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Jackman, Henrik
Publications (10 of 11) Show all publications
Jackman, H., Krakhmalev, P. & Svensson, K. (2015). Mechanical behavior of carbon nanotubes in the rippled and buckled phase. Journal of Applied Physics, 117(8), 084318
Open this publication in new window or tab >>Mechanical behavior of carbon nanotubes in the rippled and buckled phase
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, p. 084318-Article in journal (Refereed) Published
Abstract [en]

We have studied the mechanical behavior of multi-walled carbon nanotubes for bending strains beyond the onset for rippling and buckling. We found a characteristic drop in the bending stiffness at the rippling and buckling onset and the relative retained stiffness was dependent on the nanotube dimensions and crystallinity. Thin tubes are more prone to buckle, where some lose all of their bending stiffness, while thicker tubes are more prone to ripple and on average retain about 20\% of their bending stiffness. In defect rich tubes the bending stiffness is very low prior to rippling but these tubes retain up to 70\% of their initial bending stiffness.

Keywords
carbon nanotubes, Young's modulus, bending stiffness, buckling, rippling, nonlinear behavior
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-35340 (URN)10.1063/1.4913701 (DOI)000351132500050 ()
Funder
Swedish Research Council, 2010-4324
Available from: 2015-03-07 Created: 2015-03-07 Last updated: 2019-07-11Bibliographically approved
Jackman, H., Krakhmalev, P. & Svensson, K. (2014). Large variations in the onset of rippling in concentric nanotubes.. Applied Physics Letters, 104, Article ID 021910.
Open this publication in new window or tab >>Large variations in the onset of rippling in concentric nanotubes.
2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, article id 021910Article in journal (Refereed) Published
Abstract [en]

We present a detailed experimental study of the onset of rippling in highly crystalline carbon nanotubes. Modeling has shown that there should be a material constant, called the critical length, describing the dependence of the critical strain on the nanotube outer radius. Surprisingly, we have found very large variations, by a factor of three, in the critical length. We attribute this to a supporting effect from the inner walls in multiwalled concentric nanotubes. We provide an analytical expression for the maximum deflection prior to rippling, which is an important design consideration in nanoelectromechanical systems utilizing nanotubes.

