Study On The Electrochemical Fabrication And The Related Theories Of Black Nanostructured Ni Films

Compared to the traditional polycrystal and amorphous materials, metal matrix nanocomposite thin films exhibit many excellent performances, such as unique magnetic, optical, physical chemic properties and so on. Consequently, it has a expansive applied foreground in many fields, so extensive research efforts with regard to nanostructure material have been done. It is well known that deposition of electrochemical coatings (EC) is not a newly developed technique and has been in continuous development since the 1970s. Meanwhile, when compared with other techniques for nanostructure material synthesis, electroplating possesses many advantages including: low cost and industrial applicability, simple operation, versatility, high production rates and so on. Therefore, the EC technique has arosed attention of many investigators in the world. Black coatings are simple and elegance, because the coating has a matte, heat-absorbing characteristics, which were widely used, often black films including black chrome plating, black nickel et al, of which the most studied was black nickel, but the Black Nickel confined is conventional structures, nano-structured Black nickel is not reflected in domestic and international coverageBased on the theories of "epitaxial growth" and "derivational nucleation", this dissertation tries to adopt a modification method based on traditional electroplating technique to fabricate the holistically nanostructured black Ni films. The research not only has value in theory, but also has an expansive applied foreground.Firstly, the influences of principal technological parameters on the microstructure of eletrodeposited nanostructure black Ni film were studied. Such as: current density, pH value, temperature, solution agitation speed and so on. We optimized a steady technique ultimately.Secondly, the microstructure of the optimized nanostructure black Ni film was characterized by scanning transmission electron microscopy (SEM), atomic force microscope (AFM) and X-ray (XRD), It can be clearly seen that the optimized nanostructure black Ni film is substantially nanostructured in character.Finally, the mechanism was stuied, Cyclic voltammetry (CV), Chronoampermetry (CA) and electrochemical impedance spectroscopy (EIS) at cathodic potential were performed. In the case of high deposition overpotential, the electroplating of nanostructured black Ni film followed 3D nucleating and subsequent instantaneous grain growth mechanism.In addition, the corrosion behavior of nanostructured black Ni films has been investigated in 3.5.wt. % NaCl solution by electrochemical impedance spectroscopy (EIS) and Tafel plots measurements. The results shown that, the corrosion behavior of nanostructured black Ni films was divided into two sequential stages according to the characteristics of EIS data. At the first stage, two time constants involved; and at the second stage, there were three time contents while the low frequency one from the diffusion. Otherwise, the nanostructured black Ni films have good corrosion resistance compared with the commercial nickel film.