Synthesis and characterization of Ni(OH)_2 and Co(OH)_2 nano-sheet crystals

Transition metal hydroxides Ni(OH)_2 and Co(OH)_2 nano-sheet crystals with hexagonal morphology have been successfully synthesized through hydrothermal method using strong alkali(KOH) as precipitator.The structure and morphology of the as-prepared samples were characterized by X-ray diffraction(XRD) and transmission electron microscopy(TEM).TEM observations exhibit that the Co(OH)_2 phase is formed with the regular hexangular nano-sheets,while Ni(OH)_2 phase a mixture of nano-sheets and nano-rods.Selected area electron diffraction(SAED) patterns reveal the single crystalline nature of the entire nano-sheet.The yields of the nano-sheets for Ni(OH)_2 and Co(OH)_2 reach about 70% and 90%,respectively.It is proposed that hexagonal sheet is a stable crystalline morphology for the current solid compounds under normal precipitation conditions.Comparing with the previous reports on synthesis of transition metal hydroxide nano-sheet by the other methods,a new formation mechanism of nano-sheets has been discussed.