Nickel hydroxide nanosheets, nanobelts and nanorods were prepared by hydrothermal treatment of the precipitates obtained at different pH values. The morphology and crystal structure of the products could be controlled simply by adjusting the pH value at precipitation. Interconnected nanosheets of hexagonal beta-Ni(OH)(2) with thickness around 10-20 nm were formed at pH similar to 11, whereas nanobelts with typical widths around 40-80 nm, and nanorods with diameters around 50-60 nm of phase pure alpha-Ni(OH)(2) containing intercalated sulphate ions were obtained in the pH range similar to 9.5-8.5. Thermal annealing of the hydroxides at 500 degrees C yielded cubic phase NiO with morphologies similar to their hydroxide precursors. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy ( FTIR), thermogravimetric analysis (TGA), and energy dispersive X-ray (EDX) analysis were used to characterize the as-prepared products. The role of pH in controlling the phase and morphology of the products was discussed. (C) 2011 Elsevier B.V. All rights reserved.