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In this study, we investigated the effect of pulse current on the microstructure, texture, deformation behavior, and mechanical properties of Ti-6Al-4 V alloys fabricated by electrically assisted stationary friction stirring welding. With the increase of the rotation speed and peak pulse current, a lamellar structure precipitated in the stir zone became more elongated, resulting in a higher concentration of grain orientation distribution and a larger but gradually decreasing ratio of high-angle grain boundaries. Moreover, the texture strength increased, but still remained lower than that of the transition zone on both sides. The microhardness distribution of the welded joint was anisotropic in all layers, with the stir zone exhibiting the highest hardness, while the HAZ was identified as the weakest region. The joints have a maximum tensile strength of 1020.1 MPa and an elongation of 6%, respectively. The tensile strength is comparable to that of the base metal (BM), and the elongation reaches 57.7% of BM. This improvement is mainly attributed to grain refinement and uniformly distributed hardness. Furthermore, all tensile fractures were ductile fractures. [ABSTRACT FROM AUTHOR]

Laser-directed energy deposition (LDED) has the advantages of high material utilization, high degrees of freedom and high forming efficiency; consequently, it is applied widely in surface enhancement and repair of damaged parts. There are, however, some defects in the deposition process such as cracks and pores. The assistance of the external energy field is an effective measure to reduce such defects. To study this we deposited a single track clad of Inconel 625 onto the surface of HT300 grey cast iron by laser-directed energy deposition (LDED) with electromagnetic compound field (EMCF) assistance. The geometrical characteristics, microstructure and microhardness of the clad were determined to investigate the influence of the EMCF. The results show that: under the action of the EMCF with high magnetic field strength and high pulse current strength, the geometrical characteristic of the clad changed markedly. The application of the EMCF led to an increase in clad depth and a decrease in clad height, which led to an increase in dilution rate. The geometrical characteristic did not change significantly when the EMCF was small. The application of the EMCF can inhibit the growth of dendrites crystals, facilitates fine grain formation and improves the uniformity of microstructure. The microhardness improved and the range of microhardness decreased significantly under the condition of the EMCF. [ABSTRACT FROM AUTHOR]

In order to study the anisotropy mechanism and the effect of current mode on the anisotropy, the arc additive manufacturing experiment of 316L stainless steel was completed by using direct current and pulse current, respectively. The results of microstructure analysis show that each layer of the additive wall can be divided in the longitudinal direction into a heat-affected zone, a central zone and a remelting zone. The grain growth direction of each zone was basically the same, and the microstructure, alloying element content and hardness of the three zones were obviously different. The crystallographic texture and inhomogeneity of the layer were the main reasons for the anisotropy. Compared with the use of direct current, the difference in tensile strength between horizontal and vertical specimens was reduced by 23.5% when using pulse current. Additionally, the wall has high forming accuracy, small grain size and good plasticity. And the δ-ferrite content inside the layer is lower, the hardness of each zone is higher, and the hardness difference between the three zones is smaller. [ABSTRACT FROM AUTHOR]

SiC/Al composites are widely used in aerospace and other fields due to their excellent mechanical properties. For large-concentration composites, due to the extremely high proportion of SiC and the unstable interface between the two phases, the SiC particles are broken and detached during the processing, which makes the surface quality of the workpiece insufficient to meet the service requirements. Electrically assisted cutting technology is expected to break through this technical bottleneck. This paper investigates the surface quality of high-concentration SiC/Al grinding with electroassisted biolubricant MQL. The surface morphology after processing is observed. Firstly, by comparing the traditional grinding and electrically assisted grinding conditions, it is found that the fundamental reason for the improvement in the grinding surface quality using a pulse current is the improvement in the Al plasticity. Secondly, based on the thermal effect and non-thermal effect of the pulse current, the influence of the electrical parameters (current, duty cycle and frequency) on the machining indication quality is discussed. It is found that when the current and duty cycle increase, the machining surface quality will also increase, while the frequency change has little effect on the surface quality. Finally, friction and wear experiments are carried out on the grinding surface under different working conditions to explore the friction and wear characteristics of the surface of the workpiece. The results show that the pulse current can significantly improve the wear resistance of the grinding surface. [ABSTRACT FROM AUTHOR]

Energy efficiency is an important issue in industry, especially with the ever-increasing consumption of electrical energy. The power quality and the traceability of metering devices are essential when integrating energy metering systems for energy efficiency. This management requires an understanding of electrical current events such as pulse and transient currents. Current transducers are widely used to measure these electrical current events up to a few megahertz. Their use makes it possible to measure not only the main current flowing through the transducer, but also the bypass current that affects electrical equipment. Calibration of these sensors up to a few megahertz then becomes an essential step. Currently, most calibration methods are limited to 100 kHz frequency for a current of 10 A. This paper presents an improvement of a traceable calibration methodology for current transducers up to 10 A and 1 MHz, thus increasing, by 10 times, the current level for such high frequency applications. This calibration methodology is based on a metrological traceability chain (uninterrupted link to the International System of Units) with respect to a calculable current shunt and is currently the only traceable method for calibrating current transducers at 10 A and up to 1 MHz. The uncertainty obtained for the transimpedance ratio is less than 0.2%, which is considerably reduced with respect to the existing capabilities. [ABSTRACT FROM AUTHOR]

