Pulsed Current Technique Research Articles

Electrodeposition of thin poly(propylene glycol) acrylate electrolytes on 3D-nanopillar electrodes

Solid polymer electrolytes consisting of poly(propylene glycol) diacrylate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were deposited onto Cu2O-coated 3D Cu nano-pillars through cathodic electropolymerization. Electropolymerization, using constant and pulsed current techniques, was used to produce polymer coatings directly onto 3D substrates with thicknesses down to nano-scale dimensions. SEM confirmed that pulsed current deposition is comparatively beneficial for producing uniform and conformal electrolyte coatings along the nano-pillar structure. ATR/FTIR studies of the electropolymerized electrolytes showed that the degree of polymerization in the electrolyte can be increased by a heating treatment after synthesis. XPS analysis confirmed the presence of co-deposited LiTFSI salt in the polymer layer during electropolymerization. The ionic conductivity of the obtained electrolytes was characterized by EIS and is in the order of 10−6 S cm−1 at room temperature. This work demonstrates that the electrolyte coated on the nano-pillar electrodes may serve as a template for further deposition of electrode materials for the assembly of 3D-microbattery whole-cells.

Influence of the electrodeposition current regime on the corrosion resistance of Zn–CeO2 nanocomposite coatings

The present work aims at studying the influence of the current regime on the electrodeposition of zinc–ceria composite coatings obtained from a chloride based electrolyte, by using both direct and pulse current electrodeposition techniques. The microstructure, microhardness, composition profile and the corrosion parameters of the samples were evaluated via SEM, GDOES, microhardness tests and polarization curves, respectively. Pure zinc samples obtained under the same experimental conditions were used as a reference. The addition of CeO2 nanoparticles leads to finer grained deposits, with better corrosion resistant properties. The study also revealed that a pulsed-current regime is preferable to a direct-current approach of the electro-co-deposition process, leading to coatings with better anti-corrosion properties.

Pore-arrayed hydrogen molybdenum bronze: Preparation and performance as support of platinum nanoparticles for methanol oxidation

A novel electrocatalyst for methanol oxidation is fabricated by decorating platinum nanoparticles on pore-arrayed hydrogen molybdenum bronze (HxMoO3). In this fabrication, pore-arrayed HxMoO3 is prepared with polystyrene monolayer as a template, and platinum nanoparticles are decorated on the resulting pore-arrayed HxMoO3 by using a current pulse technique. The fabricated electrocatalyst is investigated with a combination of physical characterizations from X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy, and electrochemical measurements including cyclic voltammetry, chronopotentiometry, chronoamperometry, and cell discharge test. It is found that the platinum decorated on pore-arrayed HxMoO3 (Pt/p-HxMoO3) is more uniform, has smaller particle size and exhibits improved electrocatalytic activity and stability for methanol oxidation, compared to that on non-pore-arrayed HxMoO3 (Pt/HxMoO3). The peak current for methanol oxidation in cyclic voltammetry is improved from 4.89 mA cm−2 for Pt/HxMoO3 to 6.41 mA cm−2 for Pt/p-HxMoO3, and the time for abrupt potential change in chronopotentiometry is enhanced from 498 min for Pt/HxMoO3 to 576 min for Pt/p-HxMoO3. The improved performance is attributed to the larger specific surface area of the pore-arrayed HxMoO3, which favors the formation of smaller Pt nanoparticles.

Combined current-modulation annealing induced enhancement of giant magnetoimpedance effect of Co-rich amorphous microwires

We report on a combined current-modulation annealing (CCMA) method, which integrates the optimized pulsed current (PC) and DC annealing techniques, for improving the giant magnetoimpedance (GMI) effect and its field sensitivity of Co-rich amorphous microwires. Relative to an as-prepared Co68.2Fe4.3B15Si12.5 wire, CCMA is shown to remarkably improve the GMI response of the wire. At 10 MHz, the maximum GMI ratio and its field sensitivity of the as-prepared wire were, respectively, increased by 3.5 and 2.28 times when subjected to CCMA. CCMA increased atomic order orientation and circumferential permeability of the wire by the co-action of high-density pulsed magnetic field energy and thermal activation energy at a PC annealing stage, as well as the formation of uniform circular magnetic domains by a stable DC magnetic field at a DC annealing stage. The magnetic moment can overcome eddy-current damping or nail-sticked action in rotational magnetization, giving rise to a double-peak feature and wider working field range (up to ±2 Oe) at relatively higher frequency (f ≥ 1 MHz).

