It turns out diamonds are graphene’s best friend. Scientists have found that adding very small diamonds to graphene creates a rare phenomenon called “superlubricity.” According to the researchers, their discovery could lead to improved engines, turbines and microelectromechanical systems.
The team, spearheaded by nanoscientist Ani Sumant, from the U.S. Department of Energy’s Argonne National Laboratory, combined various components including diamond nanoparticles, patches of graphene and a diamond-like carbon material that’s responsible for superlubricity.
When the diamond particles and the graphene patches rub against the carbon material, the graphene travels around the diamond particle. This movement, according to the scientists, looks a lot like a ball bearing on the nanoscopic level. “The interaction between the graphene and the diamond-like carbon is essential for creating the ‘superlubricity’ effect,” said researcher Ali Erdemir. “The two materials depend on each other.”
Friction at the atomic level
“You can think of it as like trying to slide two egg cartons against each other bottom-to-bottom,” said one of the study’s authors, Diana Berman, referring to the concept of friction at the atomic level. “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.”
The researchers developed the graphene-encapsulated diamond ball bearings (also known as “scrolls”) in order to apply the nanoscale superlubricity on a much larger scale. “A scroll can be manipulated and rotated much more easily than a simple sheet of graphene or graphite,” Berman explained.
The group achieved superlubricity in dry conditions, but could not do so in humid environments. This led them to call on atomistic calculations. “We observed that the scroll formation was inhibited in the presence of a water layer, therefore causing higher friction,” said co-author Subramanian Sankaranarayanan.
Benefits to the manufacturing sector
Sanket Deshmukh, a researcher added, “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 group’s research could potentially benefit various manufacturing sectors. “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,” said Sumant.
A paper based on the team’s research, titled “Macroscale superlubricity enabled by graphene nanoscroll formation,” was recently published in the journal Science Express. For more information, visit the Argonne National Laboratory’s website.