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Switchable and Memorable Adhesion of Gold-Coated Microspheres with Electrochemical Modulation

Description: Switchable adhesives using stimuli-responsive systems have many applications, including transfer printing, climbing robots, and gripping in pick and place processes. Among these adhesives, electroadhesive surface can spontaneously adjust their adhesion in response to an external electric field. However, electroadhesives usually need high voltage (e.g. kV) and the adhesion disappears upon turning off the signal. These limitations make them complicated and costly. In this research, we demonstrate… more
Date: May 2021
Creator: Wang, Jie (Materials scientist)
Partner: UNT Libraries
open access

Structure Evolution and Nano-Mechanical Behavior of Bulk Metallic Glasses and Multi-Principal Element Alloys

Description: Bulk metallic glasses and multi-principal element alloys represent relatively new classes of multi-component engineering materials designed for satisfying multiple functionalities simultaneously. Correlating the microstructure with mechanical behavior (at the microstructural length-scales) in these materials is key to understanding their performance. In this study, the structure evolution and nano-mechanical behavior of these two classes of materials was investigated with the objective of funda… more
Date: May 2017
Creator: Mridha, Sanghita
Partner: UNT Libraries
open access

Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide

Description: A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains cor… more
Date: May 2016
Creator: Karna, Sanjay K.
Partner: UNT Libraries

Self-Healing Ceramics for High Temperature Application

Description: 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
Partner: UNT Libraries

Process-Structure-Property Relationships in Friction Stir Welded Precipitation Strengthened Aluminum Alloys

Description: Through a series of carefully designed experiments, characterization and some modeling tools, this work is aimed at studying the role of thermal profiles on different microstructural zones and associated properties like strength and corrosion through a variation of weld parameters, thermal boundary conditions and material temper. Two different alloys belonging to the Al-Cu and Al-Cu-Li system in different temper conditions- peak aged (T8) and annealed (O) were used. A 3D-thermal pseudo mechanic… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: May 2019
Creator: Mondal, Barnali
Partner: UNT Libraries
open access

Fabrication of Large-Scale and Thickness-Modulated Two-Dimensional Transition Metal Dichalcogenides [2D TMDs] Nanolayers

Description: This thesis describes the fabrication and characterization of two-dimensional transition dichalcogenides (2D TMDs) nanolayers for various applications in electronic and opto-electronic devices applications. In Chapter 1, crystal and optical structure of TMDs materials are introduced. Many TMDs materials reveal three structure polytypes (1T, 2H, and 3R). The important electronic properties are determined by the crystal structure of TMDs; thus, the information of crystal structure is explained. … more
Date: May 2019
Creator: Park, Juhong
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
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: May 2019
Creator: Cai, Bimin
Partner: UNT Libraries
open access

Surface Chemistry and Work Function of Irradiated and Nanoscale Thin Films Covered Indium Tin Oxides

Description: In this study, we used UV-ozone Ar sputtering, X-ray photoelectron and ultra-violet photoelectron spectroscopies and sputtering based depositions of RuO2 and Se nano-layers on indium tin oxides (ITOs). We elucidated the effect of Ar sputtering on the composition and chemistry of Sn rich ITO surface. We demonstrated that while a combination of UV-ozone radiation and Ar sputtering removes most of the hydrocarbons responsible for degrading the work function of ITO, it also removes significant amou… more
Date: May 2018
Creator: Che, Hui
Partner: UNT Libraries
open access

A Study on NiTiSn Low-Temperature Shape Memory Alloys and the Processing of NiTiHf High-Temperature Shape Memory Alloys

Description: Shape memory alloys (SMAs) operating as solid-state actuators pose economic and environmental benefits to the aerospace industry due to their lightweight, compact design, which provides potential for reducing fuel emissions and overall operating cost in aeronautical equipment. Despite wide applicability, the implementation of SMA technology into aerospace-related actuator applications is hindered by harsh environmental conditions, which necessitate extremely high or low transformation temperatu… more
Date: May 2018
Creator: Young, Avery W
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
open access

Friction Stir Welding of High Strength Precipitation Strengthened Aluminum Alloys

Description: Rising demand for improved fuel economy and structural efficiency are the key factors for use of aluminum alloys for light weighting in aerospace industries. Precipitation strengthened 2XXX and 7XXX aluminum alloys are the key aluminum alloys used extensively in aerospace industry. Welding and joining is the critical step in manufacturing of integrated structures. Joining of precipitation strengthened aluminum alloys using conventional fusion welding techniques is difficult and rather undesirab… more
Date: August 2016
Creator: Sidhar, Harpreet
Partner: UNT Libraries
open access

Friction Stir Welding of Precipitation Strengthened Aluminum 7449 Alloys

Description: The Al-Zn-Mg-Cu (7XXX series) alloys are amongst the strongest aluminum available. However, they are considered unweldable with conventional fusion techniques due to the negative effects that arise with conventional welding, including hydrogen porosity, hot cracking, and stress corrosion cracking. For this reason, friction stir welding has emerged as the preferred technique to weld 7XXX series alloys. Aluminum 7449 is one of the highest strength 7XXX series aluminum alloy. This is due to its hi… more
Date: August 2016
Creator: Martinez, Nelson Y
Partner: UNT Libraries
open access