Effect of Oxygen Content in WC-FeAl Powders on Microstructure and Mechanical Properties of Sintered Composites Fabricated by Pulse Current Sintering Technique

Effect of Oxygen Content in WC-FeAl Powders on Microstructure and Mechanical Properties of Sintered Composites Fabricated by Pulse Current Sintering Technique

パルス通電焼結法により作製したWC–FeAl 複合体の組織と 機械的特性に与える粉末中の酸素量の影響

The effect of oxygen content in WC–FeAl powder is examined on mechanical properties of the sintered composites. The oxygen content is varied by controlling the milling and/or drying processes of the WC–FeAl mixed powder. The WC–FeAl composites are obtained by sintering the mixed powders with the pulse current sintering technique. Transverse rupture strength is improved by reducing the oxygen content in the mixed powder whereas the difference of microstructure and composition is not observed clearly. Some results suggest that oxidation of FeAl during the preparation of the WC–FeAl mixed powder affects the mechanical properties of WC–FeAl products. It is concluded that oxygen content is very important for controlling the mechanical properties of WC–FeAl products.

The Study to the Corrosion of Reinforcing Steel in Concrete by Using Galvanostatic Pulse Technique

This paper presents the result from a study of Galvanostatic Pulse Technique for determining the corrosion rate of steel in reinforced concrete. The investigation to the condition factors and instrument parameter that significantly influence the testing result of the current pulse technique in on-site measurements is made in this paper. Firstly standard specimens which have different thickness of concrete cover and NaCl adding content were prepared, and instruments (CorroMap TM) for field measurement of corrosion rate of steel in reinforced concrete are selected for testing. From the study we can conclude that Icorr increased with the decreasing of the thickness of the concrete cover and the adding content of NaCl to the concrete when casting with non-linear rule, and an anodic pulse of 50 μA with pulse duration of 10 seconds is appropriate for testing both passive and active area of rebar.

Characterisation of tungsten coatings by pulsed current plating from molten salt in air atmosphere

Pure and compact tungsten coatings with high (200)-orientation were successfully electrodeposited from Na2WO4–WO3 binary oxide molten salt by direct and pulse current techniques on copper based alloy substrate in air atmosphere at 1173 K. The tungsten coatings and copper alloy substrates combined well with no obvious voids and cracks. In addition, the influence of pulse plating on the microstructure, crystal structure and Vickers microhardness of coatings, adhesive strength between coatings and substrates as well as the current efficiency was investigated. It was also observed that applied pulse current led to tungsten coatings with better mechanical properties than those obtained by direct current plating. In addition, a tungsten coating of 500 μm which had lower oxygen content and higher adhesive strength than the coating obtained by the plasma spray method was obtained.

Relationship between hardness and fracture toughness in WC–FeAl composites fabricated by pulse current sintering technique

WC–FeAl composites having notable mechanical properties as hard metal materials are successfully fabricated by using pulse current sintering technique. The relationship between hardness HV and fracture toughness KIC of the composites is compared with those of WC–Co materials reported. The comparison suggests successful development of WC–FeAl composites with the characteristics almost equal to WC–Co materials currently used for the hard metal tools. Microstructure of the sintered WC–FeAl is uniform without any grain growth. In the KIC–HV plot, WC–FeAl composites locate at the same position as that of WC–Co materials. The total mechanical property of WC–FeAl is comparable to WC–Co. The developed WC–FeAl is a very promising candidate to replace WC–Co materials. Fully controlled microstructure is crucial.

An Integrated Lighting Unit With Regulated Pulse Current Driving Technique

This paper proposes an integrated lighting unit using the regulated-pulse-current-driving technique for low-power application. On-chip/package integration of a white light-emitting diode (WLED) with a light-emitting diode (LED) driver, also named a lighting unit in this paper, may be ideal for smaller and lighter portable devices. The integrated lighting unit is connected to a pulse current driver fabricated with the complementary metal-oxide-semiconductor (CMOS) technology and a WLED on-chip integration. Such a combination would help reduce the packaging costs and the size of the device as well as increase the luminous density. Two control signals are used in the proposed driver to modulate the pulse current. One signal modulates the amplitude of the pulse current from 100 to 500 mA, and the other modulates the pulse current frequency between the ranges of 350 and 750 kHz. The dimming method and experiments on the prototype of the lighting unit have been built and measured. The active area of the designed chip is 0.64 mm × 0.56 mm in a 0.5-μm CMOS process. The resulting integrated lighting unit works well; therefore, this compact device is suitable for portable applications.

