University PhD Dissertation Defense: Thermal and Thermoelectric Transport in Carbon Based Nanomaterials, Feifei Lian, Advisor: Eric Pop

University PhD Dissertation Defense<br><br>Title:&nbsp;&nbsp;Thermal and Thermoelectric Transport in Carbon Based Nanomaterials <br>Speaker:&nbsp;Feifei Lian, Advisor: Eric Pop<br>Date: December 11, 2017<br>Time: 2:00pm<br>Location: Clark Center S360<br><br>Abstract:&nbsp;<br>Thermoelectric energy harvesting was first used by NASA in 1961, but has been too inefficient and expensive for widespread application on Earth. Due to the interdependent nature of thermal and electrical conductivity, and Seebeck coefficient, it is crucial to understand these transport mechanisms in nanomaterials to design better thermoelectrics for low grade (&lt; 100&nbsp;oC) waste heat harvesting. My PhD research has focused on developing accurate metrologies to unravel the physics of thermal and thermoelectric transport in carbon-based nanomaterials.<br> <p>First, I will describe the design and construction of a bulk thermal and thermoelectric measurement tool that can be used to rapidly characterize cross-plane thermal conductivity and Seebeck voltage of macroscale materials. Next, I will talk about an infrared microscopy-based technique that is designed to measure the in-plane thermal conductivity of ~400 nm thick suspended films. I utilize this method to characterize thermal transport in chirality-sorted single-walled carbon nanotube (SWNT) networks. These networks display high thermal conductivities comparable to the best metals, despite having order-of-magnitude lower mass densities.</p> <p>In the final part of my talk, I will discuss the design and fabrication of an on-chip thermometry platform used to measure thermoelectric transport in sub-10 nm thick films. I present a comprehensive study of the effect of temperature and doping (both n- and p-type) on the thermoelectric transport in ultra-pure (&gt; 99.9 %) semiconducting SWNT (s-SWNT) networks. I demonstrate the highest electron and hole Seebeck coefficients for polymer-free s-SWNT networks, over the 80 to 600 K temperature range. To understand these results, I develop a compact theoretical model that uncovers the fundamental physics of carrier transport between CNTs, and evaluates the relative contributions of 1D tubes versus 0D CNT-junctions to the thermoelectric properties of the network.</p>

Date: 
Monday, December 11, 2017 - 2:00pm to 3:00pm
location: 
James H. Clark Center, 318 Campus Drive, Stanford, CA 94305, USA