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Platinum Group Thiophenoxyimine Complexes: Syntheses,Crystallographic and Computational Studies of Structural Properties

Description: Monomeric thiosalicylaldiminate complexes of rhodium(I) and iridium(I) were prepared by ligand transfer from the homoleptic zinc(II) species. In the presence of strongly donating ligands, the iridium complexes undergo insertion of the metal into the imine carbon-hydrogen bond. Thiophenoxyketimines were prepared by non-templated reaction of o-mercaptoacetophenone with anilines, and were complexed with rhodium(I), iridium(I), nickel(II) and platinum(II). X-ray crystallographic studies showed that while the thiosalicylaldiminate complexes display planar ligand conformations, those of the thiophenoxyketiminates are strongly distorted. Results of a computational study were consistent with a steric-strain interpretation of the difference in preferred ligand geometries.
Date: October 3, 2006
Creator: Krinsky, Jamin L.; Arnold, John & Bergman, Robert G.
Partner: UNT Libraries Government Documents Department

The Radiochemistry of Iridium

Description: The general and analytical chemistry of Ir are reviewed and applications to the radiochemistry of Ir are discussed. Topics covered include dissolution of samples containing Ir, counting techniques for radioactive Ir isotopes, radiochemical procedures for Ir radionuclides, and safety practices. A list is included of the radioactive nuclides of Ir. 106 references. (C.H.)
Date: October 1961
Creator: Leddicotte, G. W.
Partner: UNT Libraries Government Documents Department

Iridium-192 Production for Cancer Treatment

Description: The purpose of this work is to settle a laboratory for Iridium -192 sources production, that is, to determine a wire activation method and to build a hot cell for the wires manipulation, quality control and packaging. The paper relates, mainly, the wire activation method and its quality control. The wire activation is carried out in our nuclear reactor, IEA- R1m.
Date: October 5, 2004
Creator: Rostelato, M.E.C.M.; Silva, C.P.G.; Rela, P.R.; Zeituni, C.A.; Lepki, V. & Feher, A.
Partner: UNT Libraries Government Documents Department

Masses and proton separation energies obtained from Q{sub a} and Q{sub p} measurements.

Description: For many nuclei beyond the proton drip line in the Z>72, N>82 region, both proton and a emission are energetically allowed. In the case of some proton emitters, there are {alpha}-decay chains emanating from both parent and daughter nuclei. This means that if the mass excess of one member of an {alpha}-decay chain is known, then the mass excesses for all members of both chains can be obtained. In addition, proton separation energies may be derived for nuclei in the {alpha}-decay chain of the proton emitter. The method of time- and space-correlations also allows the identification of isomeric states in these nuclei. As an example, a large number of mass excesses and proton separation energies for ground and metastable states have been derived from Q{sub a} and Q{sub p} values obtained from the proton emitters {sup 165,166,167}Ir, {sup 171}Au, {sup 177}Tl, and their daughters.
Date: October 20, 2000
Creator: Davids, C. N.; Woods, P. J.; Batchelder, J. C.; Bingham, C. R.; Blumenthal, D. J.; Brown, L. T. et al.
Partner: UNT Libraries Government Documents Department

The correlation of indentation size effect experiments with pyramidal and spherical indenters.

Description: Experiments were conducted in annealed iridium using pyramidal and spherical indenters over a wide range of load. For a Berkovich pyramidal indenter, the hardness increased with decreasing depth of penetration. However, for spherical indenters, hardness increased with decreasing sphere radius. Based on the number of geometrically necessary dislocations generated during indentation, a theory that takes into account the work hardening differences between pyramidal and spherical indenters is developed to correlate the indentation size effects measured with the two indenters. The experimental results verify the theoretical correlation.
Date: January 1, 2001
Creator: Swadener, J. G. (John G.); George, Easo P. & Pharr, G.M.
Partner: UNT Libraries Government Documents Department

Work Function Study of Iridium Oxide and Molybdenum Using UPS and Simultaneous Fowler-Nordheim I-V Plots with Field Emission Energy Distributions

