Elastic Properties of Mimetically Synthesized Model Nanoporous Carbon
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Elastic Properties of Mimetically Synthesized Model Nanoporous Carbon Xi Mi1 and Yunfeng Shi2 1 Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute 2 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA. ABSTRACT Activated carbon is widely used for its attractive diffusion, adsorption and reaction properties. However, its mechanical behavior has received much less attention. We present a molecular dynamics simulation study on the elastic properties of activated carbon with nanometer-sized pores. The nanoporous carbon sample is composed of curved and defected graphene sheets, which is synthesized using quench molecular dynamics (QMD) method [1]. One unique feature of the current model is the mechanical stability, thus the bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio can be obtained from simulated mechanical tests. By varying the density of the nanoporous carbon model, it was further found that the bulk modulus vs. density relation follows Gibson-Ashby type power law with exponents of 2.80 at low densities and 1.65 at high densities. INTRODUCTION Nanoporous carbon materials have drawn substantial research interests because of their unique properties: extremely large surface area, preferential adsorption and the potential to be used as catalysts for chemical reactions [2]. A prerequisite for applications that fully exploit the above properties of these materials is the knowledge of their mechanical properties. Although indentation tests have been conducted on various nanoporous carbon materials [3-6], the systematic experimental or theoretical studies on mechanical properties remain absent. On the other hand, mechanical properties of cellular materials have been established in materials with macroscopic pores [16], while the typical size in nanoporous carbon is between a few and a few tenths of nanometers. Whether the structure-property relation in foams is valid for systems with nanometer-sized pores has not been fully examined. Nanoporous carbon can be seen as a model system to provide insights on the structure-property relation for nanoporous materials in general. Empowered by the rapid growth of computation power, molecular simulation techniques have provided valuable atomic information on the porous structure of nanoporous carbon, adsorption and diffusion behavior of its guest species [2, 7-10]. However, there is very few viable atomic level nanoporous carbon model that are both structurally realistic (i.e. agrees with experimental structural signatures) and mechanically stable (thus can be subjected to mechanical tests). The widely used slit pore models [11] fail to match the structural signatures. Recent hybrid reverse Monte Carlo (HRMC) method [12, 8] is able to generate atomic models with structural signatures that match the experiments. However, the structural signature deviates rapidly from the correct values upon thermal relaxation which indicates that the atomic models from HRMC are
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