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Experimental Study on the Graphite/Graphene Nanomechanics and Nanodevice

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Tutor: ZhengQuanShui
School: Tsinghua University
Course: Mechanics
Keywords: micro-nano devices,graphite nano-osocillator,kink mechanics,superlubricity,frict
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Type: PhD thesis
Year:  2011
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Abstract:
Micro-nano devices, is one of the most important research subject in nanotechnology and science of21st century. More and more micro-nano devices from basic research to move towards the application, walked into our daily life. And their development is toward the direction of miniaturization and muti-functionalization. In this thesis, we focused on van der Waals nano oscillator and nanomechanics based on graphite and graphene. The major results and achievements can be divided into four aspects, including three findings, three models and a practical application.Several mechanical phenomena in SiO2thin film and graphite flakes. Micromechanical exfoliation is a major method to obtain good quality graphene recently. We firstly observed an extraordinary kink mode in graphite nanosheets by this method. An interlayer shear lock-in model is further proposed to explain the observed kink mode in the framework of continuum mechanics. Finally, we compared the kink mode in graphite nanosheets with the rippling mode in multi-walled carbon nanotube. In addition, in SiO2thin film/graphite substrate system, we firstly observed an ring-shaped mechanical instability mode and an evolvement behaviour of telephone cord buckling.Development of a superlubricity research platform based on the self-retraction motion of graphite flakes. Reveals the superlubricity nature of the self-retraction motion of graphite flakes. Firstly extends the research on superlubricity from nanoscale to microscale. The self-retraction motion of graphite flakes is so robustness, that can take place stably and reproducibly in vacuum, atmospheric and even liquid environments, which provides a feasible way to realize superlubricity in microelectromechanical system and further for the study of friction and wear. Finally, we proposed a "Stone Wall" structure model for the highly oriented pyrolytic graphite, which can successfully explain the observed scale effects of the self-retraction motion of graphite flakes.Firstly and directly measuring the interlayer binding energy of graphite. We develop a method to directly measure the adhesion energy of solids. By exploring the structure superlubricity mechanism of graphite nano-osocillator, we design and assemble a graphite nano-step and nano-cantilever with atomic smooth surfaces to successfully and firstly measure the interlayer binding energy of graphite. The method is expected to become a general method to study the interaction between graphenes and substrates.Study on the self-cleaning behaviour of graphite nano-osocillator. The extremely high specific surface area of graphene resulting in the severly surface adsorption and contamination, which is detriment to the performances of graphene devices. By exploring the atomic smooth surface of graphite, we succesfully use a graphite nanoeraser to clean organic remainders and deposited amorphous carbon on the surface of HOPG and bilayer graphene. The study also shows that the self-retraction motion of graphite flakes is a self-cleaning process, which will greatly reduce the dependence of micro-nano devices on their environments.
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