Edge Of Cathode Research Articles

Single–crystalline LiNi0.8Co0.1Mn0.1O2 stabilized by F–doping–induced superlattice for 4.8 V lithium–ion batteries

Single–crystalline Ni–rich ternary layered oxides represent the cutting–edge cathode materials for lithium–ion batteries, offering enhanced cycling stability compared to the polycrystalline counterparts by eliminating grain boundaries. However, their structural stability encounters a significant challenge when operated under high voltages (cut–off charging potential ≥ 4.6 V). Excessive extraction of Li+ ions can lead to the localized collapse of transition metal (TM) slabs and accumulation of lattice dislocations, which hinders Li+ diffusion and eventually cause capacity decay. This study demonstrate that the introduction of F dopants triggers an ordered mixing of Li+ and Ni2+ ions to form a superlattice in single–crystalline LiNi0.8Co0.1Mn0.1O2. This unique F–doping–induced superlattice stabilizes the deintercalated structure through Ni2+ (Li layer)–O2––Ni2+ (TM layer) interlayer super–exchange strong interactions, thereby facilitating the reversible H2–H3 phase transformation during cycling. Consequently, when cycled between 2.8–4.8 V at 1C, the F doped single–crystalline LiNi0.8Co0.1Mn0.1O2 exhibits unprecedented cycling stability, retaining 90.3 % of its initial capacity after 200 cycles, while achieving a high discharge capacity of 186.8 mAh/g and an impressive energy density of 706.5 Wh/kg. This work sheds light on the microstructural engineering for Ni–rich layered cathode materials.

On the formation of dendritic iron from alkaline electrochemical reduction of iron oxide prepared for metal fuel applications

Low-temperature electrochemical reduction (electroreduction) of iron oxides is a promising alternative to the conventional methods for iron production due to its CO2-free operation and relatively low energy consumption. In this work, we demonstrate a novel approach for electrochemical iron production by promoting the formation of dendritic structures during iron electrodeposition, which facilitates the easy harvesting of deposits in powder form. Experiments were conducted using a single pair of parallel plate electrodes, immersed in a mixture of hematite (Fe2O3) powder and aqueous alkaline (NaOH) slurry. The effects of current density, Fe2O3 mass fraction, temperature, and powder size on current efficiency and deposit morphology are investigated. A large quantity of dendritic iron structures is observed when experiments are carried out without stirring and/or applying heat from a heating plate. This condition suggests temperature and (ion/species) concentration gradients in the system. The dendrites are mainly deposited on the cathode's sides, corners, and edges. Different deposits and dendritic structures (compact layer deposit, moss-like deposit, deposit with whisker-like dendrites, and deposit with crystal-like dendrites) are observed as operating conditions change. Overall, a cathodic deposition of metallic iron with a high Faradaic efficiency (≥90 %) is successfully accomplished. The present findings provide new insights into the production of electrolytic iron powder and its future use as a carbon neutral and sustainable fuel/energy carrier.

Investigation of plasma parameters, distributions, and optical emission for the anti-microbial performance of non-woven fabric under direct current glow discharge

The distribution of electron temperature Te and density Ne for direct current glow plasma discharge was investigated, using a single Langmuir probe, inserted inside the plasma cell. The radial temperature distribution has the same values, except with a small increment variation at the cathode edge, and an axial decrement for the temperature Te distribution profiles from the cathode fall region, passing the abnormal glow region, up to the faraway axial region.The radial distribution of the electron density Ne has its highest value at the cathode, with very intense plasma at the cathode fall region, and more Ne decrement in the abnormal glow region, passing the abnormal glow region up to the faraway axial region. In the axial Ne distribution, an increase in Ne from the cathode fall region reaches maximum values in the abnormal glow region and decreases in the faraway axial region.The optimal plasma surface treatment of non-woven silk fabric (n-WSF) can be achieved by utilizing a high plasma density and low energy of electrons to inactivate viable cells attached to (n-WSF) at very short application times, leading to complete inactivation, where the bacterial inactivation rate increases in the abnormal glow region. Based on analyses of the experimental data of initial and final densities of viable cells using survival curves in the abnormal glow discharge region, a dramatic inhibitory effect of plasma discharge on the residual survival microbe ratio was observed.

