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Advances in Tribology
Volume 2011 (2011), Article ID 929642, 6 pages
Research Article

Transfer Layers: A Comparison across SWNTs, DWNTs, Graphite, and an Ionic Fluid

1Department of Energy and Mineral Engineering and The EMS Energy Institute, The Pennsylvania State University, University Park, PA 16802, USA
2The Tribology and Mechanical Components Branch, National Aeronautics and Space Administration, Glenn Research Center, Cleveland, OH 44135, USA

Received 5 September 2010; Accepted 7 March 2011

Academic Editor: Arvind Agarwal

Copyright © 2011 Randy L. Vander Wal et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Lubrication is the science of friction at moving interfaces. Nanomaterials acting as interfacial modifiers can minimize friction and thereby improve energy efficiency. To test this hypothesis, single- (SWNT) and double-walled (DWNT) carbon nanotubes and an ionic fluid are tested individually and compared to SWNTs and graphite as additives within the ionic fluid. The minimum coefficient of friction is correlated with the longest lifetime using a ball-on-disc tribometer, in air, at atmospheric pressure. Results are interpreted in terms of the nanotubes' mechanical properties and the formation of transfer layers upon the tribosurfaces.