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Stable Nanocrystalline Au Film Structures for Sliding Electrical Contacts

Description: Hard gold thin films and coatings are widely used in electronics as an effective material to reduce the friction and wear of relatively less expensive electrically conductive materials while simultaneously seeking to provide oxidation resistance and stable sliding electrical contact resistance (ECR). The main focus of this dissertation was to synthesize nanocrystalline Au films with grain structures capable of remaining stable during thermal exposure and under sliding electrical contact stress… more
Date: May 2016
Creator: Mogonye, Jon-Erik
Item Type: Refine your search to only Thesis or Dissertation
open access

Structural, Thermal and Acoustic Performance of Polyurethane Foams for Green Buildings

Description: Decreasing the carbon footprint through use of renewable materials has environmental and societal impact. Foams are a valuable constituent in buildings by themselves or as a core in sandwich composites. Kenaf is a Southeast USA plant that provides renewable filler. The core of the kenaf is porous with a cell size in a 5-10 micrometer range. The use of kenaf core in foams represents a novel multiscalar cellular structural composite. Rigid polyurethane foams were made using free foaming expansion… more
Date: December 2014
Creator: Nar, Mangesh
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation
open access

A Study of Mechanisms to Engineer Fine Scale Alpha Phase Precipitation in Beta Titanium Alloy, Beta 21S

Description: Metastable b-Ti alloys are titanium alloys with sufficient b stabilizer alloying additions such that it's possible to retain single b phase at room temperature. These alloys are of great advantage compared to a/b alloys since they are easily cold rolled, strip produced and can attain excellent mechanical properties upon age hardening. Beta 21S, a relatively new b titanium alloy in addition to these general advantages is known to possess excellent oxidation and corrosion resistance at elevated t… more
Date: August 2013
Creator: Behera, Amit Kishan
Item Type: Refine your search to only Thesis or Dissertation
open access

A Study of Power Generation From a Low-cost Hydrokinetic Energy System

Description: The kinetic energy in river streams, tidal currents, or other artificial water channels has been used as a feasible source of renewable power through different conversion systems. Thus, hydrokinetic energy conversion systems are attracting worldwide interest as another form of distributed alternative energy. Because these systems are still in early stages of development, the basic approaches need significant research. The main challenges are not only to have efficient systems, but also to conve… more
Date: August 2013
Creator: Davila Vilchis, Juana Mariel
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation

Substrate Nanotopography and Stiffness Modulation of Cell Behavior

Description: The physical characteristics (i.e., nanostructure and stiffness) of the extracellular matrix where cells reside have been shown to profoundly affect numerous cellular events in vivo and also been employed to modulate cell behavior in vitro, yet how these physical cues regulate cell behavior is still elusive. Therefore, we engineered a variety of nanotopographies with different shapes and dimensions, and investigated how the nanotopographical cue, through focal adhesions-cytoskeleton-nucleus pat… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: May 2019
Creator: Wang, Kai
Item Type: Refine your search to only Thesis or Dissertation
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
Item Type: Refine your search to only Thesis or Dissertation
open access

Surface Degradation Behavior of Bulk Metallic Glasses and High Entropy Alloys

Description: In this study, the surface degradation behavior was studied for typical examples from bulk metallic glasses (BMGs), metallic glass composites (MGCs) and high entropy alloys (HEAs) alloy systems that are of scientific and commercial interest. The corrosion and wear behavior of two Zr-based bulk metallic glasses, Zr41.2Cu12.5Ni10Ti13.8Be22.5 and Zr57Cu15.4Ni12.6Al10Nb5, were evaluated in as-cast and thermally relaxed states. Significant improvement in corrosion rate, wear behavior, and friction c… more
Date: December 2017
Creator: Ayyagari, Venkata A
Item Type: Refine your search to only Thesis or Dissertation
open access

Surface Modifications to Enhance the Wear Resistance and the Osseo-integration Properties of Biomedical Ti-alloy

Description: The current study focuses on improving the wear resistance of femoral head component and enhancing the osseo-integration properties of femoral stem component of a hip implant made of a new generation low modulus alloy, Ti-35Nb-7Zr-5Ta or TNZT. Different techniques that were adopted to improve the wear resistance of low-modulus TNZT alloy included; (a) fabrication of graded TNZT-xB (x= 0, 1, 2 wt%) samples using LENS, (b) oxidation, and (c) LASER nitriding of TNZT. TNZT-1B and TNZT-O samples hav… more
Date: August 2013
Creator: Kami, Pavani
Item Type: Refine your search to only Thesis or Dissertation
open access