A Regulated Pulse Current Driving Technique in Green Laser Synthesis With Electrical to Optical Conversion Efficiency Improvement for Mobile Projectors

In this paper, we propose a regulated pulse current laser driver with the frequency double approach to synthesize green laser. Experiment results show that green laser synthesis conducted with the regulated pulse current driving (RPCD) technique has an electrical to optical conversion efficiency improvement of up to 78%, as compared to the DC driving technique with mean driving current of 250 mA at room temperature. This driver was fabricated with a 0.5 μm CMOS process and has a modulation frequency range of 300 kHz-700 kHz, a wide range of peak pulse current between 120 mA-900 mA with the average current range between 0 mA-280 mA. This paper not only demonstrated the synthesize procedure of green laser but also proposed driver with the RPCD technique enhances the electrical to optical conversion efficiency of green laser and its implementation in integrated circuit, making it a good match with green laser microchip to create a low cost, compact-sized device ideal for mobile projector applications.

Enhanced Mechanical Properties of AA5083 GTA Weldments with Current Pulsing and Addition of Scandium

AA5083 alloy is welded with gas tungsten arc welding using optimized welding parameters. Al-Si-Sc master alloy filler with varying contents of scandium is used for welding. Welding was carried out with and without AC-pulsed current techniques. A narrow heat affected zone with more refined grain structure is observed in the case of the pulsed current technique. Furthermore, it is observed that the columnar solidification structure in the fusion zone was suppressed and fine equiaxed grains were formed in the weld zone with increasing scandium content, which is attributed to the grain refinement effect of scandium with the generation of increased nucleating sites during weld solidification. This effect is reflected in mechanical properties also. An increased hardness of about 10 % results with pulsed current technique compared to about 20 % with an addition of 0.75 % scandium. However, in the case of tensile properties pulsing resulted in about 8 % increase in tensile strength and addition of 0.75 % scandium resulted in about 40 % increase in tensile strength. Both the pulsed current technique and the addition of scandium were observed to be better in increasing not only strength but also elongation due to the refined grain structure in the weld fusion zone.

Tailoring the physical properties of electrodeposited CoNiReP alloys with large Re content by direct, pulse, and reverse pulse current techniques

The composition, surface morphology and structure of CoNiReP alloy films with large Re content (up to 27at%), obtained in a citrate-glycine based electrolyte have been studied as a function of the electrodeposition technique. Direct current (DC), pulse plating (PP) and reverse pulse plating (RPP) were considered with cathodic current densities from −50mAcm−2 to −250mAcm−2. The mechanical and magnetic properties have been analyzed and the data obtained has been correlated with composition and crystallographic structure. For values of j (DC), jon (PP) and jc (RPP) below −100mAcm−2, Co-rich, P-containing deposits are obtained. Beyond these current densities, both the quantities of Ni and Re increase simultaneously at the expense of Co and P, the latter virtually falling to zero. The highest Re percentage (25–27at%) was achieved in both PP and RPP conditions at a cathodic pulse of −250mAcm−2. All the films were either entirely nanocrystalline in nature or partially amorphous. Hardness values as high as 9.2GPa have been found in PP plated Co64Ni18Re18 deposits. Besides the large hardness, the incorporation of Re in the films leads to high elastic recovery values. The magnetic character of the deposits ranges from soft to semi-hard ferromagnetic.

Energy consumption of electrooxidation systems with boron-doped diamond electrodes in the pulse current mode

A pulse current technique was conducted in a boron-doped diamond (BDD) anode system for electrochemical wastewater treatment. Due to the strong generation and weak absorption of hydroxyl radicals on the diamond surface, the BDD electrode possesses a powerful capability of electrochemical oxidation of organic compounds, especially in the pulse current mode. The influences of pulse current parameters such as current density, pulse duty cycle, and frequency were investigated in terms of chemical oxygen demand (COD) removal, average current efficiency, and specific energy consumption. The results demonstrated that the relatively high COD removal and low specific energy consumption were obtained simultaneously only if the current density or pulse duty cycle was adjusted to a reasonable value. Increasing the frequency slightly enhanced the COD removal and average current efficiency. A pulse-BDD anode system showed a stronger energy saving ability than a constant-BDD anode system when the electrochemical oxidation of phenol of the two systems was compared. The results prove that the pulse current technique is more cost-effective and more suitable for a BDD anode system for real wastewater treatment. A kinetic analysis was presented to explain the above results.

Effect of Pulsed Current on Temperature Distribution and Characteristics of GTA Welded Magnesium Alloy

This paper compares temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded AZ31B magnesium alloy joints. The effect of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution are reported. The use of pulsed current technique has been found to improve the tensile properties of the welds compared to those of continuous current welds due to grain refinement occurring in the fusion zone.

