Use Of Current Densities Research Articles

The influence of current density, rest time and electrolyte composition on the self-discharge of organic radical polymers

In this work we report a systematic study about the influence of the charging current density and the rest time on the self-discharge of poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA) based electrodes in two model electrolytes, namely 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI, IL) and 1 M Pyr14TFSI in propylene carbonate (PC). We show that for each electrolyte it is possible to identify a threshold of current density (and thus C-rate) which can be safely applied without increasing the electrode self-discharge. Furthermore, we show that the self-discharge of the PTMA-based electrodes is originated by a combination of activation controlled faradic processes, charge redistribution and diffusion limited processes. The use of current densities above the threshold is causing an improper charging process, which leads to faradic reactions on the surface of the eletrode followed by the redistribution of charge on the surface of the electrodes and causes a fast energy loss when a current is no longer applied. When current densities below the threshold are used, the diffusion of redox shuttles becomes the driving force of self-discharge taking place in PTMA based electrodes.

Pengaruh Rapat Arus Proses Continuous Hard Anodizing Elektrolit (H2SO4) terhadap Laju Korosi Pipa Aluminium 6061 dengan Pengujian Kabut Garam

Anodizing is an electro-chemical process used to coat metal surfaces with a stable oxide layer. The function of this oxide layer is to increase corrosion resistance. The purpose of this study is determine the effect of variations in current density on the continuous hard anodizing process carried out in sulfuric acid electrolyte solution (H2SO4) on the corrosion rate of aluminum alloy 6061. Corrosion rate testing is carried out through salt fog testing. The values of the current variation used are 1 A/dm2; 2 A/dm2; 3 A/dm2; 4 A/dm2; and 5 A/dm2. Statistical calculations using the analysis of variance proved the current density in the anodizing process has a significant effect on the corrosion resistance of the anodizing workpiece. Corrosion testing provides information that the highest corrosion rate is an anodizing workpiece with a current density of 1 A/dm2, which is 125.6861 mdd, then 2 A/dm2 of 104.33333 mdd. The lowest corrosion rate value obtained at the use of current density 3 A/dm2, that is 51,8083 mdd. Meanwhile, the use of current density of 4 A/dm2 has a slightly higher corrosion rate compared to the use of current density of 3 A/dm2, which is 86.5444 mdd. Furthermore, the use of current density of 5 A/dm2 has the highest decay rate, so that the formed oxide layer will be damaged, as seen from the higher corrosion rate of the material, which is 100.8361 mdd.

Cyclic voltammetric acetylcholinesterase biosensor for the detection of captan in apple samples with the aid of chemometrics.

The presence of captan residues in apples shows high toxicity, which often causes eye and skin irritation, dermatitis, conjunctivitis, and vomiting in humans. In this context, an electrochemical biosensor based on acetylcholinesterase (AChE) immobilized on a ZnO nanorod interface has been proposed. In this work, Hill, dose-response, and first-, second-, and third-order polynomial regression models were successfully applied and the prediction ability of these models was tested with the use of current density obtained from the cyclic voltammograms of appropriate captan solutions. The Pt/ZnO/AChE bioelectrode showed a high sensitivity of 0.538 μA cm(-2) μM(-1) in the linear range from 0.05 to 25.0 μM with a limit of detection of 107 nM. The recovery results were observed between 98.4 and 102.4 % from the apple sample. This work provides a new promising tool for the detection of captan in apple samples.

New Technology for Electrorefining of Copper

New electrorefining technology utilizes a novel manifold electrolyte inlet, which allows improving productivity and production in new and existing tankhouses at high current efficiency and very good cathode quality. Two installation examples—Montanwerke Brixlegg AG, Brixlegg, Austria (upgrade existing tankhouse) and Xiangguang Copper, Yanggu, China (new tankhouse)—demonstrate the use of current densities above 400 A/m2 at very high current efficiency in electrorefining.

