UNT Theses and Dissertations - 144 Matching Results

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Laser Deposition, Heat-treatment, and Characterization of the Binary Ti-xmn System

Description: The present research seeks to characterization of an additively manufactured and heat-treated Ti-xMn gradient alloy, a binary system that has largely been unexplored. In order to rapidly assess this binary system, compositionally graded Ti-xMn (0<x<15 wt%) specimens were fabricated using the LENS (Laser Engineered Net Shaping) and were subsequently heat-treated and characterized using a wide range of techniques. Microstructural changes with respect to the change in thermal treatments, hardness … more
Date: August 2013
Creator: Avasarala, Chandana
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Laser Modified Alumina: a Computational and Experimental Analysis

Description: Laser surface modification involves rapid melting and solidification is an elegant technique used for locally tailoring the surface morphology of alumina in order to enhance its abrasive characteristics. COMSOL Multiphysics® based heat transfer modeling and experimental approaches were designed and used in this study for single and multiple laser tracks to achieve densely-packed multi-facet grains via temperature history, cooling rate, solidification, scanning electron micrographs, and wear rat… more
Date: December 2012
Creator: Moncayo, Marco Antonio
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Laser Surface Alloying of Refractory Metals on Aluminum for Enhanced Corrosion Resistance: Experimental and Computational Approaches

Description: Aluminum (Al) and its alloys are widely used in various technological applications, mainly due to the excellent thermal conductivity, non-magnetic, ecofriendly, easy formability and good recyclability. However due to the inferior corrosion resistance its applications are hampered in various engineering sectors. Besides, the corrosion related failures such as leakage of gas from pipeline, catastrophic breakdown of bridges and fire accidents in processing plants further puts the human life in jeo… more
Date: December 2014
Creator: Rajamure, Ravi Shanker
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Laser Surface Modification of AZ31B Mg Alloy Bio-Implant Material

Description: Magnesium and its alloys are considered as the potential biomaterials due to their biocompatibility and biodegradable characteristics but suffer from poor corrosion performance. Various surface modification techniques are employed to improve their corrosion resistance. In present case, laser surface melting was carried out on AZ31B Mg alloy with various laser energy densities using a continuous wave ytterbium laser. Effect of laser treatment on phase and microstructure evolution was evaluated b… more
Date: August 2018
Creator: Wu, Tso-chang
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Laser Surface Modification on Az31b Mg Alloy for Bio-wettability

Description: Laser surface modification of AZ31B Magnesium alloy changes surface composition and roughness to provide improved surface bio-wettability. Laser processing resulted in phase transformation and grain refinement due to rapid quenching effect. Furthermore, instantaneous heating and vaporization resulted in removal of material, leading the textured surface generation. A study was conducted on a continuum-wave diode-pumped ytterbium laser to create multiple tracks for determining the resulting bio-w… more
Date: December 2013
Creator: Ho, YeeHsien
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Laser Surface Treatment of Amorphous Metals

Description: Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precu… more
Date: May 2014
Creator: Katakam, Shravana K.
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Linking Enhanced Fatigue Life to Design by Modifying the Microstructure

Description: Structural material fatigue is a leading cause of failure and has motivated fatigue-resistant design to eliminate risks to human lives. Intrinsic microstructural features alter fatigue deformation mechanisms so profoundly that, essentially, fatigue properties of structural materials become deviant. With this in mind, we initiated this project to investigate the microstructural effect on fatigue behavior of potential structural high entropy alloys. With a better understanding of the effect of mi… more
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Date: August 2019
Creator: Liu, Kaimiao
Item Type: Refine your search to only Thesis or Dissertation
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Maleic anhydride grafted polypropylene coatings on steel: Adhesion and wear.

Description: Polymeric coatings are being used in a growing number of applications, contributing to protection against weather conditions and localized corrosion, reducing the friction and erosion wear on the substrate. In this study, various polypropylene (PP) coatings were applied onto steel substrates by compression molding. Chemical modification of PP has been performed to increase its adhesion to metallic surfaces by grafting of maleic anhydride (MAH) onto PP in the presence of dicumyl peroxide (DCP). … more
Date: May 2010
Creator: Mahendrakar, Sridhar
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Mechanics and Mechanisms of Creep and Ductile Fracture

