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（广州 黄清安教授）贵刊2006年第4期第5页刊登了印仁和教授等人的文章《Zn-Ni合金共沉积影响机理的拉曼光谱研究》一文，让人耳目一新，有一些实验结果是有说服力的。文章最后得出这样的结论：证明了Zn-Ni合金共沉积中存在着较易在电极表面放电的NiClad，所以使Ni沉积的过电位降低，促进了Ni的沉积，导致Zn的异常共沉积。     

电沉积制备Zn-Ni合金及其耐蚀性的研究

研究了镀液组分对Zn-Ni合金的电沉积过程、成分、耐蚀性和表面形貌的影响。研究表明:电沉积Zn-Ni合金属于一种典型的异常共沉积现象。镀液中的Zn2+会阻碍Ni 2+的放电过程,使得合金中Ni的质量分数降低。通过增加镀液中Ni 2+的浓度,可以有效增大Zn-Ni合金中Ni的质量分数。含Ni 17%的Zn-Ni合金具有最佳的耐蚀性。合金中Ni的质量分数的增大,有利于细化颗粒,降低表面粗糙度。     

氨基磺酸体系Co-Ni合金电化学共沉积行为及动力学机理

通过稳态阴极极化和电化学交流阻抗(EIS)等方法,研究了在不同钴镍金属离子比例的氨基磺酸电解液中,Co-Ni合金的电化学共沉积行为。结果表明在氨基磺酸体系中,导致Co-Ni合金异常共沉积行为的原因和在硫酸盐,或氯化物体系中的不同。不是由于Co^2 抑制了Ni的沉积,而是由于NH2SO3^-作为双齿配体形成的异核络合物在电极表面吸附,阻滞了镍离子的还原过程。并且以晶体场理论为基础解释了Co^2 和NH2SO3^-形成的高自旋络合物,比Ni^2 所形成的络合物具有较高的晶体场稳定化能(CFSE),容易分解。因此吸附在电极表面的氨基磺酸根离子对Co2^2 沉积的阻滞作用小于对Ni2^ 的。这样就导致了在氨基磺酸电解液体系中Co^2 的优先沉积。阳极线性扫描曲线表明．钴镍合金中镍含量越高,沉积层在热力学上越稳定,耐蚀性也越好。同时通过EIS的测试,利用等效电路的分析方法和交流阻抗谱解析理论,提出了氨基磺酸电解液中Co-Ni合金共沉积的动力学机理,较好地解释了实验结果。     

Al_2O_3陶瓷表面化学气相沉积Ni涂层及其与Cu润湿性

将NiCl2·6H2O经过脱水干燥后得到的NiCl2粉末作为原料,采用化学气相沉积技术通过H2还原反应,在Al2O3陶瓷表面沉积了Ni涂层。研究了涂层的相组成、涂层与Al2O3陶瓷结合力和涂层与铜熔液间的润湿行为。结果表明:制备的涂层中的主要组分为Ni,Ni涂层均匀、致密,厚度可达40μm,且涂层与陶瓷之间的结合良好。座滴法测得沉积Ni涂层的Al2O3陶瓷与Cu之间的润湿角为30.15°,表明涂层明显改善了陶瓷与金属间的润湿性。     

碱性锌-镍合金电镀述评

介绍了电镀Zn-Ni合金镀液的类型和各自的优缺点。重点报道了碱性Zn-Ni合金电镀液的主要成分及其工艺配方。详细地总结了碱性Zn-Ni合金镀液中所用的配体和光亮剂的类型。评述了它们的作用。扼要地讨论了Zn-Ni合金共沉积时光亮剂的光亮机制以及锌与镍共沉积的机理。     

电沉积Ni-Cr合金的研究现状与发展

综述了Ni–Cr合金电沉积研究的发展过程和不同类型电镀液的特性,分析了三价铬电镀体系中Ni–Cr合金共沉积的影响因素(包括主盐、添加剂、电流密度、温度和pH),指出了目前存在的问题,给出了相关的解决方法。     

温度对电沉积氢氧化镍电化学性能的影响

在0.1mol/L的Ni(NO3)2溶液中,采用电化学沉积法制备出适用于锌镍微电池的氢氧化镍电极,研究了电沉积温度对Ni(OH)2电极的电化学循环伏安性能以及充放电性能的影响。测试结果表明,电沉积方法制备的Ni(OH)2电极适合于微电池的制作。30°C下电沉积制备的Ni(OH)2电极具有优异的电化学性能,其质子扩散系数为7.71×10-12cm2/s,放电比容量为1285μAh/cm2,利用率达91.4%。     

电镀镍—二硫化钼复合电催化电极的研究

本文报道了 MoS_2与 Ni 共同电沉积形成复合镀层及 Ni—MoS_2复合镀层对氢在碱溶液中电解析出影响研究,结果表明,在普通镀镍溶液中,MoS_2与Ni 共同沉积的机理是非静电的,Ni—MoS_2复合电极对氢在30%KOH 溶液中析出的催化活性比纯镍电极的高得多,而且其催化活性随复合电极中MoS_2含量的增加而提高。由于 MoS_2 微粒弥散在Ni 基质中,镀层表面结构的改变及两种催化剂的联合作用造成 Ni—MoS_2复合电极对氢析出反应比纯 Ni 有更高的催化活性。     

氯化胆碱-丙二酸离子液体电沉积锌-镍合金

采用恒电位法在氯化胆碱-丙二酸类离子液体中电沉积制备了Zn-Ni合金镀层.重点研究了沉积电位对Zn-Ni合金镀层孔隙率、耐蚀性、结合力和表面形貌的影响.结果表明,在-1.2 V下电沉积所得Zn-Ni合金镀层的孔隙率较低,表面平整致密,耐蚀性最好.     

