Bright Nickel and Levelling Power

In the course of our researches we have studied the cathodic phenomena which lead to blight deposits from nickel baths. The action of organic brighteners has been considered as due to the possibility of some functional groups in the organic molecule interacting with free orbitals of the nickel ions, thus minimizing the size of crystalline growth centres in the process of electrodeposition. Neutralisation of these functional groups is almost always followed by the disappearance of the brightening action as has been shown with N—alkyl substituted saccharin.

The fully brightening action of some amine oxides shows, however, that the possibility cannot be excluded that cathodic reduction of the addition agent may play an important part in the cathodic deposition process.

For the purpose of studying the levelling power of solutions giving bright deposits we have developed a metallographic method which makes use of a particular micro-profile of pseudosinusoidal shape. By plotting graphically the amplitude of tile pseudosinusoidal deposit versus its thickness on the peaks of the profile it is possible to effect a quite definite comparison between the levelling power of various electrolytes containing different organic addition agents.

Experimental considerations lead to the conclusion that levelling action may he the result of a differential adsorption of addition agents in the diffusion layer on the cathode surface. This fact may cause a differential inhibition which would then favour a faster deposition in the valleys than on the peaks of the profile.     

Metal microdistribution in electroless copper plating

It is shown that a copper electroless plating solution without addition agents produces either positive or negative levelling depending on the pH. The positive levelling power increases with the temperature, solution agitation and pH value and decreases with an increase in bath loading. A mechanism of levelling action based on the electrochemical nature of an electroless copper plating reaction is proposed.     

Proceedings at an Ordinary Meeting held on Wednesday, 13th May, 1931, at the Northampton Polytechnic Institute,London

Levelling power, defined as a function of the deposit thickness obtained at the peaks and recesses of a standard rough surface, has been measured in nickel plating solutions. The effects on levelling power and cathode potential of variations in current density and in the concentration of a variety of addition agents have been examined. Cathode efficiency has been determined and the distribution of incorporated addition agents investigated under selected levelling conditions.

The results support the view that levelling is due to variations in cathode potential between peaks and recesses of a rough surface brought about by differences in the rate of diffusion of addition agent to these points once a diffusion layer has been established. An equation has been derived permitting the calculation of levelling power in terms of current density, addition agent concentration and the rates of change of cathode potential with these two factors. Plots of calculated levelling power against concentration for coumarin, thiourea, and saccharin show many points of resemblance to the corresponding experimental curves.

Some conclusions of practical importance are listed.     

A Study of Benzotriazole as an Addition Agent for Acid Copper Sulphate Solutions

During a study of addition agents for acid copper sulphate solution, it has been shown that benzotriazole forms an insoluble cuprous complex which codeposits with the copper^1a A method has been devised for dissolving the deposit and separating the addition agent and it has been deffionstrated that benzotriazole can be recovered from the electrodeposit in the undecomposed form.² Since benzotriazole can be separated and estimated with accuracy, it provides a compound which is eminently suitable for studying addition agent action during electrodeposition. Polarization studies have shown that benzotriazole markedly increases the activation overpotential of the cathode η_A—mainly by decreasing the active area of the surface by film formation—and it is possible to detect 10^?7 M benzotriazole from its effect on the cathode overpotential. Additions of 0·012 g/1 benzotriazole give very fine grained deposits of copper and prevent epitaxy, while higher concentrations (0·12 g/1) result in fully-bright deposits with a banded structure. The effect of plating variables on the amount of benzotriazole included in copper deposits has been studied as a necessary prerequisite for suggesting a mechanism of addition agent action which, in this particular system, has been based on the formation of metal complexes.     

Interferometric investigations of the diffusion behaviour of metal ions during levelling. Part II

Accurate interferometric measurements were carried out of the concentration change in Cu²⁺ in the electrolyte layer adjacent to a microprofiled cathode in combination with the simultaneous investigation of the degree of levelling during the plating of bright copper (by applying a new method in a two-dimensional glass cell to eliminate natural convection). The hydrodynamic conditions and the concentration of the levelling additive were changed during the measurements. The observed direct effect of the levelling additive on the diffusion behaviour of Cu²⁺ (in terms of the diffusion coefficient and the thickness of the Nernst diffusion layer) is an important characteristic of the electrochemical levelling mechanism during plating from similar electrolytes.     

