材料科学
微晶
晶界
方向错误
粒度
复合材料
晶界强化
化学气相沉积
打滑(空气动力学)
单层
极限抗拉强度
凝聚态物理
结晶学
纳米技术
冶金
微观结构
化学
物理
热力学
作者
Thijs J. H. Vlugt,Pinqiang Cao,Zhiliang Zhang,Fulong Ning,Zheng Songsheng,Zhiliang Zhang
出处
期刊:Nano Letters
[American Chemical Society]
日期:2018-02-05
卷期号:18 (2): 1543-1552
被引量:65
标识
DOI:10.1021/acs.nanolett.7b05433
摘要
Pristine monocrystalline molybdenum disulfide (MoS2) possesses high mechanical strength comparable to that of stainless steel. Large-area chemical-vapor-deposited monolayer MoS2 tends to be polycrystalline with intrinsic grain boundaries (GBs). Topological defects and grain size skillfully alter its physical properties in a variety of materials; however, the polycrystallinity and its role played in the mechanical performance of the emerging single-layer MoS2 remain largely unknown. Here, using large-scale atomistic simulations, GB structures and mechanical characteristics of realistic single-layered polycrystalline MoS2 of varying grain size prepared by confinement-quenched method are investigated. Depending on misorientation angle, structural energetics of polar-GBs in polycrystals favor diverse dislocation cores, consistent with experimental observations. Polycrystals exhibit grain-size-dependent thermally induced global out-of-plane deformation, although defective GBs in MoS2 show planar structures that are in contrast to the graphene. Tensile tests show that presence of cohesive GBs pronouncedly deteriorates the in-plane mechanical properties of MoS2. Both stiffness and strength follow an inverse pseudo Hall-Petch relation to grain size, which is shown to be governed by the weakest link mechanism. Under uniaxial tension, transgranular crack propagates with small deflection, whereas upon biaxial stretching, the crack grows in a kinked manner with large deflection. These findings shed new light in GB-based engineering and control of mechanical properties of MoS2 crystals toward real-world applications in flexible electronics and nanoelectromechanical systems.
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