Pulse Current Parameters Research Articles

Influence of pulse currents on the nanostructure and color absorption ability of colored anodized aluminum

Few investigations have been carried out on the influence of the variation of pulse current parameters on the anodized aluminum. The present paper deals with some experimental results regarding the influence of pulse current parameters on the nanostructure and color absorption ability of colored anodized aluminum. Under these conditions, the nanostructure and the color were found to be dependent on the duty cycles and frequencies. The Field Emission Scanning Electron Microscopy (FE-SEM) analysis showed that variation of the pulse current parameters changed and improved the distribution and uniformity of the pores within the anodic layer and consequently the quality of the final color.

The influence of the current pulse parameters on the development of a physical contact at metal pressure welding

The influence of the current pulse parameters on the development of the physical contact area between some connectable surfaces during welding of solid dissimilar metals has been studied and the results are presented in this work. Using a composite of steel 20 and copper M1 compressed by a pressure of about 50 MPa as an example, there is determined the most preferable range of the pulse current’s parameters: the current density amplitude with regard to the skin effect within the range from 1 × 109 to 2 × 109 A/m2 and the specific total energy of the treatment within the range from 0.6 × 109 to 1 × 109 J/m3, in which one can efficiently control the processes of the plastic deformation of the surfaces and, thus, control the formation of a butt welded joint.

Integration of Electroplated CoFe in Trench Type Flux Guides for Magnetic MEMS Applications

For a magnetic MEMS application, the integration of soft magnetic flux guides with high saturation flux density is often needed. A complex form including a trench in substrate was designed to achieve its flux guide function. Electroplating CoFe with followed Chemical-mechanical Polishing (CMP) process was chosen as fabrication technology. Pulse current was selected as power supply for electrodeposition process. Experimental results show, that fine tuned pulse current parameters are necessary for electroplating high magnetic performance, low residual stress CoFe films into a trench form without any formation of cracks and voids. For the further system integration a planarization step is required. Since the CoFe layers show a strong response to the chemical attack causing etching, the mere mechanical polishing process is adequate for the planarization of CoFe. Furthermore, the application of alumina abrasives shows very good results regarding surface quality.

Biomimetic method for metallic nanostructured mesoscopic models fabrication

ABSTRACTVarious metallic structures of complex shape, resembling natural objects such as plants, mushrooms, and seashells, were produced when growing nanowires by means of pulsed current electroplating in porous membranes. These structures occur as the result of nanowires self-assembling (biomimetics) if the electroplating is continued after the nanowires reach the membrane surface. By varying the membrane geometry and the pulsed current parameters, and alternating electroplating from two baths with different electrolytes, various models were fabricated, including a hollow container with wall thickness of 10-30 nm. The possibility of shape regulation for models was demonstrated: in certain conditions, mushroom- and shell-like convex-concave models of the same kind were obtained. The hierarchical structure of models at the nano-, micro- and mesoscopic levels is shown through fragmentation and chemical etching. This biomimetic method suggests an analogy between the shape-forming processes of natural plants and their metallic models. Nanostructured mesoscopic objects of metals (Ag, Pd, Rh, Ni, Bi), alloys (PdNi, PdCo, PbIn) as well as their combinations (PdNi/ Pb, PdNi/ PbIn) were obtained. The technological simplicity of the present method makes it suitable for fabricating nanostructured materials that may be efficient in catalysis, superhydrophobic applications, medical filters, and nanoplasmonics.

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.

Characteristics of current pulses in rocket-triggered lightning

The waveform parameters of current pulses in negative rocket-triggered lightning are analyzed statistically using recorded channel-base current during Shandong Artificially Triggered Lightning Experiment (SHATLE) from 2005 to 2011. The current pulses are divided into 3 categories, including return strokes, ICC pulses in initial continuous current (ICC) stage and M-components superimposed on the continuing current following the return stroke. The geometric mean values (GM) of peak current, risetime from 10% to 90% peak, half peak width and charge transfer for return strokes are 12.1kA, 1.0μs, 14.8μs, and 0.86C, respectively. The corresponding parameters for ICC pulses are 0.09kA, 437μs, 712μs, and 0.10C, respectively, while they are 0.28kA, 251μs, 242μs and 0.10C for M-components, respectively. There is significant fraction of larger M-components (about 10% of 63 samples) demonstrating peak current of several kilo-amperes, comparable to weak return strokes. The ICC pulses show somewhat lower current peak and slower risetime than the M-components with a difference of roughly 2–3 times, resulting from the lower charge source of ICC pulses. In general, the ICC pulses and M-components show smaller peak current and charge transfer while longer risetime and half peak width than return strokes, differing with 1–2 orders of magnitude. The charge neutralized by an individual triggered lightning flash ranged from 6.3C to 68.1C, while the initial stage (IS), lasted about 245ms (GM) and lowered a GM charge of 21.2C to the ground. The average IS current in an individual lightning discharge varies from 45.8A to 140.6A with a GM value of 86.7A.

