Effect of Crystallinity of β- and βbc-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 3R1 polytype while the structure of β-phase of NiOOH polytype is less well understood. β- and -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 -phase of nickel hydroxide is poorly ordered. β- and -phases of nickel hydroxide samples were subjected to chemical oxidation using sodium hypochlorite. The oxidized phases of β- and -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 -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 -phases of nickel hydroxide indicating that the β-phase of nickel hydroxide does not transform to -phase of nickel hydroxide, but the particle sizes are significantly affected.