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in creator/contributor: "Aouadi, Samir"

Utilizing Micro-Mechanisms to Extend Fatigue Life in High Temperature Shape Memory Alloys

Shape memory alloys (SMAs) are multifunctional materials with thermoelastic phase transformation behavior capable of recovering the designed geometry after deformation. These alloys can undergo a solid-to-solid phase transformation in response to external stimuli, such as pressure or temperature, to accommodate or alleviate strain. Such a response can be utilized to design solid-state actuators by converting thermal energy into mechanical energy. Interest in these unique alloys is expanding to … more

Date: December 2024

Creator: Gantz, Faith

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Isothermal Compression of Iron-Manganese Alloys with BCC to HCP Phase Transformation

This work outlines the transformation behavior of the Fe-Mn alloy system based on two different processing methods with varying composition ranges. Fe-Mn alloys rely on the body-centered cubic to hexagonal-close packed martensitic transformation that occurs at high pressures to accommodate large amounts of strain. This phase transformation is associated with an atomic volumetric contraction which can be altered by controlling the amount of manganese in the alloy. In this thesis, using synchrotr… more

Date: December 2024

Creator: Harris, Jessica Austria

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Rapid Synthesis of Nanoporous Conformal Coatings via Plasma-Enhanced Sequential Infiltration of a Polymer Template

This article reports a plasma-enhanced sequential infiltration synthesis (PE SIS) as a new platform toward deposition of nanoporous inorganic films.

Date: November 10, 2017

Creator: She, Yunlong; Lee, Jihyung; Diroll, Benjamin T.; Lee, Byeongdu; Aouadi, Samir; Shevchenko, Elena V. et al.

Item Type: Article

Partner: UNT College of Engineering

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

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

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Date: December 2022

Creator: Reeder, Jessica Phoebe

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Characterization and Chemical Analysis of Fundamental Components for Lead Acid Batteries

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: Thesis or Dissertation

Partner: UNT Libraries

Developing Ultra-Fast Plasmonic Spiking Neuron via Integrated Photonics

This research provides a proof of concept and background theory for the physics behind the state-of-the-art ultra-fast plasmonic spiking neurons (PSN), which can serve as a primary synaptic device for developing a platform for fast neural computing. Such a plasmonic-powered computing system allows localized AI with ultra-fast operation speed. The designed architecture for a plasmonic spiking neuron (PSN) presented in this thesis is a photonic integrated nanodevice consisting of two electro-opti… more

Date: August 2022

Creator: Goudarzi, Abbas, Sr.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Design and Performance of Metal Matrix Composite Composed of Porous Boron Carbide Created by Magnetic Field-Assisted Freeze Casting Infiltrated with Aluminum (A356)

Magnetic field-assisted freeze-casting was used to create porous B4C ceramic preforms. An optimum slurry consisted of a mixture of B4C powders with 6 wt.% Er2O3 powder in an H2O-PVA solution and was cooled at a rate of 1 °C/min from room temperature to -30 °C resulting in porous green state ceramic preform with vertical channels. The Er2O3 powder was added to improve the magnetic response of the slurry. The preform was then sublimated to remove H2O and then sintered. The sintered ceramic prefor… more

Date: May 2022

Creator: Gamboa, Gerardo

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Mechanically Driven Reconstruction of Materials at Sliding Interfaces to Control Wear

To minimize global carbon emissions, having efficient jet engines and internal combustion engines necessitates utilizing lightweight alloys such as Al, Ti, and Mg-based alloys. Because of their remarkable strength/weight ratio, these alloys have received a lot of attention. Nonetheless, they have very poor tribological behavior, particularly at elevated temperatures beyond 200 °C, when most liquid lubricants begin to fail in lubrication. Over the last two decades, there has been a lot of intere… more

Date: May 2022

Creator: Shirani, Asghar

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Fractography and Mechanical Properties of Laminated Alumina and Yttria Stabilized Zirconia

