关键词： PM6 semiempirical method   metal-electrolyte systems   modeling   electronic structure   adsorption   hydration   micropotential  

摘要： We develop a computer model of the electrochemical behavior of a metal-electrolyte contact boundary by using the quantum-chemical semiempirical method (PM6) and the molecular-dynamics method. We consider the evolution of the metal-medium systems and thoroughly study the thermodynamic and kinetic features of establishing the adsorption-desorption equilibrium for the Cu-electrolyte, Zn-electrolyte, Fe-electrolyte, and alpha-brass-electrolyte cluster systems. We compute the electrode micropotentials of copper, zinc, and alpha-brass, which satisfactorily agree with the experimental data.

关键词： Li1+xV3O8   Electrochemical properties   Tartaric acid   Citric acid  

摘要： Lithium-ion battery cathode material Li1+xV3O8 is synthesized by a citric acid/tartaric acid assisted sol -gel method and sintered at 350 degrees C, 450 degrees C and 550 degrees C for 3 h for the formation of Li1+xV3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD, SEM, EIS and charge-discharge tests. Li(1+)xV(3)O(8) material synthesized by tartaric acid assisted route and sintered at 450 degrees C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g(-1) and still reserves a discharge capacity of 260 mAh g(-1) after 50 cycles. Moreover, in the case of tartaric assisted products, no capacity decadence is observed in 50 cycles. XRD together with TG/DTA measurements reveal that compared with citric acid assisted products, the adoption of tartaric acid as chelating agent effectively lowers the crystallization temperature of amorphous Li1+xV3O8. Therefore, precursors obtained by tartaric acid route calcinated at 450 degrees C for 3 h exhibit lower crystallinity and smaller grain size, which contributes to the better electrochemical performance of the cathode electrodes. From EIS measurements, the bulk resistance is reduced, which favors the intercalation and de-intercalation of lithium ions while cycling. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Advanced mddation process   1,4-dioxane   Electrochemical Fenton-type process   Ferrous ion   Hypochlorous acid   Iron sludge  

摘要： This paper reports on the reusability and the optimal reuse of iron-rich sludge for an electrochemical Fenton-type process using sequencing batch mode and separation batch mode reuse models. In the sequencing batch mode, processes of electrochemical treatment, neutralization, sedimentation, and re-dissolution of iron sludge were all performed in the same reactor, whereas the neutralization and sedimentation of iron sludge in the separation batch mode was carried out in an iron recovery tank separated from the electrochemical reactor. The effects of iron speciation at different pH levels were discussed. It was found that ferric ions at a pH <= 2.5 were suitable for this electrochemical Fenton-type process where ferrous ions acted as hydroxyl radical scavengers, generating brownish deposits on the cathode at pH 3. When the sequencing batch mode was applied, the current efficiency in the Fenton-type process after the iron recovery declined due to the formation of insoluble deposits on the electrodes, which decreased at lower pH. The deposits were mainly formed during the neutralization and sedimentation steps after the electrochemical process. Fortunately, iron from the sludge could be reused for the electrochemical process when the separation batch mode was used, with 100% iron recovery and no decline in current efficiency. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Pulsed electrochemical micromachining   Electrical double layer   Inter-electrode gap   Numerical simulation   Finite Element Method  

摘要： Pulsed electrochemical micromachining is a metal dissolution process where the capacitive behaviour of the double layer enhances the confinement of the machining profile, when very short voltage pulses are applied. During the pulses, the dissolution is confined to electrode regions where the tool-workpiece gap is the smallest. The model used combines the potential distribution in the electrolyte with the load-unload behaviour of the double layer. The model is solved using the Finite Element Method. The pulse and double layer charging are the main focus and therefore no shape change is included in the model at this point. The influence of the double layer, pulse signal parameters and inter-electrode gap size on the dissolution current density (material removal depth), as a function of time, is investigated. An estimation of the double layer loading time is presented, as well as a quantification method for the metal removal confinement, by comparing the calculated error against an ideal removal profile. The influence of pulse characteristics on the dissolution process has also been studied. It was found that a strongly non-linear polarization in combination with nano-second pulses and a small gap size increases the confinement. All the simulation results were obtained on an axisymmetric case by considering several geometrical set-ups. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Impurity segregation   Electrorefining   Ultrapure materials   Solar-grade silicon  

摘要： A theory for impurity segregation in electrochemical processes is formulated based on the Nernst equation, which forms the theoretical foundation for electrorefining. It is found that the current two-electrode configuration, while being widely used to purify metals, is incapable of producing ultrahigh purity. A three-electrode configuration is required, in which the potential applied to the anode or the cathode with respect to the reference electrode is the key to produce ultrapure materials. The theory is applied to electrorefining of metallurgical-grade silicon to produce solar-grade silicon. It is suggested that two-step electrorefining is required to remove all the impurities, in which the anode and cathode potentials are controlled in separate steps. The precise anode and cathode potentials for each step are determined from the impurity concentrations in metallurgical-grade silicon and the target impurity concentrations for solar-grade silicon. It is also found that low process temperatures promote effective electrorefining. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Ion-exchange membranes   transport phenomenon   electro-membrane processes   in situ ion substitution   separation   water splitting  

