UNT Theses and Dissertations - 224 Matching Results

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Additive Friction Stir Deposition of Al-Ce Alloys for Improved Strength and Ductility

Description: Additive friction stir deposition (AFSD) is a solid-state additive manufacturing (AM) technique that breaks down large constituent particles into more refined and uniformly disturbed microstructure. AFSD was used to print Al-Ce alloys. Current commercial Al-alloys upon elevated temperatures go through dissolution and coarsening of strengthening precipitates causing mechanical degradation of these alloys. Al-Ce alloys do not have this issue as cerium's low solubility restricts dissolution into t… more
This item is restricted from view until January 1, 2029.
Date: December 2023
Creator: Davis, Devin Fredric
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Thermodynamics, Kinetics and Mechanical Behavior of Model Metallic Glasses

Description: The thermophysical properties and deformation behavior of a systematic series of model metallic glasses was investigated. For Zr-based metallic glasses with all metallic constituents, the activation energy of glass transition was determined to be in the range of 74-173 kJ/mol while the activation energy of crystallization was in the range of 155-170 kJ/mol. The reduced glass transition temperature was roughly the same for all the alloys (~ 0.6) while the supercooled liquid region was in the ran… more
This item is restricted from view until January 1, 2026.
Date: December 2023
Creator: Akhtar, Mst Alpona
Item Type: Refine your search to only Thesis or Dissertation
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Electrochemical Behavior of Catalytic Metallic Glasses

Description: Metallic Glasses are multi-component alloys with disordered atomic structures and unique and attractive properties such as ultra-high strength, soft magnetism, and excellent corrosion/wear resistance. In addition, they may be thermoplastically processed in the supercooled liquid region to desired shapes across multiple length-scales. Recently developed metallic glasses based on noble metals (such as Pt and Pd) are highly active in catalytic reactions such as hydrogen oxidation, oxygen reduction… more
This item is restricted from view until August 1, 2025.
Date: July 2023
Creator: Mahajan, Chaitanya
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Exploring the Synergistic Effects of MXene-based Nanocomposites for Superlubricity and Friction/Wear Reduction on Rough Steel Surfaces

Description: The aim of this thesis is to advance the field of solid lubrication science by developing coatings that provide reliable performance in ambient conditions, work on rough surfaces, and are amenable to industrial size and design complexities. Two different coating systems, Ti3C2Tx-MoS2 and Ti3C2Tx-Graphene Oxide blends, were studied in this work. The Ti3C2Tx-MoS2 nanocomposites were spray-coated onto rough 52100-grade steel surfaces, and their tribological performance was evaluated in a ball-on-d… more
Date: July 2023
Creator: Macknojia, Ali Zayaan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Next Generation Friction Stir Welding Tools for High Temperature Materials

Description: The historical success of friction stir welding (FSW) on materials such as aluminum and magnesium alloys is associated with the absence of melting and solidification during the solid-state process. However, commercial adoption of FSW on steels and other non-ferrous high-strength, high-temperature materials such as nickel-base and titanium-base alloys is limited due to the high costs associated with the process. In this dissertation, the feasibility of using an FSW approach to fabricate certain … more
This item is restricted from view until August 1, 2028.
Date: July 2023
Creator: Gaddam, Supreeth
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Small Scale Fracture Mechanisms in Alloys with Varying Microstructural Complexity

Description: Small-scale fracture behavior of four model alloy systems were investigated in the order of increasing microstructural complexity, namely: (i) a Ni-based Bulk Metallic Glass (Ni-BMG) with an isotropic amorphous microstructure; (ii) a single-phase high entropy alloy, HfTaTiVZr, with body centered cubic (BCC) microstructure; (iii) a dual-phase high entropy alloy, AlCoCrFeNi2.1, with eutectic FCC (L12) -BCC (B2) microstructure; and (iv) a Medium-Mn steel with hierarchical microstructure. The micro… more
This item is restricted from view until August 1, 2025.
Date: July 2023
Creator: Jha, Shristy
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Tribocatalytically-Active Coatings for Enhanced Tribological Performance and Carbon-Based Tribofilm Formation

Description: In this study, we investigate the fundamental mechanisms defining the approach for addressing tribological challenges in mechanical systems via the use of the tribocatalytically active coating. The coating is designed using an electrodeposition process and consists of a hard amorphous cobalt-phosphorous matrix with the incorporation of tribocatalytically-active nickel and copper. Our focus is on understanding the effect of the tribocatalytic elements, Cu vs Ni, on the coating's performance in h… more
Date: July 2023
Creator: Al Sulaimi, Rawan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

