Effect of molecular weight of sodium polyacrylates on the size and morphology of nickel nanoparticles synthesized by the modified polyol method and their magnetic properties

[Display omitted] •Polymer-assisted polyol synthesis of Ni nanoparticles by hydrazine route is reported.•A decrease in the polymer concentrations yields the smaller particles.•Polymers having lower molecularweights are more efficient in reducing the NiNPs size.•The formation mechanism of nickel nanoparticles is discussed.•The as-synthesized nanoparticles exhibit an enhanced coercivity. Nickel nanoparticles were synthesized by the reduction of nickel chloride with hydrazine hydrate in a polyol medium in the presence of sodium polyacrylates (Na-PA) having molecular weights (Mw) of 1200, 5100 and 8000. The size and morphology of the resulting nickel nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy. Polymers having lower Mw values were found to be more efficient in reducing the nickel particle size. A decrease in the polymer concentrations yielded the smaller particles. Magnetic measurements showed that the as-prepared powders are ferromagnetic and their saturation magnetization and coercivity are size-dependent. Compared with bulk nickel, the nanoparticles exhibit an enhanced coercivity which is due to their small size and a decreased saturation magnetization resulted from the surface oxidation of the powder. The synthesis procedure offers a simple approach to preparing nickel nanopowders on a large scale which could be used as magnetic recording materials, including high-density memory storage devices.