Description: The characterization of work functions and field emission stability for molybdenum and iridium oxide coatings was examined. Single emission tips and flat samples of molybdenum and iridium oxide were prepared for characterization. The flat samples were characterized using X-ray Photoelectron Spectroscopy and X-ray diffraction to determine elemental composition, chemical shift, and crystal structure. Flat coatings of iridium oxide were also scanned by Atomic Force Microscopy to examine topography. Work functions were characterized by Ultraviolet Photoelectron Spectroscopy from the flat samples and by Field Emission Electron Distributions from the field emission tips. Field emission characterization was conducted in a custom build analytical chamber capable of measuring Field Emission Electron Distribution and Fowler-Nordheim I-V plots simultaneously to independently evaluate geometric and work function changes. Scanning Electron Microscope pictures were taken of the emission tips before and after field emission characterization to confirm geometric changes. Measurement of emission stability and work functions were the emphasis of this research. In addition, use of iridium oxide coatings to enhance emission stability was evaluated. Molybdenum and iridium oxide, IrO2, were characterized and found to have a work function of 4.6 eV and 4.2 eV by both characterization techniques, with the molybdenum value in agreement with previous research. The analytic chamber used in the field emission analysis demonstrated the ability to independently determine the value and changes in work function and emitter geometry by simultaneous measurement of the Field Emission Energy Distribution and Fowler-Nordheim I-V plots from single emitters. Iridium oxide coating was found to enhance the stability of molybdenum emission tips with a relatively low work function of 4.2 eV and inhibited the formation of high work function molybdenum oxides. However, the method of deposition of iridium and annealing in oxygen to form iridium oxide on molybdenum emitters left rather severe cracking in the protective oxide ...
Date: August 1999
Creator: Bernhard, John Michael
Partner: UNT Libraries

Copper Electrodeposition on Iridium, Ruthenium and Its Conductive Oxide Substrate

Description: The aim of this thesis was to investigate the physical and electrochemical properties of sub monolayer and monolayer of copper deposition on the polycrystalline iridium, ruthenium and its conductive oxide. The electrochemical methods cyclic voltammetry (CV) and chronocoulometry were used to study the under potential deposition. The electrochemical methods to oxidize the ruthenium metal are presented, and the electrochemical properties of the oxide ruthenium are studied. The full range of CV is presented in this thesis, and the distances between the stripping bulk peak and stripping UPD peak in various concentration of CuSO4 on iridium, ruthenium and its conductive oxide are shown, which yields thermodynamic data on relative difference of bonding strength between Cu-Ru/Ir atoms and Cu-Cu atoms. The monolayer of UPD on ruthenium is about 0.5mL, and on oxidized ruthenium is around 0.9mL to 1.0mL. The conductive oxide ruthenium presents the similar properties of ruthenium metal. The pH effect of stripping bulk peak and stripping UPD peak of copper deposition on ruthenium and oxide ruthenium was investigated. The stripping UPD peak and stripping bulk peak disappeared after the pH ≥ 3 on oxidized ruthenium electrode, and a new peak appeared, which means the condition of pH is very important. The results show that the Cl- , SO42- , Br- will affect the position of stripping bulk peak and stripping UPD peak: the stripping bulk peak will shift and decrease if the concentration of halide ions is increasing, and the monolayer of UPD will increase at the same time.
Date: December 2003
Creator: Huang, Long
Partner: UNT Libraries

Interfacial Electrochemistry and Surface Characterization: Hydrogen Terminated Silicon, Electrolessly Deposited Palladium & Platinum on Pyrolyzed Photoresist Films and Electrodeposited Copper on Iridium

Description: Hydrogen terminated silicon surfaces play an important role in the integrated circuit (IC) industry. Ultra-pure water is extensively used for the cleaning and surface preparation of silicon surfaces. This work studies the effects of ultra-pure water on hydrogen passivated silicon surfaces in a short time frame of 120 minutes using fourier transform infrared spectroscopy – attenuated total reflection techniques. Varying conditions of ultra-pure water are used. This includes dissolved oxygen poor media after nitrogen bubbling and equilibration under nitrogen atmosphere, as well as metal contaminated solutions. Both microscopically rough and ideal monohydride terminated surfaces are examined. Hydrogen terminated silicon is also used as the sensing electrode for a potentiometric sensor for ultra-trace amounts of metal contaminants. Previous studies show the use of this potentiometric electrode sensor in hydrofluoric acid solution. This work is able to shows sensor function in ultra-pure water media without the need for further addition of hydrofluoric acid. This is considered a boon for the sensor due to the hazardous nature of hydrofluoric acid. Thin carbon films can be formed by spin coating photoresist onto silicon substrates and pyrolyzing at 1000 degrees C under reducing conditions. This work also shows that the electroless deposition of palladium and platinum may be accomplished in hydrofluoric acid solutions to attain palladium and platinum nanoparticles on a this film carbon surface for use as an electrode. Catalysis of these substrates is studied using hydrogen evolution in acidic media, cyclic voltammetry, and catalysis of formaldehyde. X-ray diffractometry (XRD) is used to ensure that there is little strain on palladium and platinum particles. Iridium is thought to be a prime candidate for investigation as a new generation copper diffusion barrier for the IC industry. Copper electrodeposition on iridium is studied to address the potential of iridium as a copper diffusion barrier. Copper electrodeposition ...
Date: December 2003
Creator: Chan, Raymond
Partner: UNT Libraries

