Molecular Layering in Nanometer-Confined Lubricants

Krass, Marc-Dominik; Krämer, Günther; Dellwo, Ulrike; Bennewitz, Roland

doi:10.1007/s11249-018-1041-y

Cited by 20 publications

(13 citation statements)

References 23 publications

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“…Previous experimental studies on mica suggest an orientation of the interfacial hexadecane molecules parallel to the substrate. 35 This is also supported by molecular dynamics and Monte Carlo simulations that reveal well-ordered hexadecane structures when nanoconfined between two mica surfaces. 36,37 The existence of in-plane order and interlayer correlation may result in longrange correlations in the confined film 34 with humidity adversely affecting the hydrocarbon adsoprtion.…”

Section: Introductionmentioning

confidence: 63%

Impact of water on the lubricating properties of hexadecane at the nanoscale

Cafolla

Voïtchovsky

2020

Nanoscale

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Section: Introductionmentioning

confidence: 63%

Impact of water on the lubricating properties of hexadecane at the nanoscale

Cafolla

Voïtchovsky

2020

Nanoscale

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“…The TFL model with a nanosandwich structure consisting of an adsorbed layer, an ordered-molecule layer, and a fluid layer has been verified. Krass et al [110] observed that on the graphite surface, the confined molecules are parallel to the surface orientation of all liquids, resulting in a layer with the thickness equivalent to the diameter of the alkyl chain. The confined cetane molecules on the surface of mica are also parallel to the surface, while the molecules in the first layer of 1-hexadecene and PAO take a more upright direction.…”

Section: Oil-based Lubricationmentioning

confidence: 99%

A review of recent advances in tribology

et al. 2020

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The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

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“…This result is not surprising as a heavily branched hydrocarbon such as 2,6,10,15,19,23-hexamethyltetracosane (squalane) has previously produced liquid layers separated by 0.6 nm on graphite. 25 A recent AFM study 26 reported averaged layer distances of 0.42 and 0.47 nm in a larger PAO, decene tetramers, on graphite and steal, respectively.…”

Section: Resultsmentioning

confidence: 99%

Nanometer-Scale Distribution of a Lubricant Modifier on Iron Films: A Frequency-Modulation Atomic Force Microscopy Study Combined with a Friction Test

et al. 2019

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Liquid lubricants used in mechanical applications are low-vapor-pressure hydrocarbons modified with a small quantity of polar compounds. The polar modifiers adsorbed on the surface of sliding solids dominate the friction properties when the sliding surfaces are in close proximity. However, a few methods are available for the characterization of the adsorbed modifiers of a nanometer-scale thickness. In this study, we applied frequency-modulation atomic force microscopy to evaluate the vertical and lateral density distributions of the adsorbed modifier in a real lubricant, namely, poly-α-olefin (PAO) modified with an orthophosphoric acid oleyl ester. The liquid-induced force on the probing tip was mapped on a plane that was perpendicular to the lubricant–iron interface with a force sensitivity on the order of 10 pN. The PAO in the absence of the ester modifier was directly exposed to the film, which produced a few liquid layers parallel to the film surface with layer-to-layer distances of 0.6–0.7 nm. A monomolecular layer of the modifier was intermittently adsorbed with increasing ester concentration in the bulk lubricant, with complete coverage seen at 20 ppm. The C18H35 chains of the oleyl esters fluctuating in the lubricant produced a repulsive force on the tip, which monotonically decayed with the tip-to-surface distance. The dynamic friction coefficient of sliding steel–lubricant–steel interfaces, which was separately determined using a friction tester, was compared with the force map determined on the iron film immersed in the corresponding lubricant. The complete monomolecular layer of the ester modifier on the static lubricant–iron boundary is a requirement for achieving smooth and stable friction at the sliding interface.

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Molecular Layering in Nanometer-Confined Lubricants

Cited by 20 publications

References 23 publications

Impact of water on the lubricating properties of hexadecane at the nanoscale

Impact of water on the lubricating properties of hexadecane at the nanoscale

A review of recent advances in tribology

Nanometer-Scale Distribution of a Lubricant Modifier on Iron Films: A Frequency-Modulation Atomic Force Microscopy Study Combined with a Friction Test

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