Yttria stabilized zirconia (YSZ) is a polymorph with possible phase transformation toughening occurring during impact. The fractography and mechanical properties of laminated alumina and YSZ were studied in this thesis. Five sample types were studied in this thesis: (5:5) Al2O3/YSZ (a sequence of 5 alumina tapes stacked on 5 YSZ tapes), (5:5) Al2O3/YSZ (1 wt.% Pure ZrO2), (7:3) Al2O3/YSZ, Al2O3, and YSZ. Scanning electron microscopy (SEM) and X-ray microscopy (XRM) were used to study morphology… more

Date: December 2021

Creator: Cotton, Shomari Johnny

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Defect-Engineered Two-Dimensional Transition Metal Dichalcogenides for High-Efficient Piezoelectric Sensor

Piezoelectricity in two-dimensional (2D) transition metal dichalcogenides (TMDs) has attracted significant attention due to their unique crystal structure and the lack of inversion centers when the bulk TMDs thin down to monolayer. Although the piezoelectricity effect in atomic-thickness TMDs has been demonstrated, they are not scalable. Herein, we demonstrate a piezoelectric effect from large-scale, sputtered MoS2 and WS2 using a robust defect-engineering based on the thermal-solvent annealing… more

Date: May 2021

Creator: Kim, Junyoung

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Investigation of Porous Ceramic Structure by Freeze-Casting

The design and fabrication of porous ceramic materials with anisotropic properties has, in recent years, gained popularity due to their potential application in various areas that include medical, energy, defense, space, and aerospace. Freeze-casting is an effective, low-cost, and safe method as a wet shaping technique to create these structures. To control the morphology of these materials, many critical factors were found to play an important role. In this dissertation, the processing paramet… more

Date: May 2021

Creator: Bakkar, Said Adnan

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Processing-Structure Relationships of Reactive Spark Plasma Sintered Diamond Composites

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: Thesis or Dissertation

Partner: UNT Libraries

open access

Unraveling the Effect of Atomic Configurations and Structural Statistics on Mechanical Behavior of Multicomponent and Amorphous Alloys

Multicomponent high-entropy and amorphous alloys represent relatively new classes of structural materials with complex atomic configurations and exceptional mechanical properties. However, there are several knowledge gaps in the relationships between their atomic structure and mechanical properties. Understanding these critical relationships will enable novel alloy design and tailoring of their mechanical properties for desired engineering applications. In this dissertation, first-principles ca… more

Date: December 2021

Creator: Yang, Yu Chia

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Self-Healing Ceramics for High Temperature Application

Ceramics have a wide variety of applications due to their unique properties; however, the low fracture toughness leads the formation and propagation of unpredictable cracks, and reduces their reliability. To solve this problem, self-healing adaptive oxides were developed. The aim of the work is to gain new insights into self-healing mechanisms of ceramics and their application. Binary oxide systems were investigated that are at least partially healed through the extrinsic or intrinsic addition … more

Date: August 2021

Creator: Gu, Jingjing

Item Type: Thesis or Dissertation

Partner: UNT Libraries

High Strain Rate Deformation Behavior of Single-Phase and Multi-Phase High Entropy Alloys

Fundamental understanding of high strain rate deformation behavior of materials is critical in designing new alloys for wide-ranging applications including military, automobile, spacecraft, and industrial applications. High entropy alloys, consisting of multiple elements in (near) equimolar proportions, represent a new paradigm in structural alloy design providing ample opportunity for achieving excellent performance in high strain rate applications by proper selection of constituent elements a… more

Date: May 2021

Creator: Muskeri, Saideep

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Fabrication of the Novel Asymmetric Polymeric Materials via Bottom-Up Approach

Asymmetric polymeric materials can be formed by either top-down or bottom-up methods. Bottom-up methods involve assembling the atoms and molecules to form small nanostructures by carefully controlled synthesis, which results in a reduction of some of the top-down limitations. In this dissertation, thermal, tribological and antireflective properties of polymeric materials have been enhanced by introducing structural asymmetry. The overall performance of commercial polymeric coatings, e.g. epoxy … more