At present, in the process of weld induction heat treatment, the common method is to carry out centralized induction heating in the weld area, which will lead to large radial temperature difference of the weld, poor controllability of temperature distribution and easy to cause the defects of residual stress concentration in the weld area. To solve the above problems, this paper adopts the two-sided method to conduct induction heating on both sides of the weld, and at the same time, the auxiliary pulse current is passed into the weld to improve the quality of the weld. ANSYS finite element software is used to establish a multi-field coupling prediction model of electric-magnetic-thermal structure, and explore the distribution law of the auxiliary pulse current and the temperature field of the weld. Finally, an experimental study of pulsed current assisted two-sided induction heating is carried out. Temperature test and metallographic test were carried out respectively to verify the effectiveness of pulsed current assisted induction heating technology.

Electrochemical deposition of CaCO3 is one of the methods to reduce scaling in industrial water system. The pulse current（PC） and direct current（DC） were used to study the electrodeposition process of CaCO3，and the influence of different ions on PC electrodeposition of CaCO3. The crystal morphology of CaCO3 were characterized by SEM and XRD. The experimental results showed that the nucleation rate of CaCO3 on 304SS electrode under PC is faster than that under DC，which promoted the ripening process of calcium carbonate. The addition of Fe3+，PO43-，SiO32- and Mg2+ accelerated the crystallization of CaCO3，but decreased the density and thickness of the deposition. The ripening process of PC electrodeposition makes the crystallization tend to form layered calcite with larger particle size，and the calcite particle size is larger than that obtained by DC electrodeposition.

A study was conducted on the influence of current, spacing, current mode, and arc length on the formation of adjacent weld overlays in the 316L stainless steel block melting process using an extremely inert gas-shielded arc additive manufacturing method. The main defect observed during the formation of adjacent weld overlays was the incomplete fusion at the bottom. When using direct current, low current and short arc length could ensure the flatness of the overlay surface, and the fusion at the bottom of the adjacent weld overlays was improved, but the problem of incomplete fusion remained unresolved. When using pulse current, low current, short arc length, and continuous welding method could solve the problem of bottom fusion of adjacent weld overlays. Due to the thermal influence during the accumulation of adjacent weld overlays, the microstructure inside the weld overlay was uneven, and the crystallographic texture in the entire weld overlay was not formed. With a pulse current of 80 A, adjacent weld overlay spacing of 4.5 mm, travel speed of 200 mm/min, dry elongation of 10 mm, and arc length of 2 mm, the tensile strengths of the block in the X, Y, and Z directions were 568.5, 570.3, and 550.7 MPa, respectively, and the fracture elongations were 46%, 48%, and 43.3%, respectively. The strength and plasticity in the Z-direction were lower than those in the X and Y directions. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The wound healing process is considered one of the most important elements of progress in the health and medical reality alike, because it has a direct impact on the patient's life, especially those who suffer from chronic diseases such as diabetes mellitus and others. All over the world, especially in developing countries, many people are exposed to afflictions due to the lack of ability to heal wounds or the delay in their recovery. The healing of wounds is always attributed to the ability of the affected skin to produce an electric current that helps the migration of stem cells and platelets to the place of extraction for the sake of healing, this is why electrical stimulation ES devices played an important role in the process of stimulation and wound treatment through using the high voltage pulsed current HVPC, low voltage pulsed current LVPC, direct current DC or pulse current PC. In this study, we review some of the important works that touched on this field in terms of the aim of their studies and the outcome that was reached, and the results were extracted. We also discuss the problems that faced researchers, especially those problems that Their studies miss it. [ABSTRACT FROM AUTHOR]

Abstract Silicon carbide (SiC) PiN diode has shown substantial promise as the freewheel diode for switch protection in a pulsed system. In this paper, we investigate the carrier lifetime (τ) modulation on pulsed current capability of SiC PiN diodes. The carrier lifetime in 4H–SiC is modulated by the generation of the Z 1/2 center through neutron irradiation. Surprisingly, we found that the pulsed current of SiC PiN diodes shows a limited improvement when the carrier lifetime (τ) increases from 0.22 to 1.3 μs, while is significantly promoted as the carrier lifetime increases from 0.03 to 0.22 μs. This changing trend is obviously different from the on-state resistance, which decreases with the increased carrier lifetime. The simulation result indicates that the heat generation (i.e., maximum temperature rise) inside the PiN diodes, especially in the drift layer, is remarkably aggravated in the pulse tests for τ

The scale of the electric vehicle (EV) industry is expanding in the current new energy industry reform. Lithium-ion batteries (LIBs) have also gotten a lot of interest as the power source for EVs. However, the safety and remaining life of LIB are highly tied to the charging strategy adopted. Particularly, fast charging at low temperatures can cause lithium to deposit on the anode of the battery, intensifying heat production and even evolving into thermal runaway of the battery. Based on the simplified battery Alternating current (AC) impedance model, the optimal frequency of pulse current is analyzed. Considering the influence of state of charge (SOC) and temperature on the battery impedance, a three-dimensional response surface about the optimal frequency, temperature and SOC was established using Mendeley data. To simulate LIB pulse strategy charging in a cold environment, the equivalent circuit model (ECM) is coupled with a simple battery heating model. The three-dimensional response surface is employed to instantly determine the pulse frequency. The simulation results demonstrate that both the bi-directional pulse current charging strategy with optimal frequency and the positive pulse current charging strategy with optimal frequency have faster charging time and better temperature rise effect than the constant current (CC) charging strategy, and can significantly eliminate the polarization voltage of the battery at low temperatures.

