Synthesis and characterization of a nickel selenide series via a hydrothermal process

چکیده مقاله

A series of nickel selenides (NiSe and NiSe2) has been successfully synthesized from the reaction of SeCl4 with NiCl2.6H2O in the presence of cetyltrimethyl ammonium bromide (CTAB) as surfactant and hydrazine hydrate (N2H4.H2O) as reductant at 180 oC for 12 h through a simple hydrothermal method. The morphology, phase structure and composition of NixSey can be controlled by adjusting the Ni/Se ratio of the raw materials, the quantity of reductant, the reaction temperature and so forth. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. It was found that when the ratio of Ni/Se is 1:1 or 3:2, flower-like assemblies of NiSe nanosheets are formed, at 180 oC for 12h. When the ratio of Ni/Se is 1:2 at 180 oC, the products are found to be the mixture of hexagonal NiSe and cubic NiSe2. With decrease of nickel content in molar ratio of 1:2 (Ni:Se), nanospheres are agglomerated and microstructures are formed. With the reaction temperature decreasing from 180 oC to 120 oC, we reach pure NiSe2 nanoparticles. The formation mechanism of the nickel selenides has been investigated in detail by means of XRD and SEM analyses.