Degradation processes of carbon negative electrodes for all-solid lithium polymer batteries were investigated using X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and Scanning Electron Microscope (SEM). The cycling performances of the electrodes are significantly affected by the mixing speed of the electrode slurry. The cross-sectional SEM images of the electrodes containing vapor-grown carbon fiber (VGCF) show that more voids remained in the electrodes, if the slurry was mixed at high speed. The voids in the composite electrode expand and increase during the cycling test of the cell resulting in the capacity fading. On the other hand, the electrodes containing carbon nanotubes (CNT) show an opposite trend, because the high mixing speed improves the dispersibility of the CNT resulting in the formation of the less voids in the electrode. The electrode containing both VGCF and CNT prepared at high mixing speed shows the best cycleability among all the electrodes. In spite of some voids initially form in the electrode, the CNT seems to have prevented further increase and expansion of the voids.
This paper investigates the application of Electrochemical Noise (EN) to study the corrosion behavior of 304 nuclear-grade (NG) stainless steel (SS) in high purity water system at varying temperatures (105, 160, 190, 220, 250, 293°C) and pressures (0.6, 7, 9, 10.5, 16, 19 MPa). An EN sensor has been developed and applied to the high temperature water system. The potential and coupling current noise were recorded simultaneously and a variety of analytical methods (such as wavelet transform, chaos theory, noise resistance (Rn), the spectral noise resistance (Rsn) and the direct current (DC) limit of the spectral noise resistance (Rsn0)) have been used to obtain corrosion rate and corrosion form. EN analysis results demonstrated an increase in Rn with increasing temperature and pressure, except for a peak value at 293°C, 19 MPa, which was possibly due to the change in the thickness of passive film; combined chaos analysis results with morphology analysis, we may infer that the corrosion form of 304NG SS under high purity water system at high temperature and high pressure is general corrosion.
Ionic vacancies created in copper electrodeposition have been first observed by converting to microbubbles via. nanobubbles. Since the copper deposition potential was much more positive than hydrogen evolution one, the microbubbles were ascribed not to hydrogen bubbles but to the ionic vacancies. Then, the evolution times of the microbubbles at an overpotential of −300 mV were examined under various magnetic flux densities.
The corrosion properties of chromium nitride (CrN) coating on nickel have been evaluated in order to improve the anti-corrosion of metallic bipolar plate materials with applications such as redox flow batteries. The CrN layers are prepared by nitridation of electroplated Cr layers with different thickness. The nitrogen content of CrN coating layers varies from 0.5 to 4.2 wt% depending on nitriding time and coating layer thickness. Electrochemical and chemical corrosion behaviors are investigated by potentiodynamic polarization test in 5% sulfuric acid and by immersion test in 50% sulfuric acid, respectively. Electrochemical analysis of corrosion potential and corrosion current density as well as passivation behavior and chemical corrosion rate prove conclusively that an intact thin CrN layer is more corrosion resistant than thicker layers where cracks are developed. Sheet resistance of CrN coating layers before and after the corrosion test exhibits no significant difference. The improved corrosion resistance and the excellent stability of CrN coating layers suggest an efficient anti-corrosion method for metallic bipolar plate materials.
Ciliate Euplotes octocarinatus centrin (EoCen) is a member of the EF-hand super family of calcium-binding proteins, which is associated with the centrosomes. In this work, the interaction between N-terminal of EoCen (N-EoCen) and Eu3+ was investigated by cyclic voltammetry and UV-Vis spectroscopies. The result shows that a 2:1 of Eu3+ to N-EoCen complex (Eu2-N-EoCen) is formed. The electrochemical characteristics of Eu2-N-EoCen at a multi-wall carbon nanotube/Nafion composite film modified glassy carbon electrode (MWNT/Nafion/GCE) were then investigated in detail, from which a direct, quasi reversible electron transfer of Eu2-N-EoCen had been obtained. According to the Laviron diffusionless-controled equations, the electron transfer rate constant ks, was calculated to be 2.33 ± 0.14 s−1. The pH dependence of the formal potential of Eu2-N-EoCen suggests that protonation accompanies electron transfer between pH 5.5–7.4. The electrochemical redox and quantitative analysis of Eu2-N-EoCen are therefore of great significance not only studying the physiological processes of Eu2-N-EoCen in organisms but also the interaction mechanism with target protein.
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