High-voltage Arc Research Articles

Effect of nanosilver in wheat seedlings and Fusarium culmorum culture systems

The purpose of this study was to examine the effect of silver nanoparticles (AgNPs) produced using the high-voltage arc discharge method on the growth and metabolism of common wheat seedlings. Additionally, a simultaneous assessment of the AgNP-induced reduction in seedling infection by Fusarium culmorum (Fc) was performed. AgNP- and Fc-treated seedlings indicated that both factors considerably inhibited their growth. A significant Fc-induced reduction in seedling blight was observed following treatment with AgNPs; however, treatment with nanoparticles was also accompanied by a serious disintegration of the cell membranes of roots. Moreover, treatment with AgNPs increased the quantum efficiency of energy trapping in the PSII reaction centre (Fv/Fm) with a simultaneous decrease in energy dissipation in the form of heat. Induction of photosynthesis in the presence of AgNPs did not affect height but was reflected in higher total dry weight. Moreover, analysis of antioxidant enzyme activity typical for the stress response indicated the toxicity of AgNPs treatment compared to Fc treatment. Seedlings exposed to AgNP activity demonstrated accumulation of Ag in roots and its translocation to aerial parts, while the pathogen reduced both accumulation and translocation of this element.

Experiment and simulation analysis of surface structure for CuW contact after arc erosion

As an electrical contact, CuW alloy tends to be eroded under high voltage arc, and cracks would appear on the surface of the contact. Arc erosion experiments under high voltage arc were implemented on CuW contact, and then the inner stresses were analysed with the finite element method. Results showed that the surface of the CuW contact was changed to graded structure, including tungsten, tungsten skeleton and CuW alloy, with the increase in arcing cycle, and microcracks initiated and then propagated into the depth mainly due to transverse stresses. During arcing, the temperature and induced thermal stress were improved because of the appearance of graded structure on the surface, and then the erosion and cracks were enhanced. Hence, the failure mechanism of CuW contact was revealed.

Divertor impurity injection using high voltage arcs for impurity transport studies on the Mega Amp Spherical Tokamak.

The operation of next-generation fusion reactors will be significantly affected by impurity transport in the scrape-off layer (SOL). Current modelling efforts are restricted by a lack of detailed data on impurity transport in the SOL. In order to address this, a carbon injector has been designed and installed on the Mega Amp Spherical Tokamak (MAST). The injector creates short lived carbon plumes originating at the MAST divertor lasting less than 50 μs. High voltage capacitor banks are used to create a discharge across concentric carbon electrodes located in a probe mounted on the Divertor Science Facility in the MAST lower divertor. This results in a very short plume duration allowing observation of the evolution of the plume and precise localisation of the plume relative to the X-point on MAST. The emission from the carbon plume was imaged using fast visible cameras filtered in order to isolate the carbon II and carbon III emission lines centered around 514 nm and 465 nm.

Photoluminescence of CdTe nanocrystals grown by pulsed laser ablation on a template of Si nanoparticles

CdTe nanocrystals were grown on eroded Si (111) substrates at room temperature by pulsed laser ablation. Before growth, Si substrates were subjected to different erosion time in order to investigate the effect on the CdTe samples. The erosion process consists of exposition to a pulsed high-voltage electric arc. The surface consequence of the erosion process consists of Si nanoparticles which acted as a template for the growth of CdTe nanocrystals. CdTe samples were studied by X-ray diffraction (XRD), room temperature photoluminescence (RT PL) and high-resolution transmission electron microscopy (HRTEM). CdTe nanocrystals grew in the stable cubic phase, according to XRD spectra. A strong visible emission was detected in photoluminescence (PL) experiments. The PL signal was centered at 540 nm (~2.34 eV). With the effective mass approximation, the size of the CdTe crystals was estimated around 3.5 nm. HRTEM images corroborated the physical characteristics of CdTe nanocrystals. These results could be useful for the development of CdTe optoelectronic devices.

Calculation of combined diffusion coefficients in SF6-Cu mixtures

Diffusion coefficients play an important role in the description of the transport of metal vapours in gas mixtures. This paper is devoted to the calculation of four combined diffusion coefficients, namely, the combined ordinary diffusion coefficient, combined electric field diffusion coefficient, combined temperature diffusion coefficient, and combined pressure diffusion coefficient in SF6-Cu mixtures at temperatures up to 30 000 K. These four coefficients describe diffusion due to composition gradients, applied electric fields, temperature gradients, and pressure gradients, respectively. The influence of copper fluoride and sulfide species on the diffusion coefficients is shown to be negligible. The effect of copper proportion and gas pressures on these diffusion coefficients is investigated. It is shown that increasing the proportion of copper generally increases the magnitude of the four diffusion coefficients, except for copper mole fractions of 90% or more. It is further found that increasing the pressure reduces the magnitude of the coefficients, except for the combined temperature diffusion coefficient, and shifts the maximum of all four coefficients towards higher temperatures. The results presented in this paper can be applied to the simulation of high-voltage circuit breaker arcs.

