Authors: N Argibay W G Sawyer
Publish Date: 2012/04/05
Volume: 46, Issue: 3, Pages: 337-342
Abstract
This paper presents an experimental study correlating frictional behavior with in situ voltammetry for a unidirectional sliding contact between a hemispherical tipped alumina probe and a flat rotating copper counterface maximum Hertzian contact pressure of 68 MPa and sliding speed of 10 mm/s The contact was immersed in an aqueous 01 M Na2CO3 solution pH ∼11 where the copper counterface acted as the working electrode in a potentiostat controlled threeelectrode cell a coiled Pt wire was used as the counter electrode and a saturated calomel electrode SCE as the reference Clear and reproducible trends were found between friction coefficient and published data suggesting the onset of particular redox reactions graphically presented in a frictional voltammetry plot At anodic potentials primarily associated with the formation of copperI oxide Cu2O V vs SCE ∼−025 the measured friction coefficient was in the range μ ∼04–05 At cathodic potentials primarily associated with the formation of CuO CuOH2 and CuCO3 V vs SCE ∼−010 the friction coefficient transitions to the range μ ∼07–10 At sustained cathodic potentials associated with reduction of the native copper oxide Cu2O V vs SCE ∼−065 the friction coefficient is observed to fluctuate between μ ∼02 and 05 arguably a result of exposure of bare copper due to nonuniform reduction fractional coverage of Cu2O
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