BackgroundThe defects generated during the working process of metal materials have a significant impact on their performance. For example, the radiation-induced embrittlement and hardening of reactor pressure vessel (RPV) steels are a factor of concern, which hinders the life extension of the RPV. Annealing treatment is applied to alleviating irradiation-induced precipitates and defects and recover RPV's mechanical properties in the past few decades to extend the in-service lifetime of the RPV. Unfortunately, this conventional method generally requires a high treatment temperature and long operation time, inevitably wasting considerable energy due to the huge size of the RPV. Recently, as a more convenient and energy-saving method, the repair of metal defects by electropulsing treatment (EPT) has been developed.PurposeThis study aims to design and construct a device for EPT processing of samples, and investigate the repairs of defects in electron irradiated and deformed iron and RPV steel after EPT by using positron lifetime spectroscopy.MethodsElectron irradiated pure iron and RPV steel samples were prepared and subjected to multi parameter EPT device developed in laboratory, and the changes in defects of the samples with EPT were characterized by positron lifetime spectroscopy. In addition, the mechanical properties of pure iron tensile samples were characterized by micro Vickers hardness, and the defect information was characterized by positron lifetime spectroscopy to explore the relationship between macroscopic properties and microstructure.ResultsThe defects introduced by electron irradiation in pure iron and RPV steel samples gradually recover after EPT and exhibit similar patterns to annealing treatment. After stretching, the number of defects in pure iron samples increases, leading to an increase in Vickers hardness. EPT can restore defect and reduce Vickers hardness.ConclusionsThe defects generated by irradiation or deformation in pure iron and RPV steel can be partially repaired through EPT. The effect of defect repair is not only related to the initial state of the sample, but also to EPT's parameters. As a new non-destructive testing method, positron annihilation is expected to provide a criterion for material damage or defect repair under the action of pulse current, which can conveniently, quickly, and sensitively detect the defect state of actual working components.

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

Anodizing is widely used as a surface treatment for aluminum alloy to improve its surface properties by increasing the thickness of the oxide layer. Generally, conventional anodizing by direct current (DC) produced high porosity and micro‐cracks. Utilizing pulse current (PC) as a power source and graphite particles as reinforcement for the oxide layer may solve these problems. Therefore, the present work aims to study the effect of the combination approaches on coating growth and the surface characteristics of the oxide coating. The graphite‐incorporated composite oxide coating on the AA2017‐T4 Al alloy was developed by DC and PC hard anodizing process. The surface morphology, topography, chemical composition, and surface hardness were evaluated. In PC anodizing, the growth rate of oxide layer was slower (0.59 μm/min) than DC anodizing (1.08 μm/min). The surface pores start to develop at the 30th minute compared to DC, which is the 20th minute. At 60 min, the formation of porous composite oxide coating is complete with pore dimension (width: 46.74 ± 19.96 μm and depth: 7.11 ± 2.57 μm) and thickness of 35.20 ± 8.90 μm for PC, whereas for DC pore dimension (width: 81.03 ± 21.60 μm and depth: 17.16 ± 4.31 μm) and thickness of 64.80 ± 23.69 μm. Surface roughness and hardness of composite oxide coating by PC were measured at about 1.90 ± 0.04 μm and 379.10 ± 4.37 HV, respectively. Meanwhile, the DC reveals a significant increase in roughness (4.28 ± 0.25 μm) and a decrease in hardness (302.75 ± 1.09 HV). The introduction of graphite particles with PC anodizing reduces the surface porosity, microcracks and enhances the surface hardness of oxide coating. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) PiN diode has shown substantial promise as the freewheel diode for switch protection in a pulsed system. In this paper, we investigate the carrier lifetime (τ) modulation on pulsed current capability of SiC PiN diodes. The carrier lifetime in 4H–SiC is modulated by the generation of the Z1/2 center through neutron irradiation. Surprisingly, we found that the pulsed current of SiC PiN diodes shows a limited improvement when the carrier lifetime (τ) increases from 0.22 to 1.3 μs, while is significantly promoted as the carrier lifetime increases from 0.03 to 0.22 μs. This changing trend is obviously different from the on-state resistance, which decreases with the increased carrier lifetime. The simulation result indicates that the heat generation (i.e., maximum temperature rise) inside the PiN diodes, especially in the drift layer, is remarkably aggravated in the pulse tests for τ < 0.1 μs, but which is significantly suppressed as carrier lifetime rises to 0.2 μs and above. Therefore, the dependence of pulsed current on carrier lifetime is ascribed to the heat generation resulting from the carrier lifetime controlled conductivity modulation effect, which hence affects the temperature rise and brings about the failure of SiC PiN diodes under high pulsed current. [ABSTRACT FROM AUTHOR]