Relaxation of Electric Field by Covering Cathode Edge With Vanadate Glass

Relaxation of Electric Field by Covering Cathode Edge With Vanadate Glass

Research on depth control of machining trace in electrochemical trepanning

Electrochemical trepanning (ECTr) is a highly effective and economic manufacturing technology for machining difficult-to-cut metal materials that are often used in aeroengine components. Integral structural components such as blisks, diffusers, etc. are composed of hubs and blades. In continuous ECTr, machining trace stems from on the hub between adjacent blades. The depth of machining trace significantly influences the surface integrity of the integrated components, even causes the scrapping of the workpiece. In order to solve the problem of machining trace in ECTr, a cathode design method based on the relation between cathode profile and electric field distribution is proposed in this study, the edge of the cathode that affects the machining trace is chamfered. A electric field model of ECTr is established and dynamic electric field simulation of ECTr for cathodes with different chamfered edges is performed. The electric field intensity distribution at the cathode edge and the forming profile of the hub are compared. The simulation results show that optimal chamfering parameters can improve the machining trace. Subsequently, a group of cathodes with different chamfered edge is designed, and corresponding ECTr experiments are conducted. The optimal chamfering parameters are determined (α = 5°, b = 2 mm), the depth of the machining trace is reduced from 0.370 mm to 0.122 mm, the surface flatness is significantly improved. Overall, this depth control method of machining trace is verified effectively.

Effect of focus ring with external circuit on cathode edge sheath dynamics in a capacitively coupled plasma

Capacitively coupled plasmas are widely used in semiconductor processes. The control of plasma to obtain uniform deposition and etching is an open problem, particularly within a few millimeters of the substrate edge. Complex material stacks commonly referred to as focus rings are placed at the wafer edge to provide uniform processes across the entire substrate but have limitations with regard to process window and eventual material erosion. One approach is to combine a focus ring with a tunable external circuit ground path termination to extend the plasma uniformity to the wafer edge over a wider process space. The external circuit coupling focus ring to the ground influences the ion energy profile and the ion angular profile by changing the impedance between the focus ring and the ground and allows wafer edge tuning over a wide range of operating parameters. In this work, it is found that the adjustable external circuit can control the partitioning of bias and RF voltages between the RF powered and passively coupled plasma facing surfaces. The focus ring with an external circuit assembly can also control the spatial distribution of plasma density and, therefore, improve the sheath edge profile. These results point to possible source designs for engineering the distribution of power dissipation and the electric field of the wafer edge in industrial plasma reactors.

Simulation study of vertical diamond Schottky barrier diode with field plate assisted junction termination extension

In this paper, we designed vertical diamond Schottky barrier diodes with a field plate assisted junction termination extension (FP-JTE) structure by using Silvaco TCAD. It demonstrates that the JTE structure is more effective to suppress the electric field crowding around the electrode edges than the FP, but it also increases the on-resistance due to the decreasing conduction area. Then, the FP-JTE diamond SBDs are designed to realize the trade-off between the breakdown voltage and on-resistance. It is found that the JTE length should be shorter than the FP to enhance the current conduction, but it needs to cover the cathode edge to suppress the electric field crowding. We also confirm that the FP-JTE SBDs with the JTE length increase from the sidewall toward the center are recommended to take advantage of both FP and JTE structures.

Visualizing the effects of salt concentration in planar polymer light-emitting electrochemical cells

The effects of salt concentration have been visualized in bilayer, planar polymer light-emitting electrochemical cells (PLECs) with a gap size of 2 mm. Electrochemical doping and junction electroluminescence (EL) have been observed in a luminescent conjugated polymer (CP) top layer with a different solid polymer electrolyte (SPE) underlayer. By varying the salt concentration and thickness of the SPE layer, the initial cell current, peak cell current, doping propagation speed and junction formation time can all be altered/controlled. This is explained by a limiting ionic resistance in the SPE layer which is both salt concentration and thickness dependent. This study establishes the role of electrolyte ions to support doping current in PLECs. The unexpected observation of a systematic junction shift towards the cathode suggests the electrolyte ions, when functioning as counter ions for doping, are also affected by the salt concentration. At high salt concentrations, the light-emitting junction overlaps with the cathode edges which is undesirable. Thus, the bilayer PLECs allowed for the study and visualization of functions of mobile ions in PLEC operation. Moreover, the bilayer PLECs can potentially be used to study the SPE layer itself using highly sensitive imaging techniques.

Design methodologies and fabrication of 4H-SiC lateral Schottky barrier diode on thin RESURF layer

This paper discusses the design methodologies and fabrication of a 4H-SiC lateral reduced surface electric field (RESURF) Schottky barrier diode (SBD), using a very thin (0.7 μm) RESURF layer. The proposed optimization of the anode and cathode edge structure with recessed etch into mesa termination minimizes the electric field induced impact ionization at the edge of the active area. Three-dimensional simulations were conducted to optimize electric field distribution and enable close to ideal RESURF breakdown voltage within the device, while enabling junction isolation structure between neighboring devices through mesa etch. The design methodologies and the fabricated lateral SBD offer guidance for future efforts toward realizing a monolithic SiC high voltage integrated circuit.

