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Carbon Nanotubes and Molybdenum Disulfide Protected Electrodes for High Performance Lithium-Sulfur Battery Applications

Description: Lithium-sulfur (Li-S) batteries are faced with practical drawbacks of poor cycle life and low charge efficiency which hinder their advancements. Those drawbacks are primarily caused by the intrinsic issues of the cathodes (sulfur) and the anodes (Li metal). In attempt to resolve the issues found on the cathodes, this work discusses the method to prepare a binder-free three-dimensional carbon nanotubes-sulfur (3D CNTs-S) composite cathode by a facile and a scalable approach. Here, the 3D structu… more
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Date: August 2019
Creator: Cha, Eunho
Partner: UNT Libraries
open access

Carrier Mobility, Charge Trapping Effects on the Efficiency of Heavily Doped Organic Light-Emitting Diodes, and EU(lll) Based Red OLEDs

Description: Transient electroluminescence (EL) was used to measure the onset of emission delay in OLEDs based on transition metal, phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) and rare earth, phosphorescent Eu(hfa)3 with 4'-(p-tolyl)-2,2":6',2" terpyridine (ttrpy) doped into 4,4'-bis(carbazol-9-yl) triphenylamine (CBP), from which the carrier mobility was determined. For the Pt(ptp)2 doped CBP films in OLEDs with the structure: ITO/NPB (40nm)/mcp (10nm)/65% Pt(ptp)2:CBP (2… more
Date: August 2010
Creator: Lin, Ming-Te
Partner: UNT Libraries
open access

Characterization and Chemical Analysis of Fundamental Components for Lead Acid Batteries

Description: Although markets for alternative batteries, such as Li-ion, are growing, Pb-alloy batteries still dominate the market due to their low cost and good functionality. Even though these Pb-alloy batteries have been around since their discovery in 1859, little research involving advanced characterization techniques, such as synchrotron radiation X-ray diffraction (SR-XRD) and transmission electron diffraction (TEM) have been performed on Pb-alloys and sulfation, a failure mode in lead acid batteries… more
Date: May 2022
Creator: Wall, Michael T
Partner: UNT Libraries
open access

Characterization of Cure Kinetics and Physical Properties of a High Performance, Glass Fiber-Reinforced Epoxy Prepreg and a Novel Fluorine-Modified, Amine-Cured Commercial Epoxy.

Description: Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4'-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC) a… more
Date: December 2003
Creator: Bilyeu, Bryan
Partner: UNT Libraries
open access

Charge Interaction Effects in Epoxy with Cation Exchanged Montmorillonite Clay and Carbon Nanotubes.

Description: The influence of charge heterogeneity in nanoparticles such as montmorillonite layered silicates (MLS) and hybrid systems of MLS + carbon nanotubes was investigated in cured and uncured epoxy. Epoxy nanocomposites made with cation-exchanged montmorillonite clay were found to form agglomerates near a critical concentration. Using differential scanning calorimetry it was determined that the mixing temperature of the epoxy + MLS mixture prior to the addition of the curing agent critically influenc… more
Date: May 2005
Creator: Butzloff, Peter Robert
Partner: UNT Libraries
open access

Combinatorial Assessment of the Influence of Composition and Exposure Time on the Oxidation Behavior and Concurrent Oxygen-induced Phase Transformations of Binary Ti-x Systems

Description: The relatively low oxidation resistance and subsequent surface embrittlement have often limited the use of titanium alloys in elevated temperature structural applications. Although extensive effort is spent to investigate the high temperature oxidation performance of titanium alloys, the studies are often constrained to complex technical titanium alloys and neither the mechanisms associated with evolution of the oxide scale nor the effect of oxygen ingress on the microstructure of the base meta… more
Date: May 2015
Creator: Samimi, Peyman
Partner: UNT Libraries
open access

Computational Studies on Structures and Ionic Diffusion of Bioactive Glasses

Description: Bioactive glasses are a class of synthetic inorganic material that have wide orthopedics, dentistry, tissue engineering and other biomedical applications. The origin of the bioactivity is closely related to the atomic structures of these novel glass materials, which otherwise lack long range order and defies any direct experimental measurements due to their amorphous nature. The structure of bioactive glasses is thus essential for the understanding of bioactive behaviors and eventually rational… more
Date: August 2014
Creator: Xiang, Ye
Partner: UNT Libraries
open access

Computational Study of Dislocation Based Mechanisms in FCC Materials

Description: Understanding the relationships between microstructures and properties of materials is a key to developing new materials with more suitable qualities or employing the appropriate materials in special uses. In the present world of material research, the main focus is on microstructural control to cost-effectively enhance properties and meet performance specifications. This present work is directed towards improving the fundamental understanding of the microscale deformation mechanisms and mechan… more
Date: August 2014
Creator: Yellakara, Ranga Nikhil
Partner: UNT Libraries

Considerations in Designing Alloys for Laser-Powder Bed Fusion Additive Manufacturing

