Maximization of thermal conductance at interfaces via exponentially massgraded interlayers
Here, we propose a strategy to potentially best enhance interfacial thermal transport through solid–solid interfaces by adding nanoengineered, exponentially massgraded intermediate layers. This exponential design rule results in a greater enhancement than a linearly massgraded interface. By combining calculations using nonequilibrium Green's functions (NEGF) and nonequilibrium molecular dynamics (NEMD), we investigated the role of impedance matching and anharmonicity in the enhancement in addition to geometric parameters such as the number of layers and the junction thickness. Our analysis shows that the effect on thermal conductance is dominated by the phonon thermalization through anharmonic effects, while elastic phonon transmission and impedance matching play a secondary role. In the harmonic limit, increasing the number of layers results in greater elastic phonon transmission at each individual boundary, countered by the decrease of available conducting channels. Consequently, conductance initially increases with number of layers due to improved bridging, but quickly saturates. The presence of slight anharmonic effects (at very low temperature, T = 2 K) turns the saturation into a monotonically increasing trend. Anharmonic effects can further facilitate interfacial thermal transport through the thermalization of phonons at moderate temperatures. At high temperature, however, the role of anharmonicity as a facilitator of interfacial thermal transportmore »
 Authors:

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 Univ. of Virginia, Charlottesville, VA (United States)
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 U.S. Naval Research Lab. (United States)
 Publication Date:
 Grant/Contract Number:
 AC0500OR22725; Graduate opportunity (GO!) program
 Type:
 Accepted Manuscript
 Journal Name:
 Nanoscale
 Additional Journal Information:
 Journal Name: Nanoscale; Journal ID: ISSN 20403364
 Publisher:
 Royal Society of Chemistry
 Research Org:
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Sponsoring Org:
 USDOE
 Country of Publication:
 United States
 Language:
 English
 Subject:
 36 MATERIALS SCIENCE
 OSTI Identifier:
 1502588
 Alternate Identifier(s):
 OSTI ID: 1501687
Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., and Norris, Pamela M.. Maximization of thermal conductance at interfaces via exponentially massgraded interlayers. United States: N. p.,
Web. doi:10.1039/C8NR09188A.
Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., & Norris, Pamela M.. Maximization of thermal conductance at interfaces via exponentially massgraded interlayers. United States. doi:10.1039/C8NR09188A.
Rastgarkafshgarkolaei, Rouzbeh, Zhang, Jingjie, Polanco, Carlos A., Le, Nam Q., Ghosh, Avik W., and Norris, Pamela M.. 2019.
"Maximization of thermal conductance at interfaces via exponentially massgraded interlayers". United States.
doi:10.1039/C8NR09188A.
@article{osti_1502588,
title = {Maximization of thermal conductance at interfaces via exponentially massgraded interlayers},
author = {Rastgarkafshgarkolaei, Rouzbeh and Zhang, Jingjie and Polanco, Carlos A. and Le, Nam Q. and Ghosh, Avik W. and Norris, Pamela M.},
abstractNote = {Here, we propose a strategy to potentially best enhance interfacial thermal transport through solid–solid interfaces by adding nanoengineered, exponentially massgraded intermediate layers. This exponential design rule results in a greater enhancement than a linearly massgraded interface. By combining calculations using nonequilibrium Green's functions (NEGF) and nonequilibrium molecular dynamics (NEMD), we investigated the role of impedance matching and anharmonicity in the enhancement in addition to geometric parameters such as the number of layers and the junction thickness. Our analysis shows that the effect on thermal conductance is dominated by the phonon thermalization through anharmonic effects, while elastic phonon transmission and impedance matching play a secondary role. In the harmonic limit, increasing the number of layers results in greater elastic phonon transmission at each individual boundary, countered by the decrease of available conducting channels. Consequently, conductance initially increases with number of layers due to improved bridging, but quickly saturates. The presence of slight anharmonic effects (at very low temperature, T = 2 K) turns the saturation into a monotonically increasing trend. Anharmonic effects can further facilitate interfacial thermal transport through the thermalization of phonons at moderate temperatures. At high temperature, however, the role of anharmonicity as a facilitator of interfacial thermal transport reverses. Strong anharmonicity introduces significant intrinsic resistance, overruling the enhancement in thermal conduction at the boundaries. It follows that at a particular temperature, there exists a corresponding junction thickness at which thermal conductance is maximized.},
doi = {10.1039/C8NR09188A},
journal = {Nanoscale},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {2}
}
Works referenced in this record:
Nanoscale thermal transport
journal, January 2003
journal, January 2003
 Cahill, David G.; Ford, Wayne K.; Goodson, Kenneth E.
 Journal of Applied Physics, Vol. 93, Issue 2, p. 793818