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Sample records for hafnium sulfides

  1. Hafnium

    SciTech Connect

    1994-02-01

    Having been predicted from atomic number sequence, it was the first element to be discovered by X-ray methods in 1923, following spectroscopic examination of zirconium minerals by D. Coster and G. C. de Hevesey. Hafnium derives its name from {open_quotes}Hafnia{close_quotes}, the Latin name for Copenhagen. The crustal abundance of hafnium is estimated at 2.8-4.5 ppm. The element hafnium is commonly found only in solid solution with zirconium in various zirconium ores, and is a by-product of zirconium metal production. The major commercial mineral source of hafnium is zircon; a minor source is baddeleyite. Zircon, typically 67% zirconium plus hafnium oxides, is found in alluvial or beach deposits together with other heavy minerals such as rutile and ilmenite. The ratio of zirconium to hafnium in zircon averages about 50:1. Recovery is accomplished by mining, dredging on scraping, followed by wet concentration by gravity processing and then dry separation, usually by magnetic or electrostatic processes. The zirconium/hafnium concentrate is separated by liquid-liquid extraction using methyl isobutyl ketone, or extractive distillation to produce hafnium oxide. Hafnium sponge is produced by reacting the oxide with chlorine in a fluid bed chlorinator, followed by a {open_quotes}Kroll-type{close_quotes} reaction. Additional refining of the metal is possible by electrofining, electron beam melting, or the iodide process. Refined hafnium metal is regularly referred to as {open_quotes}crystal bar hafnium-iodide metal{close_quotes}, or ductile hafnium.

  2. SEPARATING HAFNIUM FROM ZIRCONIUM

    DOEpatents

    Lister, B.A.J.; Duncan, J.F.

    1956-08-21

    A dilute aqueous solution of zirconyl chloride which is 1N to 2N in HCl is passed through a column of a cation exchange resin in acid form thereby absorbing both zirconium and associated hafnium impurity in the mesin. The cation exchange material with the absorbate is then eluted with aqueous sulfuric acid of a O.8N to 1.2N strength. The first portion of the eluate contains the zirconium substantially free of hafnium.

  3. Amphoteric Aqueous Hafnium Cluster Chemistry.

    PubMed

    Goberna-Ferrón, Sara; Park, Deok-Hie; Amador, Jenn M; Keszler, Douglas A; Nyman, May

    2016-05-17

    Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography.

  4. SEPARATING HAFNIUM FROM ZIRCONIUM

    DOEpatents

    Lister, B.A.J.; Duncan, J.F.; Hutcheon, J.M.

    1956-08-21

    Substantially complete separation of zirconium from hafnium may be obtained by elution of ion exchange material, on which compounds of the elements are adsorbed, with an approximately normal solution of sulfuric acid. Preferably the acid concentration is between 0.8 N amd 1.2 N, amd should not exceed 1.5 N;. Increasing the concentration of sulfate ion in the eluting solution by addition of a soluble sulfate, such as sodium sulfate, has been found to be advantageous. The preferred ion exchange materials are sulfonated polystyrene resins such as Dowex 50,'' and are preferably arranged in a column through which the solutions are passed.

  5. SEPARATION OF HAFNIUM FROM ZIRCONIUM

    DOEpatents

    Overholser, L.B.; Barton, C.J. Sr.; Ramsey, J.W.

    1960-05-31

    The separation of hafnium impurities from zirconium can be accomplished by means of organic solvent extraction. The hafnium-containing zirconium feed material is dissolved in an aqueous chloride solution and the resulting solution is contacted with an organic hexone phase, with at least one of the phases containing thiocyanate. The hafnium is extracted into the organic phase while zirconium remains in the aqueous phase. Further recovery of zirconium is effected by stripping the onganic phase with a hydrochloric acid solution and commingling the resulting strip solution with the aqueous feed solution. Hexone is recovered and recycled by means of scrubbing the onganic phase with a sulfuric acid solution to remove the hafnium, and thiocyanate is recovered and recycled by means of neutralizing the effluent streams to obtain ammonium thiocyanate.

  6. Ablation Resistant Zirconium and Hafnium Ceramics

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  7. Zirconium and hafnium in meteorites

    NASA Technical Reports Server (NTRS)

    Ehmann, W. D.; Chyi, L. L.

    1974-01-01

    The abundances of zirconium and hafnium have been determined in nine stony meteorites by a new, precise neutron-activation technique. The Zr/Hf abundance ratios for the chondrites vary in a rather narrow range, consistent with previously published observations from our group. Replicate analyses of new, carefully selected clean interior samples of the Cl chondrite Orgueil yield mean zirconium and hafnium abundances of 5.2 and 0.10 ppm, respectively. These abundances are lower than we reported earlier for two Cl chondrite samples which we now suspect may have suffered contamination. The new Cl zirconium and hafnium abundances are in closer agreement with predictions based on theories of nucleosynthesis than the earlier data.

  8. Hafnium radioisotope recovery from irradiated tantalum

    DOEpatents

    Taylor, Wayne A.; Jamriska, David J.

    2001-01-01

    Hafnium is recovered from irradiated tantalum by: (a) contacting the irradiated tantalum with at least one acid to obtain a solution of dissolved tantalum; (b) combining an aqueous solution of a calcium compound with the solution of dissolved tantalum to obtain a third combined solution; (c) precipitating hafnium, lanthanide, and insoluble calcium complexes from the third combined solution to obtain a first precipitate; (d) contacting the first precipitate of hafnium, lanthanide and calcium complexes with at least one fluoride ion complexing agent to form a fourth solution; (e) selectively adsorbing lanthanides and calcium from the fourth solution by cationic exchange; (f) separating fluoride ion complexing agent product from hafnium in the fourth solution by adding an aqueous solution of ferric chloride to obtain a second precipitate containing the hafnium and iron; (g) dissolving the second precipitate containing the hafnium and iron in acid to obtain an acid solution of hafnium and iron; (h) selectively adsorbing the iron from the acid solution of hafnium and iron by anionic exchange; (i) drying the ion exchanged hafnium solution to obtain hafnium isotopes. Additionally, if needed to remove residue remaining after the product is dried, dissolution in acid followed by cation exchange, then anion exchange, is performed.

  9. Hafnium isotope stratigraphy of ferromanganese crusts

    USGS Publications Warehouse

    Lee, D.-C.; Halliday, A.N.; Hein, J.R.; Burton, K.W.; Christensen, J.N.; Gunther, D.

    1999-01-01

    A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in 87Sr/86Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.

  10. Hafnium carbide formation in oxygen deficient hafnium oxide thin films

    NASA Astrophysics Data System (ADS)

    Rodenbücher, C.; Hildebrandt, E.; Szot, K.; Sharath, S. U.; Kurian, J.; Komissinskiy, P.; Breuer, U.; Waser, R.; Alff, L.

    2016-06-01

    On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO2-x) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfCx) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfCx surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO2 thin films prepared and measured under identical conditions, the formation of HfCx was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.

  11. Silver-hafnium braze alloy

    DOEpatents

    Stephens, Jr., John J.; Hosking, F. Michael; Yost, Frederick G.

    2003-12-16

    A binary allow braze composition has been prepared and used in a bonded article of ceramic-ceramic and ceramic-metal materials. The braze composition comprises greater than approximately 95 wt % silver, greater than approximately 2 wt % hafnium and less than approximately 4.1 wt % hafnium, and less than approximately 0.2 wt % trace elements. The binary braze alloy is used to join a ceramic material to another ceramic material or a ceramic material, such as alumina, quartz, aluminum nitride, silicon nitride, silicon carbide, and mullite, to a metal material, such as iron-based metals, cobalt-based metals, nickel-based metals, molybdenum-based metals, tungsten-based metals, niobium-based metals, and tantalum-based metals. A hermetic bonded article is obtained with a strength greater than 10,000 psi.

  12. Ferroelectricity in undoped hafnium oxide

    SciTech Connect

    Polakowski, Patrick; Müller, Johannes

    2015-06-08

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4–20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization P{sub r} of up to 10 μC cm{sup −2} as well as a read/write endurance of 1.6 × 10{sup 5} cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  13. Ferroelectricity in undoped hafnium oxide

    NASA Astrophysics Data System (ADS)

    Polakowski, Patrick; Müller, Johannes

    2015-06-01

    We report the observation of ferroelectric characteristics in undoped hafnium oxide thin films in a thickness range of 4-20 nm. The undoped films were fabricated using atomic layer deposition (ALD) and embedded into titanium nitride based metal-insulator-metal (MIM) capacitors for electrical evaluation. Structural as well as electrical evidence for the appearance of a ferroelectric phase in pure hafnium oxide was collected with respect to film thickness and thermal budget applied during titanium nitride electrode formation. Using grazing incidence X-Ray diffraction (GIXRD) analysis, we observed an enhanced suppression of the monoclinic phase fraction in favor of an orthorhombic, potentially, ferroelectric phase with decreasing thickness/grain size and for a titanium nitride electrode formation below crystallization temperature. The electrical presence of ferroelectricity was confirmed using polarization measurements. A remanent polarization Pr of up to 10 μC cm-2 as well as a read/write endurance of 1.6 × 105 cycles was measured for the pure oxide. The experimental results reported here strongly support the intrinsic nature of the ferroelectric phase in hafnium oxide and expand its applicability beyond the doped systems.

  14. Formulation and method for preparing gels comprising hydrous hafnium oxide

    SciTech Connect

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

    2013-08-06

    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  15. Hafnium Germanate from a Hydrous Hafnium Germanium Oxide Gel.

    PubMed

    Lambert, P. M.

    1998-03-23

    The gel chemistry of germanium is explored through the formation and composition of a hydrous metal oxide precursor gel used in the preparation of the HfGeO(4) and HfGeO(4):Ti X-ray phosphors. The enhanced solubility of hexagonal GeO(2) in dilute ammoniacal solutions is exploited to give a convenient and high-yield precipitation. The precursor gel is shown by FT-IR to be a diphasic mixture of hydrous hafnia and an ammonium germanate gel. Thermal treatment drives the crystallization of a hafnium-rich, simple tetragonal Hf(1)(-)(x)()Ge(x)()O(2) structure at 893 degrees C, that upon further heating to 1200 degrees C yields scheelite HfGeO(4).

  16. Thermal Expansion of Hafnium Carbide

    NASA Technical Reports Server (NTRS)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  17. Hafnium transistor process design for neural interfacing.

    PubMed

    Parent, David W; Basham, Eric J

    2009-01-01

    A design methodology is presented that uses 1-D process simulations of Metal Insulator Semiconductor (MIS) structures to design the threshold voltage of hafnium oxide based transistors used for neural recording. The methodology is comprised of 1-D analytical equations for threshold voltage specification, and doping profiles, and 1-D MIS Technical Computer Aided Design (TCAD) to design a process to implement a specific threshold voltage, which minimized simulation time. The process was then verified with a 2-D process/electrical TCAD simulation. Hafnium oxide films (HfO) were grown and characterized for dielectric constant and fixed oxide charge for various annealing temperatures, two important design variables in threshold voltage design.

  18. Percolation conductivity in hafnium sub-oxides

    SciTech Connect

    Islamov, D. R. Gritsenko, V. A.; Cheng, C. H.; Chin, A.

    2014-12-29

    In this study, we demonstrated experimentally that formation of chains and islands of oxygen vacancies in hafnium sub-oxides (HfO{sub x}, x < 2) leads to percolation charge transport in such dielectrics. Basing on the model of Éfros-Shklovskii percolation theory, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics was achieved. Based on the percolation theory suggested model shows that hafnium sub-oxides consist of mixtures of metallic Hf nanoscale clusters of 1–2 nm distributed onto non-stoichiometric HfO{sub x}. It was shown that reported approach might describe low resistance state current-voltage characteristics of resistive memory elements based on HfO{sub x}.

  19. Calibration of the Lutetium-Hafnium Clock

    NASA Astrophysics Data System (ADS)

    Scherer, Erik; Münker, Carsten; Mezger, Klaus

    2001-07-01

    Well-defined constants of radioactive decay are the cornerstone of geochronology and the use of radiogenic isotopes to constrain the time scales and mechanisms of planetary differentiation. Four new determinations of the lutetium-176 decay constant (λ176Lu) made by calibration against the uranium-lead decay schemes yield a mean value of 1.865 +/- 0.015 × 10-11 year-1, in agreement with the two most recent decay-counting experiments. Lutetium-hafnium ages that are based on the previously used λ176Lu of 1.93 × 10-11 to 1.94 × 10-11 year-1 are thus ~4% too young, and the initial hafnium isotope compositions of some of Earth's oldest minerals and rocks become less radiogenic relative to bulk undifferentiated Earth when calculated using the new decay constant. The existence of strongly unradiogenic hafnium in Early Archean and Hadean zircons implies that enriched crustal reservoirs existed on Earth by 4.3 billion years ago and persisted for 200 million years or more. Hence, current models of early terrestrial differentiation need revision.

  20. Calibration of the lutetium-hafnium clock.

    PubMed

    Scherer, E; Munker, C; Mezger, K

    2001-07-27

    Well-defined constants of radioactive decay are the cornerstone of geochronology and the use of radiogenic isotopes to constrain the time scales and mechanisms of planetary differentiation. Four new determinations of the lutetium-176 decay constant (lambda176Lu) made by calibration against the uranium-lead decay schemes yield a mean value of 1.865 +/- 0.015 x 10(-11) year(-1), in agreement with the two most recent decay-counting experiments. Lutetium-hafnium ages that are based on the previously used lambda176Lu of 1.93 x 10(-11) to 1.94 x 10(-11) year(-1) are thus approximately 4% too young, and the initial hafnium isotope compositions of some of Earth's oldest minerals and rocks become less radiogenic relative to bulk undifferentiated Earth when calculated using the new decay constant. The existence of strongly unradiogenic hafnium in Early Archean and Hadean zircons implies that enriched crustal reservoirs existed on Earth by 4.3 billion years ago and persisted for 200 million years or more. Hence, current models of early terrestrial differentiation need revision.

  1. Assessing hafnium on hafnia as an oxygen getter

    SciTech Connect

    O'Hara, Andrew; Demkov, Alexander A.; Bersuker, Gennadi

    2014-05-14

    Hafnium dioxide or hafnia is a wide band gap dielectric used in a range of electronic applications from field effect transistors to resistive memory. In many of these applications, it is important to maintain control over oxygen stoichiometry, which can be realized in practice by using a metal layer, specifically hafnium, to getter oxygen from the adjacent dielectric. In this paper, we employ density functional theory to study the thermodynamic stability of an interface between (100)-oriented monoclinic hafnia and hafnium metal. The nudged elastic band method is used to calculate the energy barrier for migration of oxygen from the oxide to the metal. Our investigation shows that the presence of hafnium lowers the formation energy of oxygen vacancies in hafnia, but more importantly the oxidation of hafnium through the migration of oxygen from hafnia is favored energetically.

  2. Selenium Sulfide

    MedlinePlus

    Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium sulfide usually is used twice a week for the first ... it is irritating. Rinse off all of the lotion.Do not use this medication on children younger ...

  3. Hafnium transistor design for neural interfacing.

    PubMed

    Parent, David W; Basham, Eric J

    2008-01-01

    A design methodology is presented that uses the EKV model and the g(m)/I(D) biasing technique to design hafnium oxide field effect transistors that are suitable for neural recording circuitry. The DC gain of a common source amplifier is correlated to the structural properties of a Field Effect Transistor (FET) and a Metal Insulator Semiconductor (MIS) capacitor. This approach allows a transistor designer to use a design flow that starts with simple and intuitive 1-D equations for gain that can be verified in 1-D MIS capacitor TCAD simulations, before final TCAD process verification of transistor properties. The DC gain of a common source amplifier is optimized by using fast 1-D simulations and using slower, complex 2-D simulations only for verification. The 1-D equations are used to show that the increased dielectric constant of hafnium oxide allows a higher DC gain for a given oxide thickness. An additional benefit is that the MIS capacitor can be employed to test additional performance parameters important to an open gate transistor such as dielectric stability and ionic penetration.

  4. Internal dosimetry for inhalation of hafnium tritide aerosols.

    PubMed

    Inkret, W C; Schillaci, M E; Boyce, M K; Cheng, Y S; Efurd, D W; Little, T T; Miller, G; Musgrave, J A; Wermer, J R

    2001-01-01

    Metal tritides with low dissolution rates may have residence times in the lungs which are considerably longer than the biological half-time normally associated with tritium in body water, resulting in long-term irradiation of the lungs by low energy beta particles and bremsstrahlung X rays. Samples of hafnium tritide were placed in a lung simulant fluid to determine approximate lung dissolution rates. Hafnium hydride samples were analysed for particle size distribution with a scanning electron microscope. Lung simulant data indicated a biological dissolution half-time for hafnium tritide on the order of 10(5) d. Hafnium hydride particle sizes ranged between 2 and 10 microns, corresponding to activity median aerodynamic diameters of 5 to 25 microns. Review of in vitro dissolution data, development of a biokinetic model, and determination of secondary limits for 1 micron AMAD particles are presented and discussed.

  5. Hafnium(IV) tetratriflate as a glycosyl fluoride activation reagent.

    PubMed

    Manabe, Shino; Ito, Yukishige

    2013-05-01

    Hafnium(IV) tetratriflate was found to be a good activator of glycosyl fluoride. The protocol was operationally simple and was widely applicable to a variety of substrates in both solid-phase and solution-phase glycosylation reactions.

  6. Carbonyl sulfide

    Integrated Risk Information System (IRIS)

    Carbonyl sulfide ; CASRN 463 - 58 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  7. Hydrogen sulfide

    Integrated Risk Information System (IRIS)

    Hydrogen sulfide ; 7783 - 06 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  8. Selenium sulfide

    Integrated Risk Information System (IRIS)

    Selenium sulfide ; CASRN 7446 - 34 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  9. 40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants to waters of...

  10. 40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants...

  11. 40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary zirconium and hafnium subcategory. 421.330 Section 421.330 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of this subpart are applicable to discharges...

  12. 40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants...

  13. 40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants to waters of...

  14. 40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary zirconium and hafnium subcategory. 421.330 Section 421.330 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of this subpart are applicable to discharges...

  15. 40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... zirconium-hafnium forming subcategory. 471.90 Section 471.90 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This subpart applies to discharges of pollutants...

  16. Hafnium isotope variations in oceanic basalts

    NASA Technical Reports Server (NTRS)

    Patchett, P. J.; Tatsumoto, M.

    1980-01-01

    Hafnium isotope ratios generated by the beta(-) decay of Lu-176 are investigated in volcanic rocks derived from the suboceanic mantle. Hf-176/Hf-177 and Lu/Hf ratios were determined to precisions of 0.01-0.04% and 0.5%, respectively, by routine, low-blank chemistry. The Hf-176/Hf-177 ratio is found to be positively correlated with the Nd-143/Nd-144 ratio and negatively correlated with the Sr-87/Sr-86 and Pb-206/Pb-204 ratios, and to increase southwards along the Iceland-Reykjanes ridge traverse. An approximate bulk earth Hf-176/Hf-177 ratio of 0.28295 is inferred from the bulk earth Nd-143/Nd-144 ratio, which requires a bulk earth Lu/Hf ratio of 0.25, similar to the Juvinas eucrite. Midocean ridge basalts are shown to account for 60% of the range of Hf isotope ratios, and it is suggested that Lu-Hf fractionation is decoupled from Sm-Nd and Rb-Sr fractionation in very trace-element-depleted source regions as a result of partial melting.

  17. Ground-state structures of Hafnium clusters

    SciTech Connect

    Ng, Wei Chun; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    Hafnium (Hf) is a very large tetra-valence d-block element which is able to form relatively long covalent bond. Researchers are interested to search for substitution to silicon in the semi-conductor industry. We attempt to obtain the ground-state structures of small Hf clusters at both empirical and density-functional theory (DFT) levels. For calculations at the empirical level, charge-optimized many-body functional potential (COMB) is used. The lowest-energy structures are obtained via a novel global-minimum search algorithm known as parallel tempering Monte-Carlo Basin-Hopping and Genetic Algorithm (PTMBHGA). The virtue of using COMB potential for Hf cluster calculation lies in the fact that by including the charge optimization at the valence shells, we can encourage the formation of proper bond hybridization, and thus getting the correct bond order. The obtained structures are further optimized using DFT to ensure a close proximity to the ground-state.

  18. Some properties of RF sputtered hafnium nitride coatings

    NASA Technical Reports Server (NTRS)

    Aron, P. R.; Grill, A.

    1982-01-01

    Hafnium nitride coatings were deposited by reactive RF sputtering from a hafnium target in nitrogen and argon gas mixtures. The rate of deposition, composition, electrical resistivity and complex index of refraction were investigated as a function of target substrate distance and the fraction nitrogen, (fN2) in the sputtering atmosphere. The relative composition of the coatings is independent on fN2 for values above 0.1. The electric resistivity of the hafnium nitride films changes over 8 orders of magnitude when fN2 changes from 0.10 to 0.85. The index of refraction is almost constant at 2.8(1-0.3i) up to fN2 = 0.40 then decreases to 2.1(1 - 0.01i) for higher values of fN2.

  19. Potential of hafnium nitride for the hot carrier solar cell

    NASA Astrophysics Data System (ADS)

    Chung, Simon; Shrestha, Santosh; Xia, Hongze; Gupta, Neeti; Conibeer, Gavin

    2013-12-01

    The Hot Carrier solar cell is a third generation photovoltaic concept which has the potential to achieve high efficiencies, exceeding the Shockley-Queisser limit for a conventional p-n junction solar cell. The theoretical efficiencies achievable for the Hot Carrier solar cell is 65% for non-concentrated solar radiation and 85% for maximally concentrated light, very close to the limits of an infinite tandem solar cell. The approach of the Hot Carrier solar cell is to extract carriers generated before thermalisation to the bandgap edge occurs when their excess energy is lost to the environment as heat. To achieve this, the rate of carrier cooling in the absorber must be slowed down sufficiently enough to allow carriers to be collected while they are hot. This work investigates using hafnium nitride as such an absorber to restrict mechanisms of carrier cooling. Hafnium nitride's phononic properties, where a large `phononic band gap' exist can reduce the carrier cooling rate by means of a phonon bottleneck such that optical phonons cannot decay into acoustic phonons by means of the Klemens' mechanism. Optical phonon-electron scattering can maintain a hot electron population while acoustic phonons are irrecoverable and lost as heat. The electronic and phononic properties of hafnium nitride are evaluated for their suitability to be used in a Hot Carrier solar cell absorber. Recent work on the fabrication of hafnium nitride at UNSW is presented.

  20. Discovery of gallium, germanium, lutetium, and hafnium isotopes

    SciTech Connect

    Gross, J.L.; Thoennessen, M.

    2012-09-15

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  1. Mineral resource of the month: zirconium and hafnium

    USGS Publications Warehouse

    Gambogi, Joseph

    2007-01-01

    Zirconium and hafnium are corrosion-resistant metals that are grouped in the same family as titanium on the periodic table. The two elements commonly occur in oxide and silicate minerals and have significant economic importance in everything from ink, ceramics and golf shoes to nuclear fuel rods.

  2. Article having an improved platinum-aluminum-hafnium protective coating

    NASA Technical Reports Server (NTRS)

    Nagaraj, Bangalore Aswatha (Inventor); Williams, Jeffrey Lawrence (Inventor)

    2005-01-01

    An article protected by a protective coating has a substrate and a protective coating having an outer layer deposited upon the substrate surface and a diffusion zone formed by interdiffusion of the outer layer and the substrate. The protective coating includes platinum, aluminum, no more than about 2 weight percent hafnium, and substantially no silicon. The outer layer is substantially a single phase.

  3. Corrosion and tribocorrosion of hafnium in simulated body fluids.

    PubMed

    Rituerto Sin, J; Neville, A; Emami, N

    2014-08-01

    Hafnium is a passive metal with good biocompatibility and osteogenesis, however, little is known about its resistance to wear and corrosion in biological environments. The corrosion and tribocorrosion behavior of hafnium and commercially pure (CP) titanium in simulated body fluids were investigated using electrochemical techniques. Cyclic polarization scans and open circuit potential measurements were performed in 0.9% NaCl solution and 25% bovine calf serum solution to assess the effect of organic species on the corrosion behavior of the metal. A pin-on-plate configuration tribometer and a three electrode electrochemical cell were integrated to investigate the tribocorrosion performance of the studied materials. The results showed that hafnium has good corrosion resistance. The corrosion density currents measured in its passive state were lower than those measured in the case of CP titanium; however, it showed a higher tendency to suffer from localized corrosion, which was more acute when imperfections were present on the surface. The electrochemical breakdown of the oxide layer was retarded in the presence of proteins. Tribocorrosion tests showed that hafnium has the ability to quickly repassivate after the oxide layer was damaged; however, it showed higher volumetric loss than CP titanium in equivalent wear-corrosion conditions. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1157-1164, 2014.

  4. Hafnium Resonance Parameter Analysis using Neutron Capture and Transmission Experiments

    SciTech Connect

    Trbovich, Michael J.; Barry, Devin P.; Burke, John A.; Drindak, Noel J.; Leinweber, Greg; Ballad, Robert V.; Slovacek, Rudy E.; Danon, Yaron; Block, Robert C.

    2005-05-24

    The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping 176Hf and 178Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions.Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. 6Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen-section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically enriched liquid samples. The liquid samples were designed to provide information on the 176Hf and 178Hf contributions to the 8-eV doublet without saturation.Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

  5. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, Stanford R.; Yeung, Edward S.

    1985-01-01

    A method of chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction.

  6. Sulfide chemiluminescence detection

    DOEpatents

    Spurlin, S.R.; Yeung, E.S.

    1985-11-26

    A method is described for chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction. 4 figs.

  7. Initial reaction of hafnium oxide deposited by remote plasma atomic layer deposition method

    SciTech Connect

    Won, Youngdo; Park, Sangwook; Koo, Jaehyoung; Kim, Seokhoon; Kim, Jinwoo; Jeon, Hyeongtag

    2005-12-26

    A remote plasma atomic layer deposition (RPALD) method has been applied to grow a hafnium oxide thin film on the Si substrate. The deposition process was monitored by in situ XPS and the as-deposited structure and chemical bonding were examined by TEM and XPS. The in situ XPS measurement showed the presence of a hafnium silicate phase at the initial stage of the RPALD process up to the 20th cycle and indicated that no hafnium silicide was formed. The initial hafnium silicate was amorphous and grew to a thickness of approximately 2 nm. Based on these results and model reactions for silicate formation, we proposed an initial growth mechanism that includes adatom migration at nascent step edges. Density functional theory calculations on model compounds indicate that the hafnium silicate is thermodynamically favored over the hafnium silicide by as much as 250 kJ/mol.

  8. Electronic properties of hafnium oxide: A contribution from defects and traps

    NASA Astrophysics Data System (ADS)

    Gritsenko, Vladimir A.; Perevalov, Timofey V.; Islamov, Damir R.

    2016-02-01

    In the present article, we give a review of modern data and latest achievements pertaining to the study of electronic properties of oxygen vacancies in hafnium oxide. Hafnium oxide is a key dielectric for use in many advanced silicon devices. Oxygen vacancies in hafnium oxide largely determine the electronic properties of the material. We show that the electronic transitions between the states due to oxygen vacancies largely determine the optical absorption and luminescent properties of hafnium oxide. We discuss the role of oxygen vacancies as traps that facilitate charge transport in hafnium oxide films. Also, we demonstrate the fact that the electrical conductivity in hafnium oxide is controlled by the phonon-assisted tunnelling of charge carriers between traps that were identified as oxygen vacancies.

  9. Synthesis of Hafnium-Based Ceramic Materials for Ultra-High Temperature Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Johnson, Sylvia; Feldman, Jay

    2004-01-01

    This project involved the synthesis of hafnium (Hf)-based ceramic powders and Hf-based precursor solutions that were suitable for preparation of Hf-based ceramics. The Hf-based ceramic materials of interest in this project were hafnium carbide (with nominal composition HE) and hafnium dioxide (HfO2). The materials were prepared at Georgia Institute of Technology and then supplied to research collaborators Dr. Sylvia Johnson and Dr. Jay Feldman) at NASA Ames Research Center.

  10. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    SciTech Connect

    Trbovich, M J; Barry, D P; Slovacek, R E; Danon, Y; Block, R C; Francis, N C; Lubert, M; Burke, J A; Drindak, N J; Lienweber, G; Ballad, R

    2007-02-06

    The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental

  11. Alternative Processing of High Temperature Hafnium and Zirconium Based Materials

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew; Gusman, Michael; Ellerby, Don; Irby, Edward; Johnson, Sylvia M.

    2003-01-01

    The behavior of refractory hafnium and zirconium based materials are being investigated at NASA Ames as part of ongoing research aimed at developing superior heat resistant materials for aerospace applications. Hafnium and zirconium diboride based materials have shown high temperature capabilities in simulated reentry environments indicating that these materials may successfully operate as reusable oxidation resistant components for leading edge applications. Due to the refractory nature of these materials, processing of fine-grained uniform microstructures poses a number of challenges. To better understand the process-property-microstructure relationship, processing of these materials has been carried out with conventional hot pressing in addition to the novel approach of Spark Plasma Sintering (SPS). The two processing methods are compared and contrasted in an evaluation of the sintering behavior of high temperature diboride based materials and preliminary physical and mechanical properties are presented.

  12. Hydrothermal chemistry, structures, and luminescence studies of alkali hafnium fluorides.

    PubMed

    Underwood, Christopher C; McMillen, Colin D; Chen, Hongyu; Anker, Jeffery N; Kolis, Joseph W

    2013-01-01

    This paper describes the hydrothermal chemistry of alkali hafnium fluorides, including the synthesis and structural characterization of five new alkali hafnium fluorides. Two ternary alkali hafnium fluorides are described: Li(2)HfF(6) in space group P31m with a = 4.9748(7) Å and c = 4.6449(9) Å and Na(5)Hf(2)F(13) in space group C2/m with a = 11.627(2) Å, b = 5.5159(11) Å, and c = 8.4317(17) Å. Three new alkali hafnium oxyfluorides are also described: two fluoroelpasolites, K(3)HfOF(5) and (NH(4))(3)HfOF(5), in space group Fm3m with a = 8.9766(10) and 9.4144(11) Å, respectively, and K(2)Hf(3)OF(12) in space group R3m with a = 7.6486(11) Å and c = 28.802(6) Å. Infrared (IR) spectra were obtained for the title solids to confirm the structure solutions. Comparison of these materials was made based on their structures and synthesis conditions. The formation of these species in hydrothermal fluids appears to be dependent upon both the concentration of the alkali fluoride mineralizer solution and the reaction temperature. Both X-ray and visible fluorescence studies were conducted on compounds synthesized in this study and showed that fluorescence was affected by a variety of factors, such as alkali metal size, the presence/absence of oxygen in the compound, and the coordination environment of Hf(4+).

  13. Phase transformations in some hafnium-tantalum-titanium-zirconium alloys

    SciTech Connect

    Ohriner, E.K.; Kapoor, D.

    1997-11-01

    Phase transformations in hafnium alloys are of interest as a means of achieving a material which exhibits flow softening and high localized strains during deformation at high strain rates. Hafnium transforms from a body-centered-cubic beta phase to a hexagonal alpha phase upon cooling below 1749{degrees}C. Hafnium-based alloys containing up to 17.5% Ti, up to 17.5% Ta, and up to 7.3% Zr by weight were button-arc melted and, in some cases, hot extruded to obtain a refined grain size. A number of alloys were shown to have beta solvus temperatures in the range of 1100 to 1300{degrees}C and showed evidence of a shear transformation upon water quenching. The Vickers microhardness of the quenched materials are typically above 350 HV as compared to 300 HV or less for materials with an alpha plus beta structure. Quenching dilatometry indicates a martensite start temperature of about 750{degrees}C for the Hf-7.5 Ta-10 Ti-1 Zr alloy and 800{degrees}C or more for the Hf-7.5 Ta-7.5 Ti-1 Zr alloy. Tensile tests at 1 s{sup {minus}1} strain rate show a constant ultimate tensile strength for temperatures up to 600{degrees}C for the above two alloys and a rapid decrease in strength with a further increase in temperature.

  14. Continuous ion exchange separation of zirconium and hafnium

    SciTech Connect

    Begovich, J.M.; Sisson, W.G.

    1981-01-01

    A pressurized continuous annular chromatograph (CAC) has been developed for truly continuous ion exchange preparative separations. This device utilizes a slowly rotating annular bed of sorbent material, fixed multiple feed points, and fixed withdrawal locations. Most of our investigations have been performed with a 28-cm-diam by 60-cm-long CAC, but a larger model has recently been designed and constructed. A detailed study has been made of the separation of copper, nickel, and cobalt components from a simulated carbonate leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Recent studies have investigated the ion exchange separation of zirconium and hafnium from a sulfate feed solution. Nuclear reactor-grade zirconium, containing < 0.01 wt % hafnium, and hafnium, containing < 1% zirconium, have been continuously prepared using cation exchange resin in the pressurized CAC. This device, because of its continuous feed and product withdrawal, its adaptability to largescale operations, and its ability to separate many components, is expected to make chromatography a more competitive process in the industrial sector.

  15. Hafnium trifluoromethanesulfonate (hafnium triflate) as a highly efficient catalyst for chemoselective thioacetalization and transthioacetalization of carbonyl compounds.

    PubMed

    Wu, Yan-Chao; Zhu, Jieping

    2008-12-01

    A range of carbonyl compounds including aliphatic and aromatic aldehydes and ketones were converted to the corresponding thioacetals in high yields in the presence of a catalytic amount of hafnium trifluoromethanesulfonate (0.1 mol %, room temperature). The mild conditions tolerated various sensitive functional and protecting groups and were racemization-free when applied to alpha-aminoaldehydes. Transacetalization and chemoselective thioacetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones were also documented.

  16. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1992-07-07

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  17. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1991-10-22

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  18. SULFIDE MINERALS IN SEDIMENTS

    EPA Science Inventory

    The formation processes of metal sulfides in sediments, especially iron sulfides, have been the subjects of intense scientific research because of linkages to the global biogeochemical cycles of iron, sulfur, carbon, and oxygen. Transition metal sulfides (e.g., NiS, CuS, ZnS, Cd...

  19. Atomic layer deposition of hafnium oxide from hafnium chloride and water.

    PubMed

    Mukhopadhyay, Atashi B; Musgrave, Charles B; Fdez Sanz, Javier

    2008-09-10

    Hafnium oxide (HfO2) is a leading candidate to replace silicon oxide as the gate dielectric for future generation metal-oxide-semiconductor based nanoelectronic devices. Atomic layer deposition (ALD) has recently gained interest because of its suitability for fabrication of conformal films with thicknesses in the nanometer range. This study uses periodic density functional theory (DFT) to investigate the mechanisms of both half-reactions occurring on the growing surface during the ALD of HfO2 using HfCl4 and water as precursors. We find that the adsorption energy and the preferred site of adsorption of the metal precursor are strong functions of the water coverage. As water coverage increases, the metal precursor preferentially interacts with multiple surface adsorption sites. During the water pulse the removal of Cl can be facilitated by either a ligand exchange reaction or the dissociation of Cl upon increase in coordination of the Hf atom of the precursor. Our predicted potential energy surface indicates that a more likely mechanism is hydration of the adsorbed Hf complex up to a coordination number of 7, followed by the dissociation of a chloride ion that is stabilized by solvation. Born-Oppenheimer molecular dynamics (BOMD) simulations of an adsorbed metal precursor in the presence of a multilayer of water shows that Cl dissociation is facile if sufficient water molecules are present to solvate the Cl(-) anions. Hence, solvation plays a crucial role during the water pulse and provides an alternative explanation for why ALD growth rates for this system decrease at high temperatures.

  20. A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

    NASA Technical Reports Server (NTRS)

    Dupraw, W. A.

    1972-01-01

    A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

  1. Preparation of complexes of zirconium and hafnium tetrachlorides with phosphorus oxychloride

    SciTech Connect

    Snyder, T.S.; Stoltz, R.A.

    1989-09-12

    This patent describes an improvement in a method for separating hafnium chloride from zirconium chloride using a distillation column, with a hafnium chloride enriched vapor stream taken from the top of the column and a zirconium enriched chloride stream taken from the bottom of the column. The improvement comprising: purifying the zirconium-hafnium chloride in a molten salt purification vessel prior to or after introduction into the distillation column to substantially eliminate iron chloride from the zirconium-hafnium chloride by at least periodically removing iron chloride from the molten salt purification vessel by electrochemically plating iron onto an electrode in the molten salt purification vessel. The molten salt in the molten salt purification vessel consisting essentially of a mixture of chlorides selected from the group consisting of alkali metals, alkaline earth metals, zirconium, hafnium, aluminum, manganese, and zinc.

  2. Hafnium carbamates and ureates: new class of precursors for low-temperature growth of HfO2 thin films.

    PubMed

    Pothiraja, Ramasamy; Milanov, Andrian P; Barreca, Davide; Gasparotto, Alberto; Becker, Hans-Werner; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-04-21

    Novel volatile compounds of hafnium, namely tetrakis-N,O-dialkylcarbamato hafnium(iv) [Hf((i)PrNC(O)O(i)Pr)(4)] () and tetrakis-N,N,N'-trialkylureato hafnium(iv) [Hf((i)PrNC(O)N-(Me)Et)(4)] (), have been synthesized through the simple insertion reaction of isopropyl isocyanate into hafnium isopropoxide and hafnium ethylmethylamide, respectively; based on the promising thermal properties, compound has been evaluated as a precursor for metalorganic chemical vapor deposition (MOCVD) of HfO(2) thin films, which resulted in the growth of stoichiometric and crystalline layers with a uniform morphology at temperature as low as 250 degrees C.

  3. Slow DNA transport through nanopores in hafnium oxide membranes.

    PubMed

    Larkin, Joseph; Henley, Robert; Bell, David C; Cohen-Karni, Tzahi; Rosenstein, Jacob K; Wanunu, Meni

    2013-11-26

    We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2-7 nm thick) freestanding hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore.

  4. Radiochemical separation of zirconium and hafnium from other radionuclides.

    PubMed

    Hahn, R B

    1972-11-01

    Radiozirconium and radiohafnium may be separated from all other radionuclides except scandium and protactinium by precipitation with mandelic acid from 5-10 M hydrochloric acid, using commercial zirconyl chloride as carrier. Scandium and protactinium are removed by dissolving the precipitate in sodium carbonate, then adding barium nitrate to precipitate barium carbonate which acts as a scavenger. Zirconium mandelate is finally reprecipitated and the sample weighed and counted in this form. The method was checked by analysing commercial zirconyl chloride and standard rock samples for zirconium and hafnium by neutron-activation analysis.

  5. Radiochemical separation of zirconium and hafnium from other radionuclides.

    PubMed

    Hahn, R B

    1972-11-01

    Radiozirconium and radiohafnium may be separated from all other radionuclides except scandium and protactinium by precipitation with mandelic acid from 5-10 M hydrochloric acid, using commercial zirconyl chloride as carrier. Scandium and protactinium are removed by dissolving the precipitate in sodium carbonate, then adding barium nitrate to precipitate barium carbonate which acts as a scavenger. Zirconium mandelate is finally reprecipitated and the sample weighed and counted in this form. The method was checked by analysing commercial zirconyl chloride and standard rock samples for zirconium and hafnium by neutron-activation analysis. PMID:18961201

  6. Hafnium carbide structural foams synthesized from polymer precursors

    NASA Astrophysics Data System (ADS)

    Fan, Haibo

    2005-11-01

    A study was conducted to investigate a new low cost approach to produce Hafnium Carbide (HfC) structural foams through the thermolysis and pyrolysis of polymer precursors. Hafnium carbide has a melting point of over 3900 °C, the highest melting point of any known binary alloy. HfC structural foams can be fabricated into high temperature components or used as a thermal insulation material. Current available methods for creating HfC structural foams are time consuming, expensive or the material produced lacks mechanical strength. The objectives of this research were to produce HfC foam through the thermolysis and pyrolysis of Hf containing polymer mixture, optimize the properties of the HfC foam, and develop a knowledge base of acceptable process parameters. With the proposed method, HfC foam was produced by mixing a hafnium containing Macromolecular Metal Complex (MMC) and carbon source polymers, followed by heat treating the mixture under vacuum. XRD analysis showed that the produced foam was largely composed of HfC, with small amounts of hafnium oxide. The foam total porosity was measured to be over 85%. The HfC lattice parameter was found to range from 0.4613 nm to 0.4647 nm. The HfC conversion mechanism was investigated using Residual Gas Analysis, where it was observed that polymer decomposition occurred from 80 through 550 °C and HfC conversion started around 1100 °C. The HfC foam mechanical properties and microstructure were improved by optimizing the process methods and parameters. The initial research yielded an HfC foam with a compression strength of 15.16 +/- 4.66 MPa and evenly distributed foam cells with diameter sizes up to 50 mum. Continued research showed that HfC foams with total porosity of about 85% (density 1.9g/cm 3), and a foam compression strength of 212 +/- 25MPa were achievable. The proposed methodology for synthesizing HfC foam was found to be simple, inexpensive and require less production time. The process can be controlled to produce

  7. Slow DNA Transport through Nanopores in Hafnium Oxide Membranes

    PubMed Central

    Bell, David C.; Cohen-Karni, Tzahi; Rosenstein, Jacob K.; Wanunu, Meni

    2016-01-01

    We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2–7 nm thick) free-standing hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

  8. The abundances of zirconium and hafnium in the solar system

    NASA Technical Reports Server (NTRS)

    Ganapathy, R.; Papia, G. M.; Grossman, L.

    1976-01-01

    The concentrations of zirconium and hafnium have been determined in the Orgueil, Murchison, Allende, Bruderheim, and Alais meteorites by radiochemical neutron activation analysis. The mean Zr/Hf weight ratio in the first four of these meteorites is 31.3 (plus or minus 2.2), indicating no major fractionation of Zr from Hf. Alais contains anomalously high amounts of many refractory lithophile elements, including Zr and Hf. Orgueil contains 3.1 ppm Zr and 0.11 ppm Hf, corresponding to 9.0 and 0.16 atoms, respectively, relative to 1 million Si atoms.

  9. Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

    USGS Publications Warehouse

    Greenland, L.P.

    1968-01-01

    A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF3 and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; 233Pa and 95Zr contaminants in the hafnium fraction are resolved by ??-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported. ?? 1968.

  10. Zirconium and hafnium Salalen complexes in isospecific polymerisation of propylene.

    PubMed

    Press, Konstantin; Venditto, Vincenzo; Goldberg, Israel; Kol, Moshe

    2013-07-01

    The activity of dibenzylzirconium and dibenzylhafnium Salalen complexes in polymerisation of propylene with MAO as a cocatalyst is described. Three Salalen ligand precursors combining a bulky alkyl group (1-adamantyl) on the imine-side phenol and electron withdrawing halo groups of different sizes on the amine-side phenol were explored. All metal complexes were obtained as single diastereomers. An X-ray crystallographic structure of a hafnium complex of an additional ligand carrying the combination of tert-butyl and chloro substituted phenolates, 4-Hf, revealed a fac-mer wrapping of the Salalen ligand around the metal centre. All complexes led to active catalysts in propylene polymerisation and to isotactic polypropylene of high regioregularity. The zirconium complexes led to polypropylene having molecular weights of Mw = 132,000-200,000 and isotacticities of [mmmm] = 65.7-75.0%. The hafnium complexes led to polypropylene of higher molecular weights of Mw = 375,000-520,000 and higher stereoregularities of [mmmm] = 80.6-89.3%, the highest isotacticity obtained with 3-Hf.

  11. "Thermal Stability of Anodic Hafnium Oxide Nanotube Arrays"

    SciTech Connect

    Qiu, Xiaofeng; Howe, Jane Y; Mayer, Harry A; Paranthaman, Mariappan Parans; Tuncer, Enis

    2011-01-01

    Thermal stability of highly ordered Hafnium oxide, HfO2 nanotube arrays prepared through electrochemical anodization approach in the presence of ammonium fluoride is investigated in a temperature range of room temperature to 900 C in flowing Argon atmosphere. The formation of the HfO2 nanotube arrays was monitored by current density transient characteristics during anodization of hafnium metal foil. Morphologies of the as grown and post-annealed HfO2 nanotube arrays were analyzed by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Although monoclinic HfO2 is thermally stable up to 2000K in bulk, the morphology HfO2 nanotube arrays degraded at 900 C. Detailed X-ray photoelectron spectroscopy (XPS) study revealed that the thermal treatment significantly impact the composition and chemical environment of the core elements (Hf, O and F) of HfO2. Possible reasons for the degradation of the nanotube morphology were discussed based on XPS study and possible future improvements were suggested briefly.

  12. Atomic layer deposition and characterization of hafnium oxide grown on silicon from tetrakis(diethylamino)hafnium and water vapor

    SciTech Connect

    Deshpande, Anand; Inman, Ronald; Jursich, Gregory; Takoudis, Christos

    2004-09-01

    In this work thin films of hafnium oxide are deposited on Si(100) substrates by means of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and water vapor at substrate temperatures of 250-350 deg. C. Our system capabilities include fast transient delivery of reactive fluids, real-time vapor phase detection (in situ tunable diode laser hygrometer), precursor thermochemical capabilities, and ppt level elemental analysis by inductive coupling plasma mass spectrometry. The composition, purity, and other properties of the films and resulting interfaces are determined using x-ray and Fourier transform infrared spectroscopies, Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope with A scale resolution, and spectroscopic ellipsometry. The observed ALD rate is {approx}1.4 A per cycle. The nonuniformity across the film is less than 4%. Negligible carbon contamination is found in the resulting stoichiometric films under all conditions studied. The pulse sequence was optimized to prevent disastrous particulate problems while still minimizing purge times. The film deposition is investigated as a function of substrate temperature and reagent pulsing characteristics. A mild inverse temperature dependence of the ALD rate is observed. The initial stage of the HfO{sub 2} growth is investigated in detail.

  13. Enrichment/isolation of phosphorylated peptides on hafnium oxide prior to mass spectrometric analysis.

    PubMed

    Rivera, José G; Choi, Yong Seok; Vujcic, Stefan; Wood, Troy D; Colón, Luis A

    2009-01-01

    Hafnium oxide (hafnia) exhibits unique enrichment properties towards phosphorylated peptides that are complementary to those of titanium oxide (titania) and zirconium oxide (zirconia) for use with mass spectrometric analysis in the field of proteomics.

  14. PROCESS OF RECOVERING ZIRCONIUM VALUES FROM HAFNIUM VALUES BY SOLVENT EXTRACTION WITH AN ALKYL PHOSPHATE

    DOEpatents

    Peppard, D.F.

    1960-02-01

    A process of separating hafnium nitrate from zirconium nitrate contained in a nitric acid solution by selectively. extracting the zirconium nitrate with a water-immiscible alkyl phosphate is reported.

  15. Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier

    SciTech Connect

    Yu, Y.Y.; Kim, D.S.; Char, K.

    2004-12-01

    We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.

  16. Sulfide Mineralogy and Geochemistry

    NASA Astrophysics Data System (ADS)

    Dilles, John

    2007-02-01

    Reviews in Mineralogy and Geochemistry Series, Volume 61 David J. Vaughan, Editor Geochemical Society and Mineralogical Society of America; ISBN 0-939950-73-1 xiii + 714 pp.; 2006; $40. Sulfide minerals as a class represent important minor rock-forming minerals, but they are generally known as the chief sources of many economic metallic ores. In the past two decades, sulfide research has been extended to include important roles in environmental geology of sulfide weathering and resultant acid mine drainage, as well as in geomicrobiology in which bacteria make use of sulfides for metabolic energy sources. In the latter respect, sulfides played an important role in early evolution of life on Earth and in geochemical cycling of elements in the Earth's crust and hydrosphere.

