Engineering Commons^™

Ion Irradiation-Induced Microstructural Change In Sic, Chien-Hung Chen

Doctoral Dissertations

The high temperature radiation resistance of nuclear materials has become a key issue in developing future nuclear reactors. Because of its mechanical stability under high-energy neutron irradiation and high temperature, silicon carbide (SiC) has great potential as a structural material in advanced nuclear energy systems.

A newly developed nano-engineered (NE) 3C SiC with a nano-layered stacking fault (SFs) structure has been recently considered as a prospective choice due to enhanced point defect annihilation between layer-type structures, leading to outstanding radiation durability.

The objective of this project was to advance the understanding of gas bubble formation mechanisms under irradiation conditions in …

Ion Irradiation Induced Damage And Dynamic Recovery In Single Crystal Silicon Carbide And Strontium Titanate, Haizhou Xue

Doctoral Dissertations

The objective of this thesis work is to gain better understanding of ion-solid interaction in the energy regime where electronic and nuclear energy loss are comparable. Such responses of materials to ion irradiations are of fundamental importance for micro-electronics and nuclear applications. The ion irradiation induced modification for the crystal structure, the physical and chemical properties etc. may strongly affect the performance of functional materials that needs to be better understood.

Experimentally, ion irradiation induced damage accumulation and dynamic recovery in SiC [silicon carbide] and SrTiO₃ [strontium titanate] were studied in this dissertation project. Five chapters are presented: Firstly, …

Crystal Growth And Physical Property Characterization Of Complex Perovskite Oxides, Ling Li

Doctoral Dissertations

Bulk EuTiO₃ [europium titanate], a quantum paraelectric antiferromagnet, is shown to exhibit multiferroic behavior in strained thin film form, which highlights the spin-phonon coupling in this system. We have investigated the structural, elastic, magnetic, thermal and transport properties of single crystals of EuTiO₃ as well as doped system EuTi_1-xB_xO₃ (B = Zr, Nb) [Zr and Nb doped europium titanate] utilizing various experimental techniques and theoretical calculations.

The cubic to tetragonal structural transition in pure EuTiO₃ is characterized by a pronounced step-like softening of the elastic moduli near 288 K [kelvin], which resembles …

Development And Improvement Of Cerium Activated Gadolinium Gallium Aluminum Garnets Scintillators For Radiation Detectors By Codoping, Fang Meng

Doctoral Dissertations

Ce doped Gd3Ga3Al2O12 [gadolinium gallium aluminium oxides] is considered as a promising candidate for the next generation Positron Emission Tomography material due to its high light yield in theory. This dissertation is focused on studying the Gd3Ga3Al2O12:Ce crystals by codoping, aiming to improve the light yield and decay time experimentally and understand the underlying mechanism.

The work starts from prescreening appropriate codopants for Gd3Ga3Al2O12:Ce crystals. A cost-effective method is developed to predict the performance of the single crystals by characterizing the radioluminescence intensity and photoluminescence decay of the small polycrystalline pellets. This method is demonstrated by showing that the results …

Electronic Energy Loss Of Heavy Ions And Its Effects In Ceramics, Ke Jin

Doctoral Dissertations

Energy loss of medium energy heavy ions (i.e. Cl, Br, I, and Au) in thin compound foils containing light elements (i.e. silicon carbide and silicon dioxide) is directly measured using a time-of-flight elastic recoil detection analysis (ToF-ERDA) technique. An improved data analysis procedure is proposed to provide the experimentally determined electronic stopping powers. This analysis procedure requires reliable predictions of nuclear stopping. Thus, the nuclear stopping predicted by the Stopping and Range of Ions in Matter (SRIM) code is validated by measuring the angular distribution of 1 MeV Au ions after penetrating a thin silicon nitride foil, using a secondary …