The preparation of nickel powders by the ultrasonic spray pyrolysis of Ni(H
COO)(2) was studied. Phase-pure nickel powder was obtained at as low as 350
degreesC. HCOOH was a reducing source for nickel formation. Moreover, meta
llic nickel was obtained at a residence time as short as 0.1 s at 600 degre
esC. A broad range of particle morphologies, which included agglomerated na
noparticles, nonagglomerated submicrometer particles, hollow particles, and
spherical dense particles, were obtained from Ni(HCOO)(2) pyrolysis and we
re shown to depend on the precursor solution and the operating condition.