Control of the microstructure and mechanical properties of electrodeposited graphene/Ni composite

Nickel composites reinforced with reduced graphene oxide (rGO) nanosheets were fabricated by a direct current electrodeposition technique. The low volume fraction of graphene can promote the cathodic polarized potential, facilitate the transport of ions and electrons on electrodes, and provide a large number of nucleation sites, consequently accelerate the formation of heterogeneous microstructure features. The graphene/Ni composite with 2 mL graphene dispersions demonstrates a tensile strength of 864 MPa and a plastic elongation of 20.6%, which are 25% and 36% higher than that of the pure bulk Ni. The enhancements in strength and ductility of the composite can be ascribed to the bimodal microstructure, for which the fine grain population provides for enhanced strength, whereas the coarse grain population enhances ductility by enabling strain hardening. On the contrary, the positive role of rGO in microstructure control will be weakened due to the agglomeration of rGO sheets in a high-volume plating bath. The low adsorption quantity of rGO is unfavourable for the nucleation of Ni matrix, accordingly produces a uniform fine-grained microstructure. The tensile strength of the composite with 5 mL rGO is 750 MPa, whereas the fracture elongation is only 7.5%. It is believed that a proper addition of rGO dispersion makes a promising microstructure for advanced graphene/Ni composite.