Supporting group interaction among humans and autonomous agents

An important aspect of interaction among groups of humans and software agents is supporting collaboration among these heterogeneous agents while they operate remotely and communicate asynchronously. We are developing an architecture that supports multiple humans interacting with multiple automated control agents in such a manner. We are evaluating this architecture with a group consisting of the crew of a space-based vehicle and the automated software agents controlling the vehicle systems. Such agent interaction is modelled as a loosely co-ordinated group because this model minimizes agent commitment to group goals and constraints while addressing a significant portion of crew and control agent group behaviours. In this paper, we give background on human interaction with space-based automation. We identify related research in multi-agent autonomous architectures and single agent human-computer interaction systems, we describe our architecture design for human-software agent groups and we identify research issues in loosely co-ordinated human-software groups.     

The mechanism of the action of inorganic inhibitors

Abstract

The studies on the inhibition of the corrosion of iron and steel made in the Oak Ridge National Laboratory originated in the discovery of the inhibitory action of the pertechnetate ion, TcO₄^-. The properties of technetium compounds relevant to inhibition are presented, together with an outline of the hypothesis of electrostatic polarisation by the XO^4n- ions which led to the discovery.

Results of several studies related to mechanism are given. These demonstrated the extreme effectiveness of the pertechnetate ion, in comparison with other inhibiting anions, even in the absence of oxygen or other oxidising agents. It was shown that TcO₄^-, CrO₄^2- and MnO₄^- all exert an effect on the metal that does not depend upon reduction of the inhibitor. The result of this action is that the metal may be passivated anodically by much lower current densities than are requisite in non-inhibiting electrolytes, and with passage of no more charge than is necessary to form the passive film.

The nature of the interface between metal and electrolyte in both active and passive conditions is briefly discussed in relation to the alternative reaction paths which lead to active dissolution or to passivation, respectively. The various ways in which the inhibitor may enter into these processes are presented from the point of view of electrode kinetics, as modified by the specific interactions in which the structure of the inhibitor may playa part. In effect, the inhibitor reduces the ‘activity’ of the metal, as represented by its exchange current, so that it is then capable of being passivated as easily as a stainless alloy.     

Bright Metal Surfaces and a Theory of Bright Plating

The nature of bright metal surfaces and the methods available for their production are discussed. It is shown that the production of a bright surface (other than by mechanical working or by rupture at cleavage planes) involves the deposition or removal of surface atoms in a random manner.

Methods by which random electrodeposition of atoms giving bright plating can be achieved are discussed. A detailed mechanism of the action of addition agents is described, in which it is suggested that two main categories of such agents can be distinguished.

Suggestions for practical advances based on the general theory are made.     

Inhibitive action of dibenzylsulphoxide and dibenzylsulphide

Abstract

The inhibitive action of dibenzylsulphoxideand dibenzylsulphide on iron in 1 N-HCl has been studied. Anodic and cathodic polarisation curves have been obtained through a stepwisemethod. Adsorption of the inhibitors at the electrode has been measured, as a function of the time and the potential, by using ³⁵S-labelledsubstances. The dibenzylsulphidewas shown to be preferentially adsorbed in comparison with dibenzylsulphoxide,reaching a saturation condition. The inhibitor efficiencyof dibenzylsulphide is higher than that of dibenzylsulphoxide. A comparison of results supports the hypothesis that dibenzylsulphoxideacts as a secondary inhibitor.     

A Study of the Theory Involved in the Deposition of Chromium

Reaction products of aldehydes and amines have been shown to be capable of acting as brightening agents in the electrodeposition of tin from acid solutions. A reproducible method of preparing a stable brightening agent from o-toluidine and acetaldchyde has been devised and the use of this agent in a stannous sulphate electrolyte containing cresolsulphonic acid and sodium n-octyl sulphate has been developed. The plating bath, after working in, gives fully bright, ductile deposits at current densities of 10 A/ft² upwards with slow cathode movement.     

