Thermal rectification in mass-graded nanotubes: a model approach in the framework of reverse non-equilibrium molecular dynamics simulations

Abstract

The thermal rectification in nanotubes with a mass gradient is studied by reverse non-equilibrium molecular dynamics simulations. We predict a preferred heat flow from light to heavy atoms which differs from the preferential direction in one-dimensional monoatomic systems. This behavior of nanotubes is explained by anharmonicities caused by transverse motions which are stronger at the low-mass end. The present simulations show an enhanced rectification with increasing tube length, diameter and mass gradient. Implications of the present findings for applied topics are mentioned concisely.

A review of thermal rectification observations and models in solid materials

“…The non-equilibrium molecular dynamics simulations showed that transport was greater in the direction of low-mass to high-mass with an effective rectification between 0.015 and 0.074 depending on temperature and the mass gradient. In 2010 Alaghemandi et al performed additional non-equilibrium simulations of non-uniform mass distributed carbon nanotubes and found the same result as their previous work [44]. In this work they found that the addition of anharmonic effects perpendicular to the longitudinal phonon modes acted to increase the contribution of the longitudinal modes to the vibrational energy and transport which does not occur in symmetric systems of the 1D systems that will be discussed in §2.2.4.…”

“…to think about what devices can be fabricated, what quantities can be measured and whether the theoretical [15] Al/SS thermal warping 0.67 Rogers [17] Al/SS thermal potential barrier 0.1 Powell et al [19] Al/SS thermal warping 0 Clausing [20] SS/Al thermal strain 0.2 Lewis and Perkins [21] Al/SS thermal warping 0.41 O'Callaghan et al [27] varied thermal warping 0.13 Stevenson et al [23] varied thermal warping 0.21 Chang et al [5] CNT and BNNT non-uniform mass loading 0.034 Kobayashi et al [38] varied bulk thermal conductivity 0.18 [4] 1D chain nonlinear lattice 0.33 Li et al [81] 1D chain nonlinear lattice 0.98 Hu et al [82] 1D chain nonlinear lattice 1.0 Lan et al [75] 1D chain nonlinear lattice 1.0 Hopkins and Serrano [88] 1D chain asymmetric mass loading and defect 0.29 Yang et al [48] graphene asymmetric ribbons 0.6 Hu et al [49,55] graphene asymmetric ribbons 0.47 Alaghemandi et al [42,44] CNT non-uniform mass loading 0.17 Hu et al [79] water/silica interface transmission 0.21 Roberts and Walker [74] argon/krypton interface transmission 0.13 Wu and Li [46] CNH asymmetric CNT 0.55 Yang et al [47] CNC asymmetric CNT 0.46 Wu and Li [56] CNT CNT interface 0.39 systems can be realized in the lab. In fact, experimental study of thermal rectification is said to be ongoing in quite a few research labs.…”

“…Unfortunately in many of these reports the mechanism that causes thermal rectification does so by reducing the transport (in one direction more than the other), which can make it difficult to maintain high levels of conduction. In some of these studies, specifically the work with the asymmetric CNTs and graphene [5,56,47,46,49,55,42,44,48], the transport appears to be increased in one direction and decreased in the opposite which makes these ideal materials for thermal rectification applications.…”

Detecting thermal rectification

“…[14][15][16][17][18][19][20] Many theoretical works based on engineering real materials have been proposed to reach higher R's. [21][22][23][24][25][26][27][28][29][30][31][32] Recently, the concept of thermal rectification has been extended to acoustic systems and radiation heat transfer. 33,34 During the past decade, R∼1.07 in a pure phononic system was observed in BN nanotubes.…”

Thermal rectification in asymmetric U-shaped graphene flakes

“…Since J + = −J − , A and L are the same, so the thermal rectification ratio η is qualified as [9,[20][21][22]:…”