  17. Dose estimate of inhaled hafnium tritide using the ICRP 66 lung model.

    PubMed

    Cheng, Yung-Sung; Zhou, Yue; Wang, Yang-Sheng; Inkret, William C; Wermer, Joseph R

    2002-06-01

    Metal tritide is widely used for research, purification, compression, and storage of tritium. The current understanding of metal tritide and its radiation dosimetry for internal exposure is limited, and ICRP publications do not provide the tritium dosimetry for hafnium tritide. The current radiation protection guidelines for metal tritide particles (including hafnium tritide) are based on the assumption that their biological behavior is similar to tritiated water, which is completely absorbed by the body. However, the solubility of metal tritide particles depends on the chemical form of the material. The biological half-live of hafnium tritide particles and the dosimetry of an inhalation exposure to those particles could be quite different from tritiated water. This paper describes experiments on the dissolution rate of hafnium tritide particles in a simulated lung fluid. The results showed that less than 1% of the tritium was dissolved in the simulated lung fluid for hafnium tritide particles after 215 d. The short-term and long-term dissolution half times were 46 and 4.28 x 10(5) d, respectively. This indicates that hafnium tritide is an extremely insoluble material. Self-absorption of beta rays in the hafnium tritide particles was estimated by a numerical method. The dose coefficients were calculated as a function of particle size using in vitro solubility data and a calculated self-absorption factor. The dose coefficient decreased with aerodynamic diameters in the range of 0.25 to 10 microm, mainly because the self-absorption factor decreased with increasing particle size. For a particle 1 microm in aerodynamic diameter, the dose coefficient of a hafnium tritide particle was about 10 times higher than that of tritiated water but was about 1.4 times lower than that calculated by ICRP Publication 71 for Type S tritiated particles. The ICRP estimate did not include a self-absorption factor and thus might have overestimated the dose. This finding has significant

  18. Determination of hafnium by neutron activation, and variation in the Zr/Hf ratio of some granite masses.

    PubMed

    Esson, J; Hahn-Weinheimer, P; Johanning, H

    1968-11-01

    A fairly quick method for the separation of hafnium from irradiated rock samples is described and results of the hafnium determinations are reported. The distribution of zirconium and hafnium and the variation of the Zr/Hf ratio in three calc-alkali granite masses are discussed. Reasons are suggested for the observed decrease in the Zr/Hf ratio during the crystallization of igneous rocks.

  19. Growth mode evolution of hafnium oxide by atomic layer deposition

    SciTech Connect

    Nie, Xianglong; Ma, Fei; Ma, Dayan; Xu, Kewei

    2014-01-15

    HfO{sub 2} thin films were deposited using tetrakis-ethylmethylamido hafnium and H{sub 2}O as precursors on silicon by atomic layer deposition (ALD). The morphology and microstructures at different ALD cycles were characterized by atomic force microscopy and high-resolution transmission electron microscopy. Based on the height–height correlation function and power spectral density function, quantitative analysis of surface morphologies was performed. Three characteristic dimensions (ξ{sub 1}, ξ{sub 2}, and ξ{sub 3}) corresponding to three surface structures, islands, local and global fluctuations, were identified. The evolution of ALD growth mode at range of the three critical scales was investigated, respectively. It suggests the transformation of growth mode from quasi two-dimensional layer-by-layer to three-dimensional island for global fluctuations.

  20. Hafnium and Neodymium Isotopes in Atlantic Ocean Waters

    NASA Astrophysics Data System (ADS)

    Rickli, J.; Frank, M.; Halliday, A.

    2007-12-01

    Neodymium isotopic compositions (ICs) have been established as a tracer of water masses in the present and past oceans since the late 1970s. Hafnium isotopes share the capability of tracing water masses and in combination with Nd isotopes provide information on continental weathering regimes. Whereas Nd released during weathering reflects the bulk Nd IC of the weathered lithology, the released Hf is more radiogenic than the weathered lithology. This effect is due to highly variable Lu/Hf--ratios in rock--forming minerals ("zircon effect") and as a consequence physical weathering apparently leads to more congruent weathering of Hf than chemical weathering does. Our understanding of the Hf IC of seawater to date has been derived (with the exception of some as yet unpublished data from the Arctic and Pacific oceans (Zimmermann et al., in prep.)) from ferromanganese crusts and nodules, since Hf concentrations in seawater are low and have until recently hampered direct measurements of Hf IC of seawater. We present IC for the dissolved Hf and Nd in Atlantic seawater. Samples were taken mainly on a transect from the Bay of Biscay to Cape Town (RV Polarstern cruise ANT XXIII/1 in 2005). A few additional samples are from the Labrador Sea and the Drake Passage. Hafnium and Nd were pre--concentrated by iron co--precipitation from 60 to 140 liters of filtered (0.45 μm) seawater. Separation of Hf and Nd followed previously established ion chromatographic procedures. Hafnium and Nd ICs were measured by MC--ICPMS (Nu Plasma) with a 2σ external reproducibility of 0.65 and 0.3 ǎrepsilon--units, respectively. Sample sizes varied but were in most cases larger than 3ng of Hf. Surface seawater as well as deep water samples extending to ~5,000 m, plot on the "seawater array" defined previously from measurements of ferromanganese crusts and nodules. Surface seawater ICs are quite uniform for Hf ranging from ǎrepsilonHf = 0 to +2 at most sampling sites on the Atlantic transect. In the

  1. Fractionation of zirconium and hafnium during processes of mantle metasomatism

    NASA Astrophysics Data System (ADS)

    Kogarko, L. N.

    2016-06-01

    For the first time, fractionation of zirconium and hafnium in carbonatized mantle xenoliths from the eastern Antarctic has been studied. An elevation relative to the chondrite values of Zr/Hf in the metasomatized xenoliths has been revealed. The main reactions of the carbonate metasomatism lead to replacement of primary orthopyroxene by secondary clinopyroxene. A substantial broadening of the clinopyroxene crystallization field results in an increase of Zr/Hf in an equilibrated melt due to a higher partition coefficient of Hf in clinopyroxene, relative to that of Zr. Migration of reaction-active carbonate and carbonate-silicate melts, equilibrated to metasomatic wehrlite, causes an increase in the Zr/Hf value in the carbonatized mantle substrate.

  2. Processing and characterization of boron carbide-hafnium diboride ceramics

    NASA Astrophysics Data System (ADS)

    Brown-Shaklee, Harlan James

    Hafnium diboride based ceramics are promising candidate materials for advanced aerospace and nuclear reactor components. The effectiveness of boron carbide and carbon as HfB2 sintering additives was systematically evaluated. In the first stage of the research, boron carbide and carbon additives were found to improve the densification behavior of milled HfB2 powder in part by removing oxides at the HfB2 surface during processing. Boron carbide additives reduced the hot pressing temperature of HfB2 by 150°C compared to carbon, which reduced the hot pressing temperature by ˜50°C. Reduction of oxide impurities alone could not explain the difference in sintering enhancement, however, and other mechanisms of enhancement were evaluated. Boron carbides throughout the homogeneity range were characterized to understand other mechanisms of sintering enhancement in HfB2. Heavily faulted carbon rich and boron rich boron carbides were synthesized for addition to HfB2. The greatest enhancement to densification was observed in samples containing boron- and carbon-rich compositions whereas B6.5 C provided the least enhancement to densification. It is proposed that carbon rich and boron rich boron carbides create boron and hafnium point defects in HfB2, respectively, which facilitate densification. Evaluation of the thermal conductivity (kth) between room temperature and 2000°C suggested that the stoichiometry of the boron carbide additives did not significantly affect kth of HfB2-BxC composites. The improved sinterability and the high kth (˜110 W/m-K at 300K and ˜90 W/m-K at 1000°C ) of HfB2-BxC ceramics make them excellent candidates for isotopically enriched reactor control materials.

  3. RF sputtered silicon and hafnium nitrides: Properties and adhesion to 440C stainless steel

    NASA Technical Reports Server (NTRS)

    Grill, A.; Aron, P. R.

    1982-01-01

    Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or - 100 kg/sq mm was measured for hafnium nitride and 3900 + or - 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.

  4. RF-sputtered silicon and hafnium nitrides - Properties and adhesion to 440C stainless steel

    NASA Technical Reports Server (NTRS)

    Grill, A.; Aron, P. R.

    1983-01-01

    Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or 100 kg/sq mm was measured for hafnium nitride and 3900 + or 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C.

  5. Thioarsenates in sulfidic waters.

    PubMed

    Stauder, S; Raue, B; Sacher, F

    2005-08-15

    It has long been recognized that the formation of soluble arsenic sulfur complexes plays a key role for the mobility and toxicity of arsenic in sulfate-reducing environments. Knowledge of the exact arsenic species is essential to understand the behavior of arsenic in sulfidic aquifers and to develop remediation strategies. In the past, monomeric and trimeric thioarsenites were assumed to be the existing species in sulfidic systems. In this study, thioarsenates were identified by IC-ICP/MS in arsenite- and sulfide-containing solutions as well as in a reduced groundwater from a contaminated site. The unexpected finding of an oxidation of As(lll) to As(V) in thioarsenates in strongly reducing systems can be explained by the high affinity between As(Ill) and sulfur. In sulfide-containing solutions without oxidant, As(lll) therefore undergoes disproportionation to thioarsenates (As(V)) and elemental arsenic. It has previously been supposed that mobility as well as toxicity of arsenic increases if the redox state decreases. For sulfidic waters, the opposite is probably the case. Thus, the formation of thioarsenates could be used in connection with remediation strategies. Thioarsenates are highly sensitive to oxygen and pH. This is important for analytical procedures. A loss of soluble arsenic as well as a conversion to arsenite and arsenate may occur if water samples containing thioarsenates are analyzed with conventional methods.

  6. Aqueous hafnium sulfate chemistry: structures of crystalline precipitates.

    PubMed

    Kalaji, Ali; Soderholm, L

    2014-10-20

    Crystalline precipitates resulting from the hydrolysis and subsequent condensation of Hf(IV) aqueous acidic solutions at 60-95 °C are examined and compared. By varying the concentrations of the acid and sulfate source, a variety of complex hafnium-oxo-hydroxo-sulfate clusters are isolated and structures accessed. Four novel compounds were discovered, while the structures of two known compounds, an 18-mer and a planar hexamer, were updated. In total, the compounds described herein each contain one of four cluster architectures: 18-mer, 11-mer, nonamer, and planar hexamer. In addition, one compound contains small amounts of 19-mers together with 18-mers. As well as examining the individual structure of each complex cluster, we relate them to one another, as well as to the dense phases of HfO2, to gain an understanding of their formation and stability. Finally, the solution conditions under which each cluster forms are identified by plotting the crystallization regions of each cluster against acidity and sulfate concentration. Most clusters form under slightly acidic conditions, in decreasing size as the sulfate concentration is raised. The flat hexamer is the single exception; it appears to require more acidic solutions. The degree of hydroxo- versus oxo-bridges with changing solution conditions is assessed within the broader context of the condensates. Of specific interest is the identification of these products as they relate to the use of hydrolysis reactions in designing new materials.

  7. Reinvestigation of high pressure polymorphism in hafnium metal

    SciTech Connect

    Pandey, K. K. Sharma, Surinder M.; Gyanchandani, Jyoti; Dey, G. K.; Somayazulu, M.; Sikka, S. K.

    2014-06-21

    There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known α→ω structural transition at 38 ± 8 GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51 GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature α→ω transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure P{sub o} = 44.5 GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the α and ω phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

  8. Reinvestigation of high pressure polymorphism in hafnium metal

    NASA Astrophysics Data System (ADS)

    Pandey, K. K.; Gyanchandani, Jyoti; Somayazulu, M.; Dey, G. K.; Sharma, Surinder M.; Sikka, S. K.

    2014-06-01

    There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known α→ω structural transition at 38 ± 8 GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51 GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature α→ω transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure Po = 44.5 GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the α and ω phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

  9. Hafnium oxide nanoparticles: toward an in vitro predictive biological effect?

    PubMed Central

    2014-01-01

    Background Hafnium oxide, NBTXR3 nanoparticles were designed for high dose energy deposition within cancer cells when exposed to ionizing radiation. The purpose of this study was to assess the possibility of predicting in vitro the biological effect of NBTXR3 nanoparticles when exposed to ionizing radiation. Methods Cellular uptake of NBTXR3 nanoparticles was assessed in a panel of human cancer cell lines (radioresistant and radiosensitive) by transmission electron microscopy. The radioenhancement of NBTXR3 nanoparticles was measured by the clonogenic survival assay. Results NBTXR3 nanoparticles were taken up by cells in a concentration dependent manner, forming clusters in the cytoplasm. Differential nanoparticle uptake was observed between epithelial and mesenchymal or glioblastoma cell lines. The dose enhancement factor increased with increase NBTXR3 nanoparticle concentration and radiation dose. Beyond a minimum number of clusters per cell, the radioenhancement of NBTXR3 nanoparticles could be estimated from the radiation dose delivered and the radiosensitivity of the cancer cell lines. Conclusions Our preliminary results suggest a predictable in vitro biological effect of NBTXR3 nanoparticles exposed to ionizing radiation. PMID:24981953

  10. Oxidation Effect in Octahedral Hafnium Disulfide Thin Film.

    PubMed

    Chae, Sang Hoon; Jin, Youngjo; Kim, Tae Soo; Chung, Dong Seob; Na, Hyunyeong; Nam, Honggi; Kim, Hyun; Perello, David J; Jeong, Hye Yun; Ly, Thuc Hue; Lee, Young Hee

    2016-01-26

    Atomically smooth van der Waals materials are structurally stable in a monolayer and a few layers but are susceptible to oxygen-rich environments. In particular, recently emerging materials such as black phosphorus and perovskite have revealed stronger environmental sensitivity than other two-dimensional layered materials, often obscuring the interesting intrinsic electronic and optical properties. Unleashing the true potential of these materials requires oxidation-free sample preparation that protects thin flakes from air exposure. Here, we fabricated few-layer hafnium disulfide (HfS2) field effect transistors (FETs) using an integrated vacuum cluster system and study their electronic properties and stability under ambient conditions. By performing all the device fabrication and characterization procedure under an oxygen- and moisture-free environment, we found that few-layer AA-stacking HfS2-FETs display excellent field effect responses (Ion/Ioff ≈ 10(7)) with reduced hysteresis compared to the FETs prepared under ambient conditions. Oxidation of HfS2 occurs uniformly over the entire area, increasing the film thickness by 250% at a prolonged oxidation time of >120 h, while defects on the surface are the preferential initial oxidation sites. We further demonstrated that the stability of the device in air is significantly improved by passivating FETs with BN in a vacuum cluster.

  11. Study of thin hafnium oxides deposited by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ganem, J.-J.; Trimaille, I.; Vickridge, I. C.; Blin, D.; Martin, F.

    2004-06-01

    We have deposited thin films (3.5, 7.5 and 22 nm) by atomic layer deposition (ALD) using HfCl 4 and H 2O precursors at 350 °C. Growth, thermal annealing and thermal reoxidation of the thin hafnium oxide layers under controlled ultra-dry oxygen atmosphere were studied using ion beam techniques and isotopic tracing experiments. Secondary ion mass spectroscopy (SIMS) profiling shows that the composition of deposited films is homogeneous with depth and over a large area. RBS and NRA show that the films are under-stoichiometric in oxygen and contain trace chlorine contamination, more pronounced at the film-substrate interface. After oxidation for 20 min in 100 mbar O 2 enriched to 99.9% in 18O at 425 °C, nuclear resonance depth-profiling using the 151 keV 18O(p,α) 15N narrow resonance, reveals that the main process occurring is exchange between oxygen from the gas and oxygen from the film matrix. However, following a post deposition vacuum or inert gas anneal, the atomic exchange process during thermal reoxidation, in 18O 2, is significantly inhibited and limited to the superficial region. We assume a link between this effect and the crystallization of the films previously reported.

  12. Sulfidation of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Levard, C.; Michel, F. M.; Brown, G. E.

    2010-12-01

    Rapid development of nanotechnologies that exploit the properties of silver nanoparticles (Ag-NPs) raises questions concerning the impact of Ag on the environment. Ag-NPs are currently among the most widely used in the nanotechnology industry and the amount released into the environment is expected to increase along with production (1). When present in geochemical systems, Ag-NPs may undergo a variety of changes due to varying redox, pH, and chemical conditions. Expected changes range from surface modification (e.g., oxidation, sulfidation, chloridation etc.) to complete dissolution and re-precipitation. In this context, the focus of our work is on understanding the behavior of synthetic Ag-NPs with different particle sizes under varying conditions relevant to the environment. Sulfidation of Ag-NPs is of particular interest since it among the processes most likely to occur in aqueous systems, in particular under reducing conditions. Three sizes of Ag-NPs coated with polyvinyl pyrrolidone were produced using the polyol process (2) (7 ±1; 20 ±4, and 40 ±9 nm). Batch solutions containing the different Ag-NPs were subsequently reacted with Na2S solutions of different concentrations. The sulfidation process was followed step-wise for 24 hours and the corrosion products formed were characterized by electron microscopy (TEM/SEM), diffraction (XRD), and photo-electron spectroscopy (XPS). Surface charge (pHPZC) of the products formed during this process was also measured, as were changes in solubility and reactivity. Based on experimental observations we infer that the sulfidation process is the result of dissolution-precipitation and find that: (i) acanthite (Ag2S) is formed as a corrosion product; (ii) Ag-NPs aggregation increased with sulfidation rate; (iii) pHPZC increases with the rate of sulfidation; and (iv) the solubility of the corrosion products formed from sulfidation appears lower than that of non-sulfidated Ag-NPs. We observe size-dependent differences in

  13. The Hot-Pressing of Hafnium Carbide (Melting Point, 7030 F)

    NASA Technical Reports Server (NTRS)

    Sanders, William A.; Grisaffe, Salvatore J.

    1960-01-01

    An investigation was undertaken to determine the effects of the hot-pressing variables (temperature, pressure, and time) on the density and grain size of hafnium carbide disks. The purpose was to provide information necessary for the production of high-density test shapes for the determination of physical and mechanical properties. Hot-pressing of -325 mesh hafnium carbide powder was accomplished with a hydraulic press and an inductively heated graphite die assembly. The ranges investigated for each variable were as follows: temperature, 3500 to 4870 F; pressure, 1000 to 6030 pounds per square inch; and time, 5 to 60 minutes. Hafnium carbide bodies of approximately 98 percent theoretical density can be produced under the following minimal conditions: 4230 F, 3500 pounds per square inch, and 15 minutes. Further increases in temperature and time resulted only in greater grain size.

  14. Electric quadrupole interaction of 100Rh in antimony, hafnium and rhenium

    NASA Astrophysics Data System (ADS)

    Kemp, W. J.; Abiona, A. A.; Kessler, P.; Timmers, H.

    2013-05-01

    Time differential perturbed angular correlation (TDPAC) spectroscopy in beryllium, zinc, rhodium, antimony, hafnium and rhenium was performed with the 100Pd/100Rh probe using four-detector arrays with relative detector orientations of 90° and 180°. The probe was synthesized using the 92Zr(12C,4n)100Pd fusion evaporation reaction, with evaporation residues recoiling into specimens of the metals. The quadrupole coupling constant for 100Rh has been determined for the first time for antimony, hafnium and rhenium, while results for the other elements agree with known values. The coupling constants for the measured hexagonal lattices of the period VI transition metals, hafnium and rhenium, show the same trend with increasing atomic number as those of period V.

  15. Cathodo- and photoluminescence increase in amorphous hafnium oxide under annealing in oxygen

    SciTech Connect

    Ivanova, E. V. Zamoryanskaya, M. V.; Pustovarov, V. A.; Aliev, V. Sh.; Gritsenko, V. A.; Yelisseyev, A. P.

    2015-04-15

    Cathodo- and photoluminescence of amorphous nonstoichiometric films of hafnium oxide are studied with the aim to verify the hypothesis that oxygen vacancies are responsible for the luminescence. To produce oxygen vacancies, hafnium oxide was enriched in surplus metal during synthesis. To reduce the oxygen concentration, the film was annealed in oxygen. A qualitative control of the oxygen concentration was carried out by the refractive index. In the initial, almost stoichiometric films we observed a 2.7-eV band in cathodoluminescence. Annealing in oxygen results in a considerable increase in its intensity, as well as in the appearance of new bands at 1.87, 2.14, 3.40, and 3.6 eV. The observed emission bands are supposed to be due to single oxygen vacancies and polyvacancies in hafnium oxide. The luminescence increase under annealing in an oxygen atmosphere may be a result of the emission quenching effect.

  16. Composition and microstructure of zirconium and hafnium germanates obtained by different chemical routes

    SciTech Connect

    Utkin, A.V. Prokip, V.E.; Baklanova, N.I.

    2014-01-15

    The phase composition and morphology of zirconium and hafnium germanates synthesized by ceramic and co-precipitation routes were studied. The products were characterized using high-temperature X-ray diffraction analysis (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and thermal (TG/DTA) analysis. To investigate the phase composition and stoichiometry of compounds the unit cell parameters were refined by full-profile Rietveld XRD analysis. The morphology of products and its evolution during high-temperature treatment was examined by SEM analysis. It was stated that there is the strong dependence of the phase composition and morphology of products on the preparation route. The ceramic route requires a multi-stage high-temperature treatment to obtain zirconium and hafnium germanates of 95% purity or more. Also, there are strong diffusion limitations to obtain hafnium germanate Hf{sub 3}GeO{sub 8} by ceramic route. On the contrary, the co-precipitation route leads to the formation of nanocrystalline single phase germanates of stoichiometric composition at a relatively low temperatures (less than 1000 °C). The results of quantitative XRD analysis showed the hafnium germanates are stoichiometric compounds in contrast to zirconium germanates that form a set of solid solutions. This distinction may be related to the difference in the ion radii of Zr and Hf. - Graphical abstract: The phase composition and morphology of zirconium and hafnium germanates synthesized by ceramic and co-precipitation routes were studied. It was stated that there is the strong dependence of the phase composition and morphology of products on the preparation route. Display Omitted - Highlights: • Zr and Hf germanates were synthesized by ceramic and co-precipitation routes. • The morphology of products depends on the synthesis parameters. • Zirconium germanates forms a set of solid solutions. • Hafnium germanates are stoichiometric compounds.

  17. SULFIDE METHOD PLUTONIUM SEPARATION

    DOEpatents

    Duffield, R.B.

    1958-08-12

    A process is described for the recovery of plutonium from neutron irradiated uranium solutions. Such a solution is first treated with a soluble sullide, causing precipitation of the plutoniunn and uraniunn values present, along with those impurities which form insoluble sulfides. The precipitate is then treated with a solution of carbonate ions, which will dissolve the uranium and plutonium present while the fission product sulfides remain unaffected. After separation from the residue, this solution may then be treated by any of the usual methods, such as formation of a lanthanum fluoride precipitate, to effect separation of plutoniunn from uranium.

  18. Effect of substrate temperature on structural and electrical properties of RF sputtered hafnium oxide thin films

    SciTech Connect

    Das, K. C.; Ghosh, S. P.; Tripathy, N.; Kar, J. P.; Bose, G.; Lee, T.; Myoung, J. M.

    2015-06-24

    In this work hafnium oxide thin films were deposited on p-type silicon substrate by Radio frequency magnetron sputtering at different substrate temperature ranging from room temperature to 300 °C. The structural and electrical properties of the sputtered films were investigated by x-ray diffraction, capacitance-voltage and current-voltage measurements. The XRD results show the formation monoclinic structure of the hafnium oxide thin films. The shifting of C-V curves towards negative voltage side depicts the increase in positive oxide charges with the rise of substrate temperature. Leakage current was found increased, when temperature enhanced from room temperature to 300 °C.

  19. Zinc sulfide liquefaction catalyst

    DOEpatents

    Garg, Diwakar

    1984-01-01

    A process for the liquefaction of carbonaceous material, such as coal, is set forth wherein coal is liquefied in a catalytic solvent refining reaction wherein an activated zinc sulfide catalyst is utilized which is activated by hydrogenation in a coal derived process solvent in the absence of coal.

  20. Cytotoxicity and physicochemical properties of hafnium oxide nanoparticles.

    PubMed

    Field, James A; Luna-Velasco, Antonia; Boitano, Scott A; Shadman, Farhang; Ratner, Buddy D; Barnes, Chris; Sierra-Alvarez, Reyes

    2011-09-01

    Nano-sized hafnium oxide (HfO(2)) particles are being considered for applications within the semiconductor industry. However, little is known about their cytotoxicity. The objective of this work was to assess several HfO(2) nanoparticles (NPs) samples for their acute cytotoxicity. Dynamic light scattering analysis of the samples indicated that the average particle size of the HfO(2) in aqueous dispersions was in the submicron range with a fraction of particles having nano-dimensions. The media used in the toxicity assays decreased or increased the average particle size of HfO(2) NPs due to dispersion or agglomeration. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed numerous surface contaminants on the NPs. Only one HfO(2) sample caused moderate cytotoxicity to human cell lines. The inhibitory sample caused a 50% response in the Live/Dead assay with HaCaT skin cells at 2200 mg L(-1); and a 50% response in the mitochondrial toxicity test at 300 mg L(-1). A microbial inhibition assay based on methanogenic activity also revealed that another HFO(2) sample caused moderate inhibition. The difference in toxicity between samples could not be attributed to size. Instead the difference in toxicity was likely due to differences in the contaminants of the HfO(2). The ToF-SIMS analysis indicated unique signatures of Br and P in the sample toxic to human cell lines suggesting a distinct synthesis was used for that sample which may have been accompanied by inhibitory impurities. The results taken as a whole indicate that HfO(2) itself is relatively non-toxic.

  1. A reconnaissance ion-probe of hafnium isotopes in zircons

    SciTech Connect

    Kinny, P.D.; Compston, W.; Williams, I.S. )

    1991-03-01

    A SIMS technique for the isotopic analysis of hafnium in zircons using the SHRIMP ion microprobe has been developed, and a precision of typically 0.5{per thousand} (2{sigma}) achieved in the mean reduced {sup 176}Hf/{sup 177}Hf ratio measured at several spots on a single grain. Unfractionated (chondritic) initial Hf isotopic compositions have been measured on a number of Archaean zircon populations. These include the oldest-known terrestrial minerals, the 4.2 Ga-old Mount Narryer detrital zircons, thereby confirming their antiquity. In contrast, positive initial {epsilon}{sub Hf} (relative to the chondritic model composition) has been found in several post-Archaean zircon populations, reflecting the increasing involvement of isotopically evolved depleted mantle sources in the formation of younger crust. The 570 Ma-old Sri Lankan zircon standard SL7 yielded an exceptionally low initial {epsilon}{sub Hf} of {minus}23, implying a metamorphic origin as a reworked product of ancient crust. SHRIMP U-Pb analyses of zircons from Archaean tonalitic gneiss at Watersmeet, Michigan, yield a precise crystallization age of 3636 {plus minus}6 Ma (2{sigma}), and show that a previously reported correlation between {sup 176}Hf/{sup 177}Hf and U-Pb isotopic discordance in bulk zircon samples (Patchett, 1983) was caused by the addition of radiogenic Hf in discrete overgrowths of new zircon ca. 2.7 Ga ago. The original 3.64 Ga grains show no evidence of distrubance to their original (chondritic) Hf isotopic composition. There is presently no evidence for significant isotopic exchange of Hf between zircon and other minerals in crustal rocks.

  2. Hafnium(IV) chloride complexes with chelating β-ketiminate ligands: Synthesis, spectroscopic characterization and volatility study.

    PubMed

    Patil, Siddappa A; Medina, Phillip A; Antic, Aleks; Ziller, Joseph W; Vohs, Jason K; Fahlman, Bradley D

    2015-09-01

    The synthesis and characterization of four new β-ketiminate hafnium(IV) chloride complexes dichloro-bis[4-(phenylamido)pent-3-en-2-one]-hafnium (4a), dichloro-bis[4-(4-methylphenylamido)pent-3-en-2-one]-hafnium (4b), dichloro-bis[4-(4-methoxyphenylamido)pent-3-en-2-one]-hafnium (4c), and dichloro-bis[4-(4-chlorophenylamido)pent-3-en-2-one]-hafnium (4d) are reported. All the complexes (4a-d) were characterized by spectroscopic methods ((1)H NMR, (13)C NMR, IR), and elemental analysis while the compound 4c was further examined by single-crystal X-ray diffraction, revealing that the complex is monomer with the hafnium center in octahedral coordination environment and oxygens of the chelating N-O ligands are trans to each other and the chloride ligands are in a cis arrangement. Volatile trends are established for four new β-ketiminate hafnium(IV) chloride complexes (4a-d). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that, the dependence of ΔHsub on the molecular weight (4a-c) and inductive effects from chlorine (4d).

  3. Hafnium(IV) chloride complexes with chelating β-ketiminate ligands: Synthesis, spectroscopic characterization and volatility study

    NASA Astrophysics Data System (ADS)

    Patil, Siddappa A.; Medina, Phillip A.; Antic, Aleks; Ziller, Joseph W.; Vohs, Jason K.; Fahlman, Bradley D.

    2015-09-01

    The synthesis and characterization of four new β-ketiminate hafnium(IV) chloride complexes dichloro-bis[4-(phenylamido)pent-3-en-2-one]-hafnium (4a), dichloro-bis[4-(4-methylphenylamido)pent-3-en-2-one]-hafnium (4b), dichloro-bis[4-(4-methoxyphenylamido)pent-3-en-2-one]-hafnium (4c), and dichloro-bis[4-(4-chlorophenylamido)pent-3-en-2-one]-hafnium (4d) are reported. All the complexes (4a-d) were characterized by spectroscopic methods (1H NMR, 13C NMR, IR), and elemental analysis while the compound 4c was further examined by single-crystal X-ray diffraction, revealing that the complex is monomer with the hafnium center in octahedral coordination environment and oxygens of the chelating N-O ligands are trans to each other and the chloride ligands are in a cis arrangement. Volatile trends are established for four new β-ketiminate hafnium(IV) chloride complexes (4a-d). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that, the dependence of ΔHsub on the molecular weight (4a-c) and inductive effects from chlorine (4d).

  4. The Effect of Aluminum Oxide Incorporation on the Material And Electrical Properties of Hafnium Oxide on Ge

    SciTech Connect

    Sawkar-Mathur, M.; Perng, Y.-C.; Lu, J.; Blom, H.-O.; Bargar, J.; Chang, J.P.

    2009-05-27

    Hafnium aluminate thin films were synthesized by atomic layer deposition (ALD) to assess the effect of aluminum oxide incorporation on the dielectric/Ge interfacial properties. In these Hf{sub x}Al{sub y}O{sub z} thin films, the Hf to Al cation ratio was effectively controlled by changing the ratio of hafnium oxide to aluminum oxide ALD cycles, while their short range order was changed upon increasing aluminum oxide incorporation, as observed by extended x-ray absorption fine structure analysis. The incorporation of aluminum oxide was shown to improve the electrical characteristics of hafnium oxide/Ge devices, including lower interface state densities and leakage current densities.

  5. The corrosion behavior of hafnium in high-temperature-water environments

    SciTech Connect

    Rishel, D.M.; Smee, J.D.; Kammenzind, B.F.

    1999-10-01

    The high-temperature-water corrosion performance of hafnium is evaluated. Corrosion kinetic data are used to develop correlations that are a function of time and temperature. The evaluation is based on corrosion tests conducted in out-of-pile autoclaves and in out-of-flux locations of the Advanced Test Reactor (ATR) at temperatures ranging from 288 to 360 C. Similar to the corrosion behavior of unalloyed zirconium, the high-temperature-water corrosion response of hafnium exhibits three corrosion regimes: pretransition, posttransition, and spalling. In the pretransition regime, cubic corrosion kinetics are exhibited, whereas in the posttransition regime, linear corrosion kinetics are exhibited. Because of the scatter in the spalling regime data, it is not reasonable to use a best fit of the data to describe spalling regime corrosion. Data also show that neutron irradiation does not alter the corrosion performance of hafnium. Finally, the data illustrate that the corrosion rate of hafnium is significantly less than that of Zircaloy-2 and Zircaloy-4.

  6. Measurement of L(III) Subshell Absorption Jump Parameters of Hafnium.

    PubMed

    Cengiz, E; Saritas, N; Dogan, M; Koksal, O K; Karabulut, K; Apaydin, G; Tirasoglu, E

    2015-12-01

    The L(III) subshell absorption jump ratio and jump factor of hafnium have been measured using two different ways which are X-ray attenuation method and Energy Dispersive X-ray Fluorescence technique. The results obtained both ways have been compared with theoretical values. They are in good agreement with each other.

  7. "Decarbonization" of an imino-N-heterocyclic carbene ligand via triple benzyl migration from hafnium.

    PubMed

    Prema, Dipesh; Mathota Arachchige, Yohan L N; Murray, Rex E; Slaughter, LeGrande M

    2015-04-21

    An imino-N-heterocyclic carbene underwent three sequential benzyl migrations upon reaction with tetrabenzylhafnium, resulting in complete removal of the carbene carbon from the ligand. The resulting eneamido-amidinato hafnium complex showed alkene polymerization activity comparable to that of a precatalyst containing the intact iminocarbene ligand.

  8. Synthesis, properties, and structure of potassium titanyl phosphate single crystals doped with hafnium

    SciTech Connect

    Orlova, E. I.; Kharitonova, E. P.; Novikova, N. E. Verin, I. A.; Alekseeva, O. A.; Sorokina, N. I.; Voronkova, V. I.

    2010-05-15

    Single crystals of potassium titanyl phosphate doped with hafnium are grown by spontaneous flux crystallization. Their physical properties are studied, and the structure of three KTi{sub 1-x}Hf{sub x}OPO{sub 4} crystals (x = 0.01, 0.03, and 0.12) is determined. In the crystals studied, hafnium mostly occupies the second titanium position. The doping of KTP crystals with hafnium results in an elongation of K-O bonds in the potassium polyhedra and, as a consequence, in a considerable (by approximately 180 deg. C) decrease in the temperature of ferroelectric phase transition. The magnitude of anomalous permittivity substantially decreases. The electrical conduction in the specimens studied decreases by approximately half an order of magnitude in the low-temperature region but remains almost unchanged in the high-temperature region. Even at minor concentrations, the presence of a hafnium additive in the specimens considerably (by 35%) enhances the intensity of the second harmonic generation of laser radiation.

  9. Alkanephosphonates on hafnium-modified gold: a new class of self-assembled organic monolayers.

    PubMed

    Jespersen, Michael L; Inman, Christina E; Kearns, Gregory J; Foster, Evan W; Hutchison, James E

    2007-03-14

    A new method for assembling organic monolayers on gold is reported that employs hafnium ions as linkers between a phosphonate headgroup and the gold surface. Monolayers of octadecylphosphonic acid (ODPA) formed on gold substrates that had been pretreated with hafnium oxychloride are representative of this new class of organic thin films. The monolayers are dense enough to completely block assembly of alkanethiols and resist displacement by alkanethiols. The composition and structure of the monolayers were investigated by contact angle goniometry, XPS, PM-IRRAS, and TOF-SIMS. From these studies, it was determined that this assembly strategy leads to the formation of ODPA monolayers similar in quality to those typically formed on metal oxide substrates. The assembly method allows for the ready generation of patterned surfaces that can be easily prepared by first patterning hafnium on the gold surface followed by alkanephosphonate assembly. Using the bifunctional (thiol-phosphonate) 2-mercaptoethylphosphonic acid (2-MEPA), we show that this new assembly chemistry is compatible with gold-thiol chemistry and use TOF-SIMS to show that the molecule attaches through the phosphonate functionality in the patterned region and through the thiol in the bare gold regions. These results demonstrate the possibility of functionalizing metal substrates with monolayers typically formed on metal oxide surfaces and show that hafnium-gold chemistry is complementary and orthogonal to well-established gold-thiol assembly strategies.

  10. "Decarbonization" of an imino N-heterocyclic carbene via triple benzyl migration from hafnium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An imino N-heterocyclic carbene underwent three sequential benzyl migrations upon reaction with tetrabenzylhafnium, resulting in complete removal of the carbene carbon from the ligand. The resulting eneamido-amidinato hafnium complex showed alkene polymerization activity comparable to that of a prec...

  11. Electrochemical behavior of silver sulfide

    SciTech Connect

    Drouven, B.U.E.

    1982-01-01

    The electrochemical behavior of silver sulfide in sulfuric acid as well as in nitric acid was studied using electrodes made from synthetic silver sulfide. The primary techniques used were potentiostatic, potentiodynamic, galvanostatic and corrosion cell experiments. The cathodic reaction of silver sulfide produces silver and hydrogen sulfide. This reaction mechanism is a sequential two step charge transfer involving a single electron in each step. Silver ions are produced from silver sulfide upon applying an anodic potential. The dissolution rate of silver sulfide can be so high that the formation of silver sulfate occurs which partially covers the silver sulfide surface and inhibits a further rate increase. The sulfur from the silver sulfide will be oxidized at low overpotentials to elemental sulfur; at high overpotentials, the oxidation to sulfate or bisulfate is observed. The results suggest that the catalysis of chalcopyrite by the addition of silver ions is caused by the formation and subsequent dissolution of silver sulfide leaving a porous layer behind. The understanding of the reaction mechanism of silver sulfide dissolution and its optimization will significantly improve the economic evaluation of industrial processes using the catalyzed leaching of chalcopyrite. The present knowledge of the catalysis indicates that other ions may be substituted for silver ions which would increase the feasibility of hydrometallurgical processes.

  12. Sulfide detoxification in plant mitochondria.

    PubMed

    Birke, Hannah; Hildebrandt, Tatjana M; Wirtz, Markus; Hell, Rüdiger

    2015-01-01

    In contrast to animals, which release the signal molecule sulfide in small amounts from cysteine and its derivates, phototrophic eukaryotes generate sulfide as an essential intermediate of the sulfur assimilation pathway. Additionally, iron-sulfur cluster turnover and cyanide detoxification might contribute to the release of sulfide in mitochondria. However, sulfide is a potent inhibitor of cytochrome c oxidase in mitochondria. Thus, efficient sulfide detoxification mechanisms are required in mitochondria to ensure adequate energy production and consequently survival of the plant cell. Two enzymes have been recently described to catalyze sulfide detoxification in mitochondria of Arabidopsis thaliana, O-acetylserine(thiol)lyase C (OAS-TL C), and the sulfur dioxygenase (SDO) ethylmalonic encephalopathy protein 1 (ETHE1). Biochemical characterization of sulfide producing and consuming enzymes in mitochondria of plants is fundamental to understand the regulatory network that enables mitochondrial sulfide homeostasis under nonstressed and stressed conditions. In this chapter, we provide established protocols to determine the activity of the sulfide releasing enzyme β-cyanoalanine synthase as well as sulfide-consuming enzymes OAS-TL and SDO. Additionally, we describe a reliable and efficient method to purify OAS-TL proteins from plant material.

  13. Alloy 10 Al -- A new sulfidation and carburization resistant alloy for fuel combustion and conversion

    SciTech Connect

    Kloewer, J.; Sauthoff, G.; Letzig, D.

    1996-08-01

    A new nickel-base high-temperature alloy, alloy 10 Al, which contains 30% iron, 10% aluminum and 8% chromium, has been developed. Alloy 10 Al has a lamellar eutectic two-phase microstructure with one phase being the intermetallic phase NiAl and the second phase being Ni(Fe,Cr) solid solution. The high-temperature corrosion behavior of the new alloy has been determined in both air and hot process gases containing methane, sulfur dioxide and hydrogen sulfide, respectively. It was found that the corrosion resistance against carburization, sulfidation and oxidation was excellent due to the formation of a dense protective alumina scale. The adherence of the alumina scale was increased by an addition of 0.1% hafnium. The concentration of chromium was found to have a remarkable impact on oxidation and high temperature corrosion resistance. Alloys without chromium showed an increased corrosion rate in both air and sulfur-containing gas atmospheres due to the initial formation of nickel oxides. In sulfidizing gases at least 4% chromium are required to stabilize the formation of alumina and to prevent the formation of nickel/sulfur compounds.

  14. Geothermal hydrogen sulfide removal

    SciTech Connect

    Urban, P.

    1981-04-01

    UOP Sulfox technology successfully removed 500 ppM hydrogen sulfide from simulated mixed phase geothermal waters. The Sulfox process involves air oxidation of hydrogen sulfide using a fixed catalyst bed. The catalyst activity remained stable throughout the life of the program. The product stream composition was selected by controlling pH; low pH favored elemental sulfur, while high pH favored water soluble sulfate and thiosulfate. Operation with liquid water present assured full catalytic activity. Dissolved salts reduced catalyst activity somewhat. Application of Sulfox technology to geothermal waters resulted in a straightforward process. There were no requirements for auxiliary processes such as a chemical plant. Application of the process to various types of geothermal waters is discussed and plans for a field test pilot plant and a schedule for commercialization are outlined.

  15. Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; Titran, Robert H.

    1993-01-01

    The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

  16. Immobilization mechanisms of deoxyribonucleic acid (DNA) to hafnium dioxide (HfO2) surfaces for biosensing applications.

    PubMed

    Fahrenkopf, Nicholas M; Rice, P Zachary; Bergkvist, Magnus; Deskins, N Aaron; Cady, Nathaniel C

    2012-10-24

    Immobilization of biomolecular probes to the sensing substrate is a critical step for biosensor fabrication. In this work we investigated the phosphate-dependent, oriented immobilization of DNA to hafnium dioxide surfaces for biosensing applications. Phosphate-dependent immobilization was confirmed on a wide range of hafnium oxide surfaces; however, a second interaction mode was observed on monoclinic hafnium dioxide. On the basis of previous materials studies on these films, DNA immobilization studies, and density functional theory (DFT) modeling, we propose that this secondary interaction is between the exposed nucleobases of single stranded DNA and the surface. The lattice spacing of monoclinic hafnium dioxide matches the base-to-base pitch of DNA. Monoclinic hafnium dioxide is advantageous for nanoelectronic applications, yet because of this secondary DNA immobilization mechanism, it could impede DNA hybridization or cause nonspecific surface intereactions. Nonetheless, DNA immobilization on polycrystalline and amorphous hafnium dioxide is predominately mediated by the terminal phosphate in an oriented manner which is desirable for biosensing applications.

  17. Hydrogen sulfide intoxication.

    PubMed

    Guidotti, Tee L

    2015-01-01

    Hydrogen sulfide (H2S) is a hazard primarily in the oil and gas industry, agriculture, sewage and animal waste handling, construction (asphalt operations and disturbing marshy terrain), and other settings where organic material decomposes under reducing conditions, and in geothermal operations. It is an insoluble gas, heavier than air, with a very low odor threshold and high toxicity, driven by concentration more than duration of exposure. Toxicity presents in a unique, reliable, and characteristic toxidrome consisting, in ascending order of exposure, of mucosal irritation, especially of the eye ("gas eye"), olfactory paralysis (not to be confused with olfactory fatigue), sudden but reversible loss of consciousness ("knockdown"), pulmonary edema (with an unusually favorable prognosis), and death (probably with apnea contributing). The risk of chronic neurcognitive changes is controversial, with the best evidence at high exposure levels and after knockdowns, which are frequently accompanied by head injury or oxygen deprivation. Treatment cannot be initiated promptly in the prehospital phase, and currently rests primarily on supportive care, hyperbaric oxygen, and nitrite administration. The mechanism of action for sublethal neurotoxicity and knockdown is clearly not inhibition of cytochrome oxidase c, as generally assumed, although this may play a role in overwhelming exposures. High levels of endogenous sulfide are found in the brain, presumably relating to the function of hydrogen sulfide as a gaseous neurotransmitter and immunomodulator. Prevention requires control of exposure and rigorous training to stop doomed rescue attempts attempted without self-contained breathing apparatus, especially in confined spaces, and in sudden release in the oil and gas sector, which result in multiple avoidable deaths. PMID:26563786

  18. Field method for sulfide determination

    SciTech Connect

    Wilson, B L; Schwarser, R R; Chukwuenye, C O

    1982-01-01

    A simple and rapid method was developed for determining the total sulfide concentration in water in the field. Direct measurements were made using a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode connected to an Orion Model 407A/F Specific Ion Meter. The method also made use of a sulfide anti-oxidant buffer (SAOB II) which consists of ascorbic acid, sodium hydroxide, and disodium EDTA. Preweighed sodium sulfide crystals were sealed in air tight plastic volumetric flasks which were used in standardization process in the field. Field standards were prepared by adding SAOB II to the flask containing the sulfide crystals and diluting it to the mark with deionized deaerated water. Serial dilutions of the standards were used to prepare standards of lower concentrations. Concentrations as low as 6 ppB were obtained on lake samples with a reproducibility better than +- 10%.

  19. Chemical solution deposition of ferroelectric yttrium-doped hafnium oxide films on platinum electrodes

    SciTech Connect

    Starschich, S.; Griesche, D.; Schneller, T.; Böttger, U.; Waser, R.

    2014-05-19

    Ferroelectric hafnium oxide films were fabricated by chemical solution deposition with a remnant polarization of >13 μC/cm{sup 2}. The samples were prepared with 5.2 mol. % yttrium-doping and the thickness varied from 18 nm to 70 nm. The hafnium oxide layer was integrated into a metal-insulator-metal capacitor using platinum electrodes. Due to the processing procedure, no thickness dependence of the ferroelectric properties was observed. To confirm the ferroelectric nature of the deposited samples, polarization, capacitance, and piezoelectric displacement measurements were performed. However, no evidence of the orthorhombic phase was found which has been proposed to be the non-centrosymmetric, ferroelectric phase in HfO{sub 2}.

  20. Synthesis and characterization of hafnium oxide films for thermo and photoluminescence applications.

    PubMed

    Mendoza, J Guzmán; Frutis, M A Aguilar; Flores, G Alarcón; Hipólito, M García; Maciel Cerda, A; Azorín Nieto, J; Montalvo, T Rivera; Falcony, C

    2010-01-01

    Hafnium oxide (HfO(2)) films were deposited by the ultrasonic spray pyrolysis process. The films were synthesized from hafnium chloride as raw material in deionized water as solvent and were deposited on corning glass substrates at temperatures from 300 to 600 degrees C. For substrate temperatures lower than 400 degrees C the deposited films were amorphous, while for substrate temperatures higher than 450 degrees C, the monoclinic phase of HfO(2) appeared. Scanning electron microscopy showed that the film's surface resulted rough with semi-spherical promontories. The films showed a chemical composition close to HfO(2), with an Hf/O ratio of about 0.5. UV radiation was used in order to achieve the thermoluminescent characterization of the films; the 240 nm wavelength induced the best response. In addition, preliminary photoluminescence spectra, as a function of the deposition temperatures, are shown.

  1. Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

    SciTech Connect

    Pezzi, R.P.; Miotti, L.; Bastos, K.P.; Soares, G.V.; Driemeier, C.; Baumvol, I.J.R.; Punchaipetch, P.; Pant, G.; Gnade, B.E.; Wallace, R.M.; Rotondaro, A.; Visokay, J.M.; Chambers, J.J.; Colombo, L.

    2004-10-18

    Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in {sup 1}H- and {sup 2}H-containing atmospheres was investigated. {sup 1}H profiling was accessed by means of nuclear resonant reaction profiling, whereas {sup 2}H incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of {sup 1}H and {sup 2}H from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated {sup 1}H, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

  2. Dose assessment for inhaling hafnium particles based on laboratory rats study.

    PubMed

    Zhou, Y; Cheng, Y S

    2003-04-01

    Internal radiation from inhalation of hafnium tritide aerosols may be a significant radiation protection problem encountered by nuclear facility workers. Based on experimental results of the rat intratracheally instilled with hafnium tritide particles and on a self-absorption factor of beta particles determined by a numerical method, a biokinetic model was developed for inhaled particles of hafnium tritide. Results show that lung burdens of the tritide are well represented by a two-component exponential equation; biological half-lives derived for the retention of 3H in lung were 4.9 d and 1,257 d for the short- and long-term clearance, respectively. The tritium clearance rate via urine or feces was described by bi-phase exponential components. At the end of the experiment (180 d after instillation), only approximately 30% of the initial lung burden of 3H had been eliminated, of which approximately 98% was excreted via feces and 2% in urine, but none through exhaled air. Results also showed that a large percentage (70%) of the hafnium tritide initially present in lung still remained in the organ 6 mo after the exposure. The calculation of the radiation dose indicates that the cumulative dose to the lung directly from the tritide particles was approximately 10(6) times the lung dose from the dissolved tritium in the lung region. The committed effective dose to the lung was estimated to be 5.41 x 10(-10) Sv Bq(-1), which is over 99% of that to the whole body. The dose to the liver was 6.00 x 10(-15) Sv Bq(-1). This information will be useful in developing new guidelines for radiation protection purposes.

  3. Hafnium nitride buffer layers for growth of GaN on silicon

    DOEpatents

    Armitage, Robert D.; Weber, Eicke R.

    2005-08-16

    Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 {character pullout}m. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.

  4. On the phase formation of sputtered hafnium oxide and oxynitride films

    SciTech Connect

    Sarakinos, K.; Music, D.; Mraz, S.; Baben, M. to; Jiang, K.; Nahif, F.; Braun, A.; Zilkens, C.; Schneider, J. M.; Konstantinidis, S.; Renaux, F.; Cossement, D.; Munnik, F.

