High Electric Potential Research Articles

Lattice Boltzmann simulation of ion and electron transport during the discharge process in a randomly reconstructed porous electrode of a lithium-ion battery

Rechargeable lithium–ion batteries (LIBs) have improved significantly over the past 20 years; however, the micro-scale working mechanism of these batteries, especially the influence of electrode microstructures on battery performance, still requires further study. The relationship between the electrode microstructure and battery performance is studied in detail by developing a two-dimensional (2D) lattice Boltzmann model to reveal the ion and electron transport within an LIB porous electrode. The present model is established by using randomly reconstructed electrode geometry and the coupling of the electrochemical reaction and ion and electron transport under complex boundary conditions. The influences of the micro-scale morphological features of the battery electrode on the local lithium concentration distribution, electric potential and macroscopic discharge performance are revealed. The randomness of the particle distribution and particle shape result in a heterogeneous distribution of the lithium concentration and electrode potential. In electrode particles, lithium exchanges are enhanced for small particles and improved at the edges and corners for large irregular particles. Regions with low lithium concentration produce a high electric potential. A large particle size and low porosity in an anode improve battery performance. Likewise, a small particle size and high porosity in a cathode also improve battery performance.

TIG arc-induced non-contact MIG arc ignition

Based on recorded arc images, the metal inert gas (MIG) arc ignition process is analyzed and the effects of different tungsten inert gas (TIG) welding parameters on MIG arc ignition are investigated. The TIG arc induces the non-contact ignition of the MIG arc because a filamentary discharge channel develops from the MIG wire end to the TIG arc, causing the electrical breakdown of the gap between them. Among TIG welding parameters, the TIG welding current and tungsten-wire spacing are considered the main factors affecting the non-contact MIG arc ignition because changing them has a relatively greater impact on the ease of non-contact MIG arc ignition. The gap breaks down at low MIG no-load voltage because the MIG wire end has a higher electric potential than the TIG arc, a strong electric field region exists near the MIG wire end, and the MIG wire can be fed toward the workpiece.

Pattern transition from dense branching morphology to fractal for copper and β′ brass electrodeposition in thin gap geometry

Copper and β′ brass are electrodeposited in thin gap geometry and a clear transition from dense branching to fractal like pattern is observed with the variation of electric potential and concentration. The transition electric potential is 6V – 5V for copper and 25V for β′ brass. The explanation of the pattern transition is done first using the Laplacian growth as in the Di-electric Breakdown Model (DBM) and then on the basis of ion dynamics in terms of viscosity, ionic mobility, drift and thermal velocity. The fractal growth is more likely at higher electric potential as the electric field dominates and more likely to be dense branched at lower electric field when thermal motion dominates. This work inspires for further studies on modification of our model for the two ions electrodeposition and their compositional variation with different deposition parameters.

Influence of the Charge/Discharge Voltage Range on the Capacity Reversibility and Electrode/Electrolyte Interface Stability of LiCo1/3Ni1/3Mn1/3O2

