Electrodeposition of silver from thiosulfate solutions.

摘要

The goal of this work is to further the electrochemical and morphological understanding of silver electrodeposition from thiosulfate solutions. Although silver electrodeposition from photographic fixing baths containing thiosulfate has been done successfully for many years; the vast majority of information about this process remains empirical.; The electrochemical behavior of silver electrodeposition is studied from several perspectives. A comparison is made between plating silver from ammonium and sodium thiosulfate containing solutions. The diffusion coefficient for plating from ammonium thiosulfate solutions was determined to be higher than from sodium thiosulfate solutions. Two methods of surface analysis were done to study surface differences. The first used Atomic Force Microscopy (AFM) to image the surfaces. The second incorporated scaling analysis of the electrodeposited surfaces such as rms roughness, and growth and roughening exponents. From these results, silver electrodeposition from sodium thiosulfate containing solutions was found to be smoother than from ammonium thiosulfate containing solutions, caused by leveling behavior of the sodium system.; The morphology and roughness of the electrodeposit from additive containing systems was also studied. Thiourea, polyethylene glycol, benzotriazole and urea were added to ammonium thiosulfate plating solutions as plating additives. These were also analyzed by image and scaling analysis. Thiourea was found to have the greatest effect on decreasing surface roughness of the additives studied. Benzotriazole and urea were found to have minimal leveling effects, and polyethylene glycol did not perform as a leveling agent in this system.; This two-stage image and scaling analysis was also used to study the effect of fluid flow on electrodeposited silver surfaces. Increasing the fluid flow rate through a flow channel resulted in a smoothing effect, caused by a decreased effect of surface diffusion, and an increase in the Ming in of surface recesses and valleys as determined by scaling analysis, and confirmed by AFM imaging of the surfaces.; Strongly complexed, weakly complexed and uncomplexed silver were plated to determine the effects of complexation on surface roughness. Scaling analysis indicates that complexation of the silver causes a leveling effect of the surface deposit, and these results are confirmed by AFM image analysis. The results indicate that the more complexed the silver, the smoother electrodeposit.