Simulation on fabricating graphene-coated nickel powders through micromechanical exfoliation

Abstract

Fabricating graphene-coated metal powders have become a crucial method for preparing advanced composites, yet the encapsulation mechanism and mechanical behavior remain unclear. In this work, the mechanical behavior of exfoliation, encapsulation as well as the uniform dispersion of graphene nanoplatelets (GNPs) was elucidated for the first time through molecular dynamics simulation based on a two-step three-dimensional (3D) vibration milling for fabricating graphene-coated nickel powders. The critical collision velocity for separating GNPs layer by layer was obtained and the geometric effects of bulk graphite on graphene exfoliation were analyzed. Compared to cuboid graphite, collisions between nickel powders and spherical graphite were prone to the exfoliation of few-layer graphene. A comprehensive experimental study was conducted to investigate the effects of geometry on the exfoliation of graphene. These results suggest that the cuboid graphite is prone to obtaining graphite sheets rather than few-layer graphene, leading to the formation of GSs/Ni composite powders. While the GNPs coated nickel powders are obtained after the two-step 3D vibration milling via spherical graphite. This study provides a comprehensive understanding of the preparation of graphene-coated nickel powders via micromechanical exfoliation.