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1.
应用离子交换膜法电解邻氯硝基苯合成2,2′-二氯氢化偶氮苯.讨论了电极活化条件、电流密度、电解液温度等因素对电解还原反应的影响.结果表明:在反应温度t=80℃,阴极、阳极电解液分别为10%和30%(by m ass)的NaOH溶液,电流密度4.2A/dm2条件下电解,电流效率最高,可达73%,收率为83%. 相似文献
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研究了在不同电流密度下进行长时间极化后Pb-Ag(0.8%(质量分数,w))平板阳极的阳极电位、腐蚀率及阳极钝化膜.同时,也研究了该阳极在ZnSO4-MnSO4-H2SO4电解液中的阴极电流效率和阴极锌品质.阳极钝化膜的表面形貌用扫描电镜(SEM)进行观测.实验结果表明,不管电解液中是否存在Mn2+,电流密度对阳极和阴极的电化学行为都产生了显著的影响.随着电流密度的升高,阳极电位、腐蚀率、阴极电流效率和阳极泥生成量也增加,而阴极锌中的Pb含量则减少.当电流密度从500A·m-2降到200A·m-2时,阳极在ZnSO4-MnSO4-H2SO4电解液中的稳定电位和腐蚀率分别减少64mV和40%.此外,在比较低的电流密度下,阳极电位更容易稳定,阳极表面生成的钝化膜更加致密并与基体结合牢固,这些都有利于降低阳极腐蚀率.为了降低阳极电位、减小阳极腐蚀率及阳极泥生成量并提高阴极电流效率和阳极锌品质,锌电积的理想工作条件是较低的阳极电流密度和较高的阴极电流密度. 相似文献
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NaCl对离子液体中电解精炼铝的影响 总被引:1,自引:0,他引:1
研究了添加NaCl对BMIC-AlCl3离子液体电导率及电解精炼铝的影响,分析了阴极电流效率、电流密度的变化,并通过扫描电镜和能谱分析研究了沉积层的形貌及成分。结果表明,添加NaCl可以提高电解液的电导率,阴极电流效率也可提高至82%~96%,但电流密度则有所降低;添加NaCl还可以改善电解精炼铝的沉积质量,使晶粒尺寸... 相似文献
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在板框式循环电解槽中,以KOH为电解质,KI为催化剂,石墨电极分别为阳极和阴极,研究电化学间接氧化2-丁酮合成乙偶姻中间体α-羟基缩酮,讨论电流密度、极板间电解液流速、电解液中2-丁酮浓度、电解温度以及通电量等电解条件对中间体收率和电流效率的影响,经优选工艺条件为:电流密度40 mA·cm-2,流速6.4 cm·s-1,2-丁酮浓度1.75 mol·L-1,电解温度30℃,通电量为1.5 F·moL-1时,中间体收率可达78.9%,电流效率40.1%. 循环伏安测试结果表明,电解时碘离子在阳极氧化生成碘单质,甲醇在阴极还原生成甲氧基负离子,原料2-丁酮与电解产物反应,并最终生成乙偶姻中间体. 相似文献
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(NaPO3)6对AZ91D镁合金微弧氧化陶瓷层电化学腐蚀特性的影响 总被引:4,自引:0,他引:4
在Na2SiO3-KOH电解液体系中添加一定量的(NaPO3)6, 利用微弧氧化(MAO)技术在AZ91D 镁合金表面制备了原位生长的陶瓷层. 采用动电位极化和电化学阻抗谱(EIS)技术研究了添加(NaPO3)6前后, 制备的陶瓷层在3.5%(w) NaCl溶液中的室温电化学行为. 结果表明, 添加(NaPO3)6后, 陶瓷层的自腐蚀电位显著上升, 自腐蚀电流密度明显减小. 这主要是由于(NaPO3)6增加了反应过程中基体镁合金表面的“氧空位”和溶液中PO3-4的含量, 促使元素Mg在金属/膜层(M/F)界面上快速形成相应氧化物, 从而增加了陶瓷层的厚度和致密性. 根据电化学反应体系和陶瓷层的特殊结构, 建立了合理的等效电路, 并结合EIS 数据, 分析了添加(NaPO3)6提高陶瓷层耐电化学腐蚀性能的机理. 相似文献
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Pei Huang Junhui Lai Lianhuan Han Fang-Zu Yang Li-Min Jiang Jian-Jia Su Zhao-Wu Tian Zhong-Qun Tian Dongping Zhan 《中国科学:化学(英文版)》2016,59(11):1525-1528
Titanium (Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. With a home-made electrochemical machining workstation, cyclic voltammetry is performed at a wide potential range of [0 V, 20 V] to record the details of passivation and depassivation processes under a hydrodynamic mode. The results show that the thickness of viscous layer formed on the alloy surface plays a crucial effect on the electropolishing quality. The technical parameters, including the mechanical motion rate, polishing time and electrode gap, are optimized to achieve a surface roughness less than 1.9 nm, which shows a prospective application in the electrochemical machining of Ti and it alloys. 相似文献
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锌铋合金电极在溶胶电解液中的电化学行为 总被引:1,自引:0,他引:1
锌电极的自腐蚀速率, 持续放电下的阳极溶解速率和电极钝化的难易程度是碱性电池性能的重要电化学参数. 本文应用线性极化、恒流放电等电化学实验方法研究了电解液中添加Carbopol树脂以及电极中添加Bi对锌电极电化学行为的影响. 并应用金相显微镜和环境扫描电子显微镜(ESEM)对锌电极和锌铋合金电极浸蚀及放电后的形貌进行了表征. 结果表明: 电解液中添加适量的Carbopol树脂可明显提高电极的极化电阻, 显著降低电极的自腐蚀速率; 阳极的溶解电位出现不同程度的正移, 阳极过电位显著增大且大电流密度放电时较明显促进电极钝化. 锌电极中添加一定量的Bi对改善电极表面氧化物膜的沉积形貌和电极表面固液界面的传质条件, 减小电极的自腐蚀速率, 抑制电极自腐蚀等方面具有显著作用. 相似文献
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采用线性扫描伏安法研究了Lewis 酸性AlCl3-BMIC (BMIC: 1-butyl-3-methylimidazolium chloride)离子液体中铝电极的溶解. 铝电极在阳极极化时出现了钝化现象, 钝化是由于在铝电极表面形成了固体AlCl3钝化膜造成的. 铝的电化学溶解过程可以依次分为三个区: 电化学控制区、过渡区和钝化区. 在电化学控制区, 铝的电化学溶解速率随着电位的正移而逐渐增加; 在过渡区, 由于电极表面AlCl4-和Al2Cl7-浓度发生改变而析出固体AlCl3使得铝电化学溶解速率随着电位的正移而逐渐减小; 当钝化膜形成之后, 铝的电化学溶解速率不再随着电位的正移而发生改变, 铝溶解进入钝化区. 增加搅拌、升高温度、降低离子液体AlCl3摩尔分数都可以增加铝溶解阳极极限电流密度. 相似文献
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Weihua Yang Yan Zhou Honghui Wang Dongqin Bi 《Russian Journal of Electrochemistry》2009,45(7):795-799