Galvanostatic Electrophoretic Deposition of Yttriumsilicate on C/C-Si-SiC Composites

The use of carbon fibre reinforced carbon composites in oxidizing atmospheres is limited to temperatures below 400 °C. To benefit from their excellent mechanical strength that is still preserved at high temperatures, suitable oxidation protection coating systems have to be developed. Composites which are capillary infiltrated with Si and coated with SiC via chemical vapour deposition show significantly enhanced oxidation resistance. For the increase of service temperature above 1300 °C, high temperature stable materials with low oxygen diffusivities such as yttrium silicates have to complement the SiC coating. The electrophoretic deposition performed under constant current conditions leads to relatively high green densities and therefore good sinterability of the applied coatings. In this work we present the preparation of suspensions, their characterization regarding particle size and electrophoretic mobility for yttrium silicate powder prepared by the solid state method. Depending on particle charge and conductivity of the investigated suspensions iodine is employed to increase particle charge. The use of current densities between 0.5-5mA/cm² leads to smooth and homogeneous layers. Layers sintered as low as 1400 °C for 2h already show promising protection of the C/C-Si-SiC substrate during thermogravimetric analysis.

Design considerations for the TF coil center conductor post for the Ignition Spherical Torus (IST)

A trade-off study has been carried out to compare the differential costs of using high-strength alloy copper versus oxygen-free, high-conductivity (OFHC) copper for the center legs of the toroidal field (TF) coils of an Ignition Spherical Torus (IST). The electrical heating, temperatures, stresses, cooling requirements, material costs, pump costs, and power to drive the TF coils and pumps are all assessed for both materials for a range of compact tokamak reactors. The alloy copper material is found to result in a more compact reactor and to allow use of current densities of up to 170 MA/mS versus 40 MA/mS for the OFHC copper. The OFHC conductor system with high current density is $24 million less expensive than more conventional copper systems with 30 MA/mS. The alloy copper system costs $32 million less than conventional systems. Therefore, the alloy system offers a net savings of $8 million compared to the 50% cold-worked OFHC copper system. Although the savings are a significant fraction of the center conductor post cost, they are relatively insignificant in terms of the total device cost. It is concluded that the use of alloy copper contributes very little to the economic or technical viability of the compact IST.more » It is recommended that a similar systematic approach be applied to evaluating coil material and current density trade-offs for other compact copper-TF-coil tokamak designs. 9 refs., 13 figs., 13 tabs.« less

Design considerations for the TF coil center conductor post for the Ignition Spherical Torus (IST)

A trade-off study has been carried out to compare the differential costs of using high-strength alloy copper versus oxygen-free, high-conductivity (OFHC) copper for the center legs of the toroidal field (TF) coils of an Ignition Spherical Torus (IST). The electrical heating, temperatures, stresses, cooling requirements, material costs, pump costs, and power to drive the TF coils and pumps are all assessed for both materials for a range of compact tokamak reactors. The alloy copper material is found to result in a more compact reactor and to allow use of current densities of up to 170 MA/m 2 versus 40 MA/m 2 for the OFHC copper. The OFHC conductor system with high current density is $24 million less expensive than more conventional copper systems with 30 MA/m 2 . The alloy copper system costs $32 million less than conventional systems. Therefore, the alloy system offers a net savings of $8 million compared to the 50% cold-worked OFHC copper system. Although the savings are a significant fraction of the center conductor post cost, they are relatively insignificant in terms of the total device cost. It is concluded that the use of alloy copper contributes very little to the economic or technical viability of the compact IST. It is recommended that a similar systematic approach be applied to evaluating coil material and current density trade-offs for other compact copper-TF-coil tokamak designs.

A vector derivation useful in impedance plethysmographic field calculations.

A vector relationship similar to Green's theorem incorporating simplifications which can be made for impedance plethysmography is derived. The mathematics involved are simplified by the use of current density instead of electric field. Geselowitz's lead theory result [1] is rederived and a limitation of such proofs is discussed.