Preparation And The Interfacial Diffusion And Structure Of Nanocrystalline Nickel Coating

In recent years, nanocrystalline materials with grain size of less than 100nm have received considerable attention. Because of the ultrafine grain size and high intercrystalline volume, nanocrystalline materials exhibit numerous unique physical, chemical as well as mechanical properties compared with traditional polycrystalline materials, as a result, which now became a popular research field in material science and condensed physics. The prepared method for nanocrystalline materials is one of important task in nanocrystalline materials research field. Compared with other prepared methods, electrodeposition in producing nanocrystalline material has some special advantages. Jet-electrodeposition is kind of high-velocity, selective electrodeposition technique with high deposition current density and high velocity. In oversea countries, a great many fundamental researches and application researches are carried out on current-potential distribution and mass transfer about the electrodepositon method as well as the development and application about this technique. In home, jet-electrodeposition technique has also gradually received concerns. High current density and ideal deposition over-potential can be obtained by jet-electrodeposition, which are useful to the formation of nanocrystalline materials. As a result, jet-electrodeposition for preparation of nanocrystalline materials has potential extensive application and is worthy for advanced research.Deeply-steel strip with nickel electrodeposited coating is a newly high-property material for battery shell with good ductility and high corrosion resistance, which is produced with nickel coating deposited on the mild steel and followed with some special optimum treatment. Jet-electrodeposition technique in deeply-steel strip with nanostructured nickel electrodeposited coating will not only reform itsproperties, especially in local corrosion resistance, improve production efficiency, lower production cost, but also widen its application field.The investigations of this Master Thesis are divided into two parts. In the first part, nanocrystalline nickel coating is prepared on mild steel substrate by using jet-electrodeposition technique, following with the discussion in the influence of electrodeposition parameters on the microstructure and properties of coating. In the second part, under certain deposition conditions, interface diffusion treatments were carried out for nanocrystalline coating sample and the microstructure features are investigated.In the Introduction of this article, related research background and research status are introduced firstly. Then, advantages, principle, methods and influential factors of electrodeposition for preparing nanocrystalline materials as well as property and the potential of the application are reviewed. Development history and research status about jet-electrodeposition and the background about this Master Thesis are also given in the Introduction. In chapter 1, the theory of grain refinement and enhanced deposition velocity in jet-electrodeposition technique are discussed. The possibility for preparing nanocrystalline materials by jet-electrodeposition technique is also analyzed. Corresponding the research in the article, a set of unsubmerged single circular jets equipment was designed. In chapter 2, jet-electrodeposition was carried out both under direct current condition and pulse current condition. A series of samples for nanocrystalline nickel coating were prepared under different deposition parameters. Following that, the microstructure and properties of coating were analyzed and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Vickers microhardness indenter. Under direct current jet-electrodeposition condition and pulse current jet-electrodepositioncondition, the influences of the deposition parameters such as current density, electrolyte jet velocity on the microstructure and microhardness is discussed in detail. In chapter 3, Ni nanocrystalli...