesis of graphene nanosheets from petroleum asphalt by pulsed arc discharge in water

The synthesis of graphene nanosheets has been achieved by pulsed arc discharge in water with petroleum asphalt as a carbon source. The synthesized graphene nanosheets were examined by Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy and atomic force microscopy. The results indicate that most of as-synthesized graphene nanosheets have 2–5 layers, and small amounts of them have sheets in the range of 5–10 layers. The optical emission spectroscopy was used to monitor the arc discharge process, which indicates that the released hydrogen from asphalt may play a key role in the formation of graphene.

One-Step Synthesis of Metal-Encapsulated Carbon Nanotubes by Pulsed Arc Discharge in Water

One-Step Synthesis of Metal-Encapsulated Carbon Nanotubes by Pulsed Arc Discharge in Water

Plasma of Arc Discharge in Water for the Formation of Diverse Nanostructures Dependent on the Anode Material

Anodic dc arc discharge in water is herein used as an efficient medium for production of nanomaterials with high technological interest. The plasma created mainly consists of ionized and excited species of dissociated water and evaporated element of the anode electrode. Depending on the anode material, diverse and compelling crystalline nanostructures are formed, probably initiated by the supersaturation processes taking place in the plasma phase. This physical effect is visualized by the images presented in this paper.

CuO/Ta 2O 5 core/shell nanoparticles produced by arc-discharge in water

The formation of novel nanoparticles, i.e. CuO/Ta 2O 5 core/shell, via anodic arc-discharge in water is reported. Typical core diameters and shell thicknesses are about 20 and 5 nm, respectively. Both core and shell are crystalline. The resulting core/shell-structured nanopowder exhibits dielectric behavior.

Characteristic Analysis of AC Plasma Arc in Water

An experimental system of AC arc discharge in water was designed with pole-pole electrodes and a peak voltage of 1500 V and a test circuit was set up using virtual instrument technology. The mechanism of an AC plasma arc generated in water was analyzed. The voltage-current characteristic of the AC plasma arc was obtained from the waveform. The temperature characteristic was tested with a spectrum diagnosis system, and the effect of different electrode materials on the striking voltage and peak current was analyzed. The results show that when a power supply of 6 kW is applied on electrodes with a gap of 2 mm in water, the striking voltage is from 900 V to 1300 V, the arc voltage is from 40 V to 100 V, the arc current is from 2 A to 7 A, and the zero rest period is from 1 ms to 2 ms. In addition, the arc voltage and current are different for electrodes in aluminum, copper and stainless steel. The arc voltage is lower and the current is higher for an aluminum electrode than those for copper and stainless steel ones. The highest temperature of the arc is 7643 K.

Carbon Nanotube Synthesis by Arc Discharge in Water Using Metal Cathodes

Carbon nanotube (CNT) synthesis by arc discharge in water can yield high-crystallinity CNTs using simple equipment. However, it is difficult to control the morphology of CNTs, such as their length, diameter, and number of layers, because the mechanism of CNT production by arc discharge method is complicated. We describe how the morphology of CNTs depends on the cathode metal used in arc discharge. When a nickel or tungsten cathode was used, the layer number distribution was narrower than when a graphite electrode was used. Additionally, the peak position of the inner diameter distribution was downshifted in the case of tungsten. The downshift is considered to be caused by the presence of tungsten nanoparticles as a catalyst. [DOI: 10.1380/ejssnt.2010.203]

Transient Phenomena and Crater by Pulsed Microgap Arc Discharge in Water

Concerning about the pulsed current discharge in water which used for rough machining process of wire electric discharge machining, we performed measurements of single pulsed arc voltage, observed the developing process of arc discharge by using ICCD camera and examined discharge crater dependence on the discharge current. Based on these result of measurements of transient arc phenomena, we constructed a simple discharge model of arc plasma extension. As a result, we proposed the optimal pulsed discharge current under various processing conditions to improve the machining performance for Wire-EDM. The analysis of the pulsed arc discharge phenomena will form the basis of technology for realizing high-performance drive control schemes for Wire-EDM.

Degradation of 4-chlorophenol by pulsed arc discharge in water - estimation of the energy consumption

Pulsed arc (electrohydraulic) discharge process (PAED) has been studied for the removal of some organic pollutants. Firstly, the destruction of para-chlorophenol by PAED system was studied under some different experimental conditions (ionic content, pH, conductivity and organic initial concentration) in a 5.6 L reactor, with the following configuration: 2.9 kV of potential, 140 μF of capacitors. Secondly, the energy consumption for the degradation of 4-CP was estimated. From four initial concentrations of 4-CP, the energy consumption was found to be about 3.5 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> kJ/mol. A comparison between PAED efficiency and UV-254 nm, O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> systems is finally presented.

γ-Al2O3 nanoparticle production by arc-discharge in water: in situ discharge characterization and nanoparticle investigation

γ-Al2O3 crystalline nanoparticles (NPs) are for the first time produced by the arc-discharge in water method. The discharge is studied in situ during the NP formation by simultaneously recording the voltage and current waveforms, emitted light intensity and time-resolved optical emission spectra and snapshots of the discharge. The microstructure of the NPs is investigated by high-resolution transmission electron microscopy, the chemical purity is confirmed by x-ray photoelectron spectroscopy and the crystalline structure by x-ray diffraction. The results experimentally demonstrate the successive phases that lead to the supersaturation condition governing this gas-phase bottom–up process for dielectric NP production.