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Impact of Nanoscale Defects on Thermal Transport in Materials

Chauhan, Vinay Singh
http://rave.ohiolink.edu/etdc/view?acc_num=osu1586440154974469

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
Thermal management is critical for both nuclear and electronics industry because of heat generation during the operation. Major part of energy consumed in microelectronic devices and nuclear reactors dissipates as heat, and sometimes also creates hot spots. This is critical and precarious for the nuclear applications, while for the electronics, it has detrimental effects on the device performance and affects the reliability of devices. The microelectronic devices and nuclear materials are exposed to the extreme environments such as irradiation, vacuum, and molten salts etc. In addition to the already existing intrinsic defects, this exposure leads to the creation of multiple defects inside the materials. The goal of this research is to understand the phonon transport physics at these small length scales due to intrinsic and extrinsic defects in the material. Primarily, three different materials are discussed in this report. SiC and sapphire have been chosen for their applications in both microelectronic devices and nuclear industry while ceria has been studied as a surrogate material for the nuclear fuels (UO2 and ThO2). There are different kinds of defects created inside the material when exposed to irradiation. The complex interaction of phonons with these defects dictates the resultant thermal transport however, it is difficult to apportion the impact of a particular type of defect. The approach used here employs materials induced with only a few types of defects at a time in order to isolate and study the impact of induced defect on thermal transport. Consequently, irradiation has been used in this study to induce desired defects inside the material and thereafter study their effect on thermal conductivity. Interstitials and vacancies, collectively known as point defects are formed under low dose and heavy ion irradiation regime. Here, SiC is irradiated using Kr ions to study impact of point defects on its vibrational and thermal properties. While the ceria is irradiated at high temperature by protons of multiple energies to form dislocation loops and point defects. Multiple characterization techniques are used such as XRD, Raman spectroscopy, and optical ellipsometry for the quantification and impact of defects on thermal and optical properties of ceria. Lastly, sapphire is patterned with cylindrical nanochannels using Xe ions to enable the studies related to the nanoscale thermal transport. The major contributions of this work lie in better understanding of phonon interactions with the different defects, thereby improving the overall understanding of nanoscale thermal transport. It has been demonstrated that heat transfer in sapphire can be guided in a preferential direction by patterning the material with nanochannels. This can be helpful in developing thermally functional materials where heat transfer can be directed on need basis. This study also correlates results of different well-established characterization techniques to predict the heat transfer in materials with defects. This could be advantageous in future where a single characterization technique can provide multiple insights about the thermal properties of the material.
Marat Khafizov, Prof. (Advisor)
Igor Adamovich, Prof. (Committee Member)
Sandip Mazumder, Prof. (Committee Member)
David Hurley, Dr. (Committee Member)
258 p.
Condensed Matter Physics; Materials Science; Mechanical Engineering; Nanoscience; Nuclear Engineering; Nuclear Physics
thermal conductivity; nanoscale thermal transport; phonons; phonon scattering; thin films; thermoreflectance; irradiation; crystallographic defects; radiation damage; interface defects; microstructure characterization

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Citations

  • Chauhan, V. S. (2020). Impact of Nanoscale Defects on Thermal Transport in Materials [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586440154974469

    APA Style (7th edition)

  • Chauhan, Vinay. Impact of Nanoscale Defects on Thermal Transport in Materials. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1586440154974469.

    MLA Style (8th edition)

  • Chauhan, Vinay. "Impact of Nanoscale Defects on Thermal Transport in Materials." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586440154974469

    Chicago Manual of Style (17th edition)

osu1586440154974469
416
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