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High Temperature Enthalpies of the Lead Halides: Enthalpies and Entropies of Fusion

Description: The objectives of this investigation were: 1. To establish calorimetrically the transition temperature for the orthorhombic to cubic transition exhibited by PbF₂ and to determine the enthalpy of this transition. 2. To determine if the solid-solid phase transitions claimed in the literature for PbCl₂, PbF₂, PbBr₂, and PbI₂ were of thermodynamic importance, and if so, to determine the enthalpies of transition. 3. To determine if the discontinuous thermal expansions reported by Hsu for the lead halides were of thermodynamic importance. 4. To obtain reliable heat content data for the lead halides in both the solid and liquid states.
Date: June 1970
Creator: Linsey, Clarence W.
Partner: UNT Libraries

Thermodynamic Properties of Halides

Description: From Introduction: "This compilation is the second in a series revising and expanding Bureau of Mines Bulletin 605, "Thermodynamic Properties of 65 Elements-Their Oxides, Halides, Carbides, and Nitrides," by C. E. Wicks and F. E. Block, published in 1963, and including data available through 1959."
Date: unknown
Creator: Pankratz, L. B.
Partner: UNT Libraries Government Documents Department

Preparation of Ductile Zirconium: Summary of Thermodynamic Data

Description: Abstract: A summary of thermodynamic calculations for zirconium halides is given. Data indicates that the iodide is the most promising of the halides for arc dissociation and that good recoveries of zirconium should be obtainable provided dissociation is carried out at reduced pressure.
Date: September 16, 1949
Creator: Findlay, G. R.
Partner: UNT Libraries Government Documents Department

The Preparation and Properties of Some Mixed Uranium Halides

Description: From abstract: "Compounds of tetravalent uranium containing two halogens have been prepared. Six combinations of the four halogens are possible, and at least one compound of each group was made. X-ray diffraction patterns were made in most cases and cooling curves of melts were made for the bromachlorides. The two general methods of preparation used were (a) reaction of a uranium trihalide with a halogen of greater atomic weight and (b) interaction of two tetrahalides."
Date: 1948
Creator: Warf, James C. & Baenziger, Norman C.
Partner: UNT Libraries Government Documents Department

Theoretical Consideration of the Geometrical Structure of the Uranium Halides

Description: Abstract: The geometrical structure of the uranium halides has been studied from a theoretical viewpoint. This theoretical consideration tends to indicate that the pentavalent uranium halides are geometrically but not energetically capable of existence except as double halide compounds of hexavalent and tetravalent uranium.
Date: December 2, 1946
Creator: Calkins, Vincent P.
Partner: UNT Libraries Government Documents Department

BEAM EXPOSURE DEPENDENCE AND MECHANISMS OF PHOTON-STIMULATED DESORPTION FROM ALKALI FLUORIDES

Description: Photon-stimulated desorption experiments were performed on the (001) face of LiF for photon energies near the F(2s) and Li(ls) edges (from 37 to 72 eV). There are structures in the F{sup +} yield above the F(2s) edge which are absent in the Li{sup +} spectrum, differences in detail in the Li{sup +} and F{sup +} yields near the Li(1s) edge, and considerable broadening of the desorption yields as compared to the bulk photoabsorption spectrum. The first observation of a strong x-ray, and visible, beam exposure dependence of ion yields from LiF and NaF is also presented. These results are discussed in terms of electronic and defect properties of alkali halides.
Date: November 1, 1983
Creator: Parks, C.C.; Shirley, D.A. & Loubriel, G.
Partner: UNT Libraries Government Documents Department

Experimental and Theoretical Study of Electronic Transitions in Phosphorus, Phosphoryl, and Thiophosphoryl Trichlorofluorides

Description: This thesis is an investigation of the vacuum uv spectra of the phosphorus, phosphoryl, and thiophosphoryl trichlorofluorides in the region 1250 to 3000A. Assignments for absorption bands are made utilizing results from photoelectron spectra and ab initio calculations, oscillator strengths for absorption bands, and CNDO/2 molecular orbital calculations. Results from CNDO/2 calculations are compared with theoretical calculations, and experimental data are discussed with regard to the bonding in the compounds.
Date: May 1973
Creator: McAdams, Mary Jane
Partner: UNT Libraries

The Synthesis of N-(4-Nitrophenacyl)-4-Alkylpyridinium Halides and Reduction Products

Description: The synthesis of several N-(4-nitrophenacyl)-4-alkylpyridinium halides and their reduction products, 1-(4-aminophenyl)-2-[1-(4-alkylpiperidyl)]ethanols, was undertaken because of structural analogies between these and other physiologically active compounds, such as chloroamphenicol (I), 4,4'-diaminodiphenyl sulfone (II), and 2,2-bis(p-aminophenyl)-1,1,1-trichloroethane (III).
Date: 1950
Creator: Herd, Ray
Partner: UNT Libraries

Studies of non-proportionality in alkali halide and strontium iodide scintillators using SLYNCI

Description: Recently a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument to study the non-proportionality of scintillators. This device, known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument), has can completely characterize a sample with less than 24 hours of running time. Thus, SLYNCI enables a number of systematic studies of scintillators since many samples can be processed in a reasonable length of time. These studies include differences in nonproportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. The results of such recent studies are presented here, including a study of various alkali halides, and the impact of europium doping level in strontium iodide. Directions of future work area also discussed.
Date: October 14, 2010
Creator: Ahle, Larry; Bizarri, Gregory; Boatner, Lynn; Cherepy, Nerine J.; Choong, Woon-Seng; Moses, William W. et al.
Partner: UNT Libraries Government Documents Department

