The effect of ␥-Al 2 O 3 nanopowder electrolyte concentration and rotation rate on copper reduction from sulfuric acid electrolytes was examined with rotating disk electrodes. Regions of copper inhibition and enhancement were identified in the kinetic regime, with little change in the mass-transport copper limiting current density. Low particle electrolyte concentration ͑12.5 g/L͒ resulted in an inhibited copper rate, while high particle concentration ͑60 g/L͒ inhibited the rate at low overpotentials and accelerated it at higher overpotentials, depending on the electrode rotation rate. Scanning electron microscopy ͑SEM͒ analysis does not support a correlation between the observed inhibition and enhancement with microstructural surface area.
Transition of PEM fuel cells to the commercial market requires low-cost components, materials and manufacturing processes. Considering that bipolar plate manufacturing currently contributes to a significant percentage of the total fuel cell manufacturing cost, an inexpensive bipolar plate manufacturing process must be realized for fuel cells to achieve prominence in the commercial energy sector. A through-mask electro-etching process for high volume manufacturing of stainless steel bipolar plate gas flow field channels is being developed using pulse and pulse reverse electric fields. It has been demonstrated that the process can achieve a uniform channel depth, exhibits good repeatability for multiple experiments performed under the same conditions and the undercut beneath the photoresist mask varies linearly with channel depth indicating that pattern design compensation prior to photoresist patterning of the substrate to achieve the dimensional accuracy of the gas flow field channels and ribs is possible.
Research work performed to develop a functional and decorative trivalent chromium plating process from a single, simple to control trivalent-based electrolyte to replace hexavalent chromium plating will be reported. Hexavalent chromium plating has been used for many years to provide hard, durable coatings with excellent wear and corrosion resistance properties. However, hexavalent chromium baths have come under increasing scrutiny due to the toxic nature of the bath, effects on the environment, and workers' health. In this work, Faraday is updating its accomplishments to date to achieve properties comparable to existing hexavalent chromium plating for both functional and decorative applications. Continuing work on the bath chemistry, diffusion layer, hydrodynamics, and electrically mediated process parameters will also be discussed.
A pulse and pulse reverse through mask electrochemical machining (ECM) process is being developed for fabrication of gas flow field channels on metal bipolar plates used in PEM fuel cells. The process involves patterning a photoresist mask on the surface of the bipolar plate to protect specific areas during the ECM process. A pulsed electric field is applied between the bipolar plate and a suitable counter electrode to remove the metal not protected by the photoresist mask. The application of pulsed electric fields, as opposed to constant direct current (DC) electric fields provides an improved level of control through optimization of the pulse parameters. The influence of the through mask pulse and pulse reverse ECM processing parameters, such as electrolyte composition, flow rates, pulsed voltage, pulsed on-times and off-times on material removal rates, surface finish, accuracy and dimensional control for the channel fabrication are examined.
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