Researchers from Worcester Polytechnic Institute (WPI) and State University of New York (SUNY) Polytechnic Institute have shown that superlubricity—a state with virtually no friction that was once believed to only be achievable at nanoscale—can now be maintained at macroscale for extended time periods under regular atmospheric conditions by employing sustainably produced carbon coatings made from biowaste.

The findings could prove to be significant. In the automotive industry, more than 30% of fuel in passenger vehicles is used to overcome friction, so these novel coatings could help to improve fuel efficiency significantly. In manufacturing and industrial machinery, they could help to reduce wear and tear, leading to massive cost savings and decreasing the 1-4% of countries’ GDP that is spent on friction-related equipment issues. In electronic devices, friction at a minute scale can present large-scale challenges that coatings could help to alleviate.

A paper on their work is published in the journal Applied Materials Today.

Asumadu et al.

This paper discusses experimental and computational results of ultralow (near-zero) friction of carbon-coated metallic depositions on substrates of structural steels, Ti, and Ni alloys. The macroscale superlubricity was demonstrated and sustained over several cycles through structurally misoriented carbon coatings on the metallic surfaces. Carbon nanocrystals with variants of graphene footprints were deposited on these metallic surfaces using a novel high temperature biowaste treatment process.

The carbon nanocrystals deform, flatten, and coalesce in the wear tracks to form graphitic films leading to a superlubricious coefficient of friction of ∼0.003. A coating life of ∼150,000 cycles with reduced wear rates was obtained on Ni and steel substrates.

The experiments were validated with atomistic simulations providing mechanistic insights into the effects of the graphene variants on the observed frictionless conditions. The underlying mechanisms of the coating/substrate interactions contributing to the macroscale superlubricity are elucidated.

The implications of the current results are explored for designing robust and low-cost macroscale superlubricious carbon coatings on metallic substrates. Biowaste is a carbon source within a circular economy that uses material recycling to reduce the global carbon footprint.

—Asumadu et al.

Resources

• Tabiri Kwayie Asumadu, Mobin Vandadi, Desmond Edem Primus Klenam, Kwadwo Mensah-Darkwa, Emmanuel Gikunoo, Samuel Kwofie, Nima Rahbar, Winston Oluwole Soboyejo, “Robust macroscale superlubricity on carbon-coated metallic surfaces,” Applied Materials Today, Volume 37, 2024, doi: 10.1016/j.apmt.2024.102140