Origin of Friction in Superlubric Graphite Contacts

Qu, Cangyu; Wang, Kunqi; Wang, Jin; Gongyang, Yujie; Carpick, Robert W.; Urbakh, Michael; Zheng, Quanshui

doi:10.1103/physrevlett.125.126102

Cited by 59 publications

(55 citation statements)

References 43 publications

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“…The friction stress is calculated by summing over transverse forces on atoms in the mesa and dividing it by the area of contact. This definition measures the kinetic friction or the mechanical energy dissipation during the sliding process, and is consistent with the experimental measurement [25]. On the other hand, the peak values of the transverse forces measure the interfacial shear resistance.…”

Section: Setups Of MD Simulationssupporting

confidence: 69%

“…However, later experimental studies did not report notable evidences of this issue, and the effects of elastic deformation in the graphite mesa-substrate systems seem negligible for microscale structural superlubricity. The rigidity assumption is thus expected to apply up to the micrometre-and centimetre-scales [2,[24][25][26]. To clarify the vague robustness of structural superlubricity at extended length scales, we performed molecular dynamics (MD) simulations to explore interlayer sliding behaviors between graphene multilayers.…”

Section: Introductionmentioning

confidence: 99%

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Robustness of structural superlubricity beyond rigid models

Feng

2022

Friction

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Structural superlubricity is a theoretical concept stating that the friction force is absent between two rigid, incommensurate crystalline surfaces. However, elasticity of the contact pairs could modify the lattice registry at interfaces by nucleating local slips, favoring commeasure. The validity of structural superlubricity is thus concerned for large-scale systems where the energy cost of elastic distortion to break the lattice registry is low. In this work, we study the size dependence of superlubricity between single-crystal graphite flakes. Molecular dynamics simulations show that with nucleation and propagation of out-of-plane dislocations and strained solitons at Bernal interfaces, the friction force is reduced by one order of magnitude. Elastic distortion is much weaker for non-Bernal or incommensurate ones, remaining notable only at the ends of contact. Lattice self-organization at small twist angles perturbs the state of structural superlubricity through a reconstructed potential energy surface. Theoretical models are developed to illustrate and predict the interfacial elastoplastic behaviors at length scales beyond those in the simulations. These results validate the rigid assumption for graphitic superlubricity systems at microscale, and reveal the intrinsic channels of mechanical energy dissipation. The understandings lay the ground for the design of structural superlubricity applications.

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Section: Setups Of MD Simulationssupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Robustness of structural superlubricity beyond rigid models

Feng

2022

Friction

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“…Aiming to scale-up structural superlubricity in layered material interfaces implies the inevitable appearance of GBs at the sliding interface. As shown above, the scaling of their dissipative contribution with contact area is stronger than the sublinear scaling found for pristine incommensurate layered contacts 33,34 . Nevertheless, the predicted nonmonotonic frictional dependence on normal load and temperature leads to negative differential friction coefficients at the high normal load regime.…”

Section: Discussionmentioning

confidence: 78%

Superlubric Polycrystalline Graphene Interfaces

Gao

Ouyang

Urbakh

et al. 2021

Preprint

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The effect of corrugated grain boundaries on the frictional properties of extended graphitic contacts incorporating a polycrystalline surface are investigated. The friction is found to be dominated by shear induced buckling and unbuckling of corrugated grain boundary dislocations, leading to a nonmonotonic behavior of friction with normal load and temperature. The underlying mechanism involves two competing effects, where an increase of dislocation buckling probability is accompanied by a decrease of the dissipated energy per buckling event. These effects are well captured by a phenomenological two-state model, that allows for characterizing the tribological properties of any large-scale polycrystalline layered interface, while circumventing the need for demanding atomistic simulations. The resulting negative differential friction coefficients obtained in the high-load regime can reduce the expected linear scaling of grain-boundary friction with surface area and restore structural superlubricity at increasing length-scales.

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“…The central hole of the hBN gear is designed to provide an overlap area of two graphene monolayers to form the tBLG area. Because of the superlubricity effect between the interlayers of vdW materials, the friction between the hBN gear and the bottom graphene layer is low enough so that the hBN gear is rotatable through AFM tip pushing 27 . The top-layer graphene, with its main part sitting on the hBN gear, will follow the motion of the hBN gear.…”

Section: Resultsmentioning

confidence: 99%

In-situ twistable bilayer graphene

Huang

et al. 2022

Sci Rep

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The electrical and optical properties of twisted bilayer graphene (tBLG) depend sensitively on the twist angle. To study the angle dependent properties of the tBLG, currently it is required fabrication of a large number of samples with systematically varied twist angles. Here, we demonstrate the construction of in-situ twistable bilayer graphene, in which the twist angle of the two graphene monolayers can be in-situ tuned continuously in a large range with high precision. The controlled tuning of the twist angle is confirmed by a combination of real-space and spectroscopic characterizations, including atomic force microscopy (AFM) identification of crystal lattice orientation, scanning near-field optical microscopy (SNOM) imaging of superlattice domain walls, and resonant Raman spectroscopy of the largely enhanced G-mode. The developed in-situ twistable homostructure devices enable systematic investigation of the twist angle effects in a single device, thus could largely advance the research of twistronics.

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Origin of Friction in Superlubric Graphite Contacts

Cited by 59 publications

References 43 publications

Robustness of structural superlubricity beyond rigid models

Robustness of structural superlubricity beyond rigid models

Superlubric Polycrystalline Graphene Interfaces

In-situ twistable bilayer graphene

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