Thermal transport in MWCNT sheets and yarns

Aliev, Ali E.; Guthy, Csaba; Zhang, Mei; Fang, Shaoli; Zakhidov, Anvar A.; Fischer, J. E.; Baughman, Ray H.

doi:10.1016/j.carbon.2007.10.010

Cited by 182 publications

(147 citation statements)

References 22 publications

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“…It is well known that the conductivity parallel to the tubes (namely, perpendicular to the growth substrate) is higher than the conductivity perpendicular to the tube axis (namely, parallel to the growth substrate). 19 However, the CNTs grown by thermal CVD are composed of a lot of defects which are detrimental to the conductivity. Therefore, if the junctions or contact area between the CNTs increase, there are more chances for the electron conducting around the critical faults in the CNT and reduce the total resistance for electron conducting.…”

Section: Resultsmentioning

confidence: 99%

Field-Emission Characteristics of the Densified Carbon Nanotube Pillars Array

Wang

Liao

Cheng

2016

ECS J. Solid State Sci. Technol.

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In this study, the densification effects of carbon nanotube (CNT) pillar array have been proved to significantly increase the field emission characteristics. Without damage to the crystallinity of CNTs, the CNT density of each densified pillar can be increased about 6.25 times as compared to the as-grown ones. Consequently, the densified CNT pillars exhibit higher electrical conductivity, better contacts, and more emission sites, which are favorable to the field emission properties. What's more, the optimum field emission characteristics occur at the condition of R/H = 2 with H = 30 μm for both of the as-grown and densified samples because of the minimum screening effect and the proper aspect ratio. Therefore, the field emitter with densified CNT pillars of 30-μm in height and 60-μm in interspacing possesses the lowest turn on and threshold fields of 0.73 and 1.29 V/μm, respectively. It implies that the densified CNT pillars are promising for the field-emission applications. Field emission lighting (FEL) has emerged as a leading contender in lighting technologies, because it combines the conventional features of cathode ray tubes (CRTs) and flat panels. The field emitters provide cold electrons to bombard phosphors in an anode plate to generate high luminance. In the last decade, various one-dimensional (1D) nanomaterials with high aspect ratio have been intensively investigated for field emitter arrays (FEAs) 1-3 Among these candidates, carbon nanotubes (CNTs) 4-9 have attracted a great deal of attention as an electron-emitting material owing to their high aspect ratio, high thermal conductivity, large current capability, chemical inertness, and high mechanical strength. 10In general, the field-emission (FE) characteristics for an individual CNT are considered to be better than that for the CNT films because of avoiding the screen effect. For an individual CNT, the extremely high aspect ratio is ideal for the electron emission. What's more, the optimal ratio of intertube distance to the CNT height for an individual CNT was reported by Nilsson et al. 11 to be 2 for FE characteristics. But Suh et al.12 also reported that the FE characteristics of a CNT film should be enhanced with increasing CNT height. Therefore, it is critical to control the CNT height and intertube distance to get the optimal FE characteristic in unit area. However, it is very difficult to grow very long distinct vertically-aligned CNT and precisely control the intertube distance for the individual CNTs. Thus, the CNT pillar structures are generally used for the practical purposes since it is easy to control the height and spacing between the pillars, which can effectively reduce the screen effect as compared to the CNT film structure.In recent years, people used the capillary force during the evaporation of liquids to effectively pull the CNTs together, which can significantly improve the properties of the CNT forests. For instance, De Volder et al. 13 used this mechanism to demonstrate better mechanical stiffness and electrical conductiv...

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Section: Resultsmentioning

confidence: 99%

Field-Emission Characteristics of the Densified Carbon Nanotube Pillars Array

Wang

Liao

Cheng

2016

ECS J. Solid State Sci. Technol.

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“…Aligning carbon nanotubes within such preformed arrays can improve mechanical [4,5,6,7], thermal [8,9,10,11] and electrical [12,13,14] properties. A number of studies have shown an linear increase in tensile modulus and strength with an increase in orientation ( Figure 1).…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…Raman spectra were processed with both WiRE 4.1 software and Matlab. The CNT orientation was calculated by collecting polarised spectra, and applying Equation (8). The incident laser light was polarised by applying a half wave plates prior to interaction with the sample and analyser.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Mapping carbon nanotube orientation by fast fourier transform of scanning electron micrographs

Brandley

Greenhalgh

Shaffer

et al. 2018

Carbon

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Please cite this article as: E. Brandley, E.S. Greenhalgh, M.S.P. Shaffer, Q. Li, Mapping carbon nanotube orientation by fast fourier transform of scanning electron micrographs, Carbon (2018), doi: 10.1016/j.carbon.2018.04.063. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractA novel method of applying a two-dimensional Fourier transform (2D-FFT) to SEM was developed to map the CNT orientation in pre-formed arrays. Local 2D-FFTs were integrated azimuthally to determine an orientation distribution function and the associated Herman parameter. This approach provides data rapidly and over a wide range of lengthscales.Although likely to be applicable to a wide range of anisotropic nanoscale structures, the method was specifically developed to study CNT veils, a system in which orientation critically controls mechanical properties. Using this system as a model, key parameters for the 2D-FFT analysis were optimised, including magnification and domain size; a model set of CNT veils were pre-strained to 5%, 10% and 15%, to vary the alignment degree. The algorithm confirmed a narrower orientation distribution function and increasing Herman parameter, with increasing pre-strain.To validate the algorithm, the local orientation was compared to that derived from a common polarised Raman spectroscopy. Orientation maps of the Herman parameter, derived by both methods, showed good agreement. Quantitatively, the mean Herman parameter calculated using the polarised Raman spectroscopy was 0.42±0.004 compared to 0.32±0.002 for the 2D-FFT method, with a correlation coefficient of 0.73. Possible reasons for the modest and systematic discrepancy were discussed.

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“…The Multi Walled Carbon Nanotube (MWCNT) forest was synthesized by Catalytic Chemical Vapor Deposition (CCVD) using acetylene gas as the carbon source [15]. Carbon nanotubes, in the 300 μm tall forest, typically had diameters of about 10 nm.…”

Section: A Yarn Fabricationmentioning

confidence: 99%

Microwave Characterization of Carbon Nanotube Yarns For UWB Medical Wireless Body Area Networks

Abbas

Sevimli

Heimlich

et al. 2013

IEEE Trans. Microwave Theory Techn.

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Carbon nanotube (CNT) yarns are novel CNT-based materials that extend the advantages of CNT from the nanoscale to macroscale applications. In this study, we have modeled CNT yarns as potential data transmission lines. Test structures have been designed to measure electrical properties of CNT yarns, which are attached to these test structures using gold paste. DC testing and microwave S-parameter measurements have been conducted for characterization. The observed frequency independent resistive behavior of the CNT yarn is a very promising indicator that this material, with its added values of mechanical resilience and thermal conductivity, could be invaluable for a range of applications such as body area networks. A model is developed for the CNT yarn, which fits the measured data collected and agrees in general with similar data for non-yarn CNTs.

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Thermal transport in MWCNT sheets and yarns

Cited by 182 publications

References 22 publications

Field-Emission Characteristics of the Densified Carbon Nanotube Pillars Array

Field-Emission Characteristics of the Densified Carbon Nanotube Pillars Array

Mapping carbon nanotube orientation by fast fourier transform of scanning electron micrographs

Microwave Characterization of Carbon Nanotube Yarns For UWB Medical Wireless Body Area Networks

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