CdSe semiconducting layers produced by pulse electrolysis

Thin films of CdSe semiconductors electro deposited from acid aqueous electrolytes onto Ti substrates have been developed using periodically modified currents, such as pulse current. The products obtained were fully characterized and their photoelectric behavior was studied using a photo electro chemical cell. All deposits obtained by pulse electrolysis exhibit some differences in their structure, surface morphology and photoelectric properties, depending on the imposed pulse current parameters such as pulse frequency and duty cycle. It was also found that increased photoelectrochemical efficiencies are observed to so higher pulse frequencies as more negative deposition potentials are applied and vice-versa.

Pulse electrodeposition of Zn–Co alloy coatings obtained from an alkaline bath

Zn–Co alloy coatings were electrodeposited on steel substrate using a cyanide-free alkaline bath containing glycine as a complexing agent. The effect of pulse current parameters, such as current-on time (Ton), current-off time (Toff) and peak current density (Ip) on the surface morphology, chemical composition and phase distribution of coatings were investigated using SEM, EDS and XRD. Also, the corrosion behavior of the coatings was studied by using potentiodynamic polarization test in 3.5wt.% NaCl solution. The results showed that Ip and Ton had a significant effect whereas Toff had a slight effect on chemical composition and surface morphology of the deposits. It was also shown that increasing peak current density, up to 220mAcm−2, decreases the grain size and further increase in current density increases the grain size of the deposit. The corrosion resistance of the deposits was also highly influenced by the composition and morphology of the coatings. On the whole, Zn–Co deposit containing 2.35wt.% Co showed the highest corrosion resistance among the coatings due to its single phase structure and its fine morphology.

Study on Factors Effecting Weld Pool Geometry of Pulsed Current Micro Plasma Arc Welded AISI 304L Austenitic Stainless Steel Sheets Using Statistical Approach

Pulsed current Micro Plasma Arc Welding is used to joint thin sheets of AISI 304L sheets, which are used in manufacturing of metallic bellows and diaphragms. In this article the effects of pulsing current parameters on weld pool geometry namely front width, back width, front height and back height of pulsed current micro plasma arc welded AISI 304L stainless steel sheets was analyzed. Four factors, five levels, central composite design was used to develop mathematical models, incorporating pulsed current parameters and weld pool geometry. The mathematical models have been developed by Response Surface Method. The adequacy of the models was checked by ANOVA technique. Variation of output responses with input process variables are discussed. By using the developed mathematical models, weld pool geometry parameters can be predicted.

Optimization of Experimental Conditions of the Pulsed Current GTAW Parameters for Mechanical Properties of SDSS UNS S32760 Welds Based on the Taguchi Design Method

Taguchi design method with L9 orthogonal array was implemented to optimize the pulsed current gas tungsten arc welding parameters for the hardness and the toughness of super duplex stainless steel (SDSS, UNS S32760) welds. In this regard, the hardness and the toughness were considered as performance characteristics. Pulse current, background current, % on time, and pulse frequency were chosen as main parameters. Each parameter was varied at three different levels. As a result of pooled analysis of variance, the pulse current is found to be the most significant factor for both the hardness and the toughness of SDSS welds by percentage contribution of 71.81 for hardness and 78.18 for toughness. The % on time (21.99%) and the background current (17.81%) had also the next most significant effect on the hardness and the toughness, respectively. The optimum conditions within the selected parameter values for hardness were found as the first level of pulse current (100 A), third level of background current (70 A), first level of % on time (40%), and first level of pulse frequency (1 Hz), while they were found as the second level of pulse current (120 A), second level of background current (60 A), second level of % on time (60%), and third level of pulse frequency (5 Hz) for toughness. The Taguchi method was found to be a promising tool to obtain the optimum conditions for such studies. Finally, in order to verify experimental results, confirmation tests were carried out at optimum working conditions. Under these conditions, there were good agreements between the predicted and the experimental results for the both hardness and toughness.

The Effect of Hybrid Ultrasonic Pulse Current Parameters on VPTIG Arc Pressure and Weld Formation

Based on a novel arc welding device which can provide hybrid ultrasonic pulse current, the effect of hybrid pulsed current parameters on the arc pressure and weld formation during the aluminum alloy welding process was investigated. The experiment results show that, compared with normal VPTIG process, hybrid ultrasonic pulse VPTIG process gets greater arc pressure. Under the condition of keeping the RMS of positive current unchanged, lowering duty ratio has an evident effect on increasing arc pressure. At proper frequency range, increasing the pulse frequency and decreasing the pulse duty ratio can increase the depth and width of the weld, improve weld penetration rate correspondingly, and be beneficial to improve weld quality.

