Papers by Keyword: Electrochemistry

Abstract: The casting Al-Si-Mg alloy can be strengthened by heat treatments. There are close relations between heat treatments and alloys mechanical properties and corrosion resistance. The effects of heat treatments condition on corrosion behavior of Al-Si-Mg alloy in NaCl solution were studied by electrochemistry tests and immersion corrosion tests in this paper. The morphology of alloys after immersion corrosion was observed by OM (optical microscopy) and SEM (scanning electron microscopy). The influences of heat treatments on the corrosion of casting Al-Si-Mg alloy were explained. Different microstructures could lead to variation of corrosion properties. The corrosion properties of Al-Si-Mg alloy after casting, ST (solution treatment) and different aging respectively were analyzed. The results show that corrosion properties under PA (peak aging) are the worst and the best ones with ST, at the same time the I_corr under PA are the highest case and the lowest ones with ST.

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.

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.

Abstract: The environmental concerns brought during pickling process of stainless steel in HNO₃-containing acids need urgent attention. Choosing the hydrochloric acid pickling process as study object, this paper conducted a systematic study of the effect of temperature on the electrochemical behavior of stainless steel in hydrochloric acid solution. Research indicated that as temperature rose, the corrosion potential of 430SS in hydrochloric acid solution moved to positive direction with band to a narrow 0.1V. Meanwhile, the current intensity increased which indicated the acceleration of corrosion rate. In addition, the anode Tafel slope increased firstly and decreased later while the cathode Tafel slope increased slightly.

Abstract: The hydrochloric acid pickling process which is widely applied in carbon steel pickling ensures high speeds with little pollution. In this research, hydrochloric acid pickling process was introduced into stainless steel pickling to improve the surface integrity. Research indicated that the impedance spectrum obtained from 430SS in HCl solution consisted of a capacitive loop at high frequencies and an inductive loop at low frequencies. As the concentration of hydrochloric acid rose, the radiuses of the capacitive loop decreased.And the corrosion potential of 430SS in hydrochloric acid solution moved to positive direction with band to a narrow 0.1V.And high HCl concentration more markedly influenced the charge-transfer resistance.

Abstract: The fine cathode material of LiFePO₄/MWCNTs composite was synthesized by ball milling. XRD demonstrated that the particle size of material was smaller when it was milled more time. And SEM showed that the MWCNTs was decentralized into the grains of LiFePO₄. The electrochemical performance of the composite electrodes milled 12h exhibited best electrochemical performance. The electroconductibility of this composite was larger than the others. The specific capacity of it was 132.8mAh/g. So appropriate milling can promote the performance of LiFePO₄/MWCNTs composite.

Abstract: In this work we present an electrochemical study using carbon paste electrode (CPE) with CuFeS₂ in solutions with different concentrations of Fe²⁺ ions in order to evaluate the possible interaction between these ions and mineral sulfide in the absence and presence of the bacteria Acidithiobacillus ferroxidans.

Abstract: The dissolution of gold-bearing pyrite plays an important role in bioleaching of gold. This paper describes a fundamental study on the electrochemical behavior and reaction mechanisms of gold-bearing pyrite leaching in the form of Carbon Paste Electrode (CPE) with and without microorganisms using Cyclic Voltammetry (CV) and polarization curve. A two step process was suggested from Cyclic voltammetry. Electrode passivation by elemental sulphur was observed below 700mV (vs. SCE), elemental sulphur was then oxidized to sulphate when the electrode potential further increased from 700mV. The polarization current density of CPE and the oxidation rate of pyrite are further enhanced by the presence of microorganisms. Analyses of EDS and XPS confirmed the formation of elemental sulphur and sulphate. This electrochemical method successfully showed its simplicity and reliability to measure oxidation rate of gold bearing pyrite.

Abstract: Abstract. In this study, the arsenopyrite was used as representative of gold-bearing sulfides in Carlin-Type gold ores to test the ability of oxidation on them by P. chrysosporium. After shaking incubation for 20 days, the conversion rates of iron, sulfur and arsenic in arsenopyrite were 6.28%, 35% and 21.76%, which were 44.86, 2.98 and 48.36 times compared with the asepsis system, respectively. It indicated that the P. chrysosporium could improve obviously the biotransformation rate of arsenopyrite by its own metabolic activity. The electrochemical oxidation behavior of arsenopyrite in the leaching system without and with P. chrysosporium were detected with electrochemical technology. The results showed that the P. chrysosporium did not change the oxidation mechanism of arsenopyrite, but strong oxidizing environment, which was structured by its products-oxidative enzymes and hydrogen peroxide, could promote the transformation from Fe2+ to Fe3+. P. chrysosporium could significantly decrease pitting potential and improve polarization current of arsenopyrite electrode and then accelerate its corrosion process. These indicated that P. chrysosporium was an available microorganism for degrading and transforming sulfides. P. chrysosporium could break gold inclusion and improve gold leaching rate, and finally realized economical and efficient application of Carlin-type gold ores.

Abstract: The machining quality of rolling bearing raceway has an important impact on bearing life. In this paper, the finishing experiment equipment of rolling bearing raceway is built and the mechanical and electrochemical mechanical experiments are conducted. The impact of clearance between cathode and workpiece, the rotation speed and the abrasive grain size on electrochemical mechanical machining quality is analyzed. The surface roughness decreases from Ra0.20μm to Ra0.04μm through electrochemical mechanical machining. The surface morphology of workpiece after finishing is observed. Contrast with the surface morphology after conventional mechanical polishing, the surface after electrochemical mechanical finishing is more suitable to the bearing raceway.