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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Amorphization and De-vitrification in Immiscible Copper-Niobium Alloy Thin Films

Description: While amorphous phases have been reported in immiscible alloy systems, there is still some controversy regarding the reason for the stabilization of these unusual amorphous phases. Direct evidence of nanoscale phase separation within the amorphous phase forming in immiscible Cu-Nb alloy thin films using 3D atom probe tomography has been presented. This evidence clearly indicates that the nanoscale phase separation is responsible for the stabilization of the amorphous phase in such immiscible sy… more
Date: May 2007
Creator: Puthucode Balakrishnan, Anantharamakrishnan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Surface Engineering and Characterization of Laser Deposited Metallic Biomaterials

Description: Novel net shaping technique Laser Engineered Net shaping™ (LENS) laser based manufacturing solution (Sandia Corp., Albuquerque, NM); Laser can be used to deposit orthopedic implant alloys. Ti-35Nb-7Zr-5Ta (TNZT) alloy system was deposited using LENS. The corrosion resistance being an important prerequisite was tested electrochemically and was found that the LENS deposited TNZT was better than conventionally used Ti-6Al-4V in 0.1N HCl and a simulated body solution. A detailed analysis of the cor… more
Date: May 2007
Creator: Samuel, Sonia
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Study of Gate Electrode Materials on High K Dielectrics

Description: This problem in lieu of thesis report presents a study on gate electrode materials on high K dielectrics, including poly-SiGe and Ru. The stability of poly-SiGe in direct contact with Hf silicon-oxynitride (HfSiON) is studied by rapid thermal annealing (RTA), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). By performing a series of RTA treatments we found that as RTA thermal budgets reach 1050 C f… more
Date: August 2003
Creator: Yao, Chun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

A Wet Etch Release Method for Silicon Microelectromechanical Systems (MEMS) Using Polystyrene Microspheres for Improved Yield

Description: One of the final steps in fabricating microelectromechanical devices often involves a liquid etch release process. Capillary forces during the liquid evaporation stage after the wet etch process can pull two surfaces together resulting in adhesion of suspended microstructures to the supporting substrate. This release related adhesion can greatly reduce yields. In this report, a wet etch release method that uses polystyrene microspheres in the final rinse liquid is investigated. The polystyrene … more
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Date: May 2004
Creator: Mantiziba, Fadziso
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Determination of Wear in Polymers Using Multiple Scratch Test.

Description: Wear is an important phenomenon that occurs in all the polymer applications in one form or the other. However, important links between materials properties and wear remain illusive. Thus optimization of material properties requires proper understanding of polymer properties. Studies to date have typically lacked systematic approach to all polymers and wear test developed are specific to some polymer classes. In this thesis, different classes of polymers are selected and an attempt is made to us… more
Date: August 2004
Creator: Damarla, Gowrisankar
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Topics in micro electromechanical systems: MEMS engineering and alternative materials for MEMS fabrication.

Description: This paper deals with various topics in micro electromechanical systems (MEMS) technology beginning with microactuation, MEMS processing, and MEMS design engineering. The fabrication and testing of three separate MEMS devices are described. The first two devices are a linear stepping motor and a continuous rotary motor, respectively; and were designed for the purpose of investigating the frictional and wear properties of silicon components. The third device is a bi-stable microrelay, in which e… more
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Date: August 2004
Creator: Chapla, Kevin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Development of a Novel Grease Resistant Functional Coatings for Paper-based Packaging and Assessment of Application by Flexographic Press

Description: Recent commercial developments have created a need for alternative materials and methods for imparting oil/grease resistance to paper and/or paperboard used in packaging. The performance of a novel grease resistant functional coating comprised of polyvinyl alcohol (PVA), sodium tetraborate pentahydrate (borate) and acetonedicarboxylic acid (ACDA) and the application of said coating by means of flexographic press is presented herein. Application criteria is developed, testing procedures describe… more
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Date: August 2004
Creator: Brown, Robert W.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Effect of Silyation on Organosilcate Glass Films

Description: Photoresist stripping with oxygen plasma ashing destroys the functional groups in organosilicate glass films and induce moisture uptake, causing low-k dielectric degradation. In this study, hexamethyldisilazane (HMDS), triethylchlorosilane and tripropylchlorosilane are used to repair the damage to organosilicate glass by the O2 plasma ashing process. The optimization of the surface functionalization of the organosilicate glass by the silanes and the thermal stability of the functionalized surfa… more
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Date: August 2004
Creator: Kadam, Poonam
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Saturation and foaming of thermoplastic nanocomposites using supercritical CO2.