Effects of anisotropic surface drift diffusion on the strained heteroepitaxial nanoislands subjected to electromigration stressing

A systematic study based on self-consistent dynamical simulations is presented for the morphological evolutionary behavior of an isolated thin Ge/Si nanoisland (quantum dot) on a rigid substrate exposed to electromigration forces. This morphological evolution is basically induced by the anisotropic surface drift diffusion, driven by the capillary forces, the lattice mismatch stresses, and the wetting potential. In this study, we have mainly focused on the size and shape development kinetics of quantum dots, known as the “Stranski–Krastanov” (SK) morphology, influenced by applied electromigration stresses. Emphasis is given to the effects of rotational symmetry associated with the anisotropic diffusivity in 2D space (i.e., quantum wires in 3D). The pointed bullet-shaped “Stranski–Krastanov” islands with high aspect ratios, ξ = 0.77, are formed at the cathode edge, while the whole nanoisland slightly creeps out of the initial computational domain. The favorable configuration of the Ge20/Si80 alloy test module, which resulted in ζ = 0.37 enhancement in the contour surface area, has a dome shape attached to the [010] top surface of the Si substrate with a zone axis of {010}/⟨001⟩. The anisotropic surface diffusion dyadic has a fourfold rotational symmetry axis [001] lying on the (001) plane of the Si substrate, and its major axis is tilted at about ϕ = 45° from the applied electrostatic field extended along the longitudinal axis [100] of the substrate. This particular experiment resulted in a SK singlet peak with a small satellite with a very small aspect ratio of ≅0.2 that may be appropriate for the conception of quantum optoelectronic devices or inter-band structures to generate photoelectrons having large energy spectra, thereby increasing the efficiency of photovoltaics exposed to solar radiations.

Emission Features and Structure of an Electron Beam versus Gas Pressure and Magnetic Field in a Cold-Cathode Coaxial Diode

The structure of the emission surface of a cold tubular cathode and electron beam was investigated as a function of the magnetic field in the coaxial diode of the high-current accelerator. The runaway mode of magnetized electrons in atmospheric air enabled registering the instantaneous structure of activated field-emission centers at the cathode edge. The region of air pressure (about 3 Torr) was determined experimentally and via analysis, where the explosive emission mechanism of the appearance of fast electrons with energies above 100 keV is replaced by the runaway electrons in a gas.

Factors Affecting the Cathode Edge Nodulation in Copper Electrorefining Process

In this study the factors that are affecting the copper nodular growth on the cathode edge were investigated from metallurgical and operation point of view. Statistical analysis was performed to evaluate the effect of operational conditions on the nodular copper growth by characterization of the nodule-containing cathodes. Besides, the effects of defects on polymer edge strips as well as changes in weight and thickness of anodes on the formation of nodules were investigated. Electrochemical galvanostatic experiments were employed to study the effect of electrolyte additives and the distance between the anode and cathode on cathode surface quality. A relatively large porosities of about 50 µm were observed in the microstructure of the cathode edge nodules. In addition, few nodule samples that were taken was observed to have a higher concentration of Fe, Cd and Pb, up to 25 ppm. Low probability (1%) in the repeatability of the nodule formation over the same position on the edge strip was approved the insignificant effect of possible edge strip defects on nodulation. The large weight variation of anodes can cause the anode thickness variation by 10 mm and consequently alter the distance between the anode and the cathode. This was shown to cause formation of nodules at the cathode edge. The peaks that were observed in the cathodic potential curves in galvanostatic tests, were believed to be the sign of nodulation and therefore was investigated further using the optical microscopic images.

Photocatalytic Reduction of Aromatic Nitro Compounds with Ag/AgxS Composites under Visible Light Irradiation

A series of silver sulfide composites were prepared via the hydrothermal method with l-cysteine and AgNO3 in water at a range of l-cysteine/AgNO3 molar ratio of 0.5–8. The prepared Ag/AgxS materials were consisted of Ag, Ag2S, Ag2S2, and Ag2Sn species as confirmed by XRD, TEM, and XPS. The Ag/AgxS composites are active for the photocatalytic reduction of aromatic nitro compounds under the visible light irradiation. The composition of the stoichiometric Ag2S, the nonstoichiometric Ag2S2 and Ag2Sn, and metallic Ag species affected the photocatalytic performances largely. When more nonstoichiometric Ag2S2 and Ag2Sn presented on the surface, the absorption in the visible (vis) light region was enhanced remarkably and presented a blue shift, leading to a bigger band gap energy value (Eg) and higher cathodic conduction band edge potential (ECB), which promoted the formation of photogenerated electrons and inhibited the combination of photoelectrons and holes. When the more Ag0 presented on the surface, the more photogenerated electrons were transferred from the conduction band of AgxS to Ag0, preventing the combination of photoelectrons and holes. Thus, the photocatalytic performances of the Ag/AgxS composites could be controlled by varying the surface composition.

