Papers by Keyword: Electrochemistry

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Authors: Yan Sheng Zhang, Jia Ming Zhang, Bo Zhang, Ke Xin Chang, Jun Wang, Jian Ping Xie, Wen Qing Qin, Guan Zhou Qiu
Abstract: Chemical element analysis and X-ray diffraction (XRD) analysis showed that the two chalcopyrite minerals were of high purity. A mixed culture of moderately thermophiles was used for chalcopyrite bioleaching at 45°C and the copper recovery of chalcopyrite (a) and chalcopyrite (b) was 66.1% and 21.4%, respectively, after 19 days of leaching. Bioleaching behavior of the two different chalcopyrite samples was studied through comparing the lattice parameter and grain size of chalcopyrite. It was shown that lattice parameter and grain size are not the key factors affecting the leaching of chalcopyrite. The corrosion current density of chalcopyrite (a) calculated through Tafel curves was 1.149 μA/cm2, while that of chalcopyrite (b) was only 0.5696 μA/cm2. The higher corrosion current density suggested that chalcopyrite (a) can be more easily dissolved than chalcopyrite (b).
Authors: Srdjan Nešić, Magnus Nordsveen, Rolf Nyborg, Aage Stangeland
Authors: Su Xing Luo, Yuan Hui Wu, Hua Gou, Yan Liu
Abstract: In this work, a simple and sensitive electrochemical method sensor was developed to determine salbutamol based on magnetic NiFe2O4 nanoparticles modified glassy carbon electrode. It was found the anodic peak current of salbutamol was linear with the concentration of salbutamol from 2.0 μM to 60 μM with a detection limit of 1.0 μM (S/N=3). The developed method was successfully applied to determine salbutamol content in pork samples with satisfactory results.
Authors: Laïd Laoufi, Yassine Senhadji, A.S. Benosman
Abstract: Reinforcement corrosion is one of the main causes of concrete deterioration. The steel in concrete is naturally protected from corrosion by the presence of a passive film formed through the high alkalinity of concrete. A technique to improve the protection of steel in concrete is the inclusion of mineral additions. Natural pozzolan (NP) from Beni-Saf is a mineral addition that is abundant in western Algeria. The experiment was conducted on mortar specimens, containing steel bars and exposed to the aggressive solutions of Na2SO4 and MgSO4. The status of reinforcement is periodically monitored by measuring the electrochemical potentials and the corrosion rates by the technique of linear polarization resistance (LPR) and also the thermal conductivity was evaluated. The test results show that natural pozzolan significantly affects the physical properties of mortars, improves the corrosion resistance of mortars containing up to 20% of natural pozzolan and reduces the thermal conductivity.
Authors: G.Y. Liu, Z.N. Guo, Jiang Wen Liu
Abstract: This paper presents a electrochemical-mechanical combined polishing progress of Cr12 hardening steel with a new kind of embedded tool. The embedded tool has been composed of two parts, the metal base acting as electrode and the inlayer with electroplating diamond grains on its outside surface which serves as mechanical grinding abrasive. The two parts are agglutinated by adhesive which can keep a good insulation of the inlayer during the mechanical process. The inter-electrode gap can be changed by altering the metal base and inlayer’s diameter. Through the investigation of numerical simulation and polishing experiment, it can be found that lower feed, reciprocate speed, longer trip of reciprocating, smaller diamond grains make better surface quality.
Authors: Wei Hua Sun, Hong Chun Li, Ahn Kiet Tieu
Abstract: The MMS-2B wear machine was used to study abrasion wear of work rolls in cold rolling by simulating emulsion cooling during the cold rolling process. The work roll materials used were 4%Cr, same as those in industrial production. The surface SEM scanning photographs were taken every 30 minutes until the friction experiment finished, and erosive appearance of emulsion on the work roll surface could be seen in the photos. The corrosive wear of the work roll surface is discussed. Findings show that the main causes of stress corrosion and pitting corrosion are uneven microstructure on the work roll surface and a large number of dislocation accumulations, which form microscopic cells. Water in steel rolling emulsion is the main conductive medium of electrochemistry reaction, and this intensifies the corrosive wear.
Authors: Zhi Feng Zeng, Hai Yan Zhang, Xi Duo Hu
Abstract: The LiFePO4/MWCNTs composite used as cathode was synthesized by ball milling. XRD and SEM experiments demonstrated that MWCNTs didn’t change the olivine structure of LiFePO4 and that MWCNTs decentralized into the grains of LiFePO4 and working as electric bridge improving the electrochemical properties of LiFePO4. The electrochemical performance of the composite electrodes with different MWNTs in diameter were studied by button cell. The result indicated that the composite with largest diameter MWNTs exhibited best electrochemical performance. The first charge-discharge specific capacity of the composite with MWNTs of 60-100nm in diameter were 136mAh/g-1 and 129 mAh/g-1 respectively at 0.1C rate under room temperature. The difference between charge-discharge platforms of the composite electrode was the least compared to the others. This phenomenon showed that the material had the largest chemical diffusion coefficient of lithium. At the same time, the capacity of the composite only lost 4.0% after 10 cycles and kept constant after 20 cycles.
Authors: Michaela Remešová, Lenka Klakurková, Ladislav Čelko, Lucia Sládková, David Jech, Jozef Kaiser
Abstract: Electrochemical process of conversion coatings formation on Zn-Ti alloy surface during one-step anodizing process was studied in NaOH and KOH electrolytes over the range of voltages (4-50 V) and constant time in order to investigate parameters for the origin of anodic zinc coating. Stainless steel was used as a counter electrode and electrolyte during the anodizing process was agitated by compressed air. Coatings microstructures and morphology were characterized by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Surface topography was investigated prior and after the anodizing using non-contact optical 3D profilometer. It was found that high voltage (50 V) and low concentrations of electrolyte (0.04 and 0.1 mol/L NaOH) led to origin of white coloured oxide coatings, while lower voltage (4 and 6 V) and higher concentrations of electrolyte promote the origin of black coloured oxide coatings. Concentration of electrolyte and voltage influenced the thickness of conversion coatings and its surface morphology. Moreover, the surface morphology of the coatings was also influenced by the heterogeneity of substrate alloy.
Authors: Oksana V. Dubinina, Galina V. Lyamina, Gennady M. Mokrousov
Abstract: Application of polymer gels for cleaning and restoration of the surface of different steel grades has been showed. Two techniques of the surface cleaning have been tested: a contact of the polymer film with an object surface; the electrochemical cleaning of metals where the polymer gel was used as a background electrolyte. It has been established that the first technique is more effective for low carbon steels and the second technique is more effective for high-alloy steels. The advantages of the application of the technique with polymer gels are localization and control of the process.
Authors: Azzura Ismail, M. Aminuddin M. Tajuddin
Abstract: Corrosion is commonly known as rust, an undesirable phenomena which destroys the luster and beauty of objects and cause shorter of life span. The objective for this research is to study the effect of using green inhibitor with seawater (NaCl) to the corrosion resistance of stainless steel 304. The green inhibitor was extracted from banana peel added with seawater (3.5% NaCl). The concentration of green inhibitor added was 5%, 10%, 15%, 20% and 25%. The test was conducted using the 3-electrode potentiostat to understand the behaviour of corrosion attack on stainless steel 304 at room temperature under static conditions. The results elucidate that green inhibitor has significant effect to the breakdown of passive film of stainless steel 304 in seawater. The forms of corrosion attack were viewed by using optical microscope. In conclusion, banana peel can be use as green inhibitor to increase corrosion resistance of stainless steel 304 and at the same time the abundant waste from local small industries can be recycled.
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