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Friction of Octadecyltrichlorosilane Monolayer Self-Assembled on Silicon Wafer in 0% Relative Humidity

Khatri, Om P and Biswas, Sanjay K (2007) Friction of Octadecyltrichlorosilane Monolayer Self-Assembled on Silicon Wafer in 0% Relative Humidity. In: Journal of Physical Chemistry C, 111 (6). pp. 2696-2701.

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Self-assembled octadecyltrichlorosilane monolayers on silicon wafer were slid against a smooth steel ball at a 350 to 750 MPa contact pressure and in 0.02 to 1 cm/s velocity ranges in a nominal 0% relative humidity environment. The friction was found to increase monotonically over sliding time stretching to 20 h. Within a framework that the friction is related to the generation of strains and defects at the molecular scale we explore the dissipation process in some detail by varying the normal load, velocity, and a priori defect population in the monolayer. The results indicate that the rate of friction change is significantly influenced by the relative magnitude of the time allowed to the molecules to relax in intermittent contact and the characteristic relaxation time that reflects the collective response of a large number of molecules in contact at a given time. We propose a simple model to account for the observations, where the friction at the commencement of sliding is governed by backbone stiffness. This process for all practical purposes is independent of sliding time. The kinetic friction on the other hand is related to time-dependent defect generation and accumulation at the terminal end and is found to consist of reversible and irreversible components. The latter provides the monolayer with a memory of its previous loading history.

Item Type: Journal Article
Publication: Journal of Physical Chemistry C
Publisher: American Chemical Society
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Mechanical Sciences > Mechanical Engineering
Date Deposited: 03 Jun 2008
Last Modified: 19 Sep 2010 04:45
URI: http://eprints.iisc.ac.in/id/eprint/14154

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