Modeling and characterization of thermoelectric properties of SiGe nanocomposites

Direct energy conversion between thermal and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency is related to the thermoelectric figure of merit ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the large scale applications of this technology. Recently, however, significant enhancements in ZT were reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to the studies on heat transfer mechanisms in nanostructures, the reduced thermal conductivity of nanostructures is mainly attributed to the increased scattering of phonons at interfaces. Based on this idea, nanocomposites are also expected to have a lower thermal conductivity than their bulk counterparts of the same chemical configuration. Nanocomposites are materials with constituents of less than 100 nm in size. They can be fabricated with a low cost just by mixing nano sized particles followed by consolidation of nano sized powders. In this thesis, SiGe nanocomposites are investigated for power generation at high temperature. The material properties are characterized at different temperatures, and the optimized process conditions are explored experimentally. In addition, theoretical studies are carried out for better understanding of transport phenomena and our experimental results.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Lee, Hohyun, 1978-

Advisor dc:contributor.advisor

• Gang Chen.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/50589

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/50589