Mechanical properties of nickel-graphene composites synthesized by electrochemical deposition.

Graphene (Gr) nanosheets with multilayer structures were dispersed in a nickel (Ni) plating solution by using a surfactant with a magnetic stirring method. Gr nanosheets were incorporated into a Ni matrix through a plating process to form Ni-Gr composites on a target substrate. Gr nanosheets were uniformly dispersed in the Ni matrix, and the oxygen radicals present in the Gr were reduced during the electro-deposition process. The incorporation of Gr in the Ni matrix increases both the inter-planar spacing and the degree of preferred orientation of crystalline Ni. With the addition of Gr content as low as 0.05 g L(-1), the elastic modulus and hardness of the Ni-Gr composites reach 240 GPa and 4.6 GPa, respectively, which are about 1.7 and 1.2 times that of the pure Ni deposited under the same condition. The enhancement in mechanical properties of the composites is attributed to the preferred formation of the Ni crystalline phases in its (111) plane, the high interaction between Ni and Gr and the prevention of the dislocation sliding in the Ni matrix by the Gr. The results suggest that the method of using Gr directly instead of graphene oxide (GO) is efficient and scalable.