锌电极在氢氧化钾溶液中阳极惰化时的表面相变的研究

本文试图进一步从动力学方面证明恒电位下的锌电极在KOH溶液中阳极惰化时,阳极溶解电流随时间而缓慢下降是由于“表面相变”所引起。用恒电位法测取了锌电极在不同浓度的KOH溶液中电流对时间的曲线。实验结果与推导的动力学方程式相符,表明在恒电位惰化条件下,锌电极表面上最初形成的[Zn(OH)_2]_(ad)在OH~-参预下徐缓地转变为较不易溶的[ZnO]_(ad),因而导致阳极溶解电流的下降。这一表面相变过程可表示如下:     

稀土氧化物对二次锌电极性能的影响

应用阴极极化法在锌电极上覆盖一层稀土氢氧化物膜La(OH)3或Ce(OH)3,并用循环伏安、动电位极化、定电位阴极极化实验研究其电化学性能.结果表明,La(OH)3或Ce(OH)3膜能抑制锌酸根离子的迁移,提高析氢过电位,降低腐蚀电流密度并能抑制枝晶生长.SEM观测显示,稀土氧化物La2O3或CeO2改变了锌沉积形态,进而提高了锌酸钙电极的充放电循环性能.     

Sebacic acid as corrosion inhibitor for hot-dip galvanized (HDG) steel in 0.1 M NaCl

The potential of sebacic acid as a corrosion inhibitor for hot-dip galvanized steel in 0.1 M NaCl solution has been investigated. Different concentrations of the organic acid have been tested in order to understand the inhibition mechanism of the compound. The electrochemical test revealed a competitive mechanism between the dissolution of the metal in the acidified solution and the inhibition provided by the dicarboxylic species. The formation of a whitish layer consisting of zinc carboxylates and corrosion products was proved by means of scanning electron microscopy (SEM) investigation combined with Fourier transform infrared (FT-IR) analysis. A bidentate bridging coordination between the Zn(II) and the carboxylic species is suggested.     

Anodic dissolution of osmium in acid media

The anodic dissolution of Os in acidic solutions was studied under potentiostatic conditions. The results show high dissolution rates that increase markedly at rising potential. The presence of chloride ions and to a greater extent the increase in acidity of the solutions inhibit the anodic corrosion process. The nature of the dissolution products did depend on the solution pH and the concentration of the complexing anion. Thus, in HClO₄ acid and in chloride solutions at low concentration or acidity, Os goes into solution as OsO₄; in concentrated HCl solution, tetraoxide and chloro-osmyl anions are formed. No OsCl₆^2? complex was detected in solution even at high HCl concentration.     

Iron dissolution in aqueous AOT solution

The effects of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) on the electrochemical behavior of iron were studied by potentiodynamic and potentiostatic techniques and open-circuit potential measurements. Experiments were made in both neutral and alkaline AOT solutions (pH 7 and pH 12). It was found that AOT-assisted dissolution is initiated on a passivated iron surface and that the oxidation current leads to the formation of a gel-like film on the electrode surface. This dissolution process was investigated as a function of pH, potential, and electrode rotation rate and the corrosion products were characterized by polarizing microscopy, SEM/EDX, and IR spectroscopy. The gel-like material is a mixed NaAOT-Fe(AOT)3 lamellar mesophase and a structure for this mesophase is proposed.     

Kinetics and mechanism of benzyl chloride reaction with zinc in dimethylacetamide

Oxidative dissolution of zinc in the system of benzyl chloride-dimethylacetamide was investigated. The reaction stereochemistry as well as intermediates and reaction products formed were studied. The kinetic and thermodynamic parameters of the process were measured. The process was shown to follow the Langmuir-Hinshelwood mechanism with the formation of benzyl radicals and mono-solvated organozinc compound on the zinc surface. The components of mixture are adsorbed at various sites of the zinc surface, while recombination and the isomerization of the benzyl radicals occurs in solution.     

