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Aluminum coating is a potential candidate for cadmium coating replacement due to its excellent corrosion resistance and nontoxicity. Among the fabrication methods of Al coating, plating Al via ionic liquids has drawn major attention of researchers because of the superiority of controllability, stability and low energy consumption. However, the evolution rules of plating aluminum on high-strength steel via pulse current modes at room temperature requires deeper investigation. In this work, pulse current density and pulse duty factor are regulated to reveal the plating patterns of Al on 300M high-strength steel in AlCl 3 -EMIC (2:1 in mole) ionic liquid. It is found that higher current density can significantly facilitate the nucleation of Al grains and the compactness of morphology, while an enlarged pulse duty factor tends to result in more regular Al crystals. When the current density and the pulse duty factor are fixed at 20 mA cm−2 and 80 %, the densest and most uniform aluminum coating is obtained. The component of Al coating is verified to be pure Al crystals with good adhesion and the plating process achieves a high current efficiency of 97.27 %. Under the protection of Al coating, the impedance and galvanic corrosion current density of 300M steel substrate are optimized by two orders of magnitude, and the corrosion current density is markedly decreased from 5.58 μA cm−2 to 0.77 μA cm−2. [ABSTRACT FROM AUTHOR]

A one-pot strategy is employed for facile synthesis of mesoporous Li x MnO 2 (x = 0.19–0.41) by means of pulse electrodeposition technique. Li x MnO 2 materials with different chemical and physico-chemical properties are synthetized by modulating the pulse parameters. As results demonstrating, the functional properties of Li x MnO 2 are deeply influenced by varying both independent parameters namely, t on (time of current applying) and t off (time of current switching off) as well as dependent parameters: duty cycle (θ) and pulse frequency (ƒ). The mesoporous Li 0 . 41 MnO 2 with a hierarchical morphology of nano-walls and a considerably high BET surface area of 137.49 m 2  g −1 is achieved by applying the optimized pulse parameters (t on  = 5 ms, t off  = 45 ms, duty cycle = 10% and pulse frequency = 20 Hz). The Li 0 . 41 MnO 2 shows superior performance as cathode material of Li-ion batteries, delivering the first discharge capacity of 284.45 mAh g −1 , retaining 94.22% of first discharge capacity after 250 charge-discharge cycles and is still able to deliver 204 mAh g −1 after 110 successive charge-discharge cycles at different C-rates. This work proves that applying a lower duty cycles of pulse current, with optimized value of 10%, leads to the unique featured properties of Li x MnO 2 which giving rise to superior electrochemical performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pulse current improved the acidification process by supplying more reactive H+ ions. [•] Higher removal efficiencies of heavy metals were obtained in pulsed EDR. [•] Soil buffering capacity influenced the efficacy of pulse current. [•] Energy distribution analysis revealed most energy consumed at soil suspension. [•] The transition time of membranes was characterized by chronopotentiometric study. [ABSTRACT FROM AUTHOR]

Abstract: The aims of this paper were to investigate the possibility for energy saving when using a pulsed electric field during electrodialytic soil remediation (EDR) and the effect of the pulsed current on removal of heavy metals. Eight experiments with constant and pulse current in the different industrially polluted soils were performed. At a current density of 0.1mA/cm2 in soil 1 and 0.2mA/cm2 in soil 2, there was no difference on energy consumption and removal of heavy metals between pulse current and constant current experiments, but at higher current experiments (i.e., 0.2mA/cm2 in soil 1 and 0.8mA/cm2 in soil 2) the energy was saved 67% and 60% and the removal of heavy metals was increased 17–76% and 31–51% by pulse current in soil 1 and soil 2, respectively. When comparing the voltage drop at different parts of EDR cells, it was found that the voltage drop of the area across cation exchange membrane was the major contributor of energy consumption, and the pulse current could decrease the voltage drop of this part effectively. The overall removal of heavy metals in soil 1 (6–54%) was much higher than soil 2 (1–17%) due to the different acidification process and chemical speciation of heavy metals reflected by sequential extraction analysis. Among all experiments, the highest removal efficiency occurred in pulse current experiment of soil 1, where 54% of Cu and 30% of As were removed. [Copyright &y& Elsevier]

Abstract: Electrodeposition of aluminum from an AlCl3-EMIC ionic liquid with or without the addition of saturated LaCl3 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 0.3μm under the conditions of t on =80ms, t off =20ms, and i =8mA/cm2. Furthermore, the addition of LaCl3 to the melt at 60°C effectively reduced the porosity and improved compactness of deposits. [Copyright &y& Elsevier]

Abstract: In this study, a pulse current supply was initially used in a BDD anode system (pulse-BDD anode system) for electrochemical oxidation of phenol. The influences of operative parameters (current density, retention time, pulse duty cycle, power frequency) on the system performances were exmamined by response surface methodology (RSM). As for COD degradation efficiency (D COD) and specific energy consumption (E s), the influence of retention time was more important than current density and pulse duty cycle, while power frequency hardly presented significant influence. By the comparison with constant current mode, an obvious specific energy consumption reduction was achieved in the pulse-BDD anode system, though the D COD was slightly lower. The significant E s decrease might be attributed to the reduction of side reactions and concentration polarization in pulse current mode. The pulse-BDD anode system demonstrated an efficient technology to simultaneously obtain high pollutant degradation efficiency and low energy consumption. [Copyright &y& Elsevier]

Abstract: TiO2 layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but increased with duty cycle at high applied voltages. The topographical evaluations showed that the surface of the layers is rough with an average roughness of about 1.8–9.9nm. It was also found that the pore size decreased with the current frequency and increased with duty cycle at a fixed applied voltage. Photocatalytic performance of the layers was also examined by measuring the decomposition rate of methylene blue solution under ultraviolet irradiation of the surface. It was also found that about 94% of methylene blue solution was decomposed on the synthesized catalysts after 160min UV irradiation of the surface. [Copyright &y& Elsevier]

Abstract: A mathematical model was developed to describe the effect of the current shape waveform on the grain size, formation, growth rate, and deposits hardness for progressive nucleation (simultaneous nucleation and growth) when four pulse current waveforms are applied: rectangular, ramp up, ramp down, and triangular waveforms. In the model, it is considered that species diffusion across the limit layer is the rate determinant step. The Hall-Petch expression was used to relate the grain size in the metal to its hardness. The model results are compared with the experimental data for nickel electrodeposit hardness, which were presented by Wong et al. (K.P. Wong, K.C. Chan, T.M. Yue, J. Appl. Electrochem. 31 (2001) 25). The model predictions are consistent with the experimental results for the four current waveforms, with an average hardness deviation of about 10% for currents between 1 and 6kA/m2. [Copyright &y& Elsevier]