Cathode Polarization as a Function of the Current Density in Fused Salts

1936 ◽  
Vol 40 (6) ◽  
pp. 763-768
Author(s):  
S. Karpatschoff ◽  
O. Poltoratska
Keyword(s):  
Current Density ◽  
Cathode Polarization ◽  
Fused Salts

CATHODE SURFACE CHANGES IN THE PRESENCE OF GELATIN DURING ELECTRODEPOSITION OF COPPER

1943 ◽  
Vol 21b (6) ◽  
pp. 125-132 ◽  
Author(s):  
W. Gauvin ◽  
C. A. Winkler
Keyword(s):  
Grain Size ◽  
Current Density ◽  
Copper Sulphate ◽  
Cathode Surface ◽  
Active Area ◽  
Cathode Polarization ◽  
Active Centres ◽  
Main Factor ◽  
Surface Changes

Measurements of the cathode polarization during electrodeposition of copper from acid copper sulphate solutions indicate that introduction of gelatin into the electrolyte decreases the area of the cathode available for deposition, or active area, owing to adsorption of gelatin on the active centres. This decrease in area causes an increase in the true current density, with a resulting increase in cathode polarization, the former being assumed the main factor in causing an increase in the rate of nuclear formation and decrease in grain size.

EFFECT OF GELATIN ON THE CHANGES IN INITIAL CATHODE POLARIZATION DURING ELECTRODEPOSITION OF COPPER

1954 ◽  
Vol 32 (6) ◽  
pp. 581-590 ◽  
Author(s):  
B. I. Parsons ◽  
C. A. Winkler
Keyword(s):  
Steady State ◽  
Current Density ◽  
Copper Sulphate ◽  
Chloride Concentration ◽  
High Current ◽  
Concentration Increase ◽  
Addition Agent ◽  
Cathode Polarization ◽  
Current Densities ◽  
Gelatin Concentration

In the absence of addition agent, the cathode polarization during initial electrolysis of copper from a solution of acid copper sulphate rose almost instantaneously from zero to approximately the steady state polarization. When gelatin was present in the electrolyte, the polarization generally increased to a maximum, Pmax, (in time tmax) then decreased to a minimum, Pmin, (in-time tmin) beyond which it increased to the steady state value, Ps. Generally, Pmax increased to a steady value with an increase in the time, T0, the electrode was in contact with the electrolyte before electrolysis was begun. At low, moderate, and high current densities respectively, tmax increased continuously, passed through a maximum, and decreased continuously with T0.The behavior of tmin approximately paralleled that of tmax. The polarization was linear in the logarithm of the current density; tmax and tmin decreased with increase in current density. The polarization values increased and tmax decreased, with increase in gelatin concentration. Increase of temperature had approximately the same effect as decrease in current density. With both chloride and gelatin present, Pmax was practically independent of T0 and chloride concentration, while Pmin and Ps showed minimum values at about 2 mgm./l. chloride.

EFFECT OF SURFACE ON CATHODE POLARIZATION DURING THE ELECTRODEPOSITION OF COPPER

1943 ◽  
Vol 21a (4) ◽  
pp. 37-50 ◽  
Author(s):  
W. Gauvin ◽  
C. A. Winkler
Keyword(s):  
Steady State ◽  
Current Density ◽  
Crystal Size ◽  
Cathode Surface ◽  
Surface Condition ◽  
Metal Structure ◽  
Polarization Current ◽  
Cathode Polarization ◽  
Current Densities ◽  
Effect Of Surface

Measurements in a modified Haring cell have shown that at current densities above approximately 0.6 amp. per dm.2, definite values of the cathode polarization are attained during the electrodeposition of copper from acid copper sulphate solutions, providing sufficient time is allowed for the cathode surface to attain a steady state corresponding to the conditions of electrolysis. At lower current densities, the base metal structure is perpetuated in the deposit, and the cathode polarization will depend upon the surface condition of the electrode initially. The results account for the lack of agreement in polarization values obtained by different workers using the Haring cell, and indicate that crystal size is fundamentally related to true current density, rather than to cathode polarization. A method is outlined for obtaining reproducible cathode-polarization–current-density curves, substantially corresponding to steady state values.

The Effect of Nickel in Zinc Electrowinning

2011 ◽  
Vol 396-398 ◽  
pp. 106-109
Author(s):  
Gang Xie ◽  
Zhi Dong Liu ◽  
Xiao Hua Yu ◽  
Ying Lu
Keyword(s):  
Current Density ◽  
Limiting Current ◽  
Zinc Electrowinning ◽  
Kinetics Equation ◽  
Polarization Process ◽  
Polarization Function ◽  
Cathode Polarization ◽  
Nickel Ions ◽  
Process Kinetics

The effects of nickel ions on the cathode polarization process, kinetics equation and parameters in zinc electrowinning have been investigated in this paper. The results of the experiments show that when [Ni2+] ≤ 4 mg•L-1, the current density increases with increasing concentration of Ni2+ and limiting current of the passive point reach maximum, which indicates that the depolarization function of nickel in zinc electrowinning. And when [Ni2+] ≥ 4 mg•L-1, owing to the polarization function of nickel, electrowinning enters into stationary passive range at first and then enters into precipitation range because of the polarization function of nickel.

