Advanced Materials Research Vols. 194-196

Abstract: Power transformer on-line monitoring on dissolved gas in oil is one of the effective and technical means to achieve the transformer state detection and fault diagnosis, and oil-gas permeability is one of the core technologies to implement transformer on-line monitoring. The traditional methods of oil-gas separation such as vacuum method and mechanical oscillation method were unable to satisfy the requirements of transformer on-line monitoring; and the methods which were used commonly in recent years, like dynamic headspace separation, corrugated tube, carrier gas elution etc, have a high rate of gas-separation and have already been used in some on-line monitoring products. However, the problems still exist: easy formation of oil pollution, so the oil can not be recycled and the device structure is relatively complex. This paper based on the separation principle of polymer membrane, proposes mixed hollow fiber membrane made by polytetrafluoroethylene (PTFE) and polyhexafluoropropylene (PHFP), and designs an oil-gas separation test platform formed by the storage tank, oil-gas permeability tank, temperature controller and gas chromatographic analyzer etc, does laboratory research on the oil-gas permeability of the mixed hollow fiber membrane at different temperatures. The results show that, the permeability of the mixed hollow fiber membrane is obviously better than the commonly used single fluoride film or rubber film, seven fault gases H₂, CO, CO₂, CH₄, C₂H₆, C₂H₄, and C₂H₂ can be separated efficiently form transformer oil within 24 hours. More to the point, the equilibrium time is short, the gas permeability is high and the test platform structure is simple, all of these advantages provide a strong guarantee for the development of on-line monitoring technology on dissolved gas in transformer oil.

Abstract: The thermal decomposition behavior of gel precursor, the structure, morphology and electrochemical properties of NiO thin films prepared by sol-gel process were characterized by thermogravimetric/differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and constant current charge-discharge techniques. The results show that the gel precursor completely decomposes and gradually forms the nanocrystalline NiO at 450°C during the sintering. The NiO thin film is smooth, uniform and free of cracks drying at 200°C as pretreatment and sintering at a low temperature rise rate. The structure of NiO films sintered at 500°C for 2h becomes integrity, whose discharge capacity after 20 cycles remains at 714mAh/g. It is promising to be used in Li-ion battery for great initial specific capacity and well cycle performances.

Abstract: The various nitrogen gas (N₂) flows for depositing zirconium-nitride (ZrN) films on the substrate of a p-type (100) silicon wafer are investigated through reactive magnetron sputtering by a pulsed-DC power. The results, based on the design of experimental (DOE) method, indicate that the deposition effect of the ZrN_x film is obviously affected by various flow rates of nitrogen gas at the specific pulsing duty cycles. The crystal orientation of the zirconium-nitride film has a less order microstructure which is similar to an amorphous microstructure. Although the composition ratio of chemical elements is not identical in Zr and N, the surface roughness, grain size, and resistivity are the better feature. The deposition rate is inversely proportional to the nitrogen flow rate and the chamber pressure is also an important factor. The basic effect of N₂ flow rate on the surface roughness is rougher when more nitrogen gas is supplied. The resistivity of ZrN_x thin film has a positive relationship to N₂ flow rates at the reactive vacuum chamber.

Abstract: In order to decline the energy consumption in pulping process and keep the crystallinity of the cellulose in pulp, eucalyptus was selected in this study. Different quantities of ethanol, formic acid and MK2 and different experimental conditions led to different contents of alpha -cellulose and different crystallinities of the cellulose. The reduction of the kappa number of the pulp resulted from the increase of the liquor-to-wood ratio. With the addition of the MK2, a small quantity of ethanol could gain lower kappa number than original. Increasing the retention time and liquor-to-wood ratio played a significant role in keeping crystallinity with the addition of MK2.

Abstract: A solid superacid catalyst SO4²-/ZrO₂–Sm₂O₃-SiO₂ was prepared by a coprecipitation method and characterized by means of XRD, TEM and SEM. The kinetics of the esterification of palmitic acid and ethanol catalyzed by nano SO4²-/ZrO₂–Sm₂O₃-SiO₂ catalyst was studied in a stirred batch reactor for the synthesis of ethyl palmitate. The effects of reaction temperature, feed molar ratio, catalyst loading and reusability of the catalyst were evaluated. The optimum conditions were as follows: n(palmitic acid):n(ethanol)=1:5, w(SO4²-/ZrO₂–Sm₂O₃-SiO₂)=2.4%, reaction temperature 403K, and reaction time 2 h. The esterification efficiency of palmitic acid was about 82.6%. The experimental reaction rates were correlated using different rate models include the Eley–Rideal and Langmuir Hinshelwood Hougen Watson models.