Description: The main aim of this dissertation is to relate measurable and hopefully controllable features of a material's microstructure to its observed failure modes to provide a basis for designing better materials. The understanding of creep in materials used at high temperatures is of prime engineering importance. Single crystal Ni-based superalloys used in turbine aerofoils of jet engines are exposed to long dwell times at very high temperatures. In contrast to current theories, creep tests on Ni-base… more
Date: August 2013
Creator: Srivastava, Ankit
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Mechanisms of Formation and Effects of Transition Metal Oxides in Silicon Nitride on Steel Dry Sliding Contacts

Description: Silicon nitride on steel sliding contacts may provide advantageous tribological properties over traditional self-mated pairs, however the friction and wear behavior at high sliding speeds (>1 m/s) is not well understood. Previous studies at low sliding speeds (< 1 m/s) have found that the wear mechanisms change as a function of the operating parameters, e.g. atmosphere, sliding speed, load, and temperature, due to the formation of transition metal oxides such as Fe2O3 and Fe3O4. This study dete… more
Date: December 2018
Creator: Harris, Michael D.
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Mechanisms of Ordered Gamma Prime Precipitation in Nickel Base Superalloys

Description: Commercial superalloys like Rene88DT are used in high temperature applications like turbine disk in aircraft jet engines due to their excellent high temperature properties, including strength, ductility, improved fracture toughness, fatigue resistance, enhanced creep and oxidation resistance. Typically this alloy's microstructure has L12-ordered precipitates dispersed in disordered face-centered cubic &#947; matrix. A typical industrially relevant heat-treatment often leads to the formation of … more
Date: May 2011
Creator: Singh, Antariksh Rao Pratap
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Microstructural Evolution and Mechanical Response of Materials by Design and Modeling

Description: Mechanical properties of structural materials are highly correlated to their microstructure. The relationship between microstructure and mechanical properties can be established experimentally. The growing need for structural materials in industry promotes the study of microstructural evolution of materials by design using computational approaches. This thesis presents the microstructural evolution of two different structural materials. The first uses a genetic algorithm approach to study the m… more
Date: May 2017
Creator: Dutt, Aniket Kumar
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Microstructure Evolution in Laser Deposited Nickel-Titanium-Carbon in situ Metal Matrix Composite

Description: Ni/TiC metal matrix composites have been processed using the laser engineered net shaping (LENS) process. As nickel does not form an equilibrium carbide phase, addition of a strong carbide former in the form of titanium reinforces the nickel matrix resulting in a promising hybrid material for both surface engineering as well as high temperature structural applications. Changing the relative amounts of titanium and carbon in the nickel matrix, relatively low volume fraction of refined homogeneou… more
Date: December 2010
Creator: Gopagoni, Sundeep
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Microstructure for Enhanced Plasticity and Toughness

Description: Magnesium is the lightest metal with a very high specific strength. However, its practical applicability is limited by its toughness and reliability. Mg, being HCP has low ductility. This makes the improvement of toughness a grand challenge in Mg alloys. Friction stir processing (FSP) is a thermomechanical technique used to effect microstructural modification. Here, FSP was utilized to affect the toughness of WE43 sheets through microstructural modification. Room temperature Kahn-type tests wer… more
Date: August 2016
Creator: Das, Shamiparna
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Mist and Microstructure Characterization in End Milling Aisi 1018 Steel Using Microlubrication

Description: Flood cooling is primarily used to cool and lubricate the cutting tool and workpiece interface during a machining process. But the adverse health effects caused by the use of flood coolants are drawing manufacturers' attention to develop methods for controlling occupational exposure to cutting fluids. Microlubrication serves as an alternative to flood cooling by reducing the volume of cutting fluid used in the machining process. Microlubrication minimizes the exposure of metal working fluids to… more
Date: August 2013
Creator: Shaikh, Vasim
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Modeling of High Strain Rate Compression of Austenitic Shape Memory Alloys

Description: Shape memory alloys (SMAs) exhibit the ability to absorb large dynamic loads and, therefore, are excellent candidates for structural components where impact loading is expected. Compared to the large amount of research on the shape memory effect and/or pseudoelasticity of polycrystalline SMAs under quasi-static loading conditions, studies on dynamic loading are limited. Experimental research shows an apparent difference between the quasi-static and high strain rate deformation of SMAs. Research… more
Date: December 2017
Creator: Yu, Hao
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Molecular Dynamics Simulations of the Structure and Properties of Boron Containing Oxide Glasses: Empirical Potential Development and Applications

