Basic Electrodes Research Articles

Revealing Bipolar Photoresponse in Multiheterostructured WTe2-GaTe/ReSe2-WTe2 P-N Diode by Hybrid 2D Contact Engineering.

The van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been thoroughly investigated with regard to practical applications. Recent studies on 2D materials have reignited attraction in the p-n junction, with promising potential for applications in both electronics and optoelectronics. 2D materials provide exceptional band structural diversity in p-n junction devices, which is rare in regular bulk semiconductors. In this article, we demonstrate a p-n diode based on multiheterostructure configuration, WTe2-GaTe-ReSe2-WTe2, where WTe2 acts as heterocontact with GaTe/ReSe2 junction. Our devices with heterocontacts of WTe2 showed excellent performance in electronic and optoelectronic characteristics as compared to contacts with basic metal electrodes. However, the highest rectification ratio was achieved up to ∼2.09 × 106 with the lowest ideality factor of ∼1.23. Moreover, the maximum change in photocurrent (Iph) is measured around 312 nA at Vds = 0.5 V. The device showed a high responsivity (R) of 4.7 × 104 m·AW-1, maximum external quantum efficiency (EQE) of 2.49 × 104 (%), and detectivity (D*) of 2.1 × 1011 Jones at wavelength λ = 220 nm. Further, we revealed the bipolar photoresponse mechanisms in WTe2-GaTe-ReSe2-WTe2 devices due to band alignment at the interface, which can be modified by applying different gate voltages. Hence, our promising results render heterocontact engineering of the GaTe-ReSe2 heterostructured diode as an excellent candidate for next-generation optoelectronic logic and neuromorphic computing.

Оценка сварочно-технологических свойств электродных покрытий основного типа различных производителей электродов для сварки трубных деталей и сборочных единиц поверхностей теплообмена котлоагрегатов

Introduction. New grades of high-strength steels, machining and repair processes are being introduced in the power industry. At the same time manual arc welding remains the main technological process for equipment repair in conditions of thermal power plants. Welding materials used in equipment repair should provide comparable to the base metal mechanical properties of the weld. The welding industry has long faced the problem of high sensitivity of basic type electrodes to moisture absorption. High susceptibility to cold cracking caused by diffusible hydrogen and hydrogen embrittlement are major obstacles to the wider use of basic-type electrodes for high-strength steels. Hydrogen production during arc welding is the result of the presence of hydrogen in the arc atmosphere, hydrogen-contaminated filler material, or local hydrogen residues on the source material. During welding, molecular hydrogen is dislocated by the arc energy and then easily absorbed by the molten material. Currently, the welding materials market produces electrodes with basic coating of well-known and proven brands, various national and foreign manufacturers. However, in practice there are cases of cold cracks in the weld seam after welding. Purpose of work is to assess the welding and technological properties of basic type electrode coatings of different manufacturers. The work investigates specimens weld overlaid with electrodes TMU-21U, TSU-5 of different manufacturers and the content of diffusion-mobile hydrogen in the weld overlaid metal is determined. The methods of research are mechanical static tensile tests, chemical composition analysis and metallographic studies. Determination of welding-induced hydrogen content can be accomplished by various quantitative elemental analysis methods. All test methods involve welding under defined conditions followed by deep freezing of the test specimens as quickly as possible. In this way, unintended diffusion processes are inhibited and the hydrogen introduced into the weld metal is retained. Subsequently, the diffusing hydrogen is desorbed from the test specimens in a controlled manner. Results and Discussion. An assessment of welding engineering properties of the electrodes revealed unstable arc burning. Mechanical properties of the welded metal of the investigated electrodes are at the minimum permissible level from the requirements of normative documents. The concentration of hydrogen present in the arc weld metal is multifactorially dependent on the welding procedure (process and parameters, consumables used, as well as environmental conditions (e.g. humidity). For qualitative assessment, hydrogen content of more than 15 cm3/100 g is considered high and hydrogen content less than 5 cm3 ml/100 g is considered very low. Presented results. The conducted evaluation of welding engineering properties of electrodes with basic coating showed satisfactory results. Mechanical properties of the welded metal in terms of impact toughness are at the lower permissible limit, relative elongation does not meet the requirements of normative documents. The content of diffusion-mobile hydrogen in the welded metal is higher than the declared indicators by the electrode manufacturers.

