Yu Wen Liu

Influence of NaCl on dechromization of Cu-Cr-Al alloy in H3PO4 solution

Abstract The dechromization of Cu-Cr-Al alloys was investigated by a static immersing corrosion test. The influence of NaCl on the dechromization was analyzed by electrochemical test, scanning electron microscopy, optical microscopy and X-ray fluorescence spectroscopy. The results show that the dechromization of Cu-Cr-Al alloys will take place in a H3PO4 solution of 11.32 mol/L at 55 °C. And the corrosion process occurs initially at the interface between Cu and Cr phase, and then extends inward Cr-phase inside. The addition of NaCl into H3PO4 solutions can shorten the dechromization incubation time, decrease the dechromization temperature and concentration of H3PO4 solution, and increase the tendency of dechromization. But, the NaCl scarcely has an effect on the form and structure of chromium depleted-layer.

The Influence of Deformation on Dechromization Corrosion of CuCr Alloy in H3PO4 Solutions

The influence of deformation on dechromization of CuCr alloy in H3PO4 solutions was investigated by static immersion corrosion tests. The properties of undeformed and deformed alloys were characterised by XRD, Metallograph, SEM and X-ray fluorescence spectrometer respectively. It is observed that the deformation plays an important role in dechromization of CuCr alloys in H3PO4 solutions. Compared with undeformed one, the deformed CuCr alloy’s incubation time of corrosion is shortened, the concentration and temperature of H3PO4 solutions needed for dechromization decrease. Consequently the tendency of dechromization increases. Surface analysis showed that the microstructure of the dechromization layer is scarcely influenced. Finally, the dechromisation mechanism was discussed.

Effects of High Pressure Treatment on Microstructure and Corrosion Resistance of Brass

Effects of high pressure heat treatment on the microstructure refinement and corrosion resistance of brass were studied by means of metallographic observation, SEM/EDX, profilometer and CH1660A electrochemical instrument. Brass were heated from 23°C to 700°C and kept at 700°C for 10 minutes under high pressure of 1GPa, 3GPa, 4GPa and 6GPa, respectively. The results show that high pressure heat treatment has great influence not only on the microstructure refinement of the alloy but also on its corrosion resistance in HCl solution. Under 3GPa, the refined microstructure can be found and the corrosion resistance of the alloy changes into much worse. However, under a higher pressure of 6GPa, the corrosion resistance increases and the microstructure refining effect is not obvious. All the findings of this work were elucidated in terms of the change in the formation and growing of the crystal under a high pressure heat treatment condition.

Investigation of Structure and Properties of PET Multifilament Irradiated with UV in Different Atmosphere

Changes of mechanical properties and chemical structure of polyester (PET) fibers are studied through UV simulated accelerated ageing experiments with N2, air and O3 as the atmosphere. The structure, thermal stabilities and tensile strength are obtained by FTIR, DTA-TG, XRD, SEM and micro-mechanics test. The difference of degradation process in various atmospheres is discussed in this paper. The results show that the fracture tensile strength of PET multifilament decreases with the increase of UV irradiation time. And oxidation and then decarbonylation take place on the surface. Besides, Melting temperature (Tm), the temperature of quality loss by 10% (T10) and the crystallization also decrease. However, in O3 atmosphere the oxidation develops very quickly and fully, therefore, the carbonyl on the surface is eliminated and decreases significantly, and the tensile strength decreases much faster than those in N2 and air. The skin layer of irradiated fibers appears serious damaged. The mechanism of chemical degradation for samples irradiated in N2 environments is similar to those irradiated in air.

FT-IR Analysis of Molecular Structure Evolvement of Poly(Ether urethanes) in Ozone Atmosphere

The failure behavior of Poly (ether urethanes) in ozone atmosphere was investigated by FTIR, UV-Vis spectra and SEM analysis. It is found that some oxygen-containing groups such as the hydroxyl group and the carbonyl group increase first and then slightly decrease with the ozone oxidation time and the carbohydryl and ether bonds decrease slowly. After oxidation by ozone, the polyurethane molecule chains break on C-O in ether and urethane groups instead of chain crosslinking. In addition, ozone oxidization increases the color difference and lowers the UV light transparence of polyurethane.

Study on Structure and Electrochemical Performance of LiFePO4/C Modified by PANI

LiFePO4 has attracted broad attention as a promising cathode material for lithium ion batteries. The key issues related to LiFePO4 performance lie on the intrinsic characteristic of poor diffusion of lithium ions through an interface between LiFePO4 and FePO4. To explore the effect of polyaniline on performances, LiFePO4/C cathode materials were prepared via hydrothermal method, using glucose as a carbon source and polyaniline as a modifier. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), galvanostatic charge–discharge test and cyclicvoltammetry (CV). The results show that the olivine-type phase of LiFePO4/C is not changed by polyanilines and LiFePO4/C is composed of relatively large particles of about 400nm and some nano-sized polyaniline particles, which favor the electronic conductivity. The LiFePO4/C cathode material modified by 10% polyaniline has the highest uniformity. It delivers the capacity of 167.9mAh/g at 0.1C, and has good reversibility and high capacity retention.