Electrochemical Manufacturing Research Articles

Electrochemical manufacturing of nanocarbons from carbon dioxide in molten alkali metal carbonate salts: roles of alkali metal cations

One simple and fast way to manufacture a useful product from CO2 is to capture the gas by, and then carry out electrolysis in molten alkali metal carbonates. Carbon electro-deposition in molten Li2CO3-Na2CO3-K2CO3 (molar ratio: 43.5:31.5:25.0) has been widely reported in literature. However, studies in each of the individual alkali metal carbonates either have received less attention or are simply lacking in literature. Electrochemical studies of these molten carbonates are important to understand their underlying processes and reactions during the electrolysis. In this work, cyclic voltammograms (CVs) were recorded in each of the above-mentioned molten alkali carbonate salts using a 0.25 mm diameter Pt wire working electrode. In molten Na2CO3 and K2CO3, the main cathodic reaction was likely the formation of alkali metal, while that in Li2CO3 was carbon deposition. The results also suggest that other competing reactions such as CO and alkali metal carbide formation are possible as well in different molten salts. On the CVs, the anodic current peaks observed are mostly associated with the oxidation of cathodic products. Flake/ring/sheet-like structures and quasi-spherical particles were observed in the produced carbon. The morphology of the carbon contained both amorphous and graphitic structures, which varied with different electrolysis variables.

Electrochemical Manufacturing in the 21st Century

Electrochemical Manufacturing in the 21st Century

Electrochemical Manufacturing in the Chemical Industry

There are over 100,000 chemicals in the marketplace, manufactured by various technological means. Despite this large number of chemicals available in the market, electrochemical synthesis of chemicals has been limited to a narrow spectrum. The reasons for this have been previously attributed to a lag in the education of chemists and engineers in electrochemistry and electrochemical engineering, a lack of suitable resources for cell construction, and most importantly the prohibitive costs involved (in many cases) in electrochemical synthesis. However, over the past 40 years, there have been significant developments in electrochemical synthesis and methods due to the advances in materials science and nanotechnology, and progress in multi-scale modeling. The mainstays of electrochemical manufacturing (chlor-alkali industry, aluminum, organic synthesis) as well as new vistas of manufacturing are explored.

Impedance Based Characterization of Raw Materials Used in Electrochemical Manufacturing

Impedance Based Characterization of Raw Materials Used in Electrochemical Manufacturing

Electrochemical Surface Finishing

Electrochemical surface finishing is a highly scalable manufacturing process that traditionally uses viscous, non-aqueous and/or highly acidic electrolytes to achieve the desired surface profiles on metallic parts, with the addition of aggressive, hazardous chemical species to remove the oxide film on strongly passive materials. An emerging approach applies pulse and pulse reverse electric fields to control current distribution, mitigate oxide film formation and achieve the desired surface finish, in the presence of environmentally benign and simple chemistries. This approach lowers the cost of the manufacturing process, and improves process robustness. After a brief discussion of electrochemical surface finishing processes, case studies that describe deburring of automotive gears and electropolishing of semiconductor valves and superconducting radio frequency cavities are presented in this article. Conventional Electrochemical Surface Finishing Processes Electrochemical surface finishing removes metal in a selective manner from the surface of the workpiece by converting the metal into ions by means of an applied electric field. This is accomplished in an electrolytic cell by applying a positive (anodic) potential to the workpiece and a negative (cathode) potential to the tool used to shape the workpiece. While fundamental investigations of electrochemical metal removal processes typically employ a 3-electrode system, a manufacturing environment is typically not conducive to the use of reference electrodes. Therefore, most electrochemical manufacturing systems are based on a two-electrode cell. Conventional electrochemical surface finishing relies heavily on the “art” of chemical mediation for process control. Under the influence of a constant electric field and controlled electrolyte flow, aggressive chemical species diffuse to the electrochemical interface and control the preferential dissolution of asperities from a surface via an electrolytic reaction, which may be generally represented as:

Electrochemical micromachining with ultra short voltage pulses

The machining technology of electrochemical micromachining with ultra short voltage pulses (μPECM) is based on the already well-established fundamentals of common electrochemical manufacturing technologies. The enormous advantage of the highest manufacturing precision underlies the fact of the extremely small working gaps achievable through ultra short voltage pulses in nanosecond duration. This describes the main difference with common electrochemical technologies. With the theoretical resolution of 10 nm, this technology enables high precision manufacturing [4].

