Researchers from the US Department of Energy's Argonne National Laboratory have created a new combination material from graphene and diamonds that's able to almost entirely overcome friction. The property, known as superlubricity, is highly sought after for its potential use in a wide range of mechanical systems.
Zooming down to an atomic level, friction is caused by atoms locking together, making it difficult for them to pass over one another. It's like sliding the bases of two egg cartons over one another. They'll often get entangled together during the process.
In an attempt to create a material that all but eliminates this effect, the small team of researchers combined three key building blocks – diamond nanoparticles, a diamond-like carbon surface and numerous small patches of graphene.
The latter is an extremely strong, conductive form of pure carbon that's just one atom thick, forming a two-dimensional hexagonal lattice. We've seen a wide range of promising potential uses for the material, including textiles, lighting and body armor, with researchers currently clamoring to come up with a viable method for large scale production.
Combining the three materials, the Argonne National Laboratory researchers observed the graphene patches interacting with the diamond nanoparticles as they rubbed up against the diamond-like carbon surface. In essence, the graphene rolled itself around the diamond particles to create tiny ball bearing-like structure, which the researchers call nanoscrolls.
These nanoscrolls are able to change orientation during the sliding process, thereby preventing two surfaces from becoming locked together. The researchers performed tests to prove this was the case at the nanoscale level, but also used the Mira supercomputer at the Argonne Leadership Computing Facility to run large-scale atomistic computations, suggesting that the effect will also work on the macroscale, in theory at least.
Though these results were extremely promising, the team did encounter one confusing issue. While the diamond/graphene combination material performed its job admirably under dry conditions, superlubricity was not maintained when it was introduced to a humid environment.
To solve the mystery, the researchers turned once again to atomistic calculations that revealed that the presence of a water layer inhibited nanoscroll formation, causing higher levels of friction as a result.
The team believes that the findings could have a significant impact on the field.
"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," said researcher Sanket Deshmukh. "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."
The results of the research were published in the journal Science Express.
Source: Argonne National Laboratory