Description: Potential parameters that can handle multi-component oxide glass systems especially boron oxide are very limited in literature. One of the main goals of my dissertation is to develop empirical potentials to simulate multi-component oxide glass systems with boron oxide. Two approaches, both by introducing the composition dependent parameter feature, were taken and both led to successful potentials for boron containing glass systems after extensive testing and fitting. Both potential sets can pro… more
Date: December 2017
Creator: Deng, Lu
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Molecular Dynamics Simulations of the Structures and Properties of Aluminosilicate and Borosilicate Glasses

Description: Silicate glasses are the most common glass types and have impact on almost every aspect in our lives: from window, containers, to glass fibers for telecommunications. Unlike their crystalline counterparts, glass materials lack long-range order in their atomic arrangement but their structures do possess short and medium range characteristics that play critical roles in their physical and chemical properties. Despite active development of characterization techniques that have contributed to the u… more
Date: December 2018
Creator: Ren, Mengguo
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Molecular Dynamics Simulations of the Structures of Europium Containing Silicate and Cerium Containing Aluminophosphate Glasses

Description: Rare earth ion doped glasses find applications in optical and photonic devices such as optical windows, laser, and optical amplifiers, and as model systems for immobilization of nuclear waste. Macroscopic properties of these materials, such as luminescence efficiency and phase stability, depend strongly on the atomic structure of these glasses. In this thesis, I have studied the atomic level structure of rare earth doped silicate and aluminophosphate glasses by using molecular dynamics simulati… more
Date: August 2012
Creator: Kokou, Leopold Lambert Yaovi
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Nano-crystallization Inhibition in 5 Nm Ru Film Diffusion Barriers for Advanced Cu-interconnect

Description: As the semiconductor industries are moving beyond 22 nm node technology, the currently used stacked Ta/TaN diffusion barrier including a copper seed will be unable to fulfill the requirements for the future technologies. Due to its low resistivity and ability to perform galvanic copper fill without a seed layer, ruthenium (Ru) has emerged as a potential copper diffusion barrier. However, its crystallization and columnar nanostructure have been the main cause of barrier failures even at low proc… more
Date: December 2013
Creator: Sharma, Bed P.
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Nano-Manufacturing of Catalytic Amorphous Alloys

Description: In this dissertation, nano-manufacturing of amorphous alloys for electro-catalytic applications is reported and the role of chemistry and active surface area on catalytic behavior is discussed. The catalytic activity of recently developed platinum and palladium-based metallic glasses was studied using cyclic voltammetry and localized electrochemical techniques. The synergistic effect between platinum and palladium was shown for amorphous alloys containing both these elements. The mechanism for … more
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Date: December 2019
Creator: Hasannaeimi, Vahid
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Nanohybrids Based on Solid and Foam Polyurethanes

Description: Polymer nanocomposites are a going part of Materials Science and Engineering. These new composite materials exhibit dimensional and thermal stability of inorganic materials and toughness and dielectric properties of polymers. Development of nanocomposites become an important approach to create high-performance composite materials. In this study silica, fly ash, silica nanotubes and carbon black particles have been added to modify polyurethane foam and thermoplastic polyurethanes. It has been fo… more
Date: May 2015
Creator: Bo, Chong
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Non-Isothermal Laser Treatment of Fe-Si-B Metallic Glass

Description: Metallic glasses possess attractive properties, such as high strength, good corrosion resistance, and superior soft magnetic performance. They also serve as precursors for synthesizing nanocrystalline materials. In addition, a new class of composites having crystalline phases embedded in amorphous matrix is evolving based on selective crystallization of metallic glasses. Therefore, crystallization of metallic glasses and its effects on properties has been a subject of interest. Previous investi… more
Date: December 2017
Creator: Joshi, Sameehan Shrikant
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P-type Doping of Pulsed Laser Deposited WS2 with Nb

Description: Layered transition metal dichalcogenides (TMDs) are potentially ideal semiconducting materials due to their in-plane carrier transport and tunable bandgaps, which are favorable properties for electrical and optoelectronic applications. However, the ability to make p-n junctions is the foundation of semiconductor devices, and therefore the ability to achieve reproducible p- and n-type doping in TMD semiconducting materials is critical. In this work, p-type substitutional doping of pulsed laser d… more
Date: December 2017
Creator: Egede, Eforma Justin
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