Nanocrystalline Nickel Dispersed with Hydrolyzed Nano-Size Tungsten Oxide Particles by Electrodeposition

Nanocrystalline nickel dispersed with nano-size WO3 particles has been successfully synthesized using electrodeposition. In this synthesis, ionized WO4 2- molecules in an electrolyte are hydrolyzed WO3 particles and embedded into a nanocrystalline nickel matrix during electrodeposition by controlling the pH and potential of the electrode. The effect of the nano-size WO3 dispersions on the mechanical property and thermal stability of the nanocrystalline nickel is investigated in detail. The nanocrystalline nickel electrodeposited with nano WO3 particles have the same size as the nickel matrix of approximately 25 nm and the dispersed WO3 particles which is approximately 15 nm. The nickel electrodeposited with the WO3 particles has a higher hardness than that without the WO3 particles in the range of the nickel matrix grain size which is less than about 130 nm. The increase in the hardness is attributed to dispersion strengthening of nano WO3 particles. The nickel electrodeposits with the WO3 particles possess an increased thermal stability compared to the material without the WO3 particles. The nickel matrix grain size of electrodeposits associated with the WO3 particles hardly changed even after annealing for 18 ks at 573 K. The thermal stability of the nickel electrodeposits with the WO3 particles is attributed to the Zener drag effect of nano the WO3 particle.