Search

Abstract: The characteristics of grooving corrosion of oil coiled tubes by electric resistance welding were investigated by using electrochemical polarization tests and an immersed corrosion test. The welded tube exhibited severe localized corrosion in the welding zone. The post-weld heat treatments reduced the sensitivity of grooving corrosion. A corrosion groove occurred at the fusion line. The local heat treatment for the welding zone at 930°C adding the whole heat treatment for tubes at 690°C was beneficial to improve the resistance to the grooving corrosion. The reasons of the grooving corrosion were discussed from the microstructures and chemical compositions of the weld. [Copyright &y& Elsevier]

Abstract: A new rapid and sensitive FI method is reported for spectrophotometric determination of trace chromium(VI) in electroplating waste water. The method is based on the reaction of Cr(VI) with sodium diphenylamine sulfonate (DPH) in acidic medium to form a purple complex (λ max =550nm). Under the optimized conditions, the calibration curve is linear in the range 0.04–3.8μgml−1 at a sampling rate of 30h−1. The detection limit of the method is 0.0217μgml−1, and the relative standard deviation is 1.1% for eight determinations of 2μgml−1 Cr(VI). The proposed method was applied to the determination of chromium in electroplating waste water with satisfactory results. [Copyright &y& Elsevier]

The high-performance LiNi 0.5 Mn 1.5 O 4 has been prepared by an improved solid-state method, which is calcined in nitrogen at the first stage and in air at the second stage. The reaction process between nickel atoms and manganese atoms was changed by the improved solid-state method. The final product is a high purity cubic spinel structure (Fd3m) with high crystallinity, little impurities and excellent electrochemical performances. The EDX demonstrates that there is slightly lower nickel content and carbon content on the crystal surfaces. It shows a discharge capacity of 138 mAh/g at the first cycle and 133.9 mAh/g after 100 cycles at 0.1C rate. It also can deliver a discharge capacity of 111.3 mAh/g at 5C rate. The discharge capacity of the cathode at 55 °C is up to 124 mAh/g with capacity retention of 96.1% after 100 cycles. These results show that the improved solid-state method has potential application for the large-scale synthesis of LiNi 0.5 Mn 1.5 O 4 in high power Li-ion batteries. [ABSTRACT FROM AUTHOR]

LiNi 1/3 Co 1/3 Mn 1/3 O 2 is successfully coated with MnO 2 by a chemical deposition method. The X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) results demonstrate that MnO 2 forms a thin layer on the surface of LiNi 1/3 Co 1/3 Mn 1/3 O 2 without destroying the crystal structure of the core material. Compared with pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , the MnO 2 -coated sample shows enhanced electrochemical performance especially the rate capability. Even at a current density of 750 mA g −1 , the discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 is 155.15 mAh g −1 , while that of the pristine electrode is only 132.84 mAh g −1 in the range of 2.5–4.5 V. The cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) curves show that the MnO 2 coating layer reacts with Li + during cycling, which is responsible for the higher discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Electrochemical impedance spectroscopy (EIS) results confirmed that the MnO 2 coating layer plays an important role in reducing the charge transfer resistance on the electrolyte–electrode interfaces. [ABSTRACT FROM AUTHOR]

Abstract: Li[Li0.2Mn0.54Ni0.13Co0.13]O2 was prepared using a coprecipitation method and modified with Li4Ti5O12. The sample coated with 3wt% Li4Ti5O12 exhibited the best cyclability and mean coulombic efficiency in the voltage range of 2.0–4.75V. These improvements are attributed to the effective Li4Ti5O12 coating layer, which stabilizes the host structure, protects the electrode surface from electrolyte attack, and prevents the formation of a thick passive film on the electrode surface. The initial irreversible capacity loss was eliminated by blending with 10wt% Li4Ti5O12, in the larger potential window of 1.5–4.75V. It was confirmed that the irreversible capacity loss decreased with increasing Li4Ti5O12 content; this is because Li4Ti5O12 offers a larger number of available sites for insertion of extracted lithium. [Copyright &y& Elsevier]