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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
Item Type: Refine your search to only Thesis or Dissertation
open access

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
Item Type: Refine your search to only Thesis or Dissertation
open access

Device Engineering for Enhanced Efficiency from Platinum(II) Phosphorescent OLEDs

Description: Phosphorescent organic light emitting diodes (PHOLEDs) based on efficient electrophosphorescent dopant, platinum(II)-pyridyltriazolate complex, bis[3,5-bis(2-pyridyl)-1,2,4-triazolato]platinum(II) (Pt(ptp)2) have been studied and improved with respect to power efficiency, external efficiency, chromacity and efficiency roll-off. By studying the electrical and optical behavior of the doped devices and functionality of the various constituent layers, devices with a maximum EQE of 20.8±0.2 % and p… more
Date: August 2010
Creator: Li, Minghang
Item Type: Refine your search to only Thesis or Dissertation
open access

Carrier Mobility, Charge Trapping Effects on the Efficiency of Heavily Doped Organic Light-Emitting Diodes, and EU(lll) Based Red OLEDs

Description: Transient electroluminescence (EL) was used to measure the onset of emission delay in OLEDs based on transition metal, phosphorescent bis[3,5-bis(2-pyridyl)-1,2,4-triazolato] platinum(ΙΙ) and rare earth, phosphorescent Eu(hfa)3 with 4'-(p-tolyl)-2,2":6',2" terpyridine (ttrpy) doped into 4,4'-bis(carbazol-9-yl) triphenylamine (CBP), from which the carrier mobility was determined. For the Pt(ptp)2 doped CBP films in OLEDs with the structure: ITO/NPB (40nm)/mcp (10nm)/65% Pt(ptp)2:CBP (2… more
Date: August 2010
Creator: Lin, Ming-Te
Item Type: Refine your search to only Thesis or Dissertation
open access

Bulk and Interfacial Effects on Density in Polymer Nanocomposites

Description: The barrier properties of polymers are a significant factor in determining the shelf or device lifetime in polymer packaging. Nanocomposites developed from the dispersion of nanometer thick platelets into a host polymer matrix have shown much promise. The magnitude of the benefit on permeability has been different depending on the polymer investigated or the degree of dispersion of the platelet in the polymer. In this dissertation, the effect of density changes in the bulk and at the polymer-pl… more
Date: May 2007
Creator: Sahu, Laxmi Kumari
Item Type: Refine your search to only Thesis or Dissertation
open access

Effects of Plasma, Temperature and Chemical Reactions on Porous Low Dielectric Films for Semiconductor Devices

Description: Low-dielectric (k) films are one of the performance drivers for continued scaling of integrated circuit devices. These films are needed in microelectronic device interconnects to lower power consumption and minimize cross talk between metal lines that "interconnect" transistors. Low-k materials currently in production for the 45 and 65 nm node are most often organosilicate glasses (OSG) with dielectric constants near 2.8 and nominal porosities of 8-10%. The next generation of low-k materials wi… more
Date: December 2010
Creator: Osei-Yiadom, Eric
Item Type: Refine your search to only Thesis or Dissertation
open access

Growth, Structure and Tribological Properties of Atomic Layer Deposited Lubricious Oxide Nanolaminates

Description: Friction and wear mitigation is typically accomplished by introducing a shear accommodating layer (e.g., a thin film of liquid) between surfaces in sliding and/or rolling contacts. When the operating conditions are beyond the liquid realm, attention turns to solid coatings. Solid lubricants have been widely used in governmental and industrial applications for mitigation of wear and friction (tribological properties). Conventional examples of solid lubricants are MoS2, WS2, h-BN, and graphite;… more
Date: December 2010
Creator: Mensah, Benedict Anyamesem
Item Type: Refine your search to only Thesis or Dissertation
open access

Processing and Characterization of Nickel-Carbon Base Metal Matrix Composites

Description: Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are attractive reinforcements for lightweight and high strength metal matrix composites due to their excellent mechanical and physical properties. The present work is an attempt towards investigating the effect of CNT and GNP reinforcements on the mechanical properties of nickel matrix composites. The CNT/Ni (dry milled) nanocomposites exhibiting a tensile yield strength of 350 MPa (about two times that of SPS processed monolithic nickel… more
Date: May 2014
Creator: Borkar, Tushar Murlidhar
Item Type: Refine your search to only Thesis or Dissertation
open access

