Friction-induced motion evolution of reduced graphene oxide-Al2O3 at contact interface to achieve superior lubrication performance
CL Wang and JL Sun and JQ He and CL Ge, APPLIED SURFACE SCIENCE, 604, 154479 (2022).
Reduced graphene oxide-Al2O3 (rGO-Al2O3) nanoparticle (NP) was synthesized and applied as additive in water -based lubricants. Pin-on- disk tribological experiments indicated that rGO-Al2O3 nanofluid exhibited reinforced lubricity due to the formation of a double-layer tribofilm, contributing to 34.8 % +/- 2.3 % and 78.2 % +/- 2.5 % reduction in friction coefficient and wear rate. Combined with nonequilibrium molecular dynamics (NEMD) simulation, rGO-Al2O3 NP exerted synergistic effects of interlayer sliding, rolling, polishing and self-mending to obtain higher surface quality. A new parameter (p) was proposed to determine the motion modes of Al2O3. Al2O3 NP exhibited both rolling and sliding motion. The synergy of rGO and Al2O3 NPs increased the rolling motion proportion of Al2O3 from 78 % to 91 % compared to using alone. Similarly, about 12.6 % of the friction force in friction system was shared by the interlayer sliding of rGO monolayers in the presence of Al2O3 than the system with only rGO (9.5 %). Besides, rGO-Al2O3 had higher diffusion coefficient, which was more conducive to the formation of tribofilm. rGO nanosheets with large transverse size adsorbed on the Fe surface to prevent the embedding of high hardness Al2O3 to maintain its rolling effect. Meanwhile, Al2O3 can reversely stimulate the interlaminar sliding of rGO to enhance the lubrication performance of rGO-Al2O3 nanofluid.
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