Doctor of Philosophy, The Ohio State University, 2020, 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 th (open full item for complete abstract)

Committee: Marat Khafizov Prof. (Advisor); Igor Adamovich Prof. (Committee Member); Sandip Mazumder Prof. (Committee Member); David Hurley Dr. (Committee Member) Subjects: Condensed Matter Physics; Materials Science; Mechanical Engineering; Nanoscience; Nuclear Engineering; Nuclear Physics