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Growth, preparation, and dielectric properties of monodomain single crystal PbTiO sub 3

Description: A method is described for obtaining monodomain PbTiO{sub 3} single crystals with high electrical resistivity (10{sup 10}{Omega} cm) and low dielectric frequency dispersion. The single crystals of PbTiO{sub 3} were grown by flux solution method. Space charge related defects, which result in the large dielectric frequency dispersion, were eliminated by heat treatments. 90{degrees} domains were removed by applying a unidirectional compressive stress along the <100> crystallographic direction. The … more
Date: May 1, 1992
Creator: Li, Z.; Xu, X. Z.; Dai, X. H.; Lam, D. J. & Chan, S. K.
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Partner: UNT Libraries Government Documents Department
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A design of experiment study of plasma sprayed alumina-titania coatings

Description: An experimental study of the plasma spraying of alumina-titania powder is presented in this paper. This powder system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Coating experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and t… more
Date: January 1, 1992
Creator: Steeper, T. J. (Du Pont de Nemours (E.I.) and Co., Aiken, SC (United States). Savannah River Lab.); Varacalle, D. J. Jr.; Wilson, G. C. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Riggs, W. L. II (Tubal Cain Co., Loveland, OH (United States)); Rotolico, A. J. & Nerz, J. E. (Metco/Perkin-Elmer, Westbury, NY (United States))
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Partner: UNT Libraries Government Documents Department
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NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts

Description: The primary objective of the project is to examine the relations between the catalytic and magnetic properties of the copper-cobalt higher alcohol synthesis catalysts. We have undertaken to investigate the magnetic character by studying the Nuclear Quadrupole resonance of copper and (Zerofield) Nuclear Magnetic Resonance of cobalt in copper cobalt catalysts.
Date: December 17, 1991
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Nonlinear optical properties of new KTiOPO sub 4 isostructures

Description: The atomic structures of the nonlinear optical materials potassium titanyl phosphate (KTiOPO{sub 4}, or KTP) and potassium titanyl arsenate (KTiOAsO{sub 4}) feature one-dimensional channels through which the potassium ions are relatively free to migrate. Ion exchange results when these materials are immersed in molten salts containing alkali metal ions. Sodium, lithium and silver all exchange readily for K{sup +} single crystals of both KTP and KTA to yield the exchanged derivatives Na{sub .95}… more
Date: January 1, 1991
Creator: Phillips, M. L. F.; Harrison, W. T. A. & Stucky, G. D.
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Partner: UNT Libraries Government Documents Department
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NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts

Description: The primary objective of the project is to examine the relations between the catalytic and magnetic properties of the copper-cobalt higher alcohol synthesis catalysts. We have undertaken to investigate the magnetic character by studying the Nuclear Quadrupole resonance of copper and (Zerofield) Nuclear Magnetic Resonance of cobalt in copper cobalt catalysts.
Date: January 14, 1992
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Corrosion of SiC and oxide-composite ceramics by a simulated steam-reformer atmosphere

Description: To achieve higher process efficiency by using pressurized reactants and/or heat transfer fluids, the US DOE is promoting development of high-pressure heat exchanger systems under cost-sharing agreements with industrial contractors. The steam reformer would contain more than 600 tubes. Because the combination of high temperature and pressure differential of 12.7 kg/cm{sup 2} (180 psig) across the tube wall is too severe for metallic tubes, ceramic materials are being considered for reformer tube… more
Date: September 1, 1991
Creator: Federer, J.I.; Kim, H.E. & Moorhead, A.J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Structure and dynamics in low-dimensional guest-host systems

Description: New synthetic materials continue to be discovered at a rapid rate. Many of these can be broadly described as guest-host systems, in the sense that a range of compositions is accessible by selectively inserting heteroatoms or molecules into the interstitial sites in an otherwise pure starting material. The premier examples are layer intercalates (graphite, transition metal di- and trichalocogenides, silicate clays) and doped polymers (notably polyacetylene). With a somewhat broader definition of… more
Date: April 1, 1992
Creator: Fischer, J.E. (Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science)
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Photoassisted oxidation of oil films on water

Description: The objective of the project is to develop TiO{sub 2}-based photocatalysts for the solar assisted oxidative dissolution of oil slicks. In a TiO{sub 2} crystal, absorption of a photon generates an electron-hole pair. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds, usually via an intermediate OH radical. Since the density of TiO{sub 2} (3.8g/cc for anatase, 4.3 g/cc for rutile) is greater than that of eithe… more
Date: August 1, 1991
Creator: Heller, A. & Brock, J. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Stress and phase transformation phenomena in oxide films

