Hexamethylenetetramine-Precipitated α-Ni(OH)2 as Precursors for NiO Nanoparticles: Structural and Morphological Characterization.

Influenced by their morphology, nanocrystalline nickel hydroxide and nickel oxide have important technical applications. A simple novel procedure allows for the preparation of α-Ni(OH)2 from nickel nitrate using hexamethylenetetramine (HMTA) as the precipitating agent. The product obtained is free of water, but contains intercalated nitrate and HMTA. Hydroxide samples prepared in this manner decompose in a single step at 350 degrees C and can be used as precursors for NiO. The hydroxide and oxide samples were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and nitrogen physisorption. Depending on the solvent system used during synthesis, a-Ni(OH)2 has a leaf-like or a flower-like morphology. The nickel oxides obtained from these samples consist of nanocubes (average particle size: 15 nm) and nanorods (length: 30-60 nm), respectively. The oxide samples are mesoporous and the corresponding surface areas are 40 and 35 m2/g.