The effect of pulse current ratio on deformation behavior, microstructure and nature of fracture of aluminum bronze BrAZhNMts 9-4-4-1 under tension is studied. Tensile tests are performed and the structure of the bronze is determined. It is shown that pulse current ratio noticeably influences the behavior of the stress-strain curves and bronze mechanical properties. With a minimum pulse ratio within bronze microcrack formation is possible causing accelerated failure. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The detection of partial discharge (PD) in transformers is of great significance for preventing insulation defects from developing into insulation failures. Transformer partial discharge detection technology includes pulse current method, radio frequency measurement method, UHF method, ultrasonic detection method, gas chromatography, and optical detection method. Among them, the optical detection method has the characteristics of strong anti-electromagnetic interference ability, and the signal can be transmitted and received without loss. The optical detection method has unique advantages. In this paper, an optical signal measuring device for partial discharge inside the transformer is designed and fabricated, the typical insulation defect inside the transformer is simulated, and the optical signal characteristics of typical partial discharge are obtained. Compared with the pulse current method, it is found that the magnitude of partial discharge can be characterized by the integral of the optical signal. The characteristic of the optical signal phase resolved partial discharge (PRPD) spectrum of typical insulation defects is obtained. The PRPD spectrum of the optical signals of different defects is obviously different. It is feasible to draw the PRPD spectrum and identify the defect types according to the optical signal, which can be further applied to the identification of internal faults in transformers.

Energy efficiency is an important issue in industry, especially with the ever-increasing consumption of electrical energy. The power quality and the traceability of metering devices are essential when integrating energy metering systems for energy efficiency. This management requires an understanding of electrical current events such as pulse and transient currents. Current transducers are widely used to measure these electrical current events up to a few megahertz. Their use makes it possible to measure not only the main current flowing through the transducer, but also the bypass current that affects electrical equipment. Calibration of these sensors up to a few megahertz then becomes an essential step. Currently, most calibration methods are limited to 100 kHz frequency for a current of 10 A. This paper presents an improvement of a traceable calibration methodology for current transducers up to 10 A and 1 MHz, thus increasing, by 10 times, the current level for such high frequency applications. This calibration methodology is based on a metrological traceability chain (uninterrupted link to the International System of Units) with respect to a calculable current shunt and is currently the only traceable method for calibrating current transducers at 10 A and up to 1 MHz. The uncertainty obtained for the transimpedance ratio is less than 0.2%, which is considerably reduced with respect to the existing capabilities.

This study reinforced Ni–W composites with polytetrafluoroethylene (PTFE) and deposited them on the low-carbon steel substrate by a pulse current (PC) electrodeposition technique. This resulted in improved abrasion resistance and low friction coefficient. The effect of current density on the co-depositions' surface morphology, nano-hardness, friction, and wear performances was investigated. Surface morphologies and worn surfaces of the produced composites were investigated by scanning electron microscopy (SEM). The phase structures of the deposited samples were analyzed using X-ray diffraction (XRD) by calculating the crystallite size and lattice strain. The results showed that PTFE could effectively enhance the tribological performances of the nickel matrix. It was shown that there was an increase in the current density and the same trend was also observed in the amount of incorporated PTFE into the matrix for a certain level. When the deposition was operated at the current density of 10 A/dm2, the average friction coefficient of the composite coating was reduced to 0.24. Moreover, the wear rate of the co-deposition obtained at 10 A/dm2 was significantly decreased, and this was attributed to the uniform distribution of PTFE and refining microstructure of Ni–W. [ABSTRACT FROM AUTHOR]

The effect of a pulsed current on titanium tensile deformation obtained by postdeformation annealing after cold rolling of the coarse-grained and ultrafine-grained states has been considered. The effect of the duty cycle of the pulse current over a wide range on the shape of the stress–strain curves and mechanical properties has been studied. It is shown that an increase in the duty cycle results in an enhancement in the thermal effect of the current and a decrease in the flow stresses, strength, and plasticity, as well as in intense necking. A decrease in the duty cycle leads to the absence of heating and the occurrence of the electroplastic effect and an increase in the strength and plasticity, which depends on the structural state of coarse-grained titanium and the method of titanium production. The possible physical mechanisms of hardening associated with twinning, strain aging, and low-cycle fatigue have been considered. [ABSTRACT FROM AUTHOR]

The pulse current method was introduced to eliminate the residual stress in the S355 steel experimental specimens treated by Nd:YAG pulsed laser surface irradiation. One group of the experimental specimens is cooled to the room temperature, and the other group of the experimental specimens is cooled for 1 minute. Then, the two groups of the experimental specimens were treated by the pulse current. In addition, the residual stress relieving mechanism of the pulse current method was discussed. The results show that the pulse current can effectively eliminate the residual stress of the metal material, and the residual stress relieving effect of the metal material with a certain initial temperature is better than that of the metal material cooled to the room temperature. The initial temperature of the metal material can soften the metal material, which is conducive to the generation of the dislocation slip movement. In this case, the metal material with a certain initial temperature can obtain the better residual stress relieving effect. [ABSTRACT FROM AUTHOR]

The article presents the results of the analysis of heating of printed circuit conductors of printed circuit boards mounted on a metal base, on-board device of spacecraft when pulsed current flows through them. Thermal transient and impulse characteristics of a system consisting of a printed conductor and a printed circuit board are considered. The analysis of the dependence of the temperature rise rate of printed conductors and the duration of transient processes on the linear dimensions of the system elements is given. It is noted in the article that the time of transient processes most strongly depends on the thickness of the layer of insulating materials. All the results were obtained in the process of modeling transients in the ANSYS 2019 R1 Transient Thermal module. Practical recommendations on the consideration of thermal transients in printed conductors in the design of printed circuit boards are given.