Nanosilica treatment enables moisture-resistant hydrophobic arc welding covered electrodes

Controlling the moisture content of the electrode-covering is crucial in the production of defect-free, high-quality welds during shielded metal arc welding of steels. The welding industry has long faced the challenge of the high susceptibility of basic electrodes (e.g., E7018) to moisture absorption. In this paper, we demonstrate that applying a nanosilica coating to the surface of the E7018 electrode-covering using a dip-coating technique can effectively reduce the moisture absorption capability of the electrode-covering. The moisture measurement results before and after exposure to a moist environment of 80% humidity and a temperature of 27 °C for 9 h indicate that the moisture absorption values of conventional and nano-treated E7018 electrodes during exposure are 0.67 wt% and 0.03 wt%, respectively. While reducing the size of the pores on the surface of the electrode-covering can to some extent enhance the resistance to moisture absorption, it has been identified that turning the wetting behavior of the electrode-covering surface from hydrophilic to hydrophobic by the nanosilica coating is the most effective mechanism that contributes to the enhanced moisture absorption resistance of the nanosilica-treated electrode-covering. The results indicate that this approach does not have any deleterious effects on the chemical analysis and tensile properties of the weld metal. This simple modification to the electrode-covering can be generally applied to a wide range of electrode-covering types to produce hydrophobic, moisture-resistant electrodes.

Influence of contact resistance and heat leakage in the determination of the dimensionless figure of merit via duo-impedance spectroscopy

The influence of contact resistance between a polycrystalline bismuth as a basic thermoelectric material and electrodes made of copper using binders of Ag epoxy and conventional solder was investigated to estimate the dimensionless figure of merit (zT) via impedance spectroscopy (IS). The frequency dependence of the impedance using both binders was measured at 300 K under an appropriate alternating current because a considerably larger Peltier heat was required, relative to Joule heat, for estimating the zT precisely. Through the duo-IS method, zT at 300 K was estimated to be 0.126 ± 0.004 and 0.130 ± 0.002 using the Ag epoxy and solder, respectively. The temperature dependence of zT from 300 to 30 K was also estimated, and zT > 0.01 was a practical based on this technique, owing to its signal–noise ratio. The duo-IS method is invaluable for estimating zT in the entire temperature region based on an appropriate configuration.

Development of Coated Electrodes with Solid Wire and Flux-Cored Alloyed Wire for Microalloyed Steel Welding.

In this paper, we will present our investigation of the quality of J55 microalloyed steel welds that were formed by a basic flux-cored wire electrodes that were of appropriate quality and alloyed with Ni and Mo. Based on the comparison and analysis of the obtained results related to the testing of the chemical composition, mechanical properties, toughness at test temperatures, and the microstructure of welding joints formed by a classic and specially coated rutile flux-cored electrode, we assessed the justification to switch from solid wire electrodes to flux-cored alloyed wire electrodes of appropriate quality. The research aim for the application of flux-cored wire electrodes instead of solid wire electrodes is based on the advantages pertaining to a flux-cored wire: molten metal from electrode wire is transferred in the form of fine droplets, easy welding and maximum productivity within all spatial positions related to welding, improved properties of welding joints, and increased productivity when compared to a classic solid wire. Our research encompasses the development of the experimental production at the Research and Development Center IHIS Belgrade (Development Institute for Chemical Power Sources), Serbia, of the new type of a coated electrode with improved welding properties when compared to a classic electrode intended for microalloyed steel welding.

