Papers by Keyword: Electrochemical Process

Abstract: Comparative studies of the corrosion and electrochemical properties of amalgam filling materials based on copper, silver and non-gamma-2 "Oralloy" amalgam (Switzerland) were carried out in aqueous solutions of sodium chloride, sodium bicarbonate and citric acid at room temperatures and under conditions of mechanical depassivation of the surface. Although copper amalgam is corrosion-resistant in control environments due to the formation of protective passivating layers on the surface, the test results show that the advantage of silver amalgam in all tested solutions is obvious. It has been confirmed that the “Oralloy” filling material has advantages over copper and silver amalgams in the corrosion-electrochemical aspect. It is corrosion resistant in physiological neutral and slightly alkaline solutions, like silver amalgam, but surpasses it in electrochemical inertness. It has been shown that when predicting the intensity of galvanic processes that occur in the presence of two or more dissimilar metallic inclusions in the oral cavity, the potential difference between them is a necessary but insufficient criterion. When deciding the compatibility of new filling materials and previously used ones, it is necessary to take into account the pH of the environment, the potential difference between them, their nature and surface condition, as well as their position on the surface of the teeth. If there is a possibility of abrasion of the amalgam surface by antagonist teeth, then the likelihood of galvanosis increases significantly.

Abstract: Zinc oxide nanostructures were synthesized by an electrochemical dissolution and deposition process. The zinc plates were immerged in deionized water and used as two electrodes. The process was operated by applying the electric field of 10, 12.5, 25 and 50 V/cm, the constant voltage of 10 V and varied the temperatures from room temperature to 70 °C during 1 h. It was found that the electric field and temperature of electrolyte solution had affected to morphologies of ZnO NSs and were grown in forms of nanoflakes, nanoparticles and nanorods.

Abstract: The electrodeposition of zinc from acidic sulphate bath on steel substrate has been studied. The influence of sodium dodecylbenzenesulfonate (SDBS) as surfactant on the mechanism of the electrodeposition process has been investigated using potentiodynamic and cyclic voltammetry (CV) techniques. From the analysis of CV analysis, it is shown that in the surfactant free bath solution, hydrogen evolution occurs together with the zinc deposition. The presence of SDBS shifts the reduction potential of Zn²⁺ to more negative values, indicating that SDBS to some extent hinder the Zn electrodeposition.

Abstract: In this paper, CdSe-TiO₂ nanotube array composite films were successfully prepared through a two-steps method. TiO₂ nanotube arrays were firstly prepared by anodic oxidation method, based on which the composite films of CdSe-TiO₂ nanotubes arrays were prepared by electrochemical deposition. The influence of the concentration of SeO₂ on the structure and photoelectric performance of the composite films were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and photocurrent response tests. The results show that the cubic phase CdSe particles with the size of about 15~20 nm were uniformly distributed in highly ordered TiO₂ nanotubes and around the mouths of the nanotubes; With the increasing of concentration of SeO₂, the content of CdSe increases gradually while the photocurrent density of the composite films increased and decreased, The optimal photoelectric performance of composite films were obtained when the SeO₂ concentration was 4 mmol/L.

Abstract: The performance of nitrate reduction in an electrochemical system intensified by different metallic particles was evaluated in the present study. In the electrochemical process without metallic particles, the nitrate removal efficiency was found to be 65.7%, while higher nitrate conversion yields of 82.9%, 87.5% and 93.2% were obtained in the developed system in the presence of iron, steel and copper particles, respectively. Moreover, the presence of metallic particles in the electrochemical process significantly reduced 39.3-49.5% of the energy consumptions for nitrate reduction. Mechanisms of the acceleration of nitrate reduction by the three metallic particles were different. Iron and steel particles in the middle of the electric field dissolved and served as electron donors for nitrate reduction, while the copper particles worked as activated metallic catalysts. Taking into account of safety and operating cost, iron was the optimal choice among the three metallic particles studied.

Abstract: Carbon dioxide corrosion is a very complex electrochemical process. Compositions of formation water in different gas and oil wells are various, which effects on the carbon dioxide corrosion of tubular steel. HCO₃^- and SO₄^2- were studied in order to further understand their role on the corrosion process. The results show marked difference when they are the main composition while others conditions is the same. HCO₃^- mitigates the corrosion, because its participation in cathodic and anodic reactions accelerates passivation. However, corrosion in formation water mainly containing Na₂SO₄ is severe, which presents higher general corrosion rate and more dangerous localized corrosion.

Abstract: The investigated nanometric magnetite powders were synthesized electrochemically, and examined by XRD and SEM techniques. Their reduction was conducted through the isothermal heating in hydrogen in the temperature range from 600 to 860 K. Kinetics of the hydrogen recovery process during oxidation of freshly formed Fe powders in a water vapor stream was also studied. It was assumed that the solid-gas reaction is diffusion controlled, and Jander’s model was applied to describe it. The experimental data suggest that the reoxidation process proceeds in two stages, at various activation energies. By changing the conditions of the electrochemical (EC) process we were able to produce the iron oxide powders with optimal particle size and activity, for pure hydrogen production through appropriate reduction/oxidation processes.