Ballistic-diffusive phonon heat transport across grain boundaries
Date
2017-09-01
Authors
Chen, Xiang
Li, Weixuan
Li, Yang
Yang, Shengfeng
Zheng, Zexi
McDowell, David L.
Chen, Youping
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Elsevier Ltd.
Abstract
The propagation of a heat pulse in a single crystal and across grain boundaries (GBs) is simulated using a concurrent atomistic-continuum method furnished with a coherent phonon pulse model. With a heat pulse constructed based on a Bose-Einstein distribution of phonons, this work has reproduced the phenomenon of phonon focusing in single and polycrystalline materials. Simulation results provide visual evidence that the propagation of a heat pulse in crystalline solids with or without GBs is partially ballistic and partially diffusive, i.e., there is a co-existence of ballistic and diffusive thermal transport, with the long-wavelength phonons traveling ballistically while the short-wavelength phonons scatter with each other and travel diffusively. To gain a quantitative understanding of GB thermal resistance, the kinetic energy transmitted across GBs is monitored on the fly and the time-dependent energy transmission for each specimen is measured; the contributions of coherent and incoherent phonon transport to the energy transmission are estimated. Simulation results reveal that the presence of GBs modifies the nature of thermal transport, with the coherent long-wavelength phonons dominating the heat conduction in materials with GBs. In addition, it is found that phonon-GB interactions can result in reconstruction of GBs.
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Comments
This is a manuscript of an article published as Chen, Xiang, Weixuan Li, Liming Xiong, Yang Li, Shengfeng Yang, Zexi Zheng, David L. McDowell, and Youping Chen. "Ballistic-diffusive phonon heat transport across grain boundaries." Acta Materialia 136 (2017): 355-365. DOI: 10.1016/j.actamat.2017.06.054. Copyright 2017 Acta Materialia Inc. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Posted with permission.