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First Principle Calculations of the Structure and Electronic Properties of Pentacene Based Organic and ZnO Based Inorganic Semiconducting Materials

Description: In this thesis, I utilize first principles density functional theory (DFT) based calculations to investigate the structure and electronic properties including charge transfer behaviors and work function of two types of materials: pentacene based organic semiconductors and ZnO transparent conducting oxides, with an aim to search for high mobility n-type organic semiconductors and fine tuning work functions of ZnO through surface modifications. Based on DFT calculations of numerous structure comb… more
Date: May 2012
Creator: Li, Yun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

Description: Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution… more
Date: January 14, 2012
Creator: Liaw, Peter K.; Fine, Morris E.; Ghosh, Gautam; Asta, Mark D.; Liu, Chain T.; Sun, Zhiqian et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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High Temperature coatings based on {beta}-NiAI

Description: High temperature alloys are reviewed, focusing on current superalloys and their coatings. The synthesis, characerization, and oxidation performance of a NiAl–TiB{sub 2} composite are explained. A novel coating process for Mo–Ni–Al alloys for improved oxidation performance is examined. The cyclic oxidation performance of coated and uncoated Mo–Ni–Al alloys is discussed.
Date: July 10, 2012
Creator: Severs, Kevin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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IRON-PHOSPHATE GLASS FOR IMMOBILIZATION OF RADIOACTIVE TECHNETIUM

Description: Technetium-99 (Tc-99) can bring a serious environmental threat because of its high fission yield, long half-life, and high solubility and mobility in the ground water. The present work investigated the immobilization of Tc-99 (surrogated by Re) by heat-treating mixtures of an iron-phosphate glass with 1.5 to 6 wt.% KReO{sub 4} at {approx}1000 C. The Re retention in the glass was as high as {approx}1.2 wt. % while the loss of Re by evaporation during melting was {approx}50%. Re was uniformly dis… more
Date: March 19, 2012
Creator: AA, KRUGER; PR, HRMA; K, XU; J, CHOI; W, UM & J, HEO
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Grain boundary characterization in an X750 alloy

Description: Grain boundary chemistry in an X750 Ni alloy was analyzed by atom probe tomography in an effort to clarify the possible roles of elemental segregation and carbide presence on the stress corrosion cracking behavior of Ni alloys. Two types of cracks are observed: straight cracks along twin boundaries and wavy cracks at general boundaries. It was found that carbides (M23C6 and TiC) are present at both twin and general boundaries, with comparable B and P segregation for all types of grain boundarie… more
Date: November 1, 2012
Creator: Fisher, Kevin; Teysseyre, Sebastien & Marquis, Emmanuelle
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

Description: Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to… more
Date: May 1, 2012
Creator: Hurley, David; Reese, Stephen; Farzbod, Farhad & Kennedy, Rory
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Femtosecond Single-Shot Imaging of Nanoscale Ferromagnetic Order in Co/Pd Multilayers using Resonant X-ray Holography

Description: We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25 mJ/cm{sup 2}. Employing resonant spatially-muliplexed x-ray holography results in a low imaging threshold of 5 mJ/cm{sup 2}. Our results open new ways to combine ultrafast laser spe… more
Date: May 15, 2012
Creator: Wang, Tianhan; Zhu, Diling; Benny Wu,; Graves, Catherine; Schaffert, Stefan; Rander, Torbjorn et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Dft Study Revises Interstitial Configurations in Hcp Zr

Description: Analysis of experimental result on microstructure evolution in irradiated Zr and alloys has demonstrated that available knowledge on self-interstitial defects in Zr is in contradiction. We therefore have initiated an extensive theoretical and modeling program to clarify this issue. In this report we present first ab initio calculations results of single SIA configurations in Zr. We demonstrate importance of simulations cell size, applied exchange-correlation functional and simulated c/a ratio. … more
Date: June 1, 2012
Creator: Samolyuk, German D.; Golubov, Stanislav I.; Osetskiy, Yury N. & Stoller, Roger E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Analysis of ultra-narrow ferromagnetic domain walls

Description: New materials with high magnetic anisotropy will have domains separated by ultra-narrow ferromagnetic walls with widths on the order of a few unit cells, approaching the limit where the elastic continuum approximation often used in micromagnetic simulations is accurate. The limits of this approximation are explored, and the static and dynamic interactions with intrinsic crystalline defects and external driving #12;elds are modeled. The results developed here will be important when considering t… more
Date: January 10, 2012
Creator: Jenkins, Catherine & Paul, David
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Ultrafast Photovoltaic Response in Ferroelectric Nanolayers

