循环伏安法电沉积聚8-羟基喹啉–苯酚复合薄膜

采用循环伏安法在镀镍工件表面制备聚8-羟基喹啉–苯酚复合薄膜。研究了8-羟基喹啉和苯酚的浓度比、单体总浓度、氢氧化钠浓度、扫描速率和循环次数对复合薄膜耐蚀性的影响。分别采用盐水浸泡试验(时间1周)、三氯化铁缝隙试验、Tafel极化曲线法对比研究了聚8-羟基喹啉–苯酚复合薄膜、聚8-羟基喹啉薄膜和空白工件的耐蚀性。采用红外光谱仪、扫描电镜对所得复合薄膜的表面成分和形貌进行表征。电沉积复合膜的最佳工艺条件为:8-羟基喹啉和苯酚的浓度比1∶30,单体总浓度0.021 mol/L,Na OH浓度0.8 mol/L,扫描速率100 m V/s,循环次数6,室温。在最佳工艺条件下制备的聚8-羟基喹啉–苯酚复合薄膜的腐蚀电位、腐蚀速率分别为-0.277 0 V和4.54×10-4 g/(m2·h),耐蚀性优于聚8-羟基喹啉膜,远优于空白镀镍工件。     

A cyclic voltammetric study of ferrocyanide-thiocyanate silver electrodeposition electrolyte

The electrochemical behaviour of ferrocyanide-thiocyanate electrolytes for silver electrodeposition was studied by cyclic voltammetry. The differences in the electrolyte preparation procedure do not affect their electrochemical behaviour at identical silver concentrations. The silver electrodeposition is characterized by two cathodic current maxima and by charge transfer limitations with a preceding chemical reaction. The dissolution of the electrodeposited silver is characterized by the formation of AgCN on the electrode and further dissolution by passivation and formation of oxide products, which are reduced during the next cathodic scan. The redox processes of iron from the ferrocyanide complex on Pt- and Ag-substrates, as well as the effect of the complex forming agents like SCN^–- and CN^–- ions are shown.     

循环伏安法研究锌-钴合金的电沉积过程

采用循环伏安法研究了氯化物体系中锌-钴合金电镀的电沉积过程,采用X-射线厚度和成分分析仪测量了锌-钴合金镀层的厚度和钴金属质量分数.试验表明,在氯化钾锌-钴合金电镀槽液可以电镀钴质量分数为0.2%～0.4%的锌-钴合金,钴添加剂的加入,能够使氢的析出电位负移,扩大了锌-钴合金沉积的电位区间范围.     

电沉积Pt基二氧化铅电极的机理研究

研究了以Pt片为基体在Pb(Ⅱ)水溶液中,用电沉积方法制备PbO2电极的工艺,并通过循环伏安曲线测定了其沉积机理.实验发现:沉积PbO2电极要经过若干步骤,首先是Pb(Ⅱ)在本体溶液中的水合过程,之后水合离子被吸附在电极基体表面,然后这些水合离子先后被氧化为Pb(OH)2(ad) 、Pb(OOH)(ad) 等中间产物,最后这些产物脱水生成PbO2.     

镍钨合金电沉积伏安特性和初期行为的研究

镍钨合金镀层由于其高的硬度、耐磨及耐蚀性而被作为代铬镀层用于金属表面处理。为进一步探讨镍钨合金的电沉积机理,采用循环环伏安法和电位阶跃法研究了玻碳电极上镍钨电沉积的循环伏安特性和初期行为。电沉积过程中,钨酸根被还原成中间价态的氧化物。     

氨基磺酸盐-硫酸盐混合溶液中锌-锰合金的电沉积

本文研究了氨基磺酸盐-硫酸盐混合溶液中锌-锰合金的电沉积机理。实验结果显示,在低电流密度区获得哑光镀层,锰离子的催化析氢作用降低了合金沉积效率．玻璃化炭黑上的伏安试验显示锌沉积过程中的第一个电子转移较慢,阳极溶出伏安试验显示锌合金的异常共沉积导致富锌中间相的产生。     

Dissolution from electrodeposited copper–cobalt–copper sandwiches

The electrochemical behaviour of electrodeposited Co–Cu/Cu multilayers from citrate electrolytes was investigated using cyclic voltammetry and stripping techniques at a rotating ring disc electrode. Copper and cobalt–copper alloy sandwiches were deposited from an electrolyte containing 0.0125 M CuSO₄, 0.250 M CoSO₄ and 0.265 M trisodium citrate at two different pHs, 1.7 and 6.0. The Cu/Co–Cu/Cu sandwich is representative of a single layer in a Co–Cu/Cu multilayer deposit, which is known to exhibit unusual physical and magnetic properties. Results from cyclic voltammetry and detection of dissolving species at the ring showed that cobalt is stripped from a Cu/Co–Cu/Cu sandwich even when a copper layer as thick as 600 nm covers the Co–Cu alloy. Scanning electron microscopy showed that cobalt can dissolve from the deposit easily because the copper layer covering the Co–Cu alloy is porous. A separate series of experiments with Cu/Co–Ni–Cu/Cu sandwich showed that cobalt does not dissolve from these deposits because the addition of nickel stabilises cobalt in the Co–Ni–Cu alloy.     

