Controlled synthesis of spherical α-Ni(OH)2 hierarchical nanostructures via a simple hydrothermal process and their conversion to NiO

► Pure α-nickel hydroxide (α-Ni(OH)2) nanostructures were prepared via a hydrothermal method. ► Ni(OH)2 nanostructures were converted to NiO by simple calcination. ► NiO nanostructures have shown superparamagnetic behavior.