Mechanical & Materials Engineering, Department of
First Advisor
Mohammad Ghashami
Committee Members
Nitesh Nama, Natale Ianno
Date of this Version
8-2024
Document Type
Article
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Mechanical Engineering and Applied Mechanics
Under the supervision of Professor Mohammad Ghashami
Lincoln, Nebraska, August 2024
Abstract
This work investigates the mechanisms to manipulate and control the magnitudes of Near-Field Radiative Heat Transfer (NFRHT) using two-dimensional materials and nanostructured surfaces. NFRHT occurs when the geometrical features of the radiating objects or the separation distance between interacting bodies are comparable to or lower than the characteristic thermal radiation wavelength. NFRHT magnitudes surpass the blackbody limit by several orders of magnitude due to phenomena such as photon tunneling and new modes of energy transfer, like surface polaritons. Therefore, it is crucial to understand how material properties and surface nanostructures affect NFRHT.
The first part of this work examines the radiative thermal transport between Titanium Carbide MXene surfaces. Samples with varying thicknesses of Titanium Carbide MXene were fabricated using a layer-by-layer spin-coating technique on quartz substrates. Spectroscopic ellipsometry, conducted over a broad spectral range (mid-IR to vacuum ultraviolet), revealed a strong correlation between radiative properties and MXene layer thickness. Further calculations of the spectral and total radiative heat flux between these samples in the near-field regime demonstrated the superior role MXenes can play in controlling radiative heat transfer.
The second part of this study investigates the near-field radiative response of Cobalt-slanted columnar thin films (Co-SCTF) fabricated using glancing angle deposition. Generalized ellipsometry was used to determine the geometric structure and anisotropic dielectric properties of the nanostructured thin films over the near-IR to mid-IR range. The extracted anisotropic complex dielectric function was used to calculate the NFRHT between the samples. The numerical results show a periodic trend in the magnitudes of NFRHT over an in-plane rotation of the Co-SCTF, with the periodicity varying as the gap distance decreases, allowing better interaction of localized modes from the nanostructures. The NFRHT trend over the gap distance exhibited similar behavior and higher magnitudes than dielectric materials.
Advisor: Mohammad Ghashami
Comments
Copyright 2024, Sean Luke Murray. Used by permission