Introduction Many attempts have been made to increase the energy density of Li-ion batteries using positive electrode materials such as LiMO2 (LiCoO2, LiNiO2, LiNi1/3Mn1/3Co1/3O2, etc.), which have high charging voltages (typically ≥4.4 V). Various studies to understand the associated degradation mechanism and improve the capacity reversibility during high-voltage charge/discharge have been reported. Generally, the inter-terminal voltage of Li-ion batteries can be practically controlled by changing the electric potential of the positive electrode. Thus, the positive electrodes used for high-voltage charge/discharge are exposed to a high electric potential as well as a large change in the electric potential. In this study, we examined the influence of the operating voltage range on the charge/discharge characteristics, and found that the discharge cutoff voltage greatly influences the capacity reversibility during high-voltage charge/discharge. Additionally, we discuss the mechanisms that determine the capacity reversibility based on the results of electrochemical impedance analysis and soft X-ray absorption spectroscopy (soft XAS). Experimental LiNi1/3Co1/3Mn1/3O2 powder, with a secondary particle diameter of 10 μm (Toda Kogyo Corp.), was used as the active material. Positive electrodes were fabricated from a mixture of 90 wt% LiNi1/3Co1/3Mn1/3O2, 5 wt% acetylene black, and 5 wt% polyvinylidene fluoride. The electrochemical characteristics of the samples were examined in coin cells with a Li-metal counter electrode. A 1.0 mol dm-3 solution of LiPF6 in ethylene carbonate + diethyl carbonate was used as the electrolyte. The cells were cycled at discharge-charge cutoff voltages of 2.5–4.6, 3.0–4.6, 3.8–4.6, and 4.2–4.6 V, at a current rate of 1 C. The Li-ion transfer characteristics were measured by alternating current impedance spectroscopy. The electronic structure of the LiNi1/3Co1/3Mn1/3O2was investigated using soft XAS at the beam line BL11 of Ritsumeikan University SR Center (Shiga, JAPAN). Results and Discussion Figures 1a and b show the discharge capacity and discharge capacity retention versus cycle number for LiNi1/3Co1/3Mn1/3O2 cycled with different voltage ranges. As the discharge cutoff voltage was increased, the initial discharge capacity decreased, accompanied by an improvement in the discharge capacity retention. The retentions at the 143rd cycle for LiNi1/3Co1/3Mn1/3O2cycled with 2.5–4.6, 3.0–4.6, 3.8–4.6, and 4.2–4.6 V, were 8, 37, 56, and 81%, respectively. Figure 2a shows the Nyquist plots for LiNi1/3Co1/3Mn1/3O2 cycled with different voltage ranges at an open circuit voltage of ~4.2 V after 3 cycles. The charge transfer resistances (R ct) calculated from the semicircles in the lower frequency region were almost equal (5–8 Ω) regardless of the discharge cutoff voltage. From the Nyquist plots after 143 cycles (Figure 2b), the R ct for LiNi1/3Co1/3Mn1/3O2 cycled with 2.5–4.6, 3.0–4.6, 3.8–4.6, and 4.2–4.6 V, were obtained as 3800, 300, 65, and 17 Ω, respectively. The increase of R ct with the number of cycles was significantly suppressed as the discharge cutoff voltage was increased, resulting in the higher capacity retention observed in Fig. 1b. These results suggest that a stable interface is retained between the electrode and electrolyte when the charge/discharge voltage is limited to the high-voltage region only. The interface structure and the capacity reversibility mechanism will be discussed along with the electronic state of LiNi1/3Co1/3Mn1/3O2analyzed by soft XAS. Acknowledgements This work is financially supported by the RISINGII project of the NEDO and METI, Japan. Figure 1

Production of polyvinylidene fluoride nanofibers by free surface electrospinning from wire electrode

Electrospinning is the manufacturing technology for production nanoscale fibers from the polymer solution. The technique is operated in an electric field with high voltage electrical potential between two conductive electrodes. A needle is used as the anode in laboratory generally. However, the needle process is low productivity for commercialization. Free surface electrospinning is designed for solving the problem. Component use as electrodes isn’t a needle. In this work represented a needle anode by a wire electrode for increasing mass production. Polymer solution droplets were entrained on a wire and control uniformity of themselves droplet. High voltage potential could be applied between wire and ground plate on the top. Polyvinylidene fluoride (PVDF) was used as a precursor to prepared nanofiber. Morphologies of nanofibers were characterized using scanning electron microscope, which informed surface description of the nanofiber. Free surface electrospinning is alternative electrostatic fiber formation technique that can produce the nanofibers thin films continuously. This process convenient for apply in roll to roll process and useful for large scale production.

Pre-Lightning Strikes and Aircraft Electrostatics

An electric storm is a source of electrostatic charge that can induce high current and electric potential on a surface of an aircraft through direct effects. It can also be a source of radiated electromagnetic pulses on an aircraft in flight through indirect effects. Both direct and indirect effects can have adverse effects on flight safety. Thus, it is vital to gain good understanding of the pre-lightning strike and the electrical characteristics of a thunderstorm in order to quantify lightning threats to aircraft. Since lightning parameters are not easily measurable, predictive modeling can be applied to model the pre-lightning strike and aircraft electrostatics. In this paper, we applied the 3D dipole model in predicting the electrostatics build up along an aircraft extremities as it approaches an ambient electric field of a charged cloud. The results give a quantitative evaluation of the threats during pre-lightning strikes and electrostatics buildup on the aircraft. This is vital in designing and coordinating shielding measures to mitigate the threats and to harden the protection systems for aircraft.

