UNT Theses and Dissertations - 63 Matching Results

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Additive Manufacturing of Metastable Beta Titanium Alloys

Description: Additive manufacturing processes of many alloys are known to develop texture during the deposition process due to the rapid reheating and the directionality of the dissipation of heat. Titanium alloys and with respect to this study beta titanium alloys are especially susceptible to these effects. This work examines Ti-20wt%V and Ti-12wt%Mo deposited under normal additive manufacturing process parameters to examine the texture of these beta-stabilized alloys. Both microstructures contained co… more
Date: August 2017
Creator: Yannetta, Christopher James
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Angular Analysis of a Wide-Band Energy Harvester based on Mutually Perpendicular Vibrating Piezoelectric Beams

Description: The recent advancements in electronics and the advents of small scaled instruments has increased the attachment of life and functionality of devices to electrical power sources but at the same time granted the engineers and companies the ability to use smaller sources of power and batteries. Therefore, many scientists have tried to come up with new solutions for a power alternatives. Piezoelectric is a promising material which can readily produce continuous electric power from mechanical inputs… more
Date: December 2016
Creator: Mirzaabedini, Sohrab
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Anisotropic Nature of Radially Strained Metal Tubes

Description: Metal pipes are sometimes swaged by a metal cone to enlarge them, which increases the strain in the material. The amount of strain is important because it affects the burst and collapse strength. Burst strength is the amount of internal pressure that a pipe can withstand before failure, while collapse strength is the amount of external pressure that a pipe can withstand before failure. If the burst or collapse strengths are exceeded, the pipe may fracture, causing critical failure. Such an … more
Date: December 2015
Creator: Strickland, Julie N.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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An Assessment of Uncommon Titanium Binary Systems: Ti-Zn, Ti-Cu, and Ti-Sb

Description: The current study focuses on phase stability and evolution in the titanium-zinc titanium-copper and titanium-antimony systems. The study utilized the Laser Engineering Net Shaping (LENS™) processing technique to deposit compositionally graded samples of three binary system in order to allow the assessment of phase stability and evolution as a function of composition and temperature the material is subjected to. Through LENS™ processing it was possible to create graded samples from Ti-xSb (up … more
Date: May 2015
Creator: Brice, David
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries

Description: Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and gra… more
Date: August 2014
Creator: Chen, Chao-Hsu
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Atomistic Studies of Point Defect Migration Rates in the Iron-Chromium System

Description: Generation and migration of helium and other point defects under irradiation causes ferritic steels based on the Fe-Cr system to age and fail. This is motivation to study point defect migration and the He equation of state using atomistic simulations due to the steels' use in future reactors. A new potential for the Fe-Cr-He system developed by collaborators at the Lawrence Livermore National Laboratory was validated using published experimental data. The results for the He equation of state ag… more
Date: August 2010
Creator: Hetherly, Jeffery
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Bioresorbable Polymer Blend Scaffold for Tissue Engineering

Description: Tissue engineering merges the disciplines of study like cell biology, materials science, engineering and surgery to enable growth of new living tissues on scaffolding constructed from implanted polymeric materials. One of the most important aspects of tissue engineering related to material science is design of the polymer scaffolds. The polymer scaffolds needs to have some specific mechanical strength over certain period of time. In this work bioresorbable aliphatic polymers (PCL and PLLA) were… more
Date: May 2011
Creator: Manandhar, Sandeep
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Catalytic Properties and Mechanical Behavior of Metallic Glass Powders

Description: Lack of crystalline order and microstructural features such as grain/grain-boundary in metallic glasses results in a suite of remarkable attributes including very high strength, close to theoretical elasticity, high corrosion and wear resistance, and soft magnetic properties. By altering the morphology and tuning of composition, MGs may be transformed into high-performance catalytic materials. In this study, the catalytic properties of metallic glass powders were demonstrated in dissociating to… more
Date: May 2017
Creator: Garrison, Seth
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Characterization of Ti-6Al-4V Produced Via Electron Beam Additive Manufacturing

Description: In recent years, additive manufacturing (AM) has become an increasingly promising method used for the production of structural metallic components. There are a number of reasons why AM methods are attractive, including the ability to produce complex geometries into a near-net shape and the rapid transition from design to production. Ti-6Al-4V is a titanium alloy frequently used in the aerospace industry which is receiving considerable attention as a good candidate for processing via electron be… more
Date: December 2015
Creator: Hayes, Brian J.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Charpy Impact Testing of Twinning Induced Plasticity and Transformation Induced Plasticity High Entropy Alloys

