Distinguished Seminar: Atomic-scale processes in friction and wear

October 1, 2013

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Robert Carpick, PhD

Professor and Chair, Mechanical Engineering and Applied Mechanics (MEAM)
University of Pennsylvania

Friday, Oct. 25th, 2013, 3:00 pm

Warnock Engineering Bldg. (WEB) 2230; Reception to follow at 4:00 pm

Abstract:  I will discuss recent atomic force microscopy studies of nanoscale single asperity contacts that reveal surprising new behavior and insights. First, the behavior of nanoscale contacts with truly 2-dimensional materials will be discussed. For contacts to graphene and other 2-D materials, we find that the friction force exhibits a significant dependence on the number of 2-D layers [1]. An even stronger effect occurs when graphene is fluorinated. The results are interpreted in the context of the Prandtl-Tomlinson model of stick-slip friction.

I will then discuss new insights into nanoscale wear. We characterize wear with unprecedented resolution using in-situ tests inside of a transmission electron microscope. For silicon probes slid against diamond, the shape evolution and volume loss due to wear closely fit a kinetic model based on stress-assisted bonding mechanisms [2]. This allows new insights to be gained about the kinetics of atomic-scale wear [3].

[1] Lee, C., Li, Q., Kalb, W., Liu, X.-Z., Berger, H., Carpick, R.W. and Hone, J. “Frictional Characteristics of Atomically-Thin Sheets,” Science, 328, 2010, 76-80.
[2] Jacobs, T.D. and Carpick, R.W. “Nanoscale Wear as a Stress-Assisted Chemical Reaction,” Nature Nanotech., 8, 2013, 108-112.
[3] Jacobs, T.D., Gotsmann, B., Lantz, M.A. and Carpick, R.W. “On the Application of Transition State Theory to Atomic-Scale Wear,” Tribol. Lett., 39, 2010, 257-271

Bio: Robert Carpick is Professor and Chair of the Dept. of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania. Previously, he was a faculty member at the University of Wisconsin-Madison (2000-2007). He received his B.Sc. from the University of Toronto (1991), and his Ph.D. from the University of California at Berkeley (1997), both in Physics, and was a postdoc at Sandia National Laboratory (1998-1999). He studies nanotribology, nanomechanics, and scanning probes. He received the 2009 Newkirk award of the ASME, and is a Fellow of the American Physical Society. He has authored over 100 peer-reviewed journal publications.