Scientists from Argonne National Laboratory used simulations to identify and improve a new mechanism for reducing friction. The resulting hybrid material exhibited superlubricity at the macroscale.
When the lubricant materials — graphene and diamond-like carbon (DLC) — slid against each other, the graphene began rolling up to form hollow cylindrical “scrolls” that helped to practically eliminate friction and create superlubricity.
A material achieving superlubricity would be valuable for automotive applications, as reducing engine friction will increase fuel efficiency. Such materials will also help to increase the lifetime of the many mechanical components that wear down due to incessant friction.
Prior to the computational work, Argonne scientists Ali Erdemir, Anirudha Sumant, and Diana Berman were studying the hybrid material in laboratory experiments at Argonne’s Tribology Laboratory and the Center for Nanoscale Materials, a DOE Office of Science User Facility. The experimental setup consisted of small patches of graphene (a two-dimensional single-sheet form of pure carbon) sliding against a DLC-coated steel ball.
The graphene-DLC combination was registering a very low friction coefficient (a ratio that measures the force of friction between two surfaces), but the friction levels were fluctuating up and down for no apparent reason.
Argonne computational scientists then discovered the nanoscrolls and incorporated nanodiamond particles into their simulations to see if the hard material could help stabilize the nanoscrolls and make them more permanent.
The graphene patches spontaneously rolled around the nanodiamonds, which held the scrolls in place and resulted in sustained superlubricity.
The research team is in the process of seeking a patent for the hybrid material, which could potentially be used for applications in dry environments, such as computer hard drives, wind turbine gears, and mechanical rotating seals for microelectromechanical and nanoelectromechanical systems.
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