UNT Theses and Dissertations - 18 Matching Results

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Barrier and Long Term Creep Properties of Polymer Nanocomposites.

Description: The barrier properties and long term strength retention of polymers are of significant importance in a number of applications. Enhanced lifetime food packaging, substrates for OLED based flexible displays and long duration scientific balloons are among them. Higher material requirements in these applications drive the need for an accurate measurement system. Therefore, a new system was engineered with enhanced sensitivity and accuracy. Permeability of polymers is affected by permeant solubility… more
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Date: December 2004
Creator: Ranade, Ajit
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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
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Characterization and Mechanical Properties of Nanoscale Precipitates in Modified Al-Si-Cu Alloys Using Transmission Electron Microscopy and 3D Atom Probe Tomography.

Description: Among the commercial aluminum alloys, aluminum 319 (Al-7wt%Si-4wt%Cu) type alloys are popularly used in automobile engine parts. These alloys have good casting characteristics and excellent mechanical properties resulting from a suitable heat treatment. To get a high strength in the 319 type alloys, grain refining, reducing the porosity, solid solution hardening, and precipitation hardening are preferred. All experimental variables such as solidification condition, composition, and heat treatme… more
Date: May 2007
Creator: Hwang, Junyeon
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Definition of Brittleness: Connections Between Mechanical and Tribological Properties of Polymers.

Description: The increasing use of polymer-based materials (PBMs) across all types of industry has not been matched by sufficient improvements in understanding of polymer tribology: friction, wear, and lubrication. Further, viscoelasticity of PBMs complicates characterization of their behavior. Using data from micro-scratch testing, it was determined that viscoelastic recovery (healing) in sliding wear is independent of the indenter force within a defined range of load values. Strain hardening in sliding we… more
Date: August 2008
Creator: Hagg Lobland, Haley E.
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Formation and Quantification of Corrosion Deposits in the Power Industry

Description: The presence of deposits on the secondary side of pressurized water reactor (PWR) steam generator systems is one of the main contributors to the high maintenance costs of these generators. Formation and transport of corrosion products formed due to the presence of impurities, metals and metallic oxides in the secondary side of the steam generator units result in formation of deposits. This research deals with understanding the deposit formation and characterization of deposits by studying the s… more
Date: May 2007
Creator: Namduri, Haritha
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Functionalization and characterization of porous low-κ dielectrics.

Description: The incorporation of fluorine into SiO2 has been shown to reduce the dielectric constant of the existing materials by reducing the electrical polarizability. However, the incorporation of fluorine has also been shown to decrease film stability. Therefore, new efforts have been made to find different ways to further decrease the relative dielectric constant value of the existing low-k materials. One way to reduce the dielectric constant is by decreasing its density. This reduces the amount of p… more
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Date: May 2005
Creator: Orozco-Teran, Rosa Amelia
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Hydrophobic, fluorinated silica xerogel for low-k applications.

Description: A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species.… more
Date: May 2004
Creator: Zhang, Zhengping
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Long Term Property Prediction of Polyethylene Nanocomposites

Description: The amorphous fraction of semicrystalline polymers has long been thought to be a significant contributor to creep deformation. In polyethylene (PE) nanocomposites, the semicrystalline nature of the maleated PE compatibilizer leads to a limited ability to separate the role of the PE in the nanocomposite properties. This dissertation investigates blown films of linear low-density polyethylene (LLDPE) and its nanocomposites with montmorillonite-layered silicate (MLS). Addition of an amorphous ethy… more
Date: December 2008
Creator: Shaito, Ali Al-Abed
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Low Temperature Polymeric Precursor Derived Zinc Oxide Thin Films

Description: Zinc oxide (ZnO) is a versatile environmentally benign II-VI direct wide band gap semiconductor with several technologically plausible applications such as transparent conducting oxide in flat panel and flexible displays. Hence, ZnO thin films have to be processed below the glass transition temperatures of polymeric substrates used in flexible displays. ZnO thin films were synthesized via aqueous polymeric precursor process by different metallic salt routes using ethylene glycol, glycerol, citr… more
Date: December 2006
Creator: Choppali, Uma
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Measurement of Lattice Strain and Relaxation Effects in Strained Silicon Using X-ray Diffraction and Convergent Beam Electron Diffraction

Description: The semiconductor industry has decreased silicon-based device feature sizes dramatically over the last two decades for improved performance. However, current technology has approached the limit of achievable enhancement via this method. Therefore, other techniques, including introducing stress into the silicon structure, are being used to further advance device performance. While these methods produce successful results, there is not a proven reliable method for stress and strain measurements o… more
Date: August 2007
Creator: Diercks, David Robert
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Mechanical behavior and performance of injection molded semi-crystalline polymers.

