Synergistic effect of in-situ synthetic GE@Cu particles as additives for enhancement in lubrication performances

Graphene-encased copper particles (GE@Cu) with fluctuating particle sizes ranging from 3 to 15 nm, 80–210 nm, 270–530 nm, and 1.2–3.5 μm are prepared by metal-organic chemical vapor deposition using cupric tartrate and cupric acetylacetonate as precursors.The reaction temperature has been found a significant effect on the decomposition of the organocopper compounds, the coalescence of Cu/C clusters, and the morphology evolution of GE@Cu particles. Thus, the size of copper particles and thickness of the graphene cladding layer (few-layer and multi-layer) can be strictly controlled by modulating the pyrolysis temperatures of the organocopper compounds. The optimized GE@Cu particles with 0.5 wt% mass ratio in lubricants exhibit the reduction of wear track depths and coefficient of friction comparing with the pure lubricants. The corresponding wear rate for the 0.5 wt% few-layer graphene@Cu (FLGE@Cu) and 0.5 wt% multi-layer graphene@Cu (MLGE@Cu) decreases by 60.3 % and 62.5 %, respectively. Additionally, Raman spectroscopy illustrates the formation of a self-lubricating graphene layer on the wearing surface during the friction with GE@Cu as the lubricant additives. The hybridized structure of this nanoadditive introduces synergistic lubrication effects, involving sliding friction (graphene) and rolling friction (copper particles) at the friction contact surface, leading to enhanced lubrication performance. The comprehensive encapsulation of copper particles by GE established the suitability of this lubricant additive for enduring prolonged and intricate environments. In conclusion, GE@Cu lubricant additives hold great promise across the fields of mechanical equipment, bearings, and engines.