Rapid nickel oxalate thermal decomposition for producing fine porous nickel metal powders: Part 1: Synthesis

Precursor nickel oxalate powder was entrained in pure argon and a 5% hydrogen-in-argon carrier gas flow and carried through a heated transport tube reactor. The reactor wall temperature was maintained at 748–1018 K for residence times less than 4 s. Rapid reaction was possible because of high particle heating rates. A 5% addition of hydrogen to the carrier allowed for the synthesis of a high-purity elemental nickel powder with low residual oxygen content. Product particles consisted of nano-sized primary particles contained within an overall microcontainer matrix. Primary nickel particles nucleated within the precursor microcontainer matrix, followed by a coalescence period. The product powder was characterized as 2–40 μm diameter microcontainer particles comprised of nano-sized nickel primary particles with diameters of 20–70 nm. The production of porous elemental nickel powder via the aerosol flow thermal decomposition of nickel oxalate results in powder with acceptable electrical properties and is more benign and potentially cheaper than the current commercial process for nickel powder production.