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Description: A carbon-rich black layer, dating to ~;;12.9 ka, has been previously identified at ~;;50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ~;;12.9 ka, which we hypothesize caused abrupt environmentalchanges that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ~;;12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.
Date: March 13, 2007
Creator: Firestone, Richard B.; Firestone, R. B.; West, A.; Kennett, J. P.; Becker, L.; Bunch, T. E. et al.
Partner: UNT Libraries Government Documents Department

Rhenium and iridium

Description: Re is used together with Ir in a number of metallurgical applications. Ir has been used as coating for Re rocket thrusters and as an oxidation-resistant coating in a number of other applications. The high strength of Re at elevated temperature is combined with the oxidation resistance and high melting point of Ir. The use of the two metals together is advantageous due to absence of stable intermetallic compounds. Both Re and Ir alloying additions improve the ductility of W. The high solubility of Re in Ir is also taken advantage of to produce Ir-based alloys for structural applications. Uses of Re in conjunction with Ir are discussed.
Date: February 1, 1997
Creator: Ohriner, E.K.
Partner: UNT Libraries Government Documents Department

Rh-Based Mixed Alcohol Synthesis Catalysts: Characterization and Computational Report

Description: The U.S. Department of Energy is conducting a program focused on developing a process for the conversion of biomass to bio-based fuels and co-products. Biomass-derived syngas is converted thermochemically within a temperature range of 240 to 330°C and at elevated pressure (e.g., 1200 psig) over a catalyst. Ethanol is the desired reaction product, although other side compounds are produced, including C3 to C5 alcohols; higher (i.e., greater than C1) oxygenates such as methyl acetate, ethyl acetate, acetic acid and acetaldehyde; and higher hydrocarbon gases such as methane, ethane/ethene, propane/propene, etc. Saturated hydrocarbon gases (especially methane) are undesirable because they represent a diminished yield of carbon to the desired ethanol product and represent compounds that must be steam reformed at high energy cost to reproduce CO and H2. Ethanol produced by the thermochemical reaction of syngas could be separated and blended directly with gasoline to produce a liquid transportation fuel. Additionally, higher oxygenates and unsaturated hydrocarbon side products such as olefins also could be further processed to liquid fuels. The goal of the current project is the development of a Rh-based catalyst with high activity and selectivity to C2+ oxygenates. This report chronicles an effort to characterize numerous supports and catalysts to identify particular traits that could be correlated with the most active and/or selective catalysts. Carbon and silica supports and catalysts were analyzed. Generally, analyses provided guidance in the selection of acceptable catalyst supports. For example, supports with high surface areas due to a high number of micropores were generally found to be poor at producing oxygenates, possibly because of mass transfer limitations of the products formed out of the micropores. To probe fundamental aspects of the complicated reaction network of CO with H2, a computational/ theoretical investigation using quantum mechanical and ab initio molecular dynamics calculations was initiated in ...
Date: August 1, 2013
Creator: Albrecht, Karl O.; Glezakou, Vassiliki Alexandra; Rousseau, Roger J.; Engelhard, Mark H.; Varga, Tamas; Colby, Robert J. et al.
Partner: UNT Libraries Government Documents Department

