COLL 112 |
| Jose J Nainaparampil, K. C. Eapen, and J. S. Zabinski. AFRL/MLBT, Air Force Research Laboratory, Wright Patterson Air Force Base, Ohio, Bldg. 654, Rm 136, 2941 P Street, Wright Patterson AFB, OH 45433 |
| Monolayer films applied to electrostatically actuated micromotors provide substantial improvement in their performance and life. However, the statistical distribution of life improvement is large, rendering definition of a reliable life expectancy difficult. This may be caused by breakdown of the applied monolayer. Failure mechanisms of monolayer films must be studied in detail to understand the basic phenomena driving the instability. It has been noted that the molecular weight, entanglement of molecules to asperities, time duration dependent interactions between asperities and monolayers and surface electromigration can influence the failure of monolayer films. Thin polymer films undergo similar failures under similar influences (1). Tribological stressing, diffusion at increased temperature may also cause the monolayer film to fail. In this study, atomic force microscopy and related techniques are used to analyze the lifetime variation of lubricant monolayers with different functional groups and chain lengths on gold, silicon and graphite. Monolayer films are formed using the dip method and the migration and breakdown of the films are studied as a function of tribo-stressing, temperature, and voltage variation. The results of these studies and the failure mechanisms that they suggest will be presented. 1. D. Michel, S. Kopp-Marsaudon and J. P. Aimè, Tribol. Letts. 4 1998, 75 |
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Molecular Tribology
Division of Colloid and Surface Chemistry |