Scientists at the Department of Energy’s Oak Ridge National Laboratory have invented a coating that could dramatically reduce friction in common load-bearing systems with moving parts, from vehicle drive trains to wind and hydroelectric turbines. It reduces the friction of steel rubbing on steel at least a hundredfold. The novel ORNL coating could help grease a U.S. economy that each year loses more than $1 trillion to friction and wear — equivalent to 5% of the gross national product.
“When components are sliding past each other, there’s friction and wear,” said Jun Qu, leader of ORNL’s Surface Engineering and Tribology group. Tribology, from the Greek word for rubbing, is the science and technology of interacting surfaces in relative motion, such as gears and bearings. “If we reduce friction, we can reduce energy consumption. If we reduce wear, we can elongate the life span of the system for better durability and reliability.”
The ORNL coating’s superior slipperiness has staying power. Superlubricity persisted in tests of more than 500,000 rubbing cycles. Kumara tested the performances for continuous sliding over three hours, then one day and later 12 days. “We still got superlubricity,” he said. “It’s stable.”
Using electron microscopy, Kumara examined the mowed fragments to prove that tribological wear had severed the carbon nanotubes. To independently confirm that rubbing had shortened the nanotubes, ORNL co-author Lance used Raman spectroscopy, a technique that measures vibrational energy, which is related to the atomic bonding and crystal structure of a material.
He added, “Somewhere, you can find a scientist with expertise in carbon nanotubes, a scientist with expertise in tribology, a scientist with expertise in materials characterization. But they are isolated. Here at ORNL, we are together.”
ORNL’s tribology teams have done award-winning work that has attracted industrial partnerships and licensing. In 2014, an ionic anti-wear additive for fuel-efficient engine lubricants, developed by ORNL, General Motors, Shell Global Solutions and Lubrizol, won an R&D 100 award. ORNL’s collaborators were Qu, Huimin Luo, Sheng Dai, Peter Blau, Todd Toops, Brian West and Bruce Bunting. The Vehicle Technologies Office in DOE’s Office of Energy Efficiency and Renewable Energy, or EERE, sponsored the research.
Similarly, the work described in the current paper was a finalist for an R&D 100 award in 2020. And the researchers have applied for a patent of their novel superlubricity coating.
“Next, we hope to partner with industry to write a joint proposal to DOE to test, mature and license the technology,” Qu said. “In a decade we’d like to see improved high-performance vehicles and power plants with less energy lost to friction and wear.”
The title of the paper is “Macroscale superlubricity by a sacrificial carbon nanotube coating.”
ORNL’s Laboratory Directed Research and Development Seed Program provided the initial support to the proof-of-concept work. Then the Solar Energy Technologies Office and Vehicle Technologies Office in DOE’s EERE supported the follow-on research.
UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. — Dawn Levy