Description: This work identifies alloy terminal freezing range, columnar growth, grain coarsening, liquid availability towards the terminal stage of solidification, and segregation towards boundaries as primary factors affecting the hot-cracking susceptibility of fusion-based additive manufacturing (F-BAM) processed alloys. Additionally, an integrated computational materials engineering (ICME)-based approach has been formulated to design novel Al alloys, and high entropy alloys for F-BAM processing. The IC… more
This item is restricted from view until June 1, 2027.
Date: May 2022
Creator: Thapliyal, Saket
Partner: UNT Libraries

Corrosion Behavior of High Entropy Alloys in Molten Chloride and Molten Fluoride Salts

Description: High entropy alloys (HEAs) or complex concentrated alloys (CCAs) represent a new paradigm in structural alloy design. Molten salt corrosion behavior was studied for single-phase HEAs such as TaTiVWZr and HfTaTiVZr, and multi-phase HEAs such as AlCoCrFeNi2.1. De-alloying with porosity formation along the exposed surface and fluxing of unstable oxides were found to be primary corrosion mechanisms. Potentiodynamic polarization study was combined with systematic mass–loss study for TaTiVWZr, HfTaT… more
This item is restricted from view until June 1, 2024.
Date: May 2022
Creator: Patel, Kunjalkumar Babubhai
Partner: UNT Libraries

Crystallization and Lithium Ion Diffusion Mechanism in the Lithium-Aluminum-Germanium-Phosphate Glass-Ceramic Solid Electrolytes

Description: NASCION-type lithium-aluminum-germanium-phosphate (LAGP) glass-ceramic is one of the most promising solid electrolyte (SEs) material for the next generation Li-ion battery. Based on the crystallization of glass-ceramic material, the two-step heat treatment was designed to control the crystallization of Li-ion conducting crystal in the glass matrix. The results show that the LAGP crystal is preferred to internally crystalize, Tg + 60%∆T is the nucleation temperature that provides the highest ion… more
Date: May 2021
Creator: Kuo, Po Hsuen
Partner: UNT Libraries
open access

Defect Behaviors in Zinc Oxide and Zinc Titanates Ceramics from First Principles Computer Simulations

Description: ZnO and ZnO-TiO2 ceramics have intriguing electronic and mechanical properties and find applications in many fields. Many of these properties and applications rely on the understanding of defects and defect processes in these oxides as these defects control the electronic, catalytic and mechanical behaviors. The goal of this dissertation is to systematically study the defects and defects behaviors in Wurtzite ZnO and Ilmenite ZnTiO3 by using first principles calculations and classical simulatio… more
Date: December 2016
Creator: Sun, Wei
Partner: UNT Libraries
open access

Definition of Brittleness: Connections Between Mechanical and Tribological Properties of Polymers.

Description: The increasing use of polymer-based materials (PBMs) across all types of industry has not been matched by sufficient improvements in understanding of polymer tribology: friction, wear, and lubrication. Further, viscoelasticity of PBMs complicates characterization of their behavior. Using data from micro-scratch testing, it was determined that viscoelastic recovery (healing) in sliding wear is independent of the indenter force within a defined range of load values. Strain hardening in sliding we… more
Date: August 2008
Creator: Hagg Lobland, Haley E.
Partner: UNT Libraries
open access

Deformation Micro-mechanisms of Simple and Complex Concentrated FCC Alloys

Description: The principal objective of this work was to elucidate the effect of microstructural features on the intrinsic dislocation mechanisms in two FCC alloys. First alloy Al0.1CoCrFeNi was from a new class of material known as complex concentrated alloys, particularly high entropy alloys (HEA). The second was a conventional Al-Mg-Sc alloy in ultrafine-grained (UFG) condition. In the case of HEA, the lattice possess significant lattice strain due to the atomic size variation and cohesive energy differe… more
Date: December 2015
Creator: Komarasamy, Mageshwari
Partner: UNT Libraries
open access

Design and Manufacture of Molding Compounds for High Reliability Microelectronics in Extreme Conditions

Description: The widespread use of electronics in more avenues of consumer use is increasing. Applications range from medical instrumentation that directly can affect someone's life, down hole sensors for oil and gas, aerospace, aeronautics, and automotive electronics. The increased power density and harsh environment makes the reliability of the packaging a vital part of the reliability of the device. The increased importance of analog devices in these applications, their high voltage and high temperature … more
Date: December 2016
Creator: Garcia, Andres
Partner: UNT Libraries
open access

Design of a Polymeric Coating for Protecting Thermoelectric Materials from Sublimation and Oxidation

Description: Thermoelectric (TE) devices can undergo degradation from reactions in corrosive environments and at higher operating temperatures by sublimation and oxidation. To prevent the degradation, we have applied two high temperature polymers (HTPs) as coatings for TE materials. Sintering temperatures were from 250°C to 400°C. We explain why dip coating is better technique in our study and had two potential HTPs for tests. By applying TGA (thermogravimetric analysis), we were able to figure out which HT… more
Date: August 2019
Creator: Chen, I Kang
Partner: UNT Libraries
open access

