The normal-auxeticity mechanical phase transition in graphene

Deng, Binghui; Hou, Jie; Zhu, Hanxing; Liu, Sheng; Liu, Emily; Shi, Yunfeng; Peng, Qing

doi:10.1088/2053-1583/aa61e5

Cited by 49 publications

(46 citation statements)

References 33 publications

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“…The Young's modulus of ingredient B has no effect on the results of k n and α n , but strongly affects the stiffness of the cellular materials. The normal‐auxeticity mechanical phase transition has recently been found in graphene, an atomic‐thick 2D hexagonal carbon . The results in this paper could apply to multiscale metamaterials design spanning from macro‐ down to micro‐ and nanoscales and our study opens a new avenue to developing more sensitive functional materials or devices.…”

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confidence: 54%

Giant Thermal Expansion in 2D and 3D Cellular Materials

et al. 2018

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When temperature increases, the volume of an object changes. This property was quantified as the coefficient of thermal expansion only a few hundred years ago. Part of the reason is that the change of volume due to the variation of temperature is in general extremely small and imperceptible. Here, abnormal giant linear thermal expansions in different types of two-ingredient microstructured hierarchical and self-similar cellular materials are reported. The cellular materials can be 2D or 3D, and isotropic or anisotropic, with a positive or negative thermal expansion due to the convex or/and concave shape in their representative volume elements respectively. The magnitude of the thermal expansion coefficient can be several times larger than the highest value reported in the literature. This study suggests an innovative approach to develop temperature-sensitive functional materials and devices.

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confidence: 54%

Giant Thermal Expansion in 2D and 3D Cellular Materials

et al. 2018

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“…To adopt the AIREBO potential for large deformation, researchers generally modify the cutoff distances according to the specific systems studied [18,19,20]. We have examined this r min cc parameter and adopted the value of 1.92Å, as reported in our previous work [14]. The stress-strain curves are extremely insensitive to the cutoff distances under the strain below 0.1.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…Considering that the graphene, a honeycomb like structure, has a rotational symmetry in the plane and there is only 30 • apart between the armchair direction and the closest zigzag direction, we hypothesize that the anisotropy of the NA transition might imply a possible critical stretching direction between the armchair and the zigzag direction with respect to this NA transition phenomenon. To explore this issue, we have carried out extensive studies by taking advantage of our previous work [14], and shown that the NA transition disappears at a magic angle θ (shown in Figure 1) of around 10.9 • and this magic angle is weakly dependent on the temperature.…”

Section: Introductionmentioning

confidence: 99%

Magic auxeticity angle of graphene

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Zhu

et al. 2019

Carbon

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Solids exhibit transverse shrinkage when they are stretched, except auxetics that abnormally demonstrate lateral expansion instead. Graphene possesses the unique normal-auxeticity (NA) transition when it is stretched along the armchair direction but not along the zigzag direction. Here we report on the anisotropic temperature-dependent NA transitions in strained graphene using molecular dynamics simulations. The critical strain where the NA transition occurs increases with respect to an increase in the tilt angle deviating from armchair direction upon uniaxial loading. The magic angle for the NA transition is 10.9 • , beyond which the critical strain is close to fracture strain. In addition, the critical strain decreases with an increasing temperature when the tilt angle is smaller than the NA magic angle. Our results shed lights on the unprecedented nonlinear dimensional response of graphene to the large mechanical loading at various temperatures.

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“…The Brenner second-generation reactive empirical bond-order potential [24,25] was used to model the C-C bounded interaction, while the Fe-Fe and Fe-C interactions were modeled with the embedded atom potential [26]. The embedded atom potential is described by two terms [27]:…”

Section: Model Setup and Interatomic Potentialmentioning

confidence: 99%

Interaction of Edge Dislocations with Graphene Nanosheets in Graphene/Fe Composites

et al. 2018

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Abstract:Graphene is an ideal reinforcement material for metal-matrix composites owing to its exceptional mechanical properties. However, as a 2D layered material, graphene shows highly anisotropic behavior, which greatly affects the mechanical properties of graphene-based composites. In this study, the interaction between an edge dislocation (b = 1/2 (111)) and a pair of graphene nanosheets (GNSs) in GNS reinforced iron matrix composite (GNS/Fe) was investigated using molecular dynamic simulations under simple shearing conditions. We studied the cases wherein the GNS pair was parallel to the (110), (112), and (111) planes, respectively. The results showed that the GNS reinforcement can effectively hinder dislocation motion, which improves the yield strength. The interaction between the edge dislocation and the GNS pair parallel to the (112) plane showed the strongest effect of blocking dislocations among the three cases, resulting in increases in the shear modulus and yield stress of 107% and 1400%, respectively. This remarkable enhancement was attributed to the Orowan "by-passing" strengthening mechanism, whereas cross-slip of dislocation segments was observed during looping around GNSs. Our results might contribute to the development of high-strength iron matrix composites.

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The normal-auxeticity mechanical phase transition in graphene

Cited by 49 publications

References 33 publications

Giant Thermal Expansion in 2D and 3D Cellular Materials

Giant Thermal Expansion in 2D and 3D Cellular Materials

Magic auxeticity angle of graphene

Interaction of Edge Dislocations with Graphene Nanosheets in Graphene/Fe Composites

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