Exergy of Nano-Particulate Materials

Nano-particle (NP) production processes may involve the use of significant amounts of complex chemicals. A more advanced approach for producing metallic NP materials may be the use of high voltage arc- or spark-driven systems. In addition to a reduction in chemicals use, the energy use of arcs/sparks exclusively in the form of electricity may be significantly less than the energy needs of waste stream processing from chemical usage, handling and post-treatment in nano-tech industry. Using exergy as a fundamental tool we assess the energy efficiency of NP material production, a subject obscured by lack of data and literature. One goal of this paper is to introduce a description of the exergy of NP materials and their processing. Silver, gold, copper, nickel, zinc and aluminium were taken as case studies. The results show that especially for NP material < 20 nm the surface energy of the material becomes significant. Moreover, a large energy penalty results from temperatures and enthalpies of NP condensation and solidification being lower than values for melting and evaporation of the bulk material. Comparing theoretical values with results from experiments shows that the specific electricity consumption is orders of magnitude higher than the energy penalties calculated as inevitable.

Parallel vacuum arc discharge with microhollow array dielectric and anode

An electrode configuration with microhollow array dielectric and anode was developed to obtain parallel vacuum arc discharge. Compared with the conventional electrodes, more than 10 parallel microhollow discharges were ignited for the new configuration, which increased the discharge area significantly and made the cathode eroded more uniformly. The vacuum discharge channel number could be increased effectively by decreasing the distances between holes or increasing the arc current. Experimental results revealed that plasmas ejected from the adjacent hollow and the relatively high arc voltage were two key factors leading to the parallel discharge. The characteristics of plasmas in the microhollow were investigated as well. The spectral line intensity and electron density of plasmas in microhollow increased obviously with the decease of the microhollow diameter.

Behavior of AISI SAE 1020 Steel Implanted by Titanium and Exposed to Bacteria Sulphate Deoxidizer

A hybrid technology to treat solid surfaces with the pulse high voltage and electric arc discharges of low pressure with a three-dimensional ion implantation technique (3DII) is applied. This technology is used to protect AISI SAE 1020 steel against a microbiological corrosion. The titanium ion implanted steel samples (coupons) are subjected to a medium of bacteria sulphate deoxidizer (BSD) which are very typical of the hydrocarbon industry and are potentially harmful for structures when are in contact with petroleum and some of its derivatives.The used technology aims to find an effective hybrid procedure to minimize the harmful effects of bacteria on AISI SAE 1020 steel. The hybrid technology efficiency of superficial titanium implantation is estimated through the measurements of the point corrosion characteristics obtained after testing both the treated and non-treated coupons. The three-dimensional surface structures of the samples are reconstructed with help of a confocal microscope.

Incipient Fault Location Algorithm for Underground Cables

Cable failure process is gradual and is characterized by a series of single-phase sub-cycle incipient faults with high arc voltage. They often go undetected and eventually result in a permanent fault. The objective of this paper is to develop a robust yet practical incipient fault location algorithm taking into account the fault arc voltage. The algorithm is implemented in the time-domain and utilizes power quality monitor data to estimate the distance to the fault in terms of the line impedance. It can be applied to locate both sub-cycle as well as permanent faults. The proposed algorithm is evaluated and proved out using field data collected from utility distribution circuits. The average absolute error in locating incipient faults for three underground cable failures analyzed in this paper was found to be 7.37%, 4.69% and 3.58%, respectively.

Droplet Transfer Analysis of Intermittent Pulsed Arc Welding Used to Repair the Metal Defects

Intermittent pulsed arc welding using micro heat control, it can be used to repair the defect of metal parts. But the droplet transfer mode is different from the general pulsed TIG. The image signals of intermittent pulsed droplet transfer are acquired using speed camera systems. Then, the characteristics of droplet transfer for intermittent pulsed arc welding were discussed. The results showed that in the Intermittent pulsed arc welding repair process, welding wire and substrate surface were melted by instantaneous high voltage arc and formed drop wise droplet. And with gravity and surface tension the droplet jitter, roll, and then cooled and solidified rapidly. The change of microstructure is continuous from the substrate to the droplet, showing a good metallurgical bonding.