Zn-La合金制备及其电化学性能研究

采用固相扩散法合成Zn＿La合金,并研究La对锌电极化学性能的影响.实验表明:La的适量添加能抑制锌电极的枝晶及腐蚀等问题,从而明显改善锌电极的循环性能,其中以0.5at.%La的添加量为最佳.在100mA/g电流密度下,循环80周期后,其放电容量仍达520mAh/g,XPS测试表明,La主要以La2O3/La(OH)3的形式附着在锌电极表面上.正是由于La2O3/La(OH)3的存在,显著改善了锌电极的循环充放电寿命.     

Use of binary metal deposits on a cylindrical carbon-fiber microelectrode in the voltammetric determination of metal ions

The effect of binary metal deposits on a cylindrical carbon-fiber microelectrode on the determination of metals by direct and stripping voltammetry was studied. The electrolytic deposition of a binary system of copper and thallium, cadmium, lead, or mercury on the electrode in an alkaline solution resulted in the disappearance of the electroreduction peak of dissolved oxygen in the potential range from -0.8 to -1.4 V and in a decrease in the background current. Under the conditions of limited diffusion, the peak currents of Ni(II), Co(II), and Zn(II) in differential pulse voltammograms were 3–7 times higher than those calculated for a reversible electrode process under the conditions of semi-infinite diffusion. Because of this, the determination limit for metal ions in direct voltammetry was lowered to 1 X 10^-6 M. With a binary copper-thallium system, the peak current of zinc(II) reduction can be be detected in the presence of 5000-fold molar amounts of copper(II). The deposition of binary copper-lead and copper-thallium systems under the conditions of limited diffusion reduced the effect of negative interaction between the components of these systems and made possible the determination of lead(II) and thallium(I) by stripping voltammetry using additional peaks.     

Effects of compositional and structural features on corrosion behavior of nickel–tungsten alloys

Ni–W alloys were electrodeposited onto copper foil from citrate solution. Coatings containing from 11 to 21 at.% W and having 7–52 μm in thickness were obtained. The structure of these alloys was analyzed by X-ray diffraction and by using electron and light microscopy techniques. Alloys with 11 and 15% W are composed of two phases: solid solution of W in fcc Ni and solid solution of Ni in bcc W. An increase in W content in the Ni–W alloys to ca. 18–19% of W resulted in the grain refinement and the transition to amorphous structure. The corrosion behavior of obtained Ni–W and unalloyed Ni coatings was studied in 0.5 M NaCl solution by means of electrochemical impedance spectroscopy, potentiodynamic polarization and light microscopy. Comparing to pure Ni, the obtained Ni–W coatings exhibited a clearly decreased corrosion resistance (in terms of corrosion current density and polarization or charge transfer resistance at the open circuit potential). Despite of the quite wide range of composition of the alloys under test, the related grain refinement, and the transition to the amorphous structure, no clear relation between the corrosion rate and W content was detected. This behavior can be a result of the interplay of the activating effect of grain refinement or preferential dissolution of W from one side and diffusion barrier action or inhibition provided by the surface film of W oxidation products from the other side. The differences observed in the corrosion resistance of Ni–W coatings are more related to their morphological imperfections arising from various deposition conditions than to the W content. Some samples showed a rather non-uniform nature of corrosion (pronounced attack along cracks). An inversion in the dissolution behavior of Ni–W and unalloyed Ni was observed with increasing anodic potential. Contrary to pure Ni, Ni–W coatings were resistant to pitting corrosion in NaCl solution. Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical/Chemical Reactivity of Metastable Materials, Warsaw, 17th–21st September, 2007.     

