关键词： LiFePO4   Melt synthesis   Iron ore concentrate   Compositions   Impurities  

摘要： LiFePO4 was prepared from low-cost iron ore concentrate (containing 4.48 wt.% SiO2 and MgO, CaO and Al2O3 below 0.5 wt.% as contaminant) using a melt synthesis. X-ray diffraction (XRD) refinement associated with Mossbauer spectroscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) analyses are used to track the location of Si in the material. It is shown that the iron content in the melt can be used as a means to control the doping rate of elements from iron ore concentrate (IOC) precursor according to the formula (Li1 - z A (z) )(Fe1 - y M (y) )(P1 - x Si (x) )O-4. Electrochemical behavior of the material is affected by the doping of LiFePO4. While capacity is decreased in doped material, the cycling stability is much improved. When dopants are out of LiFePO4 structure, capacity retention dramatically drops as well as capacity due to the gravimetric impact of impurity phases. A trade-off between high capacity and best cycling performance is necessary. For instance, slight lack of iron in the melt (6 % deficiency) leads to a capacity only 2 % lower than that of pure Fe2O3-based material for the same stoichiometry and fairly good capacity retention.

关键词： Mn3O4   Nanoparticles   Alkalinity-controlled synthesis   Pseudocapacitors  

摘要： Mn3O4 nanoparticles were prepared at 60 A degrees C in ethanol solution by a facile precipitation method. It was found that the particle size of the as-prepared Mn3O4 depended on the alkalinity of precipitants. Nanoparticles with average size of 6 nm were obtained by using morpholine as precipitant which had low alkalinity, while 10 nm particles were produced by using NaOH as precipitant. The former particles presented higher degree electrochemical double-layer capacitor-like behavior and higher electrochemical performance than the latter. This could be attributed to the effective faradaic reactions of particles, which originated from the low equivalent series resistance resulting from their smaller particle size. Mn3O4 nanoparticles were prepared in ethanol by a facile precipitation method using precipitants with different alkalinity. It was found that smaller particles (a) were generated by using precipitant with low alkalinity as compared with the one with higher alkalinity (b). As a result, the Mn3O4 nanoparticles presented a high-degree electrochemical double-layer capacitor-like behavior due to their low equivalent series resistance.

关键词： ion exchange membrane   electrochemical impedance spectroscopy   direct current method   diffusion boundary layer thickness   electrochemical properties  

摘要： Electrochemical impedance spectroscopy (EIS) and direct current method (DC) are two powerful techniques to investigate the electrochemical properties in ion exchange membrane transport processes. This work investigated the resistance of membrane systems obtained by EIS and DC with different solution velocity and temperature. Analysis of experimental data from EIS revealed that EIS can be used to analyze each sublayer of ion exchange membrane systems separately and quantitatively and that the resistance of interfacial layers was related to Donnan exclusion. The Bode plots of EIS data were corrected for ohmic resistance to determine the evident constant phase element (CPE) behavior in the data, and the effects of flow velocity and temperature on ohmic-resistance-corrected Bode plots were also analyzed. With the comparison of data obtained from EIS and DC, the sum of pure membrane resistance, diffusion boundary layer resistance and electrical double layer resistance determined by EIS equaled to the overall resistance of membrane systems determined by DC. The results confirmed the linear relationship between the overall conductivity of membrane systems from DC and the pure membrane conductivity from EIS. These results are of major importance for applications of ion exchange membranes in various electro-membrane processes and applications of EIS on characterization of membrane transport properties. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Ultrasonic vibrations   Electrochemical honing (ECH)   Bevel gears   Tooth finishing   MRR   EN8  

摘要： Electrochemical honing (ECH) is a novel variant of hybrid machining processes (HMPs). The key feature is that the distinct coupling of electrochemical machining (ECM) and honing provide a controlled functional surface generation and faster material removal rate in a single operation. In the present study, the influence of ultrasonic vibrations on process performance of ECH of bevel gears made of EN8 is investigated. An analysis of the process has been presented with suitable illustrations. Ultrasonic frequency and processing time were considered as the input variables while improvement in surface finish, material removal and geometrical accuracies were considered as the monitored output. The effectiveness of the process was investigated through experimental trials by conducting a comparison study between classical ECH and ultrasonic vibration-assisted ECH (UECH). The results confirm that improvements in surface roughness and martial removal rate are significantly higher than those obtained with classical ECH. The study further reveals that the scrubbing of the oxide layer is easier to be achieved and surface quality is obviously improved due to ultrasonic vibrations. The experimental results demonstrate that UECH gives 18.36 % improvement in average roughness, 9.31 % improvement in maximum roughness and 20 % improvement in material removal rate as compared with ECH.

关键词： Proton diffusion   Manganese dioxide cathode   Impedance   EMD   NMD  

摘要： The aim of the present work is the study of the performances of dry cells containing the electrolytic MnO2, natural MnO2, or a mixture of both. The two components have been characterized by chemical analysis. The continuous discharge tests done on the dry cells based on EMD present a discharge time largely greater than that of the pure NMD;however, the cells containing a mixture present intermediate values of the discharge time. The value of the diffusion coefficient estimated by the GITT or impedance spectroscopy shows that the H+ diffuses more quickly in the EMD variety that in the NMD one.

