Wednesday, June 17, 2015

Friction Banished by coating Diamonds with Graphene?

Diamonds are the hardest natural substances known. Combine them with graphene, and diamond nanoparticles are also incredibly slippery, which can be useful if you want to reduce friction.

Scientists at Argonne National Laboratory recently announced that the combination of tiny bits of diamond with the two-dimensional graphene created tiny structures that had superlubricity - meaning that the friction between them and another object dropped to near zero.
At the atomic level, friction occurs when atoms in materials that slide against each other become "locked in state," which requires additional energy to overcome.

Superlubricity was accomplished by combining nanodiamonds with sheets of graphene, which curl around the nanodiamonds to form ‘nanoscrolls’ that lubricate the two surfaces. As friction is the cause of massive energy waste in various devices, this discovery can be hugely beneficial for saving energy and money in a multitude of fields.
"The interaction between the graphene and the diamond-like carbon is essential for creating the 'superlubricity' effect," he said. "The two materials depend on each other."

Superlubricity has only been detected in extremely small samples as larger surfaces have imperfections that tend to get stuck as they slide. This is why creating superlubricity in a large sample is so unique.
Superlubricity was retained through testing of various conditions, like different temperatures, varying load on the surfaces, and increased velocity. The only exception came when they increased the relative humidity to 30%, which caused friction to increase dramatically, so this technique currently only works in dry, inert conditions. Water vapour can make its way into the space between the two surfaces, creating transient bonds that need to be broken to shift the surfaces.

The scientists are working on solving the issue, but even now this is a major find as it is the first time that superlubricity has been demonstrated for something other than two defect-free surfaces.

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