Based on the fluid mechanics and electromagnetic theory, a numerical simulation model of droplet transfer during local dry underwater MIG welding (LDU-MIG) of SUS304 was established by using fluid dynamics software FLUENT. The effects of gas pressure, wire feeding speed (WFS) and pulse peak current on the whole droplet transfer process in LDU-MIG were simulated and investigated. The simulation results indicated that the increase of gas pressure reduced the plasma flow force and enlarged the pressure gradient in the local dry cavity, which hindered the droplet transfer process and led to the larger droplet diameters and longer transfer periods. The increase of WFS decreased transfer period in lower current, but it changed the droplet transfer modes in larger current. With the increase of pulse peak current, the droplet transfer modes changed from globular transfer (200 A) to projected transfer with one pulse one droplet (280 A), then to streaming transfer with one pulse multiple droplets (360 A). Finally, the droplet transfer process was captured by high-speed photography technology in LDU-MIG welding experiments, the simulation results were in good agreement with the experimental results, which provided theory guidance and data supports for manufacturing and remanufacturing of underwater structure.

Friction during contact between metals can be very complex in pulse current-assisted forming. Based on stamping process characteristics, a reciprocating friction tester was designed to study the friction characteristics between AA7075 aluminum alloy and P20 steel under different current densities. Origin software was used to process the experimental data, and a current friction coefficient model was established for the pulse current densities. The results show that the friction coefficient of the aluminum alloy sheet decreased with the increase in the pulse current density (2–10 A/mm2). After that, the friction mechanism was determined by observing microscopic morphology and SEM: some oxide cracked on the friction surface when the current was large. Finally, finite element simulations with Abaqus software and a cylindrical case validated the constant and current friction coefficient models. The thickness distribution patterns of the fixed friction coefficient and the current coefficient model were compared with an actual cylindrical drawing part. The results indicate that the new current friction model had a better fit than the fixed one. The simulation results are consistent with the actual verification results. The maximum thinning was at the corner of the stamping die, which improved the simulation accuracy by 7.31%. This indicates the effectiveness of the pulse current friction model. [ABSTRACT FROM AUTHOR]

A combination of the peroxymonosulfate (PMS) electro-activation process and the electro-oxidation process driven by a pulsed electric field (PEF) was used to degrade sulfadiazine (SND) wastewater. Mass transfer is the limiting step of electrochemical processes. The PEF could enhance mass transfer efficiency by reducing the polarization effect and increasing the instantaneous limiting current compared with the constant electric field (CEF), which could benefit the electro-generation of active radicals. The degradation rate of SND after 2 h was 73.08%. The experiments investigated the effects of operating parameters of pulsed power supply, PMS dosage, pH value and electrode inter distance on the degradation rate of SND. The predicted response value of single-factor performance experiments was obtained as 72.26% after 2 h, which was basically consistent with the experimental value. According to the quenching experiments and EPR tests, both SO4•− and •OH were present in the electrochemical processes. The generation of active species were significantly greater in the PEF system than that in the CEF system. Moreover, four kinds of intermediate products were detected during the degradation by LC-MS. This paper presents a new aspect for electrochemical degradation of sulfonamide antibiotics. [ABSTRACT FROM AUTHOR]

CO2 electrolysis with solid oxide electrolytic cells (SOECs) using intermittently available renewable energy has potential applications for carbon neutrality and energy storage. In this study, a pulsed current strategy is used to replicate intermittent energy availability, and the stability and conversion rate of the cyclic operation by a large‐scale flat‐tube SOEC are studied. One hundred cycles under pulsed current ranging from −100 to −300 mA/cm2 with a total operating time of about 800 h were carried out. The results show that after 100 cycles, the cell voltage attenuates by 0.041%/cycle in the high current stage of −300 mA/cm2, indicating that the lifetime of the cell can reach up to about 500 cycles. The total CO2 conversion rate reached 52%, which is close to the theoretical value of 54.3% at −300 mA/cm2, and the calculated efficiency approached 98.2%, assuming heat recycling. This study illustrates the significant advantages of SOEC in efficient electrochemical energy conversion, carbon emission mitigation, and seasonal energy storage. [ABSTRACT FROM AUTHOR]

