Effect of synthesis conditions on the performance of weakly agglomerated nanocrystalline NiO

Weakly agglomerated nanocrystalline NiO was synthesized by a homogeneous precipitation method in the presence of urea as the precipitation agent. The reaction mechanism about the hydrolyzation of urea, the precipitate process of the as-synthesized precursor, and the decomposition of the precursor during heating treatment was discussed. The effects of the ions concentration and the calcinations temperature on the powder properties were investigated. The as-synthesized precursor was characterized as hydrated basic carbonate by IR spectrum and TG analysis. The results revealed that crystallization started at about 350 °C, and the nanoparticles with the average crystallite size of 5 nm were obtained. With increasing the molar ratio of urea to Ni²⁺ ion, the crystalline size showed a slight increase, and then decrease, however the pH and the yield indicated a pronounced increase. During heating, an enhanced crystallite growth was observed.