Ultrahigh Vacuum Boundary Lubrication of the Cu-Cu Interface by 2,2,2-Trifluoroethanol

Autor:	Andrew J. Gellman, Christopher F. McFadden
Rok vydání:	1995
Předmět:	Normal force Chemistry Analytical chemistry Surfaces and Interfaces Condensed Matter Physics Atmosphere Shear (sheet metal) chemistry.chemical_compound Adsorption 2 2 2-Trifluoroethanol Monolayer Electrochemistry General Materials Science Boundary lubrication Spectroscopy Tribometer
Zdroj:	Langmuir. 11:273-280
ISSN:	1520-5827 0743-7463
DOI:	10.1021/la00001a046
Popis:	An ultrahigh vacuum (UHV) force measurement device has been used to study friction between Cu(111) surfaces separated by adsorbed films of 2,2,2-trifluoroethanol (CF 3 CH 2 OH) ranging in coverage from 0 to 15 monolayers (ML). The instrument is designed such that both samples may be prepared and characterized under UHV conditions and then brought into contact and sheared relative to one another without exposure to atmosphere. Both shear and normal forces generated at the metal-metal interface are measured simultaneously during sliding. The shearbehavioroftheclean Cu(111)-Cu(111) interface is characterized by high, erratic friction forces with a static friction coefficient of μ s =4.6±1.1. The presence of adsorbed trifluoroethanol at the interface does not affect the friction coefficient until the trifluoroethanol coverage reaches approximately 1 ML, after which the friction coefficient is significantly reduced. The static friction coefficient gradually decreases to a limiting value of μ s =0.38±0.07 at trifluoroethanol coverages greater than approximately 8 ML. The friction coefficient was found to be independent of normal force (F n ) and sliding velocity over the ranges accessible with the UHV tribometer (F n =2-80 nM, velocity=0.5-200 μm/s)
Databáze:	OpenAIRE
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