Keywords
nanotubes, rippling, mechanical stiffness, TEM, AFM
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-30942 (URN)10.1063/1.4861605 (DOI)000330431000038 ()
Funder
Swedish Research Council, 2010-4324
Available from: 2014-01-20 Created: 2014-01-20 Last updated: 2017-12-06Bibliographically approved
Jackman, H. (2014). Mechanical behaviour of carbon nanostructures. (Doctoral dissertation). Karlstad: Karlstads universitet
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
Keywords
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: 2017-08-11Bibliographically approved
Ghavanini, F., Jackman, H., Lundgren, P., Svensson, K. & Enoksson, P. (2013). Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers. Journal of Applied Physics, 113(19)
Open this publication in new window or tab >>Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers
Show others...
2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 19Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2013
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-13391 (URN)10.1063/1.4803853 (DOI)000319295200052 ()
Available from: 2012-05-28 Created: 2012-05-28 Last updated: 2017-08-11Bibliographically approved
Jackman, H., Krakhmalev, P. & Svensson, K. (2013). Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.. Ultramicroscopy, 124, 35-39
Open this publication in new window or tab >>Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.
2013 (English)In: Ultramicroscopy, ISSN 0304-3991, Vol. 124, p. 35-39Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Scanning electron microscopy; Carbon nanotubes; Imaging mechanisms; Deconvolution; Electron-probe shape
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-16425 (URN)10.1016/j.ultramic.2012.08.012 (DOI)000311823700006 ()23142742 (PubMedID)
Funder
Swedish Research Council, 2010-4324
Available from: 2014-02-21 Created: 2013-01-18 Last updated: 2019-07-12Bibliographically approved
Jackman, H., Krakhmalev, P. & Svensson, K. (2012). High resolution SEM imaging of carbon nanotubes: deconvolution and retrieval of intrinsic nanotube dimensions. In: : . Paper presented at NT12 - The Thirteenth International Conference on Science and Application of Nanotubes, 24-26 June, Brisbane, Australia.
Open this publication in new window or tab >>High resolution SEM imaging of carbon nanotubes: deconvolution and retrieval of intrinsic nanotube dimensions
2012 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Characterizing physical properties of individual nanotubes is crucial for their implementation in nano electromechanical systems (NEMS). This requires measurements on suspended or free-standing structures together with accurate determination of the nanotubes dimensions. In situ methods are often used where physical measurements are performed inside electron microscopes [1-3]. Transmission electron microscopy (TEM) has the advantage of high resolution, providing accurate determination of both dimensions and the internal structure. The space inside a TEM is however rather restricted, leaving limited room for additional probes [4]. Scanning electron microscopy (SEM) on the other hand, has a large specimen chamber which facilitates the addition of probes, but the image resolution is lower, making the evaluation of material properties less accurate or even impossible for very thin nanotubes [1]. One way to solve this is to first measure the physical properties inside an SEM, and then determine the diameter using a TEM afterwards [1]. This approach requires transfer of the nanotube from the SEM to a suitable TEM sample holder, and analysis of the same sample-location in both instruments. It would thereby be advantageous to obtain accurate structural information directly inside the SEM [2]. We have studied the mechanisms involved in SEM image formation of small multiwalled nanotubes, 2-5 nm in diameter. The electron-probe shape in an SEM broadens the sample details, and the image can be seen as a convolution of the secondary electron yield at each sample position and the probe shape. By comparing SEM and TEM images, we found that the probe intensity profile was best described by a linear combination of Gaussian and Lorentzian distributions. Using the obtained probe shape, the SEM images could then be deconvoluted to reveal more details, including the inner diameter in some cases. We also show how the outer diameter can be obtained by differentiating image profiles, a method that does not require any detailed knowledge regarding the probe shape and is reliable down to dimensions comparable to the electron-probe size. This significantly improves the capabilities of in-situ SEM experiments by enabling accurate characterizations of nanofibres inside SEM instruments, without the need for subsequent TEM imaging

