Engineering Commons^™

Low Energy Recoil Simulations In Mgo, Linbo3, And Litao3 Using Ab Initio Molecular Dynamics, Benjamin Aaron Petersen

Doctoral Dissertations

Ab initio molecular dynamics (AIMD) was utilized to test a series of materials, MgO, LiNbO₃ , and LiTaO₃ , to determine defect structures produced due to low energy recoil events . The kinetic energy required to displace an atom from its lattice site, the threshold displacement energy, was calculated for an array of directions in each material, based on symmetry and complexity of the structure. MgO having a simple rock salt structure provided a model material for demonstrating computational techniques used later on LiTaO₃ and LiNbO₃ . The minimum values for displacing an atom were at …

Helium Diffusion And Accumulation In Gd2ti2o7 And Gd2zr2o7, Caitlin Anne Taylor

Doctoral Dissertations

The effects of helium accumulation on bubble formation and mechanical properties, as well as the fundamentals of helium diffusion in pyrochlores, are experimentally investigated in Gd₂Ti₂O₇ [gadolinium titanate] and Gd₂Zr₂O₇ [gadolinium zirconate]. We find that helium accumulation results in bubble formation at concentrations of 6 at.% in pre-damaged Gd₂Ti₂O₇ and 4.6 at.% in pre-damaged Gd₂Zr₂O₇. Lattice parameter, residual stress, and hardness changes due to helium accumulation were investigated in Gd₂Zr₂O₇, which remains crystalline …

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, …