Influence of a Top Crust of Entangled Nanotubes on the Structure of Vertically Aligned Forests of Single-Walled Carbon Nanotubes

Zhang, Liang; Li, Zhongrui; Tan, Yongqiang; Lolli, Giulio; Sakulchaicharoen, Nataphan; Requejo, Félix G.; Mun, B. S.; Resasco, Daniel E.

doi:10.1021/cm061783b

Cited by 63 publications

(48 citation statements)

References 24 publications

(39 reference statements)

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“…The measured, single-walled CNT films have a disordered and dense crust layer on top of an aligned middle region. This is similar to observations of multiwalled CNT films in past work (21,27,34). Our single-walled CNTs have been observed to be denser and stiffer due to a smaller diameter as well as better quality.…”

supporting

confidence: 91%

“…Our previous data for the thickness-dependent in-plane modulus of multiwalled CNT films indicated a strong dependence on the nanotube density and alignment (21), which are linked to the detailed growth details (26)(27)(28). Other approaches, such as mesoscopic simulations or atomistic models, found that CNT networks exhibit unique self-organization, including bending and bundling (29)(30)(31).…”

mentioning

confidence: 96%

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Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films

Won

Gao

Panzer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Reliably routing heat to and from conversion materials is a daunting challenge for a variety of innovative energy technologies--from thermal solar to automotive waste heat recovery systems--whose efficiencies degrade due to massive thermomechanical stresses at interfaces. This problem may soon be addressed by adhesives based on vertically aligned carbon nanotubes, which promise the revolutionary combination of high through-plane thermal conductivity and vanishing in-plane mechanical stiffness. Here, we report the data for the in-plane modulus of aligned single-walled carbon nanotube films using a microfabricated resonator method. Molecular simulations and electron microscopy identify the nanoscale mechanisms responsible for this property. The zipping and unzipping of adjacent nanotubes and the degree of alignment and entanglement are shown to govern the spatially varying local modulus, thereby providing the route to engineered materials with outstanding combinations of mechanical and thermal properties.nanostructured materials | van der Waals | thermal interface materials | thermoelectrics | energy conversion N anostructured materials provide unique combinations of properties that promise performance breakthroughs for applications ranging from energy conversion to data storage and computation (1-4). In many cases it is the very unusual combination of two properties (2), neither of which is an extreme value when considered alone, that leads to adoption and major performance benefits. An example is the search for a mechanically compliant thermal conductor that can, for example, link semiconducting materials with the metals used for heat spreading and exchange. A particularly compelling case is thermoelectric waste heat recovery systems (3), for which the interfaces between the thermoelectric materials, electrodes, insulators, and heat exchangers must accommodate enormous, repetitive thermomechanical stress. However, nature does not provide a material combining the necessary high thermal conductivity with the required low elastic modulus (5, 6).Vertically aligned carbon nanotube (CNT) films may combine mechanical compliance with high thermal conductivity (7-18), but there have been few reports of the in-plane modulus of these films and little physical explanation for the wide range for the data (2-300 MPa) (19-25). Our previous data for the thickness-dependent in-plane modulus of multiwalled CNT films indicated a strong dependence on the nanotube density and alignment (21), which are linked to the detailed growth details (26-28). Other approaches, such as mesoscopic simulations or atomistic models, found that CNT networks exhibit unique self-organization, including bending and bundling (29-31). Therefore, relating the nanoscale morphological details to the mechanical properties is critical.Combined experimental, theoretical, and computational techniques applied to the more complex and fundamentally challenging single-walled CNT system are presented in this paper, along with the in-plane data for the modulus for sin...

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supporting

confidence: 91%

mentioning

confidence: 96%

Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films

Won

Gao

Panzer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…A similar rippling pattern can also occur on forests (composed of initially straight nanotubes) that are intentionally subjected to externally applied mechanical compression ex situ [9][10][11]. The interactions between nanotubes have previously been shown to be important for forest morphology [6][7][8][12][13][14][15][16][17][18][19], and will be considered here.…”

Section: Introductionmentioning

confidence: 71%

Origin of periodic rippling during chemical vapor deposition growth of carbon nanotube forests

Vinten

Bond

Marshall

et al. 2011

Carbon

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Origin of periodic rippling during chemical vapor deposition growth of carbon nanotube forestsgrowth conditions, these forests can show a growth instability that gives rise to periodic ripples that are coherent over a forest-sized scale. Previously, we showed that the uniformity and synchronization of the ripples is sufficient for them to behave as diffraction gratings for visible light. Here, we identify the conditions that reproducibly promote the formation of these ripples. We investigate the formation mechanism via ex situ scanning electron microscopy and in situ optical imaging. While the rippling amplitude varies appreciably, the rippling wavelength varies very little and can be estimated from simple mechanical considerations. We provide evidence that the rippling is a consequence of cohesive interactions between nanotubes and the build up of strain, driven by a non-uniform growth rate. The origin of the non-uniform growth rate is explained.Crown

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“…A variety of synthesis conditions have proven effective for preferential vertical growth. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] In particular, CNTs with a desired form of yarn are promising for future textile electronics. Several methods have been tried to produce CNT yarns.…”

Section: Introductionmentioning

confidence: 99%

Criteria for Producing Yarns From Vertically Aligned Carbon Nanotubes

Lee

Han

Chae

et al. 2010

NANO

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Critical yarning conditions from vertically aligned carbon nanotubes (VACNTs) using a chemical vapor deposition have been investigated. VACNTs with a diameter of around 15 nm have been synthesized with a length up to 3.7 mm. The yarning was realized exclusively in a limited range of the CNT lengths of about 170-1500 µm. Although CNTs became long for longer growth times, some of the CNTs were plucked out from the bottom substrate during growth so that the CNT density decreased at later stages of growth, prohibiting continuous yarning by the suppression of interconnection between CNTs at the bottom part of VACNTs.

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Influence of a Top Crust of Entangled Nanotubes on the Structure of Vertically Aligned Forests of Single-Walled Carbon Nanotubes

Cited by 63 publications

References 24 publications

Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films

Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films

Origin of periodic rippling during chemical vapor deposition growth of carbon nanotube forests

Criteria for Producing Yarns From Vertically Aligned Carbon Nanotubes

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