Investigations of One Dimensional Heat Transport
Date Issued
2015
Date
2015
Author(s)
Wu, Chi-Hsun
Abstract
To investigate the mechanism of phonon in thermal transport, recently, many researches have studied1, both experimentally and theoretically, on heat conduction in low dimensional systems, but due to the difficulties of synthesis of long-length nanomaterial and the decay of signal with the length, the experiments on length dependence of heat conduction by phonons are still few. After the improvement on the synthesis of carbon nanotube (CNT), single wall carbon nanotube (SWCNT) with length about half meter can be produced by flow guided chemical vapor deposition9. Besides, the highly sensitive double frequency ( 2 ω ) method we invented10 made the experiment of heat conduction in quasi-one dimensional system possible. In this thesis, we investigated the length dependence of thermal conductivity and proposed a new method to measure the asymmetric phenomena on heat conduction. In the second chapter of the thesis, the properties and synthesis of CNT will be introduced, followed by the sample preparation and experimental principle. In chapter three, we measured the thermal conductivity of CNTs with different length (2μm~1mm), and verified that the thermal conductivity diverges with increasing length. This phenomenon violates the Fourier’s law, which may help us understand thermal transport theory better. We also check our result carefully in many aspects, including the discussion on radiation heat dissipation, contact resistance, the frequency dependence of electric signals, to ensure the validity of experimental results. In the fourth chapter, we proposed a 4ω method for detecting asymmetric heat conduction, which can theoretically improve traditional method significantly. The details of this method are discussed, and the experimental results are provided. Although there are some mysteries need to be understood, we believe that this method is promising for bringing new findings on asymmetric heat conduction.
Subjects
phonon
carbon nanotube
heat conduction
thermal conductivity
Fourier’s law
chemical vapor deposition
anomalous heat conduction
Type
thesis
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