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991.
Numerical analysis of galvanic corrosion of Zn/Fe interface beneath a thin electrolyte 总被引:1,自引:0,他引:1
Jong-Min Lee 《Electrochimica acta》2006,51(16):3256-3260
A numerical analysis of galvanic corrosion of a Zn/Fe interface beneath a thin layer electrolyte is presented. Specifically, a circular defect, where the zinc coating has been removed, is considered. It is assumed that both oxygen reduction and iron oxidation can occur on the Fe surface, while only zinc oxidation occurs on the Zn surface. The importance of electrolyte thickness and conductivity and defect radius is considered. It is assumed that the iron and zinc oxidation rates are described by a Tafel relationship. If the kinetic parameters of the oxidation reactions are known, the cathodic protection of Fe is a function of a Wagner number, the ratio of the electrolyte thickness to the defect radius, and the ratio of the radius of the defect to the outer radius of the zinc layer. 相似文献
992.
993.
In situ synchrotron X-ray studies on copper-nickel 5 V Mn oxide spinel cathodes for Li-ion batteries
Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both metals in the spinel lattice structure reduces the 3.9-4.2 V potential plateaus associated with the conversion of Mn3+ to Mn4+. Higher potential plateau associated with oxidation of the substituted transition elements is also observed. These substituents also significantly alter the onset of Jahn-Teller distortions in the 3 V potential plateau. Synchrotron based in situ X-ray absorption (XAS) was used to determine the exact nature of the oxidation state changes in order to explain the overall observed capacities at different potential plateaus. The studies on LiCu0.5Mn1.5O4 show single phase behavior in the 4-5 V potential region with a good cycle life. Lower cycle life characteristic observed in cycling LiNi0.5Mn1.5O4 and LiNi0.25Cu0.25Mn1.5O4 versus Li metal are ascribed to coexistence of several phases in this potential region. However, LiCu0.5Mn1.5O4 shows onset of Jahn-Teller distortions in the 3 V potential plateau, in contrast to LiNi0.5Mn1.5O4 and LiNi0.25Cu0.25Mn1.5O4 cathode materials. 相似文献
994.
Wei Xie Rebecca Heltsley Xinhua Cai Fuquan Deng Jiemin Liu Charles Lee Wei‐Ping Pan 《应用聚合物科学杂志》2002,83(6):1219-1227
The oxidative stability of the carbon fiber‐reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off‐gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190–220°C. Based on the off‐gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371°C, thereby marking 371°C to be the highest accelerated aging temperature for its long‐term lifetime prediction. Beyond 371°C, different degradation mechanisms would apply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1219–1227, 2002 相似文献
995.
Electrospinning of poly(lactic‐co‐glycolic acid) (PLGA) in chloroform or 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was investigated, focusing on its solution parameters, to develop nonwoven biodegradable nanofibrous structures for tissue engineering. PLGA nanofibers were obtained by electrospinning of 15 wt % PLGA solution and the resulting average fiber diameters were varied with the range of 270–760 nm, depending on solution property. When small amounts of benzyl triethylammonium chloride (BTEAC) was added to the PLGA/chloroform solution, the average diameter was decreased from 760 to 450 nm and the fibers were densely amounted in a straight shape. In addition, the average fiber diameter (270 nm) of nanofibers electrospun from polar HFIP solvent was much smaller than that (760 nm) of nanofibers electrospun from nonpolar chloroform solvent. Therefore, it could be concluded that conductivity or dielectric constant of the PLGA solution was a major parameter affecting the morphology and diameter of the electrospun PLGA fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1214–1221, 2006 相似文献
996.
Summary Three pairs of polyimide/polyimide blends (50/50 wt%) with different molecular structures were prepared by two ways, i.e. mixing of the polyamic acid precursors with subsequent imidization, and direct solution mixing of the polyimides. The blends were studied with DMA technique. The results obtained show that all the blends prepared with these two different ways are miscible, as there existed only one glass transition temperature (Tg) for all the blends. It is suggested that the miscibility of these polyimide/polyimide blends is a result of the strong inter-molecular charge-transfer interaction between the chains of their components. 相似文献
997.
5—烃基—2,3—二甲基吡嗪的合成 总被引:4,自引:1,他引:4
2,3-二基-5,6-二氢吡嗪与醛或酮在氢氧化钠的乙醇溶液中反应制得16种5-烃基-2,3-二甲基吡嗪。产率66%~90%。其中6种为新合成的化合物。产率17%~87.9%。 相似文献
998.
In this work mathematical models were developed to represent the kinetics of volume changes of fluid spaces associated with
infusion of Ringer’s solution. During infusion of Ringer’s solution, the human body is assumed to be characterized by the
two-fluid space model which has second volume space in addition to the first volume so that fluid exchanges between these
two spaces are possible. Various infusion types were tested to accommodate different medical situations. Volunteers were given
Ringer’s solution and the changes in blood hemoglobin were detected. From the comparison with experimental data, the two-fluid
space model was found to represent adequately the kinetics of human volume expansion during infusion of Ringer’s solution. 相似文献
999.
蛋白质在超滤过程中的膜污染和膜清洗 总被引:9,自引:0,他引:9
本文选用四种不同的膜清洗剂对牛血清蛋白溶液超滤后污染的三种超滤膜进行研究,结果表明:在蛋白质的等电点取得在不同PH值下蛋白质对膜污染的最佳清洗效果,清洗效率与蛋白质的所荷电荷有关。采用适宜的清洗过程将会延长膜使用寿命和增强超滤膜性能。 相似文献
1000.
Forced convection heat transfer in low prandtl number turbulent flows: Influence of axial conduction
Shong-Leih Lee 《加拿大化工杂志》1982,60(4):482-486
The effect of axial conduction was investigated for turbulent heat transfer in a round pipe with uniform wall temperature. Exact solutions were obtained by using the method of separation of variables for the two cases with and without the axial conduction term. The solutions show that the effect of axial conduction is important at low Peclet numbers, say Pe < 100, but negligible in the thermally fully-developed region. Also, the fully developed Nusselt numbers depend only on Reynolds number at low Peclet numbers and the interpolation formula is proposed: which fits the calculated data well in the liquid metal range 0.001 < Pr < 0.022 for Pe < 100. 相似文献