Ultralow and anisotropic thermal conductivity in graphene phononic metamaterials

1Thermal conductivity of GPMs is lower than GNRs in different in-plane directions.2GPMs have stronger anisotropy in thermal conductance, compared with GNRs.3Phonon scattering, localization and local resonance reduce thermal conductivity.4Anisotropic phonon contributions and relaxation times lead to...

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Bibliographic Details
Published in:	International journal of heat and mass transfer Vol. 196; p. 123227
Main Authors:	Cui, Liu, Guo, Xinwang, Yu, Qingsheng, Wei, Gaosheng, Du, Xiaoze
Format:	Journal Article
Language:	English
Published:	Elsevier Ltd 01-11-2022
Subjects:	Graphene phononic metamaterials Molecular dynamics Phonon local resonance Thermal anisotropy Thermal conductivity Molecular dynamics Thermal conductivity Phonon local resonance Graphene phononic metamaterials Thermal anisotropy
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Summary:	1Thermal conductivity of GPMs is lower than GNRs in different in-plane directions.2GPMs have stronger anisotropy in thermal conductance, compared with GNRs.3Phonon scattering, localization and local resonance reduce thermal conductivity.4Anisotropic phonon contributions and relaxation times lead to thermal anisotropy.5Shorter and narrower pillars reduce thermal conductivity and increase anisotropy. Phononic metamaterials based on the idea of phonon coherent resonance attract increasing research attention because of their unique properties. In this paper, we have studied the heat transport in graphene phononic metamaterials (GPMs, pillared graphene nanoribbons) using molecular dynamics simulations. The results show that, GPMs have lower thermal conductivities in the different in-plane directions and stronger anisotropy in thermal conductance, compared with graphene nanoribbons (GNRs). As the temperature decreases or the height and width of pillar increases, the GPM thermal conductivity in both directions decreases and the anisotropic ratio increases. The pillar-driven suppression of thermal conductivity along the periodic direction is attributed to the phonon localization and the local resonance leading to the flat bands and band gaps, while the reduction in thermal conductivity along the aperiodic direction is due to the phonon boundary scattering. The thermal anisotropy results from the anisotropic phonon relaxation times and the anisotropic contributions of low-frequency-phonons. Our findings reveal the phonon transport mechanisms of GPMs in different directions, and shed some light on the GPM potential for thermoelectric and directional heat management applications. [Display omitted]
ISSN:	0017-9310 1879-2189
DOI:	10.1016/j.ijheatmasstransfer.2022.123227