Basic magnesium-doped nickel-based electrodes with card-on-lawn structure for supercapacitor with high energy density

The rapid development of electrical energy storage (EES) technology is urgent for the exploitation of the supercapacitors with high energy density. The electrode plays a crucial role in the performance of supercapacitor. In this research, a basic magnesium-doped nickel-based (BMDNB) electrode material is successfully synthesized on a foamed nickel substrate by one-step hydrothermal method. After optimizing synthesis condition, the material has a unique card-on-lawn structure, nanocards are grown on a uniform honeycomb lawn array. The unique structure and compositions endow BMDNB prominent morphological features and excellent electrochemical properties. Using the BMDNB and active carbon as electrodes, an asymmetric supercapacitor (BMDNB//AC ASC) is assembled with a voltage window of 1.8 V. The ASC device achieves a maximum energy density of 74.9 Wh∙kg−1 at a power density of 1086.8 W∙kg−1. The energy density is comparable with the state-of-the-art level of the reported Ni(Mg)-based supercapacitors.

Comparison of underwater wet welding performed with silicate and polymer agglomerated electrodes

Conventional basic electrodes varnished and basic electrodes agglomerated with polymer in underwater wet welding in a simulated depth of 10 m were compared. A hyperbaric tank was used for depth simulation and a gravity welding device for making the bead on plate welds. Bead on plate welds were deposited with welding currents of 100, 120, 140, 160 and 180 A with DCEN and DCEP polarities, in order to evaluate the arc stability through a non-dimensional statistical index. The welding current which showed better stability level in both polarities was chosen to evaluate weld bead morphology, weld metal porosity, weld metal oxygen and diffusible hydrogen levels. A methodology was used to correlate the heat input and short-circuit frequency with the weld bead morphology. It was observed a direct relation with the weld metal oxygen and penetration and an inverse relation of the weld metal oxygen with the diffusible hydrogen. Electrodes agglomerated with polymer showed higher penetration values than conventional electrodes in both polarities and lowest diffusible hydrogen levels in the DCEP polarity. It was observed lower levels of weld metal porosity for the electrodes agglomerated with polymer in comparison to conventional electrodes. This result was related to lower levels of porosity found in the droplets formed at the tip of the electrodes agglomerated with polymer.

AN APPROXIMATE CALCULATION OF ENERGY DISSIPATION AND ELECTRIC EROSION OF ELECTRODES IN THE HIGH-VOLTAGE HIGH-CURRENT AIR SWITCH OF ATMOSPHERIC PRESSURE

Purpose. To obtain new calculation correlations, determining approximate energy dissipation and electric erosion of massive basic metallic electrodes in the high-voltage high-current air switchboard (HVCAS) of atmospheric pressure, in-use in the bit chain of the high-voltage electrophysics setting (HVES) with the powerful capacity store of energy (CSE). Methodology. Electrophysics bases of technique of high-voltage and large impulsive currents (LIC), scientific and technical bases of development and planning of high-voltage heavy-current impulsive electro-devices, including HVES and powerful CSE, and also methods of measuring in their bit chains of LIC of the microsecond temporal range. Results. On the basis of new engineering approach the results of calculation estimation of excretions energy and electric erosion of massive basic metallic electrodes are resulted in probed HVCAS. New correlations are obtained for the approximate calculation of thermal energy, selected in an impulsive air spark and on the workings surfaces of anode and cathode of HVCAS. It is entered and a new electrophysics concept, touching equivalent active resistance of impulsive air spark, is mathematically certain. New formulas are obtained for the approximate calculation of most depth of single round crater of destruction on the workings surfaces of basic metallic electrodes of HVCAS, and also mass of metal, thrown out magnetic pressure from this crater of destruction on the electrodes of switch for one electric discharge through them powerful CSE HVES. It is shown that the radius of the indicated single crater of destruction is approximately equal to the maximal radius of plasma channel of a spark discharge between a cathode and anode of HVCAS. The executed high-current experiments in the bit chain of HVES with powerful CSE validated row of the got and in-use calculation correlations for the estimation of energy dissipation and electric erosion of metallic electrodes in examined HVCAS. Originality. New engineering approach is developed for the approximate calculation and estimation of energy dissipation and electric erosion of basic metallic electrodes in HVCAS. A formula is firstly got for approximate calculation unchanging in the process of swaying or aperiodic discharge of CSE HVES on the electric loading of active resistance of impulsive air spark between the electrodes of probed HVCAS. Practical value. Drawing on the got results in a high-voltage impulsive technique provides operative implementation of calculation of balance of electric energy in the high-current circuit of HVES with powerful CSE and point electric load, and also prognostication of the technical state of workings surfaces of massive basic metallic electrodes of HVCAS.

