Fabrication of nickel-graphene composites with superior hardness

Bulk nickel graphene (Ni-Gr) composites are in the high demand for most of the engineering applications. Despite many efforts made, the main problem remains the homogeneous dispersion of graphene into the Ni matrix without destroying the structural integrity of Gr. The present paper addresses the fabrication, structural features and mechanical characteristics of bulk Ni-Gr composites, manufactured from nanosized nickel powder and exfoliated graphite platelets (GP) via modified powder metallurgy procedure including micromechanical GP splitting. The combination of XRD, SEM, Raman spectroscopy and EBSD analysis revealed homogeneous distribution of Gr in Ni matrix and the significant grain refinement observed for Ni-0.1 wt% Gr composite. Bimodal grain size distributions were obtained for all samples studied, and the mean grain size depends on Gr content. Raman spectroscopy proved the complete GP-to-graphene conversion for composite with 0.1 wt% Gr. Bulk nickel specimen and composites exhibit -3 times higher hardness and moderate tensile strength values compared to Ni, manufactured from micron-sized powders. (C) 2020 Elsevier B.V. All rights reserved.