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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

MODULATION OF THERMOELECTRIC PROPERTIES OF CARBON NANOTUBES USING COHERENT PHONONS

Get access (open in a dialog) DOI: 10.1615/IHTC16.mpe.023752
pages 6103-6110

要約

A recent advance of nanotechnology allows us to design materials in nanoscale. When the length scale of nanostructures in materials reaches in the order of phonon wavelength, wave nature is expected to dominate their thermal transport properties. Despite many attempts to observe such coherent wave nature of phonons in experiments, very few studies have been reported the observation of coherent phonons except for at low temperature (< 10 K) or low frequency (< 1 THz) because phonons easily lose their phase information during scattering processes. Recently, Kodama et al. [Nat. Mater. 16, 892 (2017)] have revealed that thermal conductivity of carbon nanotubes (CNTs) decreases by ~ 60% and peak temperature of temperature dependent thermal conductivity decreases by ~ 50 K due to encapsulation of fullerenes. These results indicate that the encapsulated fullerenes act not as simple phonon scatters like impurities but modulate phonon dispersion of outer single-walled CNTs (SWNTs). Here, we show that fullerene encapsulation modulates coherent wave nature of outer SWNTs due to the periodic radial expansion. The radial expansion leads to softening and hardening of axial and radial modes, respectively, that should be caused by variation of force constants due to the induced strain. Moreover, the periodic strain leads to zone-folding effect and hybridization effect of phonon modes in outer SWNT and encapsulated fullerenes. Our simulations reveal that the encapsulation-induced periodic strain makes an artificial superlattice of CNTs, which provides a new concept of tuning of microscopic thermal transport and strain-thermal engineering.