Synthesis and characterization of nickel aluminate nanoparticles

In the work, a simple synthesis route for obtaining NiAl₂O₄ nanoparticles was developed. The synthesis route used commercial aluminium foil (Al⁰) reacting with a solution of nickel (II) chloride (NiCl₂) dissolved in a 25:75 Toluene/THF mixture in a controlled helium atmosphere. The reduction synthesis was carried out at 60 °C for 72 h. The phase transformation temperatures of the powder were determined through differential scanning calorimetry and thermal gravimetric analysis (DSC/TGA). The resulting mixture was dried at 80 °C, followed by sintering heat treatments at 500 °C, 700 °C, and 1100 °C, respectively. The powder samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), ultraviolet-visible spectroscopy (UV–vis), attenuated total reflectance (ATR), x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR-TEM) analysis. The results showed the formation of a single NiO phase when sintered at 500 °C and a nickel aluminate (NiAl₂O₄)—nickel monoxide (NiO) biphasic mixture after 700 °C and 1100 °C calcinations. The NiAl₂O₄ nanoparticles displayed an average crystallite size of 13 to 19 nm while the NiO particles are at micrometric size due to the elevation of the sintering temperature. (paper)