Composite Ni-NiO nanoparticles have been prepared via thermal decomposition of nickel citrate. Based on the thermal analysis results, the citrate precursor was pretreated for 1 h, in air, over the temperature range of 150-700 degrees C. The obtained solids were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was observed that the Ni-NiO composite starts to form as a result of calcining the precursor at 300 degrees C. Moreover, pretreatment of the precursor at 300-700 degrees C allows control over the Ni to NiO ratio. FE-SEM investigation of the synthesized powders showed that the obtained Ni-NiO composite consists of a porous network of particles with a cauliflower-like morphology. The TEM study revealed that the particle sizes of the composites obtained at 400 and 700 degrees C were in the ranges of 4-21 nm and 8-50 nm, respectively. The magnetic coercivity (H-c) of Ni-NiO composite is found to decrease from 139 to 73 Oe upon increasing the pretreatment temperature from 400 to 700 degrees C. (C) 2017 Elsevier B.V. All rights reserved.