Electrodeposition of nanocrystalline nickel embedded with inert nanoparticles formed via inverse hydrolysis

Abstract Nanocrystalline electrodeposits embedded with inert hard nanoparticles are applied to coating on engineering materials for high hardness and thermal stability. They have mainly been synthesized from a solution containing a suspension of particles in electrodeposition. In this conventional synthesis, finer particles tend to agglomerate in the electrolyte and are embedded inhomogeneously in the electrodeposits. This work provides a different approach to synthesizing nanocrystalline metal electrodeposits embedded with inert metal oxide particles that are formed through inverse hydrolysis in an electrolyte before embedding in the electrodeposits. In principle, this approach would allow the embedding of particles ranging, in size, from the molecular to the micron scale through control of the pH and the duration of stand-by reaction prior to electrodeposition. Effect of this approach on the hardness and thermal stability of Ni electrodeposits was validated, and agree semi-quantitatively with theoretical values predicted by Orowan strengthening and Zener pinning, both of which assume that dispersed particles are smaller than the matrix grain size.