Description: High entropy alloys (HEAs) are a new class of solid solution alloys that contain multiple principal elements and possess excellent mechanical properties, from corrosion resistance to fatigue and wear resistance. Even more recently, twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) non-equiatomic high entropy alloys have been engineered, promising increased strength and ductility as compared to their equiatomic counterparts. However, impact and fracture resistance o… more
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Date: August 2019
Creator: Zellner, Samantha R
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Compostable Soy-Based Polyurethane Foam with Kenaf Core Modifiers

Description: Building waste and disposable packaging are a major component in today's landfills. Most of these are structural or thermally insulative polymer foams that do not degrade over a long period of time. Currently, there is a push to replace these foams with thermoplastic or biodegradable foams that can either be recycled or composted. We propose the use of compostable soy-based polyurethane foams (PU) with kenaf core modifiers that will offer the desired properties with the ability to choose respon… more
Date: August 2016
Creator: Hoyt, Zachary
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Corrosion Protection of Aerospace Grade Magnesium Alloy Elektron 43™ for Use in Aircraft Cabin Interiors

Description: Magnesium alloys exhibit desirable properties for use in transportation technology. In particular, the low density and high specific strength of these alloys is of interest to the aerospace community. However, the concerns of flammability and susceptibility to corrosion have limited the use of magnesium alloys within the aircraft cabin. This work studies a magnesium alloy containing rare earth elements designed to increase resistance to ignition while lowering rate of corrosion. The microst… more
Date: August 2013
Creator: Baillio, Sarah S.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Defining a Relationship between the Flexibility of Materials and Other Properties

Description: Brittleness of a polymeric material has a direct relationship with the material's performance and furthermore shares an inverse relationship with that material's flexibility. The concept of flexibility of materials has been understood but merely explained with a hand-waving manner. Thus, it has never been defined by a calculation, thereby lacking the ability to determine a definite quantitative value for this characteristic. Herein, an equation is presented and proven which makes determining th… more
Date: May 2018
Creator: Osmanson, Allison Theresa
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Determining the Emissivity of Roofing Samples: Asphalt, Ceramic and Coated Cedar

Description: The goal is to perform heat measurements examine of selected roofing material samples. Those roofing materials are asphalt shingles, ceramics, and cedar. It’s important to understand the concept of heat transfer, which consists of conduction, convection, and radiation. Research work was reviewed on different infrared devices to see which one would be suitable for conducting my experiment. In this experiment, the main focus was on a specific property of radiation. That property is the emissivit… more
Date: December 2015
Creator: Adesanya, Oludamilola
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Dislocation Dynamics Simulations of Plasticity in Cu Thin Films

Description: Strong size effects in plastic deformation of thin films have been experimentally observed, indicating non-traditional deformation mechanisms. These observations require improved understanding of the behavior of dislocation in small size materials, as they are the primary plastic deformation carrier. Dislocation dynamics (DD) is a computational method that is capable of directly simulating the motion and interaction of dislocations in crystalline materials. This provides a convenient approach t… more
Date: August 2013
Creator: Wu, Han
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Dynamic Deformation and Shear Localization in Friction-Stir Processed Al0.3CoCrFeNi and Fe50Mn30Co10Cr10 High-Entropy Alloys

Description: High entropy alloys (HEAs) are a relatively new class of solid solution alloys that contain multiple principal elements to take advantage of their high configurational entropy, sluggish diffusion, lattice distortion, and the cocktail effect. In recent development, work hardening mechanisms known as twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) have been found active in Al0.3CoCrFeNi (molar fraction) and Fe50Mn30Co10Cr10 (at %) HEA compositions. Friction-stir pr… more
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Date: August 2019
Creator: Macdonald, Neil
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Dynamic Precipitation of Second Phase Under Deformed Condition in Mg-nd Based Alloy

Description: Magnesium alloys are the lightweight structural materials with high strength to weigh ratio that permits their application in fuel economy sensitive automobile industries. Among the several flavors of of Mg-alloys, precipitation hardenable Mg-rare earth (RE) based alloys have shown good potential due to their favorable creep resistance within a wide window of operating temperatures ranging from 150°C to 300°C. A key aspect of Mg-RE alloys is the presence of precipitate phases that leads to str… more
Date: December 2013
Creator: Dendge, Nilesh Bajirao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Effect of Alloy Composition, Free Volume and Glass Formability on the Corrosion Behavior of Bulk Metallic Glasses

