Formation of alpha,beta-Type Hydroxides and Second-Stage Intermediate in Hydrothermal Decomposition of Nickel Acetate

During heating of nickel acetate solution at a constant rate of 4°C/min up to 350°C, alpha-type anion-exchangeable layered hydroxide Ni2(OH)3(OCOCH3)1.4H2O, containing the acetate anions in the interlayer spaces, first crystallized at 160°C. A second-stage intermediate phase losing the acetate guest in every second layer appeared at 180°C and subsequently transformed at 210°C to slightly disordered beta-Ni(OH)2 phase with a small amount of acetate anions. beta-Ni(OH)2 phases were gradually losing the acetate guest with increasing temperature, and perfectly ordered hexagonal-shaped beta-Ni(OH)2 crystals with a mean diameter of 10 mu m were obtained at 320°C. Above 340°C, dehydration of beta-Ni(OH)2 to NiO occurred.