Ni nanoparticles with different mean diameters of 15-83 nm were synthesized by solution reduction process. The size of Ni nanoparticles can be controlled by varying the concentration of NiCl(2)center dot 6H(2)O and synthesis temperature. The smaples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM). X-ray diffraction (XRD), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). Results show that the synthesized particles are single-phased Ni with a face-centered cubic crystal structure. Magnetic measurements indicate that Ni nanoparticles are ferromagnetic. The lattice constants and coercivities of the samples are size-dependent. (C) 2008 Elsevier Ltd. All rights reserved.