Origin of High Friction at Graphene Step Edges on Graphite

Chen, Zhe; Khajeh, Arash; Martini, Ashlie; Kim, Seong H.

doi:10.1021/acsami.0c18098

Cited by 23 publications

(10 citation statements)

References 49 publications

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“…The experimentally measured friction force (𝐹𝐹 𝑒𝑒 ) will be the sum of all possible physical and chemical contributions. [75][76][77] Chemical contributions to friction might include hydrogen bonding interactions or transient chemical bond formation / dissociation, [75][76][77] while examples of physical contributions are stick-slip type processes, [78] plastic deformation, [79] or fluid shear. [80,81] When the experimentally measured friction is used in Eq.…”

Section: Perspectivesmentioning

confidence: 99%

Activation Volume in Shear-Driven Chemical Reactions

Martini

Kim

2021

Tribol Lett

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Interfacial shear-driven or shear-assisted chemical reactions play an important role in many engineering processes, including reactions between lubricant additives and the surfaces of mechanical components and fabrication of surface topographic features. Mechanistic studies of shear-driven chemical reactions often employ a mechanically assisted thermal-activation model from which a so-called activation volume can be defined. Activation volume is important because it quantifies the efficiency of interfacial shear to drive the reaction. Recent advancements in methods have enabled calculation of activation volume from both nano-and macro-scale experiments as well as simulations. However, the calculated volumes differ by orders of magnitude, even for the same reactant species, and the physical interpretations vary correspondingly. Here, we review how activation volume has been measured and interpreted for shear-driven reactions in the literature with the goal of guiding future efforts to understand and use this important parameter for engineering design through tribochemistry.

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Section: Perspectivesmentioning

confidence: 99%

Activation Volume in Shear-Driven Chemical Reactions

Martini

Kim

2021

Tribol Lett

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“…The experiments were performed at least 300 nm away from the edge of the graphitic flake. [45,46] The nominal AFM probe radius and the cantilever dimensions were measured after the completion of measurements using a scanning electron microscope (JEOL JSM-6500F, USA) (Figure S1, Supporting Information). The normal and lateral forces were calibrated using the thermal method [47] and Sader's method, [48] respectively.…”

Section: Methodsmentioning

confidence: 99%

Load‐Dependent Friction Hysteresis for Graphitic Surfaces in n‐Hexadecane

Baboukani

Pitkar

et al. 2022

Adv Materials Inter

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behavior that is dependent on the sliding history of the contact, which currently remains unexplored and is the focus of the current study.Generating a comprehensive understanding of the dissipation pathways for 2D materials in liquids is crucial for developing predictive models for the friction and wear behavior of 2D materials. [11] The atomic force microscope (AFM) has proven to be a unique and powerful tool to investigate the atomic origins of friction behavior of 2D materials under a well-defined, single-asperity contact and in the absence of wear. Previous experiments using AFM in a dry environment showed that the probe sliding history on the 2D material leads to several unique behaviors such as frictional aging of the contact, [12,13] friction strengthening, [14][15][16][17] and load-dependent friction hysteresis. [18][19][20] The previous load-dependent friction measurements on supported graphene reported lower friction forces while increasing the normal load (loading) than when the load was withdrawn (unloading) at a given normal load, [18,19] displaying friction hysteresis. This behavior is shown to originate from the irreversible transformation of the contact upon loading, caused either by changes in the contact area and/or interaction forces at the sliding interface. [18] Several physical parameters, such as the presence of environmental adsorbates, [21] maximum applied load, [19] temperature, [22] sliding velocity, [23] etc., have been shown to influence the sliding-history-dependent friction behavior for single and as well for few-layer (FL) graphene.In ambient or dry conditions, sliding an AFM probe across the graphene deposited on a copper substrate led to an out-of-theplane deformation of the graphene adjacent to the AFM probe. A higher adhesion during the unloading process, in comparison to loading, resulted in delayed relaxation of the graphene layer (higher contact area) and hence enhanced friction hysteresis. [19] However, the presence of condensed water at the probe-graphene contact suppressed the out-of-plane deformation of graphene but instead led to an irreversible reorganization of water molecules at the contact once loaded. [18] The contact area hysteresis, i.e., the smaller number of water molecules in contact with the probe (contact area) during the loading process, in comparison to unloading, led to friction hysteresis of graphene in a humid environment. [18] The load-dependent friction hysteresis was also observed for bulk graphitic surfaces when the work of adhesion between the AFM probe and the graphitic surface exceeded the Sliding-induced friction behavior of a single-asperity silica probe against fewlayer (FL) graphene and bulk graphite is measured in the presence of n-hexadecane using an atomic force microscope (AFM). The load-dependent nanoscale friction measurements display friction hysteresis, i.e., higher friction forces during unloading of the contact than loading, at a given normal load. However, unlike hysteresis in friction of graphene measured in ambient, several uniq...

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“…287 Similarly, a considerable amount of work has been carried out by Martini and collaborators using reactive FFs to study interactions between solid and liquid lubricants, nanoscale contact and sliding, etc. [288][289][290][291] Comprehensive details regarding the use of RMD simulations in tribological applications can also be further accessed in a detailed review article by Martini et al 26…”

Section: Reactive Molecular Dynamics (Rmd)mentioning

confidence: 99%