The effect of L (-) cysteine and thiourea on the kinetics of copper electrocrystallization from aqueous sulphate solutions

The production and characterization of nano-crystalline metallic coatings has been a subject of intensive research due to their fundamental and commercial significance. For instance, thin films of copper are used in electronic industry for the fabrication of interconnect for printed circuit boards, integrated chips and multilayer sandwiches. Organic substances such as thiourea (TU), gelatine, polyethylene glycol, and benzotriazole are usually added to electrodeposition bath in low concentrations for beneficial effects such as brightening and levelling of the deposit. Despite the perceived benefits of additives, there is limited fundamental understanding of their mode of action and impact on electrocrystallization kinetics. In this study, the effect of thiourea and L (-) Cysteine (CYS) on mechanisms and kinetics of copper electrodeposition from an aqueous solution at pH 1 and 25 degreesC was studied using Linear Scan Voltammetry (LSV) and Atomic Force Microscopy (AFM). The current density measurements, estimated kinetic parameters and ex situ AFM visual observation indicated that both TU and CYS have a significant inhibition and morphological effects on the electroreduction of Cu(II), resulting in fine-grained deposits. These additives were found to influence the electron and mass transfer at electrode/electrolyte interface and lead to the formation of a crystalline deposit whose structure and morphological analysis indicate S-based impurity incorporation effects

The electrocrystallization mechanisms and kinetics of copper onto glassy carbon

The nucleation and growth process of crystalline phases by electrocrystallization is of significant interests due to its application in producing thin films of metals and oxides for the fabrication of alloys, integrated circuits and magnetic recording devices with high degree of selectivity and precision. The attractiveness of electrocrystallization emerges from the fact that uniform, thin or multilayer films of various physicochemical properties may be achieved by tuning primary variables such as current density (applied potential), bath composition and temperature. To date, there is a dearth of understanding of the fundamental electrocrystallization mechanisms and kinetics and their links with the structure and properties of thin films (e.g., grain size, morphology, resistivity, hardness and corrosion). The main objective of the present work is to investigate the effect of electrolyte concentration on the mechanisms and kinetics of electrocrystallization and morphology of copper onto glassy carbon electrode. Cyclic voltametric and chronoamperometric results indicated that at lower electrolyte concentrations (5 10-4 - 10-3 M), a 2D, lattice incorporation-limited growth mechanism prevails, resulting in monolayer coverage deposition. At higher electrolyte concentrations (10-2 -10-1 M), a 3D growth mechanism under both charge transfer and volume diffusion limitations was observed. An Atomic Force Microscopy study of the deposit revealed a laterally spread small nuclei at lower concentrations and an island growth at higher concentrations, in agreement with the electrochemical findings

Influence of particle shape and roughness on the induction period for particle-bubble attachment

Within the flotation community a belief has developed that some particle shapes are more 'floatable' than others. This is usually attributed to an influence of particle shape or roughness on the induction period required to achieve attachment between the particles and the air bubbles in the pulp. Up to now, such measurements have not been able to readily isolate the effect on individual flotation subprocesses. In contrast, our experimental apparatus, the CSIRO Milli-Timer, enables us to directly observe the process of particle-bubble interaction and attachment by means of a high-speed video recording, thus providing a direct measure of the induction period for attachment. To assess the influence of particle shape on induction time we used two varieties of methylated borosilicate glass particles - spheres and angular 'frit' - in a range of tightly-sized fractions. In doing this, we take care to account for the influence of other factors that could affect the induction time, such as the polar angle of sliding commencement, and approach velocity. These parameters are recorded as variables for each interaction, and corrected for using multiple nonlinear regression. Our results illustrate the importance of particle shape on induction period, with angular particles exhibiting induction periods that were an order of magnitude lower than those of spheres. Furthermore, the induction period was seen to decrease with increasing particle velocity, or kinetic energy on approach, but increased as the trajectory approached the limit of just grazing the bubble. Particle shape in mineral processing is a consequence chiefly of the mineral type and the type of grinding employed. The results presented herein indicate that attention should be paid to the shape of particles obtained from the grinding operation, besides particle size.12 page(s