National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-15410 (URN)
Conference
NT12 - The Thirteenth International Conference on Science and Application of Nanotubes, 24-26 June, Brisbane, Australia
Funder
Swedish Research Council, 2010-4324
Available from: 2012-11-01 Created: 2012-11-01 Last updated: 2019-07-12Bibliographically approved
Jackman, H. (2012). Mechanical properties of carbon nanotubes and nanofibers. (Licentiate dissertation). Karlstad: Karlstad University Press
Open this publication in new window or tab >>Mechanical properties of carbon nanotubes and nanofibers
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Karlstad: Karlstad University Press, 2012. p. 60
Series
Karlstad University Studies, ISSN 1403-8099 ; 2012:18
Keywords
atomic force microscopy, bending, carbon nanotubes, deformation, scanning electron microscopy, Young's modulus, carbon nanofibers, mechanical properties
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-12925 (URN)978-91-7063-422-2 (ISBN)
Presentation
2012-06-08, 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: 2012-05-24 Created: 2012-04-16 Last updated: 2015-09-24Bibliographically approved
Ghavanini, F., Jackman, H., Svensson, K., Lundgren, P. & Enoksson, P. (2011). Direct Measurement of the Young’s Modulus of Individual Vertically Aligned Carbon Nanofibers (VACNFs). Paper presented at NT11 International Conference on the Science and Application of Nanotubes University of Cambridge, Cambridge, 10 – 16 July, 2011.
Open this publication in new window or tab >>Direct Measurement of the Young’s Modulus of Individual Vertically Aligned Carbon Nanofibers (VACNFs)
Show others...
2011 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Vertically aligned carbon nanofibers (VACNFs) are synthesized in a plasma-enhanced chemical vapor deposition process (PECVD) in which the position, diameter, length, and alignment of individual nanofibers can be controlled accurately. This has provided an unprecedented opportunity to realize a new bottom-up-engineered material with excellent mechanical and electrical properties which could exploit the third dimension at a reasonable cost. VACNFs have been already employed in a number of applications including electron emitters, gene delivery arrays, and nanoelectromechanical systems. However, no direct measurement of the Young’s modulus of VACNFs has been reported yet. Qi et al. have used nanoindentation method to measure the collective response of a forest of VACNFs with a distribution in length and diameter of the constituent nanofibers. Kaul et al., have reported in situ uniaxial compression tests on individual VACNFs but they have not provided enough information to evaluate the accuracy of their measurements. Indirect estimation of the VACNFs Young’s modulus has also been reported by Eriksson et al. from measurements of the resonance frequency of a nanofiber deposited on top of an excitation electrode. Here, we report on direct measurements of VACNFs Young’s modulus using a piezoresistive atomic force microscope (AFM) cantilever implemented inside a scanning electron microscope (SEM). The VACNFs were grown from Ni catalyst seeds, patterned using electron-beam lithography on top of a stoichiometric TiN underlayer. The VACNFs were grown in a commercially available PECVD chamber (AIXTRON BlackMagic™). The nanofibers were approached from the side and pushed at the tip (resembling a cantilever beam) and force-deflection curves were obtained. By calibrating the AFM sensor the bending stiffness of the nanofiber could be determined. The Young’s modulus was then estimated by taking the nanofibers dimensions into account. The sub-nano Newton force precision provided by the AFM force-sensor together with the fact the individual VACNFs could be observed in the SEM simultaneously during the measurements, has enabled us to measure the nanofibers Young’s modulus with a high precision. Preliminary measurements indicate that VACNFs posses a Young’s modulus between 40 to 100 GPa which is comparable to CVD grown carbon nanotubes of similar diameter

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kau:diva-12395 (URN)
Conference
NT11 International Conference on the Science and Application of Nanotubes University of Cambridge, Cambridge, 10 – 16 July, 2011
Available from: 2012-03-20 Created: 2012-03-20 Last updated: 2014-10-28Bibliographically approved
Jackman, H., Krakhmalev, P. & Svensson, K. (2011). Direct Measurements Of Bending Stiffness And Rippling Phenomena In Free-Standing Carbon Nanotubes. Paper presented at NT11 International Conference on the Science and Application of Nanotubes, University of Cambridge, Cambridge, 10 – 16 July, 2011.
Open this publication in new window or tab >>Direct Measurements Of Bending Stiffness And Rippling Phenomena In Free-Standing Carbon Nanotubes
2011 (English)Conference paper, Published paper (Refereed)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kau:diva-12394 (URN)
Conference
NT11 International Conference on the Science and Application of Nanotubes, University of Cambridge, Cambridge, 10 – 16 July, 2011
Available from: 2012-03-20 Created: 2012-03-20 Last updated: 2019-07-12Bibliographically approved
Jackman, H., Krakhmalev, P. & Svensson, K. (2011). Measurements of the critical strain for rippling in carbon nanotubes. Applied Physics Letters, 98(18), 3 pages
Open this publication in new window or tab >>Measurements of the critical strain for rippling in carbon nanotubes
2011 (English)In: Applied Physics Letters, ISSN 0003-6951, Vol. 98, no 18, p. 3 pages-Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
American Institute of Physics, 2011
Keywords
Carbon nanotubes, mechanical properties, rippling, atomic force microscopy (AFM), scanning electron microscopy (SEM)
National Category
Materials Engineering Physical Sciences
Research subject
Materials Engineering; Physics
Identifiers
urn:nbn:se:kau:diva-10738 (URN)10.1063/1.3587613 (DOI)000290392300048 ()
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2019-07-11Bibliographically approved
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