碱性介质中吐温20对锌电极电化学行为的影响

解决锌电极的枝晶问题对延长电池使用寿命、资源综合利用和减少固体废物有积极作用.利用循环伏安法以及动电位扫描法考察了在1.0mol/dm3 KOH溶液中,TWEEN(吐温)20作为电解液添加剂时锌电极的电化学行为,结果表明:适宜浓度的吐温20能显著影响锌电极的电化学行为.吐温20对锌电极具有一定的缓蚀作用,其缓蚀作用主要是由于覆盖效应,吐温20在锌电极表面的吸附行为符合Freundlich等温式.适宜浓度的吐温20对锌电极的阴极过程有显著的抑制作用,可以有效减缓锌电极的枝晶形成和变形.     

Electrochemical Performance Improvement of AB5-type Metal Hydride Electrode by Adding KF in KOH Electrolyte

研究了在6mol/LKOH电解液中添加不同浓度KF对商用AB5-型贮氢合金的电化学性能的影响,研究发现合金的循环性能和循环后期的高倍率性能提高,通过XRD,SEM,SEI等分析表明,在电解液中添加KF生成的LaF3能显著提高合金耐腐蚀的能力,同时阻止合金电极在循环过程中析氢过电位降低,提高合金的动力学性能。     

强碱性介质铝阳极析氢影响因素研究

结合恒电流集气试验和表面分析手段研究了强碱性介质中影响铝阳极析氢作用的因素,分析了铝阳极的合金化、电解液浓度、工作温度和抑氢物质对材料析氢性能的影响.结果表明:4 mol/L KOH是综合性能较好的强碱性介质,并且选择稀土铝阳极,引入邻胺基苯酚抑氢剂,能够显著抑制铝阳极表面的析氢速率.     

电解液中添加Cu(OH)2对La2MgNi7.5Co1.5 贮氢合金电极电化学性能的影响

采用电子探针(EPMA)、X射线衍射(XRD)和电化学测试研究了在6 mol/L KOH电解液中添加Cu(OH)2对La2MgNi7.5Co1.5贮氢合金电极电化学性能的影响.结果表明,合金电极外表面上被镀上Cu膜,Cu膜的厚度和致密性随充放电循环次数的增加而增加,合金电极表面形成致密性Cu膜,可以有效地抑制电极内部贮氢合金的氧化,但对贮氢合金颗粒粉化的抑制作用不明显.在电解液中添加Cu(OH)2,增加了La2MgNi7.5Co1.5合金电极的活化次数,降低了该合金电极的高倍率放电性能,但对合金电极的最大电化学放电容量没有负面影响.此外,利用电沉积方法在电极表面镀Cu膜能够明显改善该合金电极的电化学循环稳定性.     

镍硫钴析氢电极的制备及性能研究

采用电沉积方法制备Ni-S-Co合金电极,通过正交实验和极化曲线测试研究了CoSO4·7H2O浓度、电流密度、电镀液温度、电沉积时间和电解液温度对Ni-S-Co电极析氢性能的影响.采用SEM,XRD和EDXA对镀层的形貌、结构和组成进行观察和分析.实验结果表明:制备具有最佳析氢活性的Ni-S-Co电极的工艺条件是25 ...     

席夫碱基季铵盐型双子表面活性剂对碱性锌电极电化学性能的影响

目的选择席夫碱基季铵盐型双子表面活性剂作为电解液添加剂,改善碱性锌电极的电化学性能,提高其耐蚀性能。方法通过电化学分析法,如失重法、塔菲尔极化曲线法、交流阻抗法等分析研究三种席夫碱基季铵盐型双子表面活性剂(D1、D2、D3)对锌电极电化学性能的影响,利用X射线光电子能谱(XPS)和扫描电子显微镜(SEM)研究在6 mol/L KOH电解液(饱和ZnO)浸泡48 h后,锌片表面的成分和形貌。结果室温下,缓蚀率随席夫碱基季铵盐型表面活性剂浓度升高而增加,当浓度进一步增大,缓蚀率变化不大。三种席夫碱基表面活性剂中,D3缓蚀能力最强,缓蚀率最高达95.67%,抑制腐蚀的效果顺序为:D3D2D1,属于抑制阳极型缓蚀剂。结论 D1、D2、D3作为碱性锌电极的电解液添加剂,可以有效减缓锌电极的腐蚀、变形、钝化及枝晶形成的能力,改善了碱性锌电极的电化学性能,D1、D2、D3适合作为碱性锌电池的缓蚀添加剂。     