Hyperfine Interaction in FeCl(2): Moessbauer Studies to 61 GPa

Description: Over a wide pressure range FeCl{sub 2} is rather compressible due to its layered structure. At low pressures h-FeCl{sub 2} condenses into a close-packed, hexagonal phase with a CdI{sub 2} structure similar to the other anhydrous divalent transition metal halides. Anhydrous FeCl{sub 2} was synthesized by a direct Fe-Cl{sub 2} reaction using Fe enriched to 25% {sup 57}Fe. The anhydrous material is colorless and transparent.
Date: February 1, 1999
Creator: Pasternak, M.P.; Taylor, R.D. & Xu, W.M.
Partner: UNT Libraries Government Documents Department

Mechanisms of Methoxide Ion Substitution and Acid- Catalyzed Z/E Isomerization of N-Methoxyimines

Description: The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize highly functionalized O-methyloximes by reaction with enolate anions derived from malononitrile, ethyl cyanoacetate, and diethyl malonate. Acid-catalyzed isomerization of compounds containing the O-methyloxime moiety have been investigated with ab initio calculations (HF/6-31+G*, MP2/6- 31+G*//HF/6-31+G*, B3LYP/6-31+G*//HF/6-31+G*). Barriers for rotation around the C-N bond following protonation have been calculated. The calculated barriers are discussed in relation to an isomerization mechanism of protonation-rotation versus a nucleophilic catalysis.
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Date: December 2001
Creator: Dolliver, Debra D.
Partner: UNT Libraries

Part 1. Investigation of Aluminum Amino Acid Complexes; Part 2. Structural Studies of Aluminum Chalcogen Bonds

Description: Five different complexes of aluminum and amino acids have been synthesized and characterized. Reaction between aluminum halides and amino acids that do not contain either a carboxylate or a hydroxy group in the side chain produce complexes of the general formula, [Al(amino acid)_n(halide)_3-n]_m. The most prevalent form of this form of complex is where n = 2, and an example of this in which the halide is replaced by hydroxide ligand has been structurally characterized. The complex for which n = 3 may be obtained by employing a large excess of acid, and that for which n = 1 may be obtained by employing either equimolar conditions or an excess of aluminum halide. Reactions of aluminum halides with amino acids that contain either a carboxylate or hydroxy-containing side chain may result in complexes in which the side-chain is also bound. These proved impossible to characterize fully in the case of aspartic acid. For serine, however, a complex in which the amino acid binds in a chelating fashion through both the carboxylate and hydroxy groups was isolated. It was possible to form complexes when utilizing aluminum alkyls as the metal source. However, these complexes could only be isolated when the reactivity of the species was controlled by the presence of bulky groups. In these cases, the monomeric R_2Al(amino acid) complexes were obtained. Four complexes that contain aluminum-chalcogen bonds were structurally characterized. These included the bulky alkoxide complexes (BHT)_2AIH(OEt_2), (BHT)_3Al(cyclohexanone), and the cubane [(t-amyl)AlS]_4.
Date: May 1996
Creator: Gravelle, Philip W. (Philip Wyn)
Partner: UNT Libraries

BaBrI:Eu2 + , a new bright scintillator

Description: The scintillation properties of BaBrI:Eu2+ are reported. Crystals were produced by the vertical Bridgman technique in a sealed quartz ampoule. Excellent scintillation properties were measured. A light yield of 81,0007 +- 3000 photons per MeV (ph/MeV) of absorbed gamma-ray energy was measured. An energy resolution (FWHM over peak position) of 4.870.5percent was observed for the 662keV full absorption peak. Pulsed X-ray luminescence measurements show two exponential decay components of 297 and 482 ns with a contribution to the total light output of 23percent and 77percent, respectively. Under X-ray and UV excitation, the emission corresponds to a broadband center at 413 nm. These initial values make BaBrI:Eu2+ one of the brightest and the fastest known Eu2+ doped scintillators.
Date: November 7, 2009
Creator: Bourret-Courchesne, E.D.; Bizarri, G.; Hanrahan, S.M.; Gundiah, G.; Yan, Z. & Derenzo, S.E.
Partner: UNT Libraries Government Documents Department

Ion Partitioning at the liquid/vapor interface of a multi-component alkali halidesolution: A model for aqueous sea salt aerosols

Description: The chemistry of Br species associated with sea salt ice and aerosols has been implicated in the episodes of ozone depletion reported at Arctic sunrise. However, Br{sup -} is only a minor component in sea salt, which has a Br{sup -}/Cl{sup -} molar ratio of {approx}0.0015. Sea salt is a complex mixture of many different species, with NaCl as the primary component. In recent years experimental and theoretical studies have reported enhancement of the large, more polarizable halide ion at the liquid/vapor interface of corresponding aqueous alkali halide solutions. The proposed enhancement is likely to influence the availability of sea salt Br{sup -} for heterogeneous reactions such as those involved in the ozone depletion episodes. We report here ambient pressure x-ray photoelectron spectroscopy studies and molecular dynamics simulations showing direct evidence of Br{sup -} enhancement at the interface of an aqueous NaCl solution doped with bromide. The experiments were carried out on samples with Br{sup -}/Cl{sup -} ratios in the range 0.1% to 10%, the latter being also the ratio for which simulations were carried out. This is the first direct measurement of interfacial enhancement of Br{sup -} in a multi-component solution with particular relevance to sea salt chemistry.
Date: December 22, 2008
Creator: Ghosal, Sutapa; Brown, Matthew A.; Bluhm, Hendrik; Krisch, Maria J.; Salmeron, Miquel; Jungwirth, Pavel et al.
Partner: UNT Libraries Government Documents Department