STUDIES ON THE ELECTRO-OXIDATION OF TETRAVALENT URANIUM

1948 ◽  
Vol 26b (5) ◽  
pp. 441-455
Author(s):  
R. H. Betts
Keyword(s):  
Aqueous Solution ◽  
Uranyl Ion ◽  
Ion Concentration ◽  
Anode Potential ◽  
High Current ◽  
Tetravalent Uranium ◽  
Platinum Anode ◽  
Wide Range ◽  
Current Densities ◽  
Electro Oxidation

The conversion of uranous ion to uranyl ion at a platinum anode has been studied over a wide range of current densities and anode potentials. At high current densities, the rate of the oxidation is dependent on the uranous ion concentration and is independent of the particular current density used. At low current densities, the rate of the process increases exponentially with increases in the anode potential and temperature, but is independent of the uranyl ion concentration. It is concluded that at high current densities, the rate of oxidation is limited by the rate of diffusion of uranous ion to the anode, while at low current densities, the rate of the reaction is limited by the slowness in electron transfer between the metallic ion and the anode. A formal correlation is made between the irreversible characteristics of this system and those displayed during the electrodeposition of hydrogen and oxygen from aqueous solution.

scholarly journals Observation of current-induced switching in non-collinear antiferromagnetic IrMn3 by differential voltage measurements

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sevdenur Arpaci ◽  
Victor Lopez-Dominguez ◽  
Jiacheng Shi ◽  
Luis Sánchez-Tejerina ◽  
Francesca Garesci ◽  
...  
Keyword(s):  
Spin Orbit ◽  
High Current ◽  
Experimental Protocol ◽  
Micromagnetic Simulations ◽  
Differential Voltage ◽  
Magnetic Switching ◽  
Wide Range ◽  
Current Densities ◽  
Pass Through ◽  
Double Cross

AbstractThere is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling AFM order via spin-orbit torques, and its read-out via magnetoresistive effects. Recent studies have shown, however, that high current densities create non-magnetic contributions to resistive switching signals in AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we introduce an experimental protocol to unambiguously distinguish current-induced magnetic and nonmagnetic switching signals in AFM/HM structures, and demonstrate it in IrMn3/Pt devices. A six-terminal double-cross device is constructed, with an IrMn3 pillar placed on one cross. The differential voltage is measured between the two crosses with and without IrMn3 after each switching attempt. For a wide range of current densities, reversible switching is observed only when write currents pass through the cross with the IrMn3 pillar, eliminating any possibility of non-magnetic switching artifacts. Micromagnetic simulations support our findings, indicating a complex domain-mediated switching process.

scholarly journals General considerations on the theory of the separation of H 1 and H 2 by electrolysis of water

1934 ◽  
Vol 144 (852) ◽  
pp. 452-466 ◽  
Keyword(s):  
A Priori ◽  
Point Of View ◽  
Theoretical Point ◽  
High Current ◽  
Hydrogen Electrode ◽  
Effective Separation ◽  
A Value ◽  
Rates Of Evolution ◽  
Wide Range ◽  
Current Densities

1. The Facts .―In a solution of NaOH (or KOH) with nickel (perhaps with other) electrodes and at high current densities of the order of 1 ampere per cm. 2 of electrode the observed rates of evolution E 1 and E 2 of H 1 and H 2 at the cathode obey an equation of the type E 1 /E 2 = q D 1 /D 2 , (1) where D 1 and D 2 are the relative concentraction of the H 1 and H 2 atoms in the water as a whole. The coefficient q has been shown to be independent of D 1 /D 2 over a very wide range of relative concentrations. Under the conditions most favourable to separation, which appear to be those just specified, q can have a value as great as 6, or perhaps 7. With other metals than nickel for the electrodes and with lower current densities the factor q may fall to a value well below 2 or even to a value so nearly unity that no effective separation occurs. The dependence of q (if any) on the temperature of the solution is not known. 1.1. The Arguments .―The facts have already been commented on by Polanyi from the theoretical point of view. He has been led to conclude from them that the separation is to be attributed to a difference of " over potential" for the deposition of H 1 and H 2 ions on the cathode, and consequently that Gurney's theory of the over-potential of the hydrogen-electrode at low current densities (as measured, for example, by Bowden) must be discarded. These conclusions if correct and unavoidable are of the greatest importance. It is most general way possible, in order to see that no types of mechanism have been overlooked which could lead to the observed results. When this is done it is found that the mechanism discussed by Polanyi which refers the separation to differences of over-potential is not the only mechanism which must be held possible a priori . The observed separation could perfectly well occur by a mechanism consistent with Gurney's theory. It does not yet appear to be possible to decide confidently between the two possibilities on experimental grounds.

scholarly journals Effect of electrolysis parameters on the morphologies of copper powder obtained at high current densities

2012 ◽  
Vol 77 (5) ◽  
pp. 651-665 ◽  
Author(s):  
Gökhan Orhan ◽  
Güzey Gezgin
Keyword(s):  
Hydrogen Evolution ◽  
Apparent Density ◽  
Copper Ion ◽  
Ion Concentration ◽  
High Rate ◽  
High Current ◽  
Electrolyte Temperature ◽  
Ion Concentrations ◽  
Copper Powders ◽  
Current Densities

The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders at high current densities under galvanostatic regime were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was used for analyzing the morphology of the copper powders. It was found that the morphology was dependent over the copper ion concentration and electrolyte temperature under same current density (CD) conditions. At 150 mA cm-2 and the potential of 1000?20 mV (vs. SCE), porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4). Under this condition, high rate of hydrogen evolution reaction took place parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk-stock like morphology with the increasing of Cu ion concentrations towards 0.120 M, 0.155 M, 0.315 M, 0.475 M and 0.630 M Cu2+ in 0.5 M H2SO4 respectively at the same CD. Similarly, as the temperature was increased, powder morphology and apparent density were observed to be changed. The apparent density values of copper powders were found to be suitable for many of the powder metallurgy applications.

scholarly journals B‐Cu‐Zn gas diffusion electrodes for CO2 electroreduction to C2+ products at high current densities

2021 ◽  
Author(s):  
Yanfang Song ◽  
Joao R. C. Junqueira ◽  
Nivedita Sikdar ◽  
Denis Öhl ◽  
Stefan Dieckhöfer ◽  
...  
Keyword(s):  
Gas Diffusion ◽  
High Current ◽  
Gas Diffusion Electrodes ◽  
Co2 Electroreduction ◽  
Current Densities

scholarly journals Controlling the Reduction of Chelated Uranyl to Stable Tetravalent Uranium Coordination Complexes in Aqueous Solution

2020 ◽  
Author(s):  
Korey P. Carter ◽  
Kurt F. Smith ◽  
Toni Tratnjek ◽  
Gauthier J.-P. Deblonde ◽  
Liane M. Moreau ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Coordination Complexes ◽  
Tetravalent Uranium

scholarly journals B‐Cu‐Zn gas diffusion electrodes for CO2 electroreduction to C2+ products at high current densities

2021 ◽  
Author(s):  
Yanfang Song ◽  
Joao R. C. Junqueira ◽  
Nivedita Sikdar ◽  
Denis Öhl ◽  
Stefan Dieckhöfer ◽  
...  
Keyword(s):  
Gas Diffusion ◽  
High Current ◽  
Gas Diffusion Electrodes ◽  
Co2 Electroreduction ◽  
Current Densities
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