纳米二氧化硅对镍电沉积影响及在复合镀层中的化学键合状态

用线性扫描伏安法和电位阶跃法研究了n-SiO2／Ni复合电刷镀体系的电化学响应，探讨了纳米颗粒的影响；用X射线光电子谱研究了复合镀层中n-SiO2／Ni颗粒表面与基质金属间的相互作用，结果表明纳米颗粒使金属沉积过电位显著降低，电流效率、金属成核率及晶体生长速度增加，纳米颗粒对金属镍电结晶有明显的催化效应；n-SiO2／Ni表面氧的不饱和化学键与表面扩散过程中吸附态金属Ni原子键合形成Ni—O键，纳米颗粒与基质镍以化学键方式结合。     

ZnFe anomalous electrodeposition:: stationaries and local pH measurements

The kinetics of ZnFe codeposition was investigated in acid solutions. The effects of solution composition and pH were analyzed. Inhibition of H⁺ reduction and Fe deposition occurs with increasing Zn⁺⁺ concentration in sulfate solution. An activation of Zn deposition is also observed. Increasing pH causes Zn deposition activation during ZnFe codeposition. The anomalous codeposition is also favored in chloride medium. When alloy deposition becomes the main process, the interfacial pH is governed by the individual metal deposition that controls the kinetic behavior. The interfacial pH increases during separate Fe deposition, meaning that it occurs with simultaneous consumption of H⁺. Individual Zn deposition brings about an H⁺ inhibition. A correlation between the codeposition behavior of ZnFe and ZnNi in sulfate and chloride solutions suggests that the prevailing cathodic reaction governs the interfacial pH. Anomalous codeposition process does not seem to be associated with a saturation of any thermodynamic species at the electrode surface. It can only be described by kinetic arguments.     

Electroless plating of rhenium–nickel alloys

In this study, rhenium–nickel (Re–Ni) films were formed by electroless deposition on conductive (Cu) and non-conductive (SiO₂) substrates. Different bath compositions were evaluated, aiming to achieve high Re-content. Both sodium hypophosphite and dimethylamine-borane were used as reducing agents. Films containing up to 75 at% Re were obtained. The influence of nickel concentration in the solution on alloy composition, deposition rate and surface morphology were determined. It is shown that Ni²⁺ acts as a catalyst for the in situ reduction of the perrhenate ion, in a manner similar to what was proposed for electroplating of the same alloy. The rate of electroless plating is similar to that found in electroplating at an applied current density of 50 mA cm⁻². While pure Re cannot be deposited from our electroless plating baths, the addition of even a very small amount of Ni²⁺ ions (0.25 mM) is enough to start the induced codeposition of Re. Proper selection of the bath composition can lead to fine control of the alloy thickness and its Re-content, thus making it potentially attractive for thin barrier layers.     

Anomalous codeposition of Co–Ni: alloys from gluconate baths

Thin films of cobalt–nickel alloys were galvanostatically deposited onto steel substrates from gluconate baths. Cathodic polarization curves were determined for the parent metals and Co–Ni alloy. The effects of bath composition, current density and temperature on cathodic current efficiency (CCE) and alloy composition were studied. The deposition of Co–Ni alloy is of anomalous type, in which the less noble metal (Co) is preferentially deposited. The CCE of codeposition is high and increases with increase in temperature and current density, but it decreases as the [Co²⁺]/[Ni²⁺] ratio in the bath increases. The percentage of Co in the deposit increases with increasing cathodic current density, temperature and increasing Co²⁺ ion concentration. The structure and surface morphology of the deposit were studied by XRD, ALSV and SEM. The results showed that the alloys consisted of a single solid solution phase with a hexagonal close packed structure.     

Electrochemical investigation of the codeposition of SiC and SiO2 particles with nickel

The use of electrochemical impedance spectroscopy (EIS) for the in situ control of the electrolytic codeposition of Ni/SiO₂ and Ni/SiC was investigated. An attempt was made to clarify why silica particles hardly codeposit in comparison to silicon carbide particles. It was found that the presence of SiO₂ and SiC particles influences the metal deposition process in different ways. SiC particles that are being embedded in the growing metal layer cause an apparent decrease in the electrode surface area, probably due to blocking off a part of the surface by partly engulfed particles. In the case of SiO₂ particles, which embed in the metal matrix to a very limited extent, no blocking was observed. It was found that the presence of particles in the solution causes an apparent increase in the electrode surface area, probably due to increased surface roughness.     