DEPOLARIZATION BY MERCAPTOACETIC ACID DURING ELECTRODEPOSITION OF COPPER

1956 ◽  
Vol 34 (2) ◽  
pp. 128-132 ◽  
Author(s):  
A. J. Sukava ◽  
C. A. Winkler
Keyword(s):  
Surface Area ◽  
Current Density ◽  
Copper Complex ◽  
Copper Sulphate ◽  
Mercaptoacetic Acid ◽  
Surface Roughening ◽  
Cathode Polarization ◽  
Sulphate Electrolyte ◽  
Consequent Increase

Mercaptoacetic acid (MAA) in acid copper sulphate electrolyte decreased the cathode polarization throughout the course of electrolysis at all concentrations up to 20 mgm./liter. Addition of small amounts of chloride caused further depolarization. When present together with cystine, MAA showed an independence of action. The depolarization caused by MAA was ascribed to a decreased activation overpotential due to substitution of a more readily dischargeable MAA–copper complex for the aquo–copper complex. The additional depolarization due to chloride was ascribed to formation of a still more readily dischargeable chloro–MAA–copper complex. The depolarization in both cases increased with time during prolonged electrolysis, apparently due to surface roughening with, presumably, a consequent increase in surface area and decrease in true current density.

Electrocatalytic Properties of Nickel Foam-Based Ni-Mo, Ni +Mo and Ni+Mo/Ni-Mo Electrodes for Hydrogen Evolution Reaction

2018 ◽  
Vol 921 ◽  
pp. 134-140 ◽  
Author(s):  
Jing Guo Zhang ◽  
Shao Ming Zhang ◽  
Shuo Li ◽  
He Dai ◽  
Qiang Hu ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Current Density ◽  
Electrochemical Impedance ◽  
Nickel Foam ◽  
Real Surface ◽  
Composite Electrodes ◽  
Composite Alloy ◽  
Cathode Polarization ◽  
Real Surface Area

Nickel foam-based Ni-Mo alloy electrodes, Ni+Mo composite electrodes and Ni+Mo/Ni-Mo composite alloy electrodes were prepared by eletrodeposition, and the electrocatalytic characteristics for hydrogen evolution reaction (HER) in 30wt% KOH solution were investigated by cathode polarization curve and electrochemical impedance spectroscopy (EIS). The experimental results show that in comparison with nickel foam electrodes, these electrodes exhibit a lower overpotential, a higher exchange current density and a larger real surface area for HER. At 30°C and current density of 200 mA/cm2, the overpotentials of foam Ni electrodes, nickel foam-based Ni-Mo alloy electrodes, Ni+Mo composite electrodes, Ni+Mo/Ni-Mo electrodes are respectively 506, 252, 336, 202 mV. The nickel foam-based Ni+Mo/Ni-Mo composite alloy electrode had the highest HER electrocatalytic activity.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

Microstructural characterization of YBa2Cu3O7-x thin films formed by metalorganic CVD

1991 ◽  
Vol 49 ◽  
pp. 1080-1081
Author(s):  
P. Lu ◽  
W. Huang ◽  
C.S. Chern ◽  
Y.Q. Li ◽  
J. Zhao ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Film Growth ◽  
Chemical Vapor ◽  
Microstructural Characterization ◽  
Ion Milling ◽  
Conventional Grinding

The YBa2Cu3O7-x thin films formed by metalorganic chemical vapor deposition(MOCVD) have been reported to have excellent superconducting properties including a sharp zero resistance transition temperature (Tc) of 89 K and a high critical current density of 2.3x106 A/cm2 or higher. The origin of the high critical current in the thin film compared to bulk materials is attributed to its structural properties such as orientation, grain boundaries and defects on the scale of the coherent length. In this report, we present microstructural aspects of the thin films deposited on the (100) LaAlO3 substrate, which process the highest critical current density.Details of the thin film growth process have been reported elsewhere. The thin films were examined in both planar and cross-section view by electron microscopy. TEM sample preparation was carried out using conventional grinding, dimpling and ion milling techniques. Special care was taken to avoid exposure of the thin films to water during the preparation processes.

Analytical electron microscopy of grain boundaries in Al-Cu metallizations

1992 ◽  
Vol 50 (2) ◽  
pp. 1684-1685
Author(s):  
J. R. Michael ◽  
A. D. Romig ◽  
D. R. Frear
Keyword(s):  
Electron Microscopy ◽  
Integrated Circuits ◽  
Failure Mode ◽  
Current Density ◽  
Thermal History ◽  
Analytical Electron Microscopy ◽  
Cu Metallization ◽  
Analytical Electron ◽  
Interconnect Lines

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits, the Cu being added since it improves resistance to electromigration failure. As linewidths decrease to submicrometer dimensions, the current density carried by the interconnect increases dramatically and the probability of electromigration failure increases. To increase the robustness of the interconnect lines to this failure mode, an understanding of the mechanism by which Cu improves resistance to electromigration is needed. A number of theories have been proposed to account for role of Cu on electromigration behavior and many of the theories are dependent of the elemental Cu distribution in the interconnect line. However, there is an incomplete understanding of the distribution of Cu within the Al interconnect as a function of thermal history. In order to understand the role of Cu in reducing electromigration failures better, it is important to characterize the Cu distribution within the microstructure of the Al-Cu metallization.

Microstructure Development in a High Current Density NbTi Superconducting Composite

1985 ◽  
Vol 43 ◽  
pp. 186-189
Author(s):  
P. J. Lee ◽  
D. C. Larbalestier
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Cold Drawing ◽  
Heat Treatments ◽  
Grain Structure ◽  
Fine Grain ◽  
Boundary Film ◽  
Quantitative Basis ◽  
Cold Worked ◽  
Very High

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

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