Engineering Commons^™

Forcing Cesium Into Higher Oxidation States Via Useful Hard X-Ray Induced Chemistry At Extreme Conditions, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recent theoretical work published in Nature Chemistry postulates the existence of cesium in high oxidation states when bonding with fluorine. It is thus predicted to behave as a p-block element (such as xenon) at pressures above 5 GPa. At these pressures, fluorine atoms may bond with the inner p-shell electrons forming CsFn, where n may vary from 2 up to 6; thus the oxidation state of Cs may change up to 6+. My research focused on physically synthesizing these compounds and to verify that, given the right conditions, bonding doesn't only occur with valence electrons, but with the inner p-shell …

High-Pressure Properties Of Several Narrow Bandgap Semiconductors From First-Principles Calculations, Andrew Michael Alvarado

UNLV Theses, Dissertations, Professional Papers, and Capstones

The electronic, thermodynamic, and structural properties of three semiconducting materials, ZnO, InN, and PbS, at high pressure are investigated utilizing first-principles calculations based on density function theory. The first two systems, ZnO and InN, crystalize as hexagonal structures at ambient conditions and transition to a cubic structure at higher pressures. The last system, PbS, is cubic at ambient conditions, but transitions to an orthorhombic structure at higher pressure. At ambient conditions, these materials are well known semiconductors with vast amount of research and a variety of wide ranging applications in electrical devices. However, there is a lack of understanding of …

Neutron-Gamma Discrimination In Elpasolite Scintillator Detector, Brittany Morgan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Existing nuclear stockpiles and weapons-making capabilities imperil the global community. Current nonproliferation efforts involve the research and development of newer, more efficient detection systems that can be deployed for the interdiction and monitoring of special nuclear materials (SNM). Spontaneous and induced fission events in SNM produce neutrons and gamma rays, which can be detected and analyzed, in particular, using scintillator detectors. Various electronic data acquisition systems and data analysis methods have been employed to record and characterize neutron and photon signatures. The goal of this thesis is to develop a new method of discrimination between neutrons and photons in the …

Impedance Spectroscopy Studies Of Yttria Stabilized Zirconia Under Extreme Conditions, Quinlan Blaine Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Yttria Stabilized Zirconia (YSZ) is of interest for many industries. Varying amounts of Yttria (Y2O3) can be doped into Zirconia (ZrO2) to create materials with specific characteristics. For instance, 3mol% YSZ (3YSZ) is known to be a super hard material and is used as a coating on drill tips and as an abrasive. Eight mol% YSZ (8YSZ) is commonly used as a solid electrolyte in Solid Oxide Fuel Cells because of its good ionic conducting abilities and stability at high temperatures. In this thesis project, a novel experimental setup was created and used to study the ionic conductivity of (3 …

Mcnp6 Computational-Based Sensitivity Propagation Analysis Of Continuous Neutron Cross-Sections Using The Godiva (Hmf-001) And The Godiver (Hmf-004) Benchmark Criticality Study Cases, Lawrence James Lakeotes

UNLV Theses, Dissertations, Professional Papers, and Capstones

There has been a reduction in funding for theoretical and applied research for improving the nation's database of continuous neutron cross-sections at BNL-NNDC. From 1940 through the late 1980s, research and applied development produced volumes of reliable neutron continuous cross-sections for many isotopes. Currently, the cross-section work has been mainly computational. The focus of this research is mainly centered on the requirements for improving thermal cross-sections to support reactor operations and fuel storage. The research efforts will also helpfully aid in the fast fission spectrum in order to support fast reactor designs for improving safety analysis and feedback coefficients.

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