Surface Topography and Aesthetics of Recycled Cross-Linked Polyethylene Wire and Cable Coatings

Description: Our research focuses on re-using a waste a material, cross-linked polyethylene abbreviated XLPE, which is a widely used coating for wires. XLPE is strong and has excellent thermal properties due to its chemical structure - what leads to the significance of recycling this valuable polymer. Properties of XLPE include good resistance to heat, resistance to chemical corrosion, and high impact strength. A wire is usually composed of a metal core conductor and polymeric coating layers. One creates a … more
Date: December 2014
Creator: Xie, Wa
Item Type: Refine your search to only Thesis or Dissertation
open access

Synchrotron Radiation X-Ray Diffraction of Nickel-Titanium Shape Memory Alloy Wires During Mechanical Deformation

Description: Shape memory alloys (SMAs) are a new generation material which exhibits unique nonlinear deformations due to a phase transformation which allows it to return to its original shape after removal of stress or a change in temperature. It shows a shape memory effect (martensitic condition) and pseudoelasticity (austenitic condition) properties depends on various heat treatment conditions. The reason for these properties depends on phase transformation through temperature changes or applied stress. … more
Date: December 2015
Creator: Zhang, Baozhuo
Item Type: Refine your search to only Thesis or Dissertation
open access

Ternary Oxide Structures for High Temperature Lubrication

Description: In this research, a temperature dependent tribological investigation of selected ternary oxides was undertaken. Based on the promising results of previous studies on silver based ternary oxides, copper based ternary oxides were selected to conduct a comparative study since both copper and silver are located in the same group in the periodic table of the elements. Two methods were used to create ternary oxides: (i) solid chemical synthesis to create powders and (ii) sputtering to produce thin fi… more
Date: August 2015
Creator: Gu, Jingjing
Item Type: Refine your search to only Thesis or Dissertation
open access

Thermomechanical Processing, Additive Manufacturing and Alloy Design of High Strength Mg Alloys

Description: The recent emphasis on magnesium alloys can be appreciated by following the research push from several agencies, universities and editorial efforts. With a density equal to two-thirds of Al and one-thirds of steel, Mg provides the best opportunity for lightweighting of metallic components. However, one key bottleneck restricting its insertion into industrial applications is low strength values. In this respect, Mg-Y-Nd alloys have been promising due to their ability to form strengthening precip… more
Date: May 2016
Creator: Palanivel, Sivanesh
Item Type: Refine your search to only Thesis or Dissertation
open access

Thermoplastic and Thermoset Natural Fiber Composite and Sandwich Performance

Description: The objective of this thesis is to investigate the effects of adding natural fiber (kenaf fiber, retted kenaf fiber, and sugarcane fiber) into polymer materials. The effects are obtained by considering three main parts. 1. Performance in thermoplastic composites. The effect of fiber retting on polymer composite crystallization and mechanical performance was investigated. PHBV/PBAT in 80/20 blend ratio was modified using 5% by weight kenaf fiber. Dynamic mechanical analysis of the composites was… more
Date: May 2014
Creator: Yang, Bing
Item Type: Refine your search to only Thesis or Dissertation
open access

Thin Films As a Platform for Understanding the Conversion Mechanism of FeF2 Cathodes in Lithium-Ion Microbatteries

Description: Conversion material electrodes such as FeF2 possess the potential to deliver transformative improvements in lithium ion battery performance because they permit a reversible change of more than one Li-ion per 3d metal cation. They outperform current state of the art intercalation cathodes such as LiCoO2, which have volumetric and gravimetric energy densities that are intrinsically limited by single electron transfer. Current studies focus on composite electrodes that are formed by mixing with ca… more
Date: August 2015
Creator: Santos-Ortiz, Reinaldo
Item Type: Refine your search to only Thesis or Dissertation
open access

Three-Dimensional Carbon Nanostructure and Molybdenum Disulfide (MoS2) for High Performance Electrochemical Energy Storage Devices

Description: My work presents a novel approach to fabricate binder free three-dimensional carbon nanotubes/sulfur (3DCNTs/S) hybrid composite by a facile and scalable method increasing the loading amount from 1.86 to 8.33 mg/cm2 highest reported to date with excellent electrochemical performance exhibiting maximum specific energy of ~1233Wh/kg and specific power of ~476W/kg, with respect to the mass of the cathode. Such an excellent performance is attributed to the fact that 3DCNTs offers higher loading amo… more
Date: December 2017
Creator: Patel, Mumukshu D.
Item Type: Refine your search to only Thesis or Dissertation
open access

