568,056 research outputs found

    Side wire feed for welding apparatus

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    Coaxial electrode arrangement has solid central electrode, insulated outer electrode, and transverse channel for feeding wire through tip of electrode assembly. Polymeric insulation is thrust aside by pressure, which is provided by separately operated mechanism acting through central electrode

    Multistage depressed collector for dual mode operation

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    A depressed collector which captures the spent electrons of a microwave transmitting tube at high efficiency in both high and low power modes of operation is described. The collector comprises entrance and end electrodes, the end electrode having a spike extending toward entrance electrode. Intermediate electrodes and the entrance electrode each have a central aperture and, together, these electrodes capture most high power mode spent electrons. The apertures of the electrodes increase in size in a downstream direction. To capture low power mode spent electrons a low power mode electrode is positioned between the last intermediate electrode and the end electrode. This electrode has a central aperture preferably smaller but no larger than that of the last intermediate electrode. An auxiliary low power mode electrode may be added having a central aperture larger than that of the low power mode electrode. All of the electrodes are at voltages provided by a voltage divider connected between a potential

    Influence of normal and radial contributions of local current density on local electrochemical impedance spectroscopy.

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    A new tri-electrode probe is presented and applied to local electrochemical impedance spectroscopy (LEIS) measurements. As opposed to two-probe systems, the three-probe one allows measurement not only of normal, but also of radial contributions of local current densities to the local impedance values. The results concerning the cases of the blocking electrode and the electrode with faradaic reaction are discussed from the theoretical point of view for a disk electrode. Numerical simulations and experimental results are compared for the case of the ferri/ferrocyanide electrode reaction at the Pt working electrode disk. At the centre of the disk, the impedance taking into account both normal and radial contributions was in good agreement with the local impedance measured in terms of only the normal contribution. At the periphery of the electrode, the impedance taking into account both normal and radial contributions differed significantly from the local impedance measured in terms of only the normal contribution. The radial impedance results at the periphery of the electrode are in good agreement with the usual explanation that the associated larger current density is attributed to the geometry of the electrode, which exhibits a greater accessibility at the electrode edge

    Fundamental electrode kinetics

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    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics

    Evaluation of Constant Potential Method in Simulating Electric Double-Layer Capacitors

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    A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations induced by charge fluctuations in the electrolyte. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [Reed, et al., J. Chem. Phys., 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain constant electric potential in each electrode. For this comparison, we utilize a simplified LiClO4_4-acetonitrile/graphite EDLC. At low potential difference (ΔΨ≤2V\Delta\Psi\le 2V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ\Delta\Psi. At ΔΨ≥4V\Delta\Psi\ge 4V, the CPM ion density profiles show significant enhancement (over FCM) of "partially electrode solvated" Li+^+ ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li+^+ ions to the electrode surface.Comment: Corrected typo

    Oxygen transport and transfer properties of erbia-stabilized bismuth oxide

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    The electrode resistances of solid solutions of 75 mol% Bi2O3−25 mol% Er2O3 with sputtered and with copressed gold gauze electrodes were compared. In contrast with literature no enhancement of the electrode process could be observed for the copressed electrodes. The measurements show an oxygen partial pressure dependence of power−0.5 for the electrode resistance. Additionally 18O2 exchange results also point to a low oxygen coverage and dissociative adsorption of oxygen. The electrode surface contributes significantly to the electrode process

    Factors Affecting Nickel-oxide Electrode Capacity in Nickel-hydrogen Cells

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    The nickel-oxide electrode common to the nickel hydrogen and nickel cadmium cell is by design the limiting or capacity determining electrode on both charge and discharge. The useable discharge capacity from this electrode, and since it is the limiting electrode, the useable discharge capacity of the cell as well, can and is optimized by rate of charge, charge temperature and additives to electrode and electrolyte. Recent tests with nickel hydrogen cells and tests performed almost 25 years ago with nickel cadmium cells indicate an improvement of capacity as a result of using increased electrolyte concentration

    Plasma jet electrode has longer operating life

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    Water-cooled, silver-infiltrated tungsten electrode has twice the operating lifetime of the pure tungsten electrode used in plasma jet generators. This electrode reduces the erosion rate, ensures excellent heat transfer, and reduces thermal stresses

    Li-diffusion accelerates grain growth in intercalation electrodes: a phase-field study

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    Grain boundary migration is driven by the boundary's curvature and external loads such as temperature and stress. In intercalation electrodes an additional driving force results from Li-diffusion. That is, Li-intercalation induces volume expansion of the host-electrode, which is stored as elastic energy in the system. This stored energy is hypothesized as an additional driving force for grain boundaries and edge dislocations. Here, we apply the 2D Cahn-Hilliard−-phase-field-crystal (CH-PFC) model to investigate the coupled interactions between highly mobile Li-ions and host-electrode lattice structure, during an electrochemical cycle. We use a polycrystalline FePO4_{4}/ LiFePO4_{4} electrode particle as a model system. We compute grain growth in the FePO4_{4} electrode in two parallel studies: In the first study, we electrochemically cycle the electrode and calculate Li-diffusion assisted grain growth. In the second study, we do not cycle the electrode and calculate the curvature-driven grain growth. External loads, such as temperature and stress, did not differ across studies. We find the mean grain-size increases by ∼11%\sim11\% in the electrochemically cycled electrode particle. By contrast, in the absence of electrochemical cycling, we find the mean grain-size increases by ∼2%\sim2\% in the electrode particle. These CH-PFC computations suggest that Li-intercalation accelerates grain-boundary migration in the host-electrode particle. The CH-PFC simulations provide atomistic insights on diffusion-induced grain-boundary migration, edge dislocation movement and triple-junction drag-effect in the host-electrode microstructure.Comment: 11 pages, 9 figure
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