In-situ Electrochemical Surface Engineering in Additively Manufactured CoCrMo for Enhanced Biocompatibility

Description: Laser-based additive manufacturing is inherently associated with extreme, unprecedented, and rapid thermokinetics which impact the microstructural evolution in a built component. Such a unique, near to non-equilibrium microstructure/phase evolution in laser additively manufactured metallic components impact their properties in engineering application. In light of this, the present work investigates the unique microstructural traits as a result of process induced spatial and temporal variation i… more
This item is restricted from view until June 1, 2024.
Date: May 2023
Creator: Mazumder, Sangram
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

The Influence of Particle Morphology and Heat Treatment on the Microstructural Evolution of Silver Inks for Additively Manufactured RF Applications: A Comparison between Nanoflake and Reactive Inks

Description: In recent years, advancements in additive manufacturing (AM) technologies have paved the way for 3D-printed flexible hybrid electronics (FHE) and created opportunities for extending these gains to RF applications. However, printed metal interconnects and devices are typically characterized by high porosity and chemical impurities that significantly limit their electrical conductivity and RF performance compared to bulk equivalents. Using direct ink writing (DIW), two silver inks, a nanoflake su… more
Date: May 2023
Creator: Summers, Jason Masao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Laser Powder Bed Fusion of H13 Tool Steel: Experiments, Process Optimization and Microstructural Characterization

Description: This work focused on laser powder bed fusion (LPBF) of H13 tool steel to examine microstructure and melt pool morphology. Experiments were conducted with varying laser power (P) in the range of 90-180 W and scan speed (v) in the range of 500-1000 mm/s. layer thickness (l) and hatch spacing (h) were kept constant. Volumetric energy density (γ) was calculated using the above process parameters. In order to find a relation between the recorded density and top surface roughness with changing proces… more
Date: May 2023
Creator: Channa Reddy, Sumanth Kumar Reddy
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Structures of Multicomponent Silicate and Borosilicate Glasses from Molecular Dynamics Simulations: Effects of Iron Redox Ratio and Cation Field Strength

Description: Multicomponent silicate and borosilicate glasses find wide technological applications ranging from optical fibers, biomedicine to nuclear waste disposal. As a common component of earth's mantle and nuclear waste, iron is a frequent encounter in silicate and borosilicate melts and glasses. The redox ratio in glass matrix defined by the ratio of ferrous and ferric ions is dependent on factors such as temperature, pressure, and oxygen fugacity. Understanding their roles on the short- and medium-ra… more
This item is restricted from view until June 1, 2024.
Date: May 2023
Creator: Tuheen, Manzila Islam
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Development and Thermo-Mechanical Testing of Low Hysteresis Shape Memory Alloy for Satellite Actuators

Description: Shape memory alloys (SMAs) have gained much attention as a powerful source of actuation due to their improved performance, reduced size, and reduced complexity between components as well as having a high work output density. Their primary mechanism of actuation relies on a non-diffusional cyclic phase transformation from martensite to austenite, where the amount of thermal energy needed per cycle is directly associated with the hysteresis width between the austenite final and martensite final t… more
Date: December 2022
Creator: Montagnoli, Andre Luiz
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Influence of Externally Applied Magnetic Field on the Mechanical Behavior of Paramagnetic Materials

Description: Current ways to alter the microstructure of materials are usually through heat treatments, alloying, and other physical metallurgical methods. Recent efforts in the 21st century are focused on altering the microstructure of a material without physical contact which can be achieved through exposure to a magnetic field (MF). The motivation of this research is to study the quantum effects by subjecting solid-state metals to exposure of MFs. Many of the popular metals currently used in industry are… more
This item is restricted from view until January 1, 2028.
Date: December 2022
Creator: Reeder, Jessica Phoebe
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Investigation of the Processing-Induced Transition from Shape Memory to Strain Glass of Ni-Ti and Fe-Mn-Al-Cr-Ni Alloys

Description: In this study, we observed the effects of the processing-induced method on two different shape memory alloys (SMAs). First, we compare the transformation behavior of a martensitic NiTi SMA during thermal cycling using wide angle synchrotron radiation X-ray diffraction (WAXS). Based on the thermal cycling results, three observations about processing-induced SGAs as compared to SMAs can be seen: (1) retention of distorted austenite at high and low temperatures, (2) broadening of diffraction peaks… more
Date: December 2022
Creator: Ashmore, Bailey Nicole
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Processing and Shape-Setting of Shape Memory Alloys for Small Satellite Antennas

