Atomic-scale sliding friction on a contaminated surface

Ouyang, Wengen; Wijn, Astrid S. de; Urbakh, Michael

doi:10.1039/c7nr09530a

Cited by 29 publications

(27 citation statements)

References 45 publications

(67 reference statements)

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“…Since the experiments were conducted under N 2 atmosphere, the amount of adsorbed molecules is very low. Under these conditions, it is reasonable to assume that the friction force is proportional to the amount of molecules adsorbed at the edges [43,44]. To estimate the effect of temperature on the amount of adsorbed molecules, we used a classical Langmuir adsorption model for two types of molecules [24,[45][46][47].…”

Section: Model Simulationsmentioning

confidence: 99%

Temperature and velocity dependent friction of a microscale graphite-DLC heterostructure

Gongyang

Ouyang

et al. 2019

Friction

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One of the promising approaches to achieving large scale superlubricity is the use of junctions between existing ultra-flat surface together with superlubric graphite mesas. Here we studied the frictional properties of microscale graphite mesa sliding on the diamond-like carbon, a commercially available material with a ultra-flat surface. The interface is composed of a single crystalline graphene and a diamond-like carbon surface with roughness less than 1 nm. Using an integrated approach, which includes Argon plasma irradiation of diamond-like carbon surfaces, X-ray photoelectron spectroscopy analysis and Langmuir adsorption modeling, we found that while the velocity dependence of friction follows a thermally activated sliding mechanism, its temperature dependence is due to the desorption of chemical groups upon heating. These observations indicate that the edges have a significant contribution to the friction. Our results highlight potential factors affecting this type of emerging friction junctions and provide a novel approach for tuning their friction properties through ion irradiation.

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Section: Model Simulationsmentioning

confidence: 99%

Temperature and velocity dependent friction of a microscale graphite-DLC heterostructure

Gongyang

Ouyang

et al. 2019

Friction

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“…Non-monotonic friction-coverage dependence has recently been observed in NEMD simulations of a single asperity sliding on a crystalline surface lubricated by an atomic fluid. 83 In these systems, the tip and substrate were incommensurate, meaning that the presence of atoms between the tip and substrate increased friction until the coverage approached the level required to form a complete monolayer. 83 Non-monotonic friction-coverage behaviour has also been observed in microscale SFA experiments Yoshizawa et al 84 using zwitterionic surfactants with a range of headgroup and tailgroup structures on mica surfaces in aqueous environments.…”

Section: Frictionmentioning

confidence: 99%

“…83 In these systems, the tip and substrate were incommensurate, meaning that the presence of atoms between the tip and substrate increased friction until the coverage approached the level required to form a complete monolayer. 83 Non-monotonic friction-coverage behaviour has also been observed in microscale SFA experiments Yoshizawa et al 84 using zwitterionic surfactants with a range of headgroup and tailgroup structures on mica surfaces in aqueous environments. The non-monotonic response was attributed to a transition from liquid-like, to amorphous, and to solid-like monolayers with increasing coverage (Γ = 2-5 nm −2 ).…”

Section: Frictionmentioning

confidence: 99%

Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

Gao¹,

Ewen

Hartkamp³

et al. 2020

Preprint

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<div>Surfactant molecules, known as organic friction modi?ers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through</div><div>a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show</div><div>that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately</div><div>originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

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“…Thus, adsorbed molecules on substrates play a crucial role in adhesion, friction and wear behaviors [10–22] . Interestingly, molecular dynamics(MD) simulation demonstrated that for given external conditions, such as normal load, temperature and adsorbate surface coverage, the observed regime of friction is determined by the strength of the adsorbate‐substrate interaction [23–25] …”

Section: Introductionmentioning

confidence: 99%

In situ friction study of Ag Underpotential deposition (UPD) on Au(111) in aqueous electrolyte

Park

Baltruschat

2021

ChemPhysChem

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The electrodeposition of silver on Au(111) was investigated using lateral force microscopy (LFM) in Ag+ containing sulfuric acid. Friction force images show that adsorbed sulfate forms ()3×7R19.1∘ structure (θsulfate=0.2) on Au(111) prior to Ag underpotential deposition (UPD) and (3×3R30∘) structure (θsulfate=0.33 ) on a complete monolayer or bilayer of Ag. Variation of friction with normal load shows a non‐monotonous dependence, which is caused by increasing penetration of the tip into the sulfate adlayer. In addition, the friction force is influenced by the varying coverage and mobility of Ag atoms on the surface. Before Ag coverage reaches the critical value, the deposited silver atoms may be mobile enough to be dragged by the movement of AFM tip. Possible penetration of the tip into the UPD layer at very high loads is discussed as a model for self‐healing wear. However, when the coverage of Ag is close to 1, the deposited Ag atoms are tight enough to resist the influence of the AFM tip and the tip penetrates only into the sulfate adlayer.

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Atomic-scale sliding friction on a contaminated surface

Cited by 29 publications

References 45 publications

Temperature and velocity dependent friction of a microscale graphite-DLC heterostructure

Temperature and velocity dependent friction of a microscale graphite-DLC heterostructure

Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

In situ friction study of Ag Underpotential deposition (UPD) on Au(111) in aqueous electrolyte

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