Title :

Structural Metrics for High-Performance Thermoelectrics: From Bulk to Nano

Speaker :

Dr. Baoling Huang

Postdoctoral Research Fellow, Lawrence Berkeley National Laboratory

University of California, Berkeley, USA

Venue :

Room 215, William M. W. Mong Engineering Building, CUHK

Date :

Mar 24, 2010, Wednesday
11:30 AM - 12:30 PM

Abstract :

Efficient solid-state energy conversion based on the thermoelectric (TE) effects, i.e., the Peltier effect for cooling and the Seebeck effect for power generation, has great potentials in many applications, such as waste heat recovery and cooling for electronic components. The applications of thermoelectrics are currently limited by their low efficiency. A-high performance TE material requires a high Seebeck coefficient S, a high electrical conductivity se and a low thermal conductivity k, and its TE quality is described by the figure of merit ZT (=S2seT/k). Great efforts have been made on maximizing ZT in recent decades; however, this task has been proved to be very challenging because of the strong interdependence of the physical parameters. The fundamental understanding of the energy and charge transport mechanism in TE materials and their relationship with the atomic structure will help the search and design of high-performance thermoelectrics.

Thermal energy and charge transport in both bulk and nanostructured TE materials have been explored. A comprehensive, multi-scale approach that can predict the key TE transport coefficients (S, se, and k) has been developed by combining first-principles calculations based on density functional theory (DFT), molecular dynamics (MD) simulations, and Boltzmann transport equations (BTE). This approach also allows for the investigation of composition variations, site substitutions, and rattler insertion, etc. It has been successfully applied in the investigation for bulk high-performance thermoelectrics with microstructures, such as layered Bi2Te3. On the other side, due to the large difference in mean free path between phonons and electrons in some materials, adopting low-dimensional structures may suppress phonon transport without affecting electron transport. To understand the thermal transport in low-dimensional structures, we have batch-fabricated a suspended microdevice with integrated silicon nanowires. These nanowires are free of defects and the contact resistance has been eliminated. Key nanowire variables, such as width, thickness and lengths, can be precisely controlled. Phonon transport in silicon nanowires is also systematically and experimentally investigated.

Biography :

Dr. Baoling Huang received his B.S. and M.S. degrees in Engineering Thermophysics from the Department of Engineering Mechanics at Tsinghua University, Beijing in 1999 and 2001, respectively. From 2001 to 2003, he worked as a senior engineer in industry. In 2008, he received a Ph.D. degree in Mechanical Engineering from the University of Michigan, Ann Arbor, for research conducted in the Heat Transfer Physics Lab supervised by Professor Massoud Kaviany. After graduation, he joined the Nano-Energy Lab supervised by Professor Arun Majumdar at the University of California, Berkeley and worked as a postdoctoral research fellow in Lawrence Berkeley National Laboratory. Dr. Baoling Huang has research experience on both theoretical modeling/simulation and experimental fabrication/measurements. His research mainly focuses on developing the fundamental understanding of energy/charge transport and conversion in novel thermoelectric materials and the applications in thermal-electrical energy conversion and thermal management. His research interests are in the broad area of energy transport, conversion and storage. Of particular interest are phonon dynamics and transport in low-dimensional structures and nanocomposites, novel devices for thermoelectric energy conversion, and nano-engineered supercapacitor and battery for energy storage.

    **************************************** ALL ARE WELCOME ****************************************

Enquiries: Ms. Winnie Wong or Prof. Wen J. Li, Department of Mechanical and Automation Engineering, CUHK at 2609 8337. *MAE Series (2009-10) is contained in the World-Wide Web home page at http://www3.mae.cuhk.edu.hk/maeseminars.php#mae