    2010-07-15

    Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O{sub 2}-N{sub 2} atmosphere. It is shown that the presence of N{sub 2} allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O{sub 2} partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O{sup -} ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O{sup -} ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O{sup -} ion flux without N{sub 2} addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO{sub 2} is independent from the O{sup -} bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO{sub 2} crystal structure at the expense of the monoclinic HfO{sub 2} one.

  5. CO assisted N2 functionalization activated by a dinuclear hafnium complex: a DFT mechanistic exploration.

    PubMed

    Ma, Xuelu; Zhang, Xin; Zhang, Wenchao; Lei, Ming

    2013-01-21

    In this paper, the reaction mechanisms of CO assisted N(2) cleavage and functionalization activated by a dinuclear hafnium complex are studied using a density function theory (DFT) method. Several key intermediates (Ia, Ib, Ic and Id) with axial/equatorial N=C=O coordination structures are found to be of importance along reaction pathways of CO assisted N(2) functionalization, which could provide a profound theoretical insight into the C-N bond formation and N-N bond cleavage. There are two different attack directions to insert the first CO molecule into the Hf-N bonds of the dinuclear hafnium complex, which lead to C-N bond formation. The calculated results imply that CO insertion into the Hf(1)-N(3) bond (Path A1) reacts more easily than that into the Hf(2)-N(3) bond (Path A3). But for the insertion of the second CO insertion to give 2A, there are two possibilities (Path A1 and Path A2) according to this insertion being after/before N-N bond cleavage. Two pathways (Path A1 and Path A2) are proved to be possible to form final dinitrogen functionalized products (oxamidide 2A, 2B and 2C) in this study, which explain the formation of different oxamidide isomers in CO assisted N(2) functionalization activated by a dinuclear hafnium complex.

  6. X-Ray diffraction study of KTiOPO{sub 4} single crystals doped with hafnium

    SciTech Connect

    Novikova, N. E. Verin, I. A.; Sorokina, N. I.; Alekseeva, O. A.; Orlova, E. I.; Voronkova, V. I.

    2011-05-15

    Single crystals of KTi{sub 1-x}Hf{sub x}OPO{sub 4} (x = 0.015(2), 0.035(1), and 0.128(1) are reinvestigated by precision X-ray diffraction at room temperature. It is found that the implantation of hafnium atoms in the crystal structure of KTiOPO{sub 4} does not lead to significant changes in the framework and affects only the positions of the potassium atoms in the channel. Our studies reveal the displacements of the potassium atoms from their main and additional positions in the structure of pure KTP in all three structures studied. The largest displacements from the K1 Prime and K1 Double-Prime additional positions are observed in the structure with x = 0.035. At this hafnium concentration, the occupancy of the main positions of potassium atoms decreases and the occupancy of the additional positions increases in relation to those in KTP. This redistribution of potassium atoms enhances the nonuniformity of distribution of the electron density in the vicinity of their positions, which is probably responsible for the increase in the nonlinear susceptibility of KTP crystals that contain 3.5% hafnium in relation to crystals of pure KTP.

  7. Radiation effects on the electrical properties of hafnium oxide based MOS capacitors.

    SciTech Connect

    Petrosky, J. C.; McClory, J. W.; Bielejec, Edward Salvador; Foster, J. C.

    2010-10-01

    Hafnium oxide-based MOS capacitors were investigated to determine electrical property response to radiation environments. In situ capacitance versus voltage measurements were analyzed to identify voltage shifting as a result of changes to trapped charge with increasing dose of gamma, neutron, and ion radiation. In situ measurements required investigation and optimization of capacitor fabrication to include dicing, cleaning, metalization, packaging, and wire bonding. A top metal contact of 200 angstroms of titanium followed by 2800 angstroms of gold allowed for repeatable wire bonding and proper electrical response. Gamma and ion irradiations of atomic layer deposited hafnium oxide on silicon devices both resulted in a midgap voltage shift of no more than 0.2 V toward less positive voltages. This shift indicates recombination of radiation induced positive charge with negative trapped charge in the bulk oxide. Silicon ion irradiation caused interface effects in addition to oxide trap effects that resulted in a flatband voltage shift of approximately 0.6 V also toward less positive voltages. Additionally, no bias dependent voltage shifts with gamma irradiation and strong oxide capacitance room temperature annealing after ion irradiation was observed. These characteristics, in addition to the small voltage shifts observed, demonstrate the radiation hardness of hafnium oxide and its applicability for use in space systems.

  8. Hafnium metallocene compounds used as cathode interfacial layers for enhanced electron transfer in organic solar cells.

    PubMed

    Park, Keunhee; Oh, Seungsik; Jung, Donggeun; Chae, Heeyeop; Kim, Hyoungsub; Boo, Jin-Hyo

    2012-01-09

    We have used hafnium metallocene compounds as cathode interfacial layers for organic solar cells [OSCs]. A metallocene compound consists of a transition metal and two cyclopentadienyl ligands coordinated in a sandwich structure. For the fabrication of the OSCs, poly[3,4-ethylenedioxythiophene]:poly(styrene sulfonate), poly(3-hexylthiophene-2,5-diyl) + 66-phenyl C61 butyric acid methyl ester, bis-(ethylcyclopentadienyl)hafnium(IV) dichloride, and aluminum were deposited as a hole transport layer, an active layer, a cathode interfacial layer, and a cathode, respectively. The hafnium metallocene compound cathode interfacial layer improved the performance of OSCs compared to that of OSCs without the interfacial layer. The current density-voltage characteristics of OSCs with an interfacial layer thickness of 0.7 nm and of those without an interfacial layer showed power conversion efficiency [PCE] values of 2.96% and 2.34%, respectively, under an illumination condition of 100 mW/cm2 (AM 1.5). It is thought that a cathode interfacial layer of an appropriate thickness enhances the electron transfer between the active layer and the cathode, and thus increases the PCE of the OSCs.

  9. Oxygen and nitrogen diffusion in α-hafnium from first principles

    SciTech Connect

    O'Hara, Andrew; Demkov, Alexander A.

    2014-05-26

    We use a combination of density functional theory and multistate diffusion formalism to analyze the diffusion of oxygen and nitrogen in technologically important hafnium metal. Comparing the local density approximation and the Perdew-Burke-Ernzerhof version of the generalized gradient approximation, we find that a better description of the hafnium lattice in the latter results in the correct sequence of stable and transition states for oxygen interstitials leading to essentially quantitative agreement with experiment. For oxygen diffusion, we find an isotropic temperature-dependent diffusion coefficient of D=0.082e{sup −2.04/k{sub B}T}cm{sup 2}s{sup −1} utilizing interstitial sites with hexahedral and octahedral coordination. For the diffusivity of nitrogen, we find that an additional stable interstitial site, the crowdion site, exists and that the diffusion coefficient is D=0.15e{sup −2.68/k{sub B}T}cm{sup 2}s{sup −1}. Our results also reproduce the experimental observation that nitrogen diffusivity is lower than that of oxygen in hafnium.

  10. Oxygen and nitrogen diffusion in α-hafnium from first principles

    NASA Astrophysics Data System (ADS)

    O'Hara, Andrew; Demkov, Alexander A.

    2014-05-01

    We use a combination of density functional theory and multistate diffusion formalism to analyze the diffusion of oxygen and nitrogen in technologically important hafnium metal. Comparing the local density approximation and the Perdew-Burke-Ernzerhof version of the generalized gradient approximation, we find that a better description of the hafnium lattice in the latter results in the correct sequence of stable and transition states for oxygen interstitials leading to essentially quantitative agreement with experiment. For oxygen diffusion, we find an isotropic temperature-dependent diffusion coefficient of D =0.082e-2.04/kBTcm2s-1 utilizing interstitial sites with hexahedral and octahedral coordination. For the diffusivity of nitrogen, we find that an additional stable interstitial site, the crowdion site, exists and that the diffusion coefficient is D =0.15e-2.68/kBTcm2s-1. Our results also reproduce the experimental observation that nitrogen diffusivity is lower than that of oxygen in hafnium.

  11. RF sputtered silicon and hafnium nitrides as applied to 440C steel

    NASA Technical Reports Server (NTRS)

    Grill, A.; Aron, P. R.

    1984-01-01

    Silicon nitride and hafnium nitride coatings were deposited on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. The coatings and the interface between the coating and substrate were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. Oxide was found at all interfaces with an interface width of at least 600 A for the oxidized substrates and at least 300 A for the unoxidized substrates. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C. Coatings of both nitrides deposited at 8 mtorr were found to have increased adhesion to both oxidized and unoxidized 440C over those deposited at 20 mtorr.

  12. The Relationship Between Local Order, Long Range Order, and Sub-Band-Gap Defects in Hafnium Oxide and Hafnium Silicate Films

    SciTech Connect

    Hill,D.; Bartynski, R.; Nguyen, N.; Davydov, A.; Chandler-Horowitz, D.; Frank, M.

    2008-01-01

    We have measured x-ray absorption spectra (XAS) at the oxygen K edge for hafnium oxide (HfO2) films grown by chemical vapor deposition (CVD) and atomic layer deposition (ALD), as well as for hafnium silicate (HfSiO) films grown by CVD. The XAS results are compared to x-ray diffraction (XRD) and spectroscopic ellipsometry (SE) data from the same films. Features characteristic of crystalline HfO2 are observed in the XAS spectra from all CVD-grown HfO2 films, even for a thickness of 5 nm where XRD is not sensitive. XAS and XRD spectra from the ALD-grown HfO2 films exhibit the signature of crystallinity only for films that are 20 nm or thicker. These characteristic XAS features are absent in all HfSiO films measured, which is consistent with their being amorphous. The appearance of these peaks in XAS and XRD is correlated with sub-band-gap absorption in the SE spectra, which appears to be intrinsic to crystalline HfO2 in the monoclinic phase.

  13. Volcanogenic Massive Sulfide Deposit Density

    USGS Publications Warehouse

    Mosier, Dan L.; Singer, Donald A.; Berger, Vladimir I.

    2007-01-01

    A mineral-deposit density model for volcanogenic massive sulfide deposits was constructed from 38 well-explored control areas from around the world. Control areas contain at least one exposed volcanogenic massive sulfide deposit. The control areas used in this study contain 150 kuroko, 14 Urals, and 25 Cyprus massive sulfide subtypes of volcanogenic massive sulfide deposits. For each control area, extent of permissive rock, number of exposed volcanogenic massive sulfide deposits, map scale, deposit age, and deposit density were determined. The frequency distribution of deposit densities in these 38 control areas provides probabilistic estimates of the number of deposits for tracts that are permissive for volcanogenic massive sulfide deposits-90 percent of the control areas have densities of 100 or more deposits per 100,000 square kilometers, 50 percent of the control areas have densities of 700 or more deposits per 100,000 square kilometers, and 10 percent of the control areas have densities of 3,700 or more deposits per 100,000 square kilometers. Both map scale and the size of the control area are shown to be predictors of deposit density. Probabilistic estimates of the number of volcanogenic massive sulfide deposits can be made by conditioning the estimates on sizes of permissive area. The model constructed for this study provides a powerful tool for estimating the number of undiscovered volcanogenic massive sulfide deposits when conducting resource assessments. The value of these deposit densities is due to the consistency of these models with the grade and tonnage and the descriptive models. Mineral-deposit density models combined with grade and tonnage models allow reasonable estimates of the number, size, and grades of volcanogenic massive sulfide deposits to be made.

  14. A novel method for improving cerussite sulfidization

    NASA Astrophysics Data System (ADS)

    Feng, Qi-cheng; Wen, Shu-ming; Zhao, Wen-juan; Cao, Qin-bo; Lü, Chao

    2016-06-01

    Evaluation of flotation behavior, solution measurements, and surface analyses were performed to investigate the effects of chloride ion addition on the sulfidization of cerussite in this study. Micro-flotation tests indicate that the addition of chloride ions prior to sulfidization can significantly increase the flotation recovery of cerussite, which is attributed to the formation of more lead sulfide species on the mineral surface. Solution measurement results suggest that the addition of chloride ions prior to sulfidization induces the transformation of more sulfide ions from pulp solution onto the mineral surface by the formation of more lead sulfide species. X-ray diffraction and energy-dispersive spectroscopy indicate that more lead sulfide species form on the mineral surface when chloride ions are added prior to sulfidization. These results demonstrate that the addition of chloride ions prior to sulfidization can significantly improve the sulfidization of cerussite, thereby enhancing the flotation performance.

  15. Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

    PubMed

    Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

    2012-04-01

    The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 μm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (μ: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.

  16. Prevention of sulfide oxidation in sulfide-rich waste rock

    NASA Astrophysics Data System (ADS)

    Nyström, Elsa; Alakangas, Lena

    2015-04-01

    The ability to reduce sulfide oxidation in waste rock after mine closure is a widely researched area, but to reduce and/or inhibit the oxidation during operation is less common. Sulfide-rich (ca 30 % sulfur) waste rock, partially oxidized, was leached during unsaturated laboratory condition. Trace elements such as As and Sb were relatively high in the waste rock while other sulfide-associated elements such as Cu, Pb and Zn were low compared to common sulfide-rich waste rock. Leaching of unsaturated waste rock lowered the pH, from around six down to two, resulting in continuously increasing element concentrations during the leaching period of 272 days. The concentrations of As (65 mg/L), Cu (6.9 mg/L), Sb (1.2 mg/L), Zn (149 mg/L) and S (43 g/L) were strongly elevated at the end of the leaching period. Different alkaline industrial residues such as slag, lime kiln dust and cement kiln dust were added as solid or as liquid to the waste rock in an attempt to inhibit sulfide oxidation through neo-formed phases on sulfide surfaces in order to decrease the mobility of metals and metalloids over longer time scale. This will result in a lower cost and efforts of measures after mine closure. Results from the experiments will be presented.

  17. Apparatus for use in sulfide chemiluminescence detection

    DOEpatents

    Spurlin, S.R.; Yeung, E.S.

    1987-01-06

    A method is described for chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction. 4 figs.

  18. Apparatus for use in sulfide chemiluminescence detection

    DOEpatents

    Spurlin, Stanford R.; Yeung, Edward S.

    1987-01-01

    A method of chemiluminescently determining a sulfide which is either hydrogen sulfide or methyl mercaptan by reacting the sulfide with chlorine dioxide at low pressure and under conditions which allow a longer reaction time in emission of a single photon for every two sulfide containing species, and thereafter, chemiluminescently detecting and determining the sulfide. The invention also relates not only to the detection method, but the novel chemical reaction and a specifically designed chemiluminescence detection cell for the reaction.

  19. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example.

  20. Sulfide-mediated dehydrative glycosylation.

    PubMed

    Nguyen, H M; Chen, Y; Duron, S G; Gin, D Y

    2001-09-12

    The development of a new method for glycosylation with 1-hydroxy glycosyl donors employing dialkyl sulfonium reagents is described. The process employs the reagent combination of a dialkyl sulfide and triflic anhydride to effect anomeric bond constructions. This controlled dehydrative coupling of various C(1)-hemiacetal glycosyl donors and nucleophilic acceptors proceeds by way of a sulfide-to-sulfoxide oxidation process in which triflic anhydride serves as the oxidant.

  1. Chemical Bonding in Sulfide Minerals

    SciTech Connect

    Vaughan, David J.; Rosso, Kevin M.

    2006-08-01

    An understanding of chemical bonding and electronic structure in sulfide minerals is central to any attempt at understanding their crystal structures, stabilities and physical properties. It is also an essential precursor to understanding reactivity through modeling surface structure at the molecular scale. In recent decades, there have been remarkable advances in first principles (ab initio) methods for the quantitative calculation of electronic structure. These advances have been made possible by the very rapid development of high performance computers. Several review volumes that chart the applications of these developments in mineralogy and geochemistry are available (Tossell and Vaughan, 1992; Cygan and Kubicki, 2001). An important feature of the sulfide minerals is the diversity of their electronic structures, as evidenced by their electrical and magnetic properties (see Pearce et al. 2006, this volume). Thus, sulfide minerals range from insulators through semiconductors to metals, and exhibit every type of magnetic behavior. This has presented problems for those attempting to develop bonding models for sulfides, and also led to certain misconceptions regarding the kinds of models that may be appropriate. In this chapter, chemical bonding and electronic structure models for sulfides are reviewed with emphasis on more recent developments. Although the fully ab initio quantitative methods are now capable of a remarkable degree of sophistication in terms of agreement with experiment and potential to interpret and predict behavior with varying conditions, both qualitative and more simplistic quantitative approaches will also be briefly discussed. This is because we believe that the insights which they provide are still helpful to those studying sulfide minerals. In addition to the application of electronic structure models and calculations to solid sulfides, work on sulfide mineral surfaces (Rosso and Vaughan 2006a,b) and solution complexes and clusters (Rickard

  2. Hydrogen Sulfide Oxidation by Myoglobin.

    PubMed

    Bostelaar, Trever; Vitvitsky, Victor; Kumutima, Jacques; Lewis, Brianne E; Yadav, Pramod K; Brunold, Thomas C; Filipovic, Milos; Lehnert, Nicolai; Stemmler, Timothy L; Banerjee, Ruma

    2016-07-13

    Enzymes in the sulfur network generate the signaling molecule, hydrogen sulfide (H2S), from the amino acids cysteine and homocysteine. Since it is toxic at elevated concentrations, cells are equipped to clear H2S. A canonical sulfide oxidation pathway operates in mitochondria, converting H2S to thiosulfate and sulfate. We have recently discovered the ability of ferric hemoglobin to oxidize sulfide to thiosulfate and iron-bound hydropolysulfides. In this study, we report that myoglobin exhibits a similar capacity for sulfide oxidation. We have trapped and characterized iron-bound sulfur intermediates using cryo-mass spectrometry and X-ray absorption spectroscopy. Further support for the postulated intermediates in the chemically challenging conversion of H2S to thiosulfate and iron-bound catenated sulfur products is provided by EPR and resonance Raman spectroscopy in addition to density functional theory computational results. We speculate that the unusual sensitivity of skeletal muscle cytochrome c oxidase to sulfide poisoning in ethylmalonic encephalopathy, resulting from the deficiency in a mitochondrial sulfide oxidation enzyme, might be due to the concentration of H2S by myoglobin in this tissue. PMID:27310035

  3. Strong influence of polymer architecture on the microstructural evolution of hafnium-alkoxide-modified silazanes upon ceramization.

    PubMed

    Papendorf, Benjamin; Nonnenmacher, Katharina; Ionescu, Emanuel; Kleebe, Hans-Joachim; Riedel, Ralf

    2011-04-01

    The present study focuses on the synthesis and ceramization of novel hafnium-alkoxide-modified silazanes as well as on their microstructure evolution at high temperatures. The synthesis of hafnia-modified polymer-derived SiCN ceramic nanocomposites is performed via chemical modification of a polysilazane and of a cyclotrisilazane, followed by cross-linking and pyrolysis in argon atmosphere. Spectroscopic investigation (i.e., NMR, FTIR, and Raman) shows that the hafnium alkoxide reacts with the N-H groups of the cyclotrisilazane; in the case of polysilazane, reactions of N-H as well as Si-H groups with the alkoxide are observed. Consequently, scanning and transmission electron microscopy studies reveal that the ceramic nanocomposites obtained from cyclotrisilazane and polysilazane exhibited markedly different microstructures, which is a result of the different reaction pathways of the hafnium alkoxide with cyclotrisilazane and with polysilazane. Furthermore, the two prepared ceramic nanocomposites are unexpectedly found to exhibit extremely different high-temperature behavior with respect to decomposition and crystallization; this essential difference is found to be related to the different distribution of hafnium throughout the ceramic network in the two samples. Thus, the homogeneous distribution of hafnium observed in the polysilazane-derived ceramic leads to an enhanced thermal stability with respect to decomposition, whereas the local enrichment of hafnium within the matrix of the cyclotrisilazane-based sample induces a pronounced decomposition upon annealing at high temperatures. The results indicate that the chemistry and architecture of the precursor has a crucial effect on the microstructure of the resulting ceramic material and consequently on its high-temperature behavior.

  4. Study on the formation of self-assembled monolayers on sol-gel processed hafnium oxide as dielectric layers.

    PubMed

    Ting, Guy G; Acton, Orb; Ma, Hong; Ka, Jae Won; Jen, Alex K-Y

    2009-02-17

    High dielectric constant (k) metal oxides such as hafnium oxide (HfO2) have gained significant interest due to their applications in microelectronics. In order to study and control the surface properties of hafnium oxide, self-assembled monolayers (SAMs) of four different long aliphatic molecules with binding groups of phosphonic acid, carboxylic acid, and catechol were formed and characterized. Surface modification was performed to improve the interface between metal oxide and top deposited materials as well as to create suitable dielectric properties, that is, leakage current and capacitance densities, which are important in organic thin film transistors. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle goniometry, atomic force microscopy (AFM), and simple metal-HfO2-SAM-metal devices were used to characterize the surfaces before and after SAM modification on sol-gel processed hafnium oxide. The alkylphosphonic acid provided the best monolayer formation on sol-gel processed hafnium oxide to generate a well-packed, ultrathin dielectric exhibiting a low leakage current density of 2x10(-8) A/cm2 at an applied voltage of -2.0 V and high capacitance density of 0.55 microF/cm2 at 10 kHz. Dialkylcatechol showed similar characteristics and the potential for using the catechol SAMs to modify HfO2 surfaces. In addition, the integration of this alkylphosphonic acid SAM/hafnium oxide hybrid dielectric into pentacene-based thin film transistors yields low-voltage operation within 1.5 V and improved performance over bare hafnium oxide.

  5. Long period gratings coated with hafnium oxide by plasma-enhanced atomic layer deposition for refractive index measurements.

    PubMed

    Melo, Luis; Burton, Geoff; Kubik, Philip; Wild, Peter

    2016-04-01

    Long period gratings (LPGs) are coated with hafnium oxide using plasma-enhanced atomic layer deposition (PEALD) to increase the sensitivity of these devices to the refractive index of the surrounding medium. PEALD allows deposition at low temperatures which reduces thermal degradation of UV-written LPGs. Depositions targeting three different coating thicknesses are investigated: 30 nm, 50 nm and 70 nm. Coating thickness measurements taken by scanning electron microscopy of the optical fibers confirm deposition of uniform coatings. The performance of the coated LPGs shows that deposition of hafnium oxide on LPGs induces two-step transition behavior of the cladding modes.

  6. Determination of Ideal Broth Formulations Needed to Prepare Hydrous Hafnium Oxide Microspheres via the Internal Gelation Process

    SciTech Connect

    Collins, Jack Lee; Hunt, Rodney Dale; Simmerman, S. G.

    2009-02-01

    A simple test-tube methodology was used to determine optimum process parameters for preparing hydrous hafnium oxide microspheres by the internal gelation process. Broth formulations of hafnyl chloride [HfOCl{sub 2}], hexamethylenetetramine, and urea were found that can be used to prepare hydrous hafnium oxide gel spheres in the temperature range of 70-90 C. A few gel-forming runs were made in which microspheres were prepared with some of these formulations in order to equate the test-tube gelation times with actual gelation times. These preparations confirmed that the test-tube methodology is reliable for determining the ideal broths.

  7. Prediction of stable hafnium carbides: Stoichiometries, mechanical properties, and electronic structure

    NASA Astrophysics Data System (ADS)

    Zeng, Qingfeng; Peng, Junhui; Oganov, Artem R.; Zhu, Qiang; Xie, Congwei; Zhang, Xiaodong; Dong, Dong; Zhang, Litong; Cheng, Laifei

    2013-12-01

    We have performed a search for stable compounds in the hafnium-carbon (Hf-C) system at ambient pressure using a variable-composition ab initio evolutionary algorithm implemented in the uspex code. In addition to the well-known HfC, we predicted two additional thermodynamically stable compounds Hf3C2 and Hf6C5. The structure of Hf6C5 with space group C2/m contains 22 atoms in the conventional cell, and this prediction revives the earlier proposal by Gusev and Rempel [Phys. Status Solidi A 135, 15 (1993), 10.1002/pssa.2211350102]. The stable structure of Hf3C2 also has space group C2/m and is more energetically favorable than the Immm ,P3¯m1,P2, and C2221 structures put forward by Gusev and Rempel [Phys. Status Solidi A 135, 15 (1993), 10.1002/pssa.2211350102]. The dynamical and mechanical stabilities of the newly predicted structures have been verified by calculations of their phonons and elastic constants. Structural vacancies are found in the ordered defective rock-salt-type HfC. Chemical bonding, band structure, and Bader charges are presented and are discussed. All three compounds are weak metals with increasing metallicity as the vacancy concentration increases. The mechanical properties of the hafnium carbides nonlinearly decrease with increasing vacancy concentration, indicating the defect tolerance of this refractory compound. It is, therefore, possible to tune the hardness, ductility, and electrical conductivity by varying the stoichiometry of the hafnium carbides.

  8. Zirconium(IV)- and hafnium(IV)-catalyzed highly enantioselective epoxidation of homoallylic and bishomoallylic alcohols.

    PubMed

    Li, Zhi; Yamamoto, Hisashi

    2010-06-16

    In this report, zirconium(IV)- and hafnium(IV)-bishydroxamic acid complexes were utilized in the highly enantioselective epoxidation of homoallylic alcohols and bishomoallylic alcohols, which used to be quite difficult substrates for other types of asymmetric epoxidation reactions. The performance of the catalyst was improved by adding polar additive and molecular sieves. For homoallylic alcohols, the reaction could provide epoxy alcohols in up to 83% yield and up to 98% ee, while, for bishomoallylic alcohols, up to 79% yield and 99% ee of epoxy alcohols rather than cyclized tetrahydrofuran compounds could be obtained in most cases.

  9. Structural phase transition and elastic properties of hafnium dihydride: A first principles study

    SciTech Connect

    Santhosh, M. Rajeswarapalanichamy, R. Sudhapriyanga, G.; Murugan, A.; Chinthia, A. Jemmy; Kanagaprabha, S.; Iyakutti, K.

    2014-04-24

    The structural and elastic properties of Hafnium dihydride (HfH{sub 2}) are investigated by first principles calculation based on density functional theory using Vienna ab-initio simulation package (VASP). The calculated lattice parameters are in good agreement with the available results. A pressure induced structural phase transition from CaF{sub 2} to FeS{sub 2} phase is observed in HfH{sub 2} at 10.75 GPa. The calculated elastic constants indicate that this hydride is mechanically stable at ambient condition.

  10. A thermally robust and thickness independent ferroelectric phase in laminated hafnium zirconium oxide

    NASA Astrophysics Data System (ADS)

    Riedel, S.; Polakowski, P.; Müller, J.

    2016-09-01

    Ferroelectric properties in hafnium oxide based thin films have recovered the scaling potential for ferroelectric memories due to their ultra-thin-film- and CMOS-compatibility. However, the variety of physical phenomena connected to ferroelectricity allows a wider range of applications for these materials than ferroelectric memory. Especially mixed HfxZr1-xO2 thin films exhibit a broad compositional range of ferroelectric phase stability and provide the possibility to tailor material properties for multiple applications. Here it is shown that the limited thermal stability and thick-film capability of HfxZr1-xO2 can be overcome by a laminated approach using alumina interlayers.

  11. Multimode resistive switching in nanoscale hafnium oxide stack as studied by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hou, Y.; Celano, U.; Goux, L.; Liu, L.; Degraeve, R.; Cheng, Y.; Kang, J.; Jurczak, M.; Vandervorst, W.

    2016-07-01

    The nanoscale resistive switching in hafnium oxide stack is investigated by the conductive atomic force microscopy (C-AFM). The initial oxide stack is insulating and electrical stress from the C-AFM tip induces nanometric conductive filaments. Multimode resistive switching can be observed in consecutive operation cycles at one spot. The different modes are interpreted in the framework of a low defect quantum point contact theory. The model implies that the optimization of the conductive filament active region is crucial for the future application of nanoscale resistive switching devices.

  12. Reactivity of Sulfide Mineral Surfaces

    SciTech Connect

    Rosso, Kevin M.; Vaughan, David J.

    2006-08-01

    In the preceding chapter, the fundamental nature of sulfide mineral surfaces has been discussed, and the understanding we have of the ways in which the surface differs from a simple truncation of the bulk crystal structure reviewed. This naturally leads on to considering our understanding of sulfide surface chemistry, in the sense of how sulfide surfaces interact and react, particularly with gases and liquids. As noted elsewhere in this volume, research on sulfide mineral surfaces and surface reactivity is a relatively recent concern of mineralogists and geochemists, partly prompted by the availability of new imaging and spectroscopic methods, powerful computers and new computer algorithms. There has been a significantly longer history of sulfide mineral surface research associated with technologists working with, or within, the mining industry. Here, electrochemical methods, sometimes combined with analytical and spectroscopic techniques, have been used to probe surface chemistry. The motivation for this work has been to gain a better understanding of the controls of leaching reactions used to dissolve out metals from ores, or to understand the chemistry of the froth flotation systems used in concentrating the valuable (usually sulfide) minerals prior to metal extraction. The need for improved metal extraction technologies is still a major motivation for research on sulfide surfaces, but in the last couple of decades, new concerns have become important drivers for such work. In particular, much greater awareness of the negative environmental impact of acid and toxic metal-bearing waters derived from breakdown of sulfide minerals at former mining operations has prompted research on oxidation reactions, and on sorption of metals at sulfide surfaces. At the interface between fundamental geochemistry and industrial chemistry, the role of sulfide substrates in catalysis, and in the self-assembly and functionalization of organic molecules, has become an area of

  13. Sulfur and sulfides in chondrules

    NASA Astrophysics Data System (ADS)

    Marrocchi, Yves; Libourel, Guy

    2013-10-01

    The nature and distribution of sulfides within type I PO, POP and PP chondrules of the carbonaceous chondrite Vigarano (CV3) have been studied by secondary electron microscopy and electron microprobe. They occur predominantly as spheroidal blebs composed entirely of low-Ni iron sulfide (troilite, FeS) or troilite + magnetite but in less abundance in association with metallic Fe-Ni beads in opaque assemblages. Troilites are mainly located within the low-Ca pyroxene outer zone and their amounts increase with the abundance of low-Ca pyroxene within chondrules, suggesting co-crystallization of troilite and low-Ca pyroxene during high-temperature events. We show that sulfur concentration and sulfide occurrence in chondrules obey high temperature sulfur solubility and saturation laws. Depending on the fS2 and fO2 of the surrounding gas and on the melt composition, mainly the FeO content, sulfur dissolved in chondrule melts may eventually reach a concentration limit, the sulfur content at sulfide saturation (SCSS), at which an immiscible iron sulfide liquid separates from the silicate melt. The occurrence of both a silicate melt and an immiscible iron sulfide liquid is further supported by the non-wetting behavior of sulfides on silicate phases in chondrules due to the high interfacial tension between their precursor iron-sulfide liquid droplets and the surrounding silicate melt during the high temperature chondrule-forming event. The evolution of chondrule melts from PO to PP towards more silicic compositions, very likely due to high PSiO(g) of the surrounding nebular gas, induces saturation of FeS at much lower S content in PP than in PO chondrules, leading to the co-crystallization of iron sulfides and low-Ca pyroxenes. Conditions of co-saturation of low-Ca pyroxene and FeS are only achieved in non canonical environments characterized by high partial pressures of sulfur and SiO and redox conditions more oxidizing than IW-3. Fe and S mass balance calculations also

  14. Sulfide Stability of Planetary Basalts

    NASA Technical Reports Server (NTRS)

    Caiazza, C. M.; Righter, K.; Gibson, E. K., Jr.; Chesley, J. T.; Ruiz, J.

    2004-01-01

    The isotopic system, 187Re 187Os, can be used to determine the role of crust and mantle in magma genesis. In order to apply the system to natural samples, we must understand variations in Re/Os concentrations. It is thought that low [Os] and [Re] in basalts can be attributed to sulfide (FeS) saturation, as Re behaves incompatibly to high degrees of evolution until sulfide saturation occurs [1]. Previous work has shown that lunar basalts are sulfide under-saturated, and mid-ocean ridge, ocean-island and Martian (shergottites) basalts are saturated [2,3]. However, little is known about arc basalts. In this study, basaltic rocks were analyzed across the Trans-Mexican Volcanic Belt.

  15. Application of the Zr/Hf ratio in the determination of hafnium in geochemical samples by high-resolution inductively coupled plasma mass spectrometry.

    PubMed

    Liu, Ya Xuan; Li, Qing Xia; Ma, Na; Sun, Xiao Ling; Bai, Jin Feng; Zhang, Qin

    2014-12-01

    Hafnium content and its change are of significance in geochemistry and cosmochemistry; however, the determination of hafnium has always been problematic in analytical chemistry. In this paper, a new idea is proposed for the determination of hafnium in geochemical samples, including rocks, soils, and stream sediments. Through the comparison of two conventional open-type acid digestion methods (HF-HNO3-HClO4 and HF-HNO3-H2SO4), it was found that although neither of these methods could fully digest the zirconium and hafnium in a sample, the zirconium and hafnium digestion behaviors in one sample were consistent in the 60 experimental geochemical reference materials with different properties, so the experimentally determined Zr/Hf ratio in solution could be used to calculate the hafnium content in a sample. In addition, possible mass spectral interferences during the determination of zirconium and hafnium by high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) were studied, and it was found that the mass spectral interferences of the selected isotopes (90)Zr and (178)Hf could be neglected. The mass spectral behaviors of (90)Zr and (178)Hf were also very consistent during the determination by HR-ICPMS. Since the hafnium content was calculated using the ratio value, all of the errors (including the errors in weighing process, the accidental errors during operation and the instrument fluctuation in the determination) of the Zr/Hf ratio could be effectively reduced or even eliminated. The relative standard deviation of the actual samples was lower than 3.2%, and the detection limit of the method (considering the dilution effect and matrix effect during measurement of the Zr/Hf ratio and zirconium content) was 0.04 μg/g. The proposed method could satisfy the requirement for the determination of hafnium in geochemical samples.

  16. A Reaction Involving Oxygen and Metal Sulfides.

    ERIC Educational Resources Information Center

    Hill, William D. Jr.

    1986-01-01

    Describes a procedure for oxygen generation by thermal decomposition of potassium chlorate in presence of manganese dioxide, reacted with various sulfides. Provides a table of sample product yields for various sulfides. (JM)

  17. Nickel sulfide hollow whisker formation

    SciTech Connect

    Holcomb, G.R.; Cramer, S.D.

    1997-02-01

    Hollow, high-aspect-ratio nickel sulfide whiskers were formed during aqueous corrosion experiments at 250 C by the US Department of Energy. The whiskers grew radially from Teflon thread at the waterline in acidic sodium sulfate solutions containing chloride additions. The hollow morphology is consistent with that reported for the mineral millerite found in nature in hematite cavities. The data suggest that iron and chloride impurities are necessary for the observed whisker structure. Hollow nickel sulfide whiskers were observed only in high-temperature corrosion experiments conducted on stainless steels; they were not observed in similar experiments on nickel-base alloys.

  18. Effects of hafnium additions on the solidification behavior of directionally solidified superalloys. Final report, 1 June 1975-31 August 1977

    SciTech Connect

    Brody, H.D.; Giamei, A.F.

    1981-10-01

    A cooperative university/industry research program into the effect of hafnium additions on the solidification behavior of nickel base superalloys was carried out under Air Force sponsorship at the University of Pittsburgh and Pratt and Whitney Aircraft Company. The research was aimed at gaining a fundamental understanding of the basic solidification characteristics, i.e., development of structure and segregation, of hafnium-modified MAR-M200 over the normal range of casting conditions and for a reasonable variation in alloy content, especially hafnium content.

  19. Microstructure and optical properties of Pr3+-doped hafnium silicate films.

    PubMed

    An, Yongtao; Labbé, Christophe; Khomenkova, Larysa; Morales, Magali; Portier, Xavier; Gourbilleau, Fabrice

    2013-01-21

    In this study, we report on the evolution of the microstructure and photoluminescence properties of Pr3+-doped hafnium silicate thin films as a function of annealing temperature (TA). The composition and microstructure of the films were characterized by means of Rutherford backscattering spectrometry, spectroscopic ellipsometry, Fourier transform infrared absorption, and X-ray diffraction, while the emission properties have been studied by means of photoluminescence (PL) and PL excitation (PLE) spectroscopies. It was observed that a post-annealing treatment favors the phase separation in hafnium silicate matrix being more evident at 950°C. The HfO2 phase demonstrates a pronounced crystallization in tetragonal phase upon 950°C annealing. Pr3+ emission appeared at TA = 950°C, and the highest efficiency of Pr3+ ion emission was detected upon a thermal treatment at 1,000°C. Analysis of the PLE spectra reveals an efficient energy transfer from matrix defects towards Pr3+ ions. It is considered that oxygen vacancies act as effective Pr3+ sensitizer. Finally, a PL study of undoped HfO2 and HfSiOx matrices is performed to evidence the energy transfer.

  20. Contributions to the effective work function of platinum on hafnium dioxide

    SciTech Connect

    Schaeffer, J.K.; Fonseca, L.R.C.; Samavedam, S.B.; Liang, Y.; Tobin, P.J.; White, B.E.

    2004-09-06

    The intrinsic and extrinsic contributions to Fermi level pinning of platinum (Pt) electrodes on hafnium dioxide (HfO{sub 2}) gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the effective work function of Pt-HfO{sub 2}-silicon capacitors. The effective platinum work function is {approx}4.6 eV when annealed in forming gas. However, diffusion of oxygen to the Pt/HfO{sub 2} interface increases the platinum work function to a value of {approx}4.9 eV. Subsequent annealing in forming gas returns the platinum work function to a value comparable to that measured prior to the oxygen anneal. The effective platinum work functions are compared to the prediction of the metal induced gap states (MIGS) model. The presence of interfacial oxygen vacancies or platinum-hafnium bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the MIGS model alone.

  1. Contributions to the effective work function of platinum on hafnium dioxide

    NASA Astrophysics Data System (ADS)

    Schaeffer, J. K.; Fonseca, L. R. C.; Samavedam, S. B.; Liang, Y.; Tobin, P. J.; White, B. E.

    2004-09-01

    The intrinsic and extrinsic contributions to Fermi level pinning of platinum (Pt) electrodes on hafnium dioxide (HfO2) gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the effective work function of Pt-HfO2-silicon capacitors. The effective platinum work function is ˜4.6eV when annealed in forming gas. However, diffusion of oxygen to the Pt /HfO2 interface increases the platinum work function to a value of ˜4.9eV. Subsequent annealing in forming gas returns the platinum work function to a value comparable to that measured prior to the oxygen anneal. The effective platinum work functions are compared to the prediction of the metal induced gap states (MIGS) model. The presence of interfacial oxygen vacancies or platinum-hafnium bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the MIGS model alone.

  2. Microstructure and optical properties of Pr3+-doped hafnium silicate films

    PubMed Central

    2013-01-01

    In this study, we report on the evolution of the microstructure and photoluminescence properties of Pr3+-doped hafnium silicate thin films as a function of annealing temperature (TA). The composition and microstructure of the films were characterized by means of Rutherford backscattering spectrometry, spectroscopic ellipsometry, Fourier transform infrared absorption, and X-ray diffraction, while the emission properties have been studied by means of photoluminescence (PL) and PL excitation (PLE) spectroscopies. It was observed that a post-annealing treatment favors the phase separation in hafnium silicate matrix being more evident at 950°C. The HfO2 phase demonstrates a pronounced crystallization in tetragonal phase upon 950°C annealing. Pr3+ emission appeared at TA = 950°C, and the highest efficiency of Pr3+ ion emission was detected upon a thermal treatment at 1,000°C. Analysis of the PLE spectra reveals an efficient energy transfer from matrix defects towards Pr3+ ions. It is considered that oxygen vacancies act as effective Pr3+ sensitizer. Finally, a PL study of undoped HfO2 and HfSiOx matrices is performed to evidence the energy transfer. PMID:23336520

  3. Preparation and properties of electrically conducting ceramics based on indium oxide-rare earth oxides-hafnium oxides

    SciTech Connect

    Marchant, D.D.; Bates, J.L.

    1983-09-01

    Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

  4. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.604 Section 250.604... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Workover Operations § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or...

  5. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.504 Section 250.504... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Well-Completion Operations § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or...

  6. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Hydrogen sulfide. 250.808 Section 250.808... OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Production Safety Systems § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of...

  7. Nanostructured metal sulfides for energy storage.

    PubMed

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-09-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices. PMID:25073046

  8. Nanostructured metal sulfides for energy storage.

    PubMed

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-09-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

  9. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  10. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Hydrogen sulfide. 250.604 Section 250.604...-Workover Operations § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined...

  11. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Hydrogen sulfide. 250.504 Section 250.504...-Completion Operations § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined...

  12. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  13. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL... § 250.808 Hydrogen sulfide. Production operations in zones known to contain hydrogen sulfide (H2S) or...

  14. Nanostructured metal sulfides for energy storage

    NASA Astrophysics Data System (ADS)

    Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

    2014-08-01

    Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

  15. Platinum metals magmatic sulfide ores.

    PubMed

    Naldrett, A J; Duke, J M

    1980-06-27

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. PMID:17796685

  16. p-Chlorophenyl methyl sulfide

    Integrated Risk Information System (IRIS)

    p - Chlorophenyl methyl sulfide ; CASRN 123 - 09 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for N

  17. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, V.A.; Iton, L.E.; Pasterczyk, J.W.; Winterer, M.; Krause, T.R.

    1994-04-26

    A zeolite-based catalyst is described for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C[sub 2]+ hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  18. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, Victor A.; Iton, Lennox E.; Pasterczyk, James W.; Winterer, Markus; Krause, Theodore R.

    1994-01-01

    A zeolite based catalyst for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C.sub.2 + hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  19. Effect of hafnium doping on density of states in dual-target magnetron co-sputtering HfZnSnO thin film transistors

    SciTech Connect

    Huang, Chuan-Xin; Li, Jun Fu, Yi-Zhou; Jiang, Xue-Yin; Zhang, Jian-Hua; Zhang, Zhi-Lin

    2015-11-23

    This study investigates the effect of hafnium doping on the density of states (DOSs) in HfZnSnO thin film transistors fabricated by dual-target magnetron co-sputtering system. The DOSs is extracted by temperature-dependent field-effect measurements, and they decrease from 1.1 × 10{sup 17} to 4.6 × 10{sup 16 }eV/cm{sup 3} with increasing the hafnium concentrations. The behavior of DOSs for the increasing hafnium concentration HfZnSnO thin film transistors can be confirmed by both the reduction of ΔV{sub T} under bias stress and the trapping charges calculated by capacitance voltage measurements. It suggests that the reduction in DOSs due to the hafnium doping is closely related with the bias stability and thermal stability.

  20. Zirconium and hafnium fractionation in differentiation of alkali carbonatite magmatic systems

    NASA Astrophysics Data System (ADS)

    Kogarko, L. N.

    2016-05-01

    Zirconium and hafnium are valuable strategic metals which are in high demand in industry. The Zr and Hf contents are elevated in the final products of magmatic differentiation of alkali carbonatite rocks in the Polar Siberia region (Guli Complex) and Ukraine (Chernigov Massif). Early pyroxene fractionation led to an increase in the Zr/Hf ratio in the evolution of the ultramafic-alkali magmatic system due to a higher distribution coefficient of Hf in pyroxene with respect to Zr. The Rayleigh equation was used to calculate a quantitative model of variation in the Zr/Hf ratio in the development of the Guli magmatic system. Alkali carbonatite rocks originated from rare element-rich mantle reservoirs, in particular, the metasomatized mantle. Carbonated mantle xenoliths are characterized by a high Zr/Hf ratio due to clinopyroxene development during metasomatic replacement of orthopyroxene by carbonate fluid melt.

  1. Dinitrogen cleavage and functionalization by carbon monoxide promoted by a hafnium complex.

    PubMed

    Knobloch, Donald J; Lobkovsky, Emil; Chirik, Paul J

    2010-01-01

    Molecular nitrogen (N(2)) and carbon monoxide (CO) have the two strongest bonds in chemistry and present significant challenges in developing new transformations that exploit these two abundant feedstocks. At the core of this objective is the discovery of transition-metal compounds that promote the six-electron reductive cleavage of N(2) at ambient temperature and pressure and also promote new nitrogen-element bond formation. Here we show that an organometallic hafnium compound induces N(2) cleavage on the addition of CO, with a simultaneous assembly of new nitrogen-carbon and carbon-carbon bonds. Subsequent addition of a weak acid liberates oxamide, which demonstrates that an important agrochemical can be synthesized directly from N(2) and CO. These studies introduce an alternative paradigm for N(2) cleavage and functionalization in which the six-electron reductive cleavage is promoted by both the transition metal and the incoming ligand, CO, used for the new bond formations.

  2. Wake-up effects in Si-doped hafnium oxide ferroelectric thin films

    SciTech Connect

    Zhou, Dayu; Xu, Jin; Li, Qing; Guan, Yan; Cao, Fei; Dong, Xianlin; Müller, Johannes; Schenk, Tony; Schröder, Uwe

    2013-11-04

    Hafnium oxide based ferroelectric thin films have shown potential as a promising alternative material for non-volatile memory applications. This work reports the switching stability of a Si-doped HfO{sub 2} film under bipolar pulsed-field operation. High field cycling causes a “wake-up” in virgin “pinched” polarization hysteresis loops, demonstrated by an enhancement in remanent polarization and a shift of negative coercive voltage. The rate of wake-up is accelerated by either reducing the frequency or increasing the amplitude of the cycling field. We suggest de-pinning of domains due to reduction of the defect concentration at bottom electrode interface as origin of the wake-up.

  3. High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition

    SciTech Connect

    Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Milne, William I.; Flewitt, Andrew J.; Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J.

    2011-06-20

    Amorphous hafnium oxide (HfO{sub x}) is deposited by sputtering while achieving a very high k{approx}30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfO{sub x} (cubic k{approx}30). The films also possess a high electrical resistivity of 10{sup 14} {Omega} cm, a breakdown strength of 3 MV cm{sup -1}, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate ({approx}25 nm min{sup -1}) makes these high-k amorphous HfO{sub x} films highly advantageous for plastic electronics and high throughput manufacturing.

  4. Cesium hafnium chloride: A high light yield, non-hygroscopic cubic crystal scintillator for gamma spectroscopy

    SciTech Connect

    Burger, Arnold; Rowe, Emmanuel; Groza, Michael; Morales Figueroa, Kristle; Cherepy, Nerine J.; Beck, Patrick R.; Hunter, Steven; Payne, Stephen A.

    2015-10-05

    We report on the scintillation properties of Cs{sub 2}HfCl{sub 6} (cesium hafnium chloride or CHC) as an example of a little-known class of non-hygroscopic compounds having the generic cubic crystal structure of K{sub 2}PtCl{sub 6}. The crystals are easily growable from the melt using the Bridgman method with minimal precursor treatments or purification. CHC scintillation is centered at 400 nm, with a principal decay time of 4.37 μs and a light yield of up to 54 000 photons/MeV when measured using a silicon CCD photodetector. The light yield is the highest ever reported for an undoped crystal, and CHC also exhibits excellent light yield nonproportionality. These desirable properties allowed us to build and test CHC gamma-ray spectrometers providing energy resolution of 3.3% at 662 keV.

  5. Calculation of the production cross sections of high-spin isomeric states in hafnium

    SciTech Connect

    Chadwick, M.B.; Young, P.G. . Nuclear Physics Lab.; Los Alamos National Lab., NM )

    1989-01-01

    The J{sup {pi}} = 16{sup +} isomeric state in {sup 178}Hf(E{sub x} = 2.447 MeV), which has a halflife of 31 years, poses a threat for serious radioactive activation problems in some fusion reactor designs if its production in 14-MeV neutron reactions is significant. The relatively high excitation energy (2.447 MeV) of this state results in it lying in the continuum region, so it is necessary in a calculation to reconstruct the salient nuclear structure around the state, particularly rotational band levels that might be populated and would feed into it. Using preequilibrium and Hauser-Feshbach statistical theories, the cross sections for this and other hafnium isomeric states are calculated and compared with experimental measurements, where available. 13 refs., 6 figs., 3 tabs.

  6. Stress-rupture strength and microstructural stability of tungsten-hafnium-carbon-wire reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Signorelli, R. A.

    1974-01-01

    Tungsten-hafnium-carbon - superalloy composites were found to be potentially useful for turbine blade applications on the basis of stress-rupture strength. The 100- and 1000-hr rupture strengths calculated for 70 vol. % fiber composites based on test data at 1090C (2000F) were 420 and 280 MN/m2 (61,000 and 41,000 psi, respectively). The investigation indicated that, with better quality fibers, composites having 100- and 1000-hr rupture strengths of 570 and 370 MN/m2 (82,000 and 54,000 psi, respectively), may be obtained. Metallographic studies indicated sufficient fiber-matrix compatibility for 1000 hr or more at 1090C (2000F).

