Adhesion-dependent negative friction coefficient on chemically modified graphite at the nanoscale

Deng, Zhao; Smolyanitsky, Alexander Y.; Li, Qunyang; Feng, Xi‐Qiao; Cannara, Rachel J.

doi:10.1038/nmat3452

Cited by 269 publications

(251 citation statements)

References 22 publications

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“…The figure shows that for most of the diagram, that is, in the L, SK-SL and CL regions, there is a monotonic increase in frictional force with pressure. This trend is consistent with Amontons' first law for macroscopic bodies which states that the frictional force is proportional to 68 who demonstrated that an increase in normal force can lead to a decrease in the frictional force. It is reasonable to conclude that this is a consequence of structural changes in the film caused by that change in load which affect the slipperiness of the boundary.…”

Section: Hysteresis In the Systemsupporting

confidence: 91%

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

Maćkowiak

Heyes

Dini

et al. 2016

The Journal of Chemical Physics

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The phase behavior of a confined liquid at high pressure and shear rate, such as is found in elastohydrodynamic lubrication, can influence the traction characteristics in machine operation.Generic aspects of this behavior are investigated here using Non-equilibrium Molecular Dynamics (NEMD) simulations of confined Lennard-Jones (LJ) films under load with a recently proposed wall-driven shearing method without wall atom tethering [Gattinoni, Maćkowiak, Heyes, Brańka and Dini, Phys. Rev. E 90, 043302 (2014)]. The focus is on thick films in which the nonequilibrium phases formed in the confined region impact on the traction properties. The nonequilibrium phase and tribological diagrams are mapped out in detail as a function of load, wall sliding speed and atomic scale surface roughness, which is shown can have a significant effect. The transition between these phases is typically not sharp as the external conditions are varied. The magnitude of the friction coefficient depends strongly on the nonequilibrium phase adopted by the confined region of molecules, and in general does not follow the classical friction relations between macroscopic bodies, e.g., the frictional force can decrease with increasing load in the Plug-Slip (PS) region of the phase diagram owing to structural changes induced in the confined film. The friction coefficient can be extremely low (∼ 0.01) in the PS region as a result of incommensurate alignment between a (100) face-centered cubic wall plane and reconstructed (111) layers of the confined region near the wall. It is possible to exploit hysteresis to retain low friction PS states well into the Central Localization high wall speed region of the phase diagram.Stick-Slip behavior due to periodic in-plane melting of layers in the confined region and subsequent annealing is observed at low wall speeds and moderate external loads. At intermediate wall speeds and pressure values (at least) the friction coefficient decreases with increasing well depth of the LJ potential between the wall atoms, but increases when the attractive part of the potential between wall atoms and confined molecules is made larger.2

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Section: Hysteresis In the Systemsupporting

confidence: 91%

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

Maćkowiak

Heyes

Dini

et al. 2016

The Journal of Chemical Physics

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“…[1][2][3] For mechanical applications, the interfacial shear strength is a crucial factor that determines the effectiveness of load transfer between the polymer matrix and nanoreinforcements. [4] In principle, the interfacial shear strength is determined by the interfacial bonds between the reinforcements and the polymer matrix.…”

Section: Introductionmentioning

confidence: 99%

Diamond Nanothread as a New Reinforcement for Nanocomposites

Zhan

Zhang

Tan

et al. 2016

Adv Funct Materials

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Abstracts: This work explores the application of a new one-dimensional carbon nanomaterial, the diamond nanothread (DNT), as a reinforcement for nanocomposites.Owing to the existence of Stone-Wales transformation defects, the DNT intrinsically possesses irregular surfaces, which is expected to enhance the non-covalent interfacial load transfer. Through a series of in silico pull-out studies of the DNT in polyethylene (PE) matrix, we found that the load transfer between DNT and PE matrix is dominated by the non-covalent interactions, in particular the van der Waals interactions. Although the hydrogenated surface of the DNT reduces the strength of the van der Waals interactions at the interface, the irregular surface of the DNT can compensate for the weak bonds. These factors lead to an interfacial shear strength of the DNT/PE interface comparable with that of the carbon nanotube (CNT)/PE interface. Our results show that the DNT/PE interfacial shear strength remains high even as the number of Stone-Wales transformation defects decreases. It can be enhanced further by increasing the PE density or introduction of functional groups to the DNT, both of which greatly increase the non-covalent interactions.

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“…[12][13][14] The adhesion between atomic force microscope (AFM) probe and graphene can also affect the friction force and lead to the emergence of an effectively negative friction coefficient. 15 Meanwhile, electro-phonon coupling and shear deformations were also brought to explain the energy dissipation mechanism during the friction process. [16][17][18][19] A recent study revealed that the friction force of chemically modified graphene is mainly governed by the out of plane bending stiffness.…”

Section: Introductionmentioning

confidence: 99%

An atomistic investigation of the effect of strain on frictional properties of suspended graphene

Bai

et al. 2016

AIP Advances

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We performed molecular dynamics (MD) simulations of a diamond probe scanned on a suspended graphene to reveal the effect of strain on the frictional properties of suspended graphene. The graphene was subjected to some certain strain along the scanning direction. We compared the friction coefficient obtained from different normal loads and strain. The results show that the friction coefficient can be decreased about one order of magnitude with the increase of the strain. And that can be a result of the decreased asymmetry of the contact region which is caused by strain. The synthetic effect of potential energy and the fluctuation of contact region were found to be the main reason accounting for the fluctuation of the friction force. The strain can reduce the fluctuation of the contact region and improve the stability of friction.

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Adhesion-dependent negative friction coefficient on chemically modified graphite at the nanoscale

Cited by 269 publications

References 22 publications

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

Diamond Nanothread as a New Reinforcement for Nanocomposites

An atomistic investigation of the effect of strain on frictional properties of suspended graphene

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