SiCp/AZ91D magnesium matrix composites with 30% SiCp were successfully prepared by pulsed current melting in this work. Then, the influences of the pulse current on the microstructure, phase composition, and heterogeneous nucleation of the experimental materials were analyzed in detail. The results show that the grain size of both the solidification matrix structure and SiC reinforcement are refined by pulse current treatment, and the refining effect is gradually more obvious with an increase in the pulse current peak value. Moreover, the pulse current reduces the chemical potential of the reaction between SiCp and Mg matrix, thus promoting the reaction between SiCp and the alloy melt and stimulating the formation of Al4C3 along the grain boundaries. Furthermore, Al4C3 and MgO, as heterogeneous nucleation substrates, can induce heterogeneous nucleation and refine the solidification matrix structure. Finally, when increasing the peak value of the pulse current, the repulsive force between the particles increases while the agglomeration phenomenon is suppressed, which results in the dispersed distribution of SiC reinforcements. [ABSTRACT FROM AUTHOR]

Abstract CO2 electrolysis with solid oxide electrolytic cells (SOECs) using intermittently available renewable energy has potential applications for carbon neutrality and energy storage. In this study, a pulsed current strategy is used to replicate intermittent energy availability, and the stability and conversion rate of the cyclic operation by a large‐scale flat‐tube SOEC are studied. One hundred cycles under pulsed current ranging from −100 to −300 mA/cm2 with a total operating time of about 800 h were carried out. The results show that after 100 cycles, the cell voltage attenuates by 0.041%/cycle in the high current stage of −300 mA/cm2, indicating that the lifetime of the cell can reach up to about 500 cycles. The total CO2 conversion rate reached 52%, which is close to the theoretical value of 54.3% at −300 mA/cm2, and the calculated efficiency approached 98.2%, assuming heat recycling. This study illustrates the significant advantages of SOEC in efficient electrochemical energy conversion, carbon emission mitigation, and seasonal energy storage.

Carbon nanotubes (CNTs) can be directly grafted onto the surface of carbon fibers using the chemical vapor deposition method, in which nanometer-order nickel (Ni) particles, serving as catalysts, are plated onto the surface of carbon fibers via electrolytic plating. In our previous studies, in which a direct current (DC) was used to electrolytically plate Ni onto carbon fibers as a catalyst, the site densities and diameters of Ni particles increased simultaneously with the plating time, making it difficult to independently control the site densities and diameters of the particles. On the other hand, pulse current (PC) plating is attracting attention as a plating technique that can control the deposition morphology of nuclei. In this study, we clarify the effect of the parameters of the PC on the particle number per unit area (site density) and the particle diameters of Ni particles plated onto the surface of carbon fibers, using the PC to electrolytically plate Ni. Electrolytically plating Ni onto carbon fibers (via PC) after the removal of the sizing agent enable Ni particles with sparser site densities and larger diameters to be plated than those plated via DC. Using Ni particles with sparse site densities, it is shown that CNTs with sparse site densities can be grafted. [ABSTRACT FROM AUTHOR]

The problem of the real existence of the electroplastic effect during deformation of metallic materials of different nature is still relevant. At the same time, the influence of structure refinement is not considered enough. In this work, the deformation behavior of ultrafine-grained (UFG) titanium Grade 4 is compared with that of coarse-grained (CG) titanium under tension with pulse current of the low duty cycle. The deformation curves of both structure states are presented for different regimes of pulsed current and thermal heating from an external source. Structure studies by optical and scanning electron microscopy, as well as microhardness measurements have been carried out. It is shown that Grade 4 titanium under tension accompanied by pulsed current exhibits electroplastic effect (EPE) in the form of a flow stress reduction. EPE in UFG state is much stronger than in CG state. An increase in the density and duration of the current pulse leads to a multiple decrease in the flow stresses in CG and UFG titanium. The contribution in the flow stress reduction from heating by an external source was less than that from tension with pulse current at the same temperatures. The impact of pulsed current during tension does not influence microhardness and grain size. [ABSTRACT FROM AUTHOR]

High-voltage pulse power supplies are key power input devices for the study and application of discharge plasma. A high-voltage pulse current power supply (HV-PCPS) with an energy storage pulse transformer based on flyback topology can output microsecond pulsewidths with high-power, ultrahigh voltage, and high reliability, which are suitable for most dielectric barrier discharge (DBD) plasma applications. However, during the process of DBD driven by an HV-PCPS based on an energy storage pulse transformer, the output pulse voltage waveform quality is poor, making it not suitable for stable discharge long-term operation. This article aims to solve the aforementioned problem and proposes a novel resistor–diode–diode (RDD) shaping method. Not only can this novel method solve the problem of poor quality of the output pulse power from the HV-PCPS, guaranteeing stable discharge for various DBD electrodes, it can also limit the maximum output voltage amplitude. This prevents overvoltage breakdown when the output terminal is in an open state or a light load state because the HV-PCPS is acting as a current source. This article also analyzes the effectiveness of an RDD branch when solving the problem in theory, and gives a detailed parameter design method. Finally, a 30-kV HV-PCPS prototype is built to verify the effectiveness of the proposed RDD pulse shaping method. The average pulse power output of the whole prototype is greatly improved, and it can achieve an average pulse power output of 1 kW. Furthermore, the electrode loads of different DBD reactors can be driven by this technology. [ABSTRACT FROM AUTHOR]

