رسائل ماجيستير
Arabic
2005
SIMULATION OF ELECTROCHEMICAL REACTIONS IN ELECTROPLATING CELLS
تحسين الحطاب, حيدر حسين, كاظم خيون كحلول
كلية الهندسة-جامعة بابل · العراق
The increasing interest in the electrochemical phenomenon becomes clearer due to its major contribution to the overall industrial economy. Examples are found in batteries, fuel cells, or capacitors; for electric vehicles, portable devices, or industrial chemical productions; in the production of chlorine, caustic soda, aluminum; in electroplating, electromachining, electrorefining; and in corrosion.
The simulation method of electrochemical cells through electrochemical plating is recently considered one of the most modern approaches. In this study, the kinetics of the chemical and electrochemical reactions are examined by modeling and understanding the essential and secondary (conjugate) chemical and electrochemical reactions during the plating process. In addition, the effects of various conditions on the speed and kinetics of these reactions are also considered.
In order to apply this method, the mean-field kinetic equations and Poisson equation for a charged lattice model are adopted using two types of one-dimensional cells for the theoretical part of this study, namely (half-cell and full-cell) of size (100), with and without an applied potential of (e/2kT), provided that the cell contains two identical electrodes of thickness (10).
A computer program in Visual Basic is specially constructed to display the results of this study as required. Through this program, the concentrations are determined, including (metallic atoms, cations, anions, solvents, vacancies, and electrons), as well as the charge distribution and electric potential across the sites.
Two methods are used to determine the diffusion current, on which the mean-field kinetic equations mainly depend. They are:
Replacement of ions instead of the solvent.
Gradient of the chemical potential.
In both methods, during the three periods (t = 1, 3, 5 × 10⁵), the results showed that under potential application across the cell, the deposition continues for a long time and then is suppressed when the anode reaches its failure limit. It is observed that the deposition increases with the extension of space charges at the cathode. On the other hand, the ionic evolution (cations) takes a peak shape at the cathode, with a certain gradient between the anode and cathode. A reversed situation occurs for the anions evolution. At the same time, the electric potential distribution across the sites becomes higher, resulting in increased deposition.
Without potential application across the cell, the deposition starts and then stops at time (t = 6 × 10⁵) due to the suppression of electrochemical reactions at this time.
Comparing the two methods mentioned above at time (t = 5 × 10⁵), it is found that the deposition in the first method, by diffusion current, is larger in quantity (for the metallic atoms concentration in the half-cell) than in the second method. The reverse occurs for the full-cell.
It is also found in this study that the deposition at (t = 0.5 × 10⁵) is directly proportional to each of the ionic concentrations (cations and anions) in the electrolyte, the potential difference, and Fermi energy, and inversely proportional to the electrodes’ spacing.