关键词： MICROCHEMISTRY   INFRARED spectroscopy   ELECTROCHEMISTRY   SYNCHROTRON radiation   OXIDATION-reduction reaction   CARBON electrodes  

摘要： We describe a method for addressing redox enzymes adsorbed on a carbon electrode using synchrotron infrared microspectroscopy combined with protein film electrochemistry. Redox enzymes have high turnover frequencies, typically 10-1000 s(-1), and therefore, fast experimental triggers are needed in order to study subturnover kinetics and identify the involvement of transient species important to their catalytic mechanism. In an electrochemical experiment, this equates to the use of microelectrodes to lower the electrochemical cell constant and enable changes in potential to be applied very rapidly. We use a biological cofactor, flavin mononudeotide, to demonstrate the power of synchrotron infrared microspectroscopy relative to conventional infrared methods and show that vibrational spectra with good signal-to-noise ratios can be collected for adsorbed species with low surface coverages on microelectrodes with a geometric area of 25 x 25 mu m(2). We then demonstrate the applicability of synchrotron infrared microspectroscopy to adsorbed proteins by reporting potential-induced changes in the flavin mononudeotide active site of a flavoenzyme. The method we describe will allow time resolved spectroscopic studies of chemical and structural changes at redox sites within a variety of proteins under precise electrochemical control.

关键词： Electrochemical discharge machining   Micromachining   ECDM variants   Triplex hybridization  

摘要： Electrochemical discharge machining (ECDM) is a hybrid non-conventional machining process, used to machine electrically conductive and non-conductive materials. It is a preferred process to fabricate micro scale features like micro holes, micro channels, microgrooves and 3-dimensional intricate shapes on variety of materials. In order to improve the efficacy of ECDM process, certain technical augmentations are provided with basic configuration of ECDM. These augmentations result in developments of ECDM process variants. Further, research community has developed ECDM based triplex hybrid methods for further process enrichment. This review article presents a comprehensive review of these recent developments in ECDM process, its variants and their triplex hybrid methods. The future research possibilities are identified and presented as research potentials. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Operating cost   Electrochemical peroxidation process   Acid yellow 194   Response surface methodology  

摘要： In this study, electrochemical peroxidation was employed to remove color and total organic carbon (TOC) from co-complex (acid yellow 194) dye using iron electrodes in a batch-mode operation. The effects and relationships of the process variables were evaluated, and optimizations were carried out using response surface methodology to maximize removal efficiencies and minimize operating costs in relation to energy, electrode, and chemical (such as H2O2) consumptions. The initial pH (2.0-6.0 pH(i)), conductivity (500-2,500 mu S/cm, k), initial dye concentration (100-800mg/L, C-0), current density (10-30A/m(2), j), operating time (4-20min, t), and dosage of H2O2 (2-10mM or 175-860 mu L/L, [GRAPHICS] ) were selected as independent variables. The proposed models fit very well with experimental data, evidenced by high R-2 correlation coefficients (>90%). Maximum color removals were 98 and 80% when C-0 was 275 and 625mg/L, respectively. In contrast, maximum TOC removals were poor (52 and 40% when C-0 was 275 and 625mg/L, respectively). On the other hand, color and TOC removals were found to be 86 and 33.5%, respectively, at optimum conditions (C-0, 275mg/L;pH(i) 3;[GRAPHICS] , 1.010 mu S/cm;[GRAPHICS] , 5.1mM;j, 15A/m;and t, 8.02min). The calculated operating cost at optimized conditions was 0.647euro/m.

关键词： 中国汽车产业   大众汽车   进程   电气化   混合动力   本土化生产   中国市场   品牌计划  

摘要： 大众汽车全力推进纯电动与混合动力车型的研发进程。在未来三至四年内，大众汽车品牌计划在中国市场，推出七款全新的本土化生产的纯电动或捅电式混合动力车型。为了达成这个目标，大众汽车还计划在中国设立一个全新的设计与研发中心。

关键词： Copper-phthalocyanine dye   Electrochemical oxidation   Electro-Fenton   Oxidation products   Photoelectro-Fenton  

摘要： The degradation of the copper-phthalocyanine dye Reactive Blue 15 dye in sulfate medium has been comparatively studied by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments with 100 cm(3) solutions of 0.203 mmol dm(-3) dye were performed with a stirred tank reactor containing a boron-doped diamond (BDD) anode and an air-diffusion cathode for continuous H2O2 production. Experimental conditions of pH 3.0 and 0.50 mmol dm(-3) Fe2+ as catalyst were found optimal for the EF process by the predominant oxidation with hydroxyl radicals formed in the bulk from Fenton's reaction between added Fe2+ and generated H2O2. The kinetics of Reactive Blue 15 abatement was followed by reversed-phase HPLC and always obeyed a pseudo-first-order reaction. The decolorization rate in EO-H2O2 was much lower than dye decay due to the formation of large quantities of colored intermediates under the action of hydroxyl radicals generated at the BDD anode from water oxidation. In contrast, the color and dye removals were much more rapid in EF and PEF by the most efficient oxidation of hydroxyl radicals produced from Fenton's reaction. PEF was the most powerful treatment owing to the photolytic action of UVA irradiation, yielding 94% mineralization after 360 min at 66.7 mA cm(-2). The effect of current density over the performance of all methods was examined. LC-MS analysis of treated solutions allowed the identification of 25 aromatic and heteroaromatic products and 30 hydroxylated derivatives. Tartaric, acetic, oxalic and oxamic acids were quantified by ion-exclusion HPLC. Acetic acid was the only product remaining after PEF and its large persistence explained the almost total mineralization achieved by this process. Chloride, sulfate, nitrate and in smaller proportion, ammonium ions were released to the solution in all cases. A plausible reaction sequence for Reactive Blue 15 mineralization has been finally proposed. (C