Titanium Boride Formation and Its Subsequent Influence on Morphology and Crystallography of Alpha Precipitates in Titanium Alloys

Description: Over the last two decades there has been an increased interest in understanding the influence of trace boron additions in Ti alloys. These additions refine the prior β grain size in as-cast Ti alloys along with increasing their modulus and yield strength due to the precipitation of TiB. TiB also acts as a heterogeneous nucleation site for α precipitation and has been shown to influence the α phase morphology. B is completely soluble in liquid Ti but has a negligible solubility in both body cent… more
Date: December 2013
Creator: Nandwana, Peeyush
Item Type: Refine your search to only Thesis or Dissertation
open access

Tribological Behavior of Spark Plasma Sintered Tic/graphite/nickel Composites and Cobalt Alloys

Description: Monolithic composites are needed that combine low friction and wear, high mechanical hardness, and high fracture toughness. Thin films and coatings are often unable to meet this engineering challenge as they can delaminate and fracture during operation ceasing to provide beneficial properties during service life. Two material systems were synthesized by spark plasma sintering (SPS) and were studied for their ability to meet these criteria. A dual hybrid composite was fabricated and consisted of… more
Date: December 2013
Creator: Kinkenon, Douglas
Item Type: Refine your search to only Thesis or Dissertation
open access

Tribological Improvements of Carbon-Carbon Composites by Infiltration of Atomic Layer Deposited Lubricious Nanostructured Ceramic Oxides

Description: A number of investigators have reported enhancement in oxidation and wear resistant of carbon-carbon composites (CCC) in the presence of protective coating layers. However, application of a surface and subsurface coating system that can preserve its oxidation and wear resistance along with maintaining lubricity at high temperature remains unsolved. To this end, thermodynamically stable protective oxides (ZnO/Al2O3/ZrO2) have been deposited by atomic layer deposition (ALD) to infiltrate porous … more
Date: August 2011
Creator: Mohseni, Hamidreza
Item Type: Refine your search to only Thesis or Dissertation
open access

Ultrasonic Processing of Aluminum 2139 and 7050

Description: Acoustics is the study of all sound waves, with ultrasound classified as those frequencies above 20,000 Hz. Currently, ultrasound is being used in many industries for a variety of purposes such as ultrasonic imaging, ultrasonic assisted friction stir welding, and ultrasonic spot welding. Despite these uses, the effects of ultrasound on phase stability and resultant mechanical properties has been minimally analyzed. Here we study the impact waves play in ultrasonic welding and design an appar… more
Date: August 2018
Creator: Reed, Jordan Derek
Item Type: Refine your search to only Thesis or Dissertation

Understanding the Micromechanism of Cyclic Loading Behavior of Ultrafine Grained Alloys

Description: In the current study, we have investigated the cyclic loading behavior of conventional as well as novel alloy system exhibiting fine and ultrafine-grained structure. While in case of conventional alloy systems (here aluminum alloy AA5024), the effect of three different grain sizes was investigated. Improvement in fatigue properties was observed with decreasing grain size. The unique microstructure produced via Friction stir processing was responsible for the improved fatigue response. Additiona… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: August 2019
Creator: Shukla, Shivakant
Item Type: Refine your search to only Thesis or Dissertation
open access

Void Growth and Collapse in a Creeping Single Crystal

Description: Aircraft engine components can be subjected to a large number of thermo-mechanical loading cycles and to long dwell times at high temperatures. In particular, the understanding of creep in single crystal superalloy turbine blades is of importance for designing more reliable and fuel efficient aircraft engines. Creep tests on single crystal superalloy specimens have shown greater creep strain rates for thinner specimens than predicted by current theories. Therefore, it is necessary to develop a … more
Date: August 2011
Creator: Srivastava, Ankit
Item Type: Refine your search to only Thesis or Dissertation
open access

Workfunction tuning of AZO Films Through Surface Modification for Anode Application in OLEDs.

Description: Widespread use of organic light emitting diodes (OLEDs) in solid state lighting and display technologies require efficiency and lifetime improvements, as well as cost reductions, inclusive of the transparent conducting oxide (TCO). Indium tin oxide (ITO) is the standard TCO anode in OLEDs, but indium is expensive and the Earth's reserve of this element is limited. Zinc oxide (ZnO) and its variants such as aluminum-doped ZnO (AZO) exhibit comparable electrical conductivity and transmissivity to … more
Date: August 2016
Creator: Jha, Jitendra
Item Type: Refine your search to only Thesis or Dissertation
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