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
Partner: UNT Libraries

Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate

Description: An in-depth study of Al2W3O12 negative thermal expansion (NTE) ceramic was performed, focused on synthesis, phase mappings, and the underlying mechanisms shown to be responsible for NTE. Review of the literature has shown inconsistencies in reported values of the dilatometry measured coefficients of thermal expansion, and the temperature for the known monoclinic to orthorhombic phase transition. Two synthesis techniques are introduced: an ionic-liquid non-hydrolytic sol-gel synthesis route; an… more
Date: May 2020
Creator: Rose, Kyle
Partner: UNT Libraries

Optical Emission Spectroscopy Monitoring Method for Additively Manufactured Iron-Nickel and Other Complex Alloy Samples

Description: The method of optical emission spectroscopy has been used with Fe-Ni and other complex alloys to investigate in-situ compositional control for additive manufacturing. Although additive manufacturing of metallic alloys is an emerging technology, compositional control will be a challenge that needs to be addressed for a multitude of industries going forward for next-gen applications. This current scope of work includes analysis of ionized species generated from laser and metal powder interaction … more
Date: May 2021
Creator: Flannery, David A. (David Andrew)
Partner: UNT Libraries

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

Description: 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
Partner: UNT Libraries
open access

Engineering the Uniform Lying Helical Structure in Chiral Nematic Liquid Crystal Phase: From Morphology Transition to Dimension Control

Description: Chiral nematic liquid crystals or cholesteric liquid crystals (CLC) can be obtained by adding a chiral dopant into a nematic liquid crystal. Liquid crystal molecules spontaneously rotate along a long axis to form helical structures in CLC system. Both pitch size and orientation of the helical structure is determined by the boundary conditions and can be further tuned by external stimuli. Particularly, the uniform lying helical structure of CLC has attracted intensive attention due to its beam s… more
Date: May 2021
Creator: Jia, Zhixuan
Partner: UNT Libraries

Origin of Unusually Large Hall-Petch Strengthening Coefficients in High Entropy Alloys

Description: High entropy alloys (HEAs), also referred to as complex concentrated alloys (CCAs), are a relatively new class of alloys that have gained significant attention since 2010 due to their unique balance of properties that include high strength, ductility and excellent corrosion resistance. HEAs are usually based on five or more elements alloyed in near equimolar concentrations, and exhibit simple microstructures by the formation of solid solution phases instead of complex compounds. HEAs have great… more
Date: May 2021
Creator: Jagetia, Abhinav
Partner: UNT Libraries
open access

Processing-Structure-Property Relationships of Spark Plasma Sintered Boron Carbide and Titanium Diboride Ceramic Composites

Description: The aim of this study was to understand the processing – structure – property relationships in spark plasma sintered (SPS) boron carbide (B4C) and B4C-titanium diboride (TiB2) ceramic composites. SPS allowed for consolidation of both B4C and B4C-TiB2 composites without sintering additives, residual phases, e.g., graphite, and excessive grain growth due to long sintering times. A selection of composite compositions in 20% TiB2 feedstock powder increments from 0% to 100%, was sintered at 1900°C… more
Date: May 2018
Creator: Rubink, William S.
Partner: UNT Libraries

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

Description: 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
Partner: UNT Libraries
open access

Preventing Thermal Degradation of Pvc Insulation by Mixtures of Cross-Linking Agents and Antioxidants

Description: Poly(vinyl chloride)(PVC) wire and cable insulation has poor thermal stability, causing the plasticizer to separate from the PVC chain and produce an oily residue, lowering the tensile elongation at break and thus increasing brittleness. We have added 4 wt.% of three different types of cross-linking agents and antioxidants, as well as mixtures of both, to improve the thermal stability of the plasticizer and tensile properties of PVC after thermal exposure. We performed tensile tests, tribologic… more
Date: May 2018
Creator: Kim, Taehwan
Partner: UNT Libraries
open access

Investigation into the Semiconducting and Device Properties of MoTe2 and MoS2 Ultra-Thin 2D Materials

Description: The push for electronic devices on smaller and smaller scales has driven research in the direction of transition metal dichalcogenides (TMD) as new ultra-thin semiconducting materials. These ‘two-dimensional' (2D) materials are typically on the order of a few nanometers in thickness with a minimum all the way down to monolayer. These materials have several layer-dependent properties such as a transition to direct band gap at single-layer. In addition, their lack of dangling bonding and remarkab… more
Date: May 2018
Creator: Sirota, Benjamin
Partner: UNT Libraries
open access

Recycling of PVC and XLPE for High Impact Resistance in Spool Development

Description: My work focuses on taking waste wire-grade PVC = poly(vinyl chloride) and waste XLPE = cross-linked polyethylene and recycle them into small wire/cable spool technology in order to reduce waste cost and reduce cost of spool production. The PVC and XLPE were provided by Encore Wire Corp. of McKinney, TX; they have also defined the standard to which I am comparing my results. The end goal is to incorporate as much PVC and XLPE into the spools while maintaining material toughness, impact resistanc… more
Date: May 2018
Creator: Granowski, Gregory A
Partner: UNT Libraries
open access

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
Partner: UNT Libraries
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