An approach for fabricating Ni@graphene reinforced nickel matrix composites with enhanced mechanical properties

A novel approach is developed for the fabrication of nickel (Ni) matrix composites reinforced by graphene, which involves the synthesis of three-dimensional graphene networks (3D GNs) tightly anchored with Ni nanoparticles (3D Ni@GNs) by an in-situ high-temperature chemical vapor deposition process, subsequent uniform coating of Ni powders around the 3D Ni@GNs by an impregnation-reduction process, and final consolidation of the Ni@GNs/Ni composite powders by spark plasma sintering. Owing to the significant grain refinement and homogeneous dispersion of Ni@GNs in the composites identified through the electron backscattered diffraction, scanning and transmission electron microscopy, the composites exhibited much enhanced mechanical properties; the Ni@GNs/Ni composite with 1.0 vol% GNs was demonstrated a yield strength of 474 MPa and a tensile strength of 546 MPa, ~ 188.4% and ~ 26.0% higher than those of the pure bulk Ni respectively. It was thought that the composites were strengthened by both load transfer from the Ni matrix to the GNs and dispersion strengthening of GNs. Meanwhile, the addition of GNs greatly decreased the grain size of the Ni matrix, leading to a significant grain refinement strengthening for the Ni@GNs/Ni composites.