Electrodeposition of Poly(3-hydroxyaniline) from Acidic Aqueous/Acetonitrile Solution

Electrodeposition of poly (3-hydroxyaniline) on platinum electrode from acidic/acetonitrile medium was carried out using cyclic voltammetry technique. The kinetic parameters were calculated by means of ex-situ microgravimetric and electrochemical data. The experimentally obtained kinetic equations were R_P,W = k_W [acid]^0.91 [monomer]^1.2 [electrolyte]^0.69 from microgravimetric data and R_P,E = k_E[acid]^0.92 [monomer]^0.96 [electrolyte]^0.7 from the values of the anodic current density using cyclic voltammetry technique. The apparent activation energy was calculated by the two techniques and is found to be 145.5 and 143.6 kJ/mol from microgravimetric and electrochemical data, respectively. The mechanism of the electrochemical polymerization reaction has been discussed and thermogravimetric analysis (TGA) is used to confirm the proposed structure and determination of the number of water molecules in the polymeric chain unit.     

A cyclic voltammetric study of the kinetics andmechanism of electrodeposition of manganese dioxide

The kinetics and mechanism of electrooxidation of Mn2+ ions to MnO2 (EMD) has been studied in electrolytes comprising MnSO4 and H2SO4 by cyclic voltammetry at 80°C. The voltammogram of a Pt electrode cycled between 0.6 and 1.6V vs SCE exhibits an anodic current peak at about 1.3V vs SCE resulting in the deposition of MnO2 on the electrode, while a cathodic peak appears at 0.8V vs SCE. It is shown that the pair of peaks do not correspond to a single reversible reaction but represent two separate irreversible electrode processes. The cyclic voltammetric peak current for the deposition of EMD is found to be proportional to the square root of Mn2+ ion concentration in the electrolyte and independent of acid concentration. Based on these results, a mechanism for the formation of EMD involving diffusion of Mn2+ ions to the electrode surface, oxidation of Mn2+surface to Mn3+ads, and H2O to OHads as the primary oxidation steps is invoked. Mn3+ads ions dissociate disproportionately into Mn2+ads and Mn4+ads ions at the electrode surface. The Mn2+ads and Mn4+ads ions, respectively, react with OHads and H2O resulting in the formation of EMD.     

Some aspects of removal of copper and cobalt from mixed ion dilute solutions

Some aspects of the electrodeposition of copper and cobalt from aqueous sulphate solutions containing low concentrations of their ions were studied with a view to heavy metal removal via an electrochemical process. Both metals were deposited on a vitreous carbon rotating disc electrode. Deposits formed under different conditions were studied employing linear sweep voltammetry, scanning electron microscopy and EDAX surface analysis. Constant potential electrolysis was used to simulate recovery in a laboratory batch reactor. Copper can be deposited without cobalt interference at potentials as cathodic as –1.0 V despite high Co concentrations. At more negative potentials, both metals are deposited simultaneously, although the copper proportion in the binary mixture is greater than that corresponding to the solution concentration ratio. Voltammetry studies effected under conditions in which codeposition occurs show only minor changes in copper behaviour. On the other hand, cobalt behaviour exhibits significant modifications. Even though formation of an intermetallic compound is possible, ASVL and microscopy tests indicate cobalt deposition in different crystalline forms as the more probable cause. In turn, cobalt deposition depends on the polarization conditions of the electrode and on the cobalt and copper concentrations.     

Cyclic voltammetric studies of pasted nickel hydroxide electrode microencapsulated by cobalt

Spherical nickel hydroxide microencapsulated by cobalt has been used as the electrochemically active material in pasted-type nickel electrodes of rechargeable alkaline batteries. Cobalt coating on the surface of nickel hydroxide particles can be converted to CoOOH during charge. Well distributed CoOOH forms the conductive network on the surface of nickel hydroxide particles, thereby leading to higher utilization of active material. Cyclic voltammetric studies suggest that nickel hydroxide microencapsulated by cobalt has better reversibility of the Ni(OH)2/NiOOH redox couple, greater discharge capacity and higher oxygen evolution overpotential than nickel hydroxide with added cobalt metal powder as a conductor. The mechanism of the electrode reaction is still found to be controlled by proton diffusion, and the proton diffusion coefficient is 1. 2×10–9cm2s–1.     

