Effect of polyvinyl pyrrolidone (PVP) molecular weights on dispersion of sub-micron nickel particles by chemical reduction process

Four kinds of polyvinyl pyrrolidone (PVP) with various molecular weights (Mw: 111, 8000, 40000, and 630000) were investigated in this work for their ability to disperse sub-micron nickel particles synthesized by chemical reduction of NiCl₂ with hydrazine hydrate. Our results indicate that dispersion of the resultant nickel particles was significantly dependent on the molecular weights of PVP, and all the resultant nickel particles were composed of many nanometer-sized nickel crystallites. Using NVP (Mw = 111) or PVPk90 (Mw = 630,000) as dispersant, nickel particles seriously aggregate. PVPk30 (Mw = 40,000) is the most effective dispersant. Nickel particles synthesized with PVPK30 as dispersant show perfect dispersion status, owing to the fact that polyethylene main chains of PVPk30 bonded on the surface of nickel particles could offer good protection against agglomeration of nickel particles. In comparison with other obtained nickel powders, nickel powders synthesized with PVPk30 as dispersant show excellent electrical conductive property in the nickel powder/epoxy composite.