Photon and carrier management design for nonplanar thin-film copper indium gallium selenide photovoltaics

Nonplanar structured photovoltaic absorber design has potential to achieve high solar cell efficiency with significantly reduced material use. We report optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(InxGa1−x)Se2 (CIGS) device performance. Structures realized via either self-assembly or patterning via nanoimprint lithography, and also a combination of both are predicted to exhibit significant increases in short circuit current density and open circuit voltage simultaneously. The structures investigated include: 1) self-assembled nonplanar structures that strongly scatter incident light and enhance carrier generation near regions of high electric potential, 2) lithographically-patterned embedded periodic dielectric structures, 3) planar dielectric layers that separate the CIGS absorber from the molybdenum back-contact via reduced-area contacts that minimize optical and electronic losses, 4) a combination of these for combined effects. We find that the self-assembled nonplanar CIGS cells with 700nm planar equivalent thickness, combined with dielectric separation layers yield increases in short circuit current density and open circuit voltage up to 3.4mAcm−2 and 29mV, respectively. The absolute efficiency increases from 15.4% to 18.1%, compared to the predicted efficiency for planar CIGS thin film cells of equivalent thickness. The addition of a single layer MgF2 anti-reflection coating brings the maximum predicted efficiency up to 19.7% for randomly textured devices.

Visualizing Electrical Potential Distribution Using a Point-by-Point Scanning Method: Preliminary Investigation on the Bioactive Points over the Skins of Rodents

Objectives: Acupuncture points as bioactive points on human skin have special electrical properties, compared to points in surrounding areas. This article focuses on measuring skin electrical potentials in a rat model using a point-by-point scanning method. Materials and Methods: Animals were placed on a motorized stage with two orthogonal degrees of freedom. X- and Y-coordinates were set by stepper motors and determined the position of each measurement. A third orthogonal axis, the Z-axis, was under separate stepper control and was used to raise and lower the electrode, thus determining contact pressure between the electrode and the skin. The abdominal region, centered around the umbilicus, was chosen for the study. Data were processed to produce visual images. Results: Distribution mapping demonstrated the existence of high potential points that were distinct from surrounding regions. Positions and intensity of these high potential points were variable. Conclusions: High electrical potential points may have applicability in future acupuncture research.

Characterization of an aerosol microconcentrator for analysis using microscale optical spectroscopies

Efficient microconcentration of aerosols to a substrate is essential for effectively coupling the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma, or micro-Raman or infrared spectroscopies. In this study, we present detailed characterization of a corona-based aerosol microconcentration technique developed previously (Diwakar & Kulkarni, 2012). The method involves two coaxial electrodes separated by a few millimeters, one held at a high electrical potential and the other grounded. The particles are collected on the collection (i.e., ground) electrode from a coaxial aerosol flow in a one-step charge-and-collect scheme using corona discharge and electrical precipitation between the two electrodes. Performance of the corona microconcentration method was determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity was experimentally determined for the aerosol microconcentrator. Using this sensitivity, we show that corona-based microconcentration is much superior to alternative methods, including filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. The method offers unique advantages for compact, hand-held aerosol analytical instrumentation.

High Voltage Generation With Transversely Shock-Compressed Ferroelectrics: Breakdown Field on Thickness Dependence

The ability of ferroelectric materials to generate high voltage under shock compression is a fundamental physical effect that makes it possible to create miniature autonomous explosive-driven pulsed power systems. Shock-induced depolarization releases an electric charge at the electrodes of the ferroelectric element, and a high electric potential and a high electric field appear across the element. We performed systematic studies of the electric breakdown field, $E_{b}(d)$ , as a function of the ferroelectric element thickness, $d$ , for Pb(Zr0.95Ti0.05)O3 (PZT 95/5) and Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ceramics compressed by transverse shock waves (shock front propagates perpendicular to the polarization vector) and established a relationship between these two values: $E_{b}(d) = \textrm {const}\cdot d^{-\xi }$ . This law was found to be true in a wide range of ferroelectric element thicknesses from 1 to 50 mm. This result makes it possible to predict ferroelectric generator (FEG) output voltages up to 500 kV and it forms the basis for the design of ultrahigh-voltage FEG systems.

