Abstract
In this work, nickel oxide has been successfully synthesized by high temperature calcination of nickel hydroxide (Ni(OH)2) prepared at first by chemical precipitation, in which Ni(OH)2 was obtained after 30 minutes of the reaction at room temperature using nickel chloride as precursor and ammonia as precipitating agent. At the [Ni2+] concentration was 0.1M and the molar ratio of [NH3]/[Ni2+]=1.28, we could obtain Ni(OH)2 colloids of average size 70 nm measured by dynamic light scattering technique, at the same time the conversion was about 70%. As the colloids’ pH was 3.5, the zeta potential of these particles is 28.6mV, which is large enough to stabilize the solution against aggregation between particles themselves. In addition, by our data of XRD and TGA, we proved the dried Ni(OH)2 powders had totally converted to nickel oxide after 400℃ calcination. Besides, the powders with different calcination temperatures could exhibit different colors. In our case green powders ( By reflex UV instrument, peak of wavelength is 510 nm) could be obtained after 1h calcination at 700℃. By XPS analysis, we confirmed these powders calcined with temperature above 400℃ were only a mixture of Ni2O3 (black) and NiO (green). The computed content of NiO was 36.9% and 60.4% after respective 400℃ and 800℃ calcinations for 1h, and that is the reason for the change in color of nickel oxide powders.