High Energy Pulses Cold Patch Repair Droplet Transfer Analysis Based on High-Speed Camera

The image signal of intermittent high energy pulsed droplet transfer are acquired using high-speed camera systems and self-developed high-energy pulsed cold patch machine. Then, the droplet transfer characteristics in high-energy pulsed cold patch process were discussed. The results showed that in the high-energy pulsed cold patch repair process, welding wire and substrate surface were melted by instantaneous high voltage arc and dropwise droplet were formed. And the droplet jitter, roll by gravity and surface tension and then cooled and solidified rapidly, metallurgical fused at the end.

Fabrication of CNT Nano-Strands as a Schottky Transistor Platform

In this study, high voltage arc discharge technique is used for direct fabrication of carbon nanotube strands for schottky interconnects to study prototype carbon nanotube field effect transistors. The CNT samples are grown between graphite electrodes mounted on PCB templates in 5 mm gap using pure methane at different flow rate 0.2-1 standard litter per minute under atmospheric conditions. This report discusses the synthesis detail of nano-CNT strands, effect of electrical parameters of arc discharge and growth process. The structure of the grown carbon strands is explored in macro regime by high resolution optical microscope and also by scan electron microscopy technique for structural morphological analysis. The technique has a promising technology to grow unidirectional carbon nanomaterials which is employed on Schottky transistor fabrication.

Highly stable carbon nanotube field emitters on small metal tips against electrical arcing

Carbon nanotube (CNT) field emitters that exhibit extremely high stability against high-voltage arcing have been demonstrated. The CNT emitters were fabricated on a sharp copper tip substrate that produces a high electric field. A metal mixture composed of silver, copper, and indium micro- and nanoparticles was used as a binder to attach CNTs to the substrate. Due to the strong adhesion of the metal mixture, CNTs were not detached from the substrate even after many intense arcing events. Through electrical conditioning of the as-prepared CNT emitters, vertically standing CNTs with almost the same heights were formed on the substrate surface and most of loosely bound impurities were removed from the substrate. Consequently, no arcing was observed during the normal operation of the CNT emitters and the emission current remained constant even after intentionally inducing arcing at current densities up to 70 mA/cm2.

An investigation on stability of laser hybrid arc welding

The stability of the weld surface quality resulting from laser–arc hybrid welding of 4mm thick steel was studied. The trends of stability in terms of top weld width variation were estimated by using design of experiments, where different types of unstable welds were distinguished. High speed imaging of the process supported the interpretation of the trends. High arc voltage and short distance laser–arc has destabilized the process. For a stable process the applied spray mode has caused a short arc and symmetric central drop transfer while for high voltage the arc became long and wide and the drops traveled sideward. The potential and limits of the design of experiments method for such kinds of applications were discussed.

Pyrrole conversion induced pulse discharge plasma over a water surface under high-pressure argon

Electric field generated by pulsed high-voltage discharge plasma over water surface has been performed under high-pressure argon environments to oligomerize pyrrole compound. In this preliminary study, oligomerization of pyrrole in water as a reaction media and the effects of various parameters with pulsed high-voltage arc discharge plasma are studied. Such as plasma applied under hydrothermal conditions generates high-energy electrons, ions, and radicals, which in turn may generate new reaction fields, leading to effective organic compounds oxidation for both homogeneous and heterogeneous reactions. Here, we utilize pulse discharge plasma over water surface to study the removal characteristics for pyrrole into more valuable higher amines group which has been fascinating for both the industry and the scientific community. The experiments were conducted at 313K and 1–2MPa using a batch type reactor. Intermediate compounds from the conversion of pyrrole in the aqueous products were identified by UV–vis (ultra violet–visible) spectrophotometer and quantified using high performance liquid chromatography (HPLC). The maximum pyrrole conversion was 24.40% with a discharge plasma pressure of 2MPa with 10,000×. It was found that pyrrole conversion can be raised considerably by increasing reaction pressure and discharge plasma amount.