A model for the analytical calculations of the mean bulk temperature of plastic deformation when applying the pulse current has been developed to calculate the contact temperatures in the areas of adhesion and sliding of a roll relative to the rolled strip. [ABSTRACT FROM AUTHOR]

• Increase in pulse current value induces changes in microstructure of rail repair coatings. • Electromagnetic effect of pulse current enhances microhardness of coatings. • Too much pulse current leads to transcrystalline rupture in the coating. The hardness variation and the behavior of elemental diffusion in pulse current-assisted laser melting of multi-pass monolayer coatings and HAZ were investigated. The results showed that the coating microstructure grains were refined when the pulse current intensity increased from 5A to 10A. The electromagnetic effect generated by the pulse current drove the Fe element in the matrix to diffuse into the coating. When the pulse current was increased to 20 A, the electromagnetic impact effect overcame the bonding strength between the molten pool metals, which caused the coating to transcrystalline repture in the direction of the current movement. Meanwhile, when the pulse current increased within limits, the reduction of grain size and Fe diffusion resulted in more than two-fold hardness enhancement of the coating and HAZ. [ABSTRACT FROM AUTHOR]

Interstitial hydrogen atoms in titanium usually deteriorate the mechanical properties of titanium by brittle hydride phase or hydrogen-enhanced localized plasticity. In this study, hydride was used as the second phase to improve the tensile strength and elongation of TA1 pure titanium. The continuous coarse hydride network is precipitated in TA1 pure titanium after the hydrogen-charged. Then pulse current treatment is used to decompose the original coarse hydride network and reduce the size and number of hydride strips. Finally, a small uniform hydride network is formed in TA1 pure titanium. The results of tensile experiments indicate that the tensile strength of hydrogen-charged TA1 pure titanium treated by pulse current increases from the 286.4 MPa to 316.1 MPa and the elongation increases from the 47.6 % to 56.8 %. The improvement of mechanical properties demonstrate that the small and uniform hydrides can significantly improve the mechanical properties of TA1 pure titanium. In hydrogen-charged TA1 pure titanium treated by pulse current, the increment of strength is mainly caused by hard phase hydrides, and the increase in plasticity is attributed to the role of twins in coordinating deformation during plastic deformation. This study manifests that in addition to being used as a temporary alloying element to optimize the microstructure of titanium, hydrogen can also be directly act as a second phase in titanium to improve the mechanical properties. • Hydride was used for the first time to improve the tensile strength and elongation of Ti. • Hydride and deformation twin are the essential mechanism of tensile properties improvement of Ti. • Interstitial hydrogen has the potential to improve the mechanical properties of titanium. [ABSTRACT FROM AUTHOR]

Laser cladding has the advantages of a short processing cycle and good processing quality, and has been extensively researched in the field of rail property enhancement. The current study focuses mostly on enhancing the mechanical properties of rails by altering the laser process parameters and using complicated materials. However, the enhancement of mechanical properties such as corrosion and friction resistance by laser cladding is limited. As an effective metallurgical processing method, pulse current can be used to control the microstructure and improve the mechanical properties by altering the solidification process of the metal. In this paper, the effects of pulse current parameters (pulse current frequency, current peak, and duty cycle) on microscopic characteristics, such as microstructure number of pores, and microhardness, as well as mechanical properties, such as wear and corrosion resistance, of stellite-6 coatings created by pulse current-assisted laser cladding (PC-ALC), on the U71Mn substrate were investigated. The results showed that the electromagnetic action of the current refined the grains and reduced the number of pores in the PC-ALC coating. The degree of grain fineness increased, then decreased, as the current intensity increased. When compared with the microhardness without pulse current, the average hardness of the HAZ and coating rose by 49.7 % and 167 %, respectively. The results showed a positive link between corrosion resistance and current frequency, but a negative correlation between corrosion resistance and current peak. The corrosion resistance was improved by increasing the current duty cycle from 25 % to 50 %. The wear resistance of coatings was positively related to microhardness, and the coating reached the wear stabilization stage with a friction loss of about 0.5 %. The tests indicated that PC-ALC coatings had good corrosion and friction resistance for rail repair, extending their service life. [Display omitted] • For the first time, pulse current technology is applied to repair laser cladding rails to verify the possibility and improve the performance of the repaired rails. • Corrosion and wear resistance of rail repair coatings significantly enhances by pulse current. • Electromagnetic effect generated by the pulse current cuts the dendrites growing in the molten pool, with a maximum grain refinement rate of 57 %. • The stirring effect of the pulse current in the melt pool greatly reduces the porosity within the coating. [ABSTRACT FROM AUTHOR]

• The multi-piecewise memristor is applied to Hopfield neural network (HNN) replaced with the traditional memristor. • The presented HNN has richer dynamic behavior in comparison with previous models. • Our work may provide new insights into the mechanism of memory and cognition in the nervous. This paper investigates the effect of pulsed currents and multi-piecewise memristor on dynamic behavior of memristive Hopfield neural network (HNN). Firstly, a four-neuron HNN model is constructed by using the traditional memristor as the connecting synapse and its dynamic behavior is analyzed. Secondly, the traditional memristor in the HNN is replaced with a multi-piecewise memristor, and external pulse currents are applied to the model. The system exhibits rich dynamical behavior by introducing varying numbers of pulse current stimuli and adjusting the parameters of the multi-piecewise memristor. Experimental results demonstrate that the number of attractors in the system changes when pulse currents are applied, and after a period of chaotic behavior, the system eventually exhibits periodic activity. Furthermore, adjusting the parameters of the multi-piecewise memristor can generate multiple scroll attractors in the system. Finally, the experimental results were verified by Multisim. [ABSTRACT FROM AUTHOR]

