One-directional thermal transport in densely aligned single-wall carbon nanotube films

Yamaguchi, Shingi; Tsunekawa, Issei; Komatsu, Natsumi; Gao, Weilu; Shiga, Takuma; Kodama, Takashi; Kono, Junichiro; Shiomi, Junichiro

doi:10.1063/1.5127209

Cited by 33 publications

(49 citation statements)

References 62 publications

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“…The measured 𝜂 CNF was 3.46±0.15 (N=3), and correspondingly the 𝜅 ∥ of CNF (𝜅 CNF, ∥ ) was 0.95±0.04 W m -1 K -1 . To validate these values, 𝜅 CNF,⊥ and 𝜅 CNF, ∥ of self-standing CNF film were also measured by laser flash analysis (LFA) 31,32 and T-type method [33][34][35] , respectively. The details of each method are described in Supplementary Material.…”

Section: Resultsmentioning

confidence: 99%

Anisotropic thermal conductivity measurement of organic thin film with bidirectional 3ω method

Yamaguchi

Shiga

Ishioka

et al. 2021

Review of Scientific Instruments

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Organic thin film materials with molecular ordering are gaining attention as they exhibit semiconductor characteristics. When using them for electronics, the thermal management becomes 2 important, where heat dissipation is directional owning to the anisotropic thermal conductivity arising from the molecular ordering. However, it is difficult to evaluate the anisotropy by simultaneously measuring in-plane and cross-plane thermal conductivities of the film on a substrate, because the film is typically as thin as tens to hundreds of nanometers and its in-plane thermal conductivity is low. Here, we develop a novel bidirectional 3ω system that measures the anisotropic thermal conductivity of thin films by patterning two metal wires with different widths and preparing the films on top, and extracting the in-plane and cross-plane thermal conductivities using the difference in their sensitivities to the metal-wire width. Using the developed system, the thermal conductivity of spin-coated poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with thickness of 70 nm was successfully measured. The measured in-plane thermal conductivity of PEDOT:PSS film was as high as 2.9 W m -1 K -1 presumably due to the high structural ordering, giving anisotropy of 10. The calculations of measurement sensitivity to the film thickness and thermal conductivities suggest that the device can be applied to much thinner films by utilizing metal wires with smaller width.

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Section: Resultsmentioning

confidence: 99%

Anisotropic thermal conductivity measurement of organic thin film with bidirectional 3ω method

Yamaguchi

Shiga

Ishioka

et al. 2021

Review of Scientific Instruments

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“…The use of oriented dye molecules in luminescent solar concentrators increases emission into preferred waveguide modes, thereby increasing their optical quantum efficiency 3 . CNT buckypapers, films and fibers aligned in‐situ or by post‐processing exhibit considerable enhancements in their electrical and thermal conductivities, carrier mobility, current carrying capacities, tensile strengths and elastic moduli 4–12 . The degree of internal alignment is therefore considered an important metric to understand structure–property relations in macroscopic materials.…”

Section: Introductionmentioning

confidence: 99%

Quantifying alignment in carbon nanotube yarns and similar two‐dimensional anisotropic systems

Kaniyoor

Gspann

Mizen

et al. 2021

J of Applied Polymer Sci

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The uniaxial orientational order in a macromolecular system is usually specified using the Hermans factor which is equivalent to the second moment of the system's orientation distribution function (ODF) expanded in terms of Legendre polynomials. In this work, we show that for aligned materials that are two‐dimensional (2D) or have a measurable 2D intensity distribution, such as carbon nanotube (CNT) textiles, the Hermans factor is not appropriate. The ODF must be expanded in terms of Chebyshev polynomials and therefore, its second moment is a better measure of orientation in 2D. We also demonstrate that both orientation parameters (Hermans in three dimensional (3D) and Chebyshev in 2D) depend not only on the respective full‐width‐at‐half‐maximum of the peaks in the ODF but also on the shape of the fitted functions. Most importantly, we demonstrate a method to rapidly estimate the Chebyshev orientation parameter from a sample's 2D Fourier power spectrum, using an analysis program written in Python which is available for open access. As validation examples, we use digital photographs of dry spaghetti as well as scanning electron microscopy images of direct‐spun carbon nanotube fibers, proving the technique's applicability to a wide variety of fibers and images.

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“…Here, κ || is the thermal conductivity along the molecular backbone. This "heat trap" effect was observed at a very high temperatures of T > 10 3 K. However, room temperature experiments have also yielded relatively low values, such as κ || ≃ 0.5 − 1.2 Wm −1 K −1 for CNT forests [18], κ || ≃ 100 Wm −1 K −1 for CNT bundles [19] or κ || ≃ 43 Wm −1 K −1 for CNT sheets [20]. We note that the observed influence of crowding on κ || in CNT forests and sheets may not be a system specific phenomenon.…”

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confidence: 98%

“…Understanding heat transport in quasi-one dimensional materials (Q1DMs) is a scientifically major problem [12,13], and becomes even more challenging when dealing with arrays of Q1DMs, such as forests [14][15][16][17][18], bundles [19], sheets [20], and fibers [21,22]. Here, the complex molecular structure of an array introduces entropic disorder and thus controls its physical properties.…”

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Reduced thermal conductivity in molecular forests

Bhardwaj,

Phani,

Nojeh

et al. 2020

Preprint

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One-directional thermal transport in densely aligned single-wall carbon nanotube films

Abstract: See supplementary material for additional information regarding the synthesis method for CNT films, experimental setup, theoretical equation for thermal measurement, details for AGF calculation and absolute values of experiment/simulation data.

Cited by 33 publications

References 62 publications

Anisotropic thermal conductivity measurement of organic thin film with bidirectional 3ω method

Anisotropic thermal conductivity measurement of organic thin film with bidirectional 3ω method

Quantifying alignment in carbon nanotube yarns and similar two‐dimensional anisotropic systems

Reduced thermal conductivity in molecular forests

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