Thermal Decomposition Synthesis of Monodisperse Nickel Nanoparticles: Structural, Morphological and Magnetic Characterization

Abstract

Nickel nanoparticles have attracted considerable attention because of their size-dependent structural, morphological, magnetic, and catalytic properties. In this study, nickel nanostructures were synthesized through the thermal decomposition of a nickel oleate precursor in a mixture of 1-octadecene and oleic acid under a nitrogen atmosphere. The reaction was conducted at 638 K for 80 min with continuous mechanical stirring. The crystalline structure was investigated using X-ray diffraction (XRD), while particle morphology and size were examined using field-emission scanning electron microscopy (FESEM). Magnetic properties were evaluated through field-dependent magnetization measurements at 20 K and 300 K. The XRD pattern exhibited characteristic reflections at 44.78°, 52.16°, 76.72°, 93.23°, and 98.76°, corresponding to the (111), (200), (220), (311), and (222) planes of face-centred cubic nickel, respectively. The average lattice parameter was calculated as 0.350 nm, and the crystallite size estimated using the Scherrer equation was approximately 21 nm. FESEM analysis revealed nearly spherical, weakly agglomerated particles with an average measured diameter of approximately 28 nm, based on the analysis of 100 particles. The saturation magnetization was approximately 35.2 emu g⁻¹ at 20 K and 32.5 emu g⁻¹ at 300 K. The coercivity decreased from 0.0284 T at 20 K to 0.0039 T at 300 K. These findings demonstrate the relationship between nanoscale structure and magnetic response in thermally synthesized nickel nanoparticles and highlight the importance of controlled synthesis conditions for obtaining nickel nanomaterials with reproducible properties.