Study of the thermal conductivity of a metal-coated multi-walled carbon nanotube using molecular dynamics atomistic simu
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2018.676
Study of the thermal conductivity of a metal-coated multi-walled carbon nanotube using molecular dynamics atomistic simulations Dinesh Bommidi1, Ravindra Sunil Dhumal2, Iman Salehinia2 1
2
Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627
Department of Mechanical Engineering, Northern Illinois University, DeKalb, IL 60115
ABSTRACT
Thermal conductivity of a nickel-coated tri-wall carbon nanotube was studied using molecular dynamics where both the phonon and electron contributions were considered. Simulations predicted a significant effect of the metal coating on the thermal conductivity, i.e. 50% decrease for 1.2 nm of Ni coating. However, the decreasing rate of the thermal conductivity is minuscule for the metal thicker than 1.6 nm. The smaller thermal conductivity of the metal coating, phonon scattering at the interface, and less impacted heat transfer on the inner tubes of the carbon nanotube rationalized the observed trends.
INTRODUCTION Dimensions of next generation electronic equipment are slimming down at a great rate towards microscale as well as nanoscale. Employing thermal interface materials (TIMs) between the heat generating devices and the heat sinks helps the effective heat removal from the equipment that is essential for the stable performance of the system. Hence, research is focused to develop new materials that have a high thermal conductivity together with good mechanical compliance so that they can be easily shaped, filled, or fitted into complex geometries [1]. Carbon nanotube (CNT) arrays (turfs) (see figure. 1a) are prominent contenders as they possess incredible attributes such as but not limited to- low weight to strength ratio, high flexibility, and high thermal conductivity when compared to most of the metals or metal-based alloys [2,3]. Isolated and individual CNTs were originally predicted to have superlative thermal transport properties, and these predictions have
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been validated experimentally [4]. However, CNT arrays have never approached the thermal properties of isolated CNTs. This poor performance has been tied to defects, misaligned axial contacts between CNTs in the CNT array, and interfacial resistance between CNTs and substrate [5,6].
Figure 1 (a) CNT array (turf) having intertwined tubes shown as an inset (adapted from [7]), (b) Uniform coating of Nickel over CNTs in a turf. The inset shows the non-uniform Ni coating on CNTs due to higher electrodeposition voltage (adapted from [8]).
The application of metal coatings on each CNT in a CNT array results in the fabrication of a foam that consists of coaxial CNT and metal coating ligaments with pores between the ligaments (see figure 1b) [8,9]. This material provides low dens
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