Design Principle on Carbon Nanomaterials Electrocatalysts for Energy Storage and Conversion

Description: We are facing an energy crisis because of the limitation of the fossil fuel and the pollution caused by burning it. Clean energy technologies, such as fuel cells and metal-air batteries, are studied extensively because of this high efficiency and less pollution. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential in the process of energy storage and conversion, and noble metals (e.g. Pt) are needed to catalyze the critical chemical reactions in these devices. Funct… more
Date: May 2017
Creator: Zhao, Zhenghang
Partner: UNT Libraries
open access

Design Principles for Metal-Coordinated Frameworks as Electrocatalysts for Energy Storage and Conversion

Description: In this dissertation, density functional theory calculations are performed to calculate the thermodynamic and electrochemical properties of metal coordinated frameworks for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Gibb's free energy, overpotential, charge transfer and ligands effect are evaluated. The charge transfer analysis shows the positive charges on the metal coordinated frameworks play an essential role in improving the electrochemical properties of the metal … more
Date: December 2018
Creator: Lin, Chun-Yu
Partner: UNT Libraries
open access

Developing Modern Atom Probe Tomography for Nonmetals

Description: Atom probe tomography as a 3D atomic-scale characterization tool has seen considerable development in the past decade, both in systems improvement and theoretical understanding. However, the time and expertise required from the outset of experimentation to analyzed results is highly asymmetric between metals and nonmetals. For complex oxides, this difficulty can be exemplified by GdBa2Cu3O7-x based high-temperature superconducting coated conductors. The objective of this dissertation is to furt… more
Date: December 2022
Creator: Smith, Jesse Daniel
Partner: UNT Libraries
open access

Developing Precipitation Hardenable High Entropy Alloys

Description: High entropy alloys (HEAs) is a concept wherein alloys are constructed with five or more elements mixed in equal proportions; these are also known as multi-principle elements (MPEs) or complex concentrated alloys (CCAs). This PhD thesis dissertation presents research conducted to develop precipitation-hardenable high entropy alloys using a much-studied fcc-based equi-atomic quaternary alloy (CoCrFeNi). Minor additions of aluminium make the alloy amenable for precipitating ordered intermetallic … more
Date: August 2017
Creator: Gwalani, Bharat
Partner: UNT Libraries
open access

Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs

Description: Phosphorescent organic light emitting diodes (PHOLEDs) based on efficient electrophosphorescent dopant, platinum(II)-pyridyltriazolate complex, bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) have been studied and improved with respect to power efficiency, external efficiency, chromacity and efficiency roll-off. By studying the electrical and optical behavior of the doped devices and functionality of the various constituent layers, devices with a maximum EQE of 20.8±0.2 % and p… more
Date: August 2010
Creator: Li, Minghang
Partner: UNT Libraries
open access

Dynamic Adhesion and Self-cleaning Mechanisms of Gecko Setae and Spatulae

Description: Geckos can freely climb on walls and ceilings against their body weight at speed of over 1ms-1. Switching between attachment and detachment seem simple and easy for geckos, without considering the surface to be dry or wet, smooth or rough, dirty or clean. In addition, gecko can shed dirt particles during use, keeping the adhesive pads clean. Mimicking this biological system can lead to a new class of dry adhesives for various applications. However, gecko’s unique dry self-cleaning mechanism rem… more
Date: December 2013
Creator: Xu, Quan
Partner: UNT Libraries
open access

Effects of Plasma, Temperature and Chemical Reactions on Porous Low Dielectric Films for Semiconductor Devices

Description: Low-dielectric (k) films are one of the performance drivers for continued scaling of integrated circuit devices. These films are needed in microelectronic device interconnects to lower power consumption and minimize cross talk between metal lines that "interconnect" transistors. Low-k materials currently in production for the 45 and 65 nm node are most often organosilicate glasses (OSG) with dielectric constants near 2.8 and nominal porosities of 8-10%. The next generation of low-k materials wi… more
Date: December 2010
Creator: Osei-Yiadom, Eric
Partner: UNT Libraries

Effects of Surface Texture and Porosity on the Corrosion Behavior and Biocompatibility of Pure Zinc Biomaterials for Orthopedic Applications

Description: In this dissertation, small and large NaCl particle-derived surfaces (Ra > 40 microns) were generated on 2D Zn materials, and the surfaces were carefully studied concerning topography, corrosion behavior, and bone cell compatibility. Increases in surface roughness accelerated the corrosion rate, and cell viability was maintained. This method was then extended to 3D porous scaffolds prepared by a hybrid AM/casting technique. The scaffolds displayed a near-net shape, an interconnected pore struct… more
Date: May 2021
Creator: Cockerill, Irsalan
Partner: UNT Libraries
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