The properties of nickel aluminate nanoparticles prepared by sol-gel and impregnation methods

Nickel aluminates were prepared by sol-gel and impregnation methods and calcined at 1100 A degrees C. The sol-gel made samples were prepared with different amounts of nickel (Ni/Al molar ratio equal to 0, 0.25, 0.5, and 0.75) and aging times (24 and 48 h). The samples were characterized by X-ray diffraction, induced couple plasma, nitrogen physisorption, transmission and scanning electron microscopy, and ammonia temperature programmed desorption (NH3-TPD). In the sol-gel made samples, only the NiAl2O4 structure of nickel aluminate was defined, while for impregnation, NiAl10O16 was formed as well. The sol-gel made samples had low specific surface areas (7.7-12.4 m(2)/g), but a sample prepared by impregnation method had higher specific surface area (67.2 m(2)/g). The surface acidity density decreased by increasing the amount of nickel and was the lowest for impregnation method.