Ultra-high voltage capillary electrophoresis >300 kV: Recent advances in instrumentation and analyte detection

Instrumentation has been developed for the implementation of ultra-high voltage capillary electrophoresis (UHVCE) with potentials up to and exceeding 300kV. Several separations have been used to demonstrate the utility of higher applied voltages for improving the resolution of peptide, protein, and nucleic acid separations. Previously reported instrumentation was limited to 120kV and required submersion in a bath of transformer oil to prevent corona and high voltage arcing between the components of the instrument [Hutterer, 1999, 2000, 2005] [1–3]. A modular design that uses plastic dielectric materials to overcome these obstacles enabling simplified operation of the instrument in air is described here in detail. A forced air system developed to control the temperature of the instrument to within a few degrees over a range of 25–60°C for use with ultra-high voltage capillary gel electrophoresis is also described. UHVCE instrumentation and its applications with UV absorption and laser induced fluorescence detection are further developed, and the first demonstration of UHVCE coupled to electrospray ionization-mass spectrometry is shown.

Plasma temperature measurement in a hybrid discharge by using optical diagnostics

Of the plasma methods used to improve the tribological properties of the solid surface [1-3], the treatment of metal pieces in the hybrid discharge, which is a combination of high voltage and electric arc discharges, seems very promising [4,5]. This method is developed in the Plasma Physics and Technology Laboratory at the Universidad Industrial de Santander (Colombia). In our work, the hybrid discharge is ignited in tungsten vapor. The plasma temperature and atomic composition of the discharge are measured through its optical spectrum.

TIG-MIG複合溶接法の基礎的検討

TIG and MIG welding are most popular gas shielded arc welding processes used on many industrial fields. MIG welding is high efficiency process compared to TIG welding, however it is needed to improve the quality about spatter and weld metal toughness for advanced GMA process. Although pure Ar shielding gas is desirable for weld metal toughness, MIG arc is unstable in pure Ar shielded condition due to the irregularly behavior of cathode spot on plate surface and suitable welding execution is difficult. We found that MIG arc becomes stable even though in pure Ar shielded condition by simple hybridization of TIG and MIG. Therefore, this process has high possibility as new type of high quality and high efficiency welding process. In this study, we investigated the influence of hybridization condition such as TIG-MIG current balance, distance between the both arcs and torch angles on stabilization of the process and confirmed the suitable range of the condition. The main results are as follows: (1) TIG current is needed to be larger than MIG current for stabilization of MIG arc. (2) According to increase of the distance between the both arcs, MIG arc shows high arc voltage and becomes unstable. (3) On the condition of small angle between the both torches, as thirty degree, MIG arc is deflected toward back by repulsion with TIG arc and bead shape becomes convex.

Analysis of meso-scale damage and crack for CuW alloys induced by thermal shock

Abstract Considering the mismatch of coefficient of thermal expansion (CTE) of Cu and W phase and temperature gradient, internal and external thermal load are applied on meso-scale 2D representative volume element (RVE) of CuW alloys under thermal shock, respectively. Void volume fraction (VVF) and VVF induced crack are determined by finite element method (FEM) utilizing Gurson–Tvergaard–Needleman (GTN) model, and the driving forces for damage nucleation and growth are analyzed with normal and shear stress as well. The simulation results show that damage and damage induced crack initiate from the vertex of W grain and grow along W/Cu interface, then propagate into Cu phase. After thermal shock experiment on CuW specimen by high voltage arc, micro cracks present along W/Cu interfaces and inside Cu phase, which is in good agreement with simulation results.

Three-Dimensional Unsteady MHD Modeling of a Low-Current High-Voltage Nontransferred DC Plasma Torch Operating With Air

We present, in this paper, the MHD modeling of a dc plasma torch operating with air under very peculiar high-voltage low-current conditions. The model developed is 3-D, is time dependent, and assumes local thermodynamic equilibrium (LTE). The study has been carried out considering an axial injection of air with flow rates varying in the range of 0.16-0.5 g/s and currents varying in the range of 300-600 mA. The numerical modeling has been developed using Code_Saturne, a computational fluid dynamics software developed by EDF R&D which is based on colocated finite volume. After a detailed description of the model, the results are presented, analyzed, and discussed. The influence of current and that of air flow rate over the arc characteristics are studied in terms of temperature, velocity, electrical potential, Joule heating, and arc root motion. Regarding numerical issues, the MHD modeling of low-current high-voltage arc discharge is particularly tricky since, below 1 A, the self-induced magnetic field becomes negligible and the convection effects induce a highly irregular and unstable motion of the arc column. However, despite these difficulties, the numerical model has been successfully implemented. Numerical results have shown good correlation and good trends with experimental ones despite a discrepancy which is probably due to the LTE assumption. The model gave fruitful and significant information on parameters that could hardly be obtained experimentally. This preliminary work is likely to open the way toward a better understanding of low-current arc discharges, which technologies are currently encountering an important development in many application fields.