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喷射电沉积法制备多孔金属镍机理、工艺及应用研究

Study on the Mechanism, Process and Application of Porous Nickel Prepared by Jet Electrodeposition

【作者】 宫凯

【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, 2010, 博士

【摘要】 多孔金属材料作为一种性能优异的新型功能材料和结构材料,具有广泛的多功能应用前景,已成为当前国内外功能材料领域的研究热点。多孔金属材料的功能性能与其结构直接相关,改变其孔隙率和孔的形貌及尺寸将直接影响到材料的性能。本文工作针对传统多孔金属制备方法在上述方面普遍存在工艺复杂、成本较高等缺陷,采用一种全新的多孔金属制备方法─喷射分层扫描电沉积法制备以多孔枝晶沉积层为层芯、普通薄沉积层作面板而制成的夹心式层合式的块状三明治结构多孔金属镍。以孔隙结构优化设计和应用为目标,通过调节各种工艺参数和控制条件,使沉积的工作状态在枝晶沉积层和普通电沉积层间交替进行,控制多孔金属镍块的生长,并通过改变试验参数调节芯层孔隙结构和孔隙率,调节普通沉积层生长位置,改变多孔金属镍的三明治状闭孔形貌及尺寸。喷射电沉积法生成的多孔枝晶组织完全是自组织原位生长的,加工过程在常温、常压下进行,不需要其它辅助材料,工艺简单,成本较低,对丰富多孔金属的制造工艺具有重要的现实意义。本文的主要研究工作如下:1.进行喷射电沉积多孔枝晶层的电化学行为机理研究。主要包括:喷射电沉积多孔金属镍的动力学过程及其阴极极化的特点,喷射电沉积过程阴极极化的类型,喷射电沉积的交流阻抗行为,喷射电沉积镍的电结晶行为。2.对喷射电沉积过程中喷射速度场和压力场进行了理论分析,建立单股冲击射流紊流流动的基本数学模型。采用扩散限制凝聚模型(DLA)对喷射电沉积过程的多孔枝晶组织的形状和生长过程进行了模拟研究,并进行了验证性试验。3.研制了喷射电沉积逐层扫描制备三明治状多孔金属镍试验系统。成功制备了具有一定形状和厚度的块状多孔金属镍样品;并对制备的多孔镍的表面形貌、孔隙结构、显微组织和力学性能进行了研究。4.通过采用喷射电沉积制备的三明治状多孔金属镍为集流体,以纳米NiO为电极活性材料制成电化学电容器电极,并对组装的电容器性能特性进行了表征,结果表明:电容器储能方式主要以赝电容形式存在,单电极比容量为582-527F/g,电极电荷传递阻抗小,电容电化学行为优良。

【Abstract】 Porous metal material is a new type of functional and structural material with good performance; it has prospective application in a wide range and has been a heated research area of functional material all over the world. Meanwhile, the performance and characteristics of the porous metal material are directly related to its structure; variations in the porosity, features and sizes of the pores can directly influence the performance of the material.With the background mentioned above, this paper presents researches and discussions over the following aspects: aiming at the complicated processes and high costs that generally exist in the traditional porous metal preparation techniques, a whole new porous metal preparation technique-layer scanning jet electrodeposition of "sandwich-structured" porous nickel metal-is introduced. This bulk "sandwich structure" of the nickel metal has porous dendritic crystalline deposited layers as core layers, and normal thin deposited layers as the surface panels on both sides.This technique aims at the optimal design and the application of pore structure in the nickel metal, and through the manipulation of different kinds of machining parameters and control conditions, the working condition of the electrodeposition is able to shift between dendritic crystalline layer electrodepositing and normal layer electrodepositing alternately, and growth condition of the porous dendritic crystalline layers can be fairly controlled; this technique can also regulate pore structure and porosity of the core layer, growth location of normal deposited layer, and make variations to features and sizes of sandwich-like pores in the porous metal.Compared to other methods, the foam structures generated by jet electrodeposition technique totally grow up from the origin structure position. During the machining procedure, no subsidiary materials are added in, which allows a simpler process and a relatively lower cost. This technique is achieved under normal temperature and normal pressure condition, and requires not much of the environment or the equipment. This research has important and realistic significance on enriching applicable preparation processes of foam metals. Following works have been done and included in this paper:1. Researches on electrochemical mechanism and behavior of jet electrodeposition of porous metal preparation, which include: its kinetic process and polarization characteristics on cathode, the type of cathodic polarization during the process, the AC impedance behavior of the jet electrodeposition, and the electrical crystallization behavior of the jet electrodeposition of nickel.2. Theoretical analysis is conducted on the jet velocity field and pressure field of the jet electrodeposition procedure, then a fundamental mathematical model for the single-strand turbulent flow is set up. We apply the diffusion-limited aggregation (DLA) model to simulate the feature and growth process of the dendritic structures that exist during the electrodeposition procedure, and made verifying tests.3. Develop a test system for the preparation of bulk porous nickel metal processed by layer scanning jet electrodeposition. Use this system to make some bulk porous nickel samples with certain shapes and thicknesses, and study the surface features, pores, micro structures and mechanical properties.4. Porous nickel metal prepared by jet electrodeposition is treated as the current collector. Then make the electrochemical capacitor electrodes using electrode active nano-NiO material, and finally characterize the capacitor properties. Tests made indicate: Capacitors using the jet electrodeposited porous nickel metal as current collectors show typical characteristics of super capacitor, and they exist mostly in the form of faradic pseudocapacitance. With Specific capacitance of single electrode of the specimen varies within 582-527F/g. Capacitors have the advantages of low particle transfer impedance, good electrochemical capacitor performance.

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