Aminoacetic acid as complexing agent in baths for electroless deposition of Ni–W–P coatings

Abstract

Ni–W–P alloy coatings were deposited from a bath containing, nickel sulphate (VI), sodium tungstate (VI), sodium hypophosphite, sodium formate, and a complexing agent. The complexing agents were formic acid, acetic acid, lactic acid, succinic acid, malic acid, malonic acid, aminoacetic acid and triethanoloamine. It is shown that Ni–W–P coatings are deposited the slowest when complexing agents with the highest stability constants are used. As the deposition rate increases, i.e. in the presence of less stable complexing compounds, the amount of tungsten in the coating decreases. When aminoacetic acid and citric acid were used, the tungsten content in the coating amounted to ～2 wt-%, depending on the complexing agent concentration and the pH of the bath.     

弹性极限曲率在中厚板辊式矫直过程中的作用

针对某中板厂十一辊矫直机矫直板材翘曲问题,采用弹塑性差分的曲率积分方法,分析弹性极限曲率对矫直后板材不平度的影响规律。研究发现,弹性极限曲率可以作为判断板形问题的标准。初始曲率不是影响矫直能力的主要因素,可以用弹性极限曲率计算矫直力来判断其是否超过矫直能力。     

水溶液体系中制备纳米银线的研究

在水溶液体系中,以蔗糖为还原剂、NaCl为前驱体络合剂、PVP为表面活性剂,通过水热反应制备得到了直径大约为40 nm,线径分布均匀、分散性良好的纳米银线。有效解决了目前多元醇有机体系下制备纳米银线洗涤困难,反应条件苛刻,后处理繁琐等问题。系统研究了还原剂用量、还原剂种类、Cl^-/Ag⁺摩尔比、卤化物种类和表面活性剂种类对于产物形貌的影响。结果表明,当还原剂蔗糖的用量为0.18 g,PVP的相对分子质量为58000,选择Na Cl作为络合剂,且Cl^-/Ag⁺摩尔比控制在1.26时,制备的纳米银线形貌均一,纯度较高,纳米线长径比大于1000。     

用苦瓜提取液还原制备纳米银的研究

分别以中国种和印度种苦瓜的提取液为还原剂、硝酸银为前驱体制备纳米银颗粒,并采用紫外可见光谱(UV-Vis)、红外光谱(FTIR)、X射线衍射(XRD)、和透射电镜(TEM)进行表征。结果表明,当硝酸银浓度为10 mmol/L时,制备得到平均粒径最小为8.72和7.46 nm的球形纳米银颗粒。制备反应机理为类黄酮作为还原剂,通过失去H⁺由烯醇结构变为醌型结构来还原Ag⁺获得Ag⁰,蛋白质及其它三萜类化合物起保护剂作用。苦瓜提取液种类对纳米银的粒径、形貌、分散性及均匀性等总体影响不大。     

The role played by hydrodynamics in the levelling process during bright copper platting from acidic electrolytes. Part I

A new direct method has been developed for investigating the kinetics of levelling in a specially designed glass cell. The method was used to study the levelling mechanism during bright copper plating in acidic electrolytes. The role played by one of the important practical factors (the hydrodynamic conditions) is evaluated. It is shown that the velocity of circulation and the flow pattern of the electrolyte with respect to the cathode surface exert a substantial influence in establishing an optimum regime leading to the deposition of levelled coatings. By a suitable combination of the new method and a microspectrophotometric technique, the distribution of the levelling additive in the electrolyte layer adjacent to the microprofiled cathode was determined as a function of the hydrodynamic conditions. The results of this new approach confirm the adsorption-diffusion mechanism of electrochemical levelling.     