  7. The effect of twinning on the work hardening behavior in Hafnium

    SciTech Connect

    Cerreta, E. K.; Gray, G. T. , III; Yablinsky, C.

    2004-01-01

    In many HCP metals, both twinning and slip are known to be important modes of deformation. However, the interaction of the two mechanisms and their effect on work hardening is not well understood. In hafnium, twinning and work hardening rates increase with increasing strain, increasing strain rate, and decreasing temperature. At low strains and strain rates and at higher temperatures, slip dominates deformation and rates of work hardening are relatively lower. To characterize the interaction of slip and twinning, Hf specimens were prestrained quasi-statically in compression at 77K, creating specimens that were heavily twinned. These specimens were subsequently reloaded at room temperature. Twinning within the microstructures was characterized optically and using transmission electron microscopy. The interaction of slip with the twins was investigated as a function of prestrain and correlated with the observed rates of work hardening.

  8. Hafnium dioxide as a dielectric for highly-sensitive waveguide-coupled surface plasmon resonance sensors

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal; Sharma, Suresh C.; Hozhabri, Nader

    2016-04-01

    Hafnium dioxide has been recognized as an excellent dielectric for microelectronics. However, its usefulness for the surface plasmon based sensors has not yet been tested. Here we investigate its usefulness for waveguide-coupled bi-metallic surface plasmon resonance sensors. Several Ag/HfO2/Au multilayer structure sensors were fabricated and evaluated by optical measurements and computer simulations. The resulting data establish correlations between the growth parameters and sensor performance. The sensor sensitivity to refractive index of analytes is determined to be S n = /∂ θ SPR ∂ n ≥ 4 7 0 . The sensitivity data are supported by simulations, which also predict 314 nm for the evanescent field decay length in air.

  9. Sub-10 nm low current resistive switching behavior in hafnium oxide stack

    NASA Astrophysics Data System (ADS)

    Hou, Y.; Celano, U.; Goux, L.; Liu, L.; Fantini, A.; Degraeve, R.; Youssef, A.; Xu, Z.; Cheng, Y.; Kang, J.; Jurczak, M.; Vandervorst, W.

    2016-03-01

    In this letter, a tip-induced cell relying on the conductive atomic force microscope is proposed. It is verified as a referable replica of an integrated resistive random access memory (RRAM) device. On the basis of this cell, the functionality of sub-10 nm resistive switching is confirmed in hafnium oxide stack. Moreover, the low current switching behavior in the sub-10 nm dimension is found to be more pronounced than that of a 50 × 50 nm2 device. It shows better ON/OFF ratio and low leakage current. The enhanced memory performance is ascribed to a change in the shape of the conductive filament as the device dimensions are reduced to sub-10 nm. Therefore, device downscaling provides a promising approach for the resistance optimization that benefits the RRAM array design.

  10. Periodic alignment of Si quantum dots on hafnium oxide coated single wall carbon nanotubes

    SciTech Connect

    Olmedo, Mario; Martinez-Morales, Alfredo A.; Ozkan, Mihrimah; Liu Jianlin; Liu Gang; Lau, C.N.; Yengel, Emre; Ozkan, Cengiz S.

    2009-03-23

    We demonstrate a bottom up approach for the aligned epitaxial growth of Si quantum dots (QDs) on one-dimensional (1D) hafnium oxide (HfO{sub 2}) ridges created by the growth of HfO{sub 2} thin film on single wall carbon nanotubes. This growth process creates a high strain 1D ridge on the HfO{sub 2} film, which favors the formation of Si seeds over the surrounding flat HfO{sub 2} area. Periodic alignment of Si QDs on the 1D HfO{sub 2} ridge was observed, which can be controlled by varying different growth conditions, such as growth temperature, growth time, and disilane flow rate.

  11. Comparison of the synthesis of Ge nanocrystals in hafnium aluminum oxide and silicon oxide matrices.

    PubMed

    Chew, H G; Zheng, F; Choi, W K; Chim, W K; Fitzgerald, E A; Foo, Y L

    2009-02-01

    Growth of germanium (Ge) nanocrystals in silicon (Si) oxide and hafnium aluminum oxide (HfAlO) is examined. In Si oxide, nanocrystals were able to form at annealing temperatures of 800 degrees C to 1000 degrees C. Nanocrystals formed at 800 degrees C were round and approximately 8 nm in diameter, at 900 degrees C they become facetted and at 1000 degrees C they become spherical again. In HfAlO, at 800 degrees C nanocrystals formed are relatively smaller (approximately 3 nm in diameter) and lower in density. While at 900 degrees C and 1000 degrees C, nanocrystals did not form due to out-diffusion of Ge. Different nanocrystal formation characteristics in the matrices are attributed to differences in their crystallization temperatures.

  12. Composition effects on mechanical properties of tungsten-rhenium-hafnium-carbon alloys

    NASA Technical Reports Server (NTRS)

    Witzke, W. R.

    1973-01-01

    The mechanical properties of rod and sheet fabricated from arc melted W-4Re-Hf-C alloys containing up to about 0.8 mol percent hafnium carbide (HfC) were evaluated in the as-worked condition. The DBTT's of electropolished bend and tensile specimens were independent of HfC content in this range but dependent on excess Hf or C above that required for stoichiometric HfC. Low temperature ductility was a maximum at Hf contents slightly in excess of stoichiometric. Variations in high temperature strength were also dependent on excess Hf and C. Maximum creep strengthening also occurred at Hf contents in excess of stoichiometric. Analysis of extracted second phase particles indicated that creep strength was reduced by increasing WC content in the HfC particles.

  13. Episodic growth of the Gondwana supercontinent from hafnium and oxygen isotopes in zircon.

    PubMed

    Kemp, A I S; Hawkesworth, C J; Paterson, B A; Kinny, P D

    2006-02-01

    It is thought that continental crust existed as early as 150 million years after planetary accretion, but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records. For example, the striking global peaks in juvenile igneous activity 2.7, 1.9 and 1.2 Gyr ago imply rapid crustal generation in response to the emplacement of mantle 'super-plumes', rather than by the continuous process of subduction. Yet uncertainties persist over whether these age peaks are artefacts of selective preservation, and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks. Detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle. These 'model' ages are only meaningful if the host magma lacked a mixed or sedimentary source component, but the latter can be diagnosed by oxygen isotopes, which are strongly fractionated by rock-hydrosphere interactions. Here we report the first study that integrates hafnium and oxygen isotopes, all measured in situ on the same, precisely dated detrital zircon grains. The data reveal that crust generation in part of Gondwana was limited to major pulses at 1.9 and 3.3 Gyr ago, and that the zircons crystallized during repeated reworking of crust formed at these times. The implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts. PMID:16452978

  14. Episodic growth of the Gondwana supercontinent from hafnium and oxygen isotopes in zircon.

    PubMed

    Kemp, A I S; Hawkesworth, C J; Paterson, B A; Kinny, P D

    2006-02-01

    It is thought that continental crust existed as early as 150 million years after planetary accretion, but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records. For example, the striking global peaks in juvenile igneous activity 2.7, 1.9 and 1.2 Gyr ago imply rapid crustal generation in response to the emplacement of mantle 'super-plumes', rather than by the continuous process of subduction. Yet uncertainties persist over whether these age peaks are artefacts of selective preservation, and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks. Detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle. These 'model' ages are only meaningful if the host magma lacked a mixed or sedimentary source component, but the latter can be diagnosed by oxygen isotopes, which are strongly fractionated by rock-hydrosphere interactions. Here we report the first study that integrates hafnium and oxygen isotopes, all measured in situ on the same, precisely dated detrital zircon grains. The data reveal that crust generation in part of Gondwana was limited to major pulses at 1.9 and 3.3 Gyr ago, and that the zircons crystallized during repeated reworking of crust formed at these times. The implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts.

  15. Synthesis of nanoparticles of barium lanthanum hafnium oxide by a modified combustion process.

    PubMed

    John, Asha M; Jose, R; Divakar, R; Koshy, J

    2002-02-01

    Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm.

  16. Marine diagenesis of hydrothermal sulfide

    SciTech Connect

    Moammar, M.O.

    1985-01-01

    An attempt is made to discuss the artificial and natural oxidation and hydrolysis of hydrothermal sulfide upon interaction with normal seawater. Synthetic and natural ferrosphalerite particles used in kinetic oxidation and hydrolysis studies in seawater develop dense, crystalline coatings consisting of ordered and ferrimagnetic delta-(Fe, Zn)OOH. Due to the formation of this reactive diffusion barrier, the release of Zn into solution decreases rapidly, and sulfide oxidation is reduced to a low rate determined by the diffusion of oxygen through the oxyhydroxide film. This also acts as an efficient solvent for ions such as Zn/sup 2 +/, Ca/sup 2 +/, and possibly Cd/sup 2 +/, which contribute to the stabilization of the delta-FeOOH structure. The oxidation of sulfide occurs in many seafloor spreading areas, such as 21/sup 0/N on the East Pacific Ridge. In these areas the old surface of the sulfide chimneys are found to be covered by an orange stain, and sediment near the base of nonactive vents is also found to consist of what has been referred to as amorphous iron oxide and hydroxide. This thesis also discusses the exceedingly low solubility of zinc in seawater, from delta-(Fe, Zn)OOH and the analogous phase (zinc-ferrihydroxide) and the zinc exchange minerals, 10-A manganate and montmorillonite. The concentrations of all four are of the same magnitude (16, 36.4, and 12 nM, respectively) as the zinc concentration in deep ocean water (approx. 10 nM), which suggests that manganates and montmorillonite with iron oxyhydroxides control zinc concentration in the deep ocean.

  17. Sulfide smelting using Ausmelt technology

    NASA Astrophysics Data System (ADS)

    Mounsey, Edward N.; Robilliard, Ken R.

    1994-08-01

    Over the past decade, Ausmelt has been developing the top submerged lancing process for the smelting of sulfidic ores to recover such metals as copper, lead, silver, tin, antimony, and nickel as well as for separation of minor elements such as arsenic, antimony, and bismuth. Development has taken place in Ausmelt's pilot plant in Dandenong, near Melbourne, Australia. A number of projects have proceeded to commercial-scale operation. This paper reviews developments at both the pilot and commercial scales.

  18. Metal sulfide for battery applications

    SciTech Connect

    Guidotti, R.A.

    1988-01-01

    A number of metal sulfides can be used in batteries as a cathode (reducible) material as part of an electrochemical couple to provide energy. There are a number of physical and chemical characteristics that can be evaluated for screening potential candidates for use in batteries. These include: cell potential vs. Li, thermal and chemical stability, electrical conductivity, allotropic form (phase), reaction kinetics during discharge, type of discharge mechanism, and material rechargeability. These are reviewed in general, with emphasis on sulfides of copper, iron, and molybdenum which are currently being used as cathodes in Li and Li-alloy batteries. The presence of impurities can adversely impact performance when naturally occurring sulfide minerals are used for battery applications. Sandia National Laboratories uses natural pyrite (FeS2) for its high-temperature, thermally activated Li(Si)/FeS2 batteries. The purification and processing procedures for the FeS2 involves both chemical and physical methods. Flotation was found to yield comparable results as HF leaching for removal of silica, but without the negative health and environmental concerns associated with this technique. 11 refs., 5 figs., 6 tabs.

  19. Chemical dissolution of sulfide minerals

    USGS Publications Warehouse

    Chao, T.T.; Sanzolone, R.F.

    1977-01-01

    Chemical dissolution treatments involving the use of aqua regia, 4 N HNO3, H2O2-ascorbic acid, oxalic acid, KClO3+HCl, and KClO3+HCl followed by 4 N HNO3 were applied to specimens of nine common sulfide minerals (galena, chalcopyrite, cinnabar, molybdenite, orpiment, pyrite, stibnite, sphalerite, and tetrahedrite) mixed individually with a clay loam soil. The resultant decrease in the total sulfur content of the mixture, as determined by using the Leco induction furnace, was used to evaluate the effectiveness of each chemical treatment. A combination of KClO3+HCl followed by 4 N HNO3 boiling gently for 20 min has been shown to be very effective in dissolving all the sulfide minerals. This treatment is recommended to dissolve metals residing in sulfide minerals admixed with secondary weathering products, as one step in a fractionation scheme whereby metals in soluble and adsorbed forms, and those associated with organic materials and secondary oxides, are first removed by other chemical extractants.

  20. Sulfide-Driven Microbial Electrosynthesis

    SciTech Connect

    Gong, YM; Ebrahim, A; Feist, AM; Embree, M; Zhang, T; Lovley, D; Zengler, K

    2013-01-01

    Microbial electrosynthesis, the conversion of carbon dioxide to organic molecules using electricity, has recently been demonstrated for acetogenic microorganisms, such as Sporomusa ovata. The energy for reduction of carbon dioxide originates from the hydrolysis of water on the anode, requiring a sufficiently low potential. Here we evaluate the use of sulfide as an electron source for microbial electrosynthesis. Abiotically oxidation of sulfide on the anode yields two electrons. The oxidation product, elemental sulfur, can be further oxidized to sulfate by Desulfobulbus propionicus, generating six additional electrons in the process. The eight electrons generated from the combined abiotic and biotic steps were used to reduce carbon dioxide to acetate on a graphite cathode by Sporomusa ovata at a rate of 24.8 mmol/day.m(2). Using a strain of Desulfuromonas as biocatalyst on the anode resulted in an acetate production rate of 49.9 mmol/day.m(2), with a Coulombic efficiency of over 90%. These results demonstrate that sulfide can serve effectively as an alternative electron donor for microbial electrosynthesis.

  1. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Hydrogen sulfide. 250.604 Section 250.604... § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  2. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Hydrogen sulfide. 250.504 Section 250.504... § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  3. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Hydrogen sulfide. 250.604 Section 250.604... § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  4. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Hydrogen sulfide. 250.504 Section 250.504... § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  5. 30 CFR 250.604 - Hydrogen sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Hydrogen sulfide. 250.604 Section 250.604... § 250.604 Hydrogen sulfide. When a well-workover operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  6. 30 CFR 250.504 - Hydrogen sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Hydrogen sulfide. 250.504 Section 250.504... § 250.504 Hydrogen sulfide. When a well-completion operation is conducted in zones known to contain hydrogen sulfide (H2S) or in zones where the presence of H2S is unknown (as defined in § 250.490 of...

  7. Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago.

    PubMed

    Næraa, T; Scherstén, A; Rosing, M T; Kemp, A I S; Hoffmann, J E; Kokfelt, T F; Whitehouse, M J

    2012-05-30

    Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens. These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate

  8. Aminopyridinate-FI hybrids, their hafnium and titanium complexes, and their application in the living polymerization of 1-hexene.

    PubMed

    Haas, Isabelle; Dietel, Thomas; Press, Konstantin; Kol, Moshe; Kempe, Rhett

    2013-10-11

    Based on two well-established ligand systems, the aminopyridinato (Ap) and the phenoxyimine (FI) ligand systems, new Ap-FI hybrid ligands were developed. Four different Ap-FI hybrid ligands were synthesized through a simple condensation reaction and fully characterized. The reaction of hafnium tetrabenzyl with all four Ap-FI hybrid ligands exclusively led to mono(Ap-FI) complexes of the type [(Ap-FI)HfBn2 ]. The ligands acted as tetradentate dianionic chelates. Upon activation with tris(pentafluorophenyl)borane, the hafnium-dibenzyl complexes led to highly active catalysts for the polymerization of 1-hexene. Ultrahigh molecular weights and extremely narrow polydispersities support the living nature of this polymerization process. A possible deactivation product of the hafnium catalysts was characterized by single-crystal X-ray analysis and is discussed. The coordination modes of these new ligands were studied with the help of model titanium complexes. The reaction of titanium(IV) isopropoxide with ligand 1 led to a mono(Ap-FI) complex, which showed the desired fac-mer coordination mode. Titanium (IV) isopropoxide reacted with ligand 4 to give a complex of the type [(ApH-FI)2 Ti(OiPr)2 ], which featured the ligand in its monoanionic form. The two titanium complexes were characterized by X-ray crystal-structure analysis.

  9. Lithium-cupric sulfide cell

    SciTech Connect

    Cuesta, A.J.; Bump, D.D.

    1980-01-01

    Lithium cells have become the primary power source for cardiac pacemakers due to their reliability and longevity at low current drain rates. A lithium-cupric sulfide cell was developed which makes maximum use of the shape of a pacemaker's battery compartment. The cell has a stable voltage throughout 90% of its lifetime. It then drops to a second stable voltage before depletion. The voltage drop creates a small decrease in pacemaker rate, which alerts the physician to replace the pacemaker. No loss of capacity due to self-discharge as been seen to date, and cells have proven to be safe under extreme conditions. 2 refs.

  10. Molybdenum sulfide/carbide catalysts

    DOEpatents

    Alonso, Gabriel; Chianelli, Russell R.; Fuentes, Sergio; Torres, Brenda

    2007-05-29

    The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

  11. Preparation of amorphous sulfide sieves

    DOEpatents

    Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

    2006-11-07

    The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

  12. Synthesis and optical properties of sulfide nanoparticles prepared in dimethylsulfoxide.

    PubMed

    Li, Yuebin; Ma, Lun; Zhang, Xing; Joly, Alan G; Liu, Zuli; Chen, Wei

    2008-11-01

    Many methods have been reported for the formation of sulfide nanoparticles by the reaction of metallic salts with sulfide chemical sources in aqueous solutions or organic solvents. Here, we report the formation of sulfide nanoparticles in dimethylsulfoxide (DMSO) by boiling metallic salts without sulfide sources. The sulfide sources are generated from the boiling of DMSO and react with metallic salts to form sulfide nanoparticles. In this method DMSO functions as a solvent and a sulfide source as well as a stabilizer for the formation of the nanoparticles. The recipe is simple and economical making sulfide nanoparticles formed in this way readily available for many potential applications.

  13. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Provisions § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration... the potassium ferricyanide titration method for the determination of sulfide in wastewaters...

  14. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Provisions § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration... the potassium ferricyanide titration method for the determination of sulfide in wastewaters...

  15. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Provisions § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration... the potassium ferricyanide titration method for the determination of sulfide in wastewaters...

  16. Synthesis and Optical Properties of Sulfide Nanoparticles Prepared in Dimethylsulfoxide

    SciTech Connect

    Li, Yuebin; Ma, Lun; Zhang, Xing; Joly, Alan G.; Liu, Zuli; Chen, Wei

    2008-11-01

    Many methods have been reported for the formation of sulfide nanoparticles by the reaction of metallic salts with sulfide chemical sources in aqueous solutions or organic solvents. Here, we report the formation of sulfide nanoparticles in dimethylsulfoxide (DMSO) by boiling metallic salts without sulfide sources. The sulfide sources are generated from the boiling of DMSO and react with metallic salts to form sulfide nanoparticles. In this method DMSO functions as a solvent and a sulfide source as well as a stabilizer for the formation of the nanoparticles. The recipe is simple and economical making sulfide nanoparticles formed in this way readily available for many potential applications.

  17. Variation in sulfide tolerance of photosystem II in phylogenetically diverse cyanobacteria from sulfidic habitats

    NASA Technical Reports Server (NTRS)

    Miller, Scott R.; Bebout, Brad M.

    2004-01-01

    Physiological and molecular phylogenetic approaches were used to investigate variation among 12 cyanobacterial strains in their tolerance of sulfide, an inhibitor of oxygenic photosynthesis. Cyanobacteria from sulfidic habitats were found to be phylogenetically diverse and exhibited an approximately 50-fold variation in photosystem II performance in the presence of sulfide. Whereas the degree of tolerance was positively correlated with sulfide levels in the environment, a strain's phenotype could not be predicted from the tolerance of its closest relatives. These observations suggest that sulfide tolerance is a dynamic trait primarily shaped by environmental variation. Despite differences in absolute tolerance, similarities among strains in the effects of sulfide on chlorophyll fluorescence induction indicated a common mode of toxicity. Based on similarities with treatments known to disrupt the oxygen-evolving complex, it was concluded that sulfide toxicity resulted from inhibition of the donor side of photosystem II.

  18. Ammonia and hydrogen sulfide removal using biochar

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reducing ammonia and hydrogen sulfide emissions from livestock facilities is an important issue for many communities and livestock producers. Ammonia has been regarded as odorous, precursor for particulate matter (PM), and contributed to livestock mortality. Hydrogen sulfide is highly toxic at elev...

  19. Sulfide oxidation under chemolithoautotrophic denitrifying conditions.

    PubMed

    Cardoso, Ricardo Beristain; Sierra-Alvarez, Reyes; Rowlette, Pieter; Flores, Elias Razo; Gómez, Jorge; Field, Jim A

    2006-12-20

    Chemolithoautotrophic denitrifying microorganisms oxidize reduced inorganic sulfur compounds coupled to the reduction of nitrate as an electron acceptor. These denitrifiers can be applied to the removal of nitrogen and/or sulfur contamination from wastewater, groundwater, and gaseous streams. This study investigated the physiology and kinetics of chemolithotrophic denitrification by an enrichment culture utilizing hydrogen sulfide, elemental sulfur, or thiosulfate as electron donor. Complete oxidation of sulfide to sulfate was observed when nitrate was supplemented at concentrations equal or exceeding the stoichiometric requirement. In contrast, sulfide was only partially oxidized to elemental sulfur when nitrate concentrations were limiting. Sulfide was found to inhibit chemolithotrophic sulfoxidation, decreasing rates by approximately 21-fold when the sulfide concentration increased from 2.5 to 10.0 mM, respectively. Addition of low levels of acetate (0.5 mM) enhanced denitrification and sulfate formation, suggesting that acetate was utilized as a carbon source by chemolithotrophic denitrifiers. The results of this study indicate the potential of chemolithotrophic denitrification for the removal of hydrogen sulfide. The sulfide/nitrate ratio can be used to control the fate of sulfide oxidation to either elemental sulfur or sulfate.

  20. 30 CFR 250.808 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 2 2011-07-01 2011-07-01 false Hydrogen sulfide. 250.808 Section 250.808 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE... Safety Systems § 250.808 Hydrogen sulfide. Production operations in zones known to contain...

  1. Dielectric and complex impedance properties of tetravalent hafnium (HF 4+) integrated cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Sanchez, Luis

    The work presented in this thesis was carried out to understand the effects of tetravalent hafnium (Hf4+) ion on the crystal structure and phase, surface morphology, electrical, dielectric and complex impedance properties of cobalt ferrite (CoFe2O4; CFO). Hafnium incorporated cobalt ferrite, CoFe2-xHfxO4, with x = 0.00, 0.05, 0.075, 0.10, 0.15 and 0.20 were prepared by the standard solid state ceramic synthesis method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations were performed to determine the structural properties. Most important aspect of this study is to explore the dielectric and complex impedance properties as a function of variable temperature (T=300-1000 K) and frequency (f=20 Hz -1 MHz). Room temperature and the temperature dependence of dielectric constant, loss factor, complex impedance, and the ac resistivity measurements enabled us to understand the effect of temperature and frequency on the electrical and dielectric properties on CoFe2-xHfxO4 and, thus, to derive structure-property relation. X-ray diffraction (XRD) patterns for Hf-incorporated CFO confirm the formation of majority of CFO spinel [with space group Fd3m (227)] phase, in addition to the small amount of HfO2 monoclinic [space group, P1 21/c (14)] phase leading to formation of CFO-Hf composites. The lattice constant values derived from XRD for CFO-Hf were found to increase from 8.374 A (x = 0.000) to 8.391 A (x = 0.200). The lattice expansion is significant at the very first step of Hf-incorporation and then slows down with progressive Hf-incorporation. SEM imaging analysis indicates that Hf resides at the grain boundaries for CFO-Hf. The dielectric constant (epsilon') of CFO-Hf is T-independent at T<450 K, at which point increasing trend prevails. A grain bulk-boundary based two-layer model, where semiconducting-grains separated by insulating-grain boundaries, satisfactorily accounts for epsilon- T (>450 K) variation. Correspondingly, electrical

  2. Internal correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis.

    PubMed

    Rodríguez-Castrillón, José Angel; Moldovan, Mariella; García Alonso, J Ignacio

    2009-05-01

    A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched (194)Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194, 195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the reference material "BCR-723 road dust" and has been applied to different environmental matrices (road dust, air particles, bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using Kragten's spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope ratios and not by the uncertainties of the isotopic composition of platinum and hafnium.

  3. Weathering of sulfides on Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.; Fisher, Duncan S.

    1987-01-01

    Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produce degradation products in the Martian regolith. By analogy and terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni, and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato-and hydroxo-complex ions and sols formed gossan above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite), and silica (opal). Underlying groundwater, now permafrost contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates, and phyllosilicates during dust storms on Mars.

  4. Percutaneous absorption of selenium sulfide

    SciTech Connect

    Farley, J.; Skelly, E.M.; Weber, C.B.

    1986-01-01

    The purpose of this study was to determine selenium levels in the urine of Tinea patients before and after overnight application of a 2.5% selenium sulfide lotion. Selenium was measured by atomic absorption spectroscopy (AAS). Hydride generation and carbon rod atomization were studied. It was concluded from this study that selenium is absorbed through intact skin. Selenium is then excreted, at least partially, in urine, for at least a week following treatment. The data show that absorption and excretion of selenium vary on an individual basis. Selenium levels in urine following a single application of selenium sulfide lotion do not indicate that toxic amounts of selenium are being absorbed. Repeated treatments with SeS/sub 2/ result in selenium concentrations in urine which are significantly higher than normal. Significant matrix effects are observed in the carbon rod atomization of urine samples for selenium determinations, even in the presence of a matrix modifier such as nickel. The method of standard additions is required to obtain accurate results in the direct determination of selenium in urine by carbon rod AAS.

  5. Hydrogen sulfide pollution in wastewater treatment facilities

    SciTech Connect

    AlDhowalia, K.H. )

    1987-01-01

    The hydrogen sulfide (H{sub 2}S) found in wastewater collection systems and wastewater treatment facilities results from the bacterial reduction of the sulfate ion (SO{sub 4}). Hydrogen sulfide is a gas that occurs both in the sewer atmosphere and as a dissolved gas in the wastewater. When raw wastewater first enters the wastewater treatment facility by gravity most of the hydrogen sulfide is in the gaseous phase and will escape into the atmosphere at the inlet structures. Also some of the dissolved hydrogen sulfide will be released at points of turbulance such as at drops in flow, flumes, or aeration chambers. Several factors can cause excessive hydrogen sulfide concentrations in a sewerage system. These include septic sewage, long flow times in the sewerage system, high temperatures, flat sewer grades, and poor ventilation. These factors are discussed in this paper.

  6. Unique erosion features of hafnium cathode in atmospheric pressure arcs of air, nitrogen and oxygen

    NASA Astrophysics Data System (ADS)

    Ghorui, S.; Meher, K. C.; Kar, R.; Tiwari, N.; Sahasrabudhe, S. N.

    2016-07-01

    Experimental investigation of cathode erosion in atmospheric pressure hafnium-electrode plasma torches is reported under different plasma environments along with the results of numerical simulation. Air, nitrogen and oxygen are the plasma gases considered. Distinct differences in the erosion features in different plasmas are brought out. Cathode images exhibiting a degree of erosion and measured erosion rates are presented in detail as a function of time of arc operation and arc current. Physical erosion rates are determined using high precision balance. The changes in the surface microstructures are investigated through scanning electron microscopy (SEM). Evolution of cathode chemistry is determined using energy dispersive x-ray spectroscopy (EDX). Numerical simulation with proper consideration of the plasma effects is performed for all the plasma gases. The important role of electromagnetic body forces in shaping the flow field and the distribution of pressure in the region is explored. It is shown that the mutual interaction between fluid dynamic and electromagnetic body forces may self-consistently evolve a situation of an extremely low cathode erosion rate.

  7. Temperature effect on electrospinning of nanobelts: the case of hafnium oxide.

    PubMed

    Su, Yurong; Lu, Bingan; Xie, Yizhu; Ma, Ziwei; Liu, Lixin; Zhao, Haiting; Zhang, Jia; Duan, Huigao; Zhang, Hongliang; Li, Jian; Xiong, Yuqing; Xie, Erqing

    2011-07-15

    Electrospinning is a convenient and versatile method for fabricating different kinds of one-dimensional nanostructures such as nanofibres, nanotubes and nanobelts. Environmental parameters have a great influence on the electrospinning nanostructure. Here we report a new method to fabricate hafnium oxide (HfO(2)) nanobelts. HfO(2) nanobelts were prepared by electrospinning a sol-gel solution with the implementation of heating and subsequent calcination treatment. We investigate the temperature dependence of the products by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive x-ray (EDX) spectroscopy. The heating temperature of spinning ambient is found to be crucial to the formation of HfO(2) nanobelts. By tuning the temperature, the morphological transformation of HfO(2) from nanowires to nanobelts was achieved. It was found that the rapid evaporation of solvent played an important role in the formation process of HfO(2) nanobelts. It is shown that nanobelts can only be obtained with the temperature higher than 50 °C and they are in the high quality monoclinic phase. A possible growth mechanism of the nanobelts based on phase separation is proposed. The enhanced photoluminescence (PL) of HfO(2):Eu(3+) nanobelts is also illustrated. PMID:21659687

  8. The molecular frame electric dipole moment and hyperfine interactions in hafnium fluoride, HfF.

    PubMed

    Le, Anh; Steimle, Timothy C; Skripnikov, Leonid; Titov, Anatoly V

    2013-03-28

    The (1,0) [17.9]2.5-X(2)Δ(3∕2) band of hafnium monofluoride (HfF) has been recorded using high-resolution laser-induced fluorescence spectroscopy both field-free and in the presence of a static electric field. The field-free spectra of (177)HfF, (179)HfF, and (180)HfF were modeled to generate a set of fine and hyperfine parameter for the X(2)Δ(3∕2)(v = 0) and [17.9]2.5 (v = 1) states. The observed optical Stark shifts for the (180)HfF isotopologue were analyzed to produce the molecular frame electric dipole moments of 1.66(1) D and 0.419(7) D for the X(2)Δ(3∕2) and [17.9]2.5 state, respectively. Both the generalized effective core potential and all-electron four component approaches were used in ab initio calculations to predict the properties of ground state HfF including equilibrium distance, dipole moments, quadrupole coupling, and magnetic hyperfine constants.

  9. Synthesis of cubic zirconium and hafnium nitride having Th3P4 structure.

    PubMed

    Zerr, Andreas; Miehe, Gerhard; Riedel, Ralf

    2003-03-01

    High-pressure synthesis is a powerful method for the preparation of novel materials with high elastic moduli and hardness. Additionally, such materials may exhibit interesting thermal, optoelectronic, semiconductuing, magnetic or superconducting properties. Here, we report on the high-pressure synthesis of zirconium and hafnium nitrides with the stoichiometry M3N4, where M = Zr, Hf. Synthesis experiments were performed in a laser-heated diamond anvil cell at pressures up to 18 GPa and temperatures up to 3,000 K. We observed formation of cubic Zr3N4 and Hf3N4 (c-M3N4) with a Th3P4-structure, where M-cations are eightfold coordinated by N anions. The c-M3N4 phases are the first binary nitrides with such a high coordination number. Both compounds exhibit high bulk moduli around 250 GPa, which indicates high hardness. Moreover, the new nitrides, c-Zr3N4 and c-Hf3N4, may be the first members of a larger group of transition metal and/or lanthanide nitrides with interesting ferromagnetic or superconducting behaviour.

  10. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect

    Vargas, Mirella; Murphy, N. R.; Ramana, C. V.

    2014-03-10

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

  11. Dinitrogen functionalization with bis(cyclopentadienyl) complexes of zirconium and hafnium.

    PubMed

    Chirik, Paul J

    2007-01-01

    The rich chemistry of substituted bis(cyclopentadienyl)zirconium and hafnium complexes bearing side-on coordinated dinitrogen ligands is highlighted in this Perspective. Our studies in this area were initially motivated by the desire to understand side-on vs. end-on dinitrogen coordination in bimetallic zirconocene and hafnocene N2 compounds. In the cases where eta2,eta2-dinitrogen compounds were isolated, both structural and computational data have established significant imido character in the metal-nitrogen bonds. This additional bonding interaction, which is diminished in end-on complexes bearing both terminal and bridging N2 ligands, facilitates dinitrogen functionalization by non-polar reagents including dihydrogen, carbon-hydrogen bonds and weak Brønsted acids such as water and ethanol. In hafnocene chemistry, where unwanted side-on, end-on isomerization is suppressed, cycloaddition of phenylisocyanate to coordinated N2 has also been accomplished. For N-H bond forming reactions involving H2, kinetic measurements, in addition to isotopic labelling and computational studies, are consistent with dinitrogen functionalization by 1,2-addition involving a highly ordered, four-centred transition structure.

  12. Carrier Transport at Metal/Amorphous Hafnium-Indium-Zinc Oxide Interfaces.

    PubMed

    Kim, Seoungjun; Gil, Youngun; Choi, Youngran; Kim, Kyoung-Kook; Yun, Hyung Joong; Son, Byoungchul; Choi, Chel-Jong; Kim, Hyunsoo

    2015-10-14

    In this paper, the carrier transport mechanism at the metal/amorphous hafnium-indium-zinc oxide (a-HIZO) interface was investigated. The contact properties were found to be predominantly affected by the degree of interfacial reaction between the metals and a-HIZO; that is, a higher tendency to form metal oxide phases leads to excellent Ohmic contact via tunneling, which is associated with the generated donor-like oxygen vacancies. In this case, the Schottky-Mott theory is not applicable. Meanwhile, metals that do not form interfacial metal oxide, such as Pd, follow the Schottky-Mott theory, which results in rectifying Schottky behavior. The Schottky characteristics of the Pd contact to a-HIZO can be explained in terms of the barrier inhomogeneity model, which yields a mean barrier height of 1.40 eV and a standard deviation of 0.14 eV. The work function of a-HIZO could therefore be estimated as 3.7 eV, which is in good agreement with the ultraviolet photoelectron spectroscopy (3.68 eV). Our findings will be useful for establishing a strategy to form Ohmic or Schottky contacts to a-HIZO films, which will be essential for fabricating reliable high-performance electronic devices.

  13. Carrier Transport at Metal/Amorphous Hafnium-Indium-Zinc Oxide Interfaces.

    PubMed

    Kim, Seoungjun; Gil, Youngun; Choi, Youngran; Kim, Kyoung-Kook; Yun, Hyung Joong; Son, Byoungchul; Choi, Chel-Jong; Kim, Hyunsoo

    2015-10-14

    In this paper, the carrier transport mechanism at the metal/amorphous hafnium-indium-zinc oxide (a-HIZO) interface was investigated. The contact properties were found to be predominantly affected by the degree of interfacial reaction between the metals and a-HIZO; that is, a higher tendency to form metal oxide phases leads to excellent Ohmic contact via tunneling, which is associated with the generated donor-like oxygen vacancies. In this case, the Schottky-Mott theory is not applicable. Meanwhile, metals that do not form interfacial metal oxide, such as Pd, follow the Schottky-Mott theory, which results in rectifying Schottky behavior. The Schottky characteristics of the Pd contact to a-HIZO can be explained in terms of the barrier inhomogeneity model, which yields a mean barrier height of 1.40 eV and a standard deviation of 0.14 eV. The work function of a-HIZO could therefore be estimated as 3.7 eV, which is in good agreement with the ultraviolet photoelectron spectroscopy (3.68 eV). Our findings will be useful for establishing a strategy to form Ohmic or Schottky contacts to a-HIZO films, which will be essential for fabricating reliable high-performance electronic devices. PMID:26411354

  14. Ion-assisted deposition of moisture-stable hafnium oxide films for ultraviolet applications

    NASA Astrophysics Data System (ADS)

    Jensen, Traci R.; Warren, John; Johnson,, Robert L., Jr.

    2002-06-01

    A design-of-experiments statistical approach was taken to determine the optimum ion gun operating parameters for the deposition of moisture-stable, low-absorbing hafnium oxide films by ion-assisted electron-beam evaporation. Factors identified as affecting the quality of hafnia films were chamber pressure, deposition rate, ion gun source gas composition, and ion gun current. Both oxygen and argon were used as source gases. High and low levels of the factors were chosen on the basis of our experience with the operating range of the system, and we made a series of 24 runs with all possible combinations of these factors. From a statistical analysis of the data, we find that the best films are obtained with a 1:1 mixture of argon and oxygen, 3-3.5 x 10-4 Torr chamber pressure, 0.3-nm/s deposition rate, and 0.5-A ion gun current. X-ray diffraction measurements show that the ion-assisted films exhibit a partial monoclinic crystalline structure, whereas the unassisted films are amorphous.

  15. Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

    SciTech Connect

    Xiao, Zhigang; Kisslinger, Kim

    2015-06-17

    Thin films of hafnium dioxide (HfO2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ring oscillator to test the quality of the HfO2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO2 thin film functioned very well as the gate oxide.

  16. Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

    DOE PAGES

    Xiao, Zhigang; Kisslinger, Kim

    2015-06-17

    Thin films of hafnium dioxide (HfO2) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ring oscillator to test themore » quality of the HfO2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO2 thin film functioned very well as the gate oxide.« less

  17. Low temperature structural phase transition in hafnium and zirconium tetrafluoride trihydrates

    NASA Astrophysics Data System (ADS)

    Dey, S. K.; Dey, C. C.; Saha, S.

    2016-04-01

    From time-differential perturbed angular correlation (TDPAC) measurements, the monoclinic and triclinic crystal structures in hafnium and zirconium tetrafluoride trihydrates are found to be present simultaneously in both the compounds. From previous TDPAC and XRD investigations, a monoclinic crystal structure for HfF4·3H2O but, for its analogues zirconium compound, a triclinic structure was reported. Contrary to earlier reports, the triclinic fraction in HfF4·3H2O is found to be maximum (80%) at room temperature. In fact, the triclinic crystal structure of HfF4·3H2O is reported here which was not known prior to this report. In ZrF4·3H2O, a strong signal (80-90%) for the triclinic structure is found at room temperature while the monoclinic fraction appears as a weak signal (10-15%). Structural phase transitions in these trihydrate compounds have been observed in the temperature range 298-333 K.

  18. Arc Jet Testing of Hafnium Diboride Based Ultra High Temperature Ceramics

    NASA Technical Reports Server (NTRS)

    Ellerby, Don; Beckman, Sarah; Irby, Edward; Squire, Tom; Olejniczak, Joe; Johnson, Sylvia M.; Gusman, Michael; Gasch, Matthew

    2003-01-01

    Hafnium Diboride (HFB,) based materials have shown promise for use in a number of high temperature aerospace applications, including rocket nozzles and as leading edges on hypersonic reentry vehicles. The stability of the materials in relevant environments is key to determining their suitability for a particular application. In this program we have been developing HfB2/SiC materials for use as sharp leading edges. The program as a whole included processing and characterization of the HfBJSiC materials. The specific work discussed here will focus on studies of the materials oxidation behavior in simulated reentry environments through arc jet testing. Four flat face models were tested to examine the influence of heat flux and stagnation pressure on the materials oxidation behavior. The results from arc jet testing of two HfB2/SiC cone models will also be discussed. Each cone model was run multiple times with gradually increasing heat fluxes. Total run times on a single cone model exceeded 80 minutes. For both the flat face and cone models surface temperatures well in excess of 2200 C were measured. Post test microstructural examination of the models and correlations with measured temperatures will be discussed.

  19. Measurement and Simulation of Thermal Conductivity of Hafnium-Aluminum Thermal Neutron Absorber Material

    NASA Astrophysics Data System (ADS)

    Guillen, Donna Post; Harris, William H.

    2016-09-01

    A metal matrix composite (MMC) material composed of hafnium aluminide (Al3Hf) intermetallic particles in an aluminum matrix has been identified as a promising material for fast flux irradiation testing applications. This material can filter thermal neutrons while simultaneously providing high rates of conductive cooling for experiment capsules. The purpose of this work is to investigate effects of Hf-Al material composition and neutron irradiation on thermophysical properties, which were measured before and after irradiation. When performing differential scanning calorimetry (DSC) on the irradiated specimens, a large exotherm corresponding to material annealment was observed. Therefore, a test procedure was developed to perform DSC and laser flash analysis (LFA) to obtain the specific heat and thermal diffusivity of pre- and post-annealment specimens. This paper presents the thermal properties for three states of the MMC material: (1) unirradiated, (2) as-irradiated, and (3) irradiated and annealed. Microstructure-property relationships were obtained for the thermal conductivity. These relationships are useful for designing components from this material to operate in irradiation environments. The ability of this material to effectively conduct heat as a function of temperature, volume fraction Al3Hf, radiation damage, and annealing is assessed using the MOOSE suite of computational tools.

  20. Temperature effect on electrospinning of nanobelts: the case of hafnium oxide.

    PubMed

    Su, Yurong; Lu, Bingan; Xie, Yizhu; Ma, Ziwei; Liu, Lixin; Zhao, Haiting; Zhang, Jia; Duan, Huigao; Zhang, Hongliang; Li, Jian; Xiong, Yuqing; Xie, Erqing

    2011-07-15

    Electrospinning is a convenient and versatile method for fabricating different kinds of one-dimensional nanostructures such as nanofibres, nanotubes and nanobelts. Environmental parameters have a great influence on the electrospinning nanostructure. Here we report a new method to fabricate hafnium oxide (HfO(2)) nanobelts. HfO(2) nanobelts were prepared by electrospinning a sol-gel solution with the implementation of heating and subsequent calcination treatment. We investigate the temperature dependence of the products by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive x-ray (EDX) spectroscopy. The heating temperature of spinning ambient is found to be crucial to the formation of HfO(2) nanobelts. By tuning the temperature, the morphological transformation of HfO(2) from nanowires to nanobelts was achieved. It was found that the rapid evaporation of solvent played an important role in the formation process of HfO(2) nanobelts. It is shown that nanobelts can only be obtained with the temperature higher than 50 °C and they are in the high quality monoclinic phase. A possible growth mechanism of the nanobelts based on phase separation is proposed. The enhanced photoluminescence (PL) of HfO(2):Eu(3+) nanobelts is also illustrated.

  1. Dry Sliding Wear Behavior of Hafnium-Based Bulk Metallic Glass at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Keshri, Anup Kumar; Behl, Lovish; Lahiri, Debrupa; Dulikravich, George S.; Agarwal, Arvind

    2016-09-01

    Dry sliding wear behavior of hafnium-based bulk metallic glass was studied at two loads (5 and 15 N) and two temperatures (298 and 673 K) using aluminum oxide (Al2O3) ball as a wear counterpart. At 5 N load, wear reduced by ~71% on increasing the temperature from 298 to 673 K. At a higher load of 15 N, the weight loss reduction was much lower (45%) on increasing the temperature from 298 to 673 K. Decreased wear weight loss on increasing the temperature was attributed to the increased hardness of the Hf-based metallic glass at high temperatures. Micro-hardness of the alloy at 293 K was found to be 636 Hv, which gradually increased to 655 Hv on annealing at 673 K. Improvement in the hardness at elevated temperature is attributed to: (1) free volume annihilation, (2) surface oxide formation and (3) nano-crystallites precipitation. Reduced wear at elevated temperature resulted in smaller volume of debris generation that restricted three-body wear to obtain lower coefficient of friction (COF) (0.25-0.35) compared to COF (0.65-0.75) at room temperature.

  2. Facing-target mid-frequency magnetron reactive sputtered hafnium oxide film: Morphology and electrical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Xu, Jun; Wang, You-Nian; Choi, Chi Kyu; Zhou, Da-Yu

    2016-03-01

    Amorphous hafnium dioxide (HfO2) film was prepared on Si (100) by facing-target mid-frequency reactive magnetron sputtering under different oxygen/argon gas ratio at room temperature with high purity Hf target. 3D surface profiler results showed that the deposition rates of HfO2 thin film under different O2/Ar gas ratio remain unchanged, indicating that the facing target midfrequency magnetron sputtering system provides effective approach to eliminate target poisoning phenomenon which is generally occurred in reactive sputtering procedure. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) demonstrated that the gradual reduction of oxygen vacancy concentration and the densification of deposited film structure with the increase of oxygen/argon (O2/Ar) gas flow ratio. Atomic force microscopy (AFM) analysis suggested that the surface of the as-deposited HfO2 thin film tends to be smoother, the root-meansquare roughness (RMS) reduced from 0.876 nm to 0.333 nm while O2/Ar gas flow ratio increased from 1/4 to 1/1. Current-Voltage measurements of MOS capacitor based on Au/HfO2/Si structure indicated that the leakage current density of HfO2 thin films decreased by increasing of oxygen partial pressure, which resulted in the variations of pore size and oxygen vacancy concentration in deposited thin films. Based on the above characterization results the leakage current mechanism for all samples was discussed systematically.

  3. Dry Sliding Wear Behavior of Hafnium-Based Bulk Metallic Glass at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Keshri, Anup Kumar; Behl, Lovish; Lahiri, Debrupa; Dulikravich, George S.; Agarwal, Arvind

    2016-07-01

    Dry sliding wear behavior of hafnium-based bulk metallic glass was studied at two loads (5 and 15 N) and two temperatures (298 and 673 K) using aluminum oxide (Al2O3) ball as a wear counterpart. At 5 N load, wear reduced by ~71% on increasing the temperature from 298 to 673 K. At a higher load of 15 N, the weight loss reduction was much lower (45%) on increasing the temperature from 298 to 673 K. Decreased wear weight loss on increasing the temperature was attributed to the increased hardness of the Hf-based metallic glass at high temperatures. Micro-hardness of the alloy at 293 K was found to be 636 Hv, which gradually increased to 655 Hv on annealing at 673 K. Improvement in the hardness at elevated temperature is attributed to: (1) free volume annihilation, (2) surface oxide formation and (3) nano-crystallites precipitation. Reduced wear at elevated temperature resulted in smaller volume of debris generation that restricted three-body wear to obtain lower coefficient of friction (COF) (0.25-0.35) compared to COF (0.65-0.75) at room temperature.

  4. Investigation of crystallization processes from hafnium silicate powders prepared from an oxychloride sol-gel

    SciTech Connect

    McGilvery, Catriona M.; De Gendt, S; Payzant, E Andrew; Craven, A J; MacKenzie, M; McComb, D W

    2012-01-01

    Hafnium oxide and silicate materials are now incorporated into working CMOS devices, however the crystallisation mechanism is still poorly understood. In particular, addition of SiO2 to HfO2 has been shown to increase the crystallisation temperature of HfO2 hence allowing it to remain amorphous under current processing conditions. Building on earlier work we here investigate bulk HfxSi1-xO2 samples to determine the effect of SiO2 on the crystallisation pathway. Techniques such as XRD, HTXRD, thermal analysis techniques and TEM are used. It is found that the addition of SiO2 has very little affect on the crystallisation path at temperatures below 900 C but at higher temperatures a second t-HfO2 phase nucleates and is stabilised due to the strain of the surrounding amorphous SiO2 material. With an increase in SiO2 content the temperature at which this nucleation and stabilisation occurs is increased. The effect of strain has implications for inhibiting the crystallisation of the high-k layer, reduction of grain boundaries and hence diffusion, reduction of formation of interface layers and the possibility of stabilising t-HfO2 rather than m-HfO2 hence increasing the dielectric of the layer.

  5. Novel synthesis of hafnium oxide nanoparticles by precipitation method and its characterization

    SciTech Connect

    Ramadoss, Ananthakumar; Krishnamoorthy, Karthikeyan; Kim, Sang Jae

    2012-09-15

    Highlights: ► HfO{sub 2} NPs were prepared by precipitation method. ► XRD and Raman analysis revealed the presence of monoclinic phase. ► The average particle size of HfO{sub 2} NPs is 20 nm. ► The method is a simple, low cost and eco-friendly approach. -- Abstract: Hafnium oxide nanoparticles (HfO{sub 2} NPs) have been successfully synthesized by means of a novel precipitation method and were characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), UV–visible, Fourier transform infrared (FTIR) and laser Raman spectroscopy. The XRD and Raman analysis revealed the presence of pure monoclinic HfO{sub 2} NPs. FESEM image showed that the HfO{sub 2} NPs were of spherical shape with an average particle size of about 20 nm. The optical band gap of the HfO{sub 2} NPs was found to be 6.12 eV. Advantages of this method were simple and low cost of synthesis of HfO{sub 2} NPs includes the small and narrow particle size distribution.

