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Preparation and Stability of Cobalt Trifluoride

Description: Report discussing the preparation, stability, and recommended storage of cobalt trifluoride. "Cobalt trifluoride prepared by the action of fluorine upon anhydrous cobalt dichloride remains stable when kept in sealed glass tubes but on exposure to air it absorbs water and its use in the conversion of T3O8 to TF6 cannot be relied upon..."
Date: October 15, 1945
Creator: Whitney, J.; Smith, Fred & Miller, A. J.
Partner: UNT Libraries Government Documents Department

Substitution Chemistry of the Cobalt Complexes [Co₂(CO)₆(PhC≡CR) (R=Ph, H) and PhCCo₃(CO)₉] with the Diphosphine Ligands [Bis(diphenylphosphino)maleic Anhydride (BMA) and (Z)-Ph₂PCH=CHPPh₂]. Reversible Chelate-to-Bridge Diphosphine Ligand Exchange, Phosphorus-Carbon Bond Cleavage and Phosphorus-Carbon Bond Formation

Description: The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At -97 °C, 31P NMR analysis of 2 reveals a Keq of 5.7 in favor of the bridging isomer. The bridged bma cluster 2 is the only observed species above -50°C. The solid-state structure of 2 does not correspond to the major bridging isomer observed in solution but rather the minor chelating isomer. The conversion of 2 to 3 followed first-order kinetics, with the reaction rates being independent of the nature of the reaction solvent and strongly suppressed by added CO, supporting a dissociative loss of CO as the rate-determining step. The activation parameters for CO loss were determined to be ΔH≠ = 29.9 ± 2.2 kcal/mol and ΔS≠ = 21.6 ± 6 eu.
Date: December 1994
Creator: Yang, Kaiyuan
Partner: UNT Libraries

A Study of Synthesis and Stereoisomerism of some Complex Cobalt Compounds

Description: The purpose of this investigation is two-fold. Some new complex compounds, where one of the bidentate molecules is an optically active amino acid, were prepared, and attempts to separate those complex isomers by different methods were made. The replacement of the amino acids by optically inactive ligands was studied.
Date: January 1965
Creator: Yuan, Daniel T. N.
Partner: UNT Libraries

The Uranium-Cobalt System

Description: Abstract: "A phase diagram for the uranium-cobalt system has been constructed, based on thermal, microscopic, X-ray and chemical data. The results indicate the existence of three compounds and two eutectics, one of which shows a lowering of the melting point of uranium by approximately 400 C."
Date: March 1, 1946
Creator: Noyce, William Knight & Daane, A. H.
Partner: UNT Libraries Government Documents Department

Blackbird Cobalt Deposits, Lemhi County, Idaho

Description: Report from the U.S. Bureau of Mines on exploration of known cobalt ore deposits in Lemhi County, Idaho. Physical features of the area, and properties of the cobalt samples collected are presented. This report includes tables, maps, and illustrations.
Date: February 1947
Creator: Reed, G. C. & Herdlick, J. A.
Partner: UNT Libraries Government Documents Department

Synthesis, structure and redox reactivity of Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂)

Description: The tricobalt cluster PhCCo₃(CO)₉ (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic thioanhydride (bta) with added Me₃NO to yield PhCCo₃(CO)₇(bta) (2), which upon heating overnight yields Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂) (3). Cluster (3) has been isolated and characterized by FT-IR and ³¹P NMR spectroscopy. Structural determination of the cluster has been demonstrated by X-ray diffraction analysis. Cluster (3) is analogous to the cluster synthesized by Richmond and coworkers. The redox properties of (3) have been examined by cyclic voltammetry and the data are reported within.
Date: May 1994
Creator: Muñoz, Trinidad
Partner: UNT Libraries

