Mechanical Properties of Vacancy-containing Graphene and Graphite Estimated by Molecular Dynamics Simulations
ABSTRACT Using molecular dynamics (MD) simulation, we investigated the mechanical properties of graphene and graphite, which contain cluster-type vacancies. We found that as the vacancy size increases, the tensile strength drastically decreases to at least 56% of that of pristine graphene, whereas Young’s modulus hardly changes. In vacancy-containing graphene, we also found that slip deformation followed by fracture occurs under zigzag tension. In general, tensile strength decreases as the size of cluster-type vacancies increases. However, the tensile strength of graphene with a clustered sextuple vacancy increases as the vacancy disappears because slip deformation proceeds. Furthermore, we found that slip deformation by vacancies in graphite occurs less easily than in graphene.Our results suggest that the shape of vacancies affects the strengths of graphene and graphite.
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ABSTRACT: Abstract Graphene, a single atomic layer of carbon atoms, has continued to draw much attention due to its extraordinary properties and application potential. The electronic and mechanical properties of pristine graphene sheets are outstanding but structural defects deteriorate its mechanical properties. Defects in a graphene structure are unavoidable; they can appear during fabrication processes or environmental and operating conditions in which the graphene based device is used. However, structural defects can be useful in that, they can be used to engineer certain properties of graphene material to achieve new functionalities. Therefore, it is important to understand the relationship between structural defects and graphene’s properties. In this study, the effects of structural defects on the nanomechanical properties of graphene have been investigated using Multimode 8 AFM. Graphene sheets on SiO2 substrate have been irradiated with Gallium ions to introduce controlled amounts of structural defect. Using the PeakForce QNM mode, the relationship between the nanomechanical properties and structural defect density has been found.05/2015, Degree: Master, Supervisor: Klaus Leifer