【作者】 王桂峰；

【导师】 黄因慧；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 硕士

【摘要】 金属电沉积方法是现在冶金生产中用于金属提取的一种很重要的制备工艺,而枝晶生长是电沉积过程中存在的一个非常重要的问题,在以电解法生产金属时,往往会因为枝晶的生长而影响生产的正常进行,而有时则要求有特殊形态的枝晶的形成,例如本课题组正在采用喷射电沉积制备泡沫金属的研究,就需要产生特殊形态的枝晶以形成泡沫金属所需的孔隙。所以,对枝晶生长的过程和形貌进行研究,深入了解这一生长现象,实现沉积物形态的可控生长,无疑会对在错综复杂的工业生产过程的顺利进行以及优质产品的制造有所帮助。这些沉积生成的枝晶,具有奇妙的形式上的对称性,但因其形貌上呈现出的极不规则、极其复杂的几何特征,用传统的欧氏几何来处理这一非线性的生长问题是十分困难的,甚至于无法获得数值解,分形几何学的建立为这一研究提供了新的思路。结合分形几何的基本理论,人们广泛地将计算机应用于各种生长过程的模拟中,计算机模拟的一个主要优点是可以随意地设定或改变各种参数,并可以完成大量繁琐的工作量,最后产生一个人们期待的或者意想不到的结果。对于分形电沉积的计算机模拟,具有重大的应用价值,可以解决一些经典电化学未能顾及的问题,并实现对枝晶生长情况更为真实客观地理解和把握,从而引导出更为精细的结论,这无疑更加有利于进一步从机理上研究枝晶的生长问题。本文通过对DLA分形模型进行改进,使用计算机对金属在以点电极、平行板电极作为阴极进行电沉积时所生成的沉积产物的形貌进行了模拟,并模拟了不同离子沉积速度、沉积过程中不同阶段和不同结合概率时生成沉积物的形貌,进而从分形维数的角度对模拟结果之间存在的差异进行了比较、说明。在此基础上,分别以点电极下和平行板电极下金属镍喷射电沉积过程中枝晶的二维生长情况为实例进行了试验,得到了沉积产物形貌与相关条件的相互关系,并对金属镍电沉积过程中,外加电压或通过装置的电流随沉积时间的变化情况进行了测定、分析,同时从物理学的角度对枝晶的生长进行研究,从而实现了二维条件下,不同情况时金属生长规律和形态定量的研究,最后,从分形维数的角度对试验获得的金属镍电沉积产物形貌与电沉积试验所使用的外加电压、通过试验装置的电流、电解液浓度以及试验温度等条件的相互关系进行了研究、分析。更多还原

【Abstract】 Meta electrodeposition plays an important role in industry. Dendritic growth in metal electrodeposition is a very serious problem. When people use the electrolytic process to manufacture metal, the dendritic growth always the reason what make the process can’t normally go on wheels. Some times people also need dendritic crystal with special morphology. For example, our research workers are starting to use special dendritic crystal to produce the foamed metal. With a good Study of the process about the dendritic growth and its morphology, people will be able to control the process of dendritic growth one day, it also can help make sure the anfractuous industrial process go smoothly, and help produce high-quality products. In addition, the morphology of dendritic crystal produced by electrodeposition has marvelous symmetry, but because it’s topography often has more inhomogeneous and complex geometry characteristics, the full nonlinear problem is difficult to solve by the use of traditional Euclidean geometry method, even the numerical solution cannot be got, the appearance of theory about fractal geometry gives a new method to investigate electrodeposition resultfully.Today, combining the basic theory about fractal, people wildly use the computer to simulate various growth process. The major advantage about computer simulation is, people can change the parameters at their option and the computer can automatic accomplish a great deal of miscellaneous task, and finally, it will give one result which people want or can’t expect. The computer simulation has more important applied cost, people have solved some questions that classical electrochemistry never considered and led more tenuously conclusions with it. It is also very useful for people to understand the process of dendritic growth in mechanism.In this paper, the simulation about the growth process of electrodeposition which used the point electrode and parallel plate electrode as cathode had been realized by means of modifying the DLA model. With the computer, the results of electrodeposition with different deposition rates, reaction stages and united probabilities were compared and analyzed by the way of fractal dimension. And then, experimental investigations on the two-dimension dendritic growth process of metal nickel performed with point electrode and parallel plate electrode, and the current time graphs or voltage time graphs in those experiments were got. Then the fractal dimension and macroscopic morphology under various experimental conditions were observed and analyzed.更多还原