High Electric Current Density Research Articles

Rapid Growth of Niobium Oxide Nanowires by Joule Resistive Heating

Joule heating of niobium (Nb) metal wires by running a high electric current density through them has been used to grow Nb2O5 nanowires. The formation of a micrometric oxide layer on the Nb wires has also been observed. The size and density of the nanowires are related to the current values applied, as well as the thickness of the oxide layer formed. Characterization of both nanowires and oxide layer has been performed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and micro-Raman spectroscopy. It has been observed that this method allows the growth of Nb2O5 nanowires in times as short as tens of seconds.

Structure of the Contact Layers of Steel and Their Deterioration in Dry Sliding Against Steel Under High-Density Electric Currents at Different Turn Ratios of a Supply Transformer

Structure of the Contact Layers of Steel and Their Deterioration in Dry Sliding Against Steel Under High-Density Electric Currents at Different Turn Ratios of a Supply Transformer

Study of heat and mass transfer processes in the Fe-Sn reaction crucible in the presence of high-density electric current

Study of heat and mass transfer processes in the Fe-Sn reaction crucible in the presence of high-density electric current

An avalanche-and-surge robust ultrawide-bandgap heterojunction for power electronics

Avalanche and surge robustness involve fundamental carrier dynamics under high electric field and current density. They are also prerequisites of any power device to survive common overvoltage and overcurrent stresses in power electronics applications such as electric vehicles, electricity grids, and renewable energy processing. Despite tremendous efforts to develop the next-generation power devices using emerging ultra-wide bandgap semiconductors, the lack of effective bipolar doping has been a daunting obstacle for achieving the necessary robustness in these devices. Here we report avalanche and surge robustness in a heterojunction formed between the ultra-wide bandgap n-type gallium oxide and the wide-bandgap p-type nickel oxide. Under 1500 V reverse bias, impact ionization initiates in gallium oxide, and the staggered band alignment favors efficient hole removal, enabling a high avalanche current over 50 A. Under forward bias, bipolar conductivity modulation enables the junction to survive over 50 A surge current. Moreover, the asymmetric carrier lifetime makes the high-level carrier injection dominant in nickel oxide, enabling a fast reverse recovery within 15 ns. This heterojunction breaks the fundamental trade-off between robustness and switching speed in conventional homojunctions and removes a key hurdle to advance ultra-wide bandgap semiconductor devices for power industrial applications.

Synergetic-modified porous Co2SiO4 conductive network with ZIF-8 derived carbon and reduced graphene oxide for high-rate lithium-ion battery anode

Aiming at the key problems such as low conductivity, volume expansion rate and poor rate performance faced by high-capacity silicon-based anode, a three-dimensional porous Co2SiO4/rGO/ZIFC conductive network is designed and prepared by synergistic modifying Co2SiO4 with reduced graphene oxide (rGO) and ZIF-8 derived carbon (ZIFC). The internal rGO as a lamellar template, supporting substrate and conductive bridge accelerates the transfer of electrons, while the external reasonable coating of ZIF-8 derived carbon greatly maintains the overall structure of the material and supplies fields for lithium-ion diffusion. The obtained porous structure can not only lead to excellent ion diffusion rate and promote the electrochemical interface reaction, but also relieve volume expansion of the material during the cycling, thus heightening the electrochemical performance. The obtained Co2SiO4/rGO/ZIFC electrode offers an outstanding specific capacity of 1295 mA h g−1 at 0.2 A g−1 and 650 mA h g−1 even at a high electric current density of 5 A g−1. The pseudocapacitance ratio of the Co2SiO4/rGO/ZIFC anode at a scan rate of 0.8 mV s−1 is as high as 91%, verifying its excellent lithium ion kinetics and promising rate performance.

Control of Microstructure in Iron–Carbon Thin Films by Means of Electromigration

Herein, it is demonstrated that high DC electric current densities can be used to tailor the microstructure of iron–carbon thin films. Specifically, elongated ferrite grains can be formed in a nanocrystalline matrix via a process involving electromigration‐induced carbide migration. Herein this article, the parameters that are required to produce and control elongated grain formation in the Fe(C) system are mapped out and they are interpreted in terms of carbon electromigration, and the flux divergences need to reach a critical carbon concentration for precipitate growth and migration. Possible approaches to allow more precise control of the elongated grains are discussed, as are the requirements for material systems where microstructure control through electromigration should be feasible.

