An improved chemical reduction route for fine nickel powders

We report an improved chemical reduction route toward fine nickel powders by using nickel hydrazine complexes [Ni(N₂H₄) ₃SO₄ and Ni(N₂H₄)_nCl ₂ (n = 2 and 3)] as the starting materials, rather than Ni(OH) ₂, which is used in the conventional procedure. The reductions of the hydrazine complexes had reaction rates that were three to ten-fold higher than those of the conventional method. As a result, the products consist of homogeneous, phase-pure, spherical, fine nickel particles that have smooth surfaces; they were formed without the need for additives or extreme reaction conditions. The reaction rates could be related to the solubilities of the precursors, which increase in the order Ni(N₂H₄) ₂Cl₂ > Ni(N₂H₄) ₃Cl₂ > Ni(N₂H₄) ₃SO₄; we propose a reaction mechanism based on this observation.