Characterization of field induced electro-mechanical responses on carbon nanotubes

場效應誘發奈米碳管之機電性質研究

薛森鴻(Sen-Hong Syue)

指導教授 ： 施漢章 ； 徐文光

國立清華大學/工學院/材料科學工程學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00455

摘要

The works presented in this thesis discuss the electric field effects on mechanical properties such as intertube friction, elaborate tube activities in CNT bundle, and the improvement of bundle stiffness as well as the electric properties modulation of carbon nanotubes. Intertube interaction and tube activities will essentially play the significant roles if carbon nanotubes are employed as the primary ingredient in engineering. Current works report not only the estimation of the intertube friction based on the cohesive energy of CNT bundle with the tube displacement arisen from external field, but also a field stiffening CNT bundle associated with nanotube reorganization. Electric field altered chemical potential of CNT bundle are also investigated and the detail mechanism are proposed. The substance of reversible M→S→M transition is verified by theoretical calculation, and is expected to be applied in the future.
Chapter 1 introduces the background of carbon nanotubes in this thesis, including the mechanical properties, deformation mechanism, basic electric properties, metal-semiconductor transition, and doping effects on carbon nanotubes.
Chapter 2 firstly describes the preliminary preparations such as the source of BCNT, which is the selected materials in our works, and the experimental setup for further tests. Secondly, the characterization techniques employed in this study are also introduced.
Chapter 3 demonstrates a straightforward method for evaluating internanotube friction. Field induced displacement of carbon nanotubes is detected within a bundle and intertube friction is calculated via cohesive energy and electromagnetic formula. Tube-tube friction is found to be 1.4 × 10−4 N which is five orders of magnitude greater than the value obtained between adjacent layers within a nanotube.
Chapter 4 exhibits a stiffer CNT bundle structure after electric field treatment, and detail discussion is as follows. Carbon nanotubes are reorganized into close packed bundle via electric field induced intertube displacement and calculation reveals that cohesive energy and modulus of reorganized nanotube bundle are greater than pristine structure by two orders of magnitude.
Chapter 5 displays a metal-semiconductor transition after longitudinal field treatment in a vacuum chamber. A semiconducting phase is temporarily present in doped carbon nanotube after field treatment and underlying mechanism involves chemical potential change and EF movement by field induced charge accumulation. Metallic phase re-emerges as accumulated charges are released.
Chapter 6 concludes the results of our experiments and proposes some feasibly researchable directions

關鍵字

奈米碳管 ； 電場 ； 機械性質 ； 電子性質

並列摘要

無資料

並列關鍵字

carbon nanotube ； electric field ； mechanical property ； electronic property

參考文獻

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