The role of functional groups of saccharin in electrodeposition of nanocrystalline nickel

Abstract

Nanostructural materials exhibit different mechanical, physical, chemical, and electrochemical properties relative to conventional structures. For instance, nanostructural nickel shows enhanced properties compared to those of polycrystalline nickel, such as higher microhardness, increased wear resistance, higher brightness and lower roughness. In order to produce nanostructural materials, some additives are used as grain refiners. Saccharin is one of the additives that is usually added to the Watts bath in the electroplating process as a grain refiner. The aim of this study is to clarify the functional mechanism of saccharin as a grain refiner in order to realize which functional group of this molecule works as a grain refiner and causes enhancement of properties. To investigate the impact of a functional group of saccharin in the production of nanocrystalline nickel deposits, three different materials with the same functional groups as saccharin were chosen: benzene sulfonic acid, methyl sulfonamide, and benzothiazole. In the process of nickel electroplating these materials were added to the Watts bath as additives. The X-ray diffraction patterns were used to determine the average grain size of the nanocrystalline nickel coatings. The results indicate that the presence of a benzene ring in saccharin, benzene sulfonic acid and benzothiazole cause these molecules to move from the electrolyte to the electrode surface and, by blocking the electrode surface, enhance the grain size and produce nickel coatings with an average grain size below 50 nm. The results also showed that the presence of materials containing a benzene ring with a weak ionic group enhances adsorption on the electrode surface.