Publication Date

2019

Document Type

Dissertation/Thesis

First Advisor

Salehinia, Iman

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Mechanical Engineering

Abstract

Breakthroughs in nanotechnology have made it possible for the size of electronic gadgets to be scaled down to micro/nano level. What follows however, is the side effect of high power densities and overheating as the heat dissipation is restricted to very small surface area. Thus, the need of an effective thermal management system is central to these developments. One way to counter this problem is to use Thermal Interface Materials (TIMs) which promote heat transfer between heat source and sink.

Owing to their high thermal conductivity (up to 6000 W/mK), Carbon Nanotubes (CNTs) are thought of as strong candidates for TIMs. Unfortunately, they do not behave as expected when employed as Vertically Aligned CNT arrays, called as turfs. Possible causes include but are not restricted to bent/deformed CNTs, presence of impurities, defects, tube-tube contact resistance, and radiative heat losses to surroundings. Since the reduction in thermal conductivity of CNTs due to vacancies can be attributed to scattering of phonons at the site of the vacancies, we hypothesize that coating the defective CNTs with metallic layers will alleviate this reduction by providing additional pathways for heat transfer. Additionally, the metallic coatings will help decrease the contact resistance between co-axial tubes, protect the CNTs from surroundings to reduce radiative heat losses, and provide an added stiffness to CNTs, restricting their deformation. The current study focuses on employing Molecular Dynamics (MD) simulations to study the effect of vacancy concentration(s) on the thermal conductivity of metal-coated tri-walled CNTs (3WCNT).

It should be noted that the metal’s major contribution to heat transfer is by the virtue of its electrons, which the classical MD simulations are unable to capture. We therefore employ Two-Temperature Model (TTM), which can take into consideration the effect of electron-phonon interactions. Due to its ability to form uniform coatings around CNTs, Nickel has been chosen as the prime candidate for metal in this study.

Extent

65 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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