  6. Ion-assisted deposition of moisture-stable hafnium oxide films for ultraviolet applications.

    PubMed

    Jensen, Traci R; Warren, John; Johnson, Robert L

    2002-06-01

    A design-of-experiments statistical approach was taken to determine the optimum ion gun operating parameters for the deposition of moisture-stable, low-absorbing hafnium oxide films by ion-assisted electron-beam evaporation. Factors identified as affecting the quality of hafnia films were chamber pressure, deposition rate, ion gun source gas composition, and ion gun current. Both oxygen and argon were used as source gases. High and low levels of the factors were chosen on the basis of our experience with the operating range of the system, and we made a series of 24 runs with all possible combinations of these factors. From a statistical analysis of the data, we find that the best films are obtained with a 1:1 mixture of argon and oxygen, 3-3.5 x 10(-4) Torr chamber pressure, 0.3-nm/s deposition rate, and 0.5-A ion gun current. X-ray diffraction measurements show that the ion-assisted films exhibit a partial monoclinic crystalline structure, whereas the unassisted films are amorphous.

  7. Sulfiding of hydrogel derived catalysts

    SciTech Connect

    Kemp, R.A.

    1991-11-05

    This patent describes a process for hydrotreating hydrocarbon feeds. It comprises contacting the feeds at a temperature in the range of from about 400{degrees} F. to about 850{degrees} F. and a pressure in the range of from about 400 psig to about 2500 psig with a catalyst having improved desulfurization activity prepared by incorporating an element selected from the group consisting of nickel, cobalt and mixtures thereof, and a heavy metal selected from the group consisting of molybdenum, tungsten and mixtures thereof, into an alumina hydrogel containing a phosphorous-containing compound, and sulfiding the catalyst with a gaseous sulfur compound at a temperature of at least about 900{degrees} F. for at least one hour.

  8. Pelletizing of sulfide molybdenite concentrates

    NASA Astrophysics Data System (ADS)

    Palant, A. A.

    2007-04-01

    The results of a pelletizing investigation using various binding components (water, syrup, sulfite-alcohol distillery grains, and bentonite) of the flotation sulfide molybdenite concentrate (˜84% MoS2) from the Mongolian deposit are discussed. The use of syrup provides rather high-strength pellets (>3 N/pellet or >300 g/pellet) of the required size (2 3 mm) for the consumption of 1 kg binder per 100 kg concentrate. The main advantage of the use of syrup instead of bentonite is that the molybdenum cinder produced by oxidizing roasting of raw ore materials is not impoverished due to complete burning out of the syrup. This fact exerts a positive effect on the subsequent hydrometallurgical process, decreasing molybdenum losses related to dump cakes.

  9. [Hydrogen sulfide and penile erection].

    PubMed

    Huang, Yi-Ming; Cheng, Yong; Jiang, Rui

    2012-09-01

    Hydrogen sulfide (H2S) is the third type of active endogenous gaseous signal molecule following nitric oxide (NO) and carbon monoxide (CO). In mammalians, H2S is mainly synthesized by two proteases, cystathionine-beta-synthase (CBS) and cystathionine-gamma-lyase (CSE). H2S plays an essential function of physiological regulation in vivo, and promotes penile erection by acting on the ATP-sensitive potassium channels to relax the vascular smooth muscle as well as by the synergistic effect with testosterone and NO to relax the corpus cavernosum smooth muscle (CCSM). At present, the selective phosphodiesterase type 5 (PDE5) inhibitor is mainly used for the treatment of erectile dysfunction (ED), but some ED patients fail to respond. Therefore, further studies on the mechanism of H2S regulating penile erection may provide a new way for the management of erectile dysfunction.

  10. Structural studies in limestone sulfidation

    SciTech Connect

    Fenouil, L.A.; Lynn, S.

    1993-05-01

    This study investigates the sulfidation of limestone at high temperatures (700--900{degree}C) as the first step in the design of a High-Temperature Coal-Gas Clean-Up system using millimeter-size limestone particles. Several workers have found that the rate of this reaction significantly decreases after an initial 10 to 15% conversion of CaCO{sub 3} to CaS. The present work attempts to explain this feature. It is first established that millimeter-size limestone particles do not sinter at temperatures up to the CaCO{sub 3} calcination point (899{degree}C at 1.03 bar CO{sub 2} partial pressure). It is then shown that CaS sinters rapidly at 750 to 900{degree}C if CO{sub 2} is present in the gas phase. Scanning Electron Microscope (SEM) photographs and Electron Dispersive Spectroscopy (EDS) data reveal that the CaS product layer sinters and forms a quasi-impermeable coating around the CaCO{sub 3} grains that greatly hinders more H{sub 2}S from reaching the still unreacted parts of the stone. Moreover, most of the pores initially present within the limestone structure begin to disappear or, at least, are significantly reduced in size. From then on, subsequent conversion is limited by diffusion of H{sub 2}S through the CaS layer, possibly by S{sup 2{minus}} ionic diffusion. The kinetics is then adequately described by a shrinking-core model, in which a sharp front of completely converted limestone is assumed to progress toward the center of the pellet. Finally, experimental evidence and computer simulations using simple sintering models suggest that the CaS sintering, responsible for the sharp decrease in the sulfidation rate, is surface-diffusion controlled.

  11. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  12. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  13. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  14. 21 CFR 73.2995 - Luminescent zinc sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Luminescent zinc sulfide. 73.2995 Section 73.2995... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2995 Luminescent zinc sulfide. (a) Identity. The color additive luminescent zinc sulfide is zinc sulfide containing a copper activator....

  15. 21 CFR 177.2490 - Polyphenylene sulfide resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyphenylene sulfide resins. 177.2490 Section 177... Components of Articles Intended for Repeated Use § 177.2490 Polyphenylene sulfide resins. Polyphenylene sulfide resins (poly(1,4-phenylene sulfide) resins) may be safely used as coatings or components...

  16. Nanostructured lead sulfide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Rempel, A. A.

    2016-07-01

    The theoretical and experimental results of recent studies dealing with nanostructured lead sulfide are summarized and analyzed. The key methods for the synthesis of nanostructured lead sulfide are described. The crystal structure of PbS in nanopowders and nanofilms is discussed. The influence of the size of nanostructure elements on the optical and thermal properties of lead sulfide is considered. The dependence of the band gap of PbS on the nanoparticle (crystallite) size for powders and films is illustrated. The bibliography includes 222 references.

  17. Microbial control of hydrogen sulfide production

    SciTech Connect

    Montgomery, A.D.; Bhupathiraju, V.K.; Wofford, N.; McInerney, M.J.

    1995-12-31

    A sulfide-resistant strain of Thiobacillus denitrificans, strain F, prevented the accumulation of sulfide by Desulfovibrio desulfuricans when both organisms were grown in liquid medium. The wild-type strain of T. denitrificans did not prevent the accumulation of sulfide produced by D. desulfuricans. Strain F also prevented the accumulation of sulfide by a mixed population of sulfate-reducing bacteria enriched from an oil field brine. Fermentation balances showed that strain F stoichiometrically oxidized the sulfide produced by D. desulfuricans and the oil field brine enrichment to sulfate. The ability of a strain F to control sulfide production in an experimental system of cores and formation water from the Redfield, Iowa, natural gas storage facility was also investigated. A stable, sulfide-producing biofilm was established in two separate core systems, one of which was inoculated with strain F while the other core system (control) was treated in an identical manner, but was not inoculated with strain F. When formation water with 10 mM acetate and 5 mM nitrate was injected into both core systems, the effluent sulfide concentrations in the control core system ranged from 200 to 460 {mu}M. In the test core system inoculated with strain F, the effluent sulfide concentrations were lower, ranging from 70 to 110 {mu}M. In order to determine whether strain F could control sulfide production under optimal conditions for sulfate-reducing bacteria, the electron donor was changed to lactate and inorganic nutrients (nitrogen and phosphate sources) were added to the formation water. When nutrient-supplemented formation water with 3.1 mM lactate and 10 mM nitrate was used, the effluent sulfide concentrations of the control core system initially increased to about 3,800 {mu}M, and then decreased to about 1,100 {mu}M after 5 weeks. However, in the test core system inoculated with strain F, the effluent sulfide concentrations were much lower, 160 to 330 {mu}M.

  18. In-Pile Experiment of a New Hafnium Aluminide Composite Material to Enable Fast Neutron Testing in the Advanced Test Reactor

    SciTech Connect

    Donna Post Guillen; Douglas L. Porter; James R. Parry; Heng Ban

    2010-06-01

    A new hafnium aluminide composite material is being developed as a key component in a Boosted Fast Flux Loop (BFFL) system designed to provide fast neutron flux test capability in the Advanced Test Reactor. An absorber block comprised of hafnium aluminide (Al3Hf) particles (~23% by volume) dispersed in an aluminum matrix can absorb thermal neutrons and transfer heat from the experiment to pressurized water cooling channels. However, the thermophysical properties, such as thermal conductivity, of this material and the effect of irradiation are not known. This paper describes the design of an in-pile experiment to obtain such data to enable design and optimization of the BFFL neutron filter.

  19. Investigation on laboratory and pilot-scale airlift sulfide oxidation reactor under varying sulfide loading rate.

    PubMed

    Pokasoowan, Chanya; Kanitchaidecha, Wilawan; K C, Bal Krishna; Annachhatre, Ajit P

    2009-01-01

    Airlift bioreactor was established for recovering sulfur from synthetic sulfide wastewater under controlled dissolved oxygen condition. The maximum recovered sulfur was 14.49 g/day when sulfide loading rate, dissolved oxygen (DO) and pH values were 2.97 kgHS(-)/m(3)-day, 0.2-1.0 mg/L and 7.2-7.8, respectively. On the other hand, the increase in recovered sulfur reduced the contact surface of sulfide oxidizing bacteria which affects the recovery process. This effect caused to reduce the conversion of sulfide to sulfur. More recovered sulfur was produced at high sulfide loading rate due to the change of metabolic pathway of sulfide-oxidizing bacteria which prevented the toxicity of sulfide in the culture. The maximum activity in this system was recorded to be about 3.28 kgS/kgVSS-day. The recovered sulfur contained organic compounds which were confirmed by the results from XRD and CHN analyzer. Afterwards, by annealing the recovered sulfur at 120 degrees C for 24 hrs under ambient Argon, the percentage of carbon reduced from 4.44% to 0.30%. Furthermore, the percentage of nitrogen and hydrogen decreased from 0.79% and 0.48% to 0.00% and 0.14%, respectively. This result showed the success in increasing the purity of recovered sulfur by using the annealing technique. The pilot-scale biological sulfide oxidation process was carried out using real wastewater from Thai Rayon Industry in Thailand. The airlift reactor successfully removed sulfide more than 90% of the influent sulfide at DO concentration of less than 0.1 mg/L, whereas the elementary sulfur production was 2.37 kgS/m(3)-day at sulfide loading rate of 2.14 kgHS(-)/m(3)-day. The sulfur production was still increasing as the reactor had not yet reached its maximum sulfide loading rate. PMID:19085599

  20. Routes to new hafnium(IV) tetraaryl porphyrins and crystal structures of unusual phosphate-, sulfate-, and peroxide-bridged dimers.

    PubMed

    Falber, Alexander; Todaro, Louis; Goldberg, Israel; Favilla, Michael V; Drain, Charles Michael

    2008-01-21

    New routes for the synthesis of mono tetraaryl porphyrinato hafnium(IV) complexes, Hf(IV)Por(L)(2), are reported, where the secondary ligands, L, are determined by the method of purification. These synthetic routes cater to the solubility of the macrocycles and provide access to Hf(IV) complexes of meso tetraaryl porphyrins bearing diverse functional groups such as phenyl, tolyl, pyridyl, pentafluorophenyl, and carboxyphenyl. The latter three derivatives significantly expand the repertoire of hafnium porphyrinates. One route refluxes the porphyrin with HfCl(4) in 1-chloronaphthalene or in a mixed solvent of 1-chloronaphthalene and o-cresol. A second, solventless method is also reported wherein the porphyrin is mixed with Hf(cp)(2)Cl(2) and heated to give the metalated porphyrin in good yields. Simultaneous purification and formation of stable porphyrinato hafnium(IV) diacetate complexes, Hf(Por)OAc(2), is accomplished by elution over silica gel using 3-5% acetic acid in the eluent. Exchange of the acetate ligands for other oxo-bearing ligands can be nearly quantitative, such as p-aminobenzoate (PABA), pentanoate (pent), or octanoate (oct). Notably, we find that two to three of a variety of small multitopic dianions such as peroxo (O(2)(-2)), SO(4)(-2), and HPO(4)(-2) serve to bridge between two Hf(Por) moieties to form stable dimers. The crystal structures of this library of Hf(Por) complexes are reported, and we note that careful analysis of crystallography data reveals (Por)Hf(micro-eta(2)-O(2))(2)Hf(Por) rather than four bridging oxo or hydroxy ions.

  1. Sulfidation of iron at high temperatures and diffusion kinetics in ferrous sulfide

    SciTech Connect

    Danielewski, M.; Mrowec, S.; Stoklosa, A.

    1982-02-01

    The kinetics and mechanism of iron sulfidation have been studied as a function of temperature (950-1200 K) and sulfur pressure (10/sup -3/ 0.065 atm). It has been stated that a compact Fe/sub 1-y/ S scale on iron grows according to the parabolic rate law as a result of outward lattice diffusion of metal ions through cation vacancies. The activation energy of sulfidation increases with sulfur pressure and the 1/n exponent increases with temperature. This nontypical dependence of iron sulfidation kinetics on temperature and pressure results from the analogous effect of both these parameters on defect concentration in ferrous sulfide. The chemical diffusion coefficients, D/sub FeS/ , and diffusion coefficients of defects, D/sub d/ , in ferrous sulfide have been calculated on the basis of parabolic rate contacts of iron sulfidation and deviations from stoichiometry in ferrous sulfide. It has been shown that D/sub FeS/ is practically independent of cation vacancy concentration whereas the diffusion coefficient of defects depends strongly on that parameter. A comparison of self-diffusion coefficients of iron in Fe/sub 1-y/ S calculated from the kinetics of iron sulfidation to those obtained from radioisotopic studies indicates that within the range studied of temperatures and sulfur vapor pressures the outward diffusion of iron across the scale occurs preferentially along the c axis of columnar ferrous sulfide crystals.

  2. Effect of nitrogen on tensile properties and structures of T-111 (tantalum, 8 percent tungsten, 2 percent hafnium) tubing

    NASA Technical Reports Server (NTRS)

    Buzzard, R. J.; Metroka, R. R.

    1973-01-01

    The effect of controlled nitrogen additions was evaluated on the mechanical properties of T-111 (Ta-8W-2Hf) fuel pin cladding material proposed for use in a lithium-cooled nuclear reactor concept. Additions of 80 to 1125 ppm nitrogen resulted in increased strengthening of T-111 tubular section test specimens at temperatures of 25 to 1200 C. Homogeneous distributions of up to 500 ppm nitrogen did not seriously decrease tensile ductility. Both single and two-phase microstructures, with hafnium nitride as the second phase, were evaluated in this study.

  3. Zirconium and hafnium complexes based on 2-aryl-8-arylaminoquinoline ligands: synthesis, molecular structure, and catalytic performance in ethylene copolymerization.

    PubMed

    Nifant'ev, Ilya E; Ivchenko, Pavel V; Bagrov, Vladimir V; Nagy, Sandor M; Winslow, Linda N; Merrick-Mack, Jean A; Mihan, Shahram; Churakov, Andrei V

    2013-02-01

    A general and efficient approach toward new zirconium and hafnium complexes based on 2-aryl-8-arylaminoquinoline ligands was developed. These precursors, when activated with MAO/borate cocatalyst and supported on silica, result in active olefin polymerization catalysts. The ethylene copolymers produced under industrially relevant conditions show very high molecular weights and unique microstructures defined by the multisite nature of the catalyst. A site-diversification mechanism is proposed to explain the presence of at least five individual sites, as deduced from 3D-TREF analysis of ethylene-butene copolymers.

  4. Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago.

    PubMed

    Næraa, T; Scherstén, A; Rosing, M T; Kemp, A I S; Hoffmann, J E; Kokfelt, T F; Whitehouse, M J

    2012-05-31

    Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens. These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate

  5. Ridding Groundwater of Hydrogen Sulfide. Part 1.

    ERIC Educational Resources Information Center

    Lochrane, Thomas G.

    1979-01-01

    This article is the first in a series reviewing the problems associated with hydrogen sulfide in drinking water sources. Discussion centers on identification of a cost-effective balance between aeration and chlorination treatment operations. (AS)

  6. Selenium sulfide: adjunctive therapy for tinea capitis.

    PubMed

    Allen, H B; Honig, P J; Leyden, J J; McGinley, K J

    1982-01-01

    Selenium sulfide lotion used as a shampoo has been shown to be an effective adjunctive agent to griseofulvin in the treatment of tinea capitis. Of 16 children with Trichophyton tonsurans infections 15 had negative fungal cultures at two weeks following a regimen of daily oral griseofulvin and selenium sulfide shampooing twice weekly. All patients treated with griseofulvin alone or in combination with either a bland shampoo or topical clotrimazole had positive cultures not only at the two-week interval but also as long as eight weeks later. In vitro analysis shows selenium sulfide to be sporicidal, correlating well with the in vivo observations. It is postulated that selenium sulfide usage may lessen the chances for spreading of infectious spores to other individuals.

  7. The Search for Interstellar Sulfide Grains

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Messenger, Scott

    2010-01-01

    The lifecycle of sulfur in the galaxy is poorly understood. Fe-sulfide grains are abundant in early solar system materials (e.g. meteorites and comets) and S is highly depleted from the gas phase in cold, dense molecular cloud environments. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium, indicating that little sulfur is incorporated into solid grains in this environment. It is widely believed that sulfur is not a component of interstellar dust grains. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. Fe sulfide grains are ubiquitous in cometary samples where they are the dominant host of sulfur. The Fe-sulfides (primarily pyrrhotite; Fe(1-x)S) are common, both as discrete 0.5-10 micron-sized grains and as fine (5-10 nm) nanophase inclusions within amorphous silicate grains. Cometary dust particles contain high abundances of well-preserved presolar silicates and organic matter and we have suggested that they should contain presolar sulfides as well. This hypothesis is supported by the observation of abundant Fe-sulfides grains in dust around pre- and post-main sequence stars inferred from astronomical spectra showing a broad 23 micron IR feature due to FeS. Fe-sulfide grains also occur as inclusions in bona fide circumstellar amorphous silicate grains and as inclusions within deuterium-rich organic matter in cometary dust samples. Our irradiation experiments show that FeS is far more resistant to radiation damage than silicates. Consequently, we expect that Fe sulfide stardust should be as abundant as silicate stardust in solar system materials.

  8. Upper critical field of copper molybdenum sulfide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Woollam, J. A.

    1978-01-01

    The upper critical field of sintered and sputtered copper molybdenum sulfide Cu(x)Mo6S8 was measured and found to exceed the Werthamer, Helfand, and Hohenberg (1966) value for a type II superconductor characterized by dirty limit, weak isotropic electron phonon coupling, and no paramagnetic limiting. It is suggested that the enhancement results from anisotropy or clean limit or both. Other ternary molybdenum sulfides appear to show similar anomalies.

  9. Preparation of octahydro- and tetrahydro-[1,10]phenanthroline zirconium and hafnium complexes for olefin polymerization.

    PubMed

    Hwang, Eun Yeong; Park, Geun Ho; Lee, Chun Sun; Kang, Yi Young; Lee, Junseong; Lee, Bun Yeoul

    2015-02-28

    Post-metallocenes were constructed for olefin polymerization using 1,2,3,4,7,8,9,10-octahydro[1,10]phenanthroline and 1,2,3,4-tetrahydro[1,10]phenanthroline derivatives. A series of zirconium complexes - LZrCl2(NHMe2)2 [L = 2,9-H2-C12H12N2 (4), 2,9-Me2-C12H12N2 (5), 2,9-nBu2-C12H12N2 (6), and 2,9-iPr2-C12H12N2 (7)] - and hafnium complexes - LHfCl2(NHMe2)2 [L = 2,9-H2-C12H12N2 (8), 2,9-Me2-C12H12N2 (9), 2,9-nBu2-C12H12N2 (10), and 2,9-iPr2-C12H12N2 (11)] - were synthesized via the reaction of octahydro[1,10]phenanthrolines (2,9-R2-C12H12(NH)2) with (Me2N)2MCl2 (DME). The reaction of 2,9-R2-C12H12(NH)2 with (PhCH2)2ZrCl2 in the presence of a small amount of THF afforded a series of THF adduct analogs, i.e., LZrCl2(THF)2 [L = 2,9-H2-C12H12N2 (12), 2,9-Me2-C12H12N2 (13), 2,9-nBu2-C12H12N2 (14), and 2,9-iPr2-C12H12N2 (15)]. The treatment of 12 and 13 with excess Me3Al resulted in the formation of unexpected complexes, i.e., (η(4)-LAlMe2)ZrCl2(Me) [L = 2,9-H2-C12H12N2 (16) and 2,9-Me2-C12H12N2 (17)], in which the Me2Al unit forms a five-membered ring through binding with the two nitrogen donors and the MeCl2Zr unit slips to an η(4)-binding mode containing the N-C-C-N fragment. The treatment of tetrahydro[1,10]phenanthrolines [2,9-R2-C12NH9(NH)] with M(CH2Ph)4 afforded tribenzyl zirconium complexes LZr(CH2Ph)3 - [L = 2,9-Me2-C12NH9N (18) and 2,9-nBu2-C12NH9N (19)] - and hafnium complexes - LHf(CH2Ph)3 [L = 2,9-Me2-C12NH9N (20), 2,9-nBu2-C12NH9N (21), and 2,9-iPr2-C12NH9N (22)]. The structures of 4, 5, 12, 17, and 22 were elucidated by X-ray crystallography. The newly prepared complexes were screened for ethylene/1-octene copolymerization activity: 12 and 16 were potent catalysts (activities of 74 × 10(6) g mol-Zr h(-1) at ∼120 °C under 30 bar ethylene) for the production of wax-like low-molecular weight polyethylene (Mn: ∼5000), which is widely used in industry.

  10. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface.

    PubMed

    Nguyen, Duc; Mallek, Justin; Cloud, Andrew N; Abelson, John R; Girolami, Gregory S; Lyding, Joseph; Gruebele, Martin

    2014-11-28

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB2 has a very high bulk glass transition temperature Tg, and we observe no three-state hopping or sequential two-state hopping previously seen on lower Tg glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses.

  11. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface.

    PubMed

    Nguyen, Duc; Mallek, Justin; Cloud, Andrew N; Abelson, John R; Girolami, Gregory S; Lyding, Joseph; Gruebele, Martin

    2014-11-28

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB2 has a very high bulk glass transition temperature Tg, and we observe no three-state hopping or sequential two-state hopping previously seen on lower Tg glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses. PMID:25429948

  12. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

    NASA Astrophysics Data System (ADS)

    Nguyen, Duc; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Girolami, Gregory S.; Lyding, Joseph; Gruebele, Martin

    2014-11-01

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB2 has a very high bulk glass transition temperature Tg, and we observe no three-state hopping or sequential two-state hopping previously seen on lower Tg glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses.

  13. Effects of trimethylaluminium and tetrakis(ethylmethylamino) hafnium in the early stages of the atomic-layer-deposition of aluminum oxide and hafnium oxide on hydroxylated GaN nanoclusters.

    PubMed

    León-Plata, Paola A; Coan, Mary R; Seminario, Jorge M

    2013-10-01

    We calculate the interactions of two atomic layer deposition (ALD) reactants, trimethylaluminium (TMA) and tetrakis(ethylmethylamino) hafnium (TEMAH) with the hydroxylated Ga-face of GaN clusters when aluminum oxide and hafnium oxide, respectively, are being deposited. The GaN clusters are suitable as testbeds for the actual Ga-face on practical GaN nanocrystals of importance not only in electronics but for several other applications in nanotechnology. We find that TMA spontaneously interacts with hydroxylated GaN; however it does not follow the atomic layer deposition reaction path unless there is an excess in potential energy introduced in the clusters at the beginning of the optimization, for instance, using larger bond lengths of various bonds in the initial structures. TEMAH also does not interact with hydroxylated GaN, unless there is an excess in potential energy. The formation of a Ga-N(CH3)(CH2CH3) bond during the ALD of HfO2 using TEMAH as the reactant without breaking the Hf-N bond could be the key part of the mechanism behind the formation of an interface layer at the HfO2/GaN interface.

  14. Hydrogen sulfide and translational medicine

    PubMed Central

    Guo, Wei; Cheng, Ze-yu; Zhu, Yi-zhun

    2013-01-01

    Hydrogen sulfide (H2S) along with carbon monoxide and nitric oxide is an important signaling molecule that has undergone large numbers of fundamental investigations. H2S is involved in various physiological activities associated with the regulation of homeostasis, vascular contractility, pro- and anti-inflammatory activities, as well as pro- and anti-apoptotic activities etc. However, the actions of H2S are influenced by its concentration, reaction time, and cell/disease types. Therefore, H2S is a signaling molecule without definite effect. The use of existing H2S donors is limited because of the instant release and short lifetime of H2S. Thus, translational medicine involving the sustained and controlled release of H2S is of great value for both scientific and clinical uses. H2S donation can be manipulated by different ways, including where H2S is given, how H2S is donated, or the specific structures of H2S-releasing drugs and H2S donor molecules. This review briefly summarizes recent progress in research on the physiological and pathological functions of H2S and H2S-releasing drugs, and suggests hope for future investigations. PMID:24096643

  15. Hydrogen Sulfide as a Gasotransmitter

    PubMed Central

    Gadalla, Moataz M.; Snyder, Solomon H.

    2010-01-01

    Nitric oxide (NO) and carbon monoxide (CO) are well established as messenger molecules throughout the body, gasotransmitters, based on striking alterations in mice lacking the appropriate biosynthetic enzymes. Hydrogen sulfide (H2S) is even more chemically reactive, but till recently there was little definitive evidence for its physiologic formation. Cystathionine β-synthase (CBS, EC 4.2.1.22), and Cystathionine γ-lyase (CSE; EC 4.4.1.1), also known as cytathionase, can generate H2S from cyst(e)ine. Very recent studies with mice lacking these enzymes have established that CSE is responsible for H2S formation in the periphery, while in the brain CBS is the biosynthetic enzyme. Endothelial-derived relaxing factor (EDRF) activity is reduced 80% in the mesenteric artery of mice with deletion of CSE, establishing H2S as a major physiologic EDRF. H2S appears to signal predominantly by S-sulfhydrating cysteines in its target proteins, analogous to S-nitrosylation by NO. Whereas S-nitrosylation typically inhibits enzymes, S-sulfhydration activates them. S-nitrosylation basally affects 1–2% of its target proteins, while 10–25% of H2S target proteins are S-sulfhydrated. In summary, H2S appears to be a physiologic gasotransmitter of comparable importance to NO and CO. PMID:20067586

  16. Synthesis of a base-free hafnium nitride from N2 cleavage: a versatile platform for dinitrogen functionalization.

    PubMed

    Semproni, Scott P; Chirik, Paul J

    2013-07-31

    The synthesis and characterization of a metastable, base-free isocyanato dihafnocene μ-nitrido complex from CO-induced dinitrogen cleavage is described. The open coordination site at hafnium suggested the possibility of functionalization of the nitrogen atom by cycloaddition and insertion chemistry. Addition of the strained, activated alkyne, cyclooctyne, resulted in N-C bond formation by cycloaddition. The alkyne product is kinetically unstable engaging the terminal hafnocene isocyanate and promoting deoxygenation and additional N-C bond formation resulting in a substituted cyanamide ligand. Group transfer between hafnium centers was observed upon treatment with Me3SiCl resulting in bridging carbodiimidyl ligands. Amidinato-type ligands, [NC(R)N](3-) were prepared by addition of either cyclohexyl or isobutyronitrile to the base free dihafnocene μ-nitrido complex, which also engages in additional N-C bond formation with the terminal isocyanate to form bridging ureate-type ligands. Heterocummulenes also proved reactive as exposure of the nitride complex to CO2 resulted in deoxygenation and N-C bond formation to form isocyanate ligands. With substituted isocyanates, cycloaddition to the dihafnocene μ-nitrido was observed forming ureate ligands, which upon thermolysis isomerize to bridging carbodiimides. Taken together, these results establish the base free dihafnocene μ-nitrido as a versatile platform to synthesize organic molecules from N2 and carbon monoxide.

  17. NEAR-CONTINUOUS MEASUREMENT OF HYDROGEN SULFIDE AND CARBONYL SULFIDE BY AN AUTOMATIC GAS CHROMATOGRAPH

    EPA Science Inventory

    An automatic gas chromatograph with a flame photometric detector that samples and analyzes hydrogen sulfide and carbonyl sulfide at 30-s intervals is described. Temperature programming was used to elute trace amounts of carbon disulfide present in each injection from a Supelpak-S...

  18. Gondwanan basement terranes of the Variscan-Appalachian orogen: Baltican, Saharan and West African hafnium isotopic fingerprints in Avalonia, Iberia and the Armorican Terranes

    NASA Astrophysics Data System (ADS)

    Henderson, Bonnie J.; Collins, William Joseph; Murphy, James Brendan; Gutierrez-Alonso, Gabriel; Hand, Martin

    2016-06-01

    Iberia, Avalonia and the "Armorican" terranes form key constituents of the Variscan-Appalachian orogen, but their Neoproterozoic origins along the northern Gondwanan margin continue to be strongly debated. Here, we present a new detrital zircon U-Pb-Hf dataset from Neoproterozoic-Silurian sedimentary sequences in NW Iberia and Avalonia, in conjunction with the comprehensive existing datasets from potential source cratons, to demonstrate that the provenance of each terrane is relatively simple and can be traced back to three major cratons. The enigmatic Tonian-Stenian detrital zircons in autochthonous Iberian rocks were derived from the Saharan metacraton in the latest Neoproterozoic-early Cambrian. Avalonia is commonly considered to have been derived from the Amazonian margin of Gondwana, but the hafnium isotopic characteristics of the detrital zircon grains in early Neoproterozoic rocks bear much stronger similarities to Baltica. The hafnium isotopic array also suggests the early Avalonian oceanic arc was built on a sliver of "Grenvillian-type crust" (~ 2.0-1.0 Ga) possibly of Baltican affinity at ~ 800 Ma, prior to accretion with a continental margin at ~ 640 Ma. The Upper Allochthon of Iberia is frequently linked to the West African Craton in the late Neoproterozoic-early Cambrian, however the hafnium isotopic array presented here does not support this connection; rather it is more similar to the hafnium array from Avalonia. The Armorican terranes have strong detrital zircon isotopic links to the West African Craton during the late Neoproterozoic-Cambrian.

  19. Highly active and stereoselective zirconium and hafnium alkoxide initiators for solvent-free ring-opening polymerization of rac-lactide.

    PubMed

    Chmura, Amanda J; Davidson, Matthew G; Frankis, Catherine J; Jones, Matthew D; Lunn, Matthew D

    2008-03-21

    Under solvent-free conditions (at 130 degrees C), zirconium and hafnium amine tris(phenolate) alkoxides are extremely active, well-controlled, single-site initiators for the ring-opening polymerization of rac-lactide, yielding highly heterotactic polylactide.

  20. Continuous measurement of dissolved sulfide in sewer systems.

    PubMed

    Sutherland-Stacey, L; Corrie, S; Neethling, A; Johnson, I; Gutierrez, O; Dexter, R; Yuan, Z; Keller, J; Hamilton, G

    2008-01-01

    Sulfides are particularly problematic in the sewage industry. Hydrogen sulfide causes corrosion of concrete infrastructure, is dangerous at high concentrations and is foul smelling at low concentrations. Despite the importance of sulfide monitoring there is no commercially available system to quantify sulfide in waste water. In this article we report on our use of an in situ spectrometer to quantify bisulfide in waste water and additional analysis with a pH probe to calculate total dissolved sulfide. Our results show it is possible to use existing commercially available and field proven sensors to measure sulfide to mg/l levels continuously with little operator intervention and no sample preparation. PMID:18309215

  1. Process for producing cadmium sulfide on a cadmium telluride surface

    DOEpatents

    Levi, Dean H.; Nelson, Art J.; Ahrenkiel, Richard K.

    1996-01-01

    A process for producing a layer of cadmium sulfide on a cadmium telluride surface to be employed in a photovoltaic device. The process comprises providing a cadmium telluride surface which is exposed to a hydrogen sulfide plasma at an exposure flow rate, an exposure time and an exposure temperature sufficient to permit reaction between the hydrogen sulfide and cadmium telluride to thereby form a cadmium sulfide layer on the cadmium telluride surface and accomplish passivation. In addition to passivation, a heterojunction at the interface of the cadmium sulfide and the cadmium telluride can be formed when the layer of cadmium sulfide formed on the cadmium telluride is of sufficient thickness.

  2. Animal adaptations for tolerance and exploitation of poisonous sulfide.

    PubMed

    Grieshaber, M K; Völkel, S

    1998-01-01

    Many aquatic animal species can survive sulfide exposure to some extent through oxidation of the sulfide, which results mainly in thiosulfate. In several species, sulfide oxidation is localized in the mitochondria and is accompanied by ATP synthesis. In addition, blood-based and intracellular compounds can augment sulfide oxidation. The formation of thiosulfate requires oxygen, which results in an increase in oxygen consumption of some species. If not all sulfide is detoxified, cytochrome C oxidase is inhibited. Under these conditions, a sulfide-dependent anaerobic energy metabolism commences. PMID:9558453

  3. Hydrogen Sulfide Inhibits Amyloid Formation

    PubMed Central

    2015-01-01

    Amyloid fibrils are large aggregates of misfolded proteins, which are often associated with various neurodegenerative diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and vascular dementia. The amount of hydrogen sulfide (H2S) is known to be significantly reduced in the brain tissue of people diagnosed with Alzheimer’s disease relative to that of healthy individuals. These findings prompted us to investigate the effects of H2S on the formation of amyloids in vitro using a model fibrillogenic protein hen egg white lysozyme (HEWL). HEWL forms typical β-sheet rich fibrils during the course of 70 min at low pH and high temperatures. The addition of H2S completely inhibits the formation of β-sheet and amyloid fibrils, as revealed by deep UV resonance Raman (DUVRR) spectroscopy and ThT fluorescence. Nonresonance Raman spectroscopy shows that disulfide bonds undergo significant rearrangements in the presence of H2S. Raman bands corresponding to disulfide (RSSR) vibrational modes in the 550–500 cm–1 spectral range decrease in intensity and are accompanied by the appearance of a new 490 cm–1 band assigned to the trisulfide group (RSSSR) based on the comparison with model compounds. The formation of RSSSR was proven further using a reaction with TCEP reduction agent and LC-MS analysis of the products. Intrinsic tryptophan fluorescence study shows a strong denaturation of HEWL containing trisulfide bonds. The presented evidence indicates that H2S causes the formation of trisulfide bridges, which destabilizes HEWL structure, preventing protein fibrillation. As a result, small spherical aggregates of unordered protein form, which exhibit no cytotoxicity by contrast with HEWL fibrils. PMID:25545790

  4. Hydrogen Sulfide and Urogenital Tract.

    PubMed

    di Villa Bianca, Roberta d'Emmanuele; Cirino, Giuseppe; Sorrentino, Raffaella

    2015-01-01

    In this chapter the role played by H2S in the physiopathology of urogenital tract revising animal and human data available in the current relevant literature is discussed. H2S pathway has been demonstrated to be involved in the mechanism underlying penile erection in human and experimental animal. Both cystathionine-β synthase (CBS) and cystathionine-γ lyase (CSE) are expressed in the human corpus cavernosum and exogenous H2S relaxes isolated human corpus cavernosum strips in an endothelium-independent manner. Hydrogen sulfide pathway also accounts for the direct vasodilatory effect operated by testosterone on isolated vessels. Convincing evidence suggests that H2S can influence the cGMP pathway by inhibiting the phosphodiesterase 5 (PDE-5) activity. All these findings taken together suggest an important role for the H2S pathway in human corpus cavernosum homeostasis. However, H2S effect is not confined to human corpus cavernosum but also plays an important role in human bladder. Human bladder expresses mainly CBS and generates in vitro detectable amount of H2S. In addition the bladder relaxant effect of the PDE-5 inhibitor sildenafil involves H2S as mediator. In conclusion the H2S pathway is not only involved in penile erection but also plays a role in bladder homeostasis. In addition the finding that it involved in the mechanism of action of PDE-5 inhibitors strongly suggests that modulation of this pathway can represent a therapeutic target for the treatment of erectile dysfunction and bladder diseases. PMID:26162831

  5. Sulfide capacities of fayalite-base slags

    NASA Astrophysics Data System (ADS)

    Simeonov, S. R.; Sridhar, R.; Toguri, J. M.

    1995-04-01

    The sulfide capacities of fayalite-base slags were measured by a gas-slag equilibration technique under controlled oxygen and sulfur potentials similar to those encountered in the pyrometallurgical processing of nonferrous metals. The oxygen pressure range was from 10-9.5 to 10-11 MPa and the sulfur pressure range from 10-3 to 10-4.5 MPa, over a temperature range of 1473 to 1623 K. The slags studied were FeO-SiO2 at silica saturation and those with addition of CaO, MgO, and Al2O3 to determine their effect on sulfide capacities. For these slags, the sulfide capacities were found to vary from 10-3.3 to 10-5. The sulfide capacities increased with increasing temperature from 1473 to 1623 K. A comparison of the reported plant data on sulfur content of industrial slags shows good agreement with the present experimental results. The present data will be useful in estimating metal losses in slag due to metal sulfide entrainment in nonferrous smelters.

  6. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  7. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  8. Surface modifications of steels to improve corrosion resistance in sulfidizing-oxidizing environments

    NASA Astrophysics Data System (ADS)

    Behrani, Vikas

    Industrial and power generation processes employ units like boilers and gasifiers to burn sulfur containing fuels to produce steam and syn gas (H 2 and CO), which can generate electricity using turbines and fuel cells. These units often operate under environments containing gases such as H 2S, SO2, O2 etc, which can attack the metallic structure and impose serious problems of corrosion. Corrosion control in high temperature sulfur bearing environments is a challenging problem requiring information on local gaseous species at the surface of alloy and mechanisms of degradation in these environments. Coatings have proved to be a better alternative for improving corrosion resistance without compromising the bulk mechanical properties. Changes in process conditions may result in thermal and/or environment cycling between oxidizing and sulfidizing environments at the alloy surface, which can damage the protective scale formed on the alloy surface, leading to increase in corrosion rates. Objective of this study was to understand the effect of fluctuating environments on corrosion kinetics of carbon steels and develop diffusion based coatings to mitigate the high temperatures corrosion under these conditions. More specifically, the focus was: (1) to characterize the local gaseous environments at the surface of alloys in boilers; (2) optimizing diffusion coatings parameters for carbon steel; (3) understand the underlying failure mechanisms in cyclic environments; (4) to improve aluminide coating behavior by co-deposition of reactive elements such as Yttrium and Hafnium; (5) to formulate a plausible mechanism of coating growth and effects of alloying elements on corrosion; and (6) to understand the spallation behavior of scale by measuring stresses in the scales. The understanding of coating mechanism and effects of fluctuating gaseous environments provides information for designing materials with more reliable performance. The study also investigates the mechanism behind

  9. The Molecular Frame Electric Dipole Moment and Hyperfine Interactions in Hafnium Fluoride, HfF

    NASA Astrophysics Data System (ADS)

    Le, Anh; Steimle, Timothy C.; Skripnikov, Leonid; Titov, Anatoly V.

    2013-06-01

    The identification of HfF^{+} as a possible candidate for a d_{e}} measurement has stimulated new interest in the spectroscopy of both HfF^{+} and neutral HfF. Studies of the neutral are relevant because photoionization schemes can be used to produce the cations. More importantly, computational methodologies used to predict the electronic wavefunction of HfF^{+} can be effectively assessed by making a comparison of predicted and experimental properties of the neutral, which are more readily determinable. The (1,0)[17.9]2.5 -X^{2}Δ_{3/2} band of hafnium monofluoride (HfF) has been recorded using high-resolution laser-induced fluorescence spectroscopy both field-free and in the presence of a static electric field. The field-free spectra of ^{177}HfF, ^{179}HfF, and ^{180}HfF were model to generate a set of fine and hyperfine parameters for the X^{2}Δ_{3/2} (v=0) and [17.9]2.5 (v=1) states. The observed optical Stark shifts for the ^{180}HfF isotopologue were analyzed to produce the molecular frame electric dipole moments of 1.66(1)D and 0.419(7)D for the X^{2}Δ_{3/2} and [17.9]2.5 states, respectively. A two-step ab initio calculation consisting of a two-component generalized relativistic effective core potential calculation (GRECP) followed by a restoration of the proper four-component wavefunction was performed to predict the properties of ground state HfF. B. J. Barker, I. O. Antonov, V. E. Bondybey, and M. C. Heaven, J. Chem. Phys., 134, 201102 (2011). K. C. Cossel, D. N. Gresh, L. C. Sinclair, T. Coffey, L. V. Skripnikov, A. N. Petrov, N. S. Mosyagin, A. V. Titov, R. W. Field, E. R. Meyer, E. A. Cornell and J. Ye, Chem. Phys. Lett., 546, 1 (2012). M. Grau, A. E. Leanhardt, H. Loh, L. C. Sinclair, R. P. Stutz, T. S. Yahn, and E. A. Cornell, J. Mol. Spectroc., 272, 32 (2012). H. Loh, R. P. Stutz, T. S. Yahn, H. Looser, R. W. Field, and E. A. Cornell, J. Mol. Spectroc.,276-277, 49 (2012).

  10. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

    SciTech Connect

    Nguyen, Duc; Girolami, Gregory S.; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Lyding, Joseph; Gruebele, Martin

    2014-11-28

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB{sub 2} glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB{sub 2} has a very high bulk glass transition temperature T{sub g}, and we observe no three-state hopping or sequential two-state hopping previously seen on lower T{sub g} glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how “mixed” features can show up in surface dynamics of glasses.

  11. Hafnium isotopes in Jack Hills zircons and the formation of the Hadean crust

    NASA Astrophysics Data System (ADS)

    Blichert-Toft, Janne; Albarède, Francis

    2008-01-01

    New bulk Hf and Pb isotope data were obtained for 63 leached single zircons from Jack Hills (JH), Western Australia, using solution chemistry and, respectively, MC-ICP MS and ICP-MS. With the exception of one "young" zircon at 3.32 Ga, the remainder of the selected grains were previously dated at > 3.9 Ga by ion-microprobe. This work extends and complements the solution chemistry data of Harrison et al. [Harrison, T.M., Blichert-Toft, J., Müller, W., Albarède, F., Holden, P., Mojzsis, S.J., 2005. Heterogeneous Hadean hafnium: evidence of continental crust at 4.4 to 4.5 Ga. Science 310, 1947-1950.] but uses bulk rather than in situ Pb-Pb ages to interpret the Hf isotope data. This larger data set is used to explore whether the host rocks of the JH zircons formed as a succession of pulses or rather as a single event, and to calculate the age and assess the nature of their crustal protolith. We find that the parent granites of the JH zircons analyzed here formed during a single pulse 4.1 ± 0.1 Ga ago by the remelting of a 4.30-4.36 Ga old protolith. Monte Carlo modeling indicates that the 176Lu/ 177Hf ratios of this material (< 0.01) are unlike the ratios of modern-type oceanic crust and island arc rocks but rather fit a tonalite-trondhjemite-granodiorite (TTG) source. TTGs themselves derived their inordinately enriched character from a basaltic progenitor which corresponds to the missing enriched reservoir identified by the 143Nd- 144Nd, 142Nd- 144Nd, and 176Hf/ 177Hf systematics of Archean rocks. We speculate that crystallization of the magma ocean in the presence of garnet left the upper mantle and an early basaltic crust enriched in incompatible elements. Reaction of this early crust with the overlying hydrosphere and subsequent foundering into the mantle gave rise at ˜ 4.3 Ga to the TTG protolith of the JH granites. Dating the onset of plate tectonics therefore depends on whether TTGs can be considered as subduction zone magmas or not.

  12. Hafnium in peralkaline and peraluminous boro-aluminosilicate glass, and glass subcomponents: a solubility study.

    SciTech Connect

    Davis, Linda L.; Darab, John G.; Qian, Maoxu; Zhao, Donggao; Palenik, Christopher S.; Li, Hong; Strachan, Denis M.; Li, Liyu

    2003-10-15

    A relationship between the solubility of hafnia (HfO2) and the host glass composition was explored by determining the solubility limits of HfO2 in peralkaline and peraluminous borosilicate glasses in the system SiO2-Al2O3-B2O3-Na2O, and in glasses in the system SiO2-Na2O-Al2O3 in air at 1450 C. The only Hf-bearing phase to crystallize in the peralkaline borosilicate melts is hafnia, while in the boron-free melts sodium-hafnium silicates crystallize. All peraluminous borosilicate melts crystallize hafnia, but the slightly peraluminous glasses also have sector-zoned hafnia crystals that contain Al and Si. The more peraluminous borosilicate glasses also crystallize a B-containing mullite. The general morphology of the hafnia crystals changes as peralkalinity (Na2O/(Na2O+Al2O3)) decreases, as expected in melts with increasing viscosity. In all of the glasses with Na2O > Al2O3, the solubility of hafnia is linearly and positively correlated with Na2O/(Na2O + Al2O3) or Na2O - Al2O3 (excess sodium), despite the presence of 5 to 16 mol% B2O3. The solubility of hafnia is higher in the sodium-aluminum borosilicate glasses than in the sodium-aluminosilicate glasses, suggesting that the boron is enhancing the effect that excess sodium has on the incorporation of Hf into the glass structure. The results of this solubility study are compared to other studies of high-valence cation solubility in B-free silicate melts. From this, for peralkaline B-bearing glasses, it is shown that, although the solubility limits are higher, the solution behavior of hafnia is the same as in B-free silicate melts previously studied. By comparison, also, it is shown that in peraluminous melts, there must be a different solution mechanism for hafnia: different than for peralkaline sodium-aluminum borosilicate glasses and different than for B-free silicate melts studied by others.

  13. Deposition and characterization of titanium dioxide and hafnium dioxide thin films for high dielectric applications

    NASA Astrophysics Data System (ADS)

    Yoon, Meeyoung

    The industry's demand for higher integrated circuit density and performance has forced the gate dielectric layer thickness to decrease rapidly. The use of conventional SiO2 films as gate oxide is reaching its limit due to the rapid increase in tunneling current. Therefore, a need for a high dielectric material to produce large oxide capacitance and low leakage current has emerged. Metal-oxides such as titanium dioxide (TiO2) and hafnium dioxide (HfO2) are attractive candidates for gate dielectrics due to their electrical and physical properties suitable for high dielectric applications. MOCVD of TiO2 using titanium isopropoxide (TTIP) precursor on p-type Si(100) has been studied. Insertion of a TiO x buffer layer, formed by depositing metallic Ti followed by oxidation, at the TiO2/Si interface has reduced the carbon contamination in the TiO2 film. Elemental Ti films, analyzed by in-situ AES, were found to grow according to Stranski-Krastanov mode on Si(100). Carbon-free, stoichiometric TiO2 films were successfully produced on Si(100) without any parasitic SiO2 layers at the TiO 2/Si interface. Electron-beam deposition of HfO2 films on Si(100) has also been investigated in this work. HfO2 films are formed by depositing elemental Hf on Si(100) and then oxidizing it either in O2 or O 3. XPS results reveal that with oxidation Hf(4f) peak shifts +3.45eV with 02 and +3.65eV with O3 oxidation. LEED and AFM studies show that the initially ordered crystalline Hf becomes disordered after oxidation. The thermodynamic stability of HfO2 films on Si has been studied using a unique test-bed structure of Hf/O3/Si. Post-Oxidation of Layer Deposition (POLD) has been employed to produce HfO2 films with a desired thickness. XPS results indicate that stoichiometric HfO 2 films were successfully produced using the POLD process. The investigation of the growth and thin film properties of TiO 2 and HfO2 using oxygen and ozone has laid a foundation for the application of these metal

  14. Platinum and palladium incorporation into phosphate/viologen-phosphonates of zirconium and hafnium: synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Dokoutchaev, Alexandre; Krishnan, Venkatesan V.; Thompson, Mark E.; Balasubramanian, Mahalingam

    1998-10-01

    We have continued previous efforts to synthesize and characterize a microporous metal phosphate/viologen-phosphonate compound, [(ZrF) 2(PO 4)(O 3PCH 2CH 2-4,4'-bipyridinium-CH 2CH 2PO 3)] ṡF·2H 2O, ZrPO PV. A derivative of this material has been shown to be an efficient catalyst for the production of hydrogen peroxide from hydrogen and oxygen. This paper has two objectives—one is to optimize the synthetic routes leading to the preparation of MPO PV (M=zirconium or hafnium) and the second is to characterize MPO PV and the derivatives formed by Pt or Pd incorporation by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray absorption fine structure analysis (XAFS). Powder XRD data have shown much higher crystallinity in MPO PV samples prepared by hydrothermal methods than those prepared by reflux methods. In the hydrothermal synthesis, the amount of mineralizer (HF) present controlled the crystallite size (as determined from TEM micrographs). The larger the quantity of HF in the bomb, the larger the size of the crystals but the lower the yield of the MPO PV material. Crystal sizes of about 2.5 μm in length and 0.15 μm in diameter have been made with very large quantities of HF as mineralizer (10 times the required stoichiometric amount). Ion exchange of the material by PdCl 42- has resulted in the incorporation of the PdCl 42- ions in place of X - in the material. This has been confirmed by XAFS studies that demonstrate the oxidation state of Pd is 2+ and show four Cl atoms bound to Pd. Upon reduction it has been confirmed (by XAFS) that the palladium exists as metal with oxidation state of zero. Ion exchange by PdCl 42- and PtCl 42- and subsequent reduction of the material suspension by hydrogen result in the formation of separate Pt and Pd colloids in the close vicinity of the crystallites. TEM micrographs show clearly that the Pt metal

  15. Determination of microamounts of hafnium in zirconium using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry during their separation by ion exchange on Diphonix chelating resin.

