In the ongoing struggle to resolve our current energy crisis, many agencies and researchers have spearheaded the application of direct energy conversion materials, such as thermoelectric and thermionic devices for waste heat recovery and power generation. However, the current state-of-the-art direct energy conversion materials are plagued by extremely low efficiencies that prevent a widespread solution. Recent effort to improve the efficiencies of these direct energy conversion materials has demonstrated a drastic increase through the inclusion of nanoscale features. With new advances in nanoscale materials comes the need for new models that can capture the underlying physics. Thus, this research has developed a necessary tool and a unique modeling approach (based on NEGF quantum simulations) that couples both the electrical and thermal response of nanoscale transport accounting for both the dissipative interactions of electron-phonon and phonon-phonon scattering. Through the aid of high performance computing techniques, the models developed in this research are able to explore the large design space of nano-structured thermoelectrics and thermionic materials. The models allow computational predictions to drive innovation for new, optimized, direct energy conversion materials.
A specific device innovation that has come from this research is the development of variably spaced superlattice (VSSL) devices, which are the next progression in band engineering thermoelectric materials. Computational findings of VSSL materials predict a seven times increase in ZT at room temperature when compared to traditional superlattice devices. Other thermoelectric materials studied include nanocrystalline composites (NCC) which were predicted to outperform equivalent superlattice structures as a results of decreases electron filtering. In addition to thermoelectric materials, this research has developed a quantum modeling technique to investigate and optimize nano-tipped thermionic and thermal-field devices. Results have provided incite into the applicability of Richardson's theory in characterizing the emission from wide-band gap thermionic materials. Ultimately, the quantum models developed in this research are a necessary tool for understanding nanoscale transport and innovating new nanostructured materials.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-03262012-225805 |
| Date | 10 April 2012 |
| Creators | Musho, Terence David |
| Contributors | Alvin Strauss, Kalman Varga, Norman Tolk, Ron Schrimpf, D. Greg Walker |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu//available/etd-03262012-225805/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0016 seconds