Effects Of Different Current Densities Research Articles

Enhancement of Structural and Optical Characteristics of Nanostructured InGaN Using Electrochemical Etching

In this work, we used an alternating current electrochemical etching technique to fabricate nanostructured InGaN in potassium hydroxide, which serves as an electrolyte. The effects of different current densities during alternating current electrochemical etching on the morphological and optical characteristics of the nanostructured InGaN samples were investigated. The morphology of the nanostructured InGaN samples was determined by extreme high resolution field emission scanning electron microscopy. The pore size (~38 nm) and estimated porosity (~35%) were highest at 250 mA/cm2 current density. Furthermore, the surface roughness and average pore depth of the nanostructured InGaN increased with increasing current density, as revealed by atomic force microscopy. X-ray diffraction data showed a reduction in the full width at half maximum value and dislocation density of the nanostructured InGaN samples. The InGaN-like E2(high) phonon mode of the nanostructured InGaN sample was shifted to a higher frequency in the Raman spectra relative to that of the untreated sample, indicating that stress relaxation occurs in the nanostructured samples. Raman spectra showed an increase in intensity of the nanostructured InGaN samples showing improvement in optical property. The observed properties illustrate the potential of using nanostructured InGaN application in sensing devices.

Effect of the Current Density on the Electrodeposition Efficiency of Zinc in Aqueous Zinc‐Ion Batteries

AbstractIncreasing the electrodeposition efficiency of metallic zinc from quasi‐neutral aqueous electrolytes is one of the major key requirements for the commercialization of rechargeable aqueous Zn‐ion batteries. Several strategies have been recently reported in the literature. Unfortunately, electrochemical studies on the effect of different current densities on the zinc electrodeposition efficiency usually are not recorded in realistic experimental conditions: e. g. depth of discharges <1–10 %, use of negative electrodes with infinite reservoir of Zn2+, etc. Here, the effect of the current density on the zinc electrodeposition onto optimized bismuth‐indium substrates cycled with 33 % of depth of discharge in a ZnSO4‐containing aqueous solution has been investigated. It was found that low Zn plating/stripping current densities displayed higher electrodeposition efficiencies over 200 Zn electrodeposition/dissolution cycles, more homogeneous distribution of the zinc deposits and lower amounts of inactive zinc passivation products. When higher current densities were applied during the Zn plating/stripping cycles, lower electrodeposition efficiencies and a greater amount of inactive zinc hydroxides and dead zinc were observed on the electrode surface.

Preparation and mechanism analysis of nano-Mg(OH)2 by electroconversion of MgCl2

The preparation and application of porous laminated nanomaterials have been widely concerned because of their large surface area, abundant active sites, and enhanced mass transmission and diffusion. This study used a simple and economical method to synthesize metal hydroxide by the cationic membrane electroconversion synthesis method (CMESM). However, CMESM is not a typical metal electrodeposition process, it is a pseudoelectrolysis process, there is no gain or loss of metal electrons, but metal deposits will be generated. Therefore, its mechanism cannot be studied by conventional electrochemical methods. Thus, we change the research ideas, take the cheap and easy-to-obtain MgCl2·6H2O as raw material, use the chemical precipitation method and the cation membrane permeation method as comparative experiments, study the effect of different current densities on the product, and discuss the mechanism of CMESM. The results show that the Mg(OH)2 nanosheets are electric field induced and assembled into a three-dimensional porous layered petal structure with a large specific surface area and aperture. The metal hydroxides with low cost and high purity can be prepared by cationic membrane electrolytic synthesis.

The multi-functional system of electrochemical desalination, RhB degradation and Cr (VI) removal

ABSTRACT Capacitive deionisation (CDI), as a novel electrochemical technology, has attracted a fast-growing research interest over the past years. However, the single function of salt removal limits further development of conventional CDI systems. Herein, we propose a multi-function CDI device, which can achieve the electrochemical desalination, degradation of organic pollutants and removal of heavy metal ions through the redox electrocatalytic deionisation technology. Sulphur-doped reduced graphene oxide (S@rGO) is utilised as the anode to catalyse the degradation of rhodamine B. The Pt-coated graphite paper is used as a cathode for the removal of dichromate ions by the electro-reduction process. The voltage plateau of S@rGO is reduced by ∼0.35 V compared with the pure carbon cloth electrode, indicating the effectiveness of S@rGO as the catalyser. The salt feed is desalted to ∼0.74 mS·cm−1 level at a current density of 1 mA·cm−2. The degradation efficiency of rhodamine B (RhB) and potassium dichromate are 99.1% and 55.3%, respectively. The effects of different current densities and cycling are also investigated. This work is significant for the multi-functional process of water treatment and the device design. Synopsis : The single function of salt removal limits the further development of the CDI system. A multi-function CDI device is proposed to achieve electrochemical desalination, organics degradation and dichromate ion removal.