Description: Polystyrene (PS) nanocomposite foams were prepared using supercritical fluid (SCF) CO2 as a solvent and blowing agent. PS was first in-situ polymerized with a range of concentrations of montmorillonite layered silicate (MLS). The polymerized samples were then compression molded into 1 to 2mm thick laminates. The laminates were foamed in a batch supercritical CO2 process at various temperatures and pressures from 60°-85°C and 7.6-12MPa. The resulting foams were analyzed by scanning electron micr… more
Date: May 2005
Creator: Strauss, William C.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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A magnetorheological study of single-walled and multi-walled carbon nanotube dispersions in mineral oil and epoxy resin.

Description: Single wall carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) were dispersed in mineral oil and epoxy resin. The magnetorheological properties of these dispersions were studied using a parallel plate rheometer. Strain sweeps, frequency sweeps, magneto sweeps and steady shear tests were conducted in various magnetic fields. G', G", h* and ty increased with increasing magnetic field, which was partially attributed to the increasing degree of the alignment of nanotubes in a strong… more
Date: May 2005
Creator: Yang, Zhengtao
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Morphological properties of poly (ethylene terephthalate) (PET) nanocomposites in relation to fracture toughness.

Description: The effect of incorporation of montmorillonite layered silicate (MLS) on poly (ethylene terephthalate) (PET) matrix was investigated. MLS was added in varying concentration of 1 to 5 weight percent in the PET matrix. DSC and polarized optical microscopy were used to determine the crystallization effects of MLS addition. Non isothermal crystallization kinetics showed that the melting temperature and crystallization temperature decrease as the MLS percent increases. This delayed crystallization a… more
Date: August 2005
Creator: Pendse, Siddhi
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

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
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Indentation induced deformation in metallic materials.

Description: Nanoindentation has brought in many features of research over the past decade. This novel technique is capable of producing insights into the small ranges of deformation. This special point has brought a lot of focus in understanding the deformation behavior under the indenter. Nickel, iron, tungsten and copper-niobium alloy system were considered for a surface deformation study. All the samples exhibited a spectrum of residual deformation. The change in behavior with indentation and the materi… more
Date: December 2005
Creator: Vadlakonda, Suman
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Micro and nano composites composed of a polymer matrix and a metal disperse phase.

Description: Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of… more
Date: December 2007
Creator: Olea Mejia, Oscar Fernando
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Supercritical CO2 foamed biodegradable polymer blends of polycaprolactone and Mater-Bi.

Description: Supercritical CO2 foam processing of biopolymers represents a green processing route to environmentally friendly media and packaging foams. Mater-Bi, a multiconstituent biopolymer of polyester, starch and vegetable oils has shown much promise for biodegradation. The polymer, however, is not foamable with CO2 so blended with another polymer which is. Polycaprolactone is a biopolymer with potential of 4000% change in volume with CO2. Thus we investigate blends of Mater-Bi (MB) and polycaprolacton… more
Date: December 2007
Creator: Ogunsona, Emmanuel Olusegun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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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

Supercritical Silylation and Stability of Silyl Groups

Description: Methylsilsesquioxane (MSQ) and organosilicate glass (OSG) are the materials under this study because they exhibit the dielectric constant values necessary for future IC technology requirements. Obtaining a low-k dielectric value is critical for the IC industry in order to cope time delay and cross talking issues. These materials exhibit attractive dielectric value, but there are problems replacing conventional SiO2, because of their chemical, mechanical and electrical instability after plasma p… more
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Date: May 2006
Creator: Nerusu, Pawan Kumar
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Partner: UNT Libraries
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Study of lead sorption on magnetite at high temperatures.

Description: Lead's uptake on magnetite has been quantitatively evaluated in the present study at a temperature of 200°C and pH of 8.5 with lead concentrations ranging from 5 ppm to175 ppm by equilibrium adsorption isotherms. The pH independent sorption behavior suggested lead sorption due to pH independent permanent charge through weak electrostatic, non-specific attraction where cations are sorbed on the cation exchange sites. The permanent negative charge could be a consequence of lead substitution which… more
Date: December 2006
Creator: Paliwal, Vaishali
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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