Pulse electrodeposition of nanocrystalline nickel using ultra narrow pulse width and high peak current density

The synthesis of nanocrystalline nickel by electrodeposition has been studied for more than 10 years. However, most attention has been on the adjustment of bath composition or development of new chemical additives. In this paper, a new method was developed to synthesize bulk nanocrystalline nickel without using any additives. Pulse plating with ultra narrow pulse width and high peak current density was employed to increase the deposition current density and the nucleation rate. At an on-time of 10 μs and an off-time of 90 μs, it was found that different surface morphologies, grain sizes, textures, and hardness were obtained at different current densities. Grain sizes ranging from 50 to 200 nm were obtained when the current density varied from 300 to 60 A dm-2. The preferred orientation of the nickel deposit changed from a weak (2 0 0) fiber texture to a strong (2 0 0) fiber texture when the peak current density increased from 40 to 100 A dm-2. It was obtained however that the intensity of the (2 0 0) fiber orientation decreased when there was a further increase in the current density. The hardness of the nickel deposit was also found to increase with increasing peak current density when it changed from 20 to 150 A dm-2, but the hardness tended to decrease when the current density was above 150 A dm-2. These experimental findings are considered to relate to the change in cathodic overpotential which affects both the grain size, the internal stress, the porosity, and the preferred orientation.