Design Principle on Carbon Nanomaterials Electrocatalysts for Energy Storage and Conversion

Description: We are facing an energy crisis because of the limitation of the fossil fuel and the pollution caused by burning it. Clean energy technologies, such as fuel cells and metal-air batteries, are studied extensively because of this high efficiency and less pollution. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential in the process of energy storage and conversion, and noble metals (e.g. Pt) are needed to catalyze the critical chemical reactions in these devices. Funct… more
Date: May 2017
Creator: Zhao, Zhenghang
Item Type: Refine your search to only Thesis or Dissertation
open access

Exceptional Properties in Friction Stir Processed Beta Titanium Alloys and an Ultra High Strength Steel

Description: The penchant towards development of high performance materials for light weighting engineering systems through various thermomechanical processing routes has been soaring vigorously. Friction stir processing (FSP) - a relatively new thermomechanical processing route had shown an excellent promise towards microstructural modification in many Al and Mg alloy systems. Nevertheless, the expansion of this process to high temperature materials like titanium alloys and steels is restricted by the limi… more
Date: May 2017
Creator: Tungala, Vedavyas
Item Type: Refine your search to only Thesis or Dissertation
open access

Precession Electron Diffraction Assisted Characterization of Deformation in α and α+β Titanium Alloys

Description: Ultra-fine grained materials with sub-micrometer grain size exhibit superior mechanical properties when compared with conventional fine-grained material as well as coarse-grained materials. Severe plastic deformation (SPD) techniques have been shown to be an effective way to modify the microstructure in order to improve the mechanical properties of the material. Crystalline materials require dislocations to accommodate plastic strain gradients and maintain lattice continuity. The lattice curvat… more
Date: August 2015
Creator: Liu, Yue
Item Type: Refine your search to only Thesis or Dissertation
open access

First Principles Study of Metastable Beta Titanium Alloys

Description: The high temperature BCC phase (b) of titanium undergoes a martensitic transformation to HCP phase (a) upon cooling, but can be stabilized at room temperature by alloying with BCC transition metals such as Mo. There exists a metastable composition range within which the alloyed b phase separates into a + b upon equilibrium cooling but not when rapidly quenched. Compositional partitioning of the stabilizing element in as-quenched b microstructure creates nanoscale precipitates of a new simple he… more
Date: August 2015
Creator: Gupta, Niraj
Item Type: Refine your search to only Thesis or Dissertation
open access

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

Reactions and Interfacial Behaviors of the Water–Amorphous Silica System from Classical and Ab Initio Molecular Dynamics Simulations

Description: Due to the wide application of silica based systems ranging from microelectronics to nuclear waste disposal, detailed knowledge of water-silica interactions plays an important role in understanding fundamental processes, such as glass corrosion and the long term reliability of devices. In this dissertation, atomistic computer simulation methods have been used to explore and identify the mechanisms of water-silica reactions and the detailed processes that control the properties of the water-sili… more
Date: May 2016
Creator: Rimsza, Jessica M.
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

Influence of High Strain Rate Compression on Microstructure and Phase Transformation of NiTi Shape Memory Alloys

Description: Since NiTi shape memory alloy (SMA) was discovered in the early 1960s, great progress has been made in understanding the properties and mechanisms of NiTi SMA and in developing associated products. For several decades, most of the scientific research and industrial interests on NiTi SMA has focused on its superelastic applications in the biomedical field and shape memory based “smart” devices, which involves the low strain rate (around 0.001 s^-1) response of NiTi SMA. Due to either stress-indu… more
Date: May 2016
Creator: Qiu, Ying
Item Type: Refine your search to only Thesis or Dissertation
open access

Fatigue Behavior of A356 Aluminum Alloy

Description: Metal fatigue is a recurring problem for metallurgists and materials engineers, especially in structural applications. It has been responsible for many disastrous accidents and tragedies in history. Understanding the micro-mechanisms during cyclic deformation and combating fatigue failure has remained a grand challenge. Environmental effects, like temperature or a corrosive medium, further worsen and complicate the problem. Ultimate design against fatigue must come from a materials perspective … more
Date: May 2016
Creator: Nelaturu, Phalgun
Item Type: Refine your search to only Thesis or Dissertation
open access