Comparison of the performance of silicone and glass barriers under direct current and very severe conditions of pollution

The main objective of this paper consists in the comparison of the performance in DC voltage of a short air gap with non-uniform electrical field protected by silicone or glass barriers under very severe conditions of pollution. The choice of the investigation system is related to the rod and plane electrodes. The essential influence parameters on the performance of the system are summarized in the severity of the level of pollution of the barrier and the orientation of the axis of the basic electrodes of the system. These tests were supported by a visualization of the breakdown path followed by the electrical discharge on the barrier. An experimental device allowing simultaneously the orientation of the axis of the electrodes and the displacement of the barrier inside the air gap was made. The results show that under pollution conditions, the effective electrical protection offered by the silicone barrier is highly efficient than the glass one. Under the effect of the contaminated water droplets, the system with vertical or horizontal silicone barrier, floating above the energized rod is more rigid than when this silicone barrier is horizontal, and located below the energized electrode. The quantification of the voltages decrease is made possible by a mathematical model.

Stretchable electronic skin based on silver nanowire composite fiber electrodes for sensing pressure, proximity, and multidirectional strain.

Electronic skin (E-skin) has been attracting great research interest and effort due to its potential applications in wearable health monitoring, smart prosthetics, robot skins and so on. To expand its applications, two key challenges lie in the realization of device stretchability, and independent sensing of pressure and multidirectional lateral strain. Here we made a combination of rational device structure and artfully engineered sensing materials to fulfill the mentioned demands. The as-prepared E-skin took a simple orthogonal configuration to enable both capacitive mode for pressure sensing and resistive mode for multidirectional strain sensing, independently. Pre-cracked silver nanowire based fibers with helical microstructures were utilized as basic electrodes to endow the E-skin with intrinsic stretchability and strain sensing capability. Through dielectric layer optimization, the pressure sensing sensitivity was greatly enhanced, with a detection limit of 1.5 Pa. For application demonstrations, we utilized the E-skin as both flat and curved platforms for pressure mapping, and also as human motion sensors, such as palm and thumb bending.

Welding with Microjet Cooling as a Method of Improving the Plastic Properties of Welds

The goal of this paper is to provide a new welding technology based on microjet cooling just after the welding and to investigate the possibilities of improving the plastic properties of welds. This is possible because in this case the welds have a beneficial structure with a high amount of acicular ferrite (AF) in a weld metal deposit (WMD). A very high percentage of AF in the WMD (55–75%) cannot be obtained by an ordinary welding method (basic electrodes, MIG/MAG (Metal Inert/Active Gas), and TIG (Tungsten Inert Gas)). Welding with microjet cooling is very promising and capable of industrial application, mainly due to the significant improvement of weld quality and reduction of costs.

DIFFUSIBLE HYDROGEN CONTENT IN DEPOSITED METAL OF MULTILAYER WELDED JOINTS

The article describes manufacturing technology of multilayer joints in terms of control the diffusible hydrogen content. Diffusible hydrogen content in deposited metal for multilayer welded joints made of covered rutile electrodes or covered cellulosic and basic electrodes was determined. It was found that after four beads, the diffusible hydrogen content decreases in the case of the first technology from 36 ml/100 g to 18 ml/100 g while in the second of about 40 ml/100 g to a level of 12 ml/100 g. The explanation of the mechanisms responsible for this phenomenon and directions for further study were proposed.