Ferrate(VI) was prepared by electrooxidation in diaphragm electrolyzer with iron wire gauze as anode and NaOH-KOH mixed solution
as electrolyte. The influences of various experimental conditions, such as the volume ratio of NaOH-KOH mixed electrolyte,
temperature, current density, passivation of iron anode were investigated on ferrate current efficiency. Due to the low solubility
of K2FeO4 in concentrated alkaline solution and the passivation of iron wire gauze anode, a highest current efficiency over 90% was
obtained at 45°C and at a current density of 5 mA cm−2 in mixed electrolyte with the volume ratio of NaOH: KOH equal to 6: 4. The result is superior to using NaOH and KOH as electrolyte
respectively. In addition, polarization curves, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy
(EIS) were employed to further study the effects of synthesis conditions on ferrate(VI) in theory.
Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 7, pp. 853–857.
The article is published in the original. 相似文献
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Leszek Zaraska Elżbieta Kurowska Grzegorz D. Sulka Ilona Senyk Marian Jaskula 《Journal of Solid State Electrochemistry》2014,18(2):361-368
Porous anodic alumina layers were obtained by a simple two-step anodization of low purity aluminum (99.5 % Al, AA1050 alloy) in a 0.3 M oxalic acid electrolyte at 45 V and 20 °C. The effect of anode surface area on structural features of nanoporous oxide and process of oxide formation was investigated. An ordered structure composed of nanostripes or nanopores was formed on the Al surface during electrochemical polishing in a mixture of perchloric acid and ethanol. This nanopattern is then replicated during the anodic oxide formation. It was found that the pore diameter, interpore distance, and porosity increase slightly with increasing surface area of the aluminum sample exposed to the anodizing electrolyte. On the other hand, a slight decrease in pore density and cell wall thickness was observed with increasing surface area of the sample. The detailed inspection of current density vs. time curves was also performed. The obtained results revealed that the higher surface area of the anode, the local current density minimum, was reached faster during first step of anodization and the increase in current density corresponding to the pore rearrangement process was observed earlier. Finally, a dense array of Pd nanowires (~90 nm in diameter) was synthesized by simple electrodeposition of metal inside the channels of through-hole nanoporous anodic alumina templates with relatively large surface areas (4 cm2). 相似文献
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Wang Lei Shinohara Tadashi Zhang Bo-Ping 《Journal of Solid State Electrochemistry》2010,14(10):1897-1907
Corrosion behavior of extruded Mg, extruded AZ31 alloy, and cast AZ91 alloy was investigated by electrochemical measurements
in dilute NaCl solutions. Corrosion products and passivation films were analyzed by X-ray diffraction and X-ray photoelectron
spectroscopy. All specimens exhibit the corrosion and passivation zones in dilute NaCl solutions. The aluminum content and
alloy microstructure influence the corrosion and passivation processes. AZ91 alloy shows the broadest passivation zone followed
by AZ31 alloy and Mg. AZ91 alloy reveals a highest corrosion resistance, and preferential attack is located at the primary
Mg phase. Its relatively fine β-phase (Mg17Al12) network and Al2O3/Al(OH)3 compounds produced on the passivation film are the main factors which limit the corrosion progress as compared with AZ31
alloy and Mg. The thick passivation product on AZ31 alloy is the key factor which restricts the corrosion attack in dilute
solutions. 相似文献