Description: In situ optical methods are reviewed for characterization of phase transformation processes and evaluation of residual stress in solution- deposited metastable oxide films. Such low density films most often are deposited as disordered phases making them prone to crystallization and attendant densification when subjected to increased temperature and/or applied pressure. Inherent stress imparted during film deposition and its evolution during the transformation are evaluated from phonon frequency… more
Date: April 1, 1992
Creator: Exarhos, G.J. & Hess, N.J.
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Partner: UNT Libraries Government Documents Department
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Oxide properties of a gamma titanium aluminide: A surface science study

Description: The surface properties of oxides grown on a gamma titanium aluminide (2 at. % Nb) have been examined using a x-ray photoelectron spectroscopy (XPS) and secondary-ion mass spectroscopy (SIMS). An oxide formed on the sample during air exposure at room temperature was thermally destabilized in ultra-high vacuum. The heating largely decomposed the advanced Ti oxidation states to give a predominate +2 valence configuration at 600{degrees}C, while the Al oxide was somewhat enhanced for the same treat… more
Date: January 1, 1991
Creator: Taylor, T. N. & Paffett, M. T.
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Partner: UNT Libraries Government Documents Department
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NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts

Description: The primary objective of the project is to investigate the magnetic nature of the higher alcohol synthesis catalyst-Cu/Co supported on specific supports: chromia and titania with and without an alkali metal promoter, and examine the relations between catalytic and magnetic properties.
Date: September 14, 1990
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The search for low photodesorption coatings

Description: Low photo desorption (PSD) from surfaces of vacuum chambers increases the beam lifetime and reduces the cost of the pumping system of any storage ring. In compact rings where all radiated power ({approximately}10 kW) is incident on a few meters only, low PSD and good thermal conductivity of photon absorbers are of particular importance. An experimental chamber in which one meter long bars can be exposed to white photon beam with 500 eV critical energy has been built and installed on the U10B be… more
Date: January 1, 1990
Creator: Foerster, C.L. & Korn, G.
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Partner: UNT Libraries Government Documents Department
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First principles energetic calculations of sapphire (0001) and (1 1 02) surfaces

Description: Various crystallographic faces of sapphire, the undoped single crystal {alpha}-Al{sub 2}O{sub 3}, have been widely used as substrates fro depositing thin films of metals, semiconductors, and insulators for basic scientific studies and for microelectronic applications. Epitaxial TiO{sub 2} and VO{sub 2} thin films were successfully grown on (0001), (1102) and (1120) surfaces of sapphire substrates by the Metal Organic Chemical Vapor Deposition (MOCVD) technique in our experimental program. The p… more
Date: March 1, 1992
Creator: Guo, J.; Ellis, D.E. & Lam, D.J.
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Partner: UNT Libraries Government Documents Department
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Cluster assembly of hierarchical nanostructures

Description: In the past few years, atom clusters with diameters in the range of 2--20 nm of a variety of materials, including both metals and ceramics, have been synthesized by evaporation and condensation in high-purity gases and subsequently consolidated in situ under ultrahigh vacuum conditions to create nanophase materials. These new utlrafine-grained materials have properties that are often significantly different and considerably improved relative to those of their coarser-grained counterparts owing … more
Date: February 1, 1992
Creator: Siegel, R. W.
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Partner: UNT Libraries Government Documents Department
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Isotopic tracer studies of Fischer-Tropsch Synthesis over Ru/TiO sub 2 catalysts

Description: Fischer-Tropsch synthesis is a process in which CO and H{sub 2} react to give predominantly liquid hydrocarbons. The reaction can be considered a special type of polymerization in which the monomer is produced in situ, and chain growth occurs by a sequence of independently repeated additions of the monomer to the growing chain. A investigation has been conducted to study the CO hydrogenation reaction in order to better understand catalyst deactivation and the elementary surface processes involv… more
Date: January 1, 1992
Creator: Krishna, K.R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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The Effect of Chemical Additives on the Synthesis of Ethanol

Description: The objective of this research is to elucidate the role of various chemical additives on ethanol synthesis over Rh- and Ni-based catalysts. Chemical additives used for this study will include S, P, Ag, Cu, Mn, and Na which have different electronegativities. The effect of additives on the surface state of the catalysts, heat of adsorption of reactant molecules, reaction intermediates, reaction pathways, reaction kinetics, and product distributions is/will be investigated by a series of experime… more
Date: September 20, 1991
Creator: Chuang, S. S. C. & Balakos, M. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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NQR-NMR studies of higher alcohol synthesis Cu-Co catalysts

