Liu Feng, Wang Chao, Tang Qiheng
State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, China.
School of Engineering Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
Small. 2018 Aug;14(32):e1801458. doi: 10.1002/smll.201801458. Epub 2018 Jul 17.
In conventional foams, electrical properties often play a secondary role. However, this scenario becomes different for 3D graphene foams (GrFs). In fact, one of the motivations for synthesizing 3D GrFs is to inherit the remarkable electrical properties of individual graphene sheets. Despite immense experimental efforts to study and improve the electrical properties of 3D GrFs, lack of theoretical studies and understanding limits further progress. The causes to this embarrassing situation are identified as the multiple freedoms introduced by graphene sheets and multiscale nature of this problem. In this article, combined with transport modeling and coarse-grained molecular dynamic (MD) simulations, a theoretical framework is established to systematically study the electrical conducting properties of 3D GrFs with or without deformation. In particular, through large-scale and massive calculations, a general relation between contact area and conductance for two van der Waals bonded graphene sheets is demonstrated, in terms of which the conductivity maximum phenomenon in GrFs is first theoretically proposed and its competition mechanism is explained. Moreover, the theoretical prediction is consistent with previous experimental observations.
在传统泡沫材料中，电学性质通常起次要作用。然而，对于三维石墨烯泡沫（GrFs）而言，情况则有所不同。事实上，合成三维GrFs的动机之一是继承单个石墨烯片优异的电学性质。尽管为研究和改善三维GrFs的电学性质付出了巨大的实验努力，但缺乏理论研究和理解限制了进一步的进展。造成这种尴尬局面的原因被认为是石墨烯片引入的多种自由度以及该问题的多尺度性质。在本文中，结合输运建模和粗粒度分子动力学（MD）模拟，建立了一个理论框架，以系统地研究有或无变形情况下三维GrFs的导电性质。特别是，通过大规模的大量计算，证明了两个范德华键合石墨烯片的接触面积与电导率之间的一般关系，据此首次从理论上提出了GrFs中的电导率最大值现象并解释了其竞争机制。此外，理论预测与先前的实验观察结果一致。
