Electrodeposition of Nanocrystalline Ni-based Alloys

Nanocrystalline materials can often process superior properties, but they are generally unstable against grain growth. Addition of a dopant can stabilize nanocrystalline alloys by decreasing the excess grain boundary energy as the thermodynamic driving force for grain growth and reducing grain boundary mobility via a kinetic effect of solute drag. In this thesis study, eight Ni-based alloys (Ni-W, Ni-P, Ni-Mo, Ni-Cu, Ni-B, Ni-Mg, Ni-Zn and Ni-Co) and pure Ni were made using an electrodeposition method. It is concluded that the use of different dopant can drastically affect the deposition mechanism as well as the morphology of resultant films. Ni-W and Ni-P films, which are the most dense and uniform among the eight Ni-based alloys, were selected for a systematic study. Pure Ni films were also investigated for comparison. Grain sizes were measured by X-ray diffraction, and film morphologies were characterized by optical microscopy and scanning electron microscopy. An inverse correlation between the doping concentration and the grain size is confirmed for both Ni-W and Ni-P. Doped and undoped specimens are annealed at various temperatures in flowing Ar-H2 to probe grain growth