含钪铝镁合金微生物腐蚀行为的研究

采用电化学、微生物学和表面分析的方法，研究了厌氧环境硫酸盐还原菌（subtere ducing bacteria，SRB）溶液中Al-6Mg-Zr添加Sc元素前后的腐蚀行为。结果表明，添加Sc元素后，合金的氧化膜更加致密，具有更好的保护作用，使电极开路电位正移100mV左右，同时Sc元素的加入降低了材料在SRB菌液中的点蚀敏感性，使材料耐微生物腐蚀性能得到提高，但是添加Sc后的合金对SRB更加敏感。显微观察表明添加Sc前后两种铝镁合金的腐蚀特征均为点蚀，能谱分析表明随浸泡时间增加，腐蚀越来越严重，腐蚀产物堆积和阳极金属溶解造成进一步腐蚀。     

Electrochemical co-reduction of Y(III) and Zn(II) and extraction of yttrium on Zn electrode in LiCl-KCl eutectic melts

This work presents an electrochemical study of Y(III) ions on W electrode and liquid Zn electrode and co-reduction mechanism of Y(III) and Zn(II) on W electrode in LiCl-KCl eutectic melts. Cyclic voltammogram and current reversal chronopotentiogram revealed that the electrochemical reaction of Y(III) on W electrode proceeds a single step mechanism of Y(III) to Y(0). On liquid Zn electrode, the deposition potential of Y(III) is more positive than that on W electrode due to the formation of Y-Zn solution and the reduction process was found to be a diffusion controlled and quasi-reversible at lower scan rate of 0.1 V/s. Based on the results of cyclic voltammometry, square wave voltammetry, and chronopoteniometry, the Y-Zn intermetallics could be formed by co-reduction process of Y(III) and Zn(II) on W electrode in LiCl-KCl-ZnCl₂-YCl₃ molten salts. Moreover, the electrochemical extracting metallic Y was conducted by galvanostatic and potentiostatic electrolysis on liquid Zn electrode. Electrolysis products consisted of Zn and YZn₁₂ phases characterized by scanning electron microscopy with energy dispersive spectrometry and X-ray diffraction. Meanwhile, the change of Y(III) concentration in LiCl-KCl eutectic melts was detected by inductive coupled plasma atomic emission spectrometer and the extraction efficiency could be estimated.     

Synthesis of á-aminonitrile through Anodic Cyanation of N-benzylpiperidine

Electrochemistry behaviors including linear sweep voltammetry and cyclic voltammetry of tertiary cyclic amines with different substituted group were studied. The effect of different substituted group of the nitrogen on the oxidation potential was analyzed. The most suited potential used in α-aminonitrile synthesis through potentiostatic anodic cyanation of cyclic teritary amines was found. The anodic cyanation of N-alkyl-substituted cyclic six-membered amines including N-benzylpiperidine and…     

ZnCl＿2－尿素熔体的电化学研究

研究了温度、浓度对ＺｎＣｌ２－尿素熔体电导的影响,ＺｎＣｌ２－ＮａＣｌ－尿素熔体的电导率（１２５℃）可达３０ｍｓ·ｃｍ－１以上．用循环伏安曲线、恒电位电解及断电后的电位－时间曲线,研究尿素熔体中Ｚｎ２＋的电还原和锌在钛、铜电极上的电沉积．Ｚｎ２＋的电还原为一步可逆过程,锌沉积在铜电极上会形成ＣｕＺｎ５合金．Ｚｎ２＋在熔体中扩散系数为１．３×１０－６ｃｍ２·ｓ－１（１２５℃）     

Electrochemical deposition and corrosion stability of Zn–Co alloys

Electrochemically deposited Zn–Co alloys under various deposition conditions were investigated using anodic linear sweep voltammetry for phase structure determination, scanning electron microscopy for surface morphology analysis, atomic absorption spectroscopy for determination of chemical composition, and polarization measurements and open circuit potential measurements for determination of corrosion properties. The influence of deposition current density, temperature, and composition of deposition solution on the phase structure and corrosion properties of Zn–Co alloys was studied. It was shown that the ratio of cobalt to zinc ions in the plating bath strongly affects the chemical content and phase structure, as well as corrosion stability, of Zn–Co alloys. Zn–Co alloys deposited from plating baths with the lowest and the highest ratios of cobalt and zinc ions exhibited the lowest corrosion rate.     

