Effect of Crystallinity ofβ- andβbc-Nickel Hydroxide Samples on Chemical Cycling

摘要

β-phases of nickel hydroxide and cobalt hydroxide samples crystallize in cadmium iodide type structure.β-cobalt hydroxide on oxidation generatesβ-CoOOH which crystallized in 3R1polytype while the structure ofβ-phase of NiOOH polytype is less well understood.β- andβbc-phases of nickel hydroxide samples were prepared by using ammonium hydroxide and sodium hydroxide as precipitating agents. Powder X-ray diffraction data shows thatβ-phase of nickel hydroxide is perfectly crystalline in nature whileβbc-phase of nickel hydroxide is poorly ordered.β- andβbc-phases of nickel hydroxide samples were subjected to chemical oxidation using sodium hypochlorite. The oxidized phases ofβ- andβbc-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 ofβ- andβbc-phases of nickel oxyhydroxide, the powder X-ray diffraction patterns visually match the powder X-ray diffraction data of the pristine phases ofβ- andβbc-phases of nickel hydroxide indicating that theβ-phase of nickel hydroxide does not transform toβbc-phase of nickel hydroxide, but the particle sizes are significantly affected.