Effects of Adding Cerium to Lithium on Properties of Lithium Anode

研究了在 30 ℃的 LiOH 碱性水溶液中,添加合金元素 Ce 对锂负极性能的影响。开路电位下的自腐蚀析氢速率及电化学测试结果表明,添加 Ce 对锂负极的析氢速率有明显的抑制作用。Ce 添加量为 0.08%(质量分数)时,对锂负极的缓蚀效率接近 83.3%。SEM观察表明,与纯锂负极相比,Li-Ce 合金负极放电后的表面膜更加致密少孔。XRD 分析表明,该表面膜里除了含有 LiOH 及 LiOH·H2O外,还有 Ce(OH)3存在,说明在碱性 LiOH 水溶液电解质中,Li-Ce 合金负极表面形成的 Ce(OH)3沉淀物在抑制自腐蚀析氢及影响放电电位方面起着关键作用。     

添加剂Pr2O3和Er2O3对电沉积Ni-S合金电极性能的影响

以氧化镨、氧化铒为添加剂,在泡沫镍基体上电沉积制备Ni-S镀层电极。对镀层的表面形貌、镀层结构、电沉积行为及镀层的电化学性能进行研究。结果表明：电镀液中添加稀土氧化物后电沉积过程的阴极极化增强,沉积层晶粒细化,比表面积增大,因而电极的析氢过电位降低;其中,添加Pr203的Ni-S镀层在250mA／cm2下碱性水电解时过电位降低达37mV,且该镀层电极在碱性介质下具有较高的析氢活性和耐腐蚀性能,在100h水电解实验中表现出较强的稳定性。     

电沉积工艺对镀锌层的表面形态及电化学性能的影响

采用电沉积技术制备几种电沉积式锌电极,考察镀液中KOH浓度和沉积电流密度对所制得镀锌层的微观形貌与性能的影响规律.结果表明镀锌层的枝晶随着KOH浓度(250～400 g/L)的增加而变得粗大,且其析氢量、腐蚀电位和腐蚀电流密度均呈现先减小而后增加的趋势;随着电流密度(25～100 mA/cm2)的增长,镀锌层由块状结晶向枝晶转变,相应地电极反应活性随之增大,而耐蚀性则随之变差,并发现沉积电流密度为75 mA/cm2时,锌电极的综合性能最好,以200 mA/g充放电循环10周次,其放电容量仍可达504 mA-h/g.解释了主要工艺参数对结晶形态及电极性能影响的原因,并说明适当的KOH浓度和沉积电流密度有利于提高电极的综合性能.     

不同钝化剂对锌铝混合粉的析氢抑制及无铬达克罗性能影响

研究了水杨酸、水杨醛及其复配对锌铝混合粉在pH 8.0的乙二醇丁醚水溶液中析氢的抑制作用,并对以二者为钝化剂的无铬达克罗涂料的稳定性和盐雾性能进行了考察.结果表明:水杨酸、水杨醛对铝粉析氢的抑制作用要好于对锌粉.二者都能较好的抑制混合粉的析氢量,其最佳浓度分别为10 g/L和2 g/L.复合配比的水杨酸和水杨醛对混合粉...     

Zum Elektrodenverhalten des Zinks und des Eisens in Calciumhydroxidlösung und in Mörtel

The electrode behaviour of zinc and iron in calcium hydroxide solutions and in mortar The behaviour of zinc (fine zinc and metallurgical zinc) and of unalloyed steel in a saturated calcium hydroxide solution and in mortar has been the subject of electrode-kinetic investigations. The observations showed that the behaviour of fine zinc, metallurgical zinc and galvanized steel is more or less identical, and that even the mortar coating has little effect on the electrode behaviour. It is found that

• (a) zinc is passivated by a zinc oxide layer;
• (b) the potential of a short-circuit cell consisting passive zinc and iron becomes so negative that hydrogen is developed at the iron at an appreciable rate;
• (c) the passivity Of the zinc in a solution containing chloride is removed at a much higher chloride concentration than that of steel.

In the case of a galvanized electrode with an electrolytically dissolved layer of pure zinc, the current/potential characteristic was similar to that of the passive iron.     

Untersuchungen über den Einfluß des Zinks auf das Korrosionsverhalten von Spannstählen

Investigations on the influence of zinc on the corrosion behavior of high strength steels Corrosion and fracture behavior of hot dip galvanized high strength steels with and without damaging zinc layer was studied in deionized water, in tap water, and in saturated calcium hydroxide solution through which nitrogen, air, and carbon dioxide were bubbled separately. Hydrogen permeation measurements have been carried out for steel specimens which were cathodically polarized by means of the zinc layer. It has been observed that the hydrogen activity reached to a maximum of 1-2 in neutral solutions and 4-10 in saturated calcium hydroxide solution or in dilute acid solutions containing carbon dioxide, before decreasing to low values. The decrease of hydrogen activity is due to the formation of surface layers. Constant load tests by application of a load amounting to 100-110% yield strength caused no hydrogen induced brittle fracture within 300-400 h neither with nor without damaging zinc layer. At a constant strain rate of 5· 10^?7/s only 8 mm cold drawn steel wires were found to be almost unsusceptible to hydrogen that was absorbed during the test. Under notched conditions, all the steels investigated showed macroscopic brittle fracture.     