(Invited) Layered (III-Se) Photodetectors

Due to the unique properties of the 2D materials, the photodetectors based on two dimensional (2D) materials have attracted considerable attentions. For both the bottom and top Ti/Au contacted metal-semiconductor-metal (MSM) photodetectors in using layered GaSe and InSe devices, we systematically investigate the dependence of the photoresponsivity on the spacing distance. Through spatially resolved photocurrent measurements, we find the photocurrent active region is always close to the Schottky barrier with higher electrical potential. A theoretical model has also been developed to well explain for the underlying physics for the photoresponse [1]. The response time can be further reduced down to a few hundreds of microseconds for the devices with single layer graphene as metallic electrodes [2]. References (1) Y. F. Cao, K. M Cai, P. A. HU, L. X. Zhao, T. F. Yan, W. G. Luo, X. H. Zhang, X. G. Wu, K. Y. Wang and H. Z. Zheng, Scientific Reports, 5, 8130 (2015). (2) W. G. Luo, Y. F. Cao, P. A. Hu, K. M. Cai, Q. Feng, F. G. Yan, T. F. Yan, X. H. Zhang and K. Y. Wang, Adv. Opt. Mater., 3,(2015)1418.

Corrosion resistance characteristics of a Ti-6Al-4V alloy scaffold that is fabricated by electron beam melting and selective laser melting for implantation in vivo

The purpose of this study is to determine the corrosion resistance of Ti-6Al-4V alloy fabricated with electron beam melting and selective laser melting for implantation in vivo. Ti-6Al-4V alloy specimens were fabricated with electron beam melting (EBM) and selective laser melting (SLM). A wrought form of Ti-6Al-4V alloy was used as a control. Surface morphology observation, component analysis, corrosion resistance experimental results, electrochemical impedance spectroscopy, crevice corrosion resistance experimental results, immersion test and metal ions precipitation analysis were processed, respectively. The thermal stability of EBM specimen was the worst, based on the result of open circuit potential (OCP) result. The result of electrochemical impedance spectroscopy indicated that the corrosion resistance of the SLM specimen was the best under the low electric potential. The result of potentiodynamic polarization suggested that the corrosion resistance of the SLM specimen was the best under the low electric potential (<1.5V) and EBM specimen was the best under the high electric potential (>1.5V).The crevice corrosion resistance of the EBM specimen was the best. The corrosion resistance of SLM specimen was the best, based on the result of immersion test. The content of Ti, Al and V ions of EBM, SLM and wrought specimens was very low. In general, the scaffolds that were fabricated with EBM and SLM had good corrosion resistance, and were suitable for implantation in vivo.

Characterisation of anomalous forces on asymmetric high‐voltage capacitors

In this study, the authors analysed an anomalous force observed in asymmetric capacitors, working in high electric potentials. From a lot of experimental measurements performed in their asymmetric capacitor, they detected real variations of the device inertia. An empirical formula of the developed force according to Clausius–Mossotti relation explained the experimental results with good agreement, suggesting that the anomalous force can be related directly to the electric dipoles inside the capacitor dielectric. They could also explain why that force always points toward the small electrode when it is subjected to a convergent electric field. Such simple electrical propulsion systems could allow in the future the substitution of the fuel propulsion technology.

On the anomalous forces of high voltage symmetrical capacitors

In this work, we analyzed an anomalous effect verified from symmetrical capacitor devices, working in very high electric potentials. The mastery of that effect could mean in the future the possible substitution of propulsion technology based on fuels by single electrical propulsion systems. From experimental measurements, we detected small variations of the device inertia that cannot be associated with known interactions, so that the raised force apparently has not been completely elucidated by current theories. We measured such variations within an accurate range and we proposed that the experimental results can be explained by relations like Clausius-Mossotti one, in order to quantify the dipole forces that appear in the devices. The values of the weight losses in the capacitors were calculated by means of the theoretical proposal and indicated good agreement with our experimental measurements for 7kV and with many other experimental works.

Effect of humidity on melt electrospun polycaprolactone scaffolds

AbstractDirect write melt electrospinning is an additive manufacturing technique used to produce 3D polymer scaffolds for tissue engineering applications. It is similar to conventional 3D printing by layering 2D patterns to build up an object, but uses a high-electric potential to draw out fibres into micron-scale diameters with great precision. Direct write melt electrospinning is related to a well-established fabrication technique, solution electrospinning, but extrudes a melted polymer in a controlled manner rather than a polymer solution. The effect of environmental conditions such as humidity has been extensively studied in the context of solution electrospinning; however, there is a lack of similar studies for direct write melt electrospinning. In this study, melt electrospun polycaprolactone scaffolds were produced with 90 degree cross-hatch architecture at three specific humidity [