Description: We show that light drives large-amplitude structural changes in thin films of the prototypical ferroelectric PbTiO3 via direct coupling to its intrinsic photovoltaic response. Using time-resolved x-ray scattering to visualize atomic displacements on femtosecond timescales, photoinduced changes in the unit-cell tetragonality are observed. These are driven by the motion of photogenerated free charges within the ferroelectric and can be simply explained by a model including both shift and screenin… more
Date: February 15, 2012
Creator: Daranciang, Dan
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Final Technical Report: Grain Boundary Complexions and Transitions in Doped Silicon

Description: This four-year research project has advanced the fundamental knowledge of grain boundary (GB) complexions (i.e., "two-dimensional interfacial phases") and associated GB "phase" transitions in several grounds. First, a bilayer interfacial phase, which had been directly observed by microscopy only in complex ceramic systems in prior studies, has been identified in simpler systems such as Au-doped Si and Bi-doped Ni in this study, where the interpretations of the their formation mechanisms and mic… more
Date: October 15, 2012
Creator: Luo, Jian
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

AB INITIO STUDY OF ADVANCED METALLIC NUCLEAR FUELS FOR FAST BREEDER REACTORS

Description: Density-functional formalism is applied to study the ground state properties of {gamma}-U-Zr and {gamma}-U-Mo solid solutions. Calculated heats of formation are compared with CALPHAD assessments. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components. The decomposition curves for {gamma}-based U-Zr and U-Mo solid solutions are derived from Ising-type Monte Carlo simulations. We explore the idea of stabilization of the {delta}-UZr{sub… more
Date: April 23, 2012
Creator: Landa, A; Soderlind, P; Grabowski, B; Turchi, P A; Ruban, A V & Vitos, L
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Modified Magnetic Ground State in Nimn (2) O (4) Thin Films

Description: The authors demonstrate the stabilization of a magnetic ground state in epitaxial NiMn{sub 2}O{sub 4} (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and e… more
Date: August 23, 2012
Creator: Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Iwata, J. M.; Toney, M. F.; Arenholz, E. & Suzuki, Y.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Nano-mechanics of Tunable Adhesion using Non Covalent Forces

Description: The objective of this program was to examine, via experiment and atomistic and continuum analysis, coordinated noncovalent bonding over a range of length scales with a view to obtaining modulated, patterned and reversible bonding at the molecular level. The first step in this project was to develop processes for depositing self-assembled monolayers (SAMs) bearing carboxylic acid and amine moieties on Si (111) surfaces and probe tips of an interfacial force microscope (IFM). This allowed the adh… more
Date: September 8, 2012
Creator: Liechti, Kenneth
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

On the origin of radiation growth of hcp crystals

Description: The aim of the present work is to study theoretically the radiation growth (RG) of hcp-type materials with a particular focus on the effect of one-dimensionally (1-D) migrating clusters of self-interstitial atoms (SIAs), which are steadily produced in displacement cascades under neutron or heavy-ion irradiation. A reaction-diffusion model is developed for the description of RG in single hcp-type metallic crystals. The model reproduces all RG stages observed in neutron-irradiated annealed sample… more
Date: March 1, 2012
Creator: Golubov, Stanislav I.; Barashev, Aleksandr & Stoller, Roger E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Scalable assembly of patterned ordered functional micelle arrays : final LDRD report.

Description: No Description Available.
Date: September 1, 2012
Creator: Fan, Hongyou; Sun, Zaicheng (University of New Mexico, Albuquerque, NM); Bai, Feng (University of New Mexico, Albuquerque, NM); Ta, Anh (University of New Mexico, Albuquerque, NM); Haddad, Raid Edward (University of New Mexico, Albuquerque, NM); Boye, Daniel M. (Davidson College, Davidson, NC) et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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[Commencement Program for University of North Texas, December 14-15, 2012]

Description: Commencement program for the fall 2012 graduating class of the University of North Texas, held in the UNT Coliseum on Friday and Saturday, December 14-15, 2012. The program contains the order of service and a list of graduates for the baccalaureate, master's, doctoral degrees.
Date: 2012-12-14/2012-12-15
Creator: University of North Texas
Item Type: Refine your search to only Pamphlet
Partner: UNT Libraries Special Collections
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Scientific/Technical Report

Description: This symposium aimed to bring together researchers working on quantifying nanoscale carrier transport processes in excitonic solar cells. Excitonic solar cells, including all-organic, hybrid organic-inorganic and dye-sensitized solar cells (DSSCs), offer strong potential for inexpensive and large-area solar energy conversion. Unlike traditional inorganic semiconductor solar cells, where all the charge generation and collection processes are well understood, these excitonic solar cells contain e… more
Date: November 21, 2012
Creator: Bommissetty, Venkat
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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