The Inconel 718 superalloy was fabricated using spark plasma sintering (SPS) technology with varying sintering temperatures and heating rates. The densification and mechanical property of the sintered superalloys were characterized through tensile and compression tests at room temperature, as well as microscopic analyses. The evidence suggests that the plasma generated between the particles results in evaporative melting on the particle surface and plastic deformation of the particle boundaries, accelerating the densification process is by 3∼4 times. Besides, the grain size refinement coefficient affected by pulse current in the holding stage is 0.7–0.8, leading to a significant grain boundary strengthening during SPS process. The dislocation dominated by ball milling and SPS parameters also helps improve the strength and plasticity of the sintered superalloy. The superalloy sintered at 1050 °C with a heating rate of 100 °C/min demonstrated the highest tensile and compressive fracture strengths, measuring 1410 MPa and 1983 MPa, respectively, with the tensile and compressive yield strength of 712 MPa and 1557 MPa, respectively. Lower sintering temperatures or higher heating rates results in lower levels of densification and decreased strength. In addition, plasticity is reduced at higher sintering temperatures or lower heating rates due to excessive precipitation of brittle phases. [ABSTRACT FROM AUTHOR]

Due to usage of different materials in corrosive environment, the importance of corrosion resistance composite coating is interestingly increasing. In the present study, the effect of pulse current parameters, such as pulse frequency and duty cycle, on microstructure and corrosion behaviour of Ni–Fe–TiO2 composite, coating on a bath containing optimized consternation of TiO2 nanoparticles, was studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), potansiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluation of microstructure, phase identification and corrosion behaviour, respectively. The results showed that, the corrosion resistance of pulse current coated samples improved in comparison with direct current (DC) sample. In addition, the corrosion resistance of the layer was increased in higher frequencies and lower duty cycles. Furthermore, the results of SEM corresponded that the micro cracks with increasing the frequency were decreased. Moreover, the EDS data proved that, with decreasing the duty cycle the number of embedded particles were raised from 1 to 7% weight percent, also with increasing the frequency this rate was increased from 2 to 6% weight percent. The X-ray analyse was carried out and it showed that crystallite diffraction planes were the same in various pulse frequency and duty cycles and a specific peak was detected which was considered as Ni3Fe, although the crystallite size were declined in higher frequencies. [ABSTRACT FROM AUTHOR]

In the process of metal purification, the study of controlling the morphology and size distribution of non-metallic inclusions in steel based on electric fields has attracted extensive attention. However, the action mechanism of electric fields on inclusions in liquid steel has not been clearly identified. In this paper, the influence of pulse current on the quantity, size, and distribution of alumina inclusions in liquid steel was explored through a high-temperature energization experiment, and the action mechanism of pulse current was expounded based on the angle of interface free energy. The results show that the number of small alumina inclusions in the steel after electric pulse treatment (the pulse current density was 0.1–3 A/cm2, the frequency was 100 Hz, and the pulse waveform was a square wave) was significantly increased compared with the sample without electric pulse treatment, and the particle size was concentrated at 2–5 μm, and the inclusions were concentrated in the upper and lower parts of the sample. However, in the samples without electrification treatment, the large particles of inclusions are the majority, the particle size was concentrated at about 10 μm, and the inclusions were concentrated in the upper and middle parts of the samples. When the pulse current was applied to the molten steel, the interfacial free energy of the internal system of liquid steel alumina inclusion was reduced, the nucleation of alumina inclusion was promoted, the aggregation growth between alumina particles was inhibited, and then the migration and distribution of inclusions were also affected. The experimental results could provide technical support for high-quality steel smelting production to a certain extent. [ABSTRACT FROM AUTHOR]

The main problem in microplate implant production is the high cost of production. It is because the production process uses two machining processes. Microplate production currently uses wire-EDM and micro-milling. Therefore, microplate production with die-sinking EDM has been developed to reduce production costs. This paper proves that microplate implant can be produced by die-sinking EDM. This research also examines the response of pulse currents and electrode materials on the Material Removal Rate (MRR), the surface roughness (Ra) and the White Layer (WL) in the microplate. EDM process uses pulse currents of 6, 9, and 13 A with copper and graphite electrodes. The results show that the microplate has been successfully produced by using die-sinking EDM in a pure titanium sheet with a thickness of 0.4 mm. MRR, Ra and WL are directly proportional to pulse current. The results are greater when using the graphite compared to the copper electrode. MRR, Ra, and WL are in the range of 0.22-0.99 mm3/minute, 5.28-11.13 μm, and 21.66-33.66 μm, respectively. The pulse current of 6A with the copper electrodes produces the microplate of the best quality. [ABSTRACT FROM AUTHOR]