Tunable friction behavior of oriented carbon nanotube films
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Measured friction coefficients of carbon nanotubes vary widely from μ < 0.1–μ > 1.0 [1, 2, 3, 4, 5, 6], while theoretical studies suggest intrinsically high friction coefficients, approaching unity . Here we report that measured friction coefficients of MWNT films are strong functions of surface chemistry and temperature, but are not dependent on the presence of water vapor. We hypothesize that the origin of the temperature dependence arises from the interaction of the surface chemical groups on the nanotubes [8, 9, 10, 11, 12] and rubbing counterface. The friction coefficient of individual films can be easily tuned by changing the surface temperature and chemistry of either the countersurface or the nanotubes, we have demonstrated the ability to create and control high and low friction pairs through plasma treatments of the nanotube films with argon, hydrogen, nitrogen, and oxygen. This behavior is completely reversible, and when coupled with the superior strength, thermal, and electrical properties of nanotubes, provides a versatile tunable, multifunctional tribological system.
Keywordscarbon nanotubes coefficient of friction micro-tribology engineered surfaces
This material is based upon an AFOSR-MURI grant FA9550–04–1-0367. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the Air Force Office of Scientific Research.
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