Detection of radicals produced during electro-oxidation of atrazine using commercial DSA®-Cl2 in methanol media: Keys to understand the process

This work reports the radicals detected and identified during the degradation of atrazine in methanol medium in the presence and absence of different proportions of water (0%, 5%, and 10%). The determination of these radicals is an important step to understand the electrolysis processes in methanol medium and contribute to clarify the degradation mechanism. Furthermore, the parameters for the successful removal of the contaminant were optimized and the results showed that the application of the technique led to the removal of nearly 99.8% of atrazine after 1 h of electrolysis. The oxidation kinetics was found to be very fast and most of the atrazine molecule in the medium was degraded in the first hour of electrolysis. The results obtained from a thorough analysis conducted with a view to evaluating the effects of different current densities and initial pH values on atrazine degradation showed that the application of higher current densities resulted in lower energy consumption, as this led to faster removal of atrazine. Additionally, the initial pH of the solution was found to favor the formation of different species of active chlorine. The radicals formed during the electro-oxidation process were detected by electron paramagnetic resonance spectroscopy and include hydroxyl, methoxy and hydroxymethyl. The use of methanol for the degradation of pollutants is a highly promising technique and this work shows that the identification of the different radicals formed in the process can be the key to understanding the degradation mechanism.

Degradation of hexafluoropropylene oxide tetrameric acid (HFPO-TeA) using electrocatalytic ozone technique

Hexafluoropropylene oxide tetrameric acid (HFPO-TeA) is an alternative to perfluorooctanecarboxylic acid (PFOA) and is commonly used in the production of perfluoropolymers. In this study, the performances of ozone oxidation, electrochemical oxidation, and electrocatalytic ozone techniques in the degradation of HFPO-TeA were compared. The experimental results indicated that the electrocatalytic ozone technique was best. The effects of different current densities, ozone concentrations, electrolyte types, and initial pollutant concentrations on HFPO-TeA degradation were investigated. The results showed that the ratio of HFPO-TeA degradation reached 95.9% after electrolysis for 120 ​min for an initial HFPO-TeA concentration of 100 ​mg/L, a reaction volume of 120 ​mL, an applied current density of 10 ​mA/cm2, and an ozone concentration of 20 ​mg/L. The intermediate products detected were hexafluoropropylene oxide dimeric acid [C3F7OCF(CF3)COO−], pentafluoropropionic acid [C2F5COO−], and trifluoroacetic acid [CF3COO−]. The mechanisms involved in HFPO-TeA degradation include direct electron transfer, indirect oxidation mediated by hydroxyl radicals (·OH), and ozone oxidation.

Electrochemical Processes for the Treatment of Hazardous Wastes Exemplified by Electroplating Sludge Leaching Solutions

The solidified landfill disposal of hazardous solid waste such as electroplating sludge in arid/semi-arid areas has potential risks and hazards. In this study, the electrochemical method was used to destroy the structures of metal complexes in electroplating sludge and release metal ions so that the organics were removed by direct mineralization in the anode while the metal was recovered in the cathode. A SnO2/Ti electrode was used as the anode during the electrolysis process. The effect of different current densities (10, 20, 30, 40, 50, 60 A/m2), different pH values (2, 3, 4, 5, 6), and the presence of chloride (0.1 or 0.2 M NaCl) and sulfate (0.1 or 0.2 M Na2SO4) on treatment were investigated. Under the optimal treatment conditions (current density = 50 A/m2, pH = 3), the removal rates of CODCr, TOC, and Ni2+ reached 88.01%, 85.38%, and 97.57%, respectively, with a metal recovery of 97.01%. Further studies showed that active chlorine and active persulfate generated in the presence of chloride and sulfate had less effect on the removal of organics, while hydroxyl radicals played a major role. The dilution of the leachate would be detrimental to electrochemical treatment. The by-products of organic chlorination were produced in low amounts, mainly CHCl3. This method can be used to treat electroplating sludge in various areas to recover valuable metals while removing organic pollutants, complying with the concept of sustainable development. This method provides a new solution for the treatment of metal-containing hazardous solid waste such as electroplating sludge from the perspective of practical application.