Ignition Failure Mode Radiochemical Diagnostics Initial Assessment

Description: Radiochemical diagnostic signatures are well known to be effective indicators of nuclear ignition and burn reaction conditions. Nuclear activation is already a reliable technique to measure yield. More comprehensively, though, important quantities such as fuel areal density and ion temperature might be separately and more precisely monitored by a judicious choice of select nuclear reactions. This report details an initial assessment of this approach to diagnosing ignition failures on point-design cryogenic National Ignition Campaign targets. Using newly generated nuclear reaction cross section data for Scandium and Iridium, modest uniform doping of the innermost ablator region provides clearly observable reaction product differences between robust burn and failure for either element. Both equatorial and polar tracer loading yield observable, but indistinguishable, signatures for either choice of element for the preliminary cases studied.
Date: April 20, 2007
Creator: Fortner, R; Bernstein, L; Cerjan, C; Haan, S W; Harding, R; Hatchett, S et al.
Partner: UNT Libraries Government Documents Department

Strain hardening of fcc metal surfaces induced by microploughing

Description: Microploughing experiments were used as a method for better understanding the ploughing mechanism in gold and iridium single crystals. The plough depths ranged from 20 nm in iridium to 1,600 nm in gold. Yield stress profiles and TEM analyses indicate that both materials strain harden even when very small volumes of material are involved. Strain hardening theory, as applied to bulk material, is useful in analyzing the results.
Date: December 1, 1998
Creator: Day, R.D.; Dickerson, R.M. & Russell, P.E.
Partner: UNT Libraries Government Documents Department

Nuclear structure information derived from proton radioactivity measurements

Description: Proton decay presents an opportunity to obtain nuclear structure information for a nucleus situated beyond the proton drip line. This relatively rare decay mode is a quantum tunneling phenomenon where the decay rate is determined by a delicate interplay between the Coulomb and centrifugal terms of the nuclear potential. Ground-state proton emitters have been discovered for the odd-Z elements having Z = 51--55, 63, and 67--83. Recent results on proton radioactivity are described. Nuclear structure information such as spins, single particle orbital orderings, spectroscopic factors, and mass excesses have been obtained for a number of spherical proton emitters. New results on deformed proton emitters are discussed.
Date: October 1, 1997
Creator: Davids, C.N.
Partner: UNT Libraries Government Documents Department

Thermal contact resistance across a copper-silicon interface.

Description: An experimental setup to measure the thermal contact conductance across a silicon-copper (Si-Cu) interface is described, and the results obtained are presented. The resulting thermal contact resistance data are used in estimating the thermo-mechanical and optical performance of optical substrates cooled by interfaced copper cooling blocks. Several factors influence the heat transfer across solid interfaces. These include the material properties, interface pressure, flatness and roughness of the contacting surfaces, temperature, and interstitial material, if any. Results presented show the variation of thermal contact conductance as a function of applied interface pressure for a Cu-Si interface. Various interstitial materials investigated include iridium foil, silver foil and a liquid eutectic (Ga-In-Sn). As expected, thermal contact resistance decreases as interface pressure increases, except in the case of the eutectic, in which it was nearly constant. The softer the interstitial material, the lower the thermal contact resistance, Liquid metal provides the lowest thermal contact resistance across the Cu-Si interface, followed by the iridium foil, and then the silver foil.
Date: October 27, 1997
Creator: Khounsary, A.; Chojnowski, D.; Assoufid, L. & Worek, W.M.
Partner: UNT Libraries Government Documents Department

Using ytterbium-169 for safe and economical industrial radiography

Description: Safety has become an issue of paramount importance for industrial radiography. Many NDE facilities and suppliers are finding the cost of performing radiography Prohibitive due to heightened safety concerns for radiation area protection. The most common sources used in radiography, Iridium-192 and Cobalt-60, result in high radiation fields over a large area. Even when collimators are used large radiation fields can result from multicurie source radiography. Radiographic operations are being forced to find alternative test methods and techniques to the use of the old stand-by sources. These alternate methods are not always as comprehensive a test as full volumetric examination with radiography. Since Iridium and Cobalt are in such wide spread use, they are sometimes called upon to perform test of materials which are not in their optimum sensitivity range.
Date: January 1, 1994
Creator: Dowalo, J.A.
Partner: UNT Libraries Government Documents Department

Electrochemical Study of Under-Potential Deposition Processes on Transition Metal Surfaces