Electrochemical deposition of zinc–polystyrene composites in the presence of surfactants

The electrochemical codeposition of polystyrene particles and zinc on a rotating cylinder electrode was investigated. Rheological measurements indicate strong aggregation of the PS particles in the zinc deposition electrolyte. Addition of cetylpyridinium chloride, a cationic surfactant, prevents aggregation and enhances polystyrene codeposition. Other surfactants also increase suspension stability, but diminish polystyrene codeposition, irrespective of their charge. Hence, the surfactant charge does not affect polystyrene codeposition. The variation of polystyrene incorporation with the amount of suspended polystyrene, current density and electrode rotation speed signifies that polystyrene codeposition with zinc is determined by the competition between particle removal forces and particle adhesion forces at the cathode surface. The effect of the surfactants can be related to changes in surface roughness of zinc due to surfactant adsorbed on the electrode. Cetylpyridinium chloride behaves differently from the other surfactants, because it is reduced at the cathode.     

A parallel plate flow cell for the investigation of the role of surfactants in the codeposition of polymer particles in nickel electroplating

A parallel plate flow cell was designed for the study of particle codeposition in metal electrodeposition. Particle deposition was visualized and recorded with a microscope/video assembly. The effects of two surfactants (anionic sodium dodecyl sulphate and cationic cetyl trimethyl ammonium bromide) on the adhesion of anionic polystyrene particles to a nickel substrate were examined. The deposition rate in laminar flow was measured as a function of the main parameters, that is, electrode potential, Ni(ii) concentration, surfactant concentration and pH. The hydrodynamic drag force applies uniformly and tangentially to the collector under laminar flow in contrast with rotating disc or impinging jet cells. No deposition is observed unless specific attractive forces carry the particles through the boundary layer. Particle attachment takes place over a limited range of surfactant/Ni(II) composition and correlates with the formation of a surface film visible under the microscope. Results discussed are based on the adsorption of SDS and CTAB on to both the electrode and the particles, an adsorption which significantly alters the interaction potential at a short distance. The cell gives interesting evidence for the occurrence of specific interactions in electrolytic codeposition. It also proves useful for observing other phenomena, such as hydrogen bubbling.     

Electrodeposition of CoNiMo thin films using glycine as additive: anomalous and induced codeposition

The present study focuses on the behavior of the CoNiMo mixed anomalous/induced codeposition process, using glycine as a probe to influence the coverage of adsorbed intermediates. In order to facilitate the investigation of a wide variation of parameters the electrodeposition of the alloy films was performed using a rotating cylinder Hull cell. Alloy composition, current efficiency and partial currents of each metal were analyzed. The partial current densities and hence alloy composition was affected by the amount of glycine in the electrolyte: increasing glycine enhanced both cobalt and molybdenum deposition rates and hindered nickel deposition. It is suggested that the glycine facilitates the adsorption of M(I) adsorbed intermediates that control the anomalous and induced codeposition behavior. The current efficiency ranged from 30 up to 75% and was only slightly affected by glycine at high applied current densities. Films with a tridimensional porous structure were obtained applying current densities higher than 200 mA cm⁻², formed as a consequence of the large hydrogen evolution side reaction, presenting conditions for a novel Mo-alloy electrode structure.     

Detection and characterization of molybdenum oxides formed during the initial stages of cobalt–molybdenum electrodeposition

The initial stages of cobalt–molybdenum electrodeposition on a vitreous carbon electrode were studied to obtain information about the mechanism of cobalt–molybdenum induced codeposition. Solutions containing cobalt sulphate, sodium molybdate and sodium citrate at pH 6.6 were used. A first step in the mechanism of alloy deposition is proposed. This step takes into account the formation of molybdenum(IV) oxides over which Co–Mo alloy may be only deposited if sufficient potential is applied. Co–Mo electrodeposition occurs through an early stage involving low reduction current, related to the formation of molybdenum oxides, followed by a later stage in which the reduction current suddenly increases, corresponding to alloy codeposition. When a low potential is applied, a continuous coloured molybdenum oxide film is formed on the electrode and Co–Mo is not deposited. To induce the alloy deposition on the oxide film it is necessary to apply more negative potentials than a threshold value, which depends on the composition of the electrolytic bath. By increasing molybdate concentration in solution, the threshold potential shifts to more negative values. Intermediate molybdenum oxides were characterized using scanning electron microscopy (SEM), compositional analysis, Raman measurements and Auger and X-ray photoelectron spectroscopies.     

Electrochemical study of codeposition of Al particle—Nanocrystalline Ni/Cu composite coatings

Nanocrystalline Ni/Cu alloy matrix-Al metal particle composite coatings have been successfully developed via sediment codeposition (SCD) method. As high as 29 vol.% Al particles could be incorporated in the nanocrystalline Ni/Cu alloy matrix which has an average grain size of 16 nm. Adding conductive Al particles in the electrolyte shifted polarization curves to more negative potentials, which is a characteristic of electro-codeposition of nonconductive particles. The codeposition behavior has also been found to be consistent with the Guglielmi's model that was proposed for predicting the codeposition of nonconductive particles in metal matrix.