(7月18日9:30)Phonon Dynamics at Surfaces and Interfaces and Its Engineering Implications
报告题目： Phonon Dynamics at Surfaces and Interfaces and Its Engineering Implications
报告人: Prof. Deyu Li（李德玉）
Department of Mechanical Engineering
Nanoscale thermal transport has attracted significant attention over the past two decades because of both fundamental scientific interest and important engineering applications. For semiconductors and insulators, phonons are the dominant energy carriers and interactions between phonons and surfaces/interfaces play a key role in energy transport. From studying thermal transport through various individual nanostructures and their contacts, we have obtained several new insights into the phonon dynamics at surfaces and interfaces, which could have important implications in engineering the effective properties of nanostructured materials. Through measuring the thermal conductivity of silicon nanowires and nanoribbons, we show that when the surface-area-to-volume ratio reaches a critical value, size effects beyond phonon-boundary scattering becomes important. Further, studies on kinked boron carbide nanowires disclose how phonons transmit through a nanoscale kink, which provides new opportunities for tuning materials’ thermal conductivity. Examination of the contact thermal conductance between two individual multi-walled carbon nanotubes reveal an interesting diameter dependence, which involves intriguing underlying physics. Finally, comparison of the thermal conductivity of single and double boron nanoribbons suggests that there are two separate specularity parameters at interfaces for transmitted and reflected phonons, respectively. These new understandings could lead to novel materials design for desired effective thermal properties.
Dr. Deyu Li is currently a full professor in the Mechanical Engineering department at Vanderbilt University. He received his B.S., M.S., and Ph.D. degrees from the University of Science and Technology of China, Tsinghua University, and the University of California, Berkeley, respectively. Professor Li’s research interest includes nanoscale energy transport as well as microfluidics and nanofluidics. He has co-authored over 70 journal papers, which have been cited more than 7700 times according to Google Scholar. Dr. Li received an NSF career award in 2007, and the Vanderbilt Chancellor’s Award for Research in 2013.