Synthesis and the Structural Transformation of fcc to hcp in Ni-Graphene Nanocomposite by Simple Chemical Route via Sonication

We report the synthesis and structural transformation of fcc to hcp in Ni-graphene (Ni-Gr) composite by simple chemical route via sonication. The syntheses of Ni-Gr composite by simultaneous reduction method, and the effect of different composition ratio on morphology and crystal structure were examined in our present study. The results indicated that the graphene ratio played an important role in crystal structure and d-spacing in nickel crystals. Different compositions have shown different behavior. The nanonickel clusters of various shapes with coated graphene and decorated as nickel on graphene sheets are observed. The synthesized composites were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscope (TEM). The XRD patterns indicated crystal lattice modifications in some composites while composites with a higher graphene ratio produced very small crystals with uniform lattice parameter and d-spacing. FE-SEM images indicated the growth of Datura fruit like shapes of nickel clusters in higher composition of nickel while the composites with least concentration of nickel were composed of cubical nanoparticles grown on graphene sheets. TEM analysis revealed many Ni nanoparticles surrounding the smooth petals like surface of graphene, with average diameters of spiky nickel nanoparticles being about 50 nm and 124 nm, respectively, on 200 nm of scale