Anodic, cathodic and cyclic voltammetric deposition of ruthenium oxides from aqueous RuCl3 solutions

Anodic, cathodic and cyclic voltammetric (CV) deposition of ruthenium oxides from aqueous RuCl₃ solutions have been investigated using stationary and rotating disk electrodes (RDE) in this work. The CV deposition behavior was examined using a RDE to differentiate the contribution of current from the reactions of ruthenium ions in the electrolyte and ruthenium oxides already adsorbed on the electrode. The results indicate that the CV growth of ruthenium oxides within the potential range of aqueous electrolyte decomposition is attributed to the anodic oxidation of ruthenium ions in the electrolyte. Cathodic deposition occurs only at potential negative than −0.30 V versus saturated calomel electrode (SCE) when H₂ evolves on the electrodes. Anodic deposition of ruthenium oxides can be obtained effectively in the potential range of ca. 0.9-1.1 V versus SCE, depending on the pH value of the electrolyte. The optimum anodic and cathodic deposition potential for maximum deposition efficiency is 1.0 and −0.9 V versus SCE, respectively, in the electrolyte solution of pH 2.     

Ultrasound initiated maleic anhydride grafted onto a novel polypropylene copolymer

The reaction of maleic anhydride (MAH) grafted onto propylene‐based copolymer (DP) without adding any initiator was conducted through ultrasound assisted extrusion in this article. The effects of ultrasound power, die temperature, and MAH content on the grafting degree and efficiency were studied. With increasing ultrasound power, the grafting degree and efficiency of DP‐g‐MAH increase. The presence of ultrasound with higher power and lower die temperature is beneficial to increase the grafting degree and efficiency. The increase of MAH content can increase the grafting degree but reduce the grafting efficiency. Based on the results of melt flow index, dynamical rheological, gel permeation chromatograph (GPC), and Fourier transform infrared spectroscopy (FTIR) tests, the mechanisms of the grafting reaction were proposed. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Historical introduction to capacitor technology

Over the next several years, this magazine will publish a series of papers, hopefully one per issue, on the subject of capacitor technology. The intention is to cover all important areas of the technology in some detail, including film, ceramic, electrolytic, and double-layer capacitors. One of the authors (S. B.) will edit the series.     

Design and Optimization of Printed Spiral Coils for Efficient Transcutaneous Inductive Power Transmission

The next generation of implantable high-power neuroprosthetic devices such as visual prostheses and brain computer interfaces are going to be powered by transcutaneous inductive power links formed between a pair of printed spiral coils (PSC) that are batch-fabricated using micromachining technology. Optimizing the power efficiency of the wireless link is imperative to minimize the size of the external energy source, heating dissipation in the tissue, and interference with other devices. Previous design methodologies for coils made of 1-D filaments are not comprehensive and accurate enough to consider all geometrical aspects of PSCs with planar 3-D conductors as well as design constraints imposed by implantable device application and fabrication technology. We have outlined the theoretical foundation of optimal power transmission efficiency in an inductive link, and combined it with semi-empirical models to predict parasitic components in PSCs. We have used this foundation to devise an iterative PSC design methodology that starts with a set of realistic design constraints and ends with the optimal PSC pair geometries. We have executed this procedure on two design examples at 1 and 5 MHz achieving power transmission efficiencies of 41.2% and 85.8%, respectively, at 10-mm spacing. All results are verified with simulations using a commercial field solver (HFSS) as well as measurements using PSCs fabricated on printed circuit boards.     

Improving the self-sintering of mesocarbon-microbeads for the manufacture of high performance graphite-parts

Fine spherical mesocarbon-microbeads (MCMBs), having average particle sizes of 24.57, 11.69 and 10.74 μm, were mixed with various amounts of solid-resins (with high β-resin contents) to prepare graphite-matrixes in self-sintering reactions. The results indicate that the self-sintering reactions of the MCMBs can be significantly improved by enhancing the contacting-pattern of the mixture. MCMBs with smaller particle sizes favor self-sintering reactions and can be used to form high-quality graphite-matrixes. In addition, the self-sintering reactions are strongly dependent on the β-resin content of the raw materials. The bending strength of the graphite-matrixes increases, while the density of the graphite-matrixes decreases, with an increase of the β-resin content in the raw materials. The optimum β-resin content in the mixtures needed to obtain high density graphite-matrixes is approximately 5.0 wt.%.     

Co-electrodeposition of Pt–Ru electrocatalysts in electrolytes with varying compositions by a double-potential pulse method for the oxidation of MeOH and CO

The co-eletrodeposition of Pt–Ru on carbon electrodes was carried out using a double-potential pulse method in electrolytes containing varying concentrations of RuCl₃ + H₂PtCl₆ in an attempt to deposit highly dispersed Pt–Ru electrocatalyst with a controlled composition. The amounts of the Pt and Ru deposited on the electrodes were analyzed using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The results revealed that the Pt loading on the substrates increases linearly with H₂PtCl₆ concentrations in the bath while the Ru loading is not related to the concentration of RuCl₃, indicating that the reduction of Pt ions is the dominant reaction in the cathodic deposition of Pt–Ru clusters on the substrate. The Pt–Ru/C electrodes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optimum Ru content in the deposited Pt–Ru electrode for promoting the electro-oxidation of MeOH and adsorbed CO was found to be 25 atm%, by CO-stripping measurements in 0.5 M H₂SO₄ and by cyclic voltammography in a solution comprising CH₃OH (2.0 M) +0.5 M H₂SO₄ (0.5 M). SEM results showed that the generation of nucleation sites and growth of the deposits progresses continuously on carbon substrate and already deposited Pt–Ru particles. The particle size and loading amount of the deposits was found to increase with an increase in the number of cycles of the repeating double-potential pulse.     

Adsorption and electrokinetics of glucose reduction

The kinetics of cathodic reduction of glucose were studied by a rotating disk electrode at rotation speeds from 500 to 6000 rpm and zero to 2.0 M concentration of glucose. Sodium sulfite was used as the supporting electrolyte as well as the reducing mediator. Both the experimental results and the theoretical analysis indicated that several reaction steps occurred for the cathodic reduction of glucose. The results also revealed that the adsorption of glucose on a cathode played an important role during the electrolysis. The reaction mechanism was proposed and a mathematical model was developed. The model correlated well with the experimental results. The rate determining step was found to be the cathodic reduction of the sodium cation. The rate current of the electroreduction of glucose can be expressed as

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