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Title: Frictional characteristics of molecular length ultra-thin boundary adsorbed films
Authors: Ku, I.S.Y.
Chong, W.W.F.
Reddyhoff, T.
Rahnejat, Homer
Keywords: Ultra-thin boundary films
Thermal activation energy
Solvation
Friction
Issue Date: 2015
Publisher: © Springer
Citation: KU, I.S.Y. ...et al., 2015. Frictional characteristics of molecular length ultra-thin boundary adsorbed films. Meccanica, 50(7), pp. 1915-1922.
Abstract: © 2015, Springer Science+Business Media Dordrecht. The paper presents measurements of friction of any ultra-thin film entrained into the contact of a pair of very smooth specimen subjected to entrainment in a converging micro-wedge of a special-purpose micro-tribometer. An ultra-thin film is expected to form at the boundary solids through adsorption of boundary active molecules. Fluids with linear and branched molecules are used in the investigation. It is found that the frictional characteristics of these films can be adequately described through use of Eyring thermal activation energy and a potential energy barrier to sustain conjunctional sliding motion. The combined experimental measurement and the simple activation energy approach shows that the thin molecular adsorbed films act like hydro Langmuir–Blodgett layers, the formation and frictional characteristics of which are affected by the competing mechanisms of adsorption, forced molecular re-ordering and discrete-fashion drainage through the contact by the solvation effect. This process is a complex function of the contact sliding velocity as well as a defined Eyring activation density (packing density of the molecules within the conjunction). It is shown that the contribution of solvation to friction is in the form of energy expended to eject layers of lubricant out of the contact, which unlike the case of micro-scale hydrodynamic films, is not a function of the sliding velocity.
Description: The final publication is available at Springer via http://dx.doi.org/10.1007/s11012-015-0186-0
Sponsor: The authors acknowledge sponsorship provided by the EPSRC through Grant Numbers EP/D04099X and EP/L001624/1 (covering experimental work) along with the EPSRC ENCYCLOPAEDIC program grant (covering theoretical work).
Version: Accepted for publication
DOI: 10.1007/s11012-015-0186-0
URI: https://dspace.lboro.ac.uk/2134/26334
Publisher Link: http://dx.doi.org/10.1007/s11012-015-0186-0
ISSN: 0025-6455
Appears in Collections:Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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