Size and morphology-controlled synthesis of Ni3C nanoparticles in a TEG solution and their magnetic properties

Abstract

Nickel carbide nanoparticles (Ni₃C NPs) were synthesized by a polyol solution refluxing route at a temperature of 300 °C for 20 min using triphenylphosphine oxide (TPPO) as the surfactant. Size and morphologies of the Ni₃C NPs were controlled by adjusting the concentration of Ni(NO₃)₂ and TPPO. The products consisted of Ni and Ni₃C could be kinetically controlled by a reaction temperature of 250–290 °C and time less than 20 min and the proportion of the Ni component was lower with longer reaction times and higher temperatures due to carbon atom insertion via a carbonaceous film that formed on the surface of the growing particles. The formation process of the Ni₃C NPs was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) characterization. The saturation magnetizations of products decreased with decreasing ratio of Ni : Ni₃C, which inferred that Ni₃C was non-magnetic and the magnetism arose from trace Ni in the products.