Evaluation of the Effects of Electrical Stimulation: A Pilot Experiment on the Marine Benthic Foraminiferal Species Amphistegina lessonii.

Environmental disturbances resulting from anthropogenic energy pollution are intensely growing and represent a concern for the marine environment. Benthic organisms are the significant fauna exposed to this kind of pollution; among them, foraminifera are largely used as pollution bioindicators in marine environments, but studies on the effects induced by electrical stimulation are not documented. In the present research, we evaluated the effects of short-term different electric current densities on the viability of benthic foraminiferal species Amphistegina lessonii by checking the pseudopodial activity and defined the threshold electrical density range. After 3 days of treatment, A. lessonii stimulated with a constant current showed pseudopodial activity at a lower electric current density (0.29, 0.86 μA/cm2) up to 24 h. With increasing stimulation time, the percentages of pseudopodial activity decreased. The pseudopodial activity was absent at high current densities (5.71, 8.57 μA/cm2). The viability of A. lessonii exposed to a pulsed current was higher at a low and middle electric current density (from 0.29 to 5.71 μA/cm2) than at a high electric current density (from 11.43 to 20 μA/cm2). Based on these preliminary results, the selected benthic foraminiferal species seems to better stand pulsed currents than constant ones. These first experiments might provide useful information for the definition of the appropriate electrical density threshold to avoid side effects on a part of the benthic community.

Viscous plastic flow in contact layers as a method of stress relaxation in dry sliding of steel against steel under electric current

Electric current in sliding provides intense external impact on the surface with generation of a tribolayer. The wear resistance of the layer will be depended on ability stress relaxation due to plastic deformation in the friction zone. Determining the structural states of tribolayers of contact AISI 1020 steel /AISI 1045 steel in the ultimate state in dry sliding under high density electric current is the purpose of this work. The formation of tribolayers containing wuestite has been shown. The morphological structure of the worn sliding surface of AISI 1020 steel consisted of two sectors. It was found that the surface of one of the sectors and the worn surface of the counterbody had signs of viscous plastic flow.

Unprecedented Multifunctionality in 1D Nb1‐xTaxS3 Transition Metal Trichalcogenide Alloy

Abstract1D materials, such as nanofibers or nanoribbons are considered as the future ultimate limit of downscaling for modern electrical and electrochemical devices. Here, for the first time, nanofibers of a solid solution transition metal trichalcogenide (TMTC), Nb1‐xTaxS3, are successfully synthesized with outstanding electrical, thermal, and electrochemical characteristics rivaling the performance of the‐state‐of‐the art materials for each application. This material shows nearly unchanged sheet resistance (≈740 Ω sq−1) versus bending cycles tested up to 90 cycles, stable sheet resistance in ambient conditions tested up to 60 days, remarkably high electrical breakdown current density of ≈30 MA cm−2, strong evidence of successive charge density wave transitions, and outstanding thermal stability up to ≈800 K. Additionally, this material demonstrates excellent activity and selectivity for CO2 conversion to CO reaching ≈350 mA cm−2 at −0.8 V versus RHE with a turnover frequency number of 25. It also exhibits an excellent performance in a high‐rate Li–air battery with the specific capacity of 3000 mAh g−1 at a current density of 0.3 mA cm−2. This study uncovers the multifunctionality in 1D TMTC alloys for a wide range of applications and opens a new direction for the design of the next generation low‐dimensional materials.

Carbon nanofiber-polyelectrolyte triggered piezoelectric polymer-based hydrophilic nanocomposite for high sensing voltage generation