Description: Copper under-potential deposition (UPD) on iridium was studied due to important implications it presents to the semiconductor industry. Copper UPD allows controlled superfilling on sub-micrometer trenches; iridium has characteristics to prevent copper interconnect penetration into the surrounding dielectric. Copper UPD is not favored on iridium oxides but data shows copper over-potential deposition when lower oxidation state Ir oxide is formed. Effect of anions in solution on silver UPD at platinum (Pt) electrodes was studied with the electrochemical quartz crystal microbalance. Silver UPD forms about one monolayer in the three different electrolytes employed. When phosphoric acid is used, silver oxide growth is identified due to presence of low coverage hydrous oxide species at potentials prior to the monolayer oxide region oxide region.
Date: August 2006
Creator: Flores Araujo, Sarah Cecilia
Partner: UNT Libraries

High-field magnetization studies of U{sub 2}T{sub 2}Sn (T=Co, Ir, Pt) compounds

Description: High-field magnetization measurements at 4.2 K on U{sub 2}T{sub 2}Sn (T = Co, Ir and Pt) compounds have been performed on free and fixed powders up to 57 T. An antiferromagnetic ground state of U{sub 2}Pt{sub 2}Sn is corroborated by a metamagnetic transition at 22 T with very small hysteresis going up and down with field. U{sub 2}Co{sub 2}Sn and U{sub 2}Ir{sub 2}Sn show no metamagnetic transition up to 57 T which is in agreement with the non-magnetic ground state of these compounds. In all cases, the maximum applied field is not sufficient to achieve saturation. The short-pulse measurements presented here are compared with previous results obtained in quasi-static fields up to 35 T.
Date: July 1, 1995
Creator: Prokes, K.; Nakotte, H. & de Boer, F.R.
Partner: UNT Libraries Government Documents Department

Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

Description: Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.
Date: November 27, 2004
Creator: Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N. & Bergman, Robert G.
Partner: UNT Libraries Government Documents Department

On-line nuclear orientation. Progress report, April 1, 1992--December 31, 1993

Description: This report describes progress made during the extended final year (April 1, 1992 to December 31, 1993) and summarizes the accomplishments of the entire three-year period (April 1, 1990 through December 31, 1993) of the current US Department of Energy grant DE-FG06-87ER40345. This work is carried out primarily at the UNISOR (University Isotope Separator at Oak Ridge) facility of the Holifield Heavy-Ion Research Facility of the Oak Ridge National Laboratory. The primary mission of this work is the study of the structure and properties of nuclei far from stability through on-line nuclear orientation using the UNISOR Nuclear Orientation Facility, a helium dilution refrigerator coupled on-line to the UNISOR mass separator. The author`s group was one of the original proposers of this facility and played a central role in its design, construction, and development. The structure of nuclei far from stability is in general poorly known. Knowledge from heavy-ion reactions is generally limited to states on or near the yrast line, and thus a great deal of the low-energy structure, especially that at low spin, is often missed in such studies. The large beta-decay energies, on the other hand, result in the population of a multitude of states which often give a reasonably complete picture of the complex structure of these nuclei. The goal of this work is to use the nuclear orientation facility in conjunction with other UNISOR capabilities to examine and to understand the structure of these nuclei.
Date: December 31, 1993
Creator: Krane, K. S.
Partner: UNT Libraries Government Documents Department

High Strain Rate Tensile Testing of DOP-26 Iridium

Description: The iridium alloy DOP-26 was developed through the Radioisotope Power Systems Program in the Office of Nuclear Energy of the Department of Energy. It is used for clad vent set cups containing radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for spacecraft. This report describes mechanical testing results for DOP-26. Specimens were given a vacuum recrystallization anneal of 1 hour at 1375 C and tested in tension in orientations parallel and perpendicular to the rolling direction of the sheet from which they were fabricated. The tests were performed at temperatures ranging from room temperature to 1090 C and strain rates ranging from 1 x 10{sup -3} to 50 s{sup -1}. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1 x 10{sup -4} Torr. The yield stress (YS) and the ultimate tensile stress (UTS) decreased with increasing temperature and increased with increasing strain rate. Between 600 and 1090 C, the ductility showed a slight increase with increasing temperature. Within the scatter of the data, the ductility did not depend on the strain rate. The reduction in area (RA), on the other hand, decreased with increasing strain rate. The YS and UTS values did not differ significantly for the longitudinal and transverse specimens. The ductility and RA values of the transverse specimens were marginally lower than those of the longitudinal specimens.
Date: November 1, 2007
Creator: Schneibel, Joachim H; Carmichael Jr, Cecil Albert & George, Easo P
Partner: UNT Libraries Government Documents Department