Investigations of X-ray metallic capillaries

In our previous contributions [R. Mroczka, G. Żukociński, A. Kuczumow, J. Alloys Compd. 362 (2004) 88–95; R. Mroczka, G. Żukociński, A. Kuczumow, Geometrical description of the X-ray capillary and total reflection mirror surfaces with assumed reflection features, J. Alloys Compd. 382 (2004) 311–319], we solved the problem of analytical description of capillaries with designed reflection features. Now, the numerical program for ray tracing simulations was written, fully basing on our original analytical calculation of trajectories. All parameters essential for X-ray capillary optics system, such as point and extended X-ray sources, different ranges of photon energy, geometrical parameters of capillaries, variable surface roughness, different kinds of materials (mainly metals), location of target in relation to capillary, were tested. Profiles of output photon beam on the target were obtained. Here, some results of simulations, such as the influence of the photon energy, the capillary sizes and the internal wall smoothness on the efficiency of propagation were presented. All simulations were helpful in making decisions about the optimal shapes and parameters of capillaries that were manufactured in our laboratory. In the preliminary experimental work, the electrochemical manufacturing of capillaries with the metallic (Cu and Ni) walls was described. The cathode wire was coated with copper layer in controlled electrolytic process. It led to precise formation of the parabolic shape of a core part. Subsequently, a thin layer of nickel was coated in electroless way and electrochemically passivated. Then, a thin copper layer and subsequently, thick nickel one were electroplated, forming the body part of the capillary. The adjustment of the internal walls of the capillaries to the designed shape was controlled with the electron microscope and it was proved that it could be kept within ±1 μm scatter on a distance of several centimeters along the main axis. The roughness (rms) of the internal capillary walls was controlled by the atomic force microscope. The roughness was kept in the range of 3.5–5 nm and was in the low limit of allowed levels. The production will be optimized in the future.

Design of Electrode Profile In Electrochemical Manufacturing Process

Accurate prediction of electrode shapes is most important in electrochemical manufacturing process which includes electrochemical machining and electroforming. In the former process, the electrode design is focused on the prediction of the cathode tool which significantly affects the machining accuracy. In the electroforming process, the anode electrode shape determines the current density distribution and so the properties of the deposited metal. This paper proposes a finite element approach to accurately determine these electrode profiles. The proposed method does not require Iterative redesign process, therefore provides excellent convergence and efficient computing. Close agreements between theoretical and experimental results have been observed.

Electrosynthesis of Sodium Hydrosulfite: II. The Effect of Cathode Material

Sodium hydrosulfite is a major commodity reagent currently manufactured mainly by chemical means. A new, lower cost, electrochemical pathway is being used in some cases. One of the key determinants in the marketability of sodium hydrosulfite is the level of sodium thiosulfate in the product. At present, the level of thiosulfate from the electrochemical process is higher than that from the chemical process. Here a critical evaluation is presented of cathode materials for the electrochemical manufacture of sodium hydrosulfite nearly devoid of thiosulfate. It is demonstrated that the yield, selectivity, and efficiency of hydrosulfite and thiosulfate production depends upon the applied potential, pH of the feedstream, buffering capacity, and cathode material. Several planar cathodes for the electrosynthesis of hydrosulfite have been critically evaluated. We demonstrate that five main process parameters contribute to high hydrosulfite to thiosulfate ratios; reactant concentration, feedstream pH, buffer capacity, cathode material, and applied potential. By control of these parameters, we demonstrate that hydrosulfite solutions devoid of thiosulfate can be electrochemically produced.

Towards the electrochemical manufacture of superconductor precursor films in the presence of an ultrasonic field

Films of TI-Pb-Sr-Ca-Cu superconductor precursor material have been synthesised. The films were electrodeposited onto polished Ag substrates, with and without the presence of an ultrasonic field in the solution, by applying a pulsed potential sufficiently large to cause reduction of the appropriate metallic cations. The deposition solution was composed of dehydrated metallic nitrate salts dissolved in dimethylsulfoxide. The morphology, and the compositions, of the films were analysed using scanning electron microscopy and emission dispersive spectroscopy respectively. Deposition in the presence of the ultrasonic field showed an increased deposition current, by a factor of 4, caused by mass transfer enhancements as a result of cavitation effects produced by the ultrasonic irradiation of the solution. These films were denser compared with those deposited without the presence of the ultrasound, displaying a void percentage of around 45%, and also displayed greater morphological homogeneity.

Copper-to-aluminum transitions in high DC bus systems

A number of papers have discussed issues related to electrical applications of various types of copper-to-aluminum transitions. Little field experience, however, has been discussed. This paper describes techniques used at a large electrochemical manufacturing site for making copper-to-aluminum transitions in high DC bus systems. After a brief historical treatment of problems with bolted copper-to-aluminum transitions, various explosion-bonded and roll-bonded bus transition designs and experiences are discussed. Two roll-bonded copper-to-aluminum transition designs are described, with mixed performance records. Some specific explosion-bonded transition designs are described, along with an explosion-bonded copper-to-aluminum transition with a titanium interlayer to permit the use of higher fabrication temperatures, without detriment to the strength of the metal-to-metal bond. Explosion-bonded transitions are shown to have good performance records.