List of Events
Martin Weiner Lecture Series
Department of Physics Colloquium
For Abelson Room 131, 4 p.m. events only:
Refreshments at 3:30 p.m. outside Abelson 131
Dec 3, 2009
MRSEC Seminar Marina Ruths, Dept of Chemistry,University of Mass Lowell
5 p.m.
Room: Abelson 333
Title: "Tribology of Confined Molecularly Thin Films"
Abstract: In boundary lubricated contacts, different friction responses are observed when the strength of adhesion between the sliding surfaces is altered. In my group, we explore this by studying the adhesion and friction of self-assembled monolayers (aromatic thiols and silanes, and fatty acids) in single-asperity contact with the Surface Forces Apparatus (SFA) and with an Atomic Force Microscope (AFM). The strength of the adhesion is modified by immersing the surfaces in dry N2 gas or in ethanol. Low adhesion gives a linear dependence of the friction force on load, whereas high adhesion gives an apparent dependence on the size of the contact area (which increases sublinearly with load). The reduction of the area-dependence in ethanol allows a direct, quantitative comparison of the load-dependent friction of surfaces whose radius of curvature differs by 5−6 orders of magnitude. We use a recent contact mechanics model for adhesive, layered systems (the extended Thin-Coating Contact Mechanics model) to evaluate the area-dependence of the friction of monolayers of different stiffness (purely aromatic and purely aliphatic) probed with AFM.
Host: Seth Fraden
Dec 10, 2009
MRSEC Seminar TBD
Luca Giomi, Brandeis University
5 p.m.
Room: Abelson 333
Host: Seth Fraden