Metal Complexes of 2,3-Quinoxalinedithiol

Description: A series of new planar complexes with the dianion of 2,3-quinoxalinedithiol ligand has been prepared. The complexes have been characterized from the study of their analyses, magnetic moment, conductance, polarograms, electron spin resonance spectra, and electronic spectra, and compared with the available data on the corresponding maleonitriledithiolene and toluene-3,4-dithiolene complexes.
Date: May 1969
Creator: Ganguli, Kalyan Kumar, 1912-
Partner: UNT Libraries

Quantitative Analysis Laboratory Experiment: Bilinear Regression Analysis as a Means to Reduce Matrix Effects in Simultaneous Spectrophotometric Determination of Cr(III) and Co(II)

Description: Article on bilinear regression analysis as a means to reduce matrix effects in simultaneous spectrophotometric determination of Cr(III) and Co(II) and a quantitative analysis laboratory experiment.
Date: July 1, 1998
Creator: Pandey, Siddharth; McHale, Mary E. R.; Coym, Karen S. & Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

Studies of nuclear resonant absorption of gamma rays : covering the period from September 1 to November 30, 1961

Description: A report about the absorption of gamma rays. Absorption measurements were made using pressures up to 40,000 psi, but no measurable changes were found over this range. Experiments were carried out to determine whether there was any change in the fraction of recoil free emissions of gamma rays.
Date: 1962
Creator: Ezop, James J.; Greenwood, R. & Terrell, C. W.
Partner: UNT Libraries Government Documents Department

Effect of heat treatment upon the microstructure and hardness of a wrought cobalt-base alloy stellite 21 (AMS 5385)

Description: Report presenting an investigation of the response of wrought Stellite 21, a typical cobalt-base alloy, to heat treatment. The alloy was solution-treated and transformed by aging and isothermal transformation at temperatures of 1200 to 1950 degrees Fahrenheit for periods of 5 minutes to 72 hours. Results regarding the solution-treated structure, precipitation by isothermal transformation, precipitation by aging, grain boundary behavior, and hardness are provided.
Date: March 1954
Creator: Clauss, F. J. & Weeton, J. W.
Partner: UNT Libraries Government Documents Department

Heats of Solution of the Cobaltous Nitrate Hydrates in Water and in Certain Organic Solvents and Binding Energies of Molecular Ligands

Description: Abstract: "Heats of solution have been measured for the hexahydrate, tetrahydrate, trihydrate and dihydrate of cobaltus nitrate in water and in a series of organic solvents, including isobutyl alcohol, diethyland monoethyl ether of ethylene glycol, acetone, methyl ethyl ketone, tetrahydrofuran, tributyl phosphate and dimethyl formanide. For some solvents, where the solubility of the salt of its reaction product was insufficient, measurements were made in a mixture with acetone. Such solvents include diethyl ether, tetrahydrofurfuryl alcohol, and pyridine. Measurements were also made with mixtures of the other solvents cited and acetone. In the cases of pyridine, water, tetrahydrofurfuryl alcohol and isobutyl alcohol, evidence is found for a transition from a probably tetrasolvated neutral molecule in solution to a hexasolvated entity, frequently of lowered solubility. The solvents can be arrayed in order of base strengths on the basis of the heat measurements, and it is possible to estimate energies of binding of solvent groups by the metal atom. As a check on these some measurements of the heats of solution of some cobaltous nitrate pyridinates are also presented."
Date: February 1952
Creator: Katzin, Leonard I. & Ferraro, John R., {}
Partner: UNT Libraries Government Documents Department

The Radiochemistry of Cobalt

Description: The radiochemistry of cobalt is discussed. Included are a review of the nuclear and chemical features of cobalt, a discussion of problems of dissolution of a sample and counting techniques, and a collection of radiochemical procedures for the element as found in the literature. (M.C.G.)
Date: January 1, 1961
Creator: Bate, L. C. & Leddicotte, G. W.
Partner: UNT Libraries Government Documents Department