    PubMed

    Smolik, Marek; Jakóbik-Kolon, Agata

    2009-04-01

    Inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICPMS) methods were applied to check the possibility of determination of hafnium in zirconium at a level lower than 100 ppm. A zirconium matrix of hafnium content lower than 10 ppm was obtained using a worked-out separation method exploiting ion exchange on Diphonix resin. Both methods give results in good agreement with each other as well as with those for certified reference material BCR-098 (Zircaloy-4). They were utilized in determination of Hf in the samples collected during separation of microamounts of hafnium from zirconium by the mentioned ion exchange. These results proved the earlier described method of separation on Diphonix resin to be effective even when the initial concentration of hafnium in zirconium decreases from 2.4% to 0.0082%.

  16. Labile sulfide and sulfite in phytochelatin complexes

    SciTech Connect

    Eannetta, N.T.; Steffens, J.C. )

    1989-04-01

    Heavy metals such as cadmium induce tomato cell cultures to synthesize the metal binding polypeptides ({gamma}-Glu-Cys){sub 3} and ({gamma}-Glu-Cys){sub 4}-Gly (phytochelatins). Tomato cells selected for growth on normally lethal concentrations of CdCl{sub 2} synthesize higher quantities of these polypeptides. Cd{sup r} cells are not cross-resistant to other heavy metals, and recent work suggests that metal detoxification by these peptides may be Cd-specific. The occurrence of labile sulfur as a component of the metal complex raises questions concerning possible functions of phytochelatins besides that of Cd binding. The presence of acid-labile sulfide ion in phytochelatin complexes has been reported by several groups. We report the additional finding that labile sulfite is also present in these complexes and in higher amounts than sulfide. Sulfide and sulfite are both released from the metal binding complex by acidification or by treatment with EDTA.

  17. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration method... ferricyanide titration method for the determination of sulfide in wastewaters discharged by plants operating...

  18. 40 CFR 425.03 - Sulfide analytical methods and applicability.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... § 425.03 Sulfide analytical methods and applicability. (a) The potassium ferricyanide titration method... ferricyanide titration method for the determination of sulfide in wastewaters discharged by plants operating...

  19. Preparation of silver-activated zinc sulfide thin films

    NASA Technical Reports Server (NTRS)

    Feldman, C.; Swindells, F. E.

    1968-01-01

    Silver improves luminescence and reduces contamination of zinc sulfide phosphors. The silver is added after the zinc sulfide phosphors are deposited in thin films by vapor evaporation, but before calcining, by immersion in a solution of silver salt.

  20. Mechanisms of hydrogen sulfide removal with steel making slag.

    PubMed

    Kim, Kyunghoi; Asaoka, Satoshi; Yamamoto, Tamiji; Hayakawa, Shinjiro; Takeda, Kazuhiko; Katayama, Misaki; Onoue, Takasumi

    2012-09-18

    In the present study, we experimentally investigated the removal of hydrogen sulfide using steel-making slag (SMS) and clarified the mechanism of hydrogen sulfide removal with the SMS. The results proved that SMS is able to remove hydrogen sulfide dissolved in water, and the maximum removal amount of hydrogen sulfide per unit weight of the SMS for 8 days was estimated to be 37.5 mg S/g. The removal processes of hydrogen sulfide were not only adsorption onto the SMS, but oxidation and precipitation as sulfur. The chemical forms of sulfide adsorbed onto the SMS were estimated to be sulfur and manganese sulfide in the ratio of 81% and 19%, respectively. It is demonstrated here that the SMS is a promising material to remediate organically enriched coastal sediments in terms of removal of hydrogen sulfide. Furthermore, using SMS is expected to contribute to development of a recycling-oriented society.

  1. Sulfide and methane production in sewer sediments.

    PubMed

    Liu, Yiwen; Ni, Bing-Jie; Ganigué, Ramon; Werner, Ursula; Sharma, Keshab R; Yuan, Zhiguo

    2015-03-01

    Recent studies have demonstrated significant sulfide and methane production by sewer biofilms, particularly in rising mains. Sewer sediments in gravity sewers are also biologically active; however, their contribution to biological transformations in sewers is poorly understood at present. In this study, sediments collected from a gravity sewer were cultivated in a laboratory reactor fed with real wastewater for more than one year to obtain intact sediments. Batch test results show significant sulfide production with an average rate of 9.20 ± 0.39 g S/m(2)·d from the sediments, which is significantly higher than the areal rate of sewer biofilms. In contrast, the average methane production rate is 1.56 ± 0.14 g CH4/m(2)·d at 20 °C, which is comparable to the areal rate of sewer biofilms. These results clearly show that the contributions of sewer sediments to sulfide and methane production cannot be ignored when evaluating sewer emissions. Microsensor and pore water measurements of sulfide, sulfate and methane in the sediments, microbial profiling along the depth of the sediments and mathematical modelling reveal that sulfide production takes place near the sediment surface due to the limited penetration of sulfate. In comparison, methane production occurs in a much deeper zone below the surface likely due to the better penetration of soluble organic carbon. Modelling results illustrate the dependency of sulfide and methane productions on the bulk sulfate and soluble organic carbon concentrations can be well described with half-order kinetics.

  2. Classification of polytype structures of zinc sulfide

    SciTech Connect

    Laptev, V.I.

    1994-12-31

    It is suggested that the existing classification of polytype structures of zinc sulfide be supplemented with an additional criterion: the characteristic of regular point systems (Wyckoff positions) including their type, number, and multiplicity. The consideration of the Wyckoff positions allowed the establishment of construction principles of known polytype series of different symmetries and the systematization (for the first time) of the polytypes with the same number of differently packed layers. the classification suggested for polytype structures of zinc sulfide is compact and provides a basis for creating search systems. The classification table obtained can also be used for numerous silicon carbide polytypes. 8 refs., 4 tabs.

  3. Modeling of Sulfide Microenvironments on Mars

    NASA Technical Reports Server (NTRS)

    Schwenzer, S. P.; Bridges, J. C.; McAdam, A.; Steer, E. D.; Conrad, P. G.; Kelley, S. P.; Wiens, R. C.; Mangold, N.; Grotzinger, J.; Eigenbrode, J. L.; Franz, H. B.; Sutter, B.

    2016-01-01

    Yellowknife Bay (YKB; sol 124-198) is the second site that the Mars Science Laboratory Rover Curiosity investigated in detail on its mission in Gale Crater. YKB represents lake bed sediments from an overall neutral pH, low salinity environment, with a mineralogical composition which includes Ca-sulfates, Fe oxide/hydroxides, Fe-sulfides, amorphous material, and trioctahedral phyllosilicates. We investigate whether sulfide alteration could be associated with ancient habitable microenvironments in the Gale mudstones. Some textural evidence for such alteration may be pre-sent in the nodules present in the mudstone.

  4. Acute inhalation toxicity of carbonyl sulfide

    SciTech Connect

    Benson, J.M.; Hahn, F.F.; Barr, E.B.

    1995-12-01

    Carbonyl sulfide (COS), a colorless gas, is a side product of industrial procedures sure as coal hydrogenation and gasification. It is structurally related to and is a metabolite of carbon disulfide. COS is metabolized in the body by carbonic anhydrase to hydrogen sulfide (H{sub 2}S), which is thought to be responsible for COS toxicity. No threshold limit value for COS has been established. Results of these studies indicate COS (with an LC{sub 50} of 590 ppm) is slightly less acutely toxic than H{sub 2}S (LC{sub 50} of 440 ppm).

  5. Aromatic sulfide/sulfone polymer production

    SciTech Connect

    Scoggins, L.E.; Hoover, K.C.; Shang, W.W.

    1991-05-14

    This patent describes a process for the production of aromatic sulfide/sulfone polymer. It comprises: contacting at least one lactam, at least one alkali metal hydrosulfide, water, and at least one base selected from the group consisting of alkali metal hydroxides and mixtures of alkali metal hydroxides with alkali metal carbonates under reaction conditions of time and temperature sufficient to produce a mixture containing a complex which comprises the at least one alkali metal hydrosulfide and contacting the mixture produced with a least one dihaloaromatic sulfone under polymerization conditions for a period of time sufficient to form an aromatic sulfide/sulfone polymer.

  6. Evolution of sulfide mineralization on Mars

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.; Fisher, Duncan S.

    1990-01-01

    It has been previously suggested, on the basis of compositional and petrographic similarities noted between komatites, SNC meteorites, and the silicate portion of the Martian regolith fines, that iron-sulfide ore deposites may exist on Mars. This paper examines the possible locations of Archean-type sulfide and related ore deposits on Mars, their evolution, and the emplacement mechanisms for the ore deposit. The clues to these questions are deduced by applying to Mars the temporal patterns of ore distribution on earth and the experimental observations on sulfur solubility in basaltic melts.

  7. Membrane for hydrogen recovery from streams containing hydrogen sulfide

    DOEpatents

    Agarwal, Pradeep K.

    2007-01-16

    A membrane for hydrogen recovery from streams containing hydrogen sulfide is provided. The membrane comprises a substrate, a hydrogen permeable first membrane layer deposited on the substrate, and a second membrane layer deposited on the first layer. The second layer contains sulfides of transition metals and positioned on the on a feed side of the hydrogen sulfide stream. The present invention also includes a method for the direct decomposition of hydrogen sulfide to hydrogen and sulfur.

  8. Method for inhibiting oxidation of metal sulfide-containing material

    DOEpatents

    Elsetinow, Alicia; Borda, Michael J.; Schoonen, Martin A.; Strongin, Daniel R.

    2006-12-26

    The present invention provides means for inhibiting the oxidation of a metal sulfide-containing material, such as ore mine waste rock or metal sulfide taiulings, by coating the metal sulfide-containing material with an oxidation-inhibiting two-tail lipid coating (12) thereon, thereby inhibiting oxidation of the metal sulfide-containing material in acid mine drainage conditions. The lipids may be selected from phospholipids, sphingolipids, glycolipids and combinations thereof.

  9. Formation and characterization of the oxygen-rich hafnium dioxygen complexes: OHf(eta2-O2)(eta2-O3), Hf(eta2-O2)3, and Hf(eta2-O2)4.

    PubMed

    Gong, Yu; Zhou, Mingfei

    2007-09-20

    Hafnium atom oxidation by dioxygen molecules has been investigated using matrix isolation infrared absorption spectroscopy. The ground-state hafnium atom inserts into dioxygen to form primarily the previously characterized HfO(2) molecule in solid argon. Annealing allows the dioxygen molecules to diffuse and react with HfO(2) to form OHf(eta(2)-O(2))(eta(2)-O(3)), which is characterized as a side-on bonded oxo-superoxo hafnium ozonide complex. Under visible light (532 nm) irradiation, the OHf(eta(2)-O(2))(eta(2)-O(3)) complex either photochemically rearranges to a more stable Hf(eta(2)-O(2))(3) isomer, a side-on bonded di-superoxo hafnium peroxide complex, or reacts with dioxygen to form an unprecedented homoleptic tetra-superoxo hafnium complex: Hf(eta(2)-O(2))(4). The Hf(eta(2)-O(2))(4) complex is determined to possess a D(2d) geometry with a tetrahedral arrangement of four side-on bonded O(2) ligands around the hafnium atom, which thus presents an 8-fold coordination. These oxygen-rich complexes are photoreversible; that is, formation of Hf(eta(2)-O(2))(3) and Hf(eta(2)-O(2))(4) is accompanied by demise of OHf(eta(2)-O(2))(eta(2)-O(3)) under visible (532 nm) light irradiation and vice versa with UV (266 nm) light irradiation.

  10. Application of principle component analysis-artificial neural network for simultaneous determination of zirconium and hafnium in real samples.

    PubMed

    Abbaspour, A; Baramakeh, L

    2006-05-15

    Determination of zirconium and hafnium were done by applying singular value decomposition and a feed forward Neural Network Algorithm with back propagation of error. The determination of trace amounts of mixtures of Zr(IV) and Hf(IV) in various matrices (river, tap and industrial wastewater) were investigated by PC-ANN using the complexes formed between Alizarin Red S, Zr and Hf. The results showed that measurement is possible in the ranges of 0.03-3.4 and 0.2-7.0 microg ml-1 for Zr(IV) and Hf(IV), respectively. The detection limits were 0.02 and 0.08 microg ml-1 for Zr(IV) and Hf(IV), respectively. The results also show very good agreement between true and predicted concentration values and have the ability to use in routine analysis.

  11. Effect of post-deposition annealing on the structural and electrical properties of RF sputtered hafnium oxide thin films

    NASA Astrophysics Data System (ADS)

    Das, K. C.; Ghosh, S. P.; Tripathy, N.; Bose, G.; Kar, J. P.

    2016-02-01

    Hafnium oxide films were deposited on silicon substrates by RF sputtering at room temperature. Post-deposition rapid thermal annealing of the sputtered HfO2 films was carried out in the temperature range of 400°C to 800°C in oxygen ambient. The structural properties ware studied by X-ray diffraction (XRD), where the enhancement in the crystallinity of HfO2 (1¯11) orientation was observed. The Capacitance —Voltage (C-V) and Current density —Voltage (J-V) characteristics of the annealed dielectric film were investigated employing Al/HfO2/Si Metal Oxide Semiconductor (MOS) capacitor structure. The flatband voltage (V fb ) and oxide charge density (Q ox ) were extracted from the high frequency (1 MHz) C-V curve. Leakage current was found to be minimum for the annealing temperature of 600°C.

  12. Tribo-electrochemical characterization of hafnium multilayer systems deposited on nitride/vanadium nitride AISI 4140 steel

    NASA Astrophysics Data System (ADS)

    Mora, M.; Vera, E.; Aperador, W.

    2016-02-01

    In this work is presented the synergistic behaviour among corrosion/wear (tribocorrosion) of the multilayer coatings hafnium nitride/vanadium nitride [HfN/VN]n. The multilayers were deposited on AISI 4140 steel using the technique of physical vapor deposition PVD magnetron sputtering, the tests were performed using a pin-on-disk tribometer, which has an adapted potentiostat galvanostat with three-electrode electrochemical cell. Tribocorrosive parameters such as: Friction coefficient between the coating and the counter body (100 Cr6 steel ball); Polarization resistance by means of electrochemical impedance spectroscopy technique and corrosion rate by polarization curves were determined. It was observed an increase in the polarization resistance, a decrease in the corrosion rate and a low coefficient of friction in comparison with the substrate, due to an increase on the number of bilayers.

  13. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; Stubbins, James F.

    2015-03-15

    This work reports comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y{sub 2}O{sub 3}, fluorite Y{sub 2}O{sub 3}–HfO{sub 2} solid solution and pyrochlore (or fluorite) Y{sub 2}(Ti,Hf){sub 2−x}O{sub 7−x}. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. The results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation. - Highlights: • The oxide nanoparticles in a hafnium-containing austenitic ODS were characterized. • The nanoparticles are Y–Hf–Ti–O enriched phases according to APT and STEM–EDS. • Two coherency and an axis-parallel orientation relationships were found by HR-TEM. • Particle size has a prominent effect on the orientation relationship (OR). • Formation mechanism of the oxide nanoparticles was discussed based on the ORs.

  14. Experimental and first-principles studies on the elastic properties of α-hafnium metal under pressure

    DOE PAGES

    Qi, Xintong; Wang, Xuebing; Chen, Ting; Li, Baosheng

    2016-03-30

    Compressional and shear wave velocities of the α phase of hafnium have been measured up to 10.4 GPa at room temperature using ultrasonic interferometry in a multi-anvil apparatus. A finite strain equation of state analysis yielded Ks0 = 110.4 (5) GPa, G0 = 54.7(5) GPa,Ks0' = 3.7 and G0' = 0.6 for the elastic bulk and shear moduli and their pressure derivatives at ambient conditions. Complementary to the experimental data, the single crystal elastic constants, elastic anisotropy and the unit cell axial ratio c/a of α-hafnium at high pressures were investigated by Density Functional Theory (DFT) based first principles calculations.more » A c/a value of 1.605 is predicted for α-Hf at 40 GPa, which is in excellent agreement with previous experimental results. The low-pressure derivative of the shear modulus observed in our experimental data up to 10 GPa was found to originate from the elastic constant C44 which exhibits negligible pressure dependence within the current experimental pressure range. At higher pressures (>10 GPa), C44 was predicted to soften and the shear wave velocity νS trended to decrease with pressure, which can be interpreted as a precursor to the α-ω transition similar to that observed in other group IV elements (titanium and zirconium). Here, the acoustic velocities, bulk and shear moduli, and the acoustic Debye temperature (θD = 240.1 K) determined from the current experiments were all compared well with those predicted by our theoretical DFT calculations.« less

  15. Formation of selenide, sulfide or mixed selenide-sulfide films on metal or metal coated substrates

    DOEpatents

    Eser, Erten; Fields, Shannon

    2012-05-01

    A process and composition for preventing cracking in composite structures comprising a metal coated substrate and a selenide, sulfide or mixed selenide sulfide film. Specifically, cracking is prevented in the coating of molybdenum coated substrates upon which a copper, indium-gallium diselenide (CIGS) film is deposited. Cracking is inhibited by adding a Se passivating amount of oxygen to the Mo and limiting the amount of Se deposited on the Mo coating.

  16. New Sulfide Derivatives of Vegetable Oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetable oils containing sulfide group were synthesized using a UV initiated thiol-ene reaction. The reaction involved addition of butyl thiol to the double bonds of the vegetable oil without the presence of a solvent. The effects of temperature, reaction time, type of vegetable oil, thiol to veg...

  17. 30 CFR 250.490 - Hydrogen sulfide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... black lettering as follows: Letter height Wording 12 inches Danger. Poisonous Gas. Hydrogen Sulfide. 7... well-control techniques to prevent formation fracturing in an open hole within the pressure limits of... designed consistent with the anticipated depth, conditions of the hole, and reservoir environment to...

  18. 30 CFR 250.490 - Hydrogen sulfide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... black lettering as follows: Letter height Wording 12 inches Danger. Poisonous Gas. Hydrogen Sulfide. 7... well-control techniques to prevent formation fracturing in an open hole within the pressure limits of... designed consistent with the anticipated depth, conditions of the hole, and reservoir environment to...

  19. Sulfide as a signaling molecule in autophagy

    PubMed Central

    Gotor, Cecilia; García, Irene; Crespo, José L.; Romero, Luis C.

    2013-01-01

    Hydrogen sulfide is already recognized as an important signaling molecule in mammalian systems, and emerging data suggest that H2S is a signaling molecule just as important as nitric oxide (NO) and H2O2 in plants. Although sulfide is generated in chloroplasts and mitochondria, it is present predominantly in the charged HS- form due to the basic pH inside both organelles, thus requiring an active transporter, which is yet to be identified, to be released. In Arabidopsis, we found that the cytosolic L-cysteine desulfhydrase DES1 is involved in the degradation of cysteine, and therefore responsible for the generation of H2S in this cellular compartment. DES1 deficiency leads to the induction of autophagy. Moreover, we have demonstrated that sulfide in particular exerts a general effect on autophagy through negative regulation, in a way unrelated to nutrient deficiency. The mechanisms of H2S action and its molecular targets are largely unknown, although in animal systems, protein S-sulfhydration has been proposed as a mechanism for sulfide-mediated signaling. PMID:23328265

  20. Comparison of Hydrogen Sulfide Analysis Techniques

    ERIC Educational Resources Information Center

    Bethea, Robert M.

    1973-01-01

    A summary and critique of common methods of hydrogen sulfide analysis is presented. Procedures described are: reflectance from silver plates and lead acetate-coated tiles, lead acetate and mercuric chloride paper tapes, sodium nitroprusside and methylene blue wet chemical methods, infrared spectrophotometry, and gas chromatography. (BL)

  1. REACTION PROCESSES OF ARSENIC IN SULFIDIC SOLUTIONS

    EPA Science Inventory

    The fate of arsenic in the environment is fundamentally linked to its speciation. Arsenic in aerobic environments is predominantly arsenate, however under reducing conditions arsenite species dominate. In anoxic or sulfidic environments thioarsenite ((As(OH)x(SH)yz-) species alon...

  2. Monitoring sulfide and sulfate-reducing bacteria

    SciTech Connect

    Tanner, R.S.

    1995-12-31

    Simple yet precise and accurate methods for monitoring sulfate-reducing bacteria (SRB) and sulfide remain useful for the study of bacterial souring and corrosion. Test kits are available to measure sulfide in field samples. A more precise methylene blue sulfide assay for both field and laboratory studies is described here. Improved media, compared to that in API RP-38, for enumeration of SRB have been formulated. One of these, API-RST, contained cysteine (1.1 mM) as a reducing agent, which may be a confounding source of sulfide. While cysteine was required for rapid enumeration of SRB from environmental samples, the concentration of cysteine in medium could be reduced to 0.4 mM. It was also determined that elevated levels of yeast extract (>1 g/liter) could interfere with enumeration of SRB from environmental samples. The API-RST medium was modified to a RST-11 medium. Other changes in medium composition, in addition to reduction of cysteine, included reduction of the concentration of phosphate from 3.4 mM to 2.2 mM, reduction of the concentration of ferrous iron from 0.8 mM to 0.5 mM and preparation of a stock mineral solution to ease medium preparation. SRB from environmental samples could be enumerated in a week in this medium.

  3. Platinum metals in magmatic sulfide ores

    USGS Publications Warehouse

    Naldrett, A.J.; Duke, J.M.

    1980-01-01

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. Copyright ?? 1980 AAAS.

  4. Atomic layer deposition of metal sulfide materials.

    PubMed

    Dasgupta, Neil P; Meng, Xiangbo; Elam, Jeffrey W; Martinson, Alex B F

    2015-02-17

    CONSPECTUS: The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivating interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry. ALD of sulfide materials typically uses metalorganic precursors and hydrogen sulfide (H2S). As in oxide ALD, the precursor chemistry is critical to controlling both the film growth and properties including roughness, crystallinity, and impurity levels. By modification of the precursor sequence, multicomponent sulfides have been deposited, although challenges remain because of the higher propensity for cation exchange reactions, greater diffusion rates, and unintentional annealing of this more labile class of materials. A deeper understanding of these surface chemical reactions has been achieved through a combination of in situ studies and quantum-chemical calculations. As this understanding matures, so does our ability to deterministically tailor film properties to new applications and more sophisticated devices. This Account highlights the attributes of ALD chemistry that are unique to metal sulfides and surveys recent applications of these materials in photovoltaics, energy storage, and photonics. Within each application

  5. Oxygen Demand of Fresh and Stored Sulfide Solutions and Sulfide-Rich Constructed Wetland Effluent.

    PubMed

    Chan, Carolyn; Farahbakhsh, Khosrow

    2015-08-01

    This study investigated the contribution of hydrogen sulfide to biological oxygen demand (BOD5) and chemical oxygen demand (COD) in wastewater effluents, and documented the effect of storage times and conditions on the BOD5 and COD of pH-adjusted sodium sulfide solutions as well as graywater wetland effluent. Initial COD measurements of sulfide solutions were 84-89% of the theoretical oxygen demand (ThOD), 1.996 mg O2/mg S, whereas unseeded BOD5 measurements were 55-77%. For sulfide solutions, all storage conditions led to declines of >15% (COD, BOD5), and >31% (sulfide). For wetland effluent, storage without headspace was effective in reducing COD losses (3.7%), compared to storage with headspace (17%), and affected changes in turbidity, UVA-254 and pH. The results suggest that storage times and conditions should be controlled and reported when reporting BOD5 and COD of sulfide-rich samples. Wetland models representing sulfate reduction as a method of COD removal may need to be reconsidered. PMID:26237688

  6. Sulfide-oxidizing bacteria: Their role during air-stripping

    SciTech Connect

    Dell`Orco, M.J.; Chadik, P.A.; Bitton, G.; Neumann, R.P.

    1998-10-01

    Air-stripping, used to remove hydrogen sulfide naturally present in many groundwater supplies, commonly causes sulfide-oxidizing bacteria to proliferate. The role of sulfide-oxidizing bacteria during air-stripping was investigated in a diffused-air pilot reactor modeled after an existing treatment facility. Visible bacterial filaments and biofilm developed within a few days and increased both the sulfide removed from and turbidity in the effluent. Total sulfide, dissolved oxygen, pH, and electrode potential were monitored at eight locations in the reactor to characterize the process.

  7. Analog Experiments on Sulfide Foams in Magmatic Ore Deposits

    NASA Astrophysics Data System (ADS)

    Leitch, A. M.; Dahn, D.; Zavala, K.

    2009-05-01

    Metal sulfides form as an immiscible phase from silicate magmas. Dynamic mingling and unmingling of the two phases is important for the development of economic deposits: mingling promotes enrichment of the sulfide in valuable metals, and subsequent unmingling generates massive sulfide. Analog experiments were carried out to investigate mingling processes in immiscible systems, using oil, water and small beads to represent magma, sulfide liquid and silicate crystals. Stirring or injection led to the formation of a foam of analog sulfide droplets within an analog silicate framework. We propose that the partial collapse of such a foam explains massive sulfide lenses at the Voisey's Bay magmatic sulfide deposit, and that crystallization of silicate crystals in the remaining foam walls generates 'net-textured' ores. In the experiments, solid particles had a profound effect on unmingling: analog sulfide droplets were stably contained within analog crystal-rich magma and did not coalesce. We therefore suggest that 'net' and 'leopard' textures in disseminated sulfides indicate mingling of sulfide with crystal-poor magma, whereas isolated disseminated patches of sulfide indicate mingling with a crystal-rich magma.

  8. Salen complexes of zirconium and hafnium: synthesis, structural characterization, controlled hydrolysis, and solvent-free ring-opening polymerization of cyclic esters and lactides.

    PubMed

    Saha, Tanmoy Kumar; Ramkumar, Venkatachalam; Chakraborty, Debashis

    2011-04-01

    Dinuclear salen compounds of zirconium and hafnium are efficient initiators for the solvent-free ring-opening polymerization of cyclic ester monomers and lactides. There is a correlation between the theoretical and experimental number-average molecular weights (M(n)'s) in these polymerizations. Polymerization of β-butyrolactone gives poly(3-hydroxybutyrate) with a good M(n) and molecular weight distribution.

  9. Competition for Dimethyl Sulfide and Hydrogen Sulfide by Methylophaga sulfidovorans and Thiobacillus thioparus T5 in Continuous Cultures

    PubMed Central

    De Zwart, J.; Sluis, J.; Kuenen, J. G.

    1997-01-01

    Pure and mixed cultures of Methylophaga sulfidovorans and Thiobacillus thioparus T5 were grown in continuous cultures on either dimethyl sulfide, dimethyl sulfide and H(inf2)S, or H(inf2)S and methanol. In pure cultures, M. sulfidovorans showed a lower affinity for sulfide than T. thioparus T5. Mixed cultures, grown on dimethyl sulfide, showed coexistence of both species. M. sulfidovorans fully converted dimethyl sulfide to thiosulfate, which was subsequently further oxidized to sulfate by T. thioparus T5. Mixed cultures supplied with sulfide and methanol showed that nearly all the sulfide was used by T. thioparus T5, as expected on the basis of the affinities for sulfide. The sulfide in mixed cultures supplied with dimethyl sulfide and H(inf2)S, however, was used by both bacteria. This result may be explained by the fact that the H(inf2)S-oxidizing capacity of M. sulfidovorans remains fully induced by intracellular H(inf2)S originating from dimethyl sulfide metabolism. PMID:16535680

  10. Selective chemical dissolution of sulfides: An evaluation of six methods applicable to assaying sulfide-bound nickel

    USGS Publications Warehouse

    Klock, P.R.; Czamanske, G.K.; Foose, M.; Pesek, J.

    1986-01-01

    Six analytical techniques for the selective chemical dissolution of sulfides are compared with the purpose of defining the best method for accurately determining the concentration of sulfide-bound nickel. Synthesized sulfide phases of known elemental content, mixed with well-analyzed silicates, were used to determine the relative and absolute efficiency, based on Ni and Mg recovery, of the techniques. Tested leach-methods purported to dissolve sulfide from silicate phases include: brominated water, brominated water-carbon tetrachloride, nitric-hydrochloric acid, hydrogen peroxide-ammonium citrate, bromine-methanol and hydrogen peroxide-ascorbic acid. Only the hydrogen peroxide-ammonium citrate method did not prove adequate in dissolving the sulfide phases. The remaining five methods dissolved the sulfide phases, but the indicated amount of attack on the silicate portion ranged from 3% to 100%. The bromine-methanol method is recommended for assaying sulfide-Ni deposits when Ni is also present in silicate phases. ?? 1986.

  11. Arsenic speciation in natural sulfidic geothermal waters

    NASA Astrophysics Data System (ADS)

    Keller, Nicole S.; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    The speciation of arsenic in natural sulfidic geothermal waters was studied using chemical analyses and thermodynamic aqueous speciation calculations. Samples were collected in three geothermal systems in Iceland, having contrasting H2S concentrations in the reservoir (high vs. low). The sampled waters contained 7-116 ppb As and <0.01-77.6 ppm H2S with pH of 8.56-9.60. The analytical setup used for the determination of arsenic species (Ion Chromatography-Hydride Generation Atomic Fluorescence Spectrometry, IC-HG-AFS) was field-deployed and the samples analyzed within ∼5 min of sampling in order to prevent changes upon storage, which were shown to be considerable regardless of the sample storage method used. Nine aqueous arsenic species were detected, among others arsenite (HnAsO3n-3), thioarsenite (HnAsS3n-3), arsenate (HnAsO4n-3), monothioarsenate (HnAsSO3n-3), dithioarsenate (HnAsS2O2n-3), trithioarsenate (HnAsS3O) and tetrathioarsenate (HnAsS4n-3). The results of the measured aqueous arsenic speciation in the natural geothermal waters and comparison with thermodynamic calculations reveal that the predominant factors determining the species distribution are sulfide concentration and pH. In alkaline waters with low sulfide concentrations the predominant species are AsIII oxyanions. This can be seen in samples from a liquid-only well, tapping water that is H2S-poor and free of oxygen. At intermediate sulfide concentration AsIII and AsV thio species become important and predominate at high sulfide concentration, as seen in two-phase well waters, which have high H2S concentrations in the reservoir. Upon oxidation, for instance due to mixing of the reservoir fluid with oxygenated water upon ascent to the surface, AsV oxyanions form, as well as AsV thio complexes if the sulfide concentration is intermediate to high. This oxidation process can be seen in samples from hot springs in the Geysir geothermal area. While the thermodynamic modeling allows for a first

  12. Sulfide Intrusion and Detoxification in the Seagrass Zostera marina

    PubMed Central

    Hasler-Sheetal, Harald; Holmer, Marianne

    2015-01-01

    Gaseous sulfide intrusion into seagrasses growing in sulfidic sediments causes little or no harm to the plant, indicating the presence of an unknown sulfide tolerance or detoxification mechanism. We assessed such mechanism in the seagrass Zostera marina in the laboratory and in the field with scanning electron microscopy coupled to energy dispersive X-ray spectroscopy, chromatographic and spectrophotometric methods, and stable isotope tracing coupled with a mass balance of sulfur compounds. We found that Z. marina detoxified gaseous sediment-derived sulfide through incorporation and that most of the detoxification occurred in underground tissues, where sulfide intrusion was greatest. Elemental sulfur was a major detoxification compound, precipitating on the inner wall of the aerenchyma of underground tissues. Sulfide was metabolized into thiols and entered the plant sulfur metabolism as well as being stored as sulfate throughout the plant. We conclude that avoidance of sulfide exposure by reoxidation of sulfide in the rhizosphere or aerenchyma and tolerance of sulfide intrusion by incorporation of sulfur in the plant are likely major survival strategies of seagrasses in sulfidic sediments. PMID:26030258

  13. The Evolution of Sulfide Tolerance in the Cyanobacteria

    NASA Technical Reports Server (NTRS)

    Miller, Scott R.; Bebout, Brad M.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Understanding how the function of extant microorganisms has recorded both their evolutionary histories and their past interactions with the environment is a stated goal of astrobiology. We are taking a multidisciplinary approach to investigate the diversification of sulfide tolerance mechanisms in the cyanobacteria, which vary both in their degree of exposure to sulfide and in their capacity to tolerate this inhibitor of photosynthetic electron transport. Since conditions were very reducing during the first part of Earth's history and detrital sulfides have been found in Archean sediments, mechanisms conferring sulfide tolerance may have been important for the evolutionary success of the ancestors of extant cyanobacteria. Two tolerance mechanisms have been identified in this group: (1) resistance of photosystem II, the principal target of sulfide toxicity; and (2) maintenance of the ability to fix carbon despite photosystem II inhibition by utilizing sulfide as an electron donor in photosystem I - dependent, anoxygenic photosynthesis. We are presently collecting comparative data on aspects of sulfide physiology for laboratory clones isolated from a variety of habitats. These data will be analyzed within a phylogenetic framework inferred from molecular sequence data collected for these clones to test how frequently different mechanisms of tolerance have evolved and which tolerance mechanism evolved first. In addition, by analyzing these physiological data together with environmental sulfide data collected from our research sites using microelectrodes, we can also test whether the breadth of an organism's sulfide tolerance can be predicted from the magnitude of variation in environmental sulfide concentration it has experienced in its recent evolutionary past and whether greater average sulfide concentration and/or temporal variability in sulfide favors the evolution of a particular mechanism of sulfide tolerance.

  14. Enhanced reductive dechlorination of trichloroethylene by sulfidated nanoscale zerovalent iron.

    PubMed

    Rajajayavel, Sai Rajasekar C; Ghoshal, Subhasis

    2015-07-01

    Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of aquifers contaminated by chlorinated organic pollutants. In this study we show that the extent of sulfidation of NZVI enhances the rate of dechlorination of trichloroethylene (TCE) compared to that by unamended NZVI, and the enhancement depends on the Fe/S molar ratio. Experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62-66) showed that the surface-area normalized first-order TCE degradation rate constant increased up to 40 folds compared to non-sulfidated NZVI. Fe/S ratios in the range of 12-25 provided the highest TCE dechlorination rates, and rates decreased at both higher and lower Fe/S. In contrast, sulfidated NZVI exposed to water in the absence of TCE showed significantly lower hydrogen evolution rate (2.75 μmol L(-1) h(-1)) compared to that by an unamended NZVI (6.92 μmol L(-1) h(-1)), indicating that sulfidation of NZVI suppressed corrosion reactions with water. Sulfide (HS(-)) ions reacted rapidly with NZVI and X-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS2. We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding of TCE on the reactive sites of the iron sulfide outer layer. Resuspending sulfidated NZVI in sulfide-free or sulfide containing solutions altered the TCE degradation rate constants because of changes in the FeS layer thickness. Sulfidated NZVI maintained its high reactivity in the presence of multiple mono and divalent ions and with polyelectrolyte coatings. Thus, sulfide ions in groundwater can significantly alter NZVI reactivity.

  15. Cadmium zinc sulfide by solution growth

    DOEpatents

    Chen, Wen S.

    1992-05-12

    A process for depositing thin layers of a II-VI compound cadmium zinc sulfide (CdZnS) by an aqueous solution growth technique with quality suitable for high efficiency photovoltaic or other devices which can benefit from the band edge shift resulting from the inclusion of Zn in the sulfide. A first solution comprising CdCl.sub.2 2.5H.sub.2 O, NH.sub.4 Cl, NH.sub.4 OH and ZnCl.sub.2, and a second solution comprising thiourea ((NH.sub.2).sub.2 CS) are combined and placed in a deposition cell, along with a substrate to form a thin i.e. 10 nm film of CdZnS on the substrate. This process can be sequentially repeated with to achieve deposition of independent multiple layers having different Zn concentrations.

  16. Iron-sulfide redox flow batteries

    SciTech Connect

    Xia, Guan-Guang; Yang, Zhenguo; Li, Liyu; Kim, Soowhan; Liu, Jun; Graff, Gordon L

    2013-12-17

    Iron-sulfide redox flow battery (RFB) systems can be advantageous for energy storage, particularly when the electrolytes have pH values greater than 6. Such systems can exhibit excellent energy conversion efficiency and stability and can utilize low-cost materials that are relatively safer and more environmentally friendly. One example of an iron-sulfide RFB is characterized by a positive electrolyte that comprises Fe(III) and/or Fe(II) in a positive electrolyte supporting solution, a negative electrolyte that comprises S.sup.2- and/or S in a negative electrolyte supporting solution, and a membrane, or a separator, that separates the positive electrolyte and electrode from the negative electrolyte and electrode.

  17. Iron-sulfide redox flow batteries

    DOEpatents

    Xia, Guanguang; Yang, Zhenguo; Li, Liyu; Kim, Soowhan; Liu, Jun; Graff, Gordon L

    2016-06-14

    Iron-sulfide redox flow battery (RFB) systems can be advantageous for energy storage, particularly when the electrolytes have pH values greater than 6. Such systems can exhibit excellent energy conversion efficiency and stability and can utilize low-cost materials that are relatively safer and more environmentally friendly. One example of an iron-sulfide RFB is characterized by a positive electrolyte that comprises Fe(III) and/or Fe(II) in a positive electrolyte supporting solution, a negative electrolyte that comprises S.sup.2- and/or S in a negative electrolyte supporting solution, and a membrane, or a separator, that separates the positive electrolyte and electrode from the negative electrolyte and electrode.

  18. Subsurface heaters with low sulfidation rates

    SciTech Connect

    John, Randy Carl; Vinegar, Harold J

    2013-12-10

    A system for heating a hydrocarbon containing formation includes a heater having an elongated ferromagnetic metal heater section. The heater is located in an opening in a formation. The heater section is configured to heat the hydrocarbon containing formation. The exposed ferromagnetic metal has a sulfidation rate that goes down with increasing temperature of the heater, when the heater is in a selected temperature range.

  19. Hydrogen sulfide prodrugs—a review

    PubMed Central

    Zheng, Yueqin; Ji, Xingyue; Ji, Kaili; Wang, Binghe

    2015-01-01

    Hydrogen sulfide (H2S) is recognized as one of three gasotransmitters together with nitric oxide (NO) and carbon monoxide (CO). As a signaling molecule, H2S plays an important role in physiology and shows great potential in pharmaceutical applications. Along this line, there is a need for the development of H2S prodrugs for various reasons. In this review, we summarize different H2S prodrugs, their chemical properties, and some of their potential therapeutic applications. PMID:26579468

  20. Single-layer transition metal sulfide catalysts

    SciTech Connect

    Thoma, Steven G.

    2011-05-31

    Transition Metal Sulfides (TMS), such as molybdenum disulfide (MoS.sub.2), are the petroleum industry's "workhorse" catalysts for upgrading heavy petroleum feedstocks and removing sulfur, nitrogen and other pollutants from fuels. We have developed an improved synthesis technique to produce SLTMS catalysts, such as molybdenum disulfide, with potentially greater activity and specificity than those currently available. Applications for this technology include heavy feed upgrading, in-situ catalysis, bio-fuel conversion and coal liquefaction.

  1. Redetermination of piperidinium hydrogen sulfide structure

    NASA Technical Reports Server (NTRS)

    Andras, Maria T.; Hepp, Aloysius F.; Fanwick, Phillip E.; Duraj, Stan A.; Gordon, Edward M.

    1994-01-01

    The presence of adventitious water in a reaction between dicyclopentamethylene thiuram-disulfide (C5H10NCS2)(sub 2) and a picoline solution of tricyclopentadienyl indium(III) (C5H5)(sub 3). It resulted in the formation of piperidinium hydrogen sulfide (C5H13NS). The piperidinium hydrogen sulfide produced in this way was unambiguously characterized by X-ray crystallography. The structure determination showed that the piperidinium hydrogen sulfide crystal (MW = 119.23 g/mol) has an orthorhombic (Pbcm) unit cell whose parameters are: a = 9.818(2), b = 7.3720(1), c = 9.754(1) A, V = 706.0(3) A(exp 3), Z=4. D(sub chi) = 1.122 g cm(exp -3), Mo K(alpha) (lamda = 0.71073), mu= 3.36 cm(exp -1), F(000) = 264.0, T =293 K, R = 0.036 for 343 reflections with F(sub O)(sup 2) greater than 3 sigma (F(sub O)(sup 2)) and 65 variables. The compound consists of (C5H10NH2)(+) cations and (SH)(-) anions with both species residing on crystallographic mirror planes. N-H -- S hydrogen bonding contributes to the interconnection of neighboring piperidinium components of the compound.

  2. Using hafnium isotopic compositions in zircons to understand magmatic processes in the Okataina Volcanic Center, New Zealand

    NASA Astrophysics Data System (ADS)

    Rubin, A. E.; Cooper, K. M.; Wimpenny, J.; Yin, Q.

    2012-12-01

    The Taupo Volcanic Zone (TVZ) in New Zealand comprises the Okataina Volcanic Center (OVC) and Taupo Volcanic Center (TVC). The TVZ is one of the most active volcanic zones in the world, having erupted over 50 times in the past 60 ka. Rhyolites erupted from the OVC vary in chemical composition over relatively small distances and within single eruptions, suggesting that multiple internally homogeneous melts are stored separately, albeit in close physical proximity to each other. Eruptive products record the mingling of chemically distinct melts; however, the timescales on which these melts are amalgamated prior to (or during) eruptions is not well understood. This study presents the results of new hafnium isotopic data obtained from zircons of the 0.7 ka Kaharoa eruption, the most recent rhyolitic eruption from the OVC. ɛHf data were acquired from spots previously analyzed for trace element and U-Th age data (Klemetti et al., 2011, EPSL v 305) in order to chemically fingerprint distinct melts that existed prior to amalgamation and eruption. Zircons were analyzed from two samples of the Kaharoa eruption, each representing a chemical compositional end member of the eruptive products (Types 1 (T1) and 2 (T2)). Though erupted simultaneously, these zircons encompass a wide range of ages (~10 ka to secular equilibrium), and preliminary ɛHf values for these zircons range from -1 to +24. Zircons from T1 rhyolites display ɛHf values of +6 to +20, while T2 zircons span a somewhat wider range between -1 and +24. Zircon zones with high Y and low Hf that crystallized between 20-40 ka, previously interpreted to reflect the presence of a hot-dry-reducing magma beneath this part of the magmatic system, also have high ɛHf, suggesting that these magmas have a distinctive origin. The anomalously high ɛHf values of the Kaharoa zircons have implications for better understanding the sources of the rhyolitic melts as well as their interactions within the OVC magmatic system. One

  3. Hydrocracking of n-decane over zeolite-supported metal sulfide catalysts. 2: Zeolite Y-supported Ni and Ni-Mo sulfides

    SciTech Connect

    Welters, W.J.J.; Waerden, O.H. van der; Beer, V.H.J. de; Santen, R.A. van

    1995-04-01

    For zeolite Y-supported nickel sulfide catalysts the influence of the metal sulfide dispersion on the hydrocracking properties for n-decane is examined. In order to obtain different nickel sulfide distributions (inside or outside the zeolite structure) and dispersions, the preparation method (impregnation of CaY or ion exchange of NaY), sulfidation procedure (direct sulfidation or sulfidation after drying), and metal loading are varied. A higher nickel sulfide surface (as measured by dynamic oxygen chemisorption) results in a strong increase of the n-decane conversion, but this is not accompanied by an improvement of the catalytic properties toward ideal hydrocracking. Additionally, some zeolite Y-supported Ni-Mo sulfide catalysts (varying in preparation method and sulfidation procedure) are tested for the hydroconversion of it-decane. However, no promoter effect could be observed. The activity of the bimetallic sulfide catalysts is always almost equal to that of the most active monometallic sulfide constituent.

  4. Microaeration for hydrogen sulfide removal in UASB reactor.

    PubMed

    Krayzelova, Lucie; Bartacek, Jan; Kolesarova, Nina; Jenicek, Pavel

    2014-11-01

    The removal of hydrogen sulfide from biogas by microaeration was studied in Up-flow Anaerobic Sludge Blanket (UASB) reactors treating synthetic brewery wastewater. A fully anaerobic UASB reactor served as a control while air was dosed into a microaerobic UASB reactor (UMSB). After a year of operation, sulfur balance was described in both reactors. In UASB, sulfur was mainly presented in the effluent as sulfide (49%) and in biogas as hydrogen sulfide (34%). In UMSB, 74% of sulfur was detected in the effluent (41% being sulfide and 33% being elemental sulfur), 10% accumulated in headspace as elemental sulfur and 9% escaped in biogas as hydrogen sulfide. The efficiency of hydrogen sulfide removal in UMSB was on average 73%. Microaeration did not cause any decrease in COD removal or methanogenic activity in UMSB and the elemental sulfur produced by microaeration did not accumulate in granular sludge. PMID:25270045

  5. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, B.S.; Gupta, R.P.

    1999-06-22

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream. 1 fig.

  6. Sensitive sulfide sensor with a trypsin-stabilized gold nanocluster.

    PubMed

    Fan, Jun; Li, Ruiping; Xu, Pingping; Di, Junwei; Tu, Yifeng; Yan, Jilin

    2014-01-01

    In this work, we synthesized a trypsin-stabilized fluorescent gold nanocluster. It was found that sulfide interacted with the nanocluster, which could result in significant fluorescence quenching. With this quenching effect, a fluorescence sulfide sensor was developed. This sensor responded linearly to sulfide in the range of 50 nM to 8 μM, and was capable of detecting sulfide as low as 5.5 nM. This provided a facile and sensitive scheme for sulfide analysis; the mechanism of the sensor was also provided. The sensor was then tested for real sample analysis, and good recoveries were obtained. Furthermore, persulfate was found to be effective to remove the quenching of sulfide, and this interaction was adopted for an indirect analysis of persulfate.

  7. Process for producing cadmium sulfide on a cadmium telluride surface

    DOEpatents

    Levi, D.H.; Nelson, A.J.; Ahrenkiel, R.K.

    1996-07-30

    A process is described for producing a layer of cadmium sulfide on a cadmium telluride surface to be employed in a photovoltaic device. The process comprises providing a cadmium telluride surface which is exposed to a hydrogen sulfide plasma at an exposure flow rate, an exposure time and an exposure temperature sufficient to permit reaction between the hydrogen sulfide and cadmium telluride to thereby form a cadmium sulfide layer on the cadmium telluride surface and accomplish passivation. In addition to passivation, a heterojunction at the interface of the cadmium sulfide and the cadmium telluride can be formed when the layer of cadmium sulfide formed on the cadmium telluride is of sufficient thickness. 12 figs.

  8. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, Brian S.; Gupta, Raghubir P.

    1999-01-01

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

  9. Metal sulfide initiators for metal oxide sorbent regeneration

    DOEpatents

    Turk, Brian S.; Gupta, Raghubir P.

    2001-01-01

    A process of regenerating a sulfided sorbent is provided. According to the process of the invention, a substantial portion of the energy necessary to initiate the regeneration reaction is provided by the combustion of a particulate metal sulfide additive. In using the particulate metal sulfide additive, the oxygen-containing gas used to regenerate the sulfided sorbent can be fed to the regeneration zone without heating or at a lower temperature than used in conventional processes wherein the regeneration reaction is initiated only by heating the oxygen-containing gas. The particulate metal sulfide additive is preferably an inexpensive mineral ore such as iron pyrite which does not adversely affect the regeneration or corresponding desulfurization reactions. The invention further includes a sorbent composition comprising the particulate metal sulfide additive in admixture with an active metal oxide sorbent capable of removing one or more sulfur compounds from a sulfur-containing gas stream.

