"I remember Sanket calling me and saying 'you have got to come over here and see this. I want to show you something really cool,'" said Subramanian Sankaranarayanan, Argonne computational nanoscientist, who led the simulation work at the ALCF, a DOE Office of Science User Facility.
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. These so-called nanoscrolls represented a completely new mechanism for superlubricity, a state in which friction essentially disappears.
"The nanoscrolls combat friction in very much the same way that ball bearings do by creating separation between surfaces," said Deshmukh.
Desmukh and Sankaranarayanan used Mira, ALCF's 10-petaflops IBM Blue Gene/Q supercomputer, to discover why friction levels fluctuated on the hybrid graphene-DLC material being studied. This is how they discovered the graphene nanoscrolls. While the nanoscrolls were intact friction was low, but the pressure placed on them meant that they would cave in, increasing the friction.
The researchers incorporated nanodiamond particles into their simulations. The graphene patches spontaneously rolled around the nanodiamonds, which held the scrolls in place and resulted in sustained superlubricity.
"The beauty of this particular discovery is that we were able to see sustained superlubricity at the macroscale for the first time, proving this mechanism can be used at engineering scales for real-world applications," Sankaranarayanan said.
Considering that nearly one-third of every fuel tank is spent overcoming friction in automobiles, a material that can achieve superlubricity would greatly benefit industry and consumers alike. Such materials could also help increase the lifetime of countless mechanical components that wear down due to incessant friction.
