In situ modified multilayer graphene toward high-performance lubricating additive

To address the poor dispersibility and incompatibility of graphene toward potential applications, we propose an approach to prepare high-density modified graphene sheets by combining solvent exfoliation of graphite with chemical modification of ionic liquids (ILs). Graphite is exfoliated into graphene sheets along with in situ modification in ILs-containing solution, and ILs-modified multilayer graphene (MLG) is formed because as-exfoliated graphene sheets with the charged groups of ionic liquids can undergo self-assembly together through electrostatic interaction. Here, three ILs-modified MLG was prepared using different alkyl imidazolium ILs, and their structures and tribological properties were investigated in detail. High-density coverage of IL cation and anion moieties is achieved, remarkably enhancing the dispersibility of the graphene in lubricant. MLG hybrid nanofluids show excellent friction-reducing and anti-wear ability for the contact of steel/steel because of the synergistic effect of a physical adsorption film and a tribo-chemical reaction film on the sliding surfaces.