Date: May 2022

Creator: Hnatchuk, Nataliia

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Effect of Modifier Cation Substitution on Structure and Properties of Bioactive Glasses from Molecular Dynamics Simulations

Bioactive glass is a type of third generation bioactive material that can bond to both soft and hard tissue with applications ranging from bone defect repair, coatings for metallic implants, to scaffolds for tissue engineering. Design of bioactive glasses for these applications rely on a detailed understanding of the structures of these glasses which are complicated and multicomponent. In this thesis, I have applied molecular dynamics (MD) simulations with interatomic potentials developed in ou… more

Date: May 2022

Creator: Vu, Myra

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Time-Dependent Deformation Mechanisms in Metallic Glasses as a Function of Their Structural State

In this study, the time-dependent deformation behavior of several model bulk metallic glasses (BMGs) was studied. The BMGs were obtained in different structural states by thermal relaxation below their glass transition temperature, cryogenic thermal cycling, and chemical rejuvenation by micro-alloying. The creep behavior of Zr52.5Ti5Cu17.9Ni14.6Al10 BMG in different structural states was investigated as a function of peak load and temperature. The creep strain rate sensitivity (SRS) indicated a… more

Date: May 2022

Creator: Ghodki, Nandita

Item Type: Thesis or Dissertation

Partner: UNT Libraries

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

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

Date: May 2022

Creator: Patel, Kunjalkumar Babubhai

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Wear, Friction and High Shear Strain Deformation of Metallic Glasses

In this work, wear and scratch behavior of four different bulk metallic glasses (BMGs) namely Zr41.2Cu12.5Ni10Ti13.8Be22.5 (LM 1), Zr57Cu15.4Ni12.6Al10Nb5 (LM 106), Ni60Pd20P17B3 (Ni-BMG), and Pt57.5Cu14.7Ni5.3P22.5 (Pt-BMG) were compared. Shear band formation on the edges of the scratch groove with spallation was found to be the primary failure mechanism in progressive scratch tests. The wear behavior and the scratch response of model binary Ni-P metallic glasses was systematically studied as … more

Date: May 2022

Creator: Pole, Mayur

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Scuffing and Wear Prevention in Low Viscosity Hydrocarbon Fuels

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: Thesis or Dissertation

Partner: UNT Libraries

open access

In-situ Analysis of the Evolution of Surfaces and Interfaces under Applied Coupled Stresses

To study the effect of the substrate support on the nanoscale contact, three different regimes, i.e., graphene on rigid (ultra-crystalline diamond) and on elastic (Polydimethylsiloxane) supports and free-standing graphene, were considered. The contribution of the graphene support to the mechanical and electrical characteristics of the graphene/metal contact was studied using the conductive atomic force microscopy (AFM) technique.The results revealed that the electrical conductivity of the graph… more

Date: August 2020

Creator: Lee, Ji Hyung

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Optical Property Study of 2D Graded Photonic Super-Crystals for Photon Management

In this dissertation, we study the optical property of 2D graded photonic super-crystals (GPSCs) for photon management. We focused primarily on manipulation and control of light by using the newly discovered GPSCs which present great opportunity for electromagnetic wave control in photonic devices. The GPSC has been used to explore the superior capability of improving the light extraction efficiency of OLEDs. The enhancement of extraction efficiency has been explained in term of destructive int… more

Date: May 2020

Creator: Hassan, Safaa

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Tribo-Corrosion of High Entropy Alloys

In this dissertation, tribo-corrosion behavior of several single-phase and multi-phase high entropy alloys were investigated. Tribo-corrosion of body centered cubic MoNbTaTiZr high entropy alloy in simulated physiological environment showed very low friction coefficient (~ 0.04), low wear rate (~ 10-8 mm3/Nm), body-temperature assisted passivation, and excellent biocompatibility with respect to stem cells and bone forming osteoblast cells. Tribo-corrosion resistance was evaluated for additively… more

Date: December 2020

Creator: Shittu, Jibril

Item Type: Thesis or Dissertation

Partner: UNT Libraries