Flexible electronic devices with flexible sensors have drawn enormous attention due to their wide variety of applications, such as wearable health monitoring devices, bendable touch screens, flexible storage devices, artificial skins, etc. However, the mechanical and electrical performance of devices should be enhanced by new materials design or an innovative device structure to fulfill the requirements for such applications. Here, a poly(vinylidenefluoride) (PVDF) piezoelectric polymer-based hydrophilic nanocomposite (PHNC) sensing membrane using carbon nanofibers (CNF) and poly-acrylamido-methyl-propane-sulfonic acid (PAMPS) polyelectrolyte exhibiting enhanced mechanical and electrical performance is demonstrated. The hydrophilic PAMPS intruded in the PVDF/CNF composition, triggering microstructural changes and facilitating a strong polar β-phase PVDF formation. A dc conductivity of 0.43 S/cm and high electric current density (3.64 μA/cm2) were achieved from PVDF/CNF/PAMPS (80/2/18) PHNC. The piezoelectric performance of the PHNC was investigated for several bending cycles, and it generates the maximum peak output voltage up to 3.65 V under the repeated bending-releasing test procedure. A wearable sensor application is demonstrated by exposing it to different human body movements. During finger motion and elbow movements, the developed PHNC generated piezoelectric maximum peak output voltage up to 3.58 V at a bending angle of 180° for finger motion and 2.2 V for elbow movement. The fabricated PHNC are highly flexible and exhibit outstanding reproducibility and reliability, making them ideal for energy harvesting, the self-powered sensor in wearable electronic devices, electronic skin (e-skin), and soft robotics applications.

Enhancement of hydrogen production using dynamic magnetic field through water electrolysis

Static magnetic field (SMF) application in water electrolysis increases hydrogen production. However, the effect of the dynamic magnetic field (DMF) in water electrolysis is rarely studied. This study utilizes DMF to increase hydrogen production in water electrolysis. DMF was generated by rotating a plate-shaped magnet. As a result, DMF produces 23.1 mL H2, which almost doubled the 12.1 mL H2 of SMF. DMF increases the chance of hydrogen formation by weakening the covalent bond, hydrogen bond, and increase the ion transfer mobility as a result of additional magnetic field strength. This phenomenon consistent with the Faraday's law where fluctuating magnetic field generates an electromotive force that increases electric current density. The high electric current density alters hydroxide ion mobility as the interchanging magnetic force field by DMF increases the ions collision chance. The additional magnetic force by DMF has aligned more water molecules than DMF. Consequently, more water molecule dipoles are exposed during electrolysis. Hence, DMF eases the water-splitting process by shaking the water molecules, which continuously aligns the dipole and also energizes the water molecules. The energized water with higher kinetic energy is easier to split as the required ionization energy has reduced. This happens as the result of the spin-pair magnetic energy conversion that is stimulated by external magnetic field. The increase in rotational speed of magnetic rods does not significantly increase hydrogen evolution reaction and lower the electrolysis efficiency. This indicates the presence of DMF is more important for water electrolysis performance than the rotational speed of DMF. Conclusively, DMF enhances hydrogen evolution reaction by an increase in water kinetic energy and increase in ion transfer chance through dipole exposition.

MHD instability at the cathode spot as the origin of the vortex formation in high-intensity plasma arcs

Magnetohydrodynamic instability in a high-intensity arc, similar to typical arcs in DC electric arc furnaces, is simulated using an induction based model under 2D axisymmetric conditions. Time-averaged results show a good agreement with steady-state calculated results expected for a stable arc. The transient results declare that z-pinch close to the cathode, occurring due to the high electrical current density, is responsible for arc instability in this region. The unstable behavior of the arc can be evaluated in a periodic procedure. Moreover, correlations between the fluctuations in total voltage drop curve and the arc shape are investigated: when the arc is in form of column (or bell) the total voltage drop is on a minimum peak; if there is an irregular expansion of the arc in form of arms, the total voltage drop shows a maximum peak.

Connecting the phase-field-crystal model of electromigration with electronic and continuum theories

Electromigration (EM) is the motion of lattice atoms under high-density electric current. It is an important mechanism for structural changes in nanoelectronic devices and a major contributor to the electroplastic effect in structural metals. Recently, a phase-field-crystal (PFC) model for studying EM in metals was developed and shown to successfully capture many important EM-driven structural evolutions at experimentally relevant timescales. In this work, connections between the previous PFC EM model and existing EM theories are established. It is shown that the PFC model can be linked to both the electron-density-based quantum EM theory and the drift-diffusion-based continuum EM theory, therefore filling an important gap in the theoretical and computational study of EM-related phenomena. The numerical method for implementing the PFC EM model is discussed in detail. The well-established Blech effect is quantitatively reproduced using the model.