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利用电化学阻抗(EIS)、扫描微参比技术(SRET)、接触角、粗糙度、附着力、盐雾等测试方法,研究了铝合金阳极氧化与贻贝黏附蛋白(MAP)/CeO2/硅烷γ-APS(MCA)表面复合修饰的腐蚀防护性能以及对改性聚氨酯涂层附着力和耐蚀性的影响。结果表明,MCA复合膜可抑制铝合金的腐蚀,并具有一定的自修复功能;阳极氧化和MCA表面复合修饰可为铝合金提供有效的早期腐蚀防护作用,且能提高铝合金表面粗糙度和润湿性,显著提升改性聚氨酯涂层在铝合金表面的附着力和耐蚀性,因而结合改性聚氨酯涂层和表面复合修饰可实现对铝合金长期有效的腐蚀防护。 相似文献
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K. V. Murzenko Yu. D. Kudryavtsev V. I. Balakai 《Russian Journal of Applied Chemistry》2013,86(8):1235-1242
Effect of the cathodic current density, pH value, electrolyte temperature, and concentration of aluminum oxide introduced into the electrolyte on the wear, microhardness, and internal stresses in nickel-cobalt-aluminum oxide composite electrolytic coatings was studied. It is shown that the coatings under consideration can be used instead of chromium coatings. 相似文献
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Kuang X.-Y. Jin S.-Q. Cao Y.-H. Zhang Y.-M. Dong S.-G. Zhu L.-H. Lin L.-W. Lin C.-J. 《电化学》2021,(6):624-636
The ordinary organic coatings on aluminum alloy usually encounter a problem of low adhesion to the substrate, which results in destruction and failure of the long-term protective performance of the anticorrosion systems. The surface modification of aluminum alloy is able to enhance the adhesion of organic coating on aluminum alloys, and to improve their protective performance. In this work, a combined surface modification of anodic oxidation and mussel adhesion protein/CeO2/3-aminopropyltriethoxysilane composite film (MCA) was developed on the aluminum alloy. The adhesion of modified polyurethane coated on the treated aluminum alloy and its corrosion protective performance were evaluated comprehensively by using contact angle, adhesion strength, electrochemical impedance spectroscopy (EIS), and scanning reference electrode technique (SRET). The measurements of EIS and SRET demonstrated that the MCA composite film on anodic oxidized Al possessed self-healing function and provided effective protection against early corrosion of aluminum alloy. The pull-off test showed that both anodic oxidation treatment and MCA composite film modification were able to increase the adhesion of modified polyurethane coating on aluminum alloy, and their combined action were supposed to remarkably enhance the adhesion strength up to 17.1 MPa. The reason for the improvement of adhesion was that the anodic oxidation treatment and MCA composite film modification could improve the surface roughness of aluminum alloy, and enhance the surface wettability and surface polarity, which is beneficent to enhance the bonding of the modified polyurethane coating to aluminum alloy surface. The EIS results showed that no any corrosion occurred for the modified polyurethane coating on the treated aluminum alloy during 65 d immersion in 3.5wt.% NaCl solution. The impedance value in low frequency range of the modified polyurethane coating always maintained at a high order of magnitude on the aluminum alloy treated by anodic oxidation and MCA composite film modification, showing an excellent protective performance of the coating system. The evaluation of Neutral Salt Spray (NSS) indicated that the modified polyurethane coating on the treated aluminum alloy owned superior corrosion protection performance, and the adhesion strength remained 13.1 MPa and no any corrosion was found at the scratch locations even after 1200 h of salt spray testing. It was concluded that combination of anodic oxidation and MCA composite film were capable of significantly improving the adhesion of modified polyurethane coating on aluminum alloy and providing long-term effective corrosion protection for aluminum alloy. © 2021 Authors. All rights reserved. 相似文献