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Regioselectivity of the Electrically Modified Palladium Catalyzed Heck Arylation
Published in Mike G. Scaros, Michael L. Prunier, Catalysis of Organic Reactions, 2017
Steven A. Roberto, Robert L. Augustine
It has been found that the regioselectivity of this reaction depends on a number of factors such as the solvent type, enol ether size, substituent on the aromatic group, and the nature of the catalyst.3 One interesting trend was the change in regioselectivity in the heterogeneously catalyzed reaction which were observed with changes in the nature of catalyst support.4 Electron withdrawing supports such as alumina and silica favor substitution at the β carbon of the enol ether while electron donating supports such as magnesium oxide favors substitution towards the or carbon. With these trends in mind it was thought that a conductive support such as graphite could be induced to act as either an electron donor or an electron acceptor depending on the voltage applied by a potentiostat. A potentiostat is an instrument that maintains a constant potential applied to the working electrode. The electrode system used was a three electrode arrangement consisting of working, reference, and auxiliary electrodes as depicted in Fig. 1.
Towards a standard test for the determination of synergism in tribocorrosion: Detailed testing procedure for passivating materials
Published in J.-P. Celis, P. Ponthiaux, Testing tribocorrosion of passivating materials supporting research and industrial innovation: Handbook, 2017
The test set-up consists of the wear test equipment (tribometer) allowing either rotating ball-on-disc sliding tests or reciprocating ones. The test samples are discs and are fully immersed in the test solution (electrolyte). The counter bodies are loaded on top of the discs and are generally balls or pins with a spherical end. The ball material should be non-conductive to prevent any galvanic coupling with the disc material. A potentiostat is required to perform the electrochemical measurements. A three-electrode set-up has to be installed consisting of a working electrode composed of the polished and cleaned test sample, a counter electrode such as a Pt wire, a Pt plate or a Pt grid, and a reference electrode such as a saturated calomel or silver/silver chloride electrode. The position of the reference electrode is preferably between the wear track and the counter electrode. The risk of distortion of some electrochemical measurements due to a non-uniform distribution of the current lines has to be limited. Therefore, the counter electrode should preferably be in rotating ball-on-disc sliding testers, as a circular electrode positioned with its axis corresponding to the axis of the disc acting as the working electrode. In the case of reciprocating sliding testers, the counter electrode should be flat with a length comparable to the length of the wear track, and positioned parallel to the ball displacement direction.
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Published in Brajendra K. Sharma, Girma Biresaw, Environmentally Friendly and Biobased Lubricants, 2016
Victoria L. Finkenstadt, James A. Kenar, George F. Fanta
The dried films of the starch–soybean oil composites were evaluated for corrosion inhibition on the metal substrates under an electrolyte solution using a potentiostat. A potentiostat is an instrument that controls the voltage difference between a working electrode and a reference electrode. Electrochemical measurements were performed using a PARSTAT 2273 Advanced Potentiostat (Princeton Applied Research, Oak Ridge, Tennessee). Electrochemical impedance was recorded at an alternating current voltage of 10 mV for a frequency range of 0.1 to 10 MHz. The electrochemical cell was equipped with a conventional three-electrode system with a working electrode, a graphite counterelectrode, and a reference electrode (PTC1 Gamry Instruments, Warminster, Pennsylvania). In the corrosion experiment, the metal substrate functions as the working (i.e., corroding) electrode. The test area was approximately 14 cm2. Figure 21.1 shows the experimental setup for the electrochemical cell and potentiostat. Sodium chloride (NaCl; 5% w/v) was used as the electrolyte solution. Analysis was performed using electrochemistry software (PowerCorr, Princeton Applied Research, Oak Ridge, Tennessee) that includes modules specifically designed for corrosion measurements and analysis.
Corrosion properties of ASTM A615 rock bolt steel in US underground coal mines
Published in Mining Technology, 2020
Gopi Bylapudi, Kanchan Mondal, A. J. (Sam) Spearing, Anand Bhagwat
Potentiodynamic polarization resistance tests were performed to determine the corrosion potential (Ecorr), polarization resistance (Rp), and corrosion rates (CR) of the bolt steel in four different strata leachates. To achieve this, an eDAQ potentiostat equipped with e-corder and a personal computer with Echem software is used. The experimental setup operational schematic and the actual laboratory setup can be seen in Figure 5. The electrochemical cell with main components (electrodes, luggin capillary, and temperature sensor) can be seen in Figure 6. The potentiostat controls the potential difference between the reference electrode and the working electrode based on the applied potential. As the potential is applied, the resulting current flow between the working electrode and platinum counter electrode is measured. The measured current versus the applied potential is recorded by e-corder and is sent to the software. The obtained data from the tests are then used to plot the Tafel plots and polarization resistance plots to calculate the Ecorr in mV, Rp in Ω-mm2, and CR in mm/yr.
Corrosion behaviour of an industrial shot-peened and coated automotive spring steel AISI 9254
Published in Corrosion Engineering, Science and Technology, 2018
Mazher Ahmed Yar, Ying Wang, Xiaorong Zhou, Constantinos Soutis
The potentiostatic tests were also conducted to study the material’s accelerated corrosion. In the potentiostatic method, the potential of the working electrode is controlled using a potentiostat at a fixed appropriate value above the OCP. This instrument uses a feedback circuit to pass appropriate currents to the working electrode so that its potential measured against the reference electrode is maintained at the desired value, regardless of variations in current which correspond to changes in the rates of the corrosion reactions. The tested samples were held at a suitable potential of 100 mV above the OCP for different times (from 0.5 h to 5 days) after conditioning by immersion in corroding solution for 1 h to stabilise the free corrosion potential. All corrosion tested samples were also subjected to optical and SEM observations.
Experimental evaluation of henna extract as a corrosion inhibitor additive in sandstone acidizing and its side effect on rock/fluid system
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Reza Abdollahi, Seyed Reza Shadizadeh, Mohammad Hossein Allahyarzadeh
A potentiostat is a precise electronic instrument that measures and controls the voltage and current flow in a two/three electrodes system where these electrodes are immersed in a conductive electrolyte. This device controls the voltage difference among a working electrode and a reference electrode, while it measures the current flow through the working and counter electrodes. Such device is inevitable for modern electrochemical studies to investigate the reaction mechanisms related to redox chemistry and other chemical/electrochemical phenomena.