Reducing the internal compressive stress of the microelectroformed layer by adjusting the current densities

In the microelectromechanical systems area, micrometal devices can be fabricated by microelectroforming process. However, since the defect mechanism of crystal growth, the electroformed layer suffers from the large internal compressive stress. To reduce the large internal compressive stress, the effects of different current densities on the internal compressive stress are investigated. From the view of dislocation density, the mechanism to reduce the compressive stress by adjusting the current densities has been researched originally. The electroforming experiments were processed by several current densities. The dislocation density was measured by the X-ray diffraction method. The compressive stress was tested by side incline method. The nanocrystal structure was observed by the transmission electron microscopy method. The experimental results show that the dislocation density was decreased along with the decreasing of the current density, as well as the compressive stress. The mechanisms are that the crystal structures including the crystallite size, the microcrystal distortion and the dislocation density can be refined by adjusting the small current densities. Then, the compressive stress becomes lower. This work contributes to fabricate the electroformed layer with low internal compressive stress.

Preparation of CeO2 by ion-exchange membrane electrolysis method

The method of ionic membrane electrolysis was applied to prepare cerium (IV) oxide from cerium (III) chloride aqueous solution. This research focused on the effect of different current densities on electrolytic product. The results indicated that the method of ion-exchange membrane electrolysis was feasible to produce pure CeO2 particles with the chlorine content of lower than 0.020%. Under the conditions of this study, when the current density changed from 100 mA·cm−2 to 400 mA·cm−2, the current efficiency of CeO2 decreased monotonically from about 89.0% to 75.0%, the median particle sizes (D50) of CeO2 samples were about 9 μm~24 μm. After 1.5 h of roasting at 800 °C, the crystals of CeO2 continued to grow, and the roasted product was still CeO2, whose particle size of D50 increased from about 17 μm (before roasting) to 27 μm (after roasting). Additionally, it was obvious that the crystal after roasting was composed of nano-sized spherical particles.

Electrochemical Milling of TB6 Titanium Alloy in NaNO3 Solution

Owing to its high tensile strength and toughness, TB6 titanium alloy has been widely used in aerospace applications. However, the machining of TB6 titanium alloy via traditional processes is inefficient as a result of significant tool wear and the prolonged machining cycle. Electrochemical machining is suitable for processing TB6 titanium alloy as it does not cause tool wear or thermal deformation. However, few researchers have conducted an in-depth study of the electrolytic processing of TB6 titanium alloy with the widely used NaNO3 solution. Some researchers have even suggested that TB6 titanium alloy cannot be processed by electrolysis in NaNO3 solution. This paper focuses on the electrochemical machining of TB6 titanium alloy in NaNO3 solution. To explore the effect of the electrochemical parameters on the dissolving behavior of TB6, anodic polarization curves were analyzed. The experimental results show that efficient electrochemical dissolution can be obtained in 20% NaNO3 solution. In addition, the effects of different current densities and processing times on the surface composition and morphology of TB6 titanium alloy were investigated. An electrochemical dissolution characteristic model was proposed to illustrate the dissolution process of TB6 titanium alloy. Finally, grooves and flat surfaces were produced successfully by electrochemical milling.

Role of current density in the degradation of LiNi0.6Co0.2Mn0.2O2 cathode material

The effect of different current density on the structure transformation of LiNi0.6Co0.2Mn0.2O2 material is studied under a cut-off voltage (4.6 V). It shows that the capacity fading is accelerated at the high discharge current density. It is mainly caused by the structure instability of the material. When the current density increases, the loss of lithium on the surface of the material becomes severe, and the oxidation state becomes higher. The unit cell parameters also change, parameter a becomes larger, while the c becomes smaller. At the same time, the high discharge current density has a catalytic effect on the structural transformation, and in terms of high charging voltage, the surface structure changes to a rock salt phase. The cathode material is covered by a 3-nm-thick and discontinuous rock salt phase after cycling 50 times at the current density of 100 mA g−1. However, when the material is cycled at the current density of 1000 mA g−1, the rock salt phase becomes thicker (5∼7-nm-thick) and more continuous, which leads to a fast capacity fading.