Carbon nanostructure growth: new application of magnetron discharge

Purpose: The application of a common magnetron discharge to the growth of carbon nanostructures is studied. The simplicity of the proposed technique can be beneficial for the development of new plasma reactors for large-scale production of carbon nanostructures. Design/methodology/approach: Graphite cathode was treated by carbon-containing powder accelerated by use of nozzle, and then aged in hydrogen. Superposition of glow and arc discharges was obtained, when putting the cathode under the negative biasing with respect to the walls of a vacuum chamber. The pulsed discharge was preserved through the whole time of treatment. This process was explained in terms of interaction of glow discharge plasma with a surface of the cathode made of non-melting material. Findings: The plasma treatment resulted in generation of the diverse nanostructures confirmed by SEM and TEM images. Spruce-like nanostructures and nanofibers are observed near the cathode edge where the plasma was less dense; a grass-like structure was grown in the area of “race-track”; net-like nanostructures are found among the nanofibers. These findings allow concluding about the possible implementation of the proposed method in industry. Research limitations/implications: The main limitation is conditioned by an explosive nature of nanostructure generation in arcs; thus, more elaborate design of the setup should be developed in order to collect the nanospecies in the following study. Practical implications: High-productivity plasma process of nanosynthesis was confirmed in this research. It can be used for possible manufacturing of field emitters, gas sensors, and supercapacitors. Originality/value: Synthesis of carbon nanostructures is conducted by use of a simple and well-known technique of magnetron sputtering deposition where a preliminary surface treatment is added to expand the production yield and diversity of the obtained nanostructures.

Structure of an Electric Field at the Cathode Edge under ρ-Mode Emission

Structure of an Electric Field at the Cathode Edge under ρ-Mode Emission

Polyacrylonitrile-Based Carbon Fiber as Anode for Manganese Electrowinning: Anode Slime Emission Reduction and Metal Dendrite Control

The traditional lead-based anodes used in industrial electrolysis process trigger the high energy consumption, lead pollution and hazardous anode slime discharge. In this work, an original undecorated Polyacrylonitrile (PAN)-based carbon fiber was employed as anode material (CF anode) to evaluate its electrochemical performance and feasibility, aiming at fundamentally reducing the energy consumption and pollution emissions for the manganese electrolysis. The results shown that the CF anode exhibited excellent electrocatalytic activity and delivered a current density of 350 A m–2 at an overpotential decreased by 112 mV for oxygen evolution reaction (OER) compared with commercial lead-based alloy anode (Pb anode). We also found CF anode exhibited favorable performance with average current efficiency increased by 4.30%, energy consumption decreased by 8.36%, and a noteworthy abatement of anode slime by 80% compared with Pb anode in MnSO4 electrolyte. Additionally, the growth of manganese dendrites on the cathode edge which directly affected the electrolytic efficiency has also been effectively controlled and the possible mechanisms were also discussed. This work displayed the excellent electrocatalytic effect of CF anode serviced as a promising candidate for green and efficient electrolysis process.

The Effect of Different Cathode Configurations of the Plasma Cell on the Ion Velocity Distribution Function

The ion velocity distribution in a plasma source was investigated through a comparison between two different configurations of the cathode of the plasma cell, namely, the one mesh system electrodes (OMSE), and the one mesh and three system electrodes (OMTSE). The velocity ranged from 1 to 3.5 km/s for OMSE and from 4 to 22 km/s for OMTSE. The comparison between the experimental and theoretical ion velocity distribution function (IVDF) of OMSE and OMTSE under the same applied conditions shows a better agreement for OMSE than for OMTSE due to the difference in plasma cell construction, cathode mesh wire configuration, and cathode edge. Even though the velocity and density of ions for the OMTSE reactor are higher than those for the OMSE reactor, the OMSE reactor was found to be the best system to avoid dusty plasma defects through the etching process.

Preliminary experimental research of a Ka-band radial transit time oscillator.