  10. Limitation of Sulfide Capacity Concept for Molten Slags

    NASA Astrophysics Data System (ADS)

    Jung, In-Ho; Moosavi-Khoonsari, Elmira

    2016-04-01

    The sulfide capacity concept has been widely used in pyrometallurgy to define sulfur removal capacities of slags. Typically, the sulfide capacity is considered to be a unique slag property depending only on temperature regardless of partial pressures of oxygen and sulfur. In the present study, it is demonstrated that sulfide capacities of slags in particular those of Na2O-containing slags can vary with partial pressures of oxygen and sulfur due to large solubility of sulfide in Na2O-containing slag systems.

  11. Influence of iron on sulfide inhibition in dark biohydrogen fermentation.

    PubMed

    Dhar, Bipro Ranjan; Elbeshbishy, Elsayed; Nakhla, George

    2012-12-01

    Sulfide impact on biohydrogen production using dark fermentation of glucose at 37 °C was investigated. Dissolved sulfide (S(2-)) at a low concentration (25mg/L) increased biohydrogen production by 54% relative to the control (without iron addition). Whereas on initial dissolved S(2-) concentration of 500 mg/L significantly inhibited the biohydrogen production with total cumulative biohydrogen decreasing by 90% compared to the control (without iron addition). At sulfide concentrations of 500 mg S(2-)/L, addition of Fe(2+) at 3-4 times the theoretical requirement to precipitate 100% of the dissolved S(2-) entirely eliminated the inhibitory effect of sulfide.

  12. Contrasting origins of the upper mantle revealed by hafnium and lead isotopes from the Southeast Indian Ridge.

    PubMed

    Hanan, Barry B; Blichert-Toft, Janne; Pyle, Douglas G; Christie, David M

    2004-11-01

    The origin of the isotopic signature of Indian mid-ocean ridge basalts has remained enigmatic, because the geochemical composition of these basalts is consistent either with pollution from recycled, ancient altered oceanic crust and sediments, or with ancient continental crust or lithosphere. The radiogenic isotopic signature may therefore be the result of contamination of the upper mantle by plumes containing recycled altered ancient oceanic crust and sediments, detachment and dispersal of continental material into the shallow mantle during rifting and breakup of Gondwana, or contamination of the upper mantle by ancient subduction processes. The identification of a process operating on a scale large enough to affect major portions of the Indian mid-ocean ridge basalt source region has been a long-standing problem. Here we present hafnium and lead isotope data from across the Indian-Pacific mantle boundary at the Australian-Antarctic discordance region of the Southeast Indian Ridge, which demonstrate that the Pacific and Indian upper mantle basalt source domains were each affected by different mechanisms. We infer that the Indian upper-mantle isotope signature in this region is affected mainly by lower continental crust entrained during Gondwana rifting, whereas the isotope signature of the Pacific upper mantle is influenced predominantly by ocean floor subduction-related processes.

  13. Spectrophotometric determination of zirconium(IV) and hafnium(IV) with 1-(2'thiazolylazo)-2-naphthol

    SciTech Connect

    Eshwar, M.C.; Sharma, C.D.

    1987-11-10

    1-(2'-thiazolylazo)-2-naphthol (TAN) reacts with zirconium(IV) and hafnium(IV) in acid media to form sparingly soluble 1:4 red-colored chelates, which are dissolved in 40 and 32% methanol (v/v) respectively. The complex of Hf(IV) is stable only in the presence of sodium dodecylsulfate (0.1%, w/v), which also increases the sensitivity of the system. The Zr(IV)-TAN and Hf(IV)-TAN and Hf(IV)-TAN complexes exhibit maximum absorbance at 600 and 580 nm, obey Beer's law in the concentration ranges 0.04-2.88 and 0.8-2.60 ..mu..g/ml of Zr(IV) and Hf(IV), have molar absorptivities of 5.25 x 10/sup 4/ and 3.43 x 10/sup 4/ liter x mole/sup -1/ x cm/sup -1/, Sandell sensitivities 2.0 and 5.0 ng x cm/sup 12/, and coefficients of variation +/-1.40 and +/-1.06 respectively.

  14. Near-ultraviolet absorption annealing in hafnium oxide thin films subjected to continuous-wave laser radiation

    NASA Astrophysics Data System (ADS)

    Papernov, Semyon; Kozlov, Alexei A.; Oliver, James B.; Kessler, Terrance J.; Shvydky, Alexander; Marozas, Brendan

    2014-12-01

    Hafnium oxide (HfO2) is the most frequently used high-index material in multilayer thin-film coatings for high-power laser applications ranging from near-infrared to near-ultraviolet (UV). Absorption in this high-index material is also known to be responsible for nanosecond-pulse laser-damage initiation in multilayers. In this work, modification of the near-UV absorption of HfO2 monolayer films subjected to irradiation by continuous-wave (cw), 355-nm or 351-nm laser light focused to produce power densities of the order of ˜100 kW/cm2 is studied. Up to a 70% reduction in absorption is found in the areas subjected to irradiation. Temporal behavior of absorption is characterized by a rapid initial drop on the few-tens-of-seconds time scale, followed by a longer-term decline to a steady-state level. Absorption maps generated by photothermal heterodyne imaging confirm the permanent character of the observed effect. Nanosecond-pulse, 351-nm and 600-fs, 1053-nm laser-damage tests performed on these cw laser-irradiated areas confirm a reduction of absorption by measuring up to 25% higher damage thresholds. We discuss possible mechanisms responsible for near-UV absorption annealing and damage-threshold improvement resulting from irradiation by near-UV cw laser light.

  15. Ni ion release, osteoblast-material interactions, and hemocompatibility of hafnium-implanted NiTi alloy.

    PubMed

    Zhao, Tingting; Li, Yan; Zhao, Xinqing; Chen, Hong; Zhang, Tao

    2012-04-01

    Hafnium ion implantation was applied to NiTi alloy to suppress Ni ion release and enhance osteoblast-material interactions and hemocompatibility. The auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscope results showed that a composite TiO(2)/HfO(2) nanofilm with increased surface roughness was formed on the surface of NiTi, and Ni concentration was reduced in the superficial surface layer. Potentiodynamic polarization tests displayed that 4 mA NiTi sample possessed the highest E(br) - E(corr), 470 mV higher than that of untreated NiTi, suggesting a significant improvement on pitting corrosion resistance. Inductively coupled plasma mass spectrometry tests during 60 days immersion demonstrated that Ni ion release rate was remarkably decreased, for example, a reduction of 67% in the first day. The water contact angle increased and surface energy decreased after Hf implantation. Cell culture and methyl-thiazol-tetrazolium indicated that Hf-implanted NiTi expressed enhanced osteoblasts adhesion and proliferation, especially after 7 days culture. Hf implantation decreased fibrinogen adsorption, but had almost no effect on albumin adsorption. Platelets adhesion and activation were suppressed significantly (97% for 4 mA NiTi) and hemolysis rate was decreased by at least 57% after Hf implantation. Modified surface composition and morphology and decreased surface energy should be responsible for the improvement of cytocompatibility and hemocompatibility.

  16. Extraction of short-lived zirconium and hafnium isotopes usingcrown ethers: A model system for the study of rutherfordium

    SciTech Connect

    Sudowe, Ralf; Calvert, Michael G.; Dullmann, Christoph E.; Farina, Lindsy M.; Folden III, Charles M.; Gregorich, Kenneth E.; Gallaher, Sarah E.H.; Nelson, Sarah L.; Phillips, Diana C.; Schwantes,Jon M.; Wilson, Richard E.; Zielinski Peter M.; Hoffman, Darleane C.; Nitsche Heino

    2005-07-06

    The extraction of zirconium and hafnium from hydrochloric acid media was studied using the crown ethers dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 (DC18C6) and dicyclohexano-24-crown-8 (DC24C8) as extractants. The goal was to find an extraction system that exhibits a high selectivity between the members of group 4 of the periodic table and is suitable for the study of rutherfordium. It was found that Zr and Hf are both extracted using DB18C6, DC18C6 and DC24C8. The extraction yield increases with increasing acid concentration and increasing concentration of crown ether. The extracted species most likely consists of an ion-association complex formed between a Zr or Hf chloro complex and a hydronium crown ether complex. Conditions can be found for each extractant that provide for the separation of Zr from Hf. This selective separation between Zr and Hf makes the extraction with crown ethers from HCl well suited to study the extraction behavior of Rf and compare it to the behavior of Zr and Hf. These extraction systems can be used to determine whether the extraction behavior of Rf is similar to Zr, similar to Hf or follows the trend established by the lighter homologs. The extraction kinetics are fast enough for the study of the 78-s isotope {sup 261}Rf.

  17. Fiber textures of titanium nitride and hafnium nitride thin films deposited by off-normal incidence magnetron sputtering

    SciTech Connect

    Deniz, D.; Harper, J. M. E.

    2008-09-15

    We studied the development of crystallographic texture in titanium nitride (TiN) and hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. For a deposition angle of 40 deg. from substrate normal, we obtained TiN biaxial textures for a range of deposition conditions using radio frequency (rf) sputtering. Typically, we find that the <111> orientation is close to the substrate normal and the <100> orientation is close to the direction of the deposition source, showing substantial in-plane alignment. We also introduced a 150 eV ion beam at 55 deg. with respect to substrate normal during rf sputtering of TiN. Ion beam enhancement caused TiN to align its out-of-plane texture along <100> orientation. In this case, (200) planes are slightly tilted with respect to the substrate normal away from the ion beam source, and (111) planes are tilted 50 deg. toward the ion beam source. For comparison, we found that HfN deposited at 40 deg. without ion bombardment has a strong <100> orientation parallel to the substrate normal. These results are consistent with momentum transfer among adatoms and ions followed by an increase in surface diffusion of the adatoms on (200) surfaces. The type of fiber texture results from a competition among texture mechanisms related to surface mobilities of adatoms, geometrical, and directional effects.

  18. Thermomechanical and Thermochemical Behavior of a Hafnium-20 Percent Tantalum Alloy. Ph.D. Thesis - North Carolina State Univ., Raleigh

    NASA Technical Reports Server (NTRS)

    Howell, J. P.

    1971-01-01

    An investigation was conducted to determine the thermomechanical and thermochemical behavior of a high temperature, oxidation resistant, hafnium-20 percent tantalum alloy. The elastic and shear moduli of this alloy were determined in air up to 1000 C and in vacuum up to 2000 C using a mechanical resonance technique. The internal friction of the alloy was measured up to temperatures greater than 1400 C. Room temperature stress-strain behavior of the oxidized and unoxidized alloy was established. The effect of annealing on the elastic and shear moduli of the extruded rod material was investigated. The martensitic-type phase transformation occurring in the alloy was studied using hot stage metallography and electron microscopy. Static oxidation tests were conducted on the alloy at temperatures from 1000 C to 1700 C with weight gain measurements made as a function of time and temperatures. Surface morphology studies were conducted on the oxide coatings formed at the different temperatures using scanning electron microscopy and X-ray diffraction techniques.

  19. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; Stubbins, James F.

    2015-01-26

    We report comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y2O3, fluorite Y2O3–HfO2 solid solution and pyrochlore (or fluorite) Y2(Ti,Hf)2 - xO7 - x. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Moreover, two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. Our results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation.

  20. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    DOE PAGES

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; et al

    2015-01-26

    We report comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y2O3, fluorite Y2O3–HfO2 solid solution and pyrochlore (or fluorite) Y2(Ti,Hf)2 - xO7 - x. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Moreover, two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and themore » steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. Our results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation.« less

  1. Evidence supporting biologically mediated sulfide oxidation in hot spring ecosystems

    NASA Astrophysics Data System (ADS)

    Cox, A. D.; Shock, E.

    2011-12-01

    The sulfide concentration of fluids in hydrothermal ecosystems is one of several factors determining the transition to microbial photosynthesis (Cox et al., 2011, Chem. Geol. 280, 344-351). To investigate the loss of sulfide in Yellowstone hot spring systems, measurements of total dissolved sulfide with respect to time were made in incubation experiments conducted on 0.2-micron filtered (killed controls) vs. unfiltered hot spring water at locations with three different pH:sulfide combinations (pH 2.5 with 50 μM sulfide, 5.2 with 5.6 μM sulfide, and 8.3 with 86 μM sulfide). At the higher pH values, the experiments yielded similar rates of sulfide loss in filtered and unfiltered water of approximately 0.8 (pH 5.2) and 7.6 nmol sulfide L-1s-1 (pH 8.3). At the acidic spring, the unfiltered water lost sulfide at a rate 1.6 times that of the filtered water (8.2 vs. 5 nmol sulfide L-1s-1). These results suggest that the pelagic biomass at the pH 5.2 and 8.3 springs may not affect sulfide loss, whereas in the pH 2.5 spring there appears to be an effect. In addition, the incubation of filamentous biomass with unfiltered water increased the rate of sulfide loss by approximately two-fold at a pH of 2.5 (59 vs. 31 nmol L-1s-1; Cox et al., 2011), five-fold at a pH of 5.2 (3.9 vs. 0.8 nmol sulfide L-1s-1), and barely increased the rate of sulfide loss at a pH of 8.3 (9.1 vs. 8.4 nmol sulfide L-1s-1). Sulfide is predominately present as HS- at a pH of 8.3, which may not be taken up as easily by microorganisms as the H2S (aq) that dominates sulfide speciation at pH 2.5 and 5.2. That the loss of sulfide at acidic pH is due to biotic rather than abiotic factors is further supported by studies with whole mat samples that show greater sulfide consumption than killed controls (D'Imperio et al., 2008, AEM 74, 5802-5808). Taken together, the results of these experiments suggest that the majority of sulfide oxidation occurs in the filamentous biomass of hot spring ecosystems, although

  2. Trap state passivation improved hot-carrier instability by zirconium-doping in hafnium oxide in a nanoscale n-metal-oxide semiconductor-field effect transistors with high-k/metal gate

    NASA Astrophysics Data System (ADS)

    Liu, Hsi-Wen; Chang, Ting-Chang; Tsai, Jyun-Yu; Chen, Ching-En; Liu, Kuan-Ju; Lu, Ying-Hsin; Lin, Chien-Yu; Tseng, Tseung-Yuen; Cheng, Osbert; Huang, Cheng-Tung; Ye, Yi-Han

    2016-04-01

    This work investigates the effect on hot carrier degradation (HCD) of doping zirconium into the hafnium oxide high-k layer in the nanoscale high-k/metal gate n-channel metal-oxide-semiconductor field-effect-transistors. Previous n-metal-oxide semiconductor-field effect transistor studies demonstrated that zirconium-doped hafnium oxide reduces charge trapping and improves positive bias temperature instability. In this work, a clear reduction in HCD is observed with zirconium-doped hafnium oxide because channel hot electron (CHE) trapping in pre-existing high-k bulk defects is the main degradation mechanism. However, this reduced HCD became ineffective at ultra-low temperature, since CHE traps in the deeper bulk defects at ultra-low temperature, while zirconium-doping only passivates shallow bulk defects.

  3. Development of a high-resolution inductively-coupled argon plasma apparatus for derivative spectrometry and its application to the determination of hafnium in high-purity zirconium oxide.

    PubMed

    Ishii, H; Satoh, K

    1982-04-01

    A high-resolution apparatus for inductively-coupled plasma emission spectrometry (ICPES) has been developed, based on an echelle spectrometer modified for wavelength modulation with a quartz refractor plate. The selectivity of the technique is thus improved, and small amounts of hafnium in high-purity zirconium oxide can be determined directly without prior separation or preconcentration. A straight-line calibration curve passing through the origin is obtained without any correction for the interference from zirconium which exists in large excess. The detection limit for hafnium is 0.06 microg/ml, and the relative standard deviation (10 replicates) for hafnium at the 1.2 microg/ml level is about 3%.

  4. Application of zone-melting technique to metal chelate systems-XI Refining of tetrakis(di-n-propionylmethanato)zirconium(IV) from hafnium and trace amounts of some other metals.

    PubMed

    Yoshida, I; Kobayashi, H; Ueno, K

    1977-01-01

    The zone-melting method was applied to purification of tetrakis(di-n-propionylmethanato)zirconium(IV) which contained copper(II), nickel(II), cobalt(II and III), iron(III) and hafnium(IV) in the forms of their chelates with the common ligand. All minor components having effective distribution coefficients < 1 in the zirconium(IV) chelate were concentrated toward the terminal end of the refining column. When an aqueous solution of zirconium(IV) containing zinC(II) and manganese(II) in addition to the metal contaminants above was treated with di-n-propionylmethane to precipitate the chelate complexes, only zinc, iron and hafnium were found in the precipitated zirconium chelate. The first two were ettectively removed by zone-melting. Though the separation of hafnium was poorer, the technique was efficient enough for practical purposes. PMID:18962026

  5. Removal of copper from carbon-saturated steel with an aluminum sulfide/iron sulfide slag

    SciTech Connect

    Cohen, A.; Blander, M.

    1995-12-01

    Scrap iron and steel has long been considered a resource in the steel-making industry, and its value is largely determined by its impurity content. As the mini-mills, the major consumers of scrap iron and steel, expand into producing flat-rolled sheet, the demand for high-quality scrap will increase. Of the impurities present in scrap, copper is particularly troublesome because of its role in causing hot shortness. Therefore, the copper content of scrap should be kept below {approx} 0.1 wt%. A method for removing copper from steel could be used to improve the quality of scrap and make it more available for use by mini-mills. To determine the effectiveness of a binary slag consisting of aluminum sulfide and iron sulfide on the removal of copper from steel and iron, the distribution coefficient of copper between the slag and a carbon-saturated iron melt was investigated at 1,365 C. The composition of the slag was varied from nearly pure aluminum sulfide to pure iron sulfide. A maximum distribution coefficient of 30 was found, and the copper level in the iron melt was reduced to as low as 0.07 wt.% with a 4:1 ratio of iron to slag.

  6. Mitochondrial adaptations to utilize hydrogen sulfide for energy and signaling.

    PubMed

    Olson, Kenneth R

    2012-10-01

    Sulfur is a versatile molecule with oxidation states ranging from -2 to +6. From the beginning, sulfur has been inexorably entwined with the evolution of organisms. Reduced sulfur, prevalent in the prebiotic Earth and supplied from interstellar sources, was an integral component of early life as it could provide energy through oxidization, even in a weakly oxidizing environment, and it spontaneously reacted with iron to form iron-sulfur clusters that became the earliest biological catalysts and structural components of cells. The ability to cycle sulfur between reduced and oxidized states may have been key in the great endosymbiotic event that incorporated a sulfide-oxidizing α-protobacteria into a host sulfide-reducing Archea, resulting in the eukaryotic cell. As eukaryotes slowly adapted from a sulfidic and anoxic (euxinic) world to one that was highly oxidizing, numerous mechanisms developed to deal with increasing oxidants; namely, oxygen, and decreasing sulfide. Because there is rarely any reduced sulfur in the present-day environment, sulfur was historically ignored by biologists, except for an occasional report of sulfide toxicity. Twenty-five years ago, it became evident that the organisms in sulfide-rich environments could synthesize ATP from sulfide, 10 years later came the realization that animals might use sulfide as a signaling molecule, and only within the last 4 years did it become apparent that even mammals could derive energy from sulfide generated in the gastrointestinal tract. It has also become evident that, even in the present-day oxic environment, cells can exploit the redox chemistry of sulfide, most notably as a physiological transducer of oxygen availability. This review will examine how the legacy of sulfide metabolism has shaped natural selection and how some of these ancient biochemical pathways are still employed by modern-day eukaryotes. PMID:22430869

  7. Effect of sulfide ions on complement factor C3.

    PubMed Central

    Granlund-Edstedt, M; Johansson, E; Claesson, R; Carlsson, J

    1991-01-01

    In infected sites such as the gingival pockets of patients with periodontal disease, sulfide levels up to 1 mmol/liter may be reached. There is little information, however, on how sulfide may interact with the host defense. In a previous study (R. Claesson, M. Granlund-Edstedt, S. Persson, and J. Carlsson, Infect. Immun. 57:2776-2781, 1989), it was shown that polymorphonuclear leukocytes were able to kill bacteria in the presence of 1 mM sulfide. However, sulfide seemed to interfere with the opsonization of the bacteria. It has been claimed that sulfide may be toxic by splitting disulfide bonds of proteins. In the present study, serum was exposed to 2 mM sulfide under anaerobic conditions, and the capacity of sulfide to split disulfide bonds of 10 serum proteins involved in opsonization was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunodetection of the proteins after blotting. Sulfide had a low capacity to split the disulfide bonds of most proteins. Sulfide had, however, a pronounced effect on the complement component C3 in the form of C3bi. Sulfide released the C-terminal region of the alpha chain from C3bi. When C3 opsonizes bacteria, it is this region of C3bi which binds to complement receptor 3 (CR3) of the polymorphonuclear leukocytes. If sulfide has the same effect on C3bi deposited on the bacterial surface as it has on C3bi in solution, it will annihilate the very important contribution of C3bi to opsonization. Images PMID:1987085

  8. High temperature regenerable hydrogen sulfide removal agents

    DOEpatents

    Copeland, Robert J.

    1993-01-01

    A system for high temperature desulfurization of coal-derived gases using regenerable sorbents. One sorbent is stannic oxide (tin oxide, SnO.sub.2), the other sorbent is a metal oxide or mixed metal oxide such as zinc ferrite (ZnFe.sub.2 O.sub.4). Certain otherwise undesirable by-products, including hydrogen sulfide (H.sub.2 S) and sulfur dioxide (SO.sub.2) are reused by the system, and elemental sulfur is produced in the regeneration reaction. A system for refabricating the sorbent pellets is also described.

  9. Biogenic production of dimethyl sulfide: Krill grazing

    SciTech Connect

    Daly, K.L.; DiTullio, G.R. )

    1993-01-01

    Dimethyl sulfide (DMS), a dominant sulfur compound in sea water, is a possible precursor for cloud condensation nuclei in the atmosphere and may influence global climate. The primary source of DMS is phytoplankton, but the mechanisms remain uncertain, and concentrations of DMS in the ocean vary spatially and temporally. Laboratory studies suggest zooplankton grazing may be an important process leading to the formation of DMS in the ocean. This paper describes ocean studies which examine the suggestion that grazing by krill may be a significant source for DMS production in the antarctic coastal region. 11 refs., 2 figs.

  10. Hydrogen sulfide: physiological properties and therapeutic potential in ischaemia.

    PubMed

    Bos, Eelke M; van Goor, Harry; Joles, Jaap A; Whiteman, Matthew; Leuvenink, Henri G D

    2015-03-01

    Hydrogen sulfide (H2 S) has become a molecule of high interest in recent years, and it is now recognized as the third gasotransmitter in addition to nitric oxide and carbon monoxide. In this review, we discuss the recent literature on the physiology of endogenous and exogenous H2 S, focusing upon the protective effects of hydrogen sulfide in models of hypoxia and ischaemia.

  11. Normal state properties of the ternary molybdenum sulfides

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Alterovitz, S. A.

    1978-01-01

    By making a large number of normal state and superconducting properties measurements, all on the same ternary molybdenum sulfide samples, we obtain values for Fermi surface and superconducting parameters. From these we conclude that sputtered ternary molybdenum sulfides are not completely in the dirty superconductor limit, and that they are d-band metals with a high electron carrier density.

  12. 46 CFR 148.285 - Metal sulfide concentrates.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Metal sulfide concentrates. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 Metal sulfide concentrates. (a) When information given by the shipper under § 148.60 of this part indicates that the...

  13. 46 CFR 148.285 - Metal sulfide concentrates.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Metal sulfide concentrates. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 Metal sulfide concentrates. (a) When information given by the shipper under § 148.60 of this part indicates that the...

  14. 46 CFR 148.285 - Metal sulfide concentrates.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Metal sulfide concentrates. 148.285 Section 148.285... MATERIALS THAT REQUIRE SPECIAL HANDLING Special Requirements for Certain Materials § 148.285 Metal sulfide concentrates. (a) When information given by the shipper under § 148.60 of this part indicates that the...

  15. Protection of steel from hydrogen sulfide corrosion by bactericides

    SciTech Connect

    Abbasov, V.M.; Mamedov, I.A.; Abdullaev, E.Sh.

    1995-03-01

    Modern effective inhibitors, Araz-1 and INFKh-4, are recommended for preventing the corrosion of oilfield equipment affected by hydrogen sulfide and sulfate-reducing bacteria. Both inhibitors have undergone full-scale field tests and have shown highly effective inhibition of corrosion in two-phase hydrocarbon-electrolyte media saturated with hydrogen sulfide.

  16. 21 CFR 872.1870 - Sulfide detection device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Sulfide detection device. 872.1870 Section 872.1870 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1870 Sulfide detection device. (a)...

  17. 40 CFR 721.5075 - Mixed methyltin mercaptoester sulfides.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Mixed methyltin mercaptoester sulfides... Substances § 721.5075 Mixed methyltin mercaptoester sulfides. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as mixed methyltin...

  18. Temperature-programmed sulfiding of precursor cobalt oxide genesis of highly active sites on sulfided cobalt catalyst for hydrogenation and isomerization

    SciTech Connect

    Inamura, Kazuhiro; Takyu, Toshiyuki ); Okamoto, Yasuaki; Nagata, Kozo; Imanaka, Toshinobu )

    1992-02-01

    It was found that the method of sulfidation of cobalt oxide strongly affects the catalytic activities and selectivities of the resultant cobalt sulfide catalyst, as well as the calcination temperature of the cobalt oxide. When cobalt oxide was sulfided at 673 K by a temperature-programmed sulfiding method (a heating rate of 6 K/min), catalytic activities for the hydrogenation of butadiene and the isomerization of 1-butene were considerably enhanced compared with those for cobalt sulfide prepared by isothermal sulfidation at 673 K. Results of temperature-programmed sulfiding (TPS), temperature-programmed reduction (TPR), and X-ray diffraction (XRD) suggest that the catalysts showing high catalytic activities after sulfidation are partially sulfided at 673 K and consist of the unsulfided cobalt core phases (CoO or metallic Co). The sulfidation property of precursor cobalt oxides has been studied using TPS, simulating the sulfidation process of the cobalt sulfide catalysts. Two distinctly different kinds of sulfidation process are estimated by TPS measurements of the cobalt oxides. The calcination temperature of the precursor cobalt oxides strongly affects the sulfidation paths. They are differentiated in terms of the presence of a metallic Co intermediate. The relationship of the mechanism of sulfidation of the cobalt oxides to the generation of highly active sites is discussed.

  19. As-Received, Ozone Cleaned and Ar+ Sputtered Surfaces of Hafnium Oxide Grown by Atomic Layer Deposition and Studied by XPS

    SciTech Connect

    Engelhard, Mark H.; Herman, Jacob A.; Wallace, Robert; Baer, Donald R.

    2012-06-27

    In this study, X-ray photoelectron spectroscopy (XPS) characterization was performed on 47 nm thick hafnium oxide (HfO{sub 2}) films grown by atomic layer deposition using TEMA-Hf/H{sub 2}O at 250 C substrate temperature. HfO{sub 2} is currently being studied as a possible replacement for Silicon Oxide (SiO{sub 2}) as a gate dielectric in electronics transistors. XPS spectra were collected on a Physical Electronics Quantum 2000 Scanning ESCA Microprobe using a monochromatic Al K{sub a} X-ray (1486.7 eV) excitation source. The sample was analyzed under the following conditions: as received, after UV irradiation for five minutes, and after sputter cleaning with 2 kV Ar{sup +} ions for 180 seconds. Survey scans showed carbon, oxygen, and hafnium as the major species in the film, while the only minor species of argon and carbide was detected after sputtering. Adventitious carbon initially composed approximately 18.6 AT% of the surface, but after UV cleaning it was reduced to 2.4 AT%. This demonstrated that that the majority of carbon was due to adventitious carbon. However, after 2 kV Ar{sup +} sputtering there was still only trace amounts of carbon at {approx}1 AT%, Some of this trace carbon is now in the form of a carbide due to the interaction with Ar{sup +} used for sputter cleaning. Furthermore, the stoiciometric ratio of oxygen and hafnium is consistent with a high quality HfO{sub 2} film.

  20. Calculation of sulfide capacities of multicomponent slags

    NASA Astrophysics Data System (ADS)

    Pelton, Arthur D.; Eriksson, Gunnar; Romero-Serrano, Antonio

    1993-10-01

    The Reddy-Blander model for the sulfide capacities of slags has been modified for the case of acid slags and to include A12O3 and TiO2 as components. The model has been extended to calculate a priori sulfide capacities of multicomponent slags, from a knowledge of the thermodynamic activities of the component oxides, with no adjustable parameters. Agreement with measurements is obtained within experimental uncertainty for binary, ternary, and quinary slags involving the components SiO2-Al2O3-TiO2-CaO-MgO-FeO-MnO over wide ranges of composition. The oxide activities used in the computations are calculated from a database of model parameters obtained by optimizing thermodynamic and phase equilibrium data for oxide systems. Sulfur has now been included in this database. A computing system with automatic access to this and other databases has been developed to permit the calculation of the sulfur content of slags in multicomponent slag/metal/gas/solid equilibria.

  1. Effect of palladium on sulfide tarnishing of noble metal alloys.

    PubMed

    Suoninen, E; Herø, H; Minni, E

    1985-10-01

    Electron spectroscopic studies of Au-Ag-Cu alloys of the type used for dental castings show that small additions (less than or equal to 3 wt%) of palladium reduce essentially the thickness of the sulfide layer formed on surfaces of samples treated in aqueous Na2S solutions. Relative to silver, palladium does not enrich in the sulfide, but statistically significant enrichment is found immediately below the sulfide layer. This enrichment probably takes place during the exposure of the substrate surface to atmosphere before the sulfiding treatment. The mechanism of the impeding effect of palladium on sulfiding is assumed to be a decrease in diffusion from the bulk alloy to the surface due to the enriched layer. The effect cannot be explained by changes in the electronic structure of the alloy due to palladium alloying.

  2. Physical and microstructural aspects of iron sulfide degradation in concrete

    SciTech Connect

    Schmidt, Thomas; Gallucci, Emanuel; Scrivener, Karen

    2011-03-15

    The microstructural aspects of iron sulfide degradation in dam concrete were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in both dam concrete samples and laboratory concrete. The results show that iron sulfide inclusions with a diameter of a few micrometers in the aggregates are reactive and appear to generate expansion first in the aggregates and consequently in the cement paste. The expansion from the iron sulfides is a consequence of the increase in volume of the reaction products formed. The types of iron sulfide present in the aggregate, mainly pyrrhotite (FeS) and pyrite (FeS{sub 2}), show similar reaction behavior in the aggregates. The released sulfate can lead to a secondary ettringite formation in the concrete matrix, but the degradation associated with this appears to be minor. The reaction of the iron sulfides was found to be very slow even when laboratory samples were exposed to elevated temperatures.

  3. The Hydrolysis of Carbonyl Sulfide at Low Temperature: A Review

    PubMed Central

    Zhao, Shunzheng; Yi, Honghong; Tang, Xiaolong; Jiang, Shanxue; Gao, Fengyu; Zhang, Bowen; Zuo, Yanran; Wang, Zhixiang

    2013-01-01

    Catalytic hydrolysis technology of carbonyl sulfide (COS) at low temperature was reviewed, including the development of catalysts, reaction kinetics, and reaction mechanism of COS hydrolysis. It was indicated that the catalysts are mainly involved metal oxide and activated carbon. The active ingredients which can load on COS hydrolysis catalyst include alkali metal, alkaline earth metal, transition metal oxides, rare earth metal oxides, mixed metal oxides, and nanometal oxides. The catalytic hydrolysis of COS is a first-order reaction with respect to carbonyl sulfide, while the reaction order of water changes as the reaction conditions change. The controlling steps are also different because the reaction conditions such as concentration of carbonyl sulfide, reaction temperature, water-air ratio, and reaction atmosphere are different. The hydrolysis of carbonyl sulfide is base-catalyzed reaction, and the force of the base site has an important effect on the hydrolysis of carbonyl sulfide. PMID:23956697

  4. Luminal sulfide and large intestine mucosa: friend or foe?

    PubMed

    Blachier, François; Davila, Anne-Marie; Mimoun, Sabria; Benetti, Pierre-Henri; Atanasiu, Calina; Andriamihaja, Mireille; Benamouzig, Robert; Bouillaud, Frédéric; Tomé, Daniel

    2010-07-01

    Hydrogen sulfide (H(2)S) is present in the lumen of the human large intestine at millimolar concentrations. However, the concentration of free (unbound) sulfide is in the micromolar range due to a large capacity of fecal components to bind the sulfide. H(2)S can be produced by the intestinal microbiota from alimentary and endogenous sulfur-containing compounds including amino acids. At excessive concentration, H(2)S is known to severely inhibit cytochrome c oxidase, the terminal oxidase of the mitochondrial electron transport chain, and thus mitochondrial oxygen (O(2)) consumption. However, the concept that sulfide is simply a metabolic troublemaker toward colonic epithelial cells has been challenged by the discovery that micromolar concentration of H(2)S is able to increase the cell respiration and to energize mitochondria allowing these cells to detoxify and to recover energy from luminal sulfide. The main product of H(2)S metabolism by the colonic mucosa is thiosulfate. The enzymatic activities involved in sulfide oxidation by the colonic epithelial cells appear to be sulfide quinone oxidoreductase considered as the first and rate-limiting step followed presumably by the action of sulfur dioxygenase and rhodanese. From clinical studies with human volunteers and experimental works with rodents, it appears that H(2)S can exert mostly pro- but also anti-inflammatory effects on the colonic mucosa. From the available data, it is tempting to propose that imbalance between the luminal concentration of free sulfide and the capacity of colonic epithelial cells to metabolize this compound will result in an impairment of the colonic epithelial cell O(2) consumption with consequences on the process of mucosal inflammation. In addition, endogenously produced sulfide is emerging as a prosecretory neuromodulator and as a relaxant agent toward the intestinal contractibility. Lastly, sulfide has been recently described as an agent involved in nociception in the large intestine

  5. Measurement and biological significance of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices.

    PubMed

    Tangerman, Albert

    2009-10-15

    This review deals with the measurement of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices of rats and humans (blood, serum, tissues, urine, breath, feces and flatus). Hydrogen sulfide and methanethiol both contain the active thiol (-SH) group and appear in the free gaseous form, in the acid-labile form and in the dithiothreitol-labile form. Dimethyl sulfide is a neutral molecule and exists only in the free form. The foul odor of these sulfur volatiles is a striking characteristic and plays a major role in bad breath, feces and flatus. Because sulfur is a biologically active element, the biological significance of the sulfur volatiles are also highlighted. Despite its highly toxic properties, hydrogen sulfide has been lately recommended to become the third gasotransmitter, next to nitric oxide and carbon monoxide, based on high concentration found in healthy tissues, such as blood and brain. However, there is much doubt about the reliability of the assay methods used. Many artifacts in the sulfide assays exist. The methods to detect the various forms of hydrogen sulfide are critically reviewed and compared with findings of our group. Recent findings that free gaseous hydrogen sulfide is absent in whole blood urged the need to revisit its role as a blood-borne signaling molecule.

  6. DISSOLUTION OF PLUTONIUM CONTAINING CARRIER PRECIPITATE BY CARBONATE METATHESIS AND SEPARATION OF SULFIDE IMPURITIES THEREFROM BY SULFIDE PRECIPITATION

    DOEpatents

    Duffield, R.B.

    1959-07-14

    A process is described for recovering plutonium from foreign products wherein a carrier precipitate of lanthanum fluoride containing plutonium is obtained and includes the steps of dissolving the carrier precipitate in an alkali metal carbonate solution, adding a soluble sulfide, separating the sulfide precipitate, adding an alkali metal hydroxide, separating the resulting precipitate, washing, and dissolving in a strong acid.

  7. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    NASA Astrophysics Data System (ADS)

    Gaballa, Osama Gaballa Bahig

    Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

  8. Silicon Nanowires with High-k Hafnium Oxide Dielectrics for Sensitive Detection of Small Nucleic Acid Oligomers

    PubMed Central

    Dorvel, Brian R.; Reddy, Bobby; Go, Jonghyun; Guevara, Carlos Duarte; Salm, Eric; Alam, Muhammad Ashraful; Bashir, Rashid

    2012-01-01

    Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in Point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO2), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFET’s has been small oligonucleotides, more specifically microRNA (miRNA). MicroRNA’s are small RNA oligonucleotides which bind to messenger RNA’s, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO2 dielectric based silicon nanowires for biosensing applications. Here we demonstrate sensing of single stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100fM detection levels of miR-10b DNA analogue, with a theoretical limit of detection of 1fM. Moreover, the non-complementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform. PMID:22695179

  9. Silicon nanowires with high-k hafnium oxide dielectrics for sensitive detection of small nucleic acid oligomers.

    PubMed

    Dorvel, Brian R; Reddy, Bobby; Go, Jonghyun; Duarte Guevara, Carlos; Salm, Eric; Alam, Muhammad Ashraful; Bashir, Rashid

    2012-07-24

    Nanobiosensors based on silicon nanowire field effect transistors offer advantages of low cost, label-free detection, and potential for massive parallelization. As a result, these sensors have often been suggested as an attractive option for applications in point-of-care (POC) medical diagnostics. Unfortunately, a number of performance issues, such as gate leakage and current instability due to fluid contact, have prevented widespread adoption of the technology for routine use. High-k dielectrics, such as hafnium oxide (HfO(2)), have the known ability to address these challenges by passivating the exposed surfaces against destabilizing concerns of ion transport. With these fundamental stability issues addressed, a promising target for POC diagnostics and SiNWFETs has been small oligonucleotides, more specifically, microRNA (miRNA). MicroRNAs are small RNA oligonucleotides which bind to mRNAs, causing translational repression of proteins, gene silencing, and expressions are typically altered in several forms of cancer. In this paper, we describe a process for fabricating stable HfO(2) dielectric-based silicon nanowires for biosensing applications. Here we demonstrate sensing of single-stranded DNA analogues to their microRNA cousins using miR-10b and miR-21 as templates, both known to be upregulated in breast cancer. We characterize the effect of surface functionalization on device performance using the miR-10b DNA analogue as the target sequence and different molecular weight poly-l-lysine as the functionalization layer. By optimizing the surface functionalization and fabrication protocol, we were able to achieve <100 fM detection levels of the miR-10b DNA analogue, with a theoretical limit of detection of 1 fM. Moreover, the noncomplementary DNA target strand, based on miR-21, showed very little response, indicating a highly sensitive and highly selective biosensing platform.

  10. Oxidation Characterization of Hafnium-Based Ceramics Fabricated by Hot Pressing and Electric Field-Assisted Sintering

    NASA Technical Reports Server (NTRS)

    Gasch, Matt; Johnson, Sylvia; Marschall, Jochen

    2010-01-01

    Ceramic borides, such as hafnium diboride (HfB2) and zirconium diboride (ZrB2), are members of a family of materials with extremely high melting temperatures referred to as Ultra High Temperature Ceramics (UHTCs). UHTCs constitute a class of promising materials for use in high temperature applications, such as sharp leading edges on future-generation hypersonic flight vehicles, because of their high melting points. The controlled development of microstructure has become important to the processing of UHTCs, with the prospect of improving their mechanical and thermal properties. The improved oxidation resistance of HfB2 has also become important if this material is to be successfully used at temperatures above 2000 C. Furthermore, the use of UHTCs on the leading edges of vehicles traveling at hypersonic speeds will mean exposure to a mixed oxidation environment comprised of both molecular and atomic oxygen. The current study has investigated the high-temperature oxidation behavior of HfB2-based materials in a pure O2 environment, as well as in environments containing different levels of dissociated oxygen (O/O2). Materials were processed by two techniques: conventional hot pressing (HP) and electric field-assisted sintering (FAS). Their oxidation behavior was evaluated in both a tube furnace at 1250 C for 3 hours and in a simulated re-entry environment in the Advanced Heating Facility (AHF) arcjet at NASA Ames Research Center, during a 10-minute exposure to a cold wall heat flux of 250W/sq cm and stagnation pressure of 0.1-0.2 atm. The microstructure of the different materials was characterized before and after oxidation using scanning electron microscopy (SEM).

  11. Influence of interlayer trapping and detrapping mechanisms on the electrical characterization of hafnium oxide/silicon nitride stacks on silicon

    SciTech Connect

    Garcia, H.; Duenas, S.; Castan, H.; Gomez, A.; Bailon, L.; Toledano-Luque, M.; Prado, A. del; Martil, I.; Gonzalez-Diaz, G.

    2008-11-01

    Al/HfO{sub 2}/SiN{sub x}:H/n-Si metal-insulator-semiconductor capacitors have been studied by electrical characterization. Films of silicon nitride were directly grown on n-type silicon substrates by electron cyclotron resonance assisted chemical vapor deposition. Silicon nitride thickness was varied from 3 to 6.6 nm. Afterwards, 12 nm thick hafnium oxide films were deposited by the high-pressure sputtering approach. Interface quality was determined by using current-voltage, capacitance-voltage, deep-level transient spectroscopy (DLTS), conductance transients, and flatband voltage transient techniques. Leakage currents followed the Poole-Frenkel emission model in all cases. According to the simultaneous measurement of the high and low frequency capacitance voltage curves, the interface trap density obtained for all the samples is in the 10{sup 11} cm{sup -2} eV{sup -1} range. However, a significant increase in this density of about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride interfacial layers. In this work we probe that this increase is an artifact that must be attributed to traps existing at the HfO{sub 2}/SiN{sub x}:H intralayer interface. These traps are more easily charged or discharged as this interface comes near to the substrate, that is, as thinner the SiN{sub x}:H interface layer is. The trapping/detrapping mechanism increases the capacitance transient and, in consequence, the DLTS measurements have contributions not only from the insulator/substrate interface but also from the HfO{sub 2}/SiN{sub x}:H intralayer interface.

  12. Amorphous molybdenum sulfides as hydrogen evolution catalysts.

    PubMed

    Morales-Guio, Carlos G; Hu, Xile

    2014-08-19

    Providing energy for a population projected to reach 9 billion people within the middle of this century is one of the most pressing societal issues. Burning fossil fuels at a rate and scale that satisfy our near-term demand will irreversibly damage the living environment. Among the various sources of alternative and CO2-emission-free energies, the sun is the only source that is capable of providing enough energy for the whole world. Sunlight energy, however, is intermittent and requires an efficient storage mechanism. Sunlight-driven water splitting to make hydrogen is widely considered as one of the most attractive methods for solar energy storage. Water splitting needs a hydrogen evolution catalyst to accelerate the rate of hydrogen production and to lower the energy loss in this process. Precious metals such as Pt are superior catalysts, but they are too expensive and scarce for large-scale applications. In this Account, we summarize our recent research on the preparation, characterization, and application of amorphous molybdenum sulfide catalysts for the hydrogen evolution reaction. The catalysts can be synthesized by electrochemical deposition under ambient conditions from readily available and inexpensive precursors. The catalytic activity is among the highest for nonprecious catalysts. For example, at a loading of 0.2 mg/cm(2), the optimal catalyst delivers a current density of 10 mA/cm(2) at an overpotential of 160 mV. The growth mechanism of the electrochemically deposited film catalysts was revealed by an electrochemical quartz microcrystal balance study. While different electrochemical deposition methods produce films with different initial compositions, the active catalysts are the same and are identified as a "MoS(2+x)" species. The activity of the film catalysts can be further promoted by divalent Fe, Co, and Ni ions, and the origins of the promotional effects have been probed. Highly active amorphous molybdenum sulfide particles can also be prepared

  13. Atomic layer deposition of aluminum sulfide thin films using trimethylaluminum and hydrogen sulfide

    SciTech Connect

    Sinha, Soumyadeep; Sarkar, Shaibal K.; Mahuli, Neha

    2015-01-15

    Sequential exposures of trimethylaluminum and hydrogen sulfide are used to deposit aluminum sulfide thin films by atomic layer deposition (ALD) in the temperature ranging from 100 to 200 °C. Growth rate of 1.3 Å per ALD cycle is achieved by in-situ quartz crystal microbalance measurements. It is found that the growth rate per ALD cycle is highly dependent on the purging time between the two precursors. Increased purge time results in higher growth rate. Surface limited chemistry during each ALD half cycle is studied by in-situ Fourier transformed infrared vibration spectroscopy. Time of flight secondary ion-mass spectroscopy measurement is used to confirm elemental composition of the deposited films.

  14. Banded sulfide-magnetite ores of Mauk copper massive sulfide deposit, Central Urals: Composition and genesis

    NASA Astrophysics Data System (ADS)

    Safina, N. P.; Maslennikov, V. V.; Maslennikova, S. P.; Kotlyarov, V. A.; Danyushevsky, L. V.; Large, R. R.; Blinov, I. A.

    2015-05-01

    The results of investigation of metamorphosed sulfide-magnetite ores from the Mauk deposit located within the Main Ural Fault at the junction of Tagil and Magnitogorsk massive sulfide zones are discussed. The ore-hosting sequence comprises metamorphic rocks formed from basalt, carbonaceous and carbonaceous-cherty siltstone, and lenticular serpentinized ultramafic bodies. The ores of the deposit are represented by banded varieties and less frequent breccia. The clastic origin of the banded ore is indicated by load casts at the bottom of sulfide beds, alternation of sulfide and barren beds, and the truncation of the growth zones of pyrite crystals. Pyrite, pyrrhotite, chalcopyrite, sphalerite, and magnetite are the major minerals of the banded ores. The internal structure of the listed minerals testifies to the deep metamorphic recrystallization of primary hydrothermal-sedimentary ores accompanied with deformation. Cubanite, pyrrhotite, mackinawite, greigite, and gold are enclosed in metacrysts of pyrite, magnetite, and chalcopyrite. The accessory minerals of the Pb-Bi-Te, Bi-Te, and Ag-Te systems as well as uraninite have been found at the Mauk deposit for the first time. Magnetite predominantly replaces pyrite and less frequently chalcopyrite, pyrrhotite, and gangue minerals. It was established that the major carriers of As and Co are crystals of metamorphic pyrite. Chalcopyrite is the major carrier of Zn, Sn, Te, Pb, Bi, and Ag. Admixture of Fe and Cu is typical of sphalerite, and Se and Ni are characteristic of pyrrhotite. Ti, V, Mn, Sb, As, Ba, and U are concentrated in magnetite. The banded ores of the Mauk deposit are suggested as having been transformed in several stages: diagenesis, anadiagenesis, epidiagenesis ( t < 300°C), and amphibolite facies metamorphism ( t > 500°C).

  15. Nickeliferous sulfides in xenoliths, olivine megacrysts and basaltic glass

    NASA Astrophysics Data System (ADS)

    Fleet, Michael E.; Stone, William E.

    1990-11-01

    The composition of olivine and nickeliferous sulfide inclusions from a selection of mafic and ultramafre rocks, xenoliths and megacrysts, including picritic basalts from Kilauea Volcano, Hawaii, kimberlite from Fayette County, Pennsylvania, and megacrysts from Mount Shasta, California are compared with the mean experimental value of the distribution coefficient for Ni/Fe exchange (KD3=32). Only nine of the forty five olivipe/bulk-sulfide pairs investigated have compositions consistent with equilibration at high temperature, yielding calculated KD3 values in the range 22 to 41. The remaining pairs have calculated KD3 values which range from 0 to 19. Bulk-sulfides in disequilibrated assem-blages are consistently depleted in nickel and within both indivudual associations and individual petrographic sections they exhibit a wide variation in NiS content. The bulk copper contents of olivine-and groundmass-hosted sulfides from Kilauea Volcano range from 0.5 to 43 at%, and samples from the Kilauea Iki lava lake are more Fe-and Cu-rich and generally have lower KD3 values than those from the eruption itself. As with magmatic Ni-Cu sulfide deposits, most nickeliferous sulfide inclusions in mantle-related rocks and xenoliths and in volcanic rocks do not have pristine early-magmatic bulk compositions, and it would seem to be premature to attribute these sulfides solely to either a mantle or an early-magnatic origin.

  16. [Oxidation of sulfide minerals by Thiobacillus ferrooxidans].

