Synthesis of nanostructured nickel oxide

The process of formation of nickel oxide nanostructured powders by annealing nickel hydroxide in the temperature range 200-700A degrees C was studied. Nickel hydroxide was prepared by precipitation with alkali from nickel nitrate solutions. The annealing process was shown to be multi-step. In the first stage the hydrogel Ni (OH)(2)center dot nH(2)O decomposes and partial dehydration of hydroxide occurs. Sizes of the formed particles decrease. At the temperatures above 230A degrees C, further hydrogel decomposition and coalescence of NiO particles proceed. In view of the structural rearrangement of powder at the high temperatures 400-700A degrees C, dehydration process is monitored by the decrease of NiO particles surface area at their coalescence. According to the change in the dehydration mechanism, the hierarchically nanostructured material forms, whose particle sizes are in the range 4-5, 9-12, and 18-40 nm.