Effect of Crystallinity of β - and β bc -Nickel Hydroxide Samples on Chemical Cycling

Abstract

β -phases of nickel hydroxide and cobalt hydroxide samples crystallize in cadmium iodide type structure. β -cobalt hydroxide on oxidation generates β -CoOOH which crystallized in 3R 1 polytype while the structure of β -phase of NiOOH polytype is less well understood. β - and β bc -phases of nickel hydroxide samples were prepared by using ammonium hydroxide and sodium hydroxide as precipitating agents. Powder X-ray diffraction data shows that β -phase of nickel hydroxide is perfectly crystalline in nature while β bc -phase of nickel hydroxide is poorly ordered. β - and β bc -phases of nickel hydroxide samples were subjected to chemical oxidation using sodium hypochlorite. The oxidized phases of β - and β bc -phases of nickel oxyhydroxide are highly disordered and the broadening of reflections in the powder X-ray diffraction patterns is due to the presence of structural disorder, variations in the crystallite size, and strain. On reduction of β - and β bc -phases of nickel oxyhydroxide, the powder X-ray diffraction patterns visually match the powder X-ray diffraction data of the pristine phases of β - and β bc -phases of nickel hydroxide indicating that the β -phase of nickel hydroxide does not transform to β bc -phase of nickel hydroxide, but the particle sizes are significantly affected.