Preparation of graphite nanosheets in different solvents by sand milling and their enhancement on tribological properties of lithiumbased grease

Graphite nanosheets with the average thicknesses ranging from 24.4 to 48.9 nm were prepared with the use of expanded graphite as the raw material by sand milling in deionized water, anhydrous ethanol, glycerol, and 1,4-butanediol, respectively. Anhydrous ethanol favored the formation of graphite nanosheets with a smaller average thickness. When the graphite nanosheets with the content of 2 wt% were added in lithium-based grease, the average friction coefficient decreased by 27% as compared with the pure lithium-based grease. The weld point and load wear index were 1.6 and 1.4 times those of the pure lithium-based grease, respectively. The tribological properties of the graphite nanosheet-containing lithium-based grease were comparable with those of the graphene-containing lithium-based grease.