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(a) Simulation model of a triangular graphene flake. (b) Lateral force as a function of sliding distance for the triangle flake on different surfaces. The black dashed line is a guideline to highlight the rise of the lateral force on the boundary surface.
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The nanofriction of graphene is critical for its broad applications as lubrications and flexible electronics. Herein, using Au substrate as an example, we have investigated the effect of grain boundary on nanofriction of graphene by means of molecular dynamics simulations. We have systematically examined the coupling effects of grain boundary with...
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Continuum scaling laws often break down when materials approach atomic length scales, reflecting changes in their underlying physics and the opportunities to access unconventional properties. These continuum limits are evident in two-dimensional materials, where there is no consensus on their bending stiffnesses or how they scale with thickness. Th...
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... In addition to edges, there are abundant other structural factors that affect structural morphologies of graphene and other 2D materials. Typical example is topological defects such as Stone-Wales transformations, line defects, vacancies, etc, and these types of defects have been found to substantially affect frictional responses of 2D layered materials [18][19][20][21]. For example, Cao et al studied the effect of Stone-Wales defect on friction of graphene and found that pinning effect between tip and heptagons plays a key role in modifying the wrinkle structure and frictional force [22]. ...
Graphite possessing extraordinary frictional properties has been widely used as solid lubricants. Interesting frictional characteristics have been observed for pristine graphene layers, for defective graphene, the frictional signal shows richer behaviors such as those found in topological defective graphene and graphene step edges. Recently discovered nanoporous graphene represents a new category of defect in graphene and its impact on graphene frictional properties has not yet been explored. In this work, we perform molecular dynamics simulations on the frictional responses of nanoporous graphene layers when slid using a silicon tip. We show that the buried nanopore raises maximum friction signal amplitude while preserving the stick-slip character, the size of the nanopore plays a key role in determining the maximum frictional force. Negative friction is observed when the silicon tip scanned towards the center of the nanopore, this phenomenon originates from the asymmetrical variation of the in-plane strain and the out-of-plane deformation when indented by the silicon tip. Moreover, the layer dependent frictional character is examined for the buried graphene nanopores, showing that increasing graphene layers weakens the effect of nanopore on the frictional signal.
... Using molecular dynamics simulations, He et al. [26] investigated the effect of the grain boundary on the nanofriction of graphene on a Au substrate. They found that grain boundaries could reduce the friction between graphene and the gold substrate with a small deformation of the latter. ...
Graphene might be one of the most important materials in human history [1-4]. As a monatomic layer of carbon atoms in a honeycomb lattice, graphene possesses extraordinary mechanical properties, in addition to other amazing properties. The mechanical properties are of extreme importance for several potential applications, including tailoring other properties with strain engineering [5]. It is worth noting that the first fabrication of graphene is through mechanical exfoliation. As a fact, Mechanical exfoliation is still a popular approach for the scalable production of graphene [6].
To date, chemical vapor deposition has been employed to grow large-area polycrystalline (PC) films of hexagonal boron nitride (hBN). However, PC hBN thin films exhibit abundant grain boundaries, small grain sizes, and structural imperfections, which collectively degrade the performance as well as hinder the scalability and potential applications of hBN films. Recently, demonstrated deposition methods for growing large-area single-crystalline (SC) hBN films can break through these bottlenecks and have opened avenues for new opportunities. Large-area SC hBN films outperform their PC counterparts owing to the presence of fewer grain boundaries and a more homogeneous surface morphology. This review article presents a consolidated overview of the growth mechanisms of SC hBN films and role of metal catalysts (substrates) in the growth process. Applications, in which SC hBN outperforms PC hBN as well as the potential applications of SC hBN, are also discussed.
