Influence of additives on the properties of spherical nickel particles prepared by ultrasonic spray pyrolysis

Ideal spherical nonagglomerated Ni particles (mean diameter 0.62–1.12 μm) were prepared by ultrasonic spray pyrolysis of NiCl₂ aqueous solution in the presence of 0.1 mass% of Pd, Cu, or Ni in an H₂–N₂ atmosphere at 900 °C. Incomplete reduction of the NiCl₂ aqueous solution in the absence of additives was observed under the same conditions. Differential thermal and thermal-gravimetric analyses revealed a decrease in initial reduction temperature of NiCl₂ from 375 to 275 °C by the addition of Pd, Cu, or Ni. The morphology of Ni particles was analyzed using scanning tunneling microscopy. The surface roughness of Ni particles was found to be controllable by addition of appropriate additives.