摘要： Membrane-based separation processes are achieving a remarkable attention both in academics and industrial research due to the versatility and economic considerations. Ongoing challenges in water and wastewater treatment, food and biotechnology industries accelerating applications of electro-membrane processes. Intensified research on ion-exchange membranes (IEMs) based electro-membrane processes has been accomplished during recent years to produce potable water and downstream processes for biomolecules separation and recovery. The choice of proper membrane, design and operational optimization of the process are highly essential for successful commercialization of any process. Thus, the development of cost effective membranes by eco-friendly route is highly required for researchers working in the field of membrane development by electro-membrane-based processes. This review provides a brief summary of different preparative procedures for IEMs, transport phenomenon and their applications in electro-membrane separation processes. The most relevant studies have been discussed.

关键词： Co-axial diamond wheel-tool array   Electrochemical co-deposition   RWEDM technique  

摘要： This study presents a novel hybrid technique for fabricating a multi-edged co-axial micro diamond wheel-tool array. The technique combines an electrochemical process with a RWEDM (Rotary Wire Electrical Discharge Machining) technique to precisely electroform a diamond wheel-blank and then produce a coaxial wheel-tool array. A duplex tank design, containing a mini-tank made of porous aluminium-dioxide material is developed for the electrochemical co-deposition of a nickel-based diamond matrix onto a cylindrical aluminium alloy substrate. Optimal conditions for the co-deposition are examined and tested in the production of the wheel-blank. A small RWEDM mechanism that uses permanent magnet tension braking to maintain wire tension and reduce wire vibration is also proposed. The RWEDM process is used for slicing, truing and dressing the grinding edges of the blank. Experimental findings and machining examples show that the proposed novel hybrid process can successfully fabricate a co-axial diamond wheel-tool with a grinding-edge array that has extremely thin high integrity cutting edges. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Oxides   Sol-gel chemistry   X-ray diffraction   Microstructure   Electrochemical properties  

摘要： Lithium-ion battery cathode material Li1+xV3O8 was synthesized by a tartaric acid assisted sol-gel method and thermally treated at 350 degrees C, 450 degrees C and 550 degrees C for 3 h for the formation of Li1+xV3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD and charge-discharge tests. Li1+xV3O8 material synthesized by tartaric acid assisted route, followed by heat treatment at 450 degrees C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g(-1) and still reserves a discharge capacity of 260 mAh g(-1) after 50 cycles. Moreover, for all tartaric assisted products, no capacity decadence is observed in 50 cycles. The in situ X-ray measurements reveal a two-phase transition mechanism in the lithium intercalation/deintercalation process. During lithium extraction, the structure of the delithiated compound changes from Li4V3O8 (x > 3.1) to the original LiV3O8 phase (x < 1.4) via the coexistence state of these two phases (1.4 < x < 3.2). An obvious contraction, especially at Li(3)-Li(4) transition, along a axis and a slight expansion along b axis are also observed. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Electric double layer capacitors   Solid polymer electrolytes   Electrospinning   Poly(acrylonitrile)   Compression molding  

摘要： The electrochemical characteristics of electric double layer capacitors composed of solid polymer electrolytes with different thicknesses were investigated. A solid polymer electrolyte membrane was fabricated using electrospun fibers through solvent-assisted or thermally induced compression molding. Through the solvent-assisted or thermally induced compression molding processes, the poly(acrylonitrile) (PAN) microfibers consolidated together by the interlocking of the fibers under compression. A solid polymer electrolyte membrane clearly exhibited a free-standing shape with a bending capability. The electrospun PAN non-woven fabric and electrolyte salt composites showed higher ionic conductivity (>10(-3) S cm(-1) at 298 K) and capacitance compared with the liquid organic electrolyte. The solid polymer electrolytes provided a 10.6% increase in the energy density, seemingly due to the decrease in the IR drop and increase in the capacitance. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Ballast water   E. coli   Electrochemical disinfection   Kinetics modeling  

摘要： The invasion of biological organisms via ballast water has created threats to the environment and human health. In this study, a cost-effective electrochemical disinfection reactor was developed to inactivate Escherichia coli, one of the IMO-regulated indicator microbes, in simulated ballast water. The complete inactivation of E. coli could be achieved within a very short time (150, 120, or 60 s) with an energy consumption as low as 0.0090, 0.0074 or 0.0035 kWh/m(3) for ballast water containing E. coli at concentrations of 10(8), 10(7) and 10(6) CFU/100 mL, respectively. Electrochemical chlorination was the major disinfection mechanism in chloride-abundant electrolytes, whereas oxidants such as ozone and free radicals contributed to 20% of the disinfection efficiency in chloride-free electrolytes. Moreover, a disinfection kinetics model was successfully developed to describe the inactivation of E. coli. (C) 2012 Elsevier Ltd. All rights reserved.