ELECTRICAL POTENTIAL AND ELECTRICAL FIELD DISTRIBUTION OF SQUARE ELECTRICAL CAPACITANCE TOMOGRAPHY

Electrical Capacitance Tomography (ECT) system helps user to understand the flow distribution inside the close pipe by detecting the variation of permittivity distribution in the inspection area. Generally, most reported ECT systems are implemented to circular shape pipe only. However, square shape pipes are sometimes found in power industry and chemical reactor, therefore this paper is studying the electrical distribution of ECT system within a square pipe. ECT is able to provide fast response, low cost and non-radiation system but similar to all other electrical tomography system, ECT suffers from soft-field effect. This paper proposes segmentation excitation to overcome this problem. Segmentation excitation applies when more than one electrode excited at one time. This paper focuses Protocol 2 or 2-electrode excitation for 8-electrode square ECT system. The simulation was done by using COMSOL Multiphysics. The images of the excitations are presented in this paper. The electrical potential is recorded at the center of the system to analyses the strength of the electrical potential. In addition for square ECT system, the corner configuration provides 3.40% higher electrical potential compared to side excitation configuration.

A 128-channel picoammeter system and its application on charged particle beam current distribution measurements.

A 128-channel picoammeter system is constructed based on instrumentation amplifiers. Taking advantage of a high electric potential and narrow bandwidth in DC energetic charged beam measurements, a current resolution better than 5 fA can be achieved. Two sets of 128-channel strip electrodes are implemented on printed circuit boards and are employed for ion and electron beam current distribution measurements. Tests with 60 keV O(3+) ions and 2 keV electrons show that it can provide exact boundaries when a positive charged particle beam current distribution is measured.

Preparation of Porous Nanostructures Controlled by Electrospray

Various solid structures were prepared by electrospray technique. In this process, liquid flows out from a capillary nozzle under a high electrical potential and is subjected to an electric field, which causes elongation of the meniscus to form a jet. In our study, by controlling the amount of polyvinyl pyrrolydone in precursor solution, the jet either disrupted into droplets for the formation of spherical particles or was stretched in the electric field for the formation of fibers. During the electrospray process, the ethanol solvent was evaporated and induced the solidification of precursors, forming solid particles. The evaporation of ethanol solvent also enhanced the mass transport of solutes from the inner core to the solid shell, which facilitated fabrication of porous and hollow structure. The network structures were also prepared by heating the collector.

Power generation performance of direct flame fuel cell (DFFC) impinged by small jet flames

This paper investigated the effect of cell temperature and product species concentration induced by a small jet flame on the power generation performance of a direct flame fuel cell (DFFC). The cell is placed above the small-scale jet flame and the heated product’s gases are impinged toward it. This system is considered to be the simplest and smallest unit of such power generation devices to have been developed. Methane is used as fuel and an equivalence ratio () of the mixture (with oxygen) and the distance between the cell and the burner surface (d) are considered as the experimental parameters. It turns out that open circuit voltage increases linearly with the increase of temperature in a wide range of equivalence ratios. However, it increases drastically to the point at which the equivalence ratio becomes small enough ( ⩽ 2.0 in the present study) within the specific distance range to bring about the appearance of an inner flame. This could provide sufficient heat and oxygen for the anode, contributing to the generation of the cell’s high electric potential. It is also noted that the appearance of the inner flame does not promise to better the performance unless the preferred conditions (high temperature, low oxygen, rich fuel) near the cell are achieved. The Nernst equation works well for predicting the open circuit voltage under the conditions studied. Systematic design of the entire power generation system is preferable when a miniaturized power generation system is considered by applying DFFC.

A Plasma Spray Coating for Titanium Particles Using Software Simulation

In the present study, a plasma spray coating for titanium particles was studied using software simulations. The governing equations to solve the velocity and temperature distributions of plasma flow and titanium particles considered the effects of electric/magnetic inductions. Seven controlling factors were included in order to investigate their effects on the velocity and temperature of titanium particles colliding with the specimen substrate and the colliding scope of the effective particle depositions. The velocity and temperature distributions of the plasma flow predicted in the present study were expressed in a power form. The results predicted by the present governing equations were thus trustworthy. In general, either a small particle diameter in collaboration with a low electric potential or a large particle diameter in collaboration with a high electric potential is advantageous for a high melting and boiling points.