ZnO films and nanorod/shell arrays electrodeposited on PET-ITO electrodes

In this work, ZnO films, nanorod and nanorod/shell arrays were synthesized on the surface of PET-ITO electrodes by electrochemical methods. ZnO films with high optical transmittance were prepared from a zinc nitrate solution using a pulsed current technique with a reduced pulse time (3s). The X-ray diffraction pattern of ZnO film deposited on PET-ITO electrode showed that it has a polycrystalline structure with preferred orientations in the directions [002] and [103]. ZnO nanorods were synthesized on electrochemical seeded substrate in an aqueous solution containing zinc nitrate and hexamethylenetetramine. In order to increase the stability of PET-ITO electrode to electrochemical and chemical stresses during ZnO nanorods deposition the surface of the electrode was treated with a 17wt% NH4F aqueous solution. Electrochemical stability of PET-ITO electrode was evaluated in a solution containing nitrate ions and hexamethylenetetramine. ZnO nanorod/shell arrays were fabricated using eosin Y as nanostructuring agent. Photoluminescence spectra of ZnO nanorod and ZnO nanorod/shell arrays prepared on the surface of PET-ITO electrode were discussed comparatively. By employing the 1.5μm-length ZnO nanorod/shell array covered with a Cu2O film a photovoltaic device was fabricated on the PET-ITO substrate.

An LED Driver With Pulse Current Driving Technique

A novel driving technique, called pulse current driving technique for LED driver, is proposed. A complete introduction and analysis of the proposed driving technique and the conventional driving technique will be presented in this paper. The LED driver supply maximum peak current is 220 mA and operating frequency is between 500 kHz and1 MHz. Simulation and experimental results are presented to verify the analytical results. The LED driver is fabricated with CMOS 0.35-μm technology and chip area with pads is 0.89 mm 2. The design of the proposed circuit structure is simple, without additional output capacitance compensation for stability and with small power consumption, and is implemented in integrated circuit. As a result of the above benefits, the proposed approach is believed to be suitable in portable application.

Electrodeposition of Cobalt Nanoparticles on Thin Niobium Films

Hydrogen evolution reaction (HER) takes place immediately after the reduction of Co nanoparticles (NPs) and varies the structure of the Co NPs. The Co NPs deposited by low cathodic current exhibit their hcp- 〈1011〉 parallels the surface normal. To increase the cathodic current can increase the ratio of the polar magnetization to the longitudinal one. This is referred to an increasing population density of the Co NPs which have hcp(0002) structure during the very early depositing stage. However, for further deposition, the intensive HER in such a high cathodic current could vary the shape of the Co nanoparticles. In order to make the Co NPs to persist their hcp(0002) structure, a double pulse current technique was chosen. The population density of the Co NPs is significantly controlled by the first high current pulse and the ratio is obviously increased. This implies that the HER effect plays an important role in the initial nucleation structure of the Co NPs. This provides us a method to control the structure and magnetism of the Co NPs by choosing a suitable combination of current pulses.

Experimental investigation of the lithium-ion battery impedance characteristic at various conditions and aging states and its influence on the application

In recent years, lithium-ion batteries have often been proposed as part of various hybrid energy systems. Examples of such applications are hybrid vehicles, photovoltaic-battery or wind-battery systems and power distribution grids. One of the key functions of a battery is to be source of an additional power when the main power source in the system cannot cover the power demands. The power capability of the battery is described by its impedance characteristic. It depends significantly on the battery state-of-charge (SoC), the temperature, the current and the previous history. In this paper, these dependencies and their variations over the battery lifetime are investigated on a 40 Ah lithium-ion cell produced by Kokam (Type SLPB100216216H) with nickel manganese cobalt oxide (NMC) cathode material as an example. For this purpose, a full characterisation of the battery impedance is performed in the new and aged states using electrochemical impedance spectroscopy (EIS) and the current-pulse technique. The results obtained for the new and aged states are compared. The results show, for example, that the SoC range, in which the battery operates with high efficiency, decreases due to significant aging. For the first time, the nonlinearity (current dependency) of the battery resistance is investigated extensively. It varies slightly with the SoC and considerably with the temperature, and it also changes during the battery lifetime. Furthermore, the dependency of the lithium-ion battery impedance on the short-time previous history is shown for the first time for a new and aged cell. The influence of the measured dependencies of the battery impedance on potential applications is discussed.

Fabrication Lead Dioxide Coating by Pulse Current Method

Prepared lead dioxide（PbO2） coating on a Ti substrate by pulse current technique. The effect of the pulse current density, pulse time and relaxation time on the morphology and electrochemistry properties of the coating was studied by means of scanning electron microscopy and electrochemistry station. Compared with lead dioxide fabricate by common electroplate technique, lead dioxide coating prepared by pulse current technique is more dense, without hole, better corrosion resisting property and more stable electrochemistry properties.