Robust microscale superlubricity under high contact pressure enabled by graphene-coated microsphere

Area of Science:

• Materials Science
• Tribology
• Nanotechnology

Background:

• Superlubricity in graphite and graphene is of significant interest.
• Achieving long-lasting superlubricity under high normal load in ambient conditions remains a challenge.

Purpose of the Study:

• To directly measure sliding friction between graphene and hexagonal boron nitride (h-BN) under high contact pressures.
• To investigate the factors contributing to robust superlubricity in two-dimensional (2D) materials.

Main Methods:

• Utilized a graphene-coated microsphere (GMS) probe prepared via metal-catalyst-free chemical vapor deposition.
• Performed direct friction measurements under local asperity contact pressures up to 1 GPa.
• Evaluated friction at arbitrary relative surface rotation angles and varying relative humidity.

Main Results:

• Achieved an exceptionally low and robust friction coefficient of 0.003.
• Demonstrated superlubricity insensitive to relative humidity up to 51% RH.
• Attributed ultralow friction to sustainable overall incommensurability from randomly oriented graphene nanograins.

Conclusions:

• Realized microscale superlubricity between graphene and h-BN under demanding conditions.
• The findings suggest potential for extending this superlubricity to various other 2D layer sliding systems.
• This work paves the way for developing advanced low-friction applications in nanotechnology.