(Invited) Corrosion Resistant Coatings for PEM Bipolar Plates, Current Collectors, and PTL’s

The industrial trend with respect to PEM bipolar plate is to move from graphite plates to metal plates. The most common materials are stainless steel grades for fuel cells and titanium for electrolyzers. The typical applications of fuel cells expect a lifetime of 5,000 to 7,000 hours for passenger cars and over 20,000 hours for heavy duty applications like trucks, buses, trains and electrolyzers in general.Stainless steel is in general known for a good corrosion resistance by the formation of a native chromiumoxide film on the material’s surface. However, the operating conditions at elevated operating voltages, corrosive electrolytes, aggressive gases, and elevated temperatures break down such protective films and lead to metal ion release from the stainless steel into the stack. This causes so called poisoning of the catalyst and reduced functioning of the cells and limiting the lifetime of a stack. Titanium based bipolar plates are sensitive to hydrogen embrittlement during electrolyzing operations and need protection as well.Special coatings are developed and under further optimization to overcome the above challenges. There are three main criteria to be solved in parallel, i.e. high corrosion resistance, low electrical resistance to cope with the high current densities, and economically affordable. Technically there is a conflict between high corrosion resistance and high electrical current densities as it will trigger electrochemical corrosion. Any coating solution needs to be available at bipolar plate sizes and reproducible at high volume production, not just laboratory scale.The discussion will be about coating models, including the effect of small coating defects as they always will be present. To avoid increased local pitting corrosion, there will be a benefit of having some kind of self-healing mechanism by applying special base layers between the bipolar plate and the functional coatings. For fuel cell bipolar plates different versions of carbon-based coatings by PVD will be covered as well as combined PVD and thermal spray solutions (known as the TreadstoneTM DOT’s process). For the titanium based bipolar plates the focus will be on applying precious metals by thermal spray, varying materials for the cathode and anode side. The use of coatings also finds its way on current collectors and porous transport layers (PTL’s).Concepts and machines for mass production of such coatings will be presented.

In Situ Formed Weave Cage-Like Nanostructure Wrapped Mesoporous Micron Silicon Anode for Enhanced Stable Lithium-Ion Battery.

The low-cost and high-capacity micron silicon is identified as the suitable anode material for high-performance lithium-ion batteries (LIBs). However, the particle fracture and severe capacity fading during electrochemical cycling greatly impede the practical application of LIBs. Herein, we first proposed an in situ reduction and template assembly strategy to attain a weave cage-like carbon nanostructure, composed of short carbon nanotubes and small graphene flakes, as a flexible nanotemplate that closely wrapped micron-sized mesoporous silicon (PSi) to form a robust composite construction. The in situ formed weave cage-like carbon nanostructure can remarkably improve the electrochemical property and structural stability of micron-sized PSi during deep galvanostatic cycling and high electric current density owing to multiple attractive advantages. As a result, the rechargeable LIB applying this anode material exhibits improved initial Coulombic efficiency (ICE), excellent rate performance, and cyclic stability in the existing micron-sized PSi/nanocarbon system. Moreover, this anode reached an approximation of 100% ICE after only three cycles and maintains this level in subsequent cycles. This design of flexible nanotemplated platform wrapped micron-sized PSi anode provides a steerable nanoengineering strategy toward conquering the challenge of long-term reliable LIB application.

Toward MXene interconnects

Performance challenges as electronics continue to scale down motivate searches for new interconnect materials. In a recent report in Matter, Lipatov and coworkers demonstrate that MXene may be a candidate for interconnects by measuring conductivity and breakdown current density of Ti3C2Tx. Performance challenges as electronics continue to scale down motivate searches for new interconnect materials. In a recent report in Matter, Lipatov and coworkers demonstrate that MXene may be a candidate for interconnects by measuring conductivity and breakdown current density of Ti3C2Tx. High electrical conductivity and breakdown current density of individual monolayer Ti3C2Tx MXene flakesLipatov et al.MatterMarch 3, 2021In BriefAs the scaling down of integrated circuits continues, there is a growing interest in electrically conductive materials with high current-carrying capacity for the next generation of on-chip interconnects. Here, we report that monolayer Ti3C2Tx MXene, an emerging two-dimensional material, has a high breakdown current density of 1.2 × 108 A cm−2, which exceeds such properties of copper and other conventional metals. The remarkable combination of high electrical conductivity and high current-carrying capacity makes Ti3C2Tx promising for interconnect applications. Full-Text PDF