还原剂与表面活性剂的覆盖效应在纳米片状银合成中的作用(英文)

研究还原剂与表面活性剂对于片状银形成的影响,考虑了两种弱还原剂:柠檬酸三钠、酒石酸钾,以及3种常用表面活性剂:聚乙烯吡咯烷酮、十二烷基磺酸钠、阿拉伯胶的影响。结果表明,以上弱还原剂与表面活性剂均具有可以与纳米银(111)面紧密结合的活性基团,从而产生覆盖效应阻止该晶面生长,最终达到形成片状银的目的。结果还显示,卤素离子的熟化作用在片状银生长过程中也存在一定的影响。     

Diagnostic experimental results on the hydrogen embrittlement of austenitic steels

Three main available hypotheses of hydrogen embrittlement are analysed in relation to austenitic steels based on the studies of the hydrogen effect on the interatomic bonds, phase transformations and microplastic behaviour. It is shown that hydrogen increases the concentration of free electrons, i.e. enhances the metallic character of atomic interactions, although such a decrease in the interatomic bonding cannot be a reason for brittleness and rather assists an increased plasticity. The hypothesis of the critical role of the hydrogen-induced ϵ martensite was tested in the experiment with the hydrogen-charged Si-containing austenitic steel. Both the fraction of the ϵ martensite and resistance to hydrogen embrittlement were increased due to Si alloying, which is at variance with the pseudo-hydride hypothesis. The hydrogen-caused early start of the microplastic deformation and an increased mobility of dislocations, which are usually not observed in the common mechanical tests, are revealed by the measurements of the strain-dependent internal friction, which is consistent with the hypothesis of the hydrogen-enhanced localised plasticity. An influence of alloying elements on the enthalpy E_H of hydrogen migration in austenitic steels is studied using the temperature-dependent internal friction and a correlation is found between the values of E_H and hydrogen-caused decrease in plasticity. A mechanism for the transition from the hydrogen-caused microplasticity to the apparent macrobrittle fracture is proposed based on the similarity of the fracture of hydrogenated austenitic steels to that of high nitrogen steels.     

The use of contrast agents to enhance crack detection via neutron radiography

Contrast agents have been used in a wide variety of neutron radiographic and radioscopic examinations. Useful contrast agents range from simple hydrogenous materials such as water and oil to exotic compounds such as gadolinium chelates. The properties of the contrast agents also vary widely. Considerations such as the ability to penetrate into cracks, the ability to be removed, the neutron cross-section, or the neutron attenuation mechanism, often steer the investigator to select a particular contrast agent. We have quantified the behavior of the following substances as contrast agents: an aqueous liquid penetrant, a solvent-based liquid penetrant, water, a GdCl₃ aqueous solution, and a solution of gadolinium β-diketonate (2,2,6,6-tetramethyl-3,5-heptanedione) (TMHD) dissolved in acetone and methylene chloride. The experimental tests were carried out using wedge-shaped gaps that simulated cracks, and in actual cracks in Inconel tubing. The experimental results showed that an aqueous solution of GdCl₃ used with a wetting agent provided the best performance, but was difficult to remove completely from the crack.     

Development of an analytical 3D-simulation model of the levelling process

Sheet metal often shows shape defects, which is not complying with the increasing requirements for the quality of the products needed to satisfy the highest demands on finer tolerances. Due to the market's high requirements on the quality of products, new high-technology levelling machines were developed. The adjustment of these levellers is very complicated and a successful adjustment depends mainly on the experience of the line operator. As the computational power has developed over the past years, simulation becomes more important in the production process and is used in analysing the effects of leveller adjustments on the unflattened sheet metal. In this study, edge- and centre waves are investigated. In order to find a suitable adjustment of the leveller to reach a flat sheet metal, an analytical 3D simulation model has been developed using the Matlab programming environment. The sheet metal will be firstly analyzed and visualized before and after deformation. A user-friendly interface has been developed to enter the required parameters before starting the simulation. Different methods have been used to investigate the effect of the levelling process on the sheet metal and to calculate the remaining shape defects after levelling. The simulation results were validated by experiments and are represented in this paper.     

热轧带钢平整机组的技术改进

分析了热轧带钢平整机组的生产工艺和设备的特点,针对宝钢热轧精整分厂的二辊平整机组存在的不足之处,提出了改造方案:增加下表面检查平台、废板夹送辊、废板输送链、末板废板倾翻装置、废料导板,改造出口剪后导板台等。使机组成材率增加1.5%,生产能力提高4万t/年。并提出对平整机组技术改进时应注意的问题,为平整机组的设计与改造提供了参考依据。