Radial transit time oscillator (RTTO) can be relied on to generate effective coherent electromagnetic radiation in the millimeter wave domain. In this paper, the preliminary experimental research on a Ka-band RTTO is reported for the first time. In experiments, the radial electron beam emitted from the knife edge of the disk cathode is guided by the radial magnetic field. The bombardment trace on the nylon target verifies the emission and transportation uniformity of the radial e-beam. When the diode voltage is 410 kV, the beam current is 7.8 kA, and the magnetic field is 0.6 T, the RTTO can output microwaves with the power of 320 MW and the frequency of 31.35 GHz. As the diode voltage increases from 350 kV to 430 kV, the output microwave power will grow accordingly. Taking the ohmic loss into consideration, the experimental results are in agreement with the simulation ones.

Enhanced transcutaneous electrical nerve stimulation achieved by a localized virtual bipole: a computational study of human tibial nerve stimulation

Objective. Electrical neuromodulation is a clinically effective therapeutic instrument, currently expanding into newer indications and larger patient populations. Neuromodulation technologies are also moving towards less invasive approaches to nerve stimulation. In this study, we investigated an enhanced transcutaneous electrical nerve stimulation (eTENS) system that electrically couples a conductive nerve cuff with a conventional TENS electrode. The objectives were to better understand how eTENS achieves lower nerve activation thresholds, and to test the feasibility of applying eTENS in a human model of peripheral nerve stimulation. Approach. A finite element model (FEM) of the human lower leg was constructed to simulate electrical stimulation of the tibial nerve, comparing TENS and eTENS. Key variables included surface electrode diameter, nerve cuff properties (conductivity, length, thickness), and cuff location. Enhanced neural excitability was predicted by relative excitability (RE > 1), derived using either the activating function (AF) or the nerve activation threshold (MRG model). Main results. Simulations revealed that a localized ‘virtual bipole’ was created on the target nerve, where the isopotential surface of the cuff resulted in large potential differences with the surrounding tissue. The cathodic part (nerve depolarization) of the bipole enhanced neural excitability, predicted by RE values of up to 2.2 (MRG) and 5.5 (AF) when compared to TENS. The MRG model confirmed that action potentials were initiated at the cathodic edge of the nerve cuff. Factors contributing to eTENS were larger surface electrodes, longer cuffs, cuff conductivity (>1×103 S m−1), and cuff position relative to the cathodic surface electrode. Significance. This study provides a theoretical basis for designing and testing eTENS applied to various neural targets and data suggesting function of eTENS in large models of nerve stimulation. Although eTENS carries key advantages over existing technologies, further work is needed to translate this approach into effective clinical applications.

Visualization Analysis of Pt and Co Species in Degraded Pt3Co/C Electrocatalyst Layers of a Polymer Electrolyte Fuel Cell Using a Same-View Nano-XAFS/STEM-EDS Combination Technique.

In order to obtain a suitable design policy for the development of a next-generation polymer electrolyte fuel cell, we performed a visualization analysis of Pt and Co species following aging and degradation processes in membrane-electrode assembly (MEA), using a same-view. Nano-X-ray absorption fine structure (XAFS)/Scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDS) technique that we developed to elucidate durability factors and degradation mechanisms of a MEA Pt3Co/C cathode electrocatalyst with higher activity and durability than a MEA Pt/C. In the MEA Pt3Co/C, after 5000 ADT-rec (rectangle accelerated durability test) cycles, unlike the MEA Pt/C, there was no oxidation of Pt. In contrast, Co oxidized and dissolved over a wide range of the cathode layer (∼70% of the initial Co amount). The larger the size of the cracks and pores in the MEA Pt/C and the smaller the ratio of Pt/ionomer of cracks and pores, the faster the rate of catalyst degradation. In contrast, there was no correlation between the size or Co/ionomer ratio of the cracks and pores and the Co dissolution of the MEA Pt3Co/C. It was shown that Co dissolved in the electrolyte region had an octahedral Co2+-O6 structure, based on a 150 nm × 150 nm nano-XAFS analysis. It was also shown that its existence suppressed the oxidation and dissolution of Pt. The MEA Pt3Co/C after 10,000 ADT-rec cycles had many cracks and pores in the cathode electrocatalyst layer, and about 90% of Co had been dissolved and removed from the cathode layer. We discovered a metallic Pt-Co alloy band in the electrolyte region of 300-400 nm from the cathode edge and square planar Pt2+-O4 species and octahedral Co2+-O6 species in the area between the cathode edge and the Pt-Co band. The transition of Pt and Co chemical species in the Pt3Co/C cathode electrocatalyst in the MEA during the degradation process, as well as a fuel cell deterioration suppression process by Co were visualized for the first time at the nano scale using the same-view nano-XAFS/STEM-EDS combination technique that can measure the MEA under a humid N2 atmosphere while maintaining the working environment for a fuel cell.