Description: Bulk metallic glasses (BMGs) have received significant research interest due to their completely amorphous structure which results in unique structural and functional properties. Absence of grain boundaries and secondary phases in BMGs results in high corrosion resistance in many different environments. Understanding and tailoring the corrosion behavior can be significant for various structural applications in bulk form as well as coatings. In this study, the corrosion behavior of several Zr-ba… more
Date: December 2015
Creator: Ayyagari, Venkata Aditya
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Effect of Friction-stir Processing on the Wear Behavior of Titanium (Ti-1Al-8V-5Fe) and Stainless Steel (A-286) Alloys

Description: The effect of friction stir processing (FSP) on the mechanical wear behavior was investigated for Ti-1Al-8V-5Fe (Ti-185) and stainless steel (Incoloy® A-286) alloys. The Ti-185 and A-286 alloys were tested in different processing conditions, including as rolled (AR), AR+FSP, and AR+FSP+aged. A high frequency reciprocating rig was used to simulate fretting-type wear of these alloys at room temperature. The Vickers micro-hardness and wear rates were calculated and compared for each processing co… more
Date: May 2015
Creator: Tinubu, Olusegun Olukunle
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

The Effect of Processing Conditions on the Surface Morphology of Few-Layered WS2 Thin Films

Description: Recent progress in layered transition metal dichalcogenides (TMDs) has led to various promising electronic and optoelectronic applications. However, the structure of materials plays a critical role in electronic and optoelectronic devices, and determines performance. Electronic and optoelectronic devices typically consist of multiple layers that form electrical homojunctions or heterojunctions. Therefore, in a device it can be expected that a WS2 layer may serve as the substrate for a subseque… more
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Date: May 2019
Creator: Cai, Bimin
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Effect of Retting on Surface Chemistry and Mechanical Performance Interactions in Natural Fibers for High Performance Polymer Composites

Description: Sustainability through replacement of non-renewable fibers with renewable fibers is an ecological need. Impact of transportation costs from South-east Asia on the life cycle analysis of the composite is detrimental. Kenaf is an easily grown crop in America. Farm based processing involves placing the harvested crop in rivers and ponds, where retting of the fibers from the plant (separation into fibers) can take 2 weeks or more. The objective of this thesis is to analyze industrially viable proce… more
Date: May 2013
Creator: Ramesh, Dinesh
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Effects of HALSs and Nano-ZnO Worked as UV Stabilizers of Polypropylene

Description: This work reports the outdoor weathering performance of ultraviolet (UV)-stabilized polypropylene (PP) products (using PP resins from Encore Wire). Different hindered amine light stabilizers (HALSs) and nano-ZnO were used to stabilize PP-film-based formulations that were exposed under UV light for 6 weeks simulating for in harsh outdoor weather of Dallas, Texas, USA in 2016. Characterization of the exposed PP film products was done in terms of mechanical and friction spectroscopic properties. T… more
Date: December 2017
Creator: Lu, Xinyao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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First Principle Calculations of the Structure and Electronic Properties of Pentacene Based Organic and ZnO Based Inorganic Semiconducting Materials

Description: In this thesis, I utilize first principles density functional theory (DFT) based calculations to investigate the structure and electronic properties including charge transfer behaviors and work function of two types of materials: pentacene based organic semiconductors and ZnO transparent conducting oxides, with an aim to search for high mobility n-type organic semiconductors and fine tuning work functions of ZnO through surface modifications. Based on DFT calculations of numerous structure comb… more
Date: May 2012
Creator: Li, Yun
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Glass Forming Ability, Magnetic Properties, and Mechanical Behavior of Iron-Based and Cobalt-Based Metallic Glasses

Description: Lack of crystalline order and microstructural features such as grain/grain-boundary in metallic glasses results in a suite of remarkable attributes including very high strength, close to theoretical elasticity, high corrosion and wear resistance, and soft magnetic properties. In particular, low coercivity and high permeability of iron and cobalt based metallic glass compositions could potentially lead to extensive commercial use as magnetic heads, transformer cores, circuits and magnetic shield… more
Date: December 2014
Creator: Veligatla, Medha
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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