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Synthesis and characterization of micro/nano material for thermoelectric applications

Iyengar, Ananth Shalvapulle
http://rave.ohiolink.edu/etdc/view?acc_num=case1276182370

Abstract Details

2010, Doctor of Philosophy, Case Western Reserve University, EMC - Mechanical Engineering.
Various micro- and nanomaterials are explored to assess their potential for enhancing figure of merit (ZT) of the material. Free standing bismuth nanowires are synthesized by vapor deposition technique. Bismuth nanowires and commercial bismuth microparticles were uni-axially compressed into respective pellets. The anisotropy due to the compression process is investigated by measuring the directional thermal and electrical conductivities of the pellets. Thermal conductivity is measured by mirage technique, and dynamic plane source method. Electrical conductivity is measured by 4point probe in inline and over-under configurations. Seebeck coefficient is measured by the steady-state DC technique. The anisotropy is attributed to effects including, the particle interface, porosity, and the oxide layer on the particles. Quantum confinement effect is exhibited by the 20nm nanowire pellet. The ZT of the compressed nanowire pellets are one order of magnitude lower and the compressed microparticle pellets showed about half of the bulk bismuth ZT. These low ZT values are due to the various factors including dielectric surface oxide layer, pellet porosity, and particle interfaces. Among these factors, surface oxide layer plays the major role in reducing the electrical conductivity of the pellets. Another ongoing project is an investigation into the thermoelectric properties of electrolyte solutions to assess their viability as liquid thermoelectric materials. A steady-state thermal conductivity measuring setup for liquids was developed to measure its properties. The setup consists of a pair of coaxial cylinders with test fluid placed in the annular space between these cylinders with water tight cover plates at the top and bottom of the cylinders. Heat flow from the coil at the concentric-center of the inner cylinder raises the temperature of the assembly. Thermal conductivity is calculated by comparing the steady-state radial heat flow between the cylinders and the test fluid (comparative method). Thermal conductivity of water, glycerol, and ethylene glycol was measured for varying temperatures and is in good agreement with the published thermal conductivity values in literature.
Alexis Abramson (Advisor)
Iwan Alexander (Committee Member)
Joseph Prahl (Committee Member)
Christian Zorman (Committee Member)
168 p.
Mechanical Engineering
Compression; Nanowire; Bismuth; Anisotropy; quantum confinement; and Figure of merit

Recommended Citations

Citations

  • Iyengar, A. S. (2010). Synthesis and characterization of micro/nano material for thermoelectric applications [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1276182370

    APA Style (7th edition)

  • Iyengar, Ananth. Synthesis and characterization of micro/nano material for thermoelectric applications. 2010. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1276182370.

    MLA Style (8th edition)

  • Iyengar, Ananth. "Synthesis and characterization of micro/nano material for thermoelectric applications." Doctoral dissertation, Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1276182370

    Chicago Manual of Style (17th edition)

case1276182370
996
© 2010, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.