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Mechanical beviour of carbon nanotubes in the rippled phase
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kau:diva-32067OAI: oai:DiVA.org:kau-32067DiVA: diva2:716850
Funder
Swedish Research Council, 2010-4324
Available from: 2014-05-13 Created: 2014-05-13 Last updated: 2014-05-23Bibliographically approved
In thesis
1. Mechanical behaviour of carbon nanostructures
Open this publication in new window or tab >>Mechanical behaviour of carbon nanostructures
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Abstract

Carbon nanotubes (CNTs) have extraordinary mechanical and electrical properties. Together with their small dimensions and low density, they are attractive candidates for building blocks in future nanoelectromechanical systems and for many other applications. The extraordinary properties are however only attained by perfectly crystalline CNTs and quickly deteriorate when defects are introduced to the structure. The growth technique affects the crystallinity where in general CNTs grown by arc-discharge are close to perfectly crystalline, while CVD-grown CNTs have large defect densities. Mechanical deformation also affects these properties, even without introducing defects. When CNTs are bent they behave similarly to drinking straws, i.e. they buckle or ripple and their bending stiffness drops abruptly.

In this thesis, the mechanical behaviour of individual CNTs and vertically aligned carbon nanofibers (VACNFs) has been studied by performing force measurements inside electron microscopes. Cantilevered CNTs, and VACNFs, were bent using a force sensor, yielding force-deflection curves while their structure was imaged simultaneously.

We have found that CNTs grown by arc-discharge have a high enough crystallinity to possess a Young’s modulus close to the ideal value of 1 TPa. CVD-grown CNTs possess a Young’s modulus that is about one order of magnitude smaller, due to their large defect density. The VACNFs are yet another order of magnitude softer as a result of their cup-stacked internal structure.  We also found that a high defect density will increase the critical strain for the rippling onset and the relative post-rippling stiffness. Multi-walled CNTs with a small inner diameter are less prone to ripple and have a larger relative post-rippling stiffness. Our findings show large variations in the onset of rippling and the bending stiffness before and after rippling. These variations open up possibilities of tailoring the mechanical properties for specific applications.

Abstract [en]

Baksidetext

Carbon nanotubes (CNTs) have extraordinary mechanical and electrical properties. Together with their small dimensions and low density, they are attractive candidates for building blocks in nanoelectromechanical systems (NEMS), and many other applications.  In this thesis the mechanical behaviour of individual CNTs and vertically aligned carbon nanofibers has been studied by performing force measurements inside electron microscopes. We have found that the mechanical behaviour is very sensitive to the defect density and the internal structure of the CNTs. The extraordinary properties are only attained by defect free CNTs and quickly deteriorate if defects are introduced to the structure. Mechanical deformations also alter these properties. Single-walled CNTs behave similarly to drinking straws when bent, i.e. they buckle, while the inner tubes of multi-walled CNTs prevent buckling. Instead a more distributed rippling pattern is created for multi-walled CNTs. Both these deformation behaviours will cause an abrupt drop in the bending stiffness, which is detrimental for many applications. The findings in this work will have implications for the design of future NEMS.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:33
Keyword
carbon nanotubes, CNT, multiwalled carbon nanotubes, MWCNT, rippling, buckling, mechanical properties, transmission electron microscopy, TEM, scanning electron microscopy, SEM, atomic force microscopy, AFM, Young’s modulus, in situ TEM, in situ SEM
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-32041 (URN)978-91-7063-566-3 (ISBN)
Public defence
2014-06-13, 21A342, Karlstads universitet, Karlstad, 10:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2010-4324
Note

Artikel 2 Image formation mechanisms tidigare som manuskript, nu publicerad: urn:nbn:se:kau:diva-16425 (MÅ 150924)

Available from: 2014-05-23 Created: 2014-05-06 Last updated: 2015-11-27Bibliographically approved

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