Preparation of Ni particles by ultrasonic spray pyrolysis of NiCl2·6H2O precursor containing ammonia

The preparation of nickel particles from nickel ammine complex was studied by ultrasonic spray pyrolysis in the presence and the absence of hydrogen. In the presence of H2 (about 9 vol.%), nickel particles were formed at 500 °C, which is much lower than that reported. Metallic nickel, together with NiO, was obtained as a major phase at 400 °C. In the absence of H2, metallic Ni was also obtained, but higher temperature (e.g. 900 °C) was needed. It is suggested that the addition of NH3·H2O and NH4HCO3 to NiCl2·6H2O precursor changes the reaction pathway of Ni formation. By careful control, spherical, solid and well-distributed Ni particles of about 0.5 μm were obtained at a residence time of 7–9 s in the aerosol reactor.