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Mechanical properties of carbon nanotubes and nanofibers
Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. (Fysik)
2012 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Carbon nanotubes (CNTs) have extraordinary electrical and mechanical properties, and many potential applications have been proposed, ranging from nanoscale devices to reinforcement of macroscopic structures. However, due to their small sizes, characterization of their mechanical properties and deformation behaviours are major challenges. Theoretical modelling of deformation behaviours has shown that multi-walled carbon nanotubes (MWCNTs) can develop ripples in the walls on the contracted side when bent above a critical curvature. The rippling is reversible and accompanied by a reduction in the bending stiffness of the tubes. This behaviour will have implications for future nanoelectromechanical systems (NEMS). Although rippling has been thoroughly modelled there has been a lack of experimental data thus far. In this study, force measurements have been performed on individual MWCNTs and vertically aligned carbon nanofibers (VACNFs). This was accomplished by using a custom-made atomic force microscope (AFM) inside a scanning electron microscope (SEM). The measurements were done by bending free-standing MWCNTs/VACNFs with the AFM sensor in a cantilever-to-cantilever fashion, providing force-displacement curves. From such curves and the MWCNT/VACNF dimensions, measured from SEM-images, the critical strain for the very onset of rippling and the Young’s modulus, E, could be obtained. To enable accurate estimations of the nanotube diameter, we have developed a model of the SEM-image formation, such that intrinsic diameters can be retrieved. We have found an increase in the critical strain for smaller diameter tubes, a behaviour that compares well with previous theoretical modelling. VACNFs behaved very differently, as they did not display any rippling and had low bending stiffnesses due to inter-wall shear. We believe that our findings will have implications for the design of future NEMS devices that employ MWCNTs and VACNFs.

sted, utgiver, år, opplag, sider
Karlstad: Karlstad University Press, 2012. , s. 60
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2012:18
Emneord [en]
atomic force microscopy, bending, carbon nanotubes, deformation, scanning electron microscopy, Young's modulus, carbon nanofibers, mechanical properties
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
URN: urn:nbn:se:kau:diva-12925ISBN: 978-91-7063-422-2 (tryckt)OAI: oai:DiVA.org:kau-12925DiVA, id: diva2:517153
Presentation
2012-06-08, 21A342, Karlstads universitet, Karlstad, 10:15 (engelsk)
Opponent
Veileder
Forskningsfinansiär
Swedish Research Council, 2010-4324
Merknad

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

Tilgjengelig fra: 2012-05-24 Laget: 2012-04-16 Sist oppdatert: 2015-09-24bibliografisk kontrollert
Delarbeid
1. Measurements of the critical strain for rippling in carbon nanotubes
Åpne denne publikasjonen i ny fane eller vindu >>Measurements of the critical strain for rippling in carbon nanotubes
2011 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, Vol. 98, nr 18, s. 3 pages-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We report measurements of the bending stiffness in free standing carbon nanotubes, using atomic force microscopy inside a scanning electron microscope. Two regimes with different bending stiffness were observed, indicative of a rippling deformation at high curvatures. The observed critical strains for rippling were in the order of a few percent and comparable to previous modeling predictions. We have also found indications that the presence of defects can give a higher critical strain value and a concomitant reduction in Youngs modulus.

sted, utgiver, år, opplag, sider
American Institute of Physics, 2011
Emneord
Carbon nanotubes, mechanical properties, rippling, atomic force microscopy (AFM), scanning electron microscopy (SEM)
HSV kategori
Forskningsprogram
Materialteknik; Fysik
Identifikatorer
urn:nbn:se:kau:diva-10738 (URN)10.1063/1.3587613 (DOI)000290392300048 ()
Tilgjengelig fra: 2012-02-08 Laget: 2012-02-08 Sist oppdatert: 2019-07-11bibliografisk kontrollert
2. Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.
Åpne denne publikasjonen i ny fane eller vindu >>Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.
2013 (engelsk)Inngår i: Ultramicroscopy, ISSN 0304-3991, Vol. 124, s. 35-39Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present a detailed analysis of the image formation mechanisms that are involved in the imaging of carbon nanotubes with scanning electron microscopy (SEM). We show how SEM images can be modelled by accounting for surface enhancement effects together with the absorption coefficient for secondary electrons, and the electron-probe shape. Images can then be deconvoluted, enabling retrieval of the intrinsic nanotube dimensions. Accurate estimates of their dimensions can thereby be obtained even for structures that are comparable to the electron-probe size (on the order of 2 nm). We also present a simple and robust model for obtaining the outer diameter of nanotubes without any detailed knowledge about the electron-probe shape.

sted, utgiver, år, opplag, sider
Elsevier, 2013
Emneord
Scanning electron microscopy; Carbon nanotubes; Imaging mechanisms; Deconvolution; Electron-probe shape
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
urn:nbn:se:kau:diva-16425 (URN)10.1016/j.ultramic.2012.08.012 (DOI)000311823700006 ()23142742 (PubMedID)
Forskningsfinansiär
Swedish Research Council, 2010-4324
Tilgjengelig fra: 2014-02-21 Laget: 2013-01-18 Sist oppdatert: 2019-07-12bibliografisk kontrollert
3. Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers
Åpne denne publikasjonen i ny fane eller vindu >>Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers
Vise andre…
2013 (engelsk)Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 19Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We have measured the bending stiffness of as-grown vertically aligned carbon nanofibers using atomic force microscopy inside a scanning electron microscope. We show that the assumption of a uniform internal structure is inadequate in describing nanofibers mechanical properties and that a dual phase model is needed. We present a model in which different Young’s moduli are assigned to the inner graphitic core and the outer amorphous carbon shell and show that it provides a better fit to the measurements. We obtain values of 11±8 GPa and 63±14 GPa for the Young’s modulus of the inner core and the outer shell, respectively.

sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2013
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
urn:nbn:se:kau:diva-13391 (URN)10.1063/1.4803853 (DOI)000319295200052 ()
Tilgjengelig fra: 2012-05-28 Laget: 2012-05-28 Sist oppdatert: 2017-08-11bibliografisk kontrollert

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