Current-potential characteristics of electrochemical systems.

摘要

This dissertation contains investigations in three distinct areas. Chapters 1 and 2 provide an analysis of the effects of electromagnetic phenomena during the initial stages of cell discharge. Chapter 1 includes the solution to Maxwell's equations for the penetration of the axial component of an electric field into an infinitely long cylindrical conductor. This work investigates two time regimes: the "short time" and the "diffusive time". During the short time the current increases at a rate proportional to the time, and during the diffusive time it increases at a rate proportional to the square root of time. Also included in this chapter are mathematical expressions that describe the manner in which the electric field penetrates a conductive medium during the two time regimes. Chapter 2 contains the analysis of the conductor included in a radial circuit. The time constant for the discharge of the circuit is depicted as a function of the size of the system and the important physical parameters. Also included are analytic approximations of the time constant and a comparison to the lumped parameter approximation of inductance.;Chapter 3 provides a complete description of the equations that describe the growth of an oxide film. A finite difference program was written to solve the equations. The system investigated is the iron/iron oxide in a basic, aqueous solution. Figures are presented which provide a comparison of the simulations to the experimental data provided in the literature. Discussion of the quality of the fit is also provided. Ultimately, we found that at low voltages iron dissolves preferentially to form ferrous ions and at higher voltages reacts to form ferrous oxide.;Chapters 4 and 5 include the experimental attempts of replacing formaldehyde with an innocuous reducing agent for electroless deposition. In chapter 4, current-versus-voltage curves are provided for a sodium thiosulfate bath in the presence of a copper disk electrode. Also provided are the cathodic polarization curves of a copper/EDTA bath in the presence of a copper electrode. Explanations for the poor performance of thiosulfate as a reducing agent for copper are included. Chapter 5 contains the experimental results of work done with sodium hypophosphite as a reducing agent. Mixed-potential-versus-time curves for solutions containing various combinations of copper sulfate, nickel chloride, and hypophosphite in the presence of a palladium disk electrode provide an indication of the reducing power of the solutions. It appears that the hypophosphite is preferentially oxidized on nickel and its oxidation is inhibited on copper.