Synthesis of Needle-like Nickel Powder by Thermal Decomposition of Nickel Oxalate

Needle-like nickel powder with high aspect ratio was synthesized by the thermal decomposition of the precursors consisting of nickel ammine oxalate precipitated from aqueous solution. Nickel precursors of c.a. 1 μm in length and 50 nm in width were obtained by falling two solutions in drops simultaneously into distilled water at pH 9.5. One is a solution containing nickel chloride hexahydrate and ammonia, and the other is a sodium oxalate solution. The morphology of particles changed from granular to needle-like with the increase in pH. Large and size-dispersed needle-like particles were obtained at 363 K. The shape of metallic nickel particles changed from needle-like at 613 K to chain-like at 673 K depending on the heating treatment temperature of nickel precursors.