    PubMed

    Malakhova, P T; Chebotarev, G M; Kovalenko, E V; Volkov, Iu A

    1981-01-01

    Samples of natural pyrites and sphalerites were subjected to the action of the mineral medium 9K with 1 g of Fe3+ per litre in the presence and in the absence of Thiobacillus ferrooxidans, and incubated at 28 degrees C under the stationary conditions for 30 days. The chemical composition of the solutions was studied after leaching as well as changes of the surfaces of monoliths. The deepest etching of surfaces with the formation of crusts and films of jarosite, limonite and goslarite occurs upon the combined action of bacteria and Fe3+ in regions of a fine-zonal structure enriched with an isomorphous arsenic admixture which are characterized by a defective weak structure. The pyrite and sphalerite from Charmitan with a higher arsenic and iron content were leached more than the pyrite and sphalerite from Kurgashincan. This was also corroborated by chemical analyses of leaching solutions and by monometric studies of crushed sulfide samples. PMID:7219212

  17. Structure of 4-methylpyridinium Hydrogen Sulfide

    NASA Technical Reports Server (NTRS)

    Andras, Maria T.; Hepp, Aloysius F.; Fanwick, Phillip E.; Martuch, Robert A.; Duraj, Stan A.; Gordon, Edward M.

    1994-01-01

    4-Methylpyridinium hydrogen sulfide, (C6H7NH)HS, M(sub r) = 127.21, consists of C6H7NH(+) cations and HS(-) anions. Z = 2 for the crystal with monoclinic space group Cm (#8), dimensions of a = 8.679(2) A, b = 7.964(1) A, and c = 4.860(2) A, an angle beta of 101.10(2) degrees, and a volume of V = 329.6(3) A(exp 3). R = 0.039 and R(sub w) = 0.048 for 385 reflections with F(sub o)(exp 2) greater than 3 sigma(F(sub o)(exp 2)) and 59 variables. Both the C6H7NH(+) cation and the HS(-) anion lie on crystallographic mirror planes with the N,S, two carbon atoms, and two hydrogen atoms positioned in the planes. The hydrogen atom of the HS(-) anion was not located.

  18. Interactions among sulfide-oxidizing bacteria

    NASA Technical Reports Server (NTRS)

    Poplawski, R.

    1985-01-01

    The responses of different phototrophic bacteria in a competitive experimental system are studied, one in which primary factors such as H2S or light limited photometabolism. Two different types of bacteria shared one limited source of sulfide under specific conditions of light. The selection of a purple and a green sulfur bacteria and the cyanobacterium was based on their physiological similarity and also on the fact that they occur together in microbial mats. They all share anoxygenic photosynthesis, and are thus probably part of an evolutionary continuum of phototrophic organisms that runs from, strictly anaerobic physiology to the ability of some cyanobacteria to shift between anoxygenic bacterial style photosynthesis and the oxygenic kind typical of eukaryotes.

  19. Signaling of hydrogen sulfide and polysulfides.

    PubMed

    Kimura, Hideo

    2015-02-10

    It has been almost two decades since the first demonstration of hydrogen sulfide (H2S) as a physiological mediator of cognitive function and vascular tone. H2S is physiologically important because it protects various organs from ischemia-reperfusion injury besides regulating inflammation, oxygen sensing, cell growth, and senescence. The production, metabolism, and regulation of H2S have been studied extensively. H2S modulates target proteins through sulfhydration (or sulfuration) or by the reduction of cysteine disulfide bonds. A large number of novel H2S-donating compounds are being developed owing to the therapeutic potential of H2S. Recently, polysulfides, rather than H2S, have been identified as molecules that sulfhydrate (or sulfurate) their target proteins.

  20. Reactively evaporated films of copper molybdenum sulfide

    NASA Technical Reports Server (NTRS)

    Chi, K. C.; Dillon, R. O.; Bunshah, R. F.; Alterovitz, S.; Woollam, J. A.

    1978-01-01

    Films of superconducting Chevrel-phase copper molybdenum sulfide CuxMo6S8 were deposited on sapphire substrates by reactive evaporation using H2S as the reacting gas. Two superconducting temperatures (10.0 K and 5.0 K) of the films were found, corresponding to two different phases with different copper concentrations. All films were superconducting above 4.2 K and contained Chevrel-phase compound as well as free molybdenum. The critical current was measured as a function of applied field. One sample was found to deviate from the scaling law found for co-evaporated or sputtered samples, which possibly indicates a different pinning mechanism or inhomogeneity of the sample.

  1. [Oxidation of sulfide minerals by Thiobacillus ferrooxidans].

    PubMed

    Malakhova, P T; Chebotarev, G M; Kovalenko, E V; Volkov, Iu A

    1981-01-01

    Samples of natural pyrites and sphalerites were subjected to the action of the mineral medium 9K with 1 g of Fe3+ per litre in the presence and in the absence of Thiobacillus ferrooxidans, and incubated at 28 degrees C under the stationary conditions for 30 days. The chemical composition of the solutions was studied after leaching as well as changes of the surfaces of monoliths. The deepest etching of surfaces with the formation of crusts and films of jarosite, limonite and goslarite occurs upon the combined action of bacteria and Fe3+ in regions of a fine-zonal structure enriched with an isomorphous arsenic admixture which are characterized by a defective weak structure. The pyrite and sphalerite from Charmitan with a higher arsenic and iron content were leached more than the pyrite and sphalerite from Kurgashincan. This was also corroborated by chemical analyses of leaching solutions and by monometric studies of crushed sulfide samples.

  2. Bioextraction of cobalt from complex metal sulfides

    SciTech Connect

    Thompson, D.L.; Noah, K.S.; Wichlacz, P.L.; Torma, A.E.

    1993-05-01

    The present study has investigated the bioleachability of naturally occurring cobaltite and synthetic cobalt sulfides using 29 pedigree and ``wild type`` strains of Thiobacillus ferrooxidans. On the basis of a screening test, five strains of bacteria were selected for assessing the effects of leach parameters (pH, ferrous and ferric sulfates, ammonium sulfate, bipotassium hydrogen phosphate, and substrate concentrations) on cobalt extraction from Blackbird Mine ore and concentrate. The mechanisms of cobalt extraction were explained in terms of direct and indirect modes of bacterial activity, and the chemistry involved in these processes was identified. Using various size fractions of a high-grade cobaltite, the kinetic parameters of cobalt extraction were derived for the effect of specific surface area to be V{sub m} = 376 mg dm{sup {minus}3} h{sup {minus}1} and K 1.27 m{sup 2} g{sup {minus}1}.

  3. Bioextraction of cobalt from complex metal sulfides

    SciTech Connect

    Thompson, D.L.; Noah, K.S.; Wichlacz, P.L.; Torma, A.E.

    1993-01-01

    The present study has investigated the bioleachability of naturally occurring cobaltite and synthetic cobalt sulfides using 29 pedigree and wild type'' strains of Thiobacillus ferrooxidans. On the basis of a screening test, five strains of bacteria were selected for assessing the effects of leach parameters (pH, ferrous and ferric sulfates, ammonium sulfate, bipotassium hydrogen phosphate, and substrate concentrations) on cobalt extraction from Blackbird Mine ore and concentrate. The mechanisms of cobalt extraction were explained in terms of direct and indirect modes of bacterial activity, and the chemistry involved in these processes was identified. Using various size fractions of a high-grade cobaltite, the kinetic parameters of cobalt extraction were derived for the effect of specific surface area to be V[sub m] = 376 mg dm[sup [minus]3] h[sup [minus]1] and K 1.27 m[sup 2] g[sup [minus]1].

  4. Chemical Foundations of Hydrogen Sulfide Biology

    PubMed Central

    Li, Qian; Lancaster, Jack R.

    2013-01-01

    Following nitric oxide (nitrogen monoxide) and carbon monoxide, hydrogen sulfide (or its newer systematic name sulfane, H2S) became the third small molecule that can be both toxic and beneficial depending on the concentration. In spite of its impressive therapeutic potential, the underlying mechanisms for its beneficial effects remain unclear. Any novel mechanism has to obey fundamental chemical principles. H2S chemistry was studied long before its biological relevance was discovered, however, with a few exceptions, these past works have received relatively little attention in the path of exploring the mechanistic conundrum of H2S biological functions. This review calls attention to the basic physical and chemical properties of H2S, focuses on the chemistry between H2S and its three potential biological targets: oxidants, metals and thiol derivatives, discusses the applications of these basics into H2S biology and methodology, and introduces the standard terminology to this youthful field. PMID:23850631

  5. Hydrogen sulfide and polysulfides as signaling molecules

    PubMed Central

    KIMURA, Hideo

    2015-01-01

    Hydrogen sulfide (H2S) is a familiar toxic gas that smells of rotten eggs. After the identification of endogenous H2S in the mammalian brain two decades ago, studies of this molecule uncovered physiological roles in processes such as neuromodulation, vascular tone regulation, cytoprotection against oxidative stress, angiogenesis, anti-inflammation, and oxygen sensing. Enzymes that produce H2S, such as cystathionine β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase have been studied intensively and well characterized. Polysulfides, which have a higher number of inner sulfur atoms than that in H2S, were recently identified as potential signaling molecules that can activate ion channels, transcription factors, and tumor suppressors with greater potency than that of H2S. This article focuses on our contribution to the discovery of these molecules and their metabolic pathways and mechanisms of action. PMID:25864468

  6. Atmospheric carbonyl sulfide exchange in bog microcosms

    SciTech Connect

    Fried, A.; Klinger, L.F.; Erickson, D.J. III )

    1993-01-22

    Measurements of Carbonyl sulfide (OCS) fluxes were carried out on bog microcosms using chamber sampling and tunable diode laser analysis. Intact bog microcosms (vascular plants, mosses, and peat) removed ambient levels of OCS in the light and dark with rates from [minus]2.4 to [minus]8.1 ng S min[sup [minus]1] m[sup [minus]2]. Peat and peat plus mosses emitted OCS in the light with rates of 17.4 and 10.9 ng S min[sup [minus]1] m[sup [minus]2], respectively. In the dark, the mosses apparently removed OCS at a rate equivalent to the peat emissions. A 3-D numerical tracer model using this data indicated that boreal bog ecosystems remove at most 1% of ambient OCS, not sufficient to account for an observed OCS depletion in boreal air masses. 13 refs., 1 fig., 1 tab.

  7. Colloidal Synthesis of Hollow Cobalt Sulfide Nanocrystals

    SciTech Connect

    Yin, Yadong; Erdonmez, Can K.; Cabot, Andreu; Hughes, Steven; Alivisatos, A. Paul

    2006-03-16

    Formation of cobalt sulfide hollow nanocrystals through amechanism similar to the Kirkendall Effect has been investigated indetail. It was found that performing the reaction at>120oC leads tofast formation of a single void ins ide each shell, whereas at roomtemperature multiple voids are formed within each shell, which can beattributed to strongly temperature-dependent diffusivities for vacancies.The void formation process is dominated by outward diffusion of cobaltcations; still, significant inward transport of sulfur anions can beinferred to occur as the final voids are smaller in diameter than theoriginal cobalt nanocrystals. Comparison of volume distributions forinitial and final nanostructures indicates excess apparent volume inshells implying significant porosity and/or a defective structure.Indirect evidence for shells to fracture during growth at lowertemperatures was observed in shell size statisticsand TEM of as-grownshells. An idealized model of the diffusional process imposes two minimalrequirements on material parameters for shell growth to be obtainablewithin a specific synthetic system.

  8. A fast response hafnium selective polymeric membrane electrode based on N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine as a neutral carrier.

    PubMed

    Rezaei, B; Meghdadi, S; Zarandi, R Fazel

    2008-08-30

    In this study a new hafnium selective sensor was fabricated from polyvinylchloride (PVC) matrix membrane containing neutral carrier N,N'-bis(alpha-methyl-salicylidene)-dipropylenetriamine (Mesaldpt) as a new ionophore, sodium tetraphenyl borate (NaTPB) as anionic discriminator and dioctyl phthalate (DOP) as plasticizing solvent mediator in tetrahydrofuran solvent. The electrode exhibits Nernstian response for Hf(4+) (Hafnium(IV)) over a wide concentration range (2.0 x 10(-7) to 1.0 x 10(-1)M) with the determination coefficient of 0.9966 and slope of 15.1+/-0.1 mVdecades(-1). The limit of detection is 1.9 x 10(-7)M. The electrode has a fast response time of 18s and a working pH range of 4-8. The proposed membrane shows excellent discriminating ability towards Hf(4+) ion with regard to several alkali, alkaline earth transition and heavy metal ions. It can be used over a period of 1.5 months with good reproducibility. It is successfully applied for direct determination of Hf(4+) in solutions by standard addition method for real sample analysis.

  9. Tracing the history of submarine hydrothermal inputs and the significance of hydrothermal hafnium for the seawater budget - A combined Pb-Hf-Nd isotope approach

    USGS Publications Warehouse

    van de Flierdt, T.; Frank, M.; Halliday, A.N.; Hein, J.R.; Hattendorf, B.; Gunther, D.; Kubik, P.W.

    2004-01-01

    Secular variations in the Pb isotopic composition of a mixed hydrogenous-hydrothermal ferromanganese crust from the Bauer Basin in the eastern Equatorial Pacific provide clear evidence for changes in hydrothermal contributions during the past 7 Myr. The nearby Galapagos Rise spreading center provided a strong hydrothermal flux prior to 6.5 Ma. After 6.5 Ma, the Pb became stepwise more radiogenic and more similar to Equatorial Pacific seawater, reflecting the westward shift of spreading to the presently active East Pacific Rise (EPR). A second, previously unrecognized enhanced hydrothermal period occurred between 4.4 and 2.9 Ma, which reflects either off-axis hydrothermal activity in the Bauer Basin or a late-stage pulse of hydrothermal Pb from the then active, but waning Galapagos Rise spreading center. Hafnium isotope time-series of the same mixed hydrogenous-hydrothermal crust show invariant values over the past 7 Myr. Hafnium isotope ratios, as well as Nd isotope ratios obtained for this crust, are identical to that of hydrogenous Equatorial Pacific deep water crusts and clearly indicate that hydrothermal Hf, similar to Nd, does not travel far from submarine vents. Therefore, we suggest that hydrothermal Hf fluxes do not contribute significantly to the global marine Hf budget. ?? 2004 Elsevier B.V. All rights reserved.

  10. Sulfide capacities of MnO-SiO2 slags

    NASA Astrophysics Data System (ADS)

    Reddy, Ramana G.; Blander, Milton

    1989-04-01

    Sulfide capacities of binary MnO-SiO2 slags at 1773 and 1923 K were calculated thermodynamically. Only known data, such as the standard free energy of formation of MnO and MnS and activities of MnO in the melt, are used in making calculations based on fundamental concepts. Excellent agreement is found between our calculations and published experimental data. Correlations of sulfide capacities, based on optical basicity using Pauling electronegativities or empirically deduced optical basicities, differ from the experimental data in both magnitude and concentration dependence. Our method provides useful predictions of sulfide capacities a priori.

  11. Hydrogen and sulfur recovery from hydrogen sulfide wastes

    DOEpatents

    Harkness, John B. L.; Gorski, Anthony J.; Daniels, Edward J.

    1993-01-01

    A process for generating hydrogen and elemental sulfur from hydrogen sulfide waste in which the hydrogen sulfide is associated under plasma conditions and a portion of the hydrogen output is used in a catalytic reduction unit to convert sulfur-containing impurities to hydrogen sulfide for recycle, the process also including the addition of an ionizing gas such as argon to initiate the plasma reaction at lower energy, a preheater for the input to the reactor and an internal adjustable choke in the reactor for enhanced coupling with the microwave energy input.

  12. Hydrogen and sulfur recovery from hydrogen sulfide wastes

    DOEpatents

    Harkness, J.B.L.; Gorski, A.J.; Daniels, E.J.

    1993-05-18

    A process is described for generating hydrogen and elemental sulfur from hydrogen sulfide waste in which the hydrogen sulfide is [dis]associated under plasma conditions and a portion of the hydrogen output is used in a catalytic reduction unit to convert sulfur-containing impurities to hydrogen sulfide for recycle, the process also including the addition of an ionizing gas such as argon to initiate the plasma reaction at lower energy, a preheater for the input to the reactor and an internal adjustable choke in the reactor for enhanced coupling with the microwave energy input.

  13. Integrated thin film cadmium sulfide solar cell module

    NASA Technical Reports Server (NTRS)

    Mickelsen, R. A.; Abbott, D. D.

    1971-01-01

    The design, development, fabrication and tests of flexible integrated thin-film cadmium sulfide solar cells and modules are discussed. The development of low cost and high production rate methods for interconnecting cells into large solar arrays is described. Chromium thin films were applied extensively in the deposited cell structures as a means to: (1) achieve high adherence between the cadmium sulfide films and the vacuum-metallized copper substrates, (2) obtain an ohmic contact to the cadmium sulfide films, and (3) improve the adherence of gold films as grids or contact areas.

  14. Removal of sulfur fumes by metal sulfide sorbents.

    PubMed

    Chung, Jae Bin; Ziang, Zhidong; Chung, Jong Shik

    2002-07-01

    Removal of sulfur by a transition metal is studied at temperatures of 300-350 degrees C. Among various metal sulfides tested, only metal sulfides of iron, cobalt, and nickel can remove sulfur fumes as they are transformed into disulfides in the presence of sulfur vapor. The disulfide form can be regenerated into FeS, Co9S8, and Ni3S2, respectively, using hydrogen gas at 350-400 degrees C. These two reactions of deep sulfidation with sulfur and reduction with hydrogen can be utilized for the removal of sulfur fumes in a process stream and an emission gas.

  15. Optimization of the superconducting phase of hydrogen sulfide

    SciTech Connect

    Degtyarenko, N. N.; Masur, E. A.

    2015-12-15

    The electron and phonon spectra, as well as the densities of electron and phonon states of the SH{sub 3} phase and the stable orthorhombic structure of hydrogen sulfide SH{sub 2}, are calculated for the pressure interval 100–225 GPa. It is found that the I4/mmm phase can be responsible for the superconducting properties of metallic hydrogen sulfide along with the SH{sub 3} phase. Sequential stages for obtaining and conservation of the SH{sub 2} phase are proposed. The properties of two (SH{sub 2} and SH{sub 3}) superconducting phases of hydrogen sulfide are compared.

  16. Anodic oxidation of sulfide ions in molten lithium fluoride

    SciTech Connect

    Lloyd, C.L.; Gilbert, J.B. II . Applied Research Lab.)

    1994-10-01

    The study of sulfur and sulfide oxidation in molten salt systems is of current interest in high energy battery, and metallurgical applications. Cyclic voltammetry experiments have been performed on lithium sulfide in a lithium fluoride electrolyte at 1,161 K using a graphite working electrode and a platinum quasi-reference electrode. Two distinct oxidation mechanisms are observed for the sulfide ions. The first oxidation produces sulfur and at a higher potential a disulfide species is proposed to have formed. Both oxidations appear to be reversible and diffusion controlled.

  17. Use of sulfide-containing liquors for removing mercury from flue gases

    DOEpatents

    Nolan, Paul S.; Downs, William; Bailey, Ralph T.; Vecci, Stanley J.

    2003-01-01

    A method and apparatus for reducing and removing mercury in industrial gases, such as a flue gas, produced by the combustion of fossil fuels, such as coal, adds sulfide ions to the flue gas as it passes through a scrubber. Ideally, the source of these sulfide ions may include at least one of: sulfidic waste water, kraft caustic liquor, kraft carbonate liquor, potassium sulfide, sodium sulfide, and thioacetamide. The sulfide ion source is introduced into the scrubbing liquor as an aqueous sulfide species. The scrubber may be either a wet or dry scrubber for flue gas desulfurization systems.

  18. Use of sulfide-containing liquors for removing mercury from flue gases

    DOEpatents

    Nolan, Paul S.; Downs, William; Bailey, Ralph T.; Vecci, Stanley J.

    2006-05-02

    A method and apparatus for reducing and removing mercury in industrial gases, such as a flue gas, produced by the combustion of fossil fuels, such as coal, adds sulfide ions to the flue gas as it passes through a scrubber. Ideally, the source of these sulfide ions may include at least one of: sulfidic waste water, kraft caustic liquor, kraft carbonate liquor, potassium sulfide, sodium sulfide, and thioacetamide. The sulfide ion source is introduced into the scrubbing liquor as an aqueous sulfide species. The scrubber may be either a wet or dry scrubber for flue gas desulfurization systems.

  19. Micro-aeration for hydrogen sulfide removal from biogas

    NASA Astrophysics Data System (ADS)

    Duangmanee, Thanapong

    The presence of sulfur compounds (e.g. protein, sulfate, thiosulfate, sulfite, etc.) in the feed stream generates highly corrosive and odorous hydrogen sulfide during anaerobic digestion. The high sulfide level in the biogas stream is not only poisonous to many novel metal catalysts employed in thermo-catalytic processes but also reduces the quality of methane to produce renewable energy. This study used an innovative, low-maintenance, low-cost biological sulfide removal technology to remove sulfides simultaneously from both gas and liquid phase. ORP (Oxidation-Reduction-Potential) was used as the controlling parameter to precisely regulate air injection to the sulfide oxidizing unit (SOU). The microaeration technique provided just enough oxygen to partially oxidize sulfides to elemental sulfur without inhibiting methanogenesis. The SOU was equipped with a diffuser at the bottom for the dispersion of sulfide-laden biogas and injected air throughout the column. The SOU can be operated as a standalone unit or coupled with an anaerobic digester to simultaneously remove sulfide from the biogas and effluent. The integrated system was capable of reducing hydrogen sulfide in biogas from 2,450 to less than 2 ppmV with minimal sulfate production at the highest available sulfide loading rate of 0.24 kg/m3-day. More than 98% of sulfide removed was recovered as elemental sulfur. However, the standalone SOU was able to operate at high hydrogen sulfide loading of 1.46 kg/m 3-day at inlet sulfide concentration of 3000 ppmV and reduce the off-gas hydrogen sulfide concentrations to less than 10 ppmV. The experiment also revealed that the ORP controlled aeration was sensitive enough to prevent oxygen overdosing (dampening effect) during unexpected surges of aeration. Using generalized linear regression, a model predicting output H2S concentration based on input H2S concentrations, SOU medium heights, and biogas flow rates, was derived. With 95% confidence, output H2S concentration

  20. Enhanced Mantle Conductivity from Sulfides beneath the Sierra Nevada?

    NASA Astrophysics Data System (ADS)

    Park, S. K.

    2002-12-01

    A region of enhanced mantle conductivity (0.03-0.1 S/m) beneath the southern Sierra Nevada, where elevations of over 4000 m are found, has been attributed previously to 3-5% basaltic melt (Park et al., 1996) and to a mix of basaltic and sulfide melt (Ducea and Park, 2000). Because the sulfide melt is assumed to have similar conductivities to its solid counterpart (10,000 S/m), very small amounts (< 0.1%) of sulfide are needed in order to reduce the bulk conductivity from matrix values of about 0.003 S/m or even that of the matrix-basalt melt mix to the values observed. Basaltic melt percentages of less than 1% are needed in the presence of ~0.1% sulfide melt in order to match the observed mantle values. Xenoliths from the Holocene basalts in the Big Pine Volcanic Field contain 0.06-0.4% sulfide, so the estimated values are reasonable. Given the lack of evidence for volumetrically extensive, young (< 10 Ma) basaltic volcanism, calculated residence times of approximately 100 Ka for 3-5% partial melt, the short (about 300 Ka) times needed to develop connected pathways for the basalt, and the young extension of the adjacent Basin and Range province, a mixed melt with both basalt and sulfides seems more reasonable. This conclusion presupposes that the sulfide melt is somehow interconnected in the mantle. Models in which the matrix, the basaltic melt, and the sulfide melt each form interconnected, interlaced networks leads to much higher predictions of mantle conductivity; the sulfide melt fraction must be discontinuous in order to lower bulk conductivity. Petrological studies of sulfide-silicate systems confirm this conclusion; sulfide melts form isolated blebs on the surfaces of olivine within interconnected basaltic melt channels (Holzheid et al., 2000). Simple series-parallel models of ~1% continuous basaltic melt and ~0.01% discontinuous sulfide melt provide bulk conductivities comparable to the observed mantle values. More complicated equivalent media and Hashin

  1. Sulfiding of cobalt molybdate catalysts: characterization by Raman spectroscopy

    SciTech Connect

    Schrader, G.L.; Cheng, C.P.

    1984-02-01

    In situ laser Raman spectroscopic studies of the sulfiding of cobalt molybdate hydrodesulfurization catalysts were performed. Sulfiding in 10% H/sub 2/S/H/sub 2/ at 400/sup 0/C resulted in the formation of stable MoS/sub 2/ structures after 2h. However, the Raman spectra indicated that small crystallites or surface layers of perhaps distorted MoS/sub 2/ were present. Stepwise sulfiding of samples to 150, 250, and 350/sup 0/C permitted intermediate stages of sulfiding to be examined. Differences were observed for the relative rates of reduction versus sulfur incorporation for CoMoO/sub 4/, Co/sub 3/O/sub 4/, MoO/sub 3/, and aggregated or polymeric molybdate phases. Cobalt tended to increase the extent of reduction of the catalyst. A previously described model is extended to include the role of cobalt.

  2. A Combinatorial Approach to Determine Mechanisms of Atmospheric Copper Sulfidation

    SciTech Connect

    BARBOUR,J. CHARLES; BRAITHWAITE,JEFFREY W.; COPELAND,ROBERT GUILD; DUNN,ROBERTO G.; MINOR,KENNETH G.; MISSERT,NANCY A.; NELSON,JEFFREY S.; SULLIVAN,JOHN P.

    1999-10-07

    Parallel microscopic experimentation (the combinatorial approach often used in solid-state science) was applied to characterize atmospheric copper corrosion behavior. Specifically, this technique permitted relative sulfidation rates to be determined for copper containing different levels of point defects and impurities (In, Al, O, and D). Corrosion studies are inherently difficult because of complex interactions between material interfaces and the environment. The combinatorial approach was demonstrated using micron-scale Cu lines that were exposed to a humid air environment containing sub-ppm levels of H{sub 2}S. The relative rate of Cu{sub 2}S growth was determined by measuring the change in resistance of the line. The data suggest that vacancy trapping by In and Al impurities slow the sulfidation rate. Increased sulfidation rates were found for samples containing excess point defects or deuterium. Furthermore, the sulfidation rate of 14 {micro}m wide Cu lines was increased above that for planar films.

  3. The hydrogen sulfide metabolite trimethylsulfonium is found in human urine

    NASA Astrophysics Data System (ADS)

    Lajin, Bassam; Francesconi, Kevin A.

    2016-06-01

    Hydrogen sulfide is the third and most recently discovered gaseous signaling molecule following nitric oxide and carbon monoxide, playing important roles both in normal physiological conditions and disease progression. The trimethylsulfonium ion (TMS) can result from successive methylation reactions of hydrogen sulfide. No report exists so far about the presence or quantities of TMS in human urine. We developed a method for determining TMS in urine using liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-QQQ), and applied the method to establish the urinary levels of TMS in a group of human volunteers. The measured urinary levels of TMS were in the nanomolar range, which is commensurate with the steady-state tissue concentrations of hydrogen sulfide previously reported in the literature. The developed method can be used in future studies for the quantification of urinary TMS as a potential biomarker for hydrogen sulfide body pools.

  4. Micro-PIXE Analysis of Trace Elements in Sulfides

    SciTech Connect

    Hickmott, D.D.; Wetteland, C.; Stimac, J.; Larocque, A.C.L.; Brearley, A.

    2003-08-26

    Micro-scale Proton-induced X-ray Emission (PIXE) of trace elements (TE) in sulfides provides insights into geologic processes including magmatic system evolution, ore forming events, and fluid-flow processes. The Los Alamos nuclear microprobe was used to determine TE concentrations and ratios in sulfides from diverse geologic environments including hydrothermal ore deposits, coal seams, and metamorphic rocks. Pyrrhotite (Po) from silicic volcanics contains high Cu and Ni; Po from the Clear Lake volcanic field has higher Mo than does Po from other volcanic fields. Coal pyrites contain high Cu, As, Se, Mo and Pb, and show high As/Se and Mo/Se in marine influenced sulfides from the Lower Kittanning coal, but not in other marine-influenced coals. Sulfides are amenable to micro-PIXE studies because of the difficulties in obtaining the homogeneous standards required for many other TE microanalytical techniques.

  5. An Experiment in Autotrophic Fermentation: Microbial Oxidation of Hydrogen Sulfide.

    ERIC Educational Resources Information Center

    Sublette, Kerry L.

    1989-01-01

    Described is an experiment which uses an autotrophic bacterium to anaerobically oxidize hydrogen sulfide to sulfate in a batch-stirred tank reactor. Discusses background information, experimental procedure, and sample results of this activity. (CW)

  6. 21 CFR 177.2490 - Polyphenylene sulfide resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... specifications as determined by methods titled “Oxygen Flask Combustion-Gravimetric Method for Determination of... “Analysis for Dichlorobenzene in Ryton Polyphenylene Sulfide,” which are incorporated by reference....

  7. 21 CFR 177.2490 - Polyphenylene sulfide resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... specifications as determined by methods titled “Oxygen Flask Combustion-Gravimetric Method for Determination of... “Analysis for Dichlorobenzene in Ryton Polyphenylene Sulfide,” which are incorporated by reference....

  8. 21 CFR 177.2490 - Polyphenylene sulfide resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... titled “Oxygen Flask Combustion-Gravimetric Method for Determination of Sulfur in Organic Compounds,” “Determination of the Inherent Viscosity of Polyphenylene Sulfide,” and “Analysis for Dichlorobenzene in...

  9. Optimization of biological sulfide removal in a CSTR bioreactor.

    PubMed

    Roosta, Aliakbar; Jahanmiri, Abdolhossein; Mowla, Dariush; Niazi, Ali; Sotoodeh, Hamidreza

    2012-08-01

    In this study, biological sulfide removal from natural gas in a continuous bioreactor is investigated for estimation of the optimal operational parameters. According to the carried out reactions, sulfide can be converted to elemental sulfur, sulfate, thiosulfate, and polysulfide, of which elemental sulfur is the desired product. A mathematical model is developed and was used for investigation of the effect of various parameters on elemental sulfur selectivity. The results of the simulation show that elemental sulfur selectivity is a function of dissolved oxygen, sulfide load, pH, and concentration of bacteria. Optimal parameter values are calculated for maximum elemental sulfur selectivity by using genetic algorithm as an adaptive heuristic search. In the optimal conditions, 87.76% of sulfide loaded to the bioreactor is converted to elemental sulfur.

  10. [Activity of hydrogen sulfide production enzymes in kidneys of rats].

    PubMed

    Mel'nyk, A V; Pentiuk, O O

    2009-01-01

    An experimental research of activity and kinetic descriptions of enzymes participating in formation of hydrogen sulfide in the kidney of rats has been carried out. It was established that cystein, homocystein and thiosulphate are the basic substrates for hydrogen sulfide synthesis. The higest activity for hydrogen sulfide production belongs to thiosulfate-dithiolsulfurtransferase and cysteine aminotransferase, less activity is characteristic of cystathionine beta-synthase and cystathio-nine gamma-lyase. The highest affinity to substrate is registered for thiosulfate-dithiolsulfurtransferase and cystathionine gamma-lyase. It is discovered that the substrate inhibition is typical of all hydrogen sulfide formation enzymes, although this characteristic is the most expressed thiosulfat-dithiolsulfurtransferase. PMID:20387629

  11. 21 CFR 872.1870 - Sulfide detection device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... periodontal pocket probing depths, detect the presence or absence of bleeding on probing, and detect the presence of sulfides in periodontal pockets, as an adjunct in the diagnosis of periodontal diseases...

  12. 21 CFR 872.1870 - Sulfide detection device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... periodontal pocket probing depths, detect the presence or absence of bleeding on probing, and detect the presence of sulfides in periodontal pockets, as an adjunct in the diagnosis of periodontal diseases...

  13. The hydrogen sulfide metabolite trimethylsulfonium is found in human urine

    PubMed Central

    Lajin, Bassam; Francesconi, Kevin A.

    2016-01-01

    Hydrogen sulfide is the third and most recently discovered gaseous signaling molecule following nitric oxide and carbon monoxide, playing important roles both in normal physiological conditions and disease progression. The trimethylsulfonium ion (TMS) can result from successive methylation reactions of hydrogen sulfide. No report exists so far about the presence or quantities of TMS in human urine. We developed a method for determining TMS in urine using liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-QQQ), and applied the method to establish the urinary levels of TMS in a group of human volunteers. The measured urinary levels of TMS were in the nanomolar range, which is commensurate with the steady-state tissue concentrations of hydrogen sulfide previously reported in the literature. The developed method can be used in future studies for the quantification of urinary TMS as a potential biomarker for hydrogen sulfide body pools. PMID:27247020

  14. Azo dye decolorization assisted by chemical and biogenic sulfide.

    PubMed

    Prato-Garcia, Dorian; Cervantes, Francisco J; Buitrón, Germán

    2013-04-15

    The effectiveness of chemical and biogenic sulfide in decolorizing three sulfonated azo dyes and the robustness of a sulfate-reducing process for simultaneous decolorization and sulfate removal were evaluated. The results demonstrated that decolorization of azo dyes assisted by chemical sulfide and anthraquinone-2,6-disulfonate (AQDS) was effective. In the absence of AQDS, biogenic sulfide was more efficient than chemical sulfide for decolorizing the azo dyes. The performance of sulfate-reducing bacteria in attached-growth sequencing batch reactors suggested the absence of competition between the studied azo dyes and the sulfate-reducing process for the reducing equivalents. Additionally, the presence of chemical reduction by-products had an almost negligible effect on the sulfate removal rate, which was nearly constant (94%) after azo dye injection.

  15. Tests show DMSO effective for HDS, HDN catalyst sulfiding

    SciTech Connect

    Christman, R.D.; Plesko, R.W. ); Donahue, M. ); Wilson, R.E. )

    1989-09-18

    This paper describes tests which have shown that dimethyl sulfoxide (DMSO) is an effective agent for sulfiding hydrotreating catalysts. Thus, DMSO can be a suitable replacement for sulfiding agents that have been classified as hazardous substances by the U.S. Environmental Protection Agency (EPA). All of the commonly used sulfur compounds were originally classified by EPA as hazardous chemicals. Gaylord Chemical Corp. has petitioned EPA to remove DMS from the list of hazardous chemicals.

  16. Determination of Hydrogen Sulfide in Fermentation Broths Containing SO21

    PubMed Central

    Acree, T. E.; Sonoff, Elisabeth P.; Splittstoesser, D. F.

    1971-01-01

    A procedure for the determination of hydrogen sulfide in fermentation broths containing up to 100 μg of SO2 per ml is described. The method involves the sparging of H2S from the broth into a cadmium hydroxide absorption solution, the formation of methylene blue from the absorbed sulfide, and the measuring of this color spectrophotometrically. The use of cadmium hydroxide instead of zinc acetate, the common absorbent, substantially reduced the interference of SO2 with the analysis. PMID:5111300

  17. Preparation of mesoporous cadmium sulfide nanoparticles with moderate pore size

    SciTech Connect

    Han Zhaohui Zhu, Huaiyong; Shi, Jeffrey; Parkinson, Gordon; Lu, G.Q.

    2007-03-15

    The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10nm or are well above 100nm.

  18. Petroleum associated with polymetallic sulfide in sediment from Gorda Ridge

    USGS Publications Warehouse

    Kvenvolden, K.A.; Rapp, J.B.; Hostettler, F.D.; Morton, J.L.; King, J.D.; Claypool, G.E.

    1986-01-01

    A sediment sample, impregnated with asphaltic petroleum and polymetallic sulfide, was dredged from the southern end of Gorda Ridge (the Escanaba Trough) off northern California, within the offshore Exclusive Economic Zone of the United States. The molecular distributions of hydrocarbons in this petroleum show that it was probably derived from terrestrial organic matter in turbidite sediment filling the Escanaba Trough. Hydrothermal activity at the Gorda Ridge spreading center provided the heat for petroleum formation and was the source of fluids for sulfide mineralization.

  19. Sulfide catalysts for reducing SO2 to elemental sulfur

    DOEpatents

    Jin, Yun; Yu, Qiquan; Chang, Shih-Ger

    2001-01-01

    A highly efficient sulfide catalyst for reducing sulfur dioxide to elemental sulfur, which maximizes the selectivity of elemental sulfur over byproducts and has a high conversion efficiency. Various feed stream contaminants, such as water vapor are well tolerated. Additionally, hydrogen, carbon monoxide, or hydrogen sulfides can be employed as the reducing gases while maintaining high conversion efficiency. This allows a much wider range of uses and higher level of feed stream contaminants than prior art catalysts.

  20. Process for thin film deposition of cadmium sulfide

    DOEpatents

    Muruska, H. Paul; Sansregret, Joseph L.; Young, Archie R.

    1982-01-01

    The present invention teaches a process for depositing layers of cadmium sulfide. The process includes depositing a layer of cadmium oxide by spray pyrolysis of a cadmium salt in an aqueous or organic solvent. The oxide film is then converted into cadmium sulfide by thermal ion exchange of the O.sup.-2 for S.sup.-2 by annealing the oxide layer in gaseous sulfur at elevated temperatures.

  1. Formation of Dimethyl Sulfide and Methanethiol in Anoxic Freshwater Sediments

    PubMed Central

    Lomans, B. P.; Smolders, A.; Intven, L. M.; Pol, A.; Op, De; Van Der Drift, C.

    1997-01-01

    Concentrations of volatile organic sulfur compounds (VOSC) were measured in water and sediment columns of ditches in a minerotrophic peatland in The Netherlands. VOSC, with methanethiol (4 to 40 nM) as the major compound, appeared to be mainly of sediment origin. Both VOSC and hydrogen sulfide concentrations decreased dramatically towards the water surface. High methanethiol and high dimethyl sulfide concentrations in the sediment and just above the sediment surface coincided with high concentrations of hydrogen sulfide (correlation factors, r = 0.91 and r = 0.81, respectively). Production and degradation of VOSC were studied in 32 sediment slurries collected from various freshwater systems in The Netherlands. Maximal endogenous methanethiol production rates of the sediments tested (up to 1.44 (mu)mol per liter of sediment slurry (middot) day(sup-1)) were determined after inhibition of methanogenic and sulfate-reducing populations in order to stop VOSC degradation. These experiments showed that the production and degradation of VOSC in sediments are well balanced. Statistical analysis revealed multiple relationships of methanethiol production rates with the combination of methane production rates (indicative of total anaerobic mineralization) and hydrogen sulfide concentrations (r = 0.90) or with the combination of methane production rates and the sulfate/iron ratios in the sediment (r = 0.82). These findings and the observed stimulation of methanethiol formation in sediment slurry incubations in which the hydrogen sulfide concentrations were artificially increased provided strong evidence that the anaerobic methylation of hydrogen sulfide is the main mechanism for VOSC formation in most freshwater systems. Methoxylated aromatic compounds are likely a major source of methyl groups for this methylation of hydrogen sulfide, since they are important degradation products of the abundant biopolymer lignin. Increased sulfate concentrations in several freshwater

  2. Deposition, stabilization and characterization of zirconium oxide and hafnium oxide thin films for high k gate dielectrics

    NASA Astrophysics Data System (ADS)

    Gao, Yong

    As the MOS devices continue to scale down in feature size, the gate oxide thickness is approaching the nanometer node. High leakage current densities caused by tunneling is becoming a serious problem. Replacing silicon oxide with a high kappa material as the gate dielectrics is becoming very critical. In recent years, research has been focused on a few promising candidates, such as ZrO2, HfO2, Al2O3, Ta 2O5, and some silicates. However, unary metal oxides tend to crystallize at relatively low temperatures (less than 700°C). Crystallized films usually have a very small grain size and high leakage current due to the grain boundaries. The alternatives are high kappa oxides which are single crystal or amorphous. Silicates remain amorphous at high temperatures, but have some problems such as phase separation, interface reaction, and lower kappa value. In this work, we addressed the crystallization problems of zirconium oxide and hafnium oxide thin films. Both of these two thin films were deposited by DC reactive magnetron sputtering so that very dense films were deposited with little damage. A specially designed system was set up in order to have good control of the deposition process. The crystallization behavior of as-deposited amorphous ZrO2 and HfO2 films was studied. It was found that the films tended to have higher crystallization temperature when the films were thinner than a critical thickness of approximately 5 nm. However, it was still well below 900°C. The crystallization temperature was significantly increased by sandwiching the high kappa oxide layer between two silica layers. Ultra thin HfO2 films of 5nm thickness remained amorphous up to 900°C. This is the highest crystallization temperature which has been reported. The mechanisms for this effect are proposed. Electrical properties of these high kappa dielectric films were also studied. It was found that ultra thin amorphous HfO2 and ZrO 2 films had superior electrical properties to crystalline films

  3. Initiation of a passivated interface between hafnium oxide and In(Ga)As(0 0 1)-(4x2).

    PubMed

    Clemens, Jonathon B; Bishop, Sarah R; Lee, Joon Sung; Kummel, Andrew C; Droopad, Ravi

    2010-06-28

    Hafnium oxide interfaces were studied on two related group III rich semiconductor surfaces, InAs(0 0 1)-(4x2) and In(0.53)Ga(0.47)As(0 0 1)-(4x2), via two different methods: reactive oxidation of deposited Hf metal and electron beam deposition of HfO(2). The interfaces were investigated with scanning tunneling microscopy and spectroscopy (STS). Single Hf atom chemisorption sites were identified that are resistant to oxidation by O(2), but Hf islands are reactive to O(2). After e(-) beam deposition of <1 ML of HfO(2), single chemisorption sites were identified. At low coverage (<1 ML), the n-type and p-type HfO(2)/InGaAs(0 0 1)-(4x2) interfaces show p-type character in STS, which is typical of clean InGaAs(0 0 1)-(4x2). After annealing below 200 degrees C, full coverage HfO(2)/InGaAs(0 0 1)-(4x2) (1-3 ML) has the surface Fermi level shifted toward the conduction band minimum for n-type InGaAs, but near the valence band maximum for p-type InGaAs. This is consistent with the HfO(2)/InGaAs(0 0 1)-(4x2) interface being at least partially unpinned, i.e., a low density of states in the band gap. The partially unpinned interface results from the modest strength of the bonding between HfO(2) and InGaAs(0 0 1)-(4x2) that prevents substrate atom disruption. The fortuitous structure of HfO(2) on InAs(0 0 1)-(4x2) and InGaAs(0 0 1)-(4x2) allows for the elimination of the partially filled dangling bonds on the surface, which are usually responsible for Fermi level pinning.

  4. Initiation of a passivated interface between hafnium oxide and In(Ga)As(0 0 1)-(4x2)

    SciTech Connect

    Clemens, Jonathon B.; Bishop, Sarah R.; Kummel, Andrew C.; Lee, Joon Sung

    2010-06-28

    Hafnium oxide interfaces were studied on two related group III rich semiconductor surfaces, InAs(0 0 1)-(4x2) and In{sub 0.53}Ga{sub 0.47}As(0 0 1)-(4x2), via two different methods: reactive oxidation of deposited Hf metal and electron beam deposition of HfO{sub 2}. The interfaces were investigated with scanning tunneling microscopy and spectroscopy (STS). Single Hf atom chemisorption sites were identified that are resistant to oxidation by O{sub 2}, but Hf islands are reactive to O{sub 2}. After e{sup -} beam deposition of <<1 ML of HfO{sub 2}, single chemisorption sites were identified. At low coverage (<1 ML), the n-type and p-type HfO{sub 2}/InGaAs(0 0 1)-(4x2) interfaces show p-type character in STS, which is typical of clean InGaAs(0 0 1)-(4x2). After annealing below 200 deg. C, full coverage HfO{sub 2}/InGaAs(0 0 1)-(4x2) (1-3 ML) has the surface Fermi level shifted toward the conduction band minimum for n-type InGaAs, but near the valence band maximum for p-type InGaAs. This is consistent with the HfO{sub 2}/InGaAs(0 0 1)-(4x2) interface being at least partially unpinned, i.e., a low density of states in the band gap. The partially unpinned interface results from the modest strength of the bonding between HfO{sub 2} and InGaAs(0 0 1)-(4x2) that prevents substrate atom disruption. The fortuitous structure of HfO{sub 2} on InAs(0 0 1)-(4x2) and InGaAs(0 0 1)-(4x2) allows for the elimination of the partially filled dangling bonds on the surface, which are usually responsible for Fermi level pinning.

  5. Sulfide inhibition of and metabolism by cytochrome c oxidase.

    PubMed

    Nicholls, Peter; Marshall, Doug C; Cooper, Chris E; Wilson, Mike T

    2013-10-01

    Hydrogen sulfide (H2S), a classic cytochrome c oxidase inhibitor, is also an in vitro oxidase substrate and an in vivo candidate hormonal ('gasotransmitter') species affecting sleep and hibernation. H2S, nitric oxide (NO) and carbon monoxide (CO) share some common features. All are low-molecular-mass physiological effectors and also oxidase inhibitors, capable of binding more than one enzyme site, and each is an oxidizable 'substrate'. The oxidase oxidizes CO to CO2, NO to nitrite and sulfide to probable persulfide species. Mitochondrial cytochrome c oxidase in an aerobic steady state with ascorbate and cytochrome c is rapidly inhibited by sulfide in a biphasic manner. At least two successive inhibited species are involved, probably partially reduced. The oxidized enzyme, in the absence of turnover, occurs in at least two forms: the 'pulsed' and 'resting' states. The pulsed form reacts aerobically with sulfide to form two intermediates, 'P' and 'F', otherwise involved in the reaction of oxygen with reduced enzyme. Sulfide can directly reduce the oxygen-reactive a3CuB binuclear centre in the pulsed state. The resting enzyme does not undergo such a step, but only a very slow one-electron reduction of the electron-transferring haem a. In final reactivation phases, both the steady-state inhibition of catalysis and the accumulation of P and F states are reversed by slow sulfide oxidation. A model for this complex reaction pattern is presented. PMID:24059525

  6. Sulfide capacity of high alumina blast furnace slags

    NASA Astrophysics Data System (ADS)

    Shankar, Amitabh; Görnerup, Märten; Seetharaman, S.; Lahiri, A. K.

    2006-12-01

    Sulfide capacities of high alumina blast furnace slags were experimentally determined using the gas-slag equilibration technique. Two different slag systems were considered for the current study, namely, CaO-SiO2-MgO-Al2O3 quaternary and CaO-SiO2-MgO-Al2O3-TiO2 quinary system. The liquid slag was equilibrated with the Ar-CO-CO2-SO2 gas mixture. Experiments were conducted in the temperature range of 1773 to 1873 K. The effects of temperature, basicity, and the MgO and TiO2 contents of slags on sulfide capacity were studied. As expected, sulfide capacity was found to increase with the increase in temperature and basicity. At the higher experimental temperature, titania decreases the sulfide capacity of slag. However, at the lower temperature, there was no significant effect of titania on the sulfide capacity of slag. Sulfide capacity increases with the increase in MgO content of slag if the MgO content is more than 5 pct.

  7. Hydrodenitrogenation of quinoline over carbon-supported transition metal sulfides

    SciTech Connect

    Eijsbouts, S.; De Beer, V.H.J.; Prins, R. )

    1991-02-01

    Transition metal sulfide (TMS) catalysts were prepared by impregnation of an activated carbon support with aqueous solutions of first-, second-, and third-row (group V-VIII) transition metal salts, drying and in situ sulfidation. The catalysts were tested in the hydrodenitrogenation of quinoline (653 K, 5.5 MPa) in microautoclaves and microflow reactors. The first-row transition metal sulfides had low quinoline conversions to hydrocarbons, and their periodic trend formed a U-shaped curve with a minimum at Mn/C and Fe/C and maxima at V/C and Ni/C. The quinoline conversions to hydrocarbons of the second- and third-row TMS formed volcano curves with maxima at Rh/C and Ir/C and with Mo/C and W/C having the lowest conversions. The transition metal sulfide catalysts with a low quinoline hydrogenation (first-row transition metal sulfides, Mo/C and W/C) also had a low quinoline conversion to hydrocarbons. The transition metal sulfides with the highest quinoline conversions to hydrocarbons (Rh/C, Pd/C, Os/C, Ir/C and Pt/C) had a very highquinoline hydrogenation and a high selectivity for propylcyclohexane. Ru/C and especially Re/C had a good quinoline conversion to hydrocarbons, but also an exceptionally high selectivity for propylbenzene.

  8. Sulfide as a soil phytotoxin—a review

    PubMed Central

    Lamers, Leon P. M.; Govers, Laura L.; Janssen, Inge C. J. M.; Geurts, Jeroen J. M.; Van der Welle, Marlies E. W.; Van Katwijk, Marieke M.; Van der Heide, Tjisse