电沉积回收金技术的研究进展

用电沉积法直接提取氰化液中的金,是根据溶液中金氰络阴离子Au(CN)2-的沉积原理,在直流电场作用下,使金在阴极上析出。本文介绍了电沉积回收金技术的原理及研究现状,重点阐述了电沉积回收金技术的影响因素和存在的问题,其中,影响因素主要包括阴极材料、游离氰化物、pH、电流密度值以及其它因素对金回收的影响,存在的问题主要是电沉积过程中电流效率太低。     

铜/钴纳米多层膜的电化学制备及表征

纳米金属多层膜由于其巨磁电阻性能而受到人们的重视。采用双脉冲控电位技术在单晶硅上沉积铜／钴纳米多层膜。测量了电沉积过程中的阴极极化曲线及电流－时间曲线,确定了沉积电位;利用扫描电子显微技术及X射线衍射技术观察了沉积层的断面形貌及晶体结构。结果表明,沉积层结构清晰、连续,各子层厚度均匀。     

电沉积法制备钴超细微粒及其表征

用电沉积法制备超细钴粒子,考察反应物浓度、反应电流、反应时间、分散剂添加量等对样品粒径的影响。用XRD、XPS、TEM和激光粒度仪等进行表征。结果表明,所制备的超细钴粒子是平均粒径约500 nm的hcp相单质钴。在实验过程中,发现了外径200 nm,内径40~140 nm的钴环,长度为2μm,直径约75 nm的钴棒。     

Electrodeposition of cobalt from gluconate electrolyte

Cobalt electrodeposited onto steel substrate was carried out from solutions containing cobalt sulfate, boric acid and sodium gluconate. The study dealt with the influence of bath composition, current density, pH and temperature on the potentiodynamic cathodic polarization curves, cathodic current efficiency, and throwing power, as well as the throwing index of these baths. The microhardness of cobalt electrodeposited from gluconate baths is generally high and higher than that of cobalt deposited under similar conditions from sulfate, chloride, bromide and acetate baths. The surface morphology of the as-deposited cobalt was investigated using scanning electron microscopy (SEM) while the structure was studied using X-ray diffraction analysis. Cyclic voltammetric, as well as current-transient, techniques recorded on a glassy carbon electrode suggested that the deposition of cobalt from gluconate bath occurs via a nucleation process under charge transfer control.     

Structure of gold thin films grown on Ir(111)

We investigated the structures of the Au islands grown on Ir(111) using scanning tunneling microscopy (STM). We found that the Au islands have dendritic, triangularly compact, and irregularly compact shapes depending on the underlying layer and sample temperature, and that the island density at 100 K is much higher than that at 300 K. We also found that the first Au layer reveals a layer growth mode and that the growth becomes a multilayer mode from the second layer. The relation between the Au structures and chemical reactivity is discussed.     

Electrodeposition of Co + Ni alloys on modified silicon substrates

Cobalt+nickel alloys were electrodeposited on different base-silicon substrates since these alloys are interesting for several magnetic device applications. Acid chloride baths were used to obtain magnetic cobalt+nickel layers directly over silicon surfaces, tantalum silicide or metallic seed-layers. Although the initial stages of nucleation were influenced by the kind of substrate, in all substrates nucleation and three-dimensional growth evolving to compact, fine-grained and homogeneous deposition, took place. Preferential deposition of cobalt and anomalous codeposition occurred. Different compositions of the alloy were obtained, as is normal with a solid–solution formation. The cobalt content in the deposit rose with increase in both cobalt(ii) and saccharin concentrations and fell with decrease in the applied potential or current density.     

Direct voltammetric determination of gold nanoparticles using graphite-epoxy composite electrode

A new voltammetric method for a direct determination of gold nanoparticles, based on adsorption and electrochemical detection of colloidal gold, is described. In this protocol, the absorption of gold nanoparticles onto the rough surface of graphite-epoxy composite electrode is followed by their electrochemical oxidation in 0.1 M HCl medium at a potential of +1.25 V. The resulting tetrachloroaurate ions generated near the electrode surface are detected by differential pulse voltammetry (DPV). The DPV response is linear in the range from 4.7 × 10⁸ to 4.7 × 10¹¹ nanoparticles cm⁻³ with a limit of detection of 1.8 × 10⁸ gold nanoparticles cm⁻³. The surface characteristics of the composite electrode are investigated and the parameters that affect the complete analytical detection process of gold nanoparticles are optimized.     

在以EDTA和柠檬酸为配位剂的酸性硫代硫酸盐-亚硫酸盐镀液中电沉积金

以乙二胺四乙酸或柠檬酸作配位剂,在无氰的硫代硫酸盐–亚硫酸盐体系中研究了金在镀镍铜基底上的电沉积。在温度为60°C,pH为6和电流密度为2A/dm2的条件下,研究了不同配位剂对电流效率、镀速、镀层硬度及镀液分散能力的影响。最佳的镀液组成为0.5mol/L硫代硫酸钠–亚硫酸钠 0.2mol/L乙二胺四乙酸(或0.3mol/L柠檬酸)。该镀液具有良好的分散能力及高达98%的电流效率。采用扫描电镜、原子力显微镜及X射线衍射分析了镀态金镀层的表面形貌和晶体结构。所得的金镀层几乎无孔(孔隙率<2~4个/cm2),结合力良好,硬度适中(80~130HV)。     

纳米银修饰电极的制备

在圆柱形电解槽中,采用直流电沉积方法在导电玻璃上沉积银纳米材料,制备了Ag／ITO、Ag／CNTs／ITO复合电极,并以制得的复合电极作工作电极,测定两种电极在磷酸缓冲溶液中的循环伏安响应曲线。实验结果表明,纳米银修饰的电极具有很好的电化学活性。