Description: In this study, four different NiTi-based shape memory alloys (SMAs) compositions were processed, shape-set, and characterized to evaluate their effectiveness as SMA actuation component for satellite antennas. Three of the compositions were commercially available NiTi wires (90°C Flexinol® actuator NiTi wire and Confluent ADB SE508 NiTi wire), NiTi SM495 plates (ATI Specialty Alloys and Components) and the other composition was in house lab-produced NiTiCu plate. Different shape-setting techniqu… more
Date: December 2022
Creator: Al Jabri, Nehal Ahmed Mubarak
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Investigation of Room Temperature Sputtering and Laser Annealing of Chalcogen Rich TMDs for Opto-Electronics

Description: Chalcogen-rich transition-metal dichalcogenide (TMD) magnetron sputtering targets were custom manufactured via ball milling and sintering in the interest of depositing p-type chalcogen-rich films. Room temperature radio frequency (RF) magnetron sputtering produced ultra-thin amorphous precursor of WSx and MoSx (where x is between 2-3) on several different substrates. The influence of working pressure on the MoS3 content of the amorphous films was explored with X-ray photoelectron spectroscopy (… more
Date: August 2022
Creator: Gellerup, Branden Spencer
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Microstructure Evolution and Mechanical Response of Material by Friction Stir Processing and Modeling

Description: In this study, we have investigated the relationship between the process-microstructure to predict and modify the material's properties. Understanding these relationships allows the identification and correction of processing deficiencies when the desired properties are not achieved, depending on the microstructure. Hence, the co-relation between process-microstructure-properties helped reduce the number of experiments, materials & tool costs and saved much time. In the case of high entropy all… more
Date: August 2022
Creator: Gupta, Sanya
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Photophysical Interactions in Vapor Synthesized and Mechanically Exfoliated Two-Dimensional Conducting Crystallites for Quantum and Optical Sensing

Description: In the first study, superconducting 2D NbSe₂ was examined towards its prototypical demonstration as a transition-edge sensor, where photoexcitation caused a thermodynamic phase transition in NbSe₂ from the superconducting state to the normal state. The efficacy of the optical absorption was found to depend on the wavelength of the incoming radiation used, which ranged from the ultra-violet (405 nm), visible (660 nm), to the infrared (1060 nm). In the second case involving WSe₂, the UV-ozone tr… more
This item is restricted from view until September 1, 2024.
Date: August 2022
Creator: Jayanand, Kishan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Processing-Structure-Property Correlation for Additively Manufactured Metastable High Entropy Alloy

Description: In the present study both fusion based - laser powder bed fusion (LPBF), and solid state - additive friction stir deposition (AFSD) additive manufacturing processes were employed for the manufacturing of a metastable high entropy alloy (HEA), Fe40Mn20Co20Cr15Si5 (CS-HEA). A processing window was developed for the LPBF and AFSD processings of CS-HEA. In case of LPBF, formation of solidification related defects such as lack of fusion pores (for energy density ≤ 31.24 J/mm3) and keyhole pores (for… more
Date: August 2022
Creator: Agrawal, Priyanshi
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Processing-Structure Relationships of Reactive Spark Plasma Sintered Diamond Composites

Description: Traditional lightweight armor ceramics such as boron carbide (B4C) and silicon carbide (SiC) are used alone or together in varying amounts to create monolithic protective plates. These materials exhibit relatively small differences in hardness, flexure strength, and fracture toughness. Many of the routes taken during the synthesis of the powder and sintering of the plates using traditional ceramic processing techniques have long processing times, tend to leave asperities within the microstruc… more
Date: August 2022
Creator: Garcia, Christian
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Scuffing and Wear Prevention in Low Viscosity Hydrocarbon Fuels

Description: To design high pressure fuel system components that resist wear and scuffing failure when operated in low viscosity fuels, a comprehensive study on the tribological performance of various existing coating materials is necessary. This thesis aims to provide the relative performance of a variety of coating materials across different fuel environments by testing them in conditions that model those experienced in fuel pumps. The relative performance of these coatings are then indexed across a varie… more
Date: August 2022
Creator: Dockins, Maddox Wade
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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