A novel method for the measurement of mixing time: A new application of electrochemical limiting diffusion current technique

2018 ◽  
Vol 99 ◽  
pp. 242-250 ◽  
Author(s):  
Özkan Aydin ◽  
Sinan Yapici
Keyword(s):  
Mixing Time ◽  
Diffusion Current ◽  
Current Technique ◽  
Novel Method ◽  
Limiting Diffusion Current

scholarly journals Estimation of the exchange current density and comparative analysis of morphology of electrochemically produced lead and zinc deposits

2017 ◽  
Vol 82 (5) ◽  
pp. 539-550
Author(s):  
Nebojsa Nikolic ◽  
Predrag Zivkovic ◽  
Goran Brankovic ◽  
Miomir Pavlovic
Keyword(s):  
Current Density ◽  
Exchange Current ◽  
Exchange Current Density ◽  
Diffusion Current ◽  
Electron Microscopic ◽  
Zinc Electrodeposition ◽  
Lead And Zinc ◽  
Current Densities ◽  
Limiting Diffusion Current ◽  
Zinc Deposits

The processes of lead and zinc electrodeposition from the very dilute electrolytes were compared by the analysis of polarization characteristics and by the scanning electron microscopic (SEM) analysis of the morphology of the deposits obtained in the galvanostatic regime of electrolysis. The exchange current densities for lead and zinc were estimated by comparison of experimentally obtained polarization curves with the simulated ones obtained for the different the exchange current density to the limiting diffusion current density ratios. Using this way for the estimation of the exchange current density, it is shown that the exchange current density for Pb was more than 1300 times higher than the one for Zn. In this way, it is confirmed that the Pb electrodeposition processes are considerably faster than the Zn electrodeposition processes. The difference in the rate of electrochemical processes was confirmed by a comparison of morphologies of lead and zinc deposits obtained at current densities which corresponded to 0.25 and 0.50 values of the limiting diffusion current densities.

scholarly journals The ionic equilibrium in the CuSO4-H2SO4-H2O system and the formation of the honeycomb-like structure during copper electrodeposition

2008 ◽  
Vol 73 (7) ◽  
pp. 753-760 ◽  
Author(s):  
Nebojsa Nikolic ◽  
Ljubica Pavlovic ◽  
Goran Brankovic ◽  
Miomir Pavlovic ◽  
Konstantin Popov
Keyword(s):  
Hydrogen Evolution ◽  
Current Density ◽  
Diffusion Current ◽  
Copper Electrodeposition ◽  
Hydrodynamic Conditions ◽  
Ionic Equilibrium ◽  
Electrode Layer ◽  
Limiting Diffusion Current

The ionic equilibrium of the species in the CuSO4-H2SO4-H2O system was employed to systematize the conditions of copper electrodeposition leading to the formation of the honeycomb-like structure. The reason why CuSO4 concentrations higher than 0.15 M are unsuitable for the formation of honeycomb-like structures is shown. The range of H2SO4 concentrations enabling the formation of this type of structure was also determined. The conditions leading to the formation of the honeycomb-like structures are: electrodeposition from solutions with lower concentrations of Cu(II) ions (0.15 M CuSO4 and less) in a concentration range from 0.25 to 1.0 M H2SO4, at a temperature of 18.0?1.0 ?C and at overpotentials outside the plateau of the limiting diffusion current density at which hydrogen evolution is vigorous enough to change the hydrodynamic conditions in the near-electrode layer. .

Diffusionsgrenzstrom und verwandte Probleme bei Elektrolytschmelzen mit drei ionischen Bestandteilen / Limiting Diffusion Current and Related Problems of Ionic Melts with Three Ion Constituents

1974 ◽  
Vol 29 (12) ◽  
pp. 1935-1936 ◽  
Author(s):  
R. Haase
Keyword(s):  
Interdiffusion Coefficient ◽  
Diffusion Current ◽  
Simultaneous Occurrence ◽  
Ionic Melts ◽  
Electrode Interface ◽  
Electric Flux ◽  
And Diffusion ◽  
Internal Transport ◽  
Limiting Value ◽  
Limiting Diffusion Current

Starting from the general equation for the simultaneous occurrence of electromigration and diffusion in an ionic melt with three ion constituents, we derive the rigorous expression for the electric flux at an electrode interface. This expression contains the ratio of the interdiffusion coefficient of the melt to the internal transport number of the ion constituent that does not cross the interface. In the case of the limiting diffusion current (occurring in the problem of diffusion overvoltage), the electric flux contains the limiting value for infinite dilution of the interdiffusion coefficient.

CFD Simulation of Mixing Effects in Gas-Liquid-Solid Stirred Reactor

2011 ◽  
Vol 383-390 ◽  
pp. 5778-5784
Author(s):  
Jian Xin Xu ◽  
Hua Wang ◽  
Jian Jun Wang ◽  
Shi Bo Wang ◽  
Dao Fei Zhu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Cfd Simulation ◽  
Mixing Time ◽  
Betti Numbers ◽  
Phase Mixing ◽  
Computational Homology ◽  
Stirred Reactor ◽  
Three Phase ◽  
Fluent Software ◽  
Novel Method

In order to analyze the complex phase transition in the gas-liquid-solid three-phase mixing systems and to predict gas-liquid-solid multiphase mixing time, a novel method combined image processing technology, computational homology and CFD (Computational Fluid Dynamics) numerical simulation is introduced in this study. Firstly, the volume of fluid (VOF) multiphase flow model in FLUENT software is used for the simulation of fluid characteristics. Secondly the patterns produced by phase transition in the stirred tank are binaryzed. Finally evolution profile of the zeroth dimensional Betti numbers and the first dimensional Betti numbers in time series are obtained separately. In fact,some aggregates still remain in the tank after the homogeneous mixing.Comparing with the fractal method to characterize the mixing time, the result shows that this method not only can predict the gas-liquid-solid mixing time by the zeroth dimenstional Betti numbers, but also can predict the amount of these aggregates in the stired tank by the first dimenstional Betti numbers, leading to a useful parameter to characterize the non-uniformity of gas-liquid-solid mixing.

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