Effect of Current Density on Microstructure and Corrosion Behavior of Plasma Electrolytic Oxidation Coated 6063 Aluminum Alloy

Plasma electrolytic oxidation (PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2 on the microstructure and corrosion behavior of coatings was comprehensively studied by scanning electron microscopy (SEM), stereoscopic microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. It is found that the pore density decreases and the pore size increases with increasing current density. The XRD results show that the coatings are only composed of α-Al2O3 and γ-Al2O3. Potentiodynamic polarization test proves that the coating formed under 10 A/dm2 possesses the best anticorrosion property. The long time EIS test shows that the coating under 10 A/dm2 is able to protect the aluminum alloy substrate after long time of immersion in 0.59 M NaCl solution, which confirms the salt solution immersion test results in 2 M NaCl solution.

Electromigration behaviors in Sn–58Bi solder joints under different current densities and temperatures

Sn–58Bi eutectic solder is attracted much attention to replace Sn–Ag–Cu Pb-free solder due to its lower melting temperature in recent years. However, its low melting temperature also raised serious electromigration (EM) reliability due to the accelerated atomic migration from the high local temperature induced by Joule heating. This paper mainly studied the EM behaviors occurred in Sn–58Bi solder joints with consideration the effect of different current densities and temperature. Variation on the atomic migration and phase coarsening were observed in Sn–58Bi solder joint, and the threshold current densities to trigger EM damage were estimated. The results showed that Bi-rich layer was produced at anode side during stressing with low current density while caused Cu cathode to dissolve into Sn–Bi solder and formed Cu6Sn5 intermetallic compounds near anode side during stressing with high current density. Accordingly, the corresponding dominant diffusing species in Sn–58Bi solder were Bi atoms at low temperature and Cu and Sn atoms at high current density, respectively. High temperature applied with EM accelerated the atomic migration. The threshold current densities at different temperature were then calculated from the thickness of Bi-rich layer at anode side. There existed a lower threshold current density at higher temperature due to the active atomic mobility. Finally, Bi phase coarsening was observed in Sn–Bi solder under different current densities and temperatures. Higher current density or higher temperature induced faster grain growth, but the applied current had a greater effect on Bi phases coarsening in Sn–Bi solder matrix than the applied temperature. The controlling kinetics on the growth of Bi phases were also suggested for the effect of current densities and temperatures.

High-speed and high-quality TSV filling with the direct ultrasonic agitation for copper electrodeposition

In this paper, the influential factors of the silent and ultrasonic electroplating using 3-mercapto-1-propanesulfonate (MPS), polyethylene glycol (PEG), and Polyethylenimine alkyl salt (PN) on the TSV filling are investigated. The effects of different accelerator concentration, current density and ultrasonic agitation on TSV filling are studied. The accelerative effect of MPS on TSV filling by the copper electrodeposition is studied to find out the optimal condition of the accelerator concentration. Using the plating bath with same additive conditions, the effects of different current densities on the TSV filling under the silent and ultrasonic conditions are investigated. The results show that the quality of TSV filling under ultrasonic electroplating has improved by 23% compared with the silent condition at the same current density.

Jet electrodeposition of nanocrystalline nickel assisted by controllable friction

Abstract A controllable friction auxiliary method (CFAM) was developed to improve the quality of a coating surface prepared through flexible friction-aided jet electrodeposition (FFAJED) at a high current density. A rolling nozzle was also designed. This nozzle can provide controlled pressure constantly during deposition so that the proposed method can forcibly restrain the rapid growth of the coarse grains. The influence of different pressures and cathode scanning speeds on coating surface quality was discussed, and the optimum parameters of the method were determined. With the optimum parameters, the effect of different current densities on coating surface quality was studied. Results show that when the rolling pressure is 5 N and the scanning speed of the cathode is 860 mm/min, the surface quality of the coating is excellent. No obvious coarse grains, defects (e.g., pinhole or nodules), and apparent traces of friction were observed. The magnetic properties of Ni coating were improved too. The upper limit of current density in the preparation of Ni coating by CFAM reached 200 A/dm2, which is 1.54 times that of traditional jet electrodeposition (130 A/dm2) and 1.43 times that of FFAJED.

