A new material blend that has a rare chariacteristic called “superlubricity” has been created use miniscule diamonds and graphene, by scientists at Argonne National Laboratory.
A five-person Argonne team combined small patches of graphene, the two-dimensional single-sheet form of pure carbon, diamond nanoparticles, and a diamond-like carbon material to generate superlubricity, a very desirable material property in which friction drops to near zero.
According to Ali Erdemir of Argonne’s Energy Systems Division, the graphene patches and diamond particles rub up against a large diamond-like carbon surface, and the graphene rolls itself around the diamond particle, creating something similar to a ball bearing on the nanoscopic level:
“The interaction between the graphene and the diamond-like carbon is essential for creating the ‘superlubricity’ effect. The two materials depend on each other.”
Friction results when atoms in materials that slide against each other become “locked in state,” which requires additional energy to overcome. Said Diana Berman, postdoc researcher at Argonne’s Center for Nanoscale Materials, and a study author:
“You can think of it as like trying to slide two egg cartons against each other bottom-to-bottom. There are times at which the positioning of the gaps between the eggs – or in our case, the atoms – causes an entanglement between the materials that prevents easy sliding.”
Through fabricating the graphene-encapsulated diamond ball bearings (“scrolls”), the team found a way to translate the nanoscale superlubricity into a macroscale phenomenon.
“A scroll can be manipulated and rotated much more easily than a simple sheet of graphene or graphite,” Berman said.
Since the scrolls alter orientation in the sliding process, enough diamond particles and graphene patches prevent the two surfaces from becoming locked in state. The team used large-scale atomistic computations on the Mira supercomputer at the Argonne Leadership Computing Facility to confirm that the effect could be seen not merely at the nanoscale, but also at the macroscale.
The field of tribology has always been concerned with ways to reduce friction, and lowering the energy demands of different mechanical systems. But superlubricity is seen as a very difficult proposition. Sanket Deshmukh, another CNM postdoctoral researcher on the study, explained:
“Everyone would dream of being able to achieve superlubricity in a wide range of mechanical systems, but it’s a very difficult goal to achieve.
The knowledge gained from this study will be crucial in finding ways to reduce friction in everything from engines or turbines to computer hard disks and microelectromechanical systems.”
Diana Berman, Sanket A. Deshmukh, Subramanian K. R. S. Sankaranarayanan, Ali Erdemir, and Anirudha V. Sumant
Macroscale superlubricity enabled by graphene nanoscroll formation
Science 1262024 14 May 2015 DOI:10.1126/science.1262024