Description: During this period, we focused our attention in analyzing the magnetic nature of the extensively used trimetallic catalyst system Cu-Co-Cr for the production of higher alcohols. We believe that there could be some correspondence between the catalytic and magnetic behaviors of the transition metal catalyst systems. Both the morphology and metallic charge distribution of the particles are know to govern the catalytic as well as the magnetic properties of the system. Based on this concept, we have… more
Date: April 15, 1992
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Enhancing solar photocatalytic detoxification by adsorption of porphyrins onto TiO sub 2

Description: Titanium dioxide (TiO{sub 2}) is a known photocatalyst for solar detoxification of water containing organic contaminants including PCB's and dioxins. Unfortunately, the UV light used by the photocatalyst only comprises about 4% of the strong spectrum. Metalloporphyrins strongly absorb in the visible and near infrared region. Using visible light, we have investigated Ni(II) uroporphyrin (NiUroP), Sn(IV)Cl{sub 2} uroporphyrin (SnUroP) and Sn(IV)Cl{sub 2} tetrakis(p-carboxyphenyl) porphyrin (SnTCP… more
Date: January 1, 1991
Creator: Majumder, S. A.; Ondrias, M. R.; Prairie, M. R. & Shelnutt, J. A.
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Partner: UNT Libraries Government Documents Department
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Reinforcements for high temperature ceramics

Description: A method has been investigated and developed to grow TiB{sub 2} whiskers by the VLS mechanism. The reaction was carried out in a quartz tube 3 in. in diameter, 30 in. long at about 1150{degrees}C in the presence of a catalyst. The basic experimental parameters, a substrate, and a catalyst, for the growth of the whiskers have been defined. The whiskers produced have shown variable size and morphology depending on the experimental conditions, and location of the whiskers from the input port. The … more
Date: April 1, 1992
Creator: Kyriacou, C. I.; Sepulveda, J. L. & Watson, M. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Transient stress evolution and crystallization in laser-irradiated amorphous titania sol-gel films

Description: Amorphous TiO{sub 2} sol-gel films are irreversibly transformed to a crystalline anatase phase when heated to temperatures in excess of 575 K or subjected to intense pulsed or CW laser irradiation. The laser-induced transformation is initiated as a result of impurity absorption and subsequent heating, and results in densification and relative changes in compressive stress of the film. Isothermally annealed films exhibit a decrease in compressive stress as crystallization proceeds while an incre… more
Date: October 1, 1991
Creator: Exarhos, G.J.; Hess, N.J. (Pacific Northwest Lab., Richland, WA (United States)) & Wood, S. (Washington State Univ., Pullman, WA (United States). Dept. of Physics)
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Partner: UNT Libraries Government Documents Department
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The domain structure features of epitaxial PbTiO sub 3 thin films prepared by MOCVD

Description: Ferroelectric oxide thin films have attracted great interest in recent years because of their potential applications in numerous electro-optic, pyroelectric, acousto-optical, and nonvolatile memory devices, and a variety of methods such as sputtering, laser ablation, and MOCVD has been used for preparation of the films. Among these ferroelectric materials, the PbTiO{sub 3} thin film has been extensively studied because of its small dielectric constant, large spontaneous polarization, small coer… more
Date: March 1, 1992
Creator: Bai, G.R.; Chang, H.L.M.; Foster, C.M. & Lam, D.J.
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Partner: UNT Libraries Government Documents Department
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Rolling-contact and wear resistance of hard coatings on bearing-steel substrates

Description: Ever-increasing needs for high-performance ball- and roller-bearing components that can endure extreme applications have led to a growing interest in hard coatings for improved fatigue life and wear resistance. In particular, hard TiN and TiC coatings and, quite recently, diamond like carbon films have attracted much attention from manufacturers that produce bearing systems for both rolling- and sliding-contact applications. This paper presents an overview that highlights recent incremental pro… more
Date: February 1, 1992
Creator: Erdemir, A.
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Partner: UNT Libraries Government Documents Department
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Investigation of the processes controlling the flame generation of refractory materials

Description: The processes involved in the formation of mixed oxides powders were studied using the counterflow diffusion flame burner. Powders of different morphologies were obtained by varying the flame conditions (temperature, residence time) and the concentration ratio of the oxides precursors. In-situ particle size and number density were determined using dynamic light scattering and 90{degrees} light scattering. A thermophoretic sampling method and a larger scale powder collection device also was used… more
Date: January 1, 1992
Creator: Katz, J. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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