The Effect of Current Density to Surface Morphology and Component of Micro-Arc Oxidization Ceramic Coating of Pure Titanium

The ceramic coating containing anatase TiO2 and rutile TiO2 is fabricated on the surface of pure titanium in the electrolyte of C4H6CaO4-NaH2PO4 by micro-arc oxidation (MAO) method. The effect of different current density to microscopic structure, elemental composition and phase components of Ceramic Coating are studied with scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), 3D profilometer and etc. Results indicate that the ceramic coating on pure titanium by micro-arc oxidation is a porous mixed crystal structure which is mainly composed of such elements as Ti, O, Ca and P. With current density increasing, the average pore diameter and roughness on film surface first increase and then decrease, the porosity increases, the ratio of Ca/P then decreases, the relative content of anatase TiO2 increases and that of rutile TiO2 decreases.

A computational study to investigate the effects of the bipolar plate and gas diffusion layer interface in polymer electrolyte fuel cells

In this study, a multi-phase, two-dimensional model that integrates the bipolar plate (BP) and gas diffusion layer (GDL) interfacial morphology was developed to understand the effects of this interface on mass, charge and heat transport and performance of polymer electrolyte fuel cells (PEFCs). Two different case studies were performed. The first case assumes a perfect contact interface between the BP and GDL, whereas in the second case, the BP|GDL interfacial layer was incorporated as a separate domain based on the measured BP|GDL morphology. In the BP|GDL interface case, the interfacial voids were assumed to be filled with liquid water to investigate the role of the interfacial voids. For both cases, the effects of different current densities on the in-plane temperature, saturation, and oxygen concentration distribution in the GDL were investigated. Simulations indicate that the Ohmic and concentration losses are increased due to the inclusion of the realistic BP|GDL interface. The electrical contact resistance contribution of the BP|GDL interface was predicted to be 3.8 mΩcm2. The saturation in the GDL was found to be higher for the BP|GDL interface case, which results in higher concentration losses. The temperature was predicted to be slightly higher for the BP|GDL interface case, which could be attributed to the higher thermal contact resistance due to the fewer contact regions at the interface.

Electrochemical oxidation of ammonia-containing wastewater using Ti/RuO2-Pt electrode

The electrochemical oxidation degradation processes for artificial and actual wastewater containing ammonia were carried out with a Ti/RuO2-Pt anode and a Ti plate cathode. We studied the effects of different current densities, space sizes between the two electrodes, and amounts of added NaCl on ammonia-containing wastewater treatment. It was shown that, after a 30-min treatment under the optimal conditions, which were a current density of 20 mA/cm2, a space size between the two electrodes of 1 cm, and an added amount of 0.5 g/L of NaCl, the COD concentration in municipal wastewater was 40 mg/L, a removal rate of 90%; and the NH3-N concentration was 7 mg/L, a removal rate of 88.3%. The effluent of municipal wastewater qualified for Class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002).

Effect of Different Current Densities in the Studies of 1/f noise on the Thin Films of Silver

Abstract: Silver (Ag) thin films are having remarkable characteristics. They have found extensive applications in electronic and optical devices. Silver thin films have potential applications in ultra-high density optical non-volatile memories, transparent electrodes and in fluorescence imaging. Measurements of nonlinear properties are very interesting from the point of the view of optoelectronic and all optical switches. Hence these films are studied in the present work. 1/f noise and nonlinear effects in Silver thin films for different current densities on varying the thickness of the films, at room temperature are studied. The specific dependence of 1/f noise on the thickness of the film, the effect of current densities on 1/f noise for the films of various thicknesses (430A o to 1180A o ) has been investigated. It is noticed that, for a constant current, the thickness of the film leads to an increase of 1/f noise.1/f noise plays an important role in choosing frequency band in which a device can be effectively used. Silver thin films are regarded as a material with many attracting properties such as good conduction, high transmission coefficient etc. It is specially used in optoelectronic devices.

Effect of Different Current Density on the Performance of Microbial Fuel Cell and Denitrification Activity

Effect of Different Current Density on the Performance of Microbial Fuel Cell and Denitrification Activity