石墨烯中的力学前沿理论
科学界对石墨烯物性研究取得的历史性突破，使石墨烯受到了广泛的关注。各领域的研究从不同应用背景出发，揭示了石墨烯可能拥有的诸多优异性能，从而使人们对这些物性的应用前景寄予厚望。从力学性能来看，对比完好的石墨烯片层与现有的工程材料的拉伸强度，前者要比后者高出两个数量级以上。同时直觉告诉我们，单层原子结构的膜材料非常容易产生离面变形；并且，石墨烯的大面积制备又通常使其内在缺陷不可避免。理解这些由维度上的极限和新结构带来的独特力学行为及其与三维材料之间的差异，并建立新的描述这类变形行为的分析方法和理论体系，是解决石墨烯材料走向工程应用过程中可靠性和耐久性问题的关键所在。
近期，《国家科学评论》发表了由中科院力学研究所非线性力学国家重点实验室的魏宇杰研究员和美国科罗拉多大学伯德分校机械工程系的杨荣贵教授共同撰写的综述文章“Nanomechanics of graphene” （Natl Sci Rev, 2018, doi: 10.1093/nsr/nwy067. http://dx.doi.org/10.1093/nsr/nwy067）。互补于其他介绍石墨烯各方面性能的综述文章，该文从二维晶体结构的基本力学描述方法入手，综述了目前力学领域关于石墨烯变形、强度、断裂、与基底材料间的相互作用等方面的理论工作，同时讨论了从力学理论层面需要深入研究的几方面问题。
考虑到石墨烯作为最典型二维材料所具备的代表性意义，该文章涵括的力学理论可为其他二维材料的力学研究提供借鉴，甚至可以直接用来描述其他材料的力学行为。
High strength and ultra-low bending rigidity brings in uniqueness of graphene in contrast to other carbon allotropes. The out-of-plane deformation is of soft nature, which gives rise to rich morphology and is crucial for morphology control. Constructing the structure - mechanical property relationship of graphene is of compelling need for the reliability and durability of graphene-based applications. In a new review article published in the Beijing-based National Science Review, scientists at the Institute of Mechanics, Chinese Academy of Sciences, Beijing, China and the University of Colorado, Boulder, USA present the latest theoretical advances in nanomechanics of graphene. Co-authors Yujie Wei and Ronggui Yang summarized the current advances on the mechanics of defects in graphene, and the theory to capture the out-of-plane deformation. They reviewed the structure-mechanical property relationship in graphene, in terms of its elasticity, strength, bending, and wrinkling, with or without the influence of imperfections.
See the article: Yujie Wei, Ronggui Yang, Nanomechanics of graphene, Natl Sci Rev http://dx.doi.org/10.1093/nsr/nwy067.
单层石墨烯的典型可调控形貌及可能的内在缺陷。富勒烯和单壁碳纳米管均可看成石墨烯的变形体。这一过程展示了石墨烯高度的面外变形能力，同时也显示了这一过程中伴随而生的典型缺陷。这些特性和石墨烯的力学性能紧密相关。
Illustration of the ultra-soft deformation in a graphene sheet and such a feature leads to the easy formation of fullerence and carbon nanotubes from graphene sheets. Such a process may involve the formation of defects in graphene which in turn alters the morphology and the deformation behavior of graphene.
