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Title: Thermal anisotropy enhanced by phonon size effects in nanoporous materials

While thermal anisotropy is a desirable materials property for many applications, including transverse thermoelectrics and thermal management in electronic devices, it remains elusive in practical natural compounds. In this work, we show how nanoporous materials with anisotropic pore lattices can be used as a platform for inducing strong heat transport directionality in isotropic materials. Using density functional theory and the phonon Boltzmann transport equation, we calculate the phonon-size effects and thermal conductivity of nanoporous silicon with different anisotropic pore lattices. Here, our calculations predict a strong directionality in the thermal conductivity, dictated by the difference in the pore-pore distances, i.e., the phonon bottleneck, along the two Cartesian axes. Using Fourier’s law, we also compute the diffusive heat transport for the same geometries obtaining significantly smaller anisotropy, revealing the crucial role of phonon-size effects in tuning thermal transport directionality. Besides enhancing our understanding of nanoscale heat transport, our results demonstrate the promise of nanoporous materials for modulating anisotropy in thermal conductivity.
Authors:
 [1] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Publication Date:
Grant/Contract Number:
SC0001299; DESC0001
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 9; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1466007
Alternate Identifier(s):
OSTI ID: 1348268

Romano, Giuseppe, and Kolpak, Alexie M. Thermal anisotropy enhanced by phonon size effects in nanoporous materials. United States: N. p., Web. doi:10.1063/1.4976540.
Romano, Giuseppe, & Kolpak, Alexie M. Thermal anisotropy enhanced by phonon size effects in nanoporous materials. United States. doi:10.1063/1.4976540.
Romano, Giuseppe, and Kolpak, Alexie M. 2017. "Thermal anisotropy enhanced by phonon size effects in nanoporous materials". United States. doi:10.1063/1.4976540. https://www.osti.gov/servlets/purl/1466007.
@article{osti_1466007,
title = {Thermal anisotropy enhanced by phonon size effects in nanoporous materials},
author = {Romano, Giuseppe and Kolpak, Alexie M.},
abstractNote = {While thermal anisotropy is a desirable materials property for many applications, including transverse thermoelectrics and thermal management in electronic devices, it remains elusive in practical natural compounds. In this work, we show how nanoporous materials with anisotropic pore lattices can be used as a platform for inducing strong heat transport directionality in isotropic materials. Using density functional theory and the phonon Boltzmann transport equation, we calculate the phonon-size effects and thermal conductivity of nanoporous silicon with different anisotropic pore lattices. Here, our calculations predict a strong directionality in the thermal conductivity, dictated by the difference in the pore-pore distances, i.e., the phonon bottleneck, along the two Cartesian axes. Using Fourier’s law, we also compute the diffusive heat transport for the same geometries obtaining significantly smaller anisotropy, revealing the crucial role of phonon-size effects in tuning thermal transport directionality. Besides enhancing our understanding of nanoscale heat transport, our results demonstrate the promise of nanoporous materials for modulating anisotropy in thermal conductivity.},
doi = {10.1063/1.4976540},
journal = {Applied Physics Letters},
number = 9,
volume = 110,
place = {United States},
year = {2017},
month = {2}
}

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