Giving Friction the Slip with New Carbon Films

Newswise — The Science

In engines, motor oil additives improve lubricity, although they can damage the environment. Argonne National Laboratory scientists discovered new coatings for engine parts with exceptional anti-wear properties. Advanced computational simulations, performed in part at Argonne’s Center for Nanoscale Materials, traced the origin of the anti-wear properties to new catalytic phenomena possible only under the extreme conditions afforded by friction. Catalysts are materials that speed up chemical reactions. Further knowledge about catalytic mechanisms coupled with the predictive power of simulation may enable the design of new mechanical coatings going forward.

The Impact

New catalytically active coatings eliminate the need for environmentally hazardous anti-wear additives used commonly in lubricating oils for engines. Furthermore, they allow the combination of fluid and solid tribofilms -- named after tribology, the study of friction -- to be continually renewed during operation.

Summary

Tribology -- the study of friction, wear, and lubrication -- is critical to the efficiency and durability of engines and other moving metal parts. Tests have revealed new tribofilms containing diamond-like carbon reduce friction by 25 to 40 percent and that wear is reduced to nearly zero. But it took theoretical insight enhanced by massive computing resources to fully understand what was happening. Researchers ran large-scale simulations on powerful supercomputers to understand what was happening at the atomic level. They determined that catalyst metals in the nanocomposite coatings were stripping hydrogen atoms from the hydrocarbon chains of the lubricating oil, and then breaking the chains down into smaller segments. The smaller chains join together under pressure to create the highly durable diamond-like carbon tribofilms. Theorists explored the origins of the catalytic activity to understand how catalysis operates under the extreme heat and pressure in an engine. By gaining this understanding, researchers may be able to predict which catalysts will create the most advantageous tribofilms.

Funding

Work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies and Advanced Manufacturing Offices under contract DE-AC02-06CH11357. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357. This research also used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science user facility supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-05CH11231. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry measurements were carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities, University of Illinois.

Publications

A. Erdemir, G. Ramirez, O.L. Eryilmaz, B. Narayanan, Y. Liao, G. Kamath, and S.K.R.S. Sankaranarayanan, “Carbon-based tribofilms from lubricating oils.” Nature 536, 67 (2016). [DOI: 10.1038/nature18948]