Mechanical Properties of Nanocarbon Hybrid Films via Indentation Simulation
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Mechanical Properties of Nanocarbon Hybrid Films via Indentation Simulation T. Onodera2 and K. Shintani1 1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan 2 Division of Science Education, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501, Japan ABSTRACT The mechanical properties of nanocarbon hybrid films are addressed by means of indentation simulation based on molecular-dynamics. In these films, single-walled carbon nanotubes (SWCNTs) are intercalated parallel to each other between graphene sheets; the SWCNT axes are also parallel to the planes of the sheets. Thus the simulation model is quasi-two-dimensional. The load-deflection curve depends on both the number of the layers and the diameter of SWCNTs. In the range of small forces, the simulation data can be interpolated by a cubic function of the deflection, while in the range of large forces, the data can be expressed in terms of a linear function of the deflection. It is revealed that such a transition corresponds to the structural change of the hybrid film. INTRODUCTION Graphene and carbon nanotubes (CNTs) possess the excellent mechanical properties, e. g., high elasticity, high toughness, and high flexibility. Understanding these superior mechanical properties tempts researchers to fabricate nanocarbon hybrids consisting of them. Lv et al. [1] reviewed graphene-CNT hybrids such as three-dimensional CNT networks, a hybrid of graphene with vertical CNTs, a hybrid of graphene with horizontal CNTs, rebar graphene, schwarzites, a graphene-multi-walled carbon nanotubes (MWCNTs) hybrid film. These hybrids except the last are constructed by the covalent interconnections between sp2-hybridized carbon nanostructures. On the other hand, in a graphene-MWCNTs hybrid film, the interaction force joining graphene sheets with MWCNTs is the van der Waals interaction or π-π interaction. Such a way of connection leads to the high flexibility of the hybrid films. Tristán-López et al. [2] prepared large-area hybrid films in the form of alternating layers of graphene and MWCNTs. They assumed the MWCNTs are intercalated parallel to the graphene sheets. Their films show high mechanical robustness and excellent field emission properties. However, their films are not transparent because the CNTs constituting the alternating layers are MWCNTs. One of the ideas to secure the transparency of hybrid films is to intercalate SWCNTs between graphene sheets while maintaining the mechanical robustness. In this paper, the mechanical properties of hybrid films consisting of the alternating layers of graphene and SWNTs are addressed via molecular-dynamics. According to Tristán-López et al., SWCNTs are assumed to be intercalated parallel to each other between graphene sheets with the SWCNT axes parallel to the planes of the sheets. The periodic boundary condition is applied in the direction of the axes of the SWNTs. The indentation forces are imposed on the carbon atoms on one o
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