Formation of α,β-type hydroxides and second-stage intermediate in hydrothermal decomposition of nickel acetate

During heating of nickel acetate solution at a constant rate of 4 degrees C/min up to 350 degrees C, alpha-type anion-exchangeable layered hydroxide Ni-2(OH)(3)(OCOCH3)1.4H(2)O, containing the acetate anions in the interlayer spaces, first crystallized at 160 degrees C. A second-stage intermediate phase losing the acetate guest in every second layer appeared at 180 degrees C and subsequently transformed at 210 degrees 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 degrees C. Above 340 degrees C, dehydration of beta-Ni(OH)(2) to NiO occurred. (C) 1999 Academic Press.