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Mechanism of ultra-low friction of multilayer graphene studied by all atom molecular dynamics

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A molecular dynamics simulation is used to investigate the occurrence of thermal escape motion of a graphene transfer layer in all atom levels. In the simulation, the substrate is modelled as a 3-layer graphene slab, and the transfer layer as layered circle graphene sheets. The top graphene sheet is force to move in a constant velocity. After the sliding motion, the dynamics of the transfer layers showed different dependences on the sliding velocity and the size of the graphene sheet. Only when the sliding motion is low enough and the size is large enough, is the thermal escape motion found. When the sliding speed is too high, the lower layers cannot follow the top sheet. When the graphene sheet is too small, the lower layered structure is broken due to an internal motion. The latter motion is not found during the study using the previous coarse-grained simulation. The size of the layers experimentally observed is the same as this simulation, and when the sliding motion is low enough, a low friction is observed. Thus, a low friction is indicated as a result of the thermal escape motion.
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... Molecular dynamics simulations have been extensively utilized in the investigation of friction in carbon-based materials. Previous research has elucidated that a low friction mechanism is attributed to graphite's thermal escape motion [20,21], and that a super-lubrication phenomenon occurs due to single-layer graphene and iron particles [22,23]. In contrast, verification of GO using molecular dynamics simulations has been reported, including the mechanical properties of GO [24,25] and the wear characteristics of single-layer GO and DLC [26]. ...
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... In addition, another mechanism exists to generate low friction. According to the mechanism of thermal escape motion (Washizu et al., 2012;Maeda and Washizu, 2018), graphene in the stacking state of the commensurate level can also produce ultralow friction. While chasing the performance of graphene, a large number of 2D materials have been prepared, such as transition metal dichalcogenides (TMDCs), black phosphorus, and h-BN. ...
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... In addition to solid lubrication by two dimensional materials or graphene combined with iron nanoparticles [3][4][5][6][7][8][9][10], lubrication by the metallic oxide particles dispersed in the oils has been found to be significantly influencing the friction reduction of the different materials by the mechanisms as mending, tribofilm, sliding, rolling and applied load carrying capability [11][12][13][14][15][16][17][18][19][20][21][22]. One can see the long lists of the metallic oxide nanoparticle additives combined with the friction improvement and the lubrication mechanisms in the previously reviewing reports [23][24][25]. ...
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... Among the variety of materials used as friction reduction coatings, 2 Dgraphene layer has been investigated for the past few years by many authors in the scientific literature. Very interesting lubricant properties are attributed to graphene [6][7][8] and Geim and Novoselov at al. [9] and Wang et al [10] reported excellent mechanical, thermal and electrical properties for graphene. ...
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