Events

Abstract

High-thermal conductivity materials are essential for applications ranging from thermal management of microelectronics to electrification of industrial heating processes. Wide-bandgap diamond and semi-metallic graphite achieve record-high thermal conductivity because strong covalent bonding of light carbon atoms gives rise to a large thermal conductivity contribution from phonons, the energy quanta of lattice vibrations. It remains an outstanding question whether the reduced dimensionality of graphene and carbon nanotubes can increase their thermal conductivity beyond the graphite or diamond values. Meanwhile, theoretical studies have suggested the possibility of achieving a unusual high lattice thermal conductivity in some compounds made of both light and heavy elements due to a large energy gap in the phonon dispersion. This seminar will report recent advances in electro-thermal microbridge measurements of both lattice and electronic thermal transport in low-dimensional graphene and nanotube samples. It will also discuss thermal transport measurements of bulk crystals of semiconducting cubic boron arsenide (BAs) and semi-metallic theta-phase tantalum nitride (q-TaN) for the establishment of a phonon band engineering paradigm of high-thermal conductivity compounds. These discoveries have motivated heterogeneous integration of BAs with other semiconductors for enhanced thermal and electronic performance, and the manufacturing of high-temperature heating elements and ceramic heat exchangers based on q-TaN.

About the speaker

Li Shi holds the Ernest Cockrell, Sr. Chair in Engineering #2 at the University of Texas (UT) at Austin. He received his doctoral, master, and bachelor degrees from University of California at Berkeley, Arizona State University, and Tsinghua University, respectively. He had industrial research experiences in IBM Research and an electrical power research institute before joining UT as an assistant professor in 2002. He served as the Editor in Chief for Nanoscale and Microscale Thermophysical Engineering between 2013 and 2021. His scholarly contributions and professional services have been recognized by the Touloukian Award in Thermophysical Properties, the Heat Transfer Memorial Award in Science, and the O’Donnell Award in Engineering.