Microscale Schottky superlubric generator with high direct-current density and ultralong life

Miniaturized or microscale generators that can effectively convert weak and random mechanical energy into electricity have significant potential to provide solutions for the power supply problem of distributed devices. However, owing to the common occurrence of friction and wear, all such generators developed so far have failed to simultaneously achieve sufficiently high current density and sufficiently long lifetime, which are crucial for real-world applications. To address this issue, we invent a microscale Schottky superlubric generator (S-SLG), such that the sliding contact between microsized graphite flakes and n-type silicon is in a structural superlubric state (an ultra-low friction and wearless state). The S-SLG not only generates high current (~210 Am−2) and power (~7 Wm−2) densities, but also achieves a long lifetime of at least 5,000 cycles, while maintaining stable high electrical current density (~119 Am−2). No current decay and wear are observed during the experiment, indicating that the actual persistence of the S-SLG is enduring or virtually unlimited. By excluding the mechanism of friction-induced excitation in the S-SLG, we further demonstrate an electronic drift process during relative sliding using a quasi-static semiconductor finite element simulation. Our work may guide and accelerate the future use of S-SLGs in real-world applications.

High electrical conductivity and breakdown current density of individual monolayer Ti3C2Tx MXene flakes

High electrical conductivity and breakdown current density of individual monolayer Ti3C2Tx MXene flakes

Ultralow-current magnetization switching in nearly compensated synthetic antiferromagnetic frames using sandwiched spin sources

Spin–orbit torque (SOT)-induced magnetization switching via electric currents in large spin–orbit-coupled heavy metal (HM)/ferromagnetic (FM) frames is one of the most reliable approaches to achieve increased performances in various spintronic applications. However, its widespread utilization is still challenging owing to the inherent requirement of a high electric current density for efficient magnetization switching. In this paper, we introduce a sandwiched synthetic antiferromagnetic (S-SyAF) frame, comprising CoFeB (FM)/W (HM)/CoFeB (FM) stacks, whose operation is mediated by the Ruderman–Kittel–Kasuya–Yosida interaction. The middle HM layer serves as a spin current source for the top and bottom FM layers simultaneously. In addition, the S-SyAF frame contributes to a substantial reduction in the net magnetization, which ensures a considerably increased SOT switching efficiency; further, the switching current was almost 10 times smaller than that in a conventional HM/FM frame. Thus, we believe that these experimental findings will provide a new avenue for designing future spintronic devices.

Separating the reaction and spark plasma sintering effects during the formation of TiC–Cu composites from mechanically milled Ti–C–3Cu mixtures

The goal of this work was to separate the reaction and spark plasma sintering (SPS) effects during the in-situ synthesis of TiC in mechanically milled Ti–C–3Cu powder mixtures. The powders were milled for 3–10 min in a high-energy planetary ball mill. Structural changes occurring in the reaction mixtures during thermal explosion (TE) in a furnace and SPS in a graphite die were compared. Although the maximum temperature of TE reached the melting point of copper in some samples, no evidence of extensive melting was observed in the microstructure of the products of TE. The ignition and maximum temperatures of TE were found to decrease with increasing milling time of the mixture. In the mixture milled for 10 min, the maximum temperature of TE was only 820 °C. Melting of copper at the inter-particle contacts during SPS was observed in samples milled for 5–10 min (SPS at 900–980 °C) and caused the formation of TiC-depleted regions in the microstructure. Those regions were the re-solidified melt partially filling the pores between the agglomerates. Based on the analysis of the TE parameters in the mixtures and microstructures of the products of TE and SPS, melting during SPS was attributed to the effect of electric current (a high electric current density at the inter-particle contacts) and not to the heat of reaction. The hardness, compressive strength and Young's modulus of the sintered composites are reported. A TiC–Cu composite (milling time 5 min, SPS at 980 °C, relative density 93%) shows a compressive yield strength of 890 MPa and an ultimate compressive strength of 920 MPa.