Facile synthesis of a metastable nanocrystalline Ni3N from nickel nanoparticle

Nanoparticle has been a hot topic because of its excellent properties comparing to the corresponding bulk material in many aspects. Here we described a successful use of nickel nanoparticle prepared by a reduction of Ni2+ with hydrazine to synthesize metastable nanocrystalline Ni3N at 513 K in NH3 flow. In comparison, a nickel precursor prepared by a reduction of NiO in hydrogen was not nitrided when it was treated with NH3 at 533 K. The samples were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The XRD patterns showed that the nickel particles prepared by hydrazine reduction had a smaller crystalline size (18.3 nm) than that of nickel particles from hydrogen reduction (49.5 nm), resulting in a low nitriding temperature. As-synthesized Ni3N had spherical morphology and average particle size of ∼30 nm from TEM observation. The temperature-programmed decomposition of Ni3N showed that it began to decompose at 540 K and was finally transformed into metallic nickel.