The direct observation of the anti-wear action of ZDDP

Sheasby, J. S.; Caughlin, T.A.

doi:10.1016/s0167-8922(08)70646-1

Cited by 8 publications

(3 citation statements)

References 6 publications

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“…One particularly daunting aspect of the generally daunting ZnDTP literature is that virtually every weapon in the surface-analysis arsenal has been brought to bear upon the problem, including Auger electron spectroscopy (AES) [28,29], X-ray photoelectron spectroscopy (XPS) [30,31], near-edge X-ray absorption fine structure (NEXAFS, or XANES) [30,[32][33][34][35][36][37][38][39], Fourier transform infrared spectroscopy (FTIR) [40], time-of-flight secondary-ion mass spectroscopy (ToF-SIMS)[41], scanning force microscopy (SFM) [42,43], the surface forces apparatus (SFA) [27,44], transmission electron microscopy (TEM) [39], scanning electron microscopy (SEM) [45], extended X-ray absorption fine structure (EXAFS) [36] and profilometry [45], as well as in situ tribometry methods such as the direct-observation wear machine (DOWM) [46] and ultra-thin film interferometry [47].…”

Section: Analytical Approachesmentioning

confidence: 99%

Surface Chemistry in Tribology

and¹,

Spencer²

2005

Wear – Materials, Mechanisms and Practice

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Section: Analytical Approachesmentioning

confidence: 99%

Surface Chemistry in Tribology

and¹,

Spencer²

2005

Wear – Materials, Mechanisms and Practice

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“…One particularly daunting aspect of the generally daunting ZnD TP litera ture is that virtually every weapon in the surface-analysis arsenal has been brought to bear upon the problem, including Auger electron spectroscopy (AES) [28,29], X-ray photoelectron spectroscopy (XPS) [30,31], near-edge X-ray absorption ®ne structure (N EXAF S, or XAN ES) [30, 32±39], F ourier transform infrared (F TIR ) spectroscopy [40], time-ofight secondary-ion mass spectroscopy (ToF -SIM S) [41], scanning force microscopy (SF M ) [42,43], the surface forces apparatus (SF A) [27,44], transmission electron microscopy (TEM ) [39], scanning electron microscopy (SEM ) [45], extended X-ray absorption ®ne structure (EXAF S) [36] and pro®lometry [45], as well as in situ tribometry methods such as the directobservation wear machine (D OWM ) [46] and ultra-thin ®lm interferometry [47].…”

Section: Analytical Approachesmentioning

confidence: 99%

Surface chemistry in tribology

Gellman

Spencer²

2002

Proceedings of the Institution of Mechanical Engineers, Part J:

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IntroductionIn general, the twentieth century marked the first major incursion of chemists into the world of tribology. Driven partly by the need for improved lubricants for new machines developed in the first few decades of the century, and partly by new analytical capabilities, lubricant chemists and tribochemists were to become full partners in the science of tribology. In this review we cover a number of topics in surface chemistry in tribology, which serve both to illustrate some of the successes in tribochemical research over the past decades, and also to show that much work remains to be done before true, first-principles tribochemistry-based lubricant and tribopair design can begin. Boundary Lubrication and Oiliness AdditivesIn an ideal world, lubricated sliding surfaces are separated by a stable fluid film of lubricant, which effectively lowers friction and prevents wear, holding the surfaces apart by virtue of its fluid-mechanical properties. The friction coefficient in such a hydrodynamically lubricated bearing is proportional to ηU/W, where U is the relative sliding speed of the surfaces, W the normal load supported by the bearing and η the Newtonian viscosity [1]. At low sliding speeds (e.g upon startup) and/or higher forces, however, the friction coefficient varies in a more complex way (Figure 1) and at the lowest speeds and friction forces can be 2 orders of magnitude higher than under hydrodynamic lubrication conditions. This is the regime of "boundary lubrication", where fluid films have given way to thin layers that serve as the active lubricants, and the realm of pure engineering (hydrodynamic lubrication) has given 2 way to the complex world of surface chemistry under confinement. Boundary lubrication is clearly of vital importance, since it is the mechanism in operation under the most extreme of tribological conditions. Understanding boundary lubrication, however, has been a challenge to tribochemists over the last century, with light appearing at the end of the tunnel only quite recently. Monolayers, Multilayers and soapsIt was noticed in the 1920s that certain lubricants possessed a quality designated "oiliness", which, independent of their viscosity, led to better lubrication at low sliding speeds [2][3][4]. Generally, these oily lubricants tended to be those of natural origin, such as castor oil, containing long-chain oxygenated organic compounds (esters and acids), which have surfactant properties, and are not usually present in their mineral oil counterparts. It was shown that these oxygenated molecules could, by themselves, reduce friction considerably between sliding surfaces, their effectiveness depending on their molecular weight [5] (Figure 2). Hardy developed a monolayer theory of boundary lubrication (Figure 3), whereby he postulated that, under boundary conditions, the sliding surfaces were held apart by adsorbed, oriented monolayers of polar molecules, which form a plane of low shear strength, thus lowering friction and affording protection of the surfaces.3 Figure 2. Depe...

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“…A few examples may be cited. Film formation during sliding has been investigated by electrical contact resistance measurement (3), (4) and by direct observation (5). Elemental composition of antiwear films has been reported for both films from bench tests (3) and engine experiments (6).…”

Section: Retiredmentioning

confidence: 99%