High-Spin Cobalt Hydrides for Catalysis

Description: Organometallic chemists have traditionally used catalysts with strong-field ligands that give low-spin complexes. However, complexes with a weak ligand field have weaker bonds and lower barriers to geometric changes, suggesting that they may lead to more rapid catalytic reactions. Developing our understanding of high-spin complexes requires the use of a broader range of spectroscopic techniques, but has the promise of changing the mechanism and/or selectivity of known catalytic reactions. These changes may enable the more efficient utilization of chemical resources. A special advantage of cobalt and iron catalysts is that the metals are more abundant and cheaper than those currently used for major industrial processes that convert unsaturated organic molecules and biofeedstocks into useful chemicals. This project specifically evaluated the potential of high-spin cobalt complexes for small-molecule reactions for bond rearrangement and cleavage reactions relevant to hydrocarbon transformations. We have learned that many of these reactions proceed through crossing to different spin states: for example, high-spin complexes can flip one electron spin to access a lower-energy reaction pathway for beta-hydride elimination. This reaction enables new, selective olefin isomerization catalysis. The high-spin cobalt complexes also cleave the C-O bond of CO2 and the C-F bonds of fluoroarenes. In each case, the detailed mechanism of the reaction has been determined. Importantly, we have discovered that the cobalt catalysts described here give distinctive selectivities that are better than known catalysts. These selectivities come from a synergy between supporting ligand design and electronic control of the spin-state crossing in the reactions.
Date: August 29, 2013
Creator: Holland, Patrick L.
Partner: UNT Libraries Government Documents Department

Evaporation of Iron-, Nickel-, and Cobalt-Base Alloys at 760 to 980°C in High Vacuums

Description: Report issued by the Oak Ridge National Laboratory discussing the evaporation of alloys in high vacuums. As stated in the introduction, "the investigation encompasses measurements of the evaporation rates, identification of the evaporating elements, and correlation of these measurements to the alloy composition for specimens in both the polished and oxidized conditions" (p. 2). This report includes tables, illustrations, and photographs.
Date: November 1964
Creator: Bourgette, D. T.
Partner: UNT Libraries Government Documents Department

Disorder-driven hysteresis-loop criticality in Co/CoO-films.

Description: The effect of magnetic disorder on the magnetization reversal process in thin Co/CoO-films has been investigated. The antiferromagnetic CoO layer allows a reversible tuning of the magnetic disorder by simple temperature variation. For temperatures above a critical temperature T{sub c}, we observe a discontinuous magnetization reversal, whereas smooth magnetization loops occur for T < T{sub c}. Our measurements establish the existence of a disorder-driven critical point in the non-equilibrium phase diagram. In addition, we observe scaling behavior in the vicinity of the critical point and determine the critical exponents to {beta} = 0.022 {+-} 0.006 and {beta}{delta} = 0.30 {+-} 0.03.
Date: November 1, 2000
Creator: Berger, A.; Inomata, A.; Jiang, J. S.; Pearson, J. E. & Bader, S. D.
Partner: UNT Libraries Government Documents Department

Training effects and the microscopic magnetic structure of exchange biased Co/CoO bilayers.

Description: Exchange bias of a partially oxidized thin film of ferromagnetic Co was studied by magnetization measurements and polarized neutron reflectivity (PNR). The magnetization curve shows strong effects of training with cycling of the magnetic field. Reflectivity measurements with the field parallel to the cooling field showed the onset of spin-dependent diffuse scattering--off the specular reflection--after a training cycle. Such scattering, of the Yoneda type, is due to misaligned Co domains possibly close to the Co/CoO interface. Subjecting the field cooled Co/CoO pair to a field perpendicular to the cooling field causes a rotation of the magnetization. PNR measurements confirmed earlier susceptibility studies by indicating that the rotation of the magnetization is reversible in fields up to 400 Oe. The rotation of the magnetization of Co is uniform across the film thickness.
Date: September 1, 1999
Creator: Berger, A.; Dahlberg, E. D.; Felcher, G. P.; Hill, B. K. & te Velthius, S. G. E.
Partner: UNT Libraries Government Documents Department