In Vitro Behavior of AZ31B Mg-Hydroxyapatite Metallic Matrix Composite Surface Fabricated via Friction Stir Processing

Description: Magnesium and its alloys have been considered for load-bearing implant materials due to their similar mechanical properties to the natural bone, excellent biocompatibility, good bioactivity, and biodegradation. Nevertheless, the uncontrollable corrosion rate in biological environment restrains their application. Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a widely used bio-ceramic which has bone-like mineral structure for bone fixation. Poor fracture toughness of HA makes it not suitable for load-b… more
Date: August 2016
Creator: Ho, Yee Hsien
Item Type: Refine your search to only Thesis or Dissertation
open access

Defect Behaviors in Zinc Oxide and Zinc Titanates Ceramics from First Principles Computer Simulations

Description: ZnO and ZnO-TiO2 ceramics have intriguing electronic and mechanical properties and find applications in many fields. Many of these properties and applications rely on the understanding of defects and defect processes in these oxides as these defects control the electronic, catalytic and mechanical behaviors. The goal of this dissertation is to systematically study the defects and defects behaviors in Wurtzite ZnO and Ilmenite ZnTiO3 by using first principles calculations and classical simulatio… more
Date: December 2016
Creator: Sun, Wei
Item Type: Refine your search to only Thesis or Dissertation
open access

The Role of Misfit Strain and Oxygen Content on Formation and Evolution of Omega Precipitate in Metastable Beta-titanium Alloys

Description: β-Ti alloys are widely used in airframe and biomedical applications due to their high ductility, high hardenability, and low elastic modulus. The phase transformations in β-Ti alloys are rather complex due to formation of metastable phases during various thermo-mechanical treatments. One such critical metastable phase, the hexagonal omega (ω) phase, can form in β-Ti alloys under quenching from the high temperature β phase and/or isothermal aging at intermediate temperature. Despite a substantia… more
Date: December 2016
Creator: Hendrickson, Mandana
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
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Date: May 2019
Creator: Wang, Kai
Item Type: Refine your search to only Thesis or Dissertation

Bio-Inspired Material Surfaces with Self-cleaning, Micromanipulation and Water Collection

Description: Geckos are famous for the skill of switchable adhesion that they use to stick on various surface while keep their fingers super clean. In the dissertation, a unique mechanism was discovered to explain gecko self-cleaning phenomena. Using atomic force microscopy (AFM), we managed to compare the microparticle-substrate adhesion and the microparticle-seta adhesion with a single seta bonded to the AFM cantilever. A dynamic effect was approved that high pulling-off speed could increase the micropart… more
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Date: May 2019
Creator: Wan, Yiyang
Item Type: Refine your search to only Thesis or Dissertation
open access

Developing Precipitation Hardenable High Entropy Alloys

Description: High entropy alloys (HEAs) is a concept wherein alloys are constructed with five or more elements mixed in equal proportions; these are also known as multi-principle elements (MPEs) or complex concentrated alloys (CCAs). This PhD thesis dissertation presents research conducted to develop precipitation-hardenable high entropy alloys using a much-studied fcc-based equi-atomic quaternary alloy (CoCrFeNi). Minor additions of aluminium make the alloy amenable for precipitating ordered intermetallic … more
Date: August 2017
Creator: Gwalani, Bharat
Item Type: Refine your search to only Thesis or Dissertation
open access

Trapping of hydrogen in Hf-based high κ dielectric thin films for advanced CMOS applications.

Description: In recent years, advanced high κ gate dielectrics are under serious consideration to replace SiO2 and SiON in semiconductor industry. Hafnium-based dielectrics such as hafnium oxides, oxynitrides and Hf-based silicates/nitrided silicates are emerging as some of the most promising alternatives to SiO2/SiON gate dielectrics in complementary metal oxide semiconductor (CMOS) devices. Extensive efforts have been taken to understand the effects of hydrogen impurities in semiconductors and its behavi… more
Date: December 2007
Creator: Ukirde, Vaishali
Item Type: Refine your search to only Thesis or Dissertation
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