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11.
Xie R.Cheng K.Xie X. 《腐蚀科学与防护技术》2016,(6):555-559
The degradation process of Ni-Co coating on plate of Kovar alloy 4J42 in 3.5%NaCl solution was studied by means of electrochemical impedance spectroscope (EIS). Four distinguished electrical equivalent circuits (EEC) were proposed to simulate the degradation process. At the very beginning of immersion, the coating exhibited excellent corrosion resistance, which could be treated as a barrier layer with a high resistance in parallel with a low capacitance. After a short time of immersion, a double-layer capacitance Cdl and a charge-transfer resistance Rct were introduced, indicating that the electrochemical reactions at the metal/coating interface may take place. In the late stage of immersion, Warburg impedance was adopted to characterize the corrosion products. With the accumulation of the corrosion products, the diffusion process of corrosive medium was affected, and the EEC comprising a diffusion capacitance (Cdiff) and a diffusion resistance (Rdiff) was then introduced to fit the impedance spectra. The evolution of coating resistance and coating capacitance were investigated to illuminate the Ni-Co coating degradation process. The results showed that the degradation process of Ni-Co coating could be described by three stages: the permeation of corrosive medium, the corrosion of metal at the interface of coating/substrate and finally the failure of coating. © 2016, Corrosion Science and Protection Technology. All rights reserved. 相似文献
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熔融Ni-Co合金表面张力的测量与分析 总被引:2,自引:0,他引:2
Ni-Co高温合金广泛用于生产燃气涡轮机叶片和热交换器等工作于高温和腐蚀环境的零部件,采用改良静滴法测定了1773~1873K温度范围内熔融Ni,Ni-(5~10)%Co合金在Al2O3基板上Ar 3%H2气氛下的表面张力.熔融Ni,Ni-(5~10)%Co合金的表面张力随着温度的升高而降低.在此基础上采用Butler模型推导了表面张力随温度与浓度的变化,计算了合金体系中元素的偏聚.结果表明,Co在合金表面的浓度低于在体相的浓度. 相似文献
14.
In this paper the polarization characteristics of the processes of Ni and Co powders and Ni-Co alloy powders electrodeposition from ammonium sulfate containing supporting electrolyte are investigated as a function of Ni2+ and Co2+ ions concentrations. It is shown that the correct polarization curves for Ni and Co powders and Ni-Co alloy powders electrodeposition could be obtained only after IR drop correction, since the total current density of electrodeposition at the most negative potential of −1.4 V versus Ag|AgCl is extremely high (up to about 3-6 A cm−2) as a consequence of simultaneous hydrogen evolution which starts immediately after the beginning of metals (alloys) deposition. After determining the current density for hydrogen evolution and its subtraction from the total current density, correct polarization curves for Ni and Co powders and Ni-Co alloy powders electrodeposition are obtained. They are found to be different for each ratio of Ni2+/Co2+ ions concentration. It is also concluded that the shape of the polarization curves in all cases is practically defined by the shape of the polarization curve for hydrogen evolution. The morphology and composition of electrodeposited powders were also found to be sensitive to the ratio of Ni2+/Co2+ ions concentration. 相似文献
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采用复合电沉积法制备了AC(活性炭) / Ni-Co 复合电极。XRD 和SEM 测试结果表明, AC 微粒的复合未改变Ni-Co 合金电极的物相结构, 但使镀层的表面粗糙度和真实表面积增大。通过稳态阴极极化曲线和电化学交流阻抗技术考察了不同电极在1 mol·L-1 NaOH 溶液中的催化析氢性能, 结果表明, 镀液中AC 含量为3 g·L-1时所制备的AC/ Ni-Co 复合电极较Ni 电极和Ni-Co 合金电极具有更高的催化析氢活性, 电流密度为30 mA·cm-2时, 析氢反应极化电位分别比Ni 电极和Ni-Co 合金电极正移230 mV 和140 mV , 表观交换电流密度分别是Ni 电极和Ni-Co 合金电极的42 倍和9 倍, 复合电极催化析氢性能的提高主要归因于电极真实表面积的增大。 相似文献
17.
Surface Tension of Molten Ni and Ni-Co Alloys 总被引:3,自引:0,他引:3
Kiyoshi NOGI 《材料科学技术学报》2005,21(2):201-206
Surface tension of molten Ni and Ni-Co (5 and 10 mass fraction) alloys was measured at the temperature range of 1773-1873 K using an improved sessile drop method with an alumina substrate in an Ar+3%H2 atmosphere. The error of the data obtained was analyzed. The surface tension of molten Ni and Ni-Co (5 and 10 mass fraction) alloys decreases with increasing temperature. The influence of Co on the surface tension of Ni-Co alloys is little in the studied Co concentration range. 相似文献
18.
为促进金属粒子在膜孔中生成,采用膜相渗透和化学镀结合的方法,研究了化学镀NiCo/PTFE磁性复合膜的工艺.在正交试验结果基础上探讨了主盐离子浓度比、NaOH浓度、N2H4浓度、反应温度和反应时间对NiCo/PTFE复合膜中金属含量和磁性能的影响.本工艺最佳配方为:0.14 mol/L CoCl2·6H2O,0.06 mol/L NiCl2·6H2O,0.90 mol/L NaOH,0.45 mol/L C4H4O6KNa·4H2O,0.45 mol/L N2H4·H2O;最佳参数为:70~75℃,75 min.结果表明,相对于传统的双面金属化处理,引入膜相渗透的单面活化有助于镍钴金属粒子在膜孔内原位生成. 相似文献
19.
Magnetic field-induced solvothermal synthesis of one-dimensional assemblies of Ni-Co alloy microstructures 总被引:1,自引:0,他引:1
One-dimensional magnetic Ni-Co alloy microwires with different microstructures and differently shaped building blocks including
spherical particles, multilayer stacked alloy plates, and alloy flowers, have been synthesized by an external magnetic field-assisted
solvothermal reaction of mixtures of cobalt(II) chloride and nickel(II) chloride in 1, 2-propanediol with different NaOH concentrations.
By adjusting the experimental parameters, such as precursor concentration and Ni/Co ratio, Ni-Co alloy chains with uniform
diameters in the range 500 nm to 1.3 μm and lengths ranging from several micrometers to hundreds of micrometers can be obtained.
A mechanism of formation of the one-dimensional assemblies of magnetic Ni-Co microparticles in a weak external magnetic field
is proposed.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
This article is published with open access at Springerlink.com 相似文献
20.
Ni-Co coatings were produced on Cu substrates by electrodeposition from electrolytes with different pH values and different Co2+ concentration. The current efficiency increases from 52.1% to 81.2% with the pH increasing from 2.0 to 5.4. It is clearly observed that the content of cobalt in the deposited coatings gradually increases from 9.4% to 19.6% as the pH value varies from 2.0 to 5.4. The Co content in the deposited coatings increases from 16.5% to 72.7% as the molar ratio of CoSO4/NiSO4 varying from 1:5 to 1:2 in electrolyte. XRD patterns reveal that the structure of the coatings strongly depends on the Co content in the binary coatings. Both granular and dendritic crystals were investigated by SEM and the different crystallization behaviors were illustrated. The saturation magnetization of the coatings goes up from 96.36 kAm−1 to 136.08 kAm−1 with the pH value increasing from 2.0 to 5.4. The saturation magnetization (Ms) and coercivity (Hc) move up from 144.84 kAm−1 and 15.27 kAm−1 to 175.13 kAm−1 and 125.20 kAm−1 with the increase of Co in the electrolyte, respectively. 相似文献