Near Zero Friction from Nanoscale Lubricants

Researchers have attained superlubricity, the near absence of friction, at a carbon-silica interface using nanodiamonds wrapped in graphene flakes.

Visualized model of a superlubricity (low-friction) system: gold = nanodiamond particles; red = graphene nanoscroll; green = underlying graphene on silica; black = diamond-like carbon surface. — Image courtesy of Argonne National Laboratory

The Science

Friction hampers the movement of all mechanical parts from engines, motors, etc. in transportation, oil refineries, power plants, and other facilities. At the Center for Nanoscale Materials, scientists built a system with virtually no friction. The system wraps graphene flakes around nanodiamonds that then roll between a diamond-like carbon-surface and graphene on silica. Such hard ball bearings wrapped in slippery Teflon tissue paper rolling between two surfaces reduces the friction to almost zero.

The Impact

The new system reduces contact areas and thus reduces friction to near zero. Creating a low-friction situation has the potential for substantial cost savings because friction accounts for most of the energy lost in moving mechanical assemblies and wear accelerates mechanical failures.

Summary

Superlubricity is the state in which the friction between two sliding surfaces is reduced to nearly zero. Friction and wear are the primary modes of mechanical energy dissipation in moving assemblies, thus it is highly desirable to minimize friction in real-world engineering-based applications. Structural defect issues, however, have stymied the realization of superlubricity. Previous studies have shown the beneficial effect of using graphene to reduce friction. A new study demonstrates that superlubricity can be achieved at the macroscale in a dry environment by the addition of nanodiamonds and graphene flakes .between two surfaces, one made of silicon and one made of diamond-like carbon. In this system, the coefficient of friction is just 0.004, and contact areas are reduced by more than 65%. Analysis of the wear debris revealed that the graphene flakes form nanoscroll-like features wrapping the nanodiamonds. Computer simulations show that more and more graphene flakes scroll with time, gradually reducing the contact area between the nanoscrolls and the diamond-like carbon surface, which allows superlubricity to be attained.

Contact

Anirudha Sumant
The Center for Nanoscale Materials, Argonne National Laboratory
sumant@anl.gov
(630) 252-4854

Kathleen Carrado Gregar
The Center for Nanoscale Materials, Argonne National Laboratory
kcarrado@anl.gov
(630) 252-7968

Funding

This research was carried out under an Argonne competitive Laboratory Directed Research and Development effort. Use of the Center for Nanoscale Materials (including synthesis, Raman, and JEOL TEM), an Office of Science User Facility, was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Use of the National Energy Research Scientific Computing Center, was supported by the DOE Office of Science under Contract No. DE-AC02-05CH11231. This research used tribological test facilities of the Energy Systems Division supported by the Vehicle Technologies Program of the DOE Office of Energy Efficiency and Renewable Energy under Contract No. DE-AC02-06CH11357. An award of computer time was provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the DOE Office of Science under Contract No. DE-AC02-06CH11357.

Publications

D. Berman, S.A. Deshmukh, S.K.R.S. Sankaranarayanan, A. Erdemir, and A.V. Sumant, “Macroscale superlubricity enabled by graphene nanoscroll formation.” Science 348, 1118 (2015). [DOI: 10.1126/science.1262024].