A DCAMM seminar will be presented by
\nProfessor Jeffrey W. Kysar
\nDepartment of Mechanical Engineering
\nColumbia University, New York, USA
\n\n
\n
Abstract:
\n
\nTwo-dimensional materials are planar molecules of arbitrary extent that consist of one or possibly a few atomic layers. Graphene, the archetypal two-dimensional material, consists of a single close-packed array of carbon atoms. Another, molybdenum disulfide, consists of three atomic layers: a close-packed array of molybdenum atoms sandwiched between two close-packed arrays of sulfur atoms. Two-dimensional materials have many potential applications due to their unique electronic, optical and mechanical properties. The focus of this talk is on the mechanical properties of graphene and molybdenum disulfide. We will discuss methods to isolate two-dimensional materials via mechanical exfoliation and subsequently to make single crystal specimens via nanofabrication methods. An atomic force microscope or a nanoindenter is used to indent a freestanding circular film. The experimental results suggest the mechanically exfoliated single crystal materials to be free of defects. Thus, the breaking strengths of graphene and molybdenum disulfide represent their respective intrinsic strengths, or the maximum stress that a material theoretically can support. In fact the mechanical strength exhibited by graphene is in excess of 100 GPa, making it the strongest material ever characterized. We will also discuss a multiscale model of the stress-strain constitutive parameters of graphene and molybdenum disulfide based upon ab initio Density Functional Theory (DFT) calculations. The theory is implemented into the finite element method to validate the multiscale model against experiments. Finally, we will discuss graphene grown by Chemical Vapor Deposition (CVD) using industrially scalable processes. The CVD grown graphene is polycrystalline, yet upon optimization of the CVD parameters, the strength of the polycrystalline graphene can achieve a very high fraction of the intrinsic strength of defect-free single crystal graphene.
Danish pastry, coffee and tea will be served 15 minutes before the seminar starts.
\n
\nAll interested persons are invited
A DCAMM seminar will be presented by
\nProfessor Jeffrey W. Kysar
\nDepartment of Mechanical Engineering
\nColumbia University, New York, USA
\n\n
\n
Abstract:
\n
\nTwo-dimensional materials are planar molecules of arbitrary extent that consist of one or possibly a few atomic layers. Graphene, the archetypal two-dimensional material, consists of a single close-packed array of carbon atoms. Another, molybdenum disulfide, consists of three atomic layers: a close-packed array of molybdenum atoms sandwiched between two close-packed arrays of sulfur atoms. Two-dimensional materials have many potential applications due to their unique electronic, optical and mechanical properties. The focus of this talk is on the mechanical properties of graphene and molybdenum disulfide. We will discuss methods to isolate two-dimensional materials via mechanical exfoliation and subsequently to make single crystal specimens via nanofabrication methods. An atomic force microscope or a nanoindenter is used to indent a freestanding circular film. The experimental results suggest the mechanically exfoliated single crystal materials to be free of defects. Thus, the breaking strengths of graphene and molybdenum disulfide represent their respective intrinsic strengths, or the maximum stress that a material theoretically can support. In fact the mechanical strength exhibited by graphene is in excess of 100 GPa, making it the strongest material ever characterized. We will also discuss a multiscale model of the stress-strain constitutive parameters of graphene and molybdenum disulfide based upon ab initio Density Functional Theory (DFT) calculations. The theory is implemented into the finite element method to validate the multiscale model against experiments. Finally, we will discuss graphene grown by Chemical Vapor Deposition (CVD) using industrially scalable processes. The CVD grown graphene is polycrystalline, yet upon optimization of the CVD parameters, the strength of the polycrystalline graphene can achieve a very high fraction of the intrinsic strength of defect-free single crystal graphene.
Danish pastry, coffee and tea will be served 15 minutes before the seminar starts.
\n
\nAll interested persons are invited