Description: I have used computer simulations to investigate the behavior of polymeric materials at the molecular level. The simulations were performed using the molecular dynamics method with Lennard-Jones potentials defining the interactions between particles in the system. Significant effort was put into the creation of realistic materials on the computer. For this purpose, an algorithm was developed based on the step-wise polymerization process. The resulting computer-generated materials (CGMs) exhibit… more
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Date: August 2003
Creator: Simoes, Ricardo J. F.
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Processing, structure property relationships in polymer layer double hydroxide multifunctional nanocomposites

Description: Dan Beaty (1937-2002) was a prolific composer, pianist, researcher, educator, and writer. His large compositional output included chamber works, choral works, songs, orchestral pieces, electronic music, and keyboard works. Beaty was well versed in traditional Western music as well as the more avant-garde and perplexing idioms of the twentieth century. Beaty's compositions reflect the many fascinating, if not always popular, musical trends of his time. His music encompasses styles from serial … more
Date: August 2009
Creator: Ogbomo, Sunny Minister
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Stimuli-responsive microgels for self-assembled crystalline structures and controlled drug release.

Description: Tissue response to PNIPAM and HPC nanoparticles has been studied by implantation method. The results suggest that both PNIAPM and HPC nanoparticles possess good biocompatibility and they may serve as a good carrier for the applications of controlled delivery. Rheological properties of dispersions of IPN microgels composed of PNIPAM and PAAc have been studied. It is found that the IPN microgel dispersion can undergo a sol-gel transition at temperature above 33°C. In vivo drug release experiments… more
Date: August 2009
Creator: Zhou, Jun
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Structure and Low-temperature Tribology of Lubricious Nanocrystalline ZnO/Al2O3 Nanolaminates and ZrO2 Monofilms Grown by Atomic Layer Deposition

Description: Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures,… more
Date: December 2008
Creator: Romanes, Maia Castillo
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Synthesis and Characterization of Crystalline Assemblies of Functionalized Hydrogel Nanoparticles

Description: Two series monodispersed nanoparticles of hydroxylpropyl cellulose (HPC) and functionalized poly-N-isopropylamide (PNIPAM) particles have been synthesized and used as building blocks for creating three-dimensional networks, with two levels of structural hierarchy. The first level is HPC nanoparticles were made from methacrylated or degradable cross-linker attached HPC. These nanoparticles could be stabilized at room temperature by residual methacrylate or degradable groups are present both with… more
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Date: December 2005
Creator: Cai, Tong
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Synthesis and characterization of crystalline assembly of poly Nisopropylacry-lamide)-co-acrylic acid nanoparticles.

Description: In this study, crystalline poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAm-co-AAc) nanoparticle network in organic solvents was obtained by self assembling precursor particles in acetone/epichlorohydrin mixture at room temperature followed by inter-sphere crosslinking at ~98 °C. The crystals thus formed can endure solvent exchanges or large distortions under a temporary compressing force with the reoccurrence of crystalline structures. In acetone, the crystals were stable, independent of te… more
Date: December 2004
Creator: Zhou, Bo
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Thermophysical, Interfacial and Decomposition Analyses of Polyhydroxyalkanoates introduced against Organic and Inorganic Surfaces

Description: The development of a "cradle-to-cradle" mindset with both material performance during utilization and end of life disposal is a critical need for both ecological and economic considerations. The main limitation to the use of the biopolymers is their mechanical properties. Reinforcements are therefore a good alternative but disposal concerns then arise. Thus the objective of this dissertation is to investigate a biopolymer nanocomposite where the filler is a synthetically prepared layer double h… more
Date: December 2009
Creator: Dagnon, Koffi Leonard
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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
Partner: UNT Libraries
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