A sol–gel route using propylene oxide as a gelation agent to synthesize spherical NiAl2O4 nanoparticles

Spherical NiAl2O4 nanoparticles with large surface area were successfully synthesized by a sol–gel method using propylene oxide as a gelation agent. The formation process of the resulting nanoparticles is described and characterized by TG-DTA, XRD, BET and TEM. A pseudo-spinel structure was formed at 700 °C and a spinel NiAl2O4 structure was formed at 800 °C by the reaction of NiO at the surface of amorphous alumina particles. It was found that the presence of NiO or NiAl2O4 on the surface of the alumina retards the crystallization of amorphous alumina to γ-Al2O3. The obtained nanoparticles experienced the decrease of particle size from 700 to 800 °C accompanying the structure transformation from pseudo-spinel to NiAl2O4 spinel.