Type of Document Dissertation Author Shen, Guoan Author's Email Address email@example.com URN etd-10312006-000022 Title Effect of Interfaces on the Thermal, Mechanical and Chemical Characteristics of Carbon Nanotubes Degree Doctor of Philosophy Department Mechanical Engineering, Department of Advisory Committee
Advisor Name Title Dr. Anter El-Azab Committee Member Dr. Chiang Shih Committee Member Dr. Leon van Dommelen Committee Member Dr. Namas Chandra Committee Member Dr. Petru Andrei Committee Member Keywords
- Multiscale simulation
- load transfer
- carbon nanotubes
- molecular dynamics simulation
Date of Defense 2006-10-09 Availability unrestricted AbstractThe primary focus of this work is to explore the effect of interface on thermal, mechanical, and chemical properties of carbon nanotubes (CNTs) and the methods to modify the interface between CNTs and CNTs based composites.
CNTs are potentially promising fibers for ultra-high-strength composites. The load transfer between the inner and outer tubes in multiwall nanotubes (MWNTs) has to be clearly understood to realize the potential of MWNTs in composites and other applications such as nano-springs, and nano-bearings. This dissertation studies the load transfer between the walls of MWNTs in both tension and compression using molecular dynamics simulations. It is found that only the minimal load is transferred to the inner nanotube in tension. The load transfer of capped nanotubes in compression is much higher than in tension. The presence of a few interstitial atoms between the walls of MWNTs can significantly improve the stiffness and enhance the load transfer to the inner nanotubes in both tension and compression.
The modification of the interface of CNTs is a key factor for effectively using CNTs in many applications. The use of molecular statics and dynamics helps exploring ion irradiation as a method for functionalization of CNTs. It is found that ion bombardment of single and
Multiwall carbon nanotubes creates vacancies and defects, which can act as high-energy sites for further chemical reactions; furthermore, ion irradiation of CNTs embedded in polymer matrix creates chemical attachments between CNTs and polymer matrix, enhancing the compositing process. Mechanical property simulations based on tension and pullout tests indicate that the chemical links between constituents in CNT–polymer systems result in higher load transfer, and hence, better composite properties.
The effect of the interface turns out to be very crucial for printing in nanolithography processes. Molecular dynamics simulation is applied to extract interface properties, such as friction and adhesion, in nanoscale; later, the properties are input into a large-scale FEM model. As found, the protrusion problem is caused by many factors, such as strength of polymer at high temperature, thermal expansion properties, and depth of metal.
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