Application of hard surfacing for repairing of agricultural parts

The contribution deals with the analysis of claddings quality realised by shielded metal arc welding with covered electrodes. For cladding, covered basic electrodes marked as E Z Fe 8 EN 14700 and E Z Fe 15 EN 14700 were used. The third type of electrode was experimentally made basic electrode with operating name EW11 (wolfram content 11%). New share made of C50R EN10083/1-98 was used as reference material. Quality of repairing deposits was evaluated by micro hardness measuring and by metallographic analysis of claddings and base material. Wear resistance of claddings was determined by weight loss during abrasive wear test by wading in following loose abrasive agents – Al<sub>2</sub>O<sub>3</sub> (corundum), crushed rock and arable soil.  

An Effective Semianalytical Method for Simulating Grounding Grids

The analytical study of grounding systems is only possible for basic electrodes, i.e., hemispherical and spherical electrodes, rods, and horizontal wires. However, it is normal practice to employ more complex earthing systems, such as grounding grids integrated with rods, in order to obtain lower resistances to ground and improve the electrical safety of substations. This paper introduces a semianalytical (or seminumerical) method, consisting of an analytical approach integrated with a numerical solution, to study grounding grids of complex geometry and their effects on non stratified soils. The algorithm that was created and realized with MATLAB allows the determination of all the quantities of interest for the design and the analysis of such grounding systems, i.e., ground resistance, ground potentials, and distribution of the ground-fault current along the grid's components (i.e., horizontal wires and rods). The model is based on the assumption that conductors forming grids have very small radii if compared with their lengths and that the wires can be considered equipotential cylindrical elements. A verification of the proposed algorithm through a finite-element method has been also carried out to confirm the validity of the results. Exemplary calculations of the ground resistance of grids are included in this paper.

Hot Extraction of Diffusible Hydrogen and Its Measurement Using a Hydrogen Sensor

Diffusible hydrogen measurement in welding consumables using a Nafion®117-based Proton Exchange Membrane Hydrogen Sensor (PEMHS) has been carried out successfully at room temperature. The same sensor has now been used for measuring diffusible hydrogen by the hot extraction method. With this objective, a chamber for hot extraction of diffusible hydrogen was designed and fabricated which could be heated to a maximum temperature of 500 °C, while the chamber itself is maintained at ambient temperature by water cooling. The chamber has an inlet and an outlet for argon purging and pressurization. For this measurement, weld specimens were prepared based on ISO 3690, the standard method for diffusible hydrogen measurement, by depositing cellulose, rutile and basic coated welding electrodes (having diffusible hydrogen content ranging between 3 and 31 ml/100 g of deposited metal) on standard mild steel specimen by manual metal arc welding. After preparing the weld specimen, it was transferred to the hot extraction chamber. The chamber was subsequently flushed and filled with argon to a known pressure level and then heated at 400 °C for 30 min for the collection of hydrogen. The concentration of hydrogen in the chamber was measured using the sensor. From the volume of the chamber, the pressure of the gas inside and the mass of the weld metal, the diffusible hydrogen content in the deposits was estimated. Measurements were also repeated using the standard Mercury Method. One-to-one correlation between these two different methods of measurement was obtained. The statistical accuracy of the results obtained with the new Hot Extraction-PEMHS Method was re-confirmed by the t-Test. Further, the hydrogen content obtained with this new method was also compared with the hydrogen content obtained by Thermal Conductivity Detector (TCD)-based Hot Extraction Method (HMAT 2500 Analyzer). This paper presents the development of the system for hot extraction of diffusible hydrogen and its subsequent measurement using the sensor, the results obtained and the possible application of the systems for studying hydrogen evolution from the weld samples.