Role of Thiamine Hydrochloride and Gelatin on the Electrodeposition of Zinc

A search for a non-cyanide zinc plating bath resulted on the development of a zinc acetate bath. To obtain bright zinc deposits, thiamine hydrochloride and gelatin were added. Hull cell studies revealed that in presence of 3 g dm^?3 thiamine hydrochloride a bright deposit was obtained at a current density above 2.5 A dm^?2. Addition of 3 g dm^?3 gelatin produced a bright yellow tinge deposit above 2.5 A dm^?2. Voltammetric studies carried out at a glassy carbon electrode in the plating solution revealed that in the pH range of 4.5-5.5, zinc acetate complexes underwent successive reduction to zinc. Acetate ions and pH affected both the dissolution and deposition of zinc. The dissolution of zinc took place with the participation of OH^? ions. Gelatin molecules adsorbed on the electrode surface. They favoured both zinc dissolution and deposition and prevented hydrogen evolution in the potential range of interest. Thiamine hydrochloride caused a reduction in zinc dissolution and deposition rates but favoured hydrogen evolution.     

A Rotating Ring-Disc Electrode Study of Zinc Electrodeposition from Zincate Solutions

The electrodeposition of zinc on iron/steel and the simultaneous evolution of hydrogen have been investigated using a rotating ring-disc electrode technique.

The effects of the hydrodynamic conditions, the concentration of ZnO and NaOH as well as the addition of commercially available organic additives were evaluated. The data were supplemented with the investigations of hydrogen permeation performed by the Devanathan-Stachurski bipolar electrode method.

It was found that the additives inhibited the electrodeposition of Zn and stimulated the hydrogen evolution from the cathode to the electrolyte. The hydrogen permeation in the iron substrate was suppressed in the presence of the additives in the electrolyte.     

Vapor Pressures of Zinc Over AgZn Alloys

The vapor pressure of zinc in equilibrium with solid β AgZn alloys has been measured by the dew-point method. The thermodynamic activities of silver, and the molar heats of formation have been calculated. Similar measurements have been made for the ternary alloys formed by adding gold to AgZn. An apparent particle size effect has been observed for AgZn filings. The vapor pressure of zinc over filings is 15 to 20 pct higher than over the solid alloys.     

INFLUENCE OF SURFACE-ACTIVE ELEMENTS ON FLUID FLOW OF MIG WELDPOOL

A mathematical model describing the behavior of metal inert gas (MIG) welding isformulated in the paper. By means of numerical simulation, the influence of surface-active elements on fluid flow of MIG weldpool is studied. The calculation resultsshow that by adding surface-active elements, the fluid flow behavior is drasticallychanged and the flow fluid flows from lower to upper in vertical direction at the rearof weldpool (w>0). The physical phenomenon is explained from the viewpoint of fluidflow behavior of weldpool that the properties of weld metal is greatly improved andthe content of diffused hydrogen is reduced, thus providing a basis for developing newwelding materials.     

The Corrosion Behavior of Cold Sprayed Zinc Coatings on Mild Steel Substrate

Zinc and its alloy coatings have been used extensively for the cathodic protection of steel. Zinc coating corrodes in preference to the steel substrate due to its negative corrosion potential. Numerous studies have been conducted on the corrosion behavior of zinc and its alloy coatings deposited using several techniques viz., hot dip galvanizing, electrodeposition, metalizing or thermal spray etc. Cold spray is an emerging low temperature variant of thermal spray family which enables deposition of thick, dense, and pure coatings at a rapid rate with an added advantage of on-site coating of steel structures. In the present study, the corrosion characteristics of cold sprayed zinc coatings have been investigated for the first time. In addition, the influence of heat treatment of zinc coating at a temperature of 150 °C on its corrosion behavior has also been addressed.     

Development of peeling tool for micro-EDM

We propose a simple and fast fabricating method of tool electrode for micro-EDM. A ‘peeling tool’, a wire coated with a different material, has been developed as an interim product for a microelectrode. A zinc layer was coated by electroplating on a tungsten electrode of 100 μm diameter. The zinc layer makes both handling and chucking of the electrode easy. Part of the zinc layer is instantly ‘peeled’ by a single discharge, exposing tungsten electrode under the zinc layer undamaged and the exposed electrode can be used in microhole drilling by EDM. Time-resolved imaging revealed the peeling process dynamically.