Comparative EIS study of a paste electrode containing zinc powder in neutral and near neutral solutions

The corrosion and passivation of Zn powder particles dispersed in a paste electrode immersed in 0.5 M Na₂SO₄ and 5×10^–3 M Na₂HPO₄ solutions were studied mainly by electrochemical impedance spectroscopy. The role played by diffusion in the mechanism of anodic oxidation of zinc powder particles has been shown. It was demonstrated that the anodic reactionof Zn powder in neutral or near neutral media involves at least two adsorbed intermediates. By simulating the porous structure of the electrode, some information about porous nature of zinc electrode could be extracted. Electronic Publication     

Relation between drug-induced taste disorder and chelating behavior with zinc ion; statistical approach to the drug-induced taste disorder, part II

There are many reports that the drug-induced taste disorder is ascribable to the chelate reaction of a drug with zinc ion and the following zinc deficiency. As a quantitative measure of the chelating ability of drugs with zinc ions, the chelating ability was estimated from the electrode potential change of the Zn2+/Zn(Hg) system during the addition of a drug. The electrode potential was measured in a water-N,N-dimethylformamide mixed solution and in an aqueous solution depending on the solubility of the drugs. The observed electrode potential change showed a positive correlation to the frequency of the drug-induced taste disorder that was supplied from the manufacturer of the original drug. The regression analysis was carried out assuming that the frequency of the taste disorder and the electrode potential change was linear. The F-values, p-values, and R2-values were 4.29, 0.13, 0.589, and 4.15, 0.13, 0.580, respectively. The positive correlation between the drug-induced taste disorder and the electrode potential change appeared evident if the uncertainty in the frequency of the taste disorder was taken into consideration. Thus the assumption of the zinc ion chelating mechanism on the drug-induced disorder was also evident except for cisplatin. The frequency of the drug-induced taste disorder of bezafibrate was estimated to be 0.4--0.5 from the regression analysis.     

Electrochemical Behaviour of Magnesium(II) on Ni Electrode inLiCl-KCl Eutectic

The electrochemical behaviour of magnesium(II) and the formation mechanism of Mg-Ni alloys on Ni electrode were studied in LiCl-KCl eutectic using various electrochemical techniques. Cyclic voltammogram and square-wave voltammogram revealed that under-potential deposition of magnesium occurred on Ni electrode because Mg-Ni alloy compounds were formed. The thermodynamic properties of the Mg-Ni intermetallics, Mg₂Ni and MgNi₂, were determined using open circuit chronopotentiometry in the temperature range of 818―893 K. Moreover, the Mg-Ni alloys were produced by potentiostatic and galvanostatic electrolysis under different conditions and characterized by means of scanning electron microscopy(SEM) equipped with energy dispersive spectrometry(EDS) and X-ray diffraction(XRD). The experimental results indicate that Mg-Ni intermetallic compounds can be selectively produced by potentiostatic electrolysis.     

电场作用下金属锌在薄液膜下的腐蚀电化学研究

采用薄液膜实验装置,测量了外加直流电场作用下锌在薄液膜体系中的腐蚀电位、阴极极化电流以及阴极极化曲线等. 研究了外加直流电场对锌在薄液膜下腐蚀行为的影响. 结果表明,外电场的作用可以使锌电极的腐蚀电位负移,也可以使锌电极在阴极极化条件下的阴极电流增加. 分析结果表明,外电场与薄液膜体系中锌电极电化学过程中的相关因素发生了协同作用,改变了锌电极的阴极过程.     

Properties of arsenic in molten potassium tetrachlorogallate at 300°C: Formation of gallium arsenide

Redox properties of As(III) species have been studied in molten KGaCl₄. The plot of equilibrium potential of As vs acidity is interpreted in terms of reaction AsCl⁴_? + 3 e = As + 4 Cl^?. X-Ray analysis of electrodeposits shows that only As is formed under potentiostatic conditions. Conversely, gallium arsenide is observed under galvanostatic conditions, for which the electrode potential becomes very negative.     

Dissolution of metallic uranium and its alloys

This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL). This revised version was published online in July 2006 with corrections to the Cover Date.