Diffusible Hydrogen Measurement in Steel Welds Using an Electrochemical Hydrogen Sensor

Diffusible hydrogen (H D ) measurement in steel welding consumables having cellulose, rutile and basic coating has been carried out using a Proton Exchange Membrane Based Hydrogen Sensor (PEMHS). The sensor is an electrochemical fuel cell based device which uses Nafion@117 as proton exchange membrane electrolyte. This can detect hydrogen in an Ar+H 2 mixture with detectable limit of 1 ppm. Further, HD measurements have also been carried out on basic coated electrodes of modified 9Cr-1Mo steel, with very low levels of H D content. Results obtained have been compared with those obtained from H D measurement using mercury manometer as per standard ISO 3690. One to one correlation has been obtained between these two different methods of measurements. This sensor has shown good sensitivity, accuracy and precision hence is reliable for H D measurement. In addition to the above measurement, this method was used to study hydrogen evolution from the weldments as a function of time. The paper presents and discusses the principles of H D measurement using this sensor, its applications for H D measurements in weldment, the results obtained, its application to study the hydrogen evolution from weldment as a function of time and the possibility of using this sensor for measurement of hydrogen evolved from the weld specimens at high temperatures.

제초제 검출을 위한 전기화학적 일회용 면역센서

A disposable electrochemical immunosensor system has been developed for the detection of herbicide in aqueous samples. Disposable screen printed carbon electrodes(SPCE) were used as basic electrodes and an enzyme, horseradish peroxidase (HRP), and anti-herbicide antibodies was immobilised on to the working electrode of SPCE by using avidin-biotin coupling reactions. An herbicide-glucose oxidase conjugates have been used for the competitive immunoreaction with sample herbicides. The enzymatic reaction between the conjugated glucose oxidase and glucose added generates hydrogen peroxide, which was reduced by the peroxidase immobilised. The latter process caused an electrical current change, due to direct re-reduction of peroxidase by a direct electron transfer mechanism, which was measured to determine the herbicides in the sample. The optimal operational condition was found to be: <TEX>$20\;{\mu}gl-1$</TEX> deglycosylated avidin loading to the working electrode and working potential +50 mV vs. Ag/AgCl. The total assay time was 15 min after sample addition. The detection limits for herbicides, atrazine and simazine, were found to be 3 ppb and 10 ppb, respectively.

Spectral Features and Parameters of Some 1H-Pyrazolo[3,4-b]quinoxaline Derivative Dye Chromophores

ABSTRACT The role of ground state dipole moments of a dye chromophore on the principal features of the light-emitting diodes in the single-layered architecture ITO/PEDOT:PSS/pyrazoloquinoxaline (PQX):PVK/Ca/Al is explored for the first time. The ground state dipole moments of a chromophore determine excitonic carrier kinetics and their annihilation. It was established that the pyrazoloquinoxaline dye chromophores possessing lower dipole moments substantially favor larger electroluminescent efficiency. Parameters of the electroluminescence and current–voltage features are compared with the photoluminescence and absorption characteristics. The UV-Vis spectral absorption, photoluminescence, and current–voltage dependencies indicate a principal possibility to operate by charge kinetics at the almost fixed values of the Highest Occupied Molecular (HOMO) energy levels with respect to the basic ITO hole injector electrodes. Also, a separate role may be played by polaronic effects. We have shown a principal possibility to tune carrier kinetics.

Fluoride exposure and respiratory symptoms in welders.

Welders inhale gases and respirable particles. To investigate the relationship between fluoride exposure and respiratory symptoms in welders using basic electrodes containing calcium fluoride, 63 railroad track welders were interviewed. Fluoride was measured in post-shift urine samples. Seventeen welders reported respiratory symptoms related to welding fume exposures. Respiratory symptoms were somewhat more common with increasing concentrations of fluoride in urine. The association between welding fume exposure and respiratory symptoms seems related more to fluorides than to other particles among welders using basic electrodes.

Plasticising and stabilising components in coatings of basic electrodes

Plasticising and stabilising components in coatings of basic electrodes