AVS 56th International Symposium & Exhibition
    Tribology Focus Topic Tuesday Sessions
       Session TR+SS-TuA

Paper TR+SS-TuA7
Nanotribology at Cryogenic Temperatures

Tuesday, November 10, 2009, 4:00 pm, Room B2

Session: Surface Science for Tribology
Presenter: S.S. Perry, University of Florida
Authors: S.S. Perry, University of Florida
X. Zhao, University of Florida
S.R. Phillpot, University of Florida
G. Sawyer, University of Florida
S.B. Sinnott, University of Florida
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The temperature dependence of the kinetic friction between a silicon nitride probe tip and a number of crystalline surfaces has been evaluated through atomic force microscopy measurements performed under an ultrahigh vacuum environment over the temperature range 140-750 K. Surfaces interrogated include highly oriented pyrolytic graphite, molybdenum disulfide, and lead sulfide. A relatively weak dependence on temperature is observed in the friction measured between 300 K and 750 K. As temperature decreases below ambient temperatures, a sharp increase in friction is observed for all surfaces, however with variations in the temperature threshold. Collectively, these results obtained from fundamental interfaces are consistent with an activated mechanism of energy dissipation during sliding. An Arhennius analysis of the temperature dependent friction over this range yields different effective activation energies, ranging from 0.1-0.4 eV for the thermally activated stick-slip motion of the probe tip on this surface. As temperature is reduced further, a distinct transition to a largely athermal behavior is detected and is shown to result from the onset of interfacial wear, entailing an alternative energy dissipation pathway.