Synthesis, characterization and understanding of the mechanisms of electroplating of nanocrystalline-amorphous nickel-tungsten alloys using in situ electrochemical impedance spectroscopy

In this study, a series of Nickel (Ni)-Tungsten (W) alloys were electrodeposited onto copper (Cu) substrates using electroplating baths and tri-sodium citrate (Na3C6H5O7) as the complex agent. The electro co-deposition of Ni-W alloys was carried out by varying several important experimental parameters: the tungstate ion [WO4]2- concentration, the bath temperature and the speed of stirring. Potentio-dynamic polarization and in-situ electrochemical impedance spectroscopy (EIS) techniques were used as electroplating methods to study the processes. The phases present in the films were identified using powder X-ray diffraction (XRD) and electron diffraction (ED). The films were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and their elemental compositions determined using X-ray energy dispersive spectrometry (XEDS). The electrodeposited films were found to be a mixture of amorphous and nanocrystalline Ni-W. This study has allowed us to reach a better understanding of the complex mechanisms and effective parameters of co-deposition of Ni and W using citrate ions complex baths.