Influences of pulsed current parameters on mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloys

This paper reveals the influences of pulsed current parameters, namely peak current, base current, pulse frequency and pulse-on time, on the mechanical and metallurgical properties of gas tungsten arc welded AZ31B magnesium alloys. Twenty joints were fabricated using different levels of peak current, base current, pulse frequency and pulse-on time. The tensile properties of the welded joints were evaluated and correlated with the weld zone’s microstructure and hardness. Optical microscopy, scanning electron microscopy and X-ray diffraction were used to evaluate the metallurgical characteristics of the welded joints. The joints fabricated using a peak current of 210 A, base current of 80 A, pulse frequency of 6 Hz and pulse on time of 50 % yielded tensile properties superior to the other joints. The formation of fine grains in the weld region, higher fusion zone hardness and uniformly distributed precipitates are the main reasons for the superior tensile properties of these joints.

Evaluation Study on Angular Distortion and Residual Stress of Stainless Steel Pulsed TIG Weldment

The aim of this study was to investigate the effect of pulsed current welding parameters on angular distortion and residual stress of TIG weldment. Autogenous TIG welding was applied on type 316L stainless steel sheet to produce bead-on-plate welds. Angular distortion was determined using the mean vertical displacement method. Residual stress was determined using the hole-drilling strain- gage method. The results showed that the pulsed current TIG welding has a number of advantages, including lower heat input and consequently a reduction in distortion and residual stress of weldment.

Pulse current electrodeposition of Al from an AlCl 3-EMIC ionic liquid

Electrodeposition of aluminum from an AlCl 3-EMIC ionic liquid with or without the addition of saturated LaCl 3 was carried out by both direct- and pulse-current plating methods. The effects of various parameters, including current density, pulse frequency, current on/off duration ( t on and t off), and temperature, on deposit morphology and crystal size were investigated. Deposits prepared by pulse-current plating gave a brighter and flatter surface than those prepared by direct-current plating at appropriate pulse current parameters. Temperature and pulse–current frequency ( t off) were shown to significantly affect deposit morphology. Coalescence of grains during t off periods in the pulse current plating was observed, especially at temperatures above 60 °C. Increasing the temperature from 25 to 90 °C caused an increase in deposit grain size and resulted in a change of grain shapes from a small sphere-like form to a feather-like form. As a result, the adhesion of the deposited aluminum to the substrate was lowered. Smaller grain sizes and well-adhered deposits were achieved at lower temperatures. For example, deposition at 25 °C resulted in the smallest crystal size of about 0.3 μm under the conditions of t on = 80 ms, t off = 20 ms, and i = 8 mA/cm 2. Furthermore, the addition of LaCl 3 to the melt at 60 °C effectively reduced the porosity and improved compactness of deposits.

Effects of Direct Current and Pulse Electrodeposition Parameters on the Properties of Nano Cobalt Coatings

The aim of this study was to investigate the effects of direct current (DC) and pulse current (PC) parameters on the properties of cobalt (Co) coatings electrodeposited from a chloride acidic bath. The effects of peak current density, frequency and duty cycle on the surface morphology, crystal size, thickness, current efficiency, and preferred orientation of the deposits were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental thickness of the deposit was lower for pulse plating compared to that of DC plating. The current efficiency was comparatively higher for pulse plating. Less porosity and fine grains were formed by pulse plating. From XRD analysis, the calculated grain sizes of nano and micro Co coatings were around 65nm and 430nm, respectively. The results showed that, with an increase in duty cycle, grain sizes would increase, too. As pulse frequency was increased to 50Hz, grain sizes would also decrease. However, at higher frequencies, grain sizes would increase again.

A study of the electromagnetic and hydrodynamic processes in a liquid-metal conductor exposed to current pulses

In this work, we describe the results of a mathematical simulation of the electromagnetic and hydrodynamic processes that occur in a liquid-metal aluminum conductor while the passing of a kiloampere single-pulse current of microsecond duration through it. It is found that the compression of the liquid conductor by the magnetic pressure occurs upon exceeding a certain threshold value of the pulse current, which is governed by the metallostatic pressure. The fields and absolute values of the flow velocities in the conductor depending on the current pulse parameters are determined.

Experimental Study of Bipolar Pulse Electroforming on Micro Optical Aspheric Mold Manufacturing

Compared with unipolar and periodic reverse pulse current electroforming, bipolar pulse current in electroforming is known to result in better precision and surface finish. In this paper, bipolar pulse current electroforming is introduced. The influencing parameters, such as electrolyte parameter, additives, current density, PH value, temperature and pulse current parameters have been studied on experiments. Experiments on nickel and nickel alloys electroforming on micro optical aspheric moulds have been done. The results indicated that bipolar pulse current could improve the quality and precision, reduce internal stress in micro electroforming.

Pulse co-electrodeposition and characterization of NiW–WC composite coatings

The present study investigates the influence of pulse current parameters on the structure and hardness of the co-deposited nickel tungsten alloys incorporated by tungsten carbide particles (NiW–WC) for environmentally friendly alternatives to chromium deposits. While a minimum average current density of about 0.04 A/cm 2 is required for sufficient co-deposition kinetics, a decrease of duty cycle from 50% to 10% and a reduction of pulse frequency from 100 Hz to 10 Hz generally result in the increase of the carbide content in the deposits. Furthermore, these pulse parameters also affect the content of tungsten alloyed in the nickel matrix. NiW–WC of high hardness exceeding that of hard chromium coating by about 40% is achieved in the deposits with uniform structure, and with 31 at.% W and 13 wt.% WC particles. The mechanisms controlling the co-electrodeposition process and the corresponding hardness are discussed.

Assessment of low-density lipoprotein oxidation, paraoxonase activity, and arterial distensibility in epileptic children who were treated with anti-epileptic drugs

Studies show that anti-epileptic drugs increase oxidative stress. Thus, low-density lipoprotein oxidation increases and atherogenesis is induced. Paraoxonase-associated high-density lipoprotein protects low-density lipoprotein and high-density lipoprotein oxidation. The effects of anti-epileptic drugs on paraoxonase activity has not been investigated yet. The aim of this study is to investigate the effect of anti-epileptic drugs on paraoxonase activity, lipid profiles, folat, vitamin B12, homocysteine, thyroid hormones, apolipoprotein A-1, total anti-oxidant capacity, malondialdehyd, nitric oxide, and oxidised low-density lipoprotein. The association with carotid-femoral pulse wave velocity and current biochemical parameters had been searched for assessing the effects of anti-epileptic drugs on the vascular system. We recruited 59 epileptic patients treated with anti-epileptic drugs and 23 controls (group IV) at least 6 months ago. The epileptic group was divided into three groups by receiving anti-epileptic drugs as follows: group I: carbamazepine, group II: valproic acid, and group III: carbamazepine and valproic acid. Arterial distensibility was assessed with the Complior device. There was no difference between the current biochemical parameters in epileptic children. Serum-free T4 was decreased, when compared with group IV. Thyroid-stimulating hormone was increased in group II, compared with group IV. The carotid-femoral pulse wave velocity was increased in group III, compared with group IV. The carotid-femoral pulse wave velocity was correlated with thyroid-stimulating hormone and valproic acid levels. Anti-epileptic drugs may induce atherogenesis by affecting the thyroid hormones. According to the current data, the effects of thyroid hormones on vascular system may be independent of other biochemical markers. Epileptic patients using anti-epileptic drugs must be followed closely for arterial stiffness, and also for the development and progression of atherosclerosis.

Vagus nerve stimulation for epilepsy activates the vocal folds maximally at therapeutic levels

Vagus nerve stimulation (VNS) for medically refractory epilepsy can give hoarseness due to stimulation of the recurrent laryngeal nerve. For a group of VNS-therapy users this side-effect interferes severely with their daily activities. Our goal was to investigate the severity of intra-operative VNS-related vocal fold contraction at different pulse widths and current output parameters. We investigated electromyographic and morphometric alterations on the vocal folds during VNS. Vocal fold EMG experiments were conducted intra-operatively during the implantation of a VNS system. During surgery the VNS pulse generator was programmed to stimulate at different pulse durations. At each pulse width the EMG-threshold current was determined by electrical stimulation of the vagus nerve with increasing stimulation currents. Laryngostroboscopic examination was performed after surgery to analyze the effects of spontaneous stimulation on the larynx. The vocal fold EMG and morphodynamic changes in the larynx have been analyzed in eight patients. In all patients left vocal fold EMG-threshold was between 0.25 and 0.50 mA. Pulse duration had little influence on the EMG-threshold level. Vocal fold EMG saturation levels were reached between 0.75 and 1.00 mA. Video stroboscopic monitoring showed that stimulation induced an adductory spasm of either the ipsilateral vocal fold or the vestibular fold, and was present remarkably irrespective of the presence of hoarseness. VNS causes pronounced effects on the vocal folds even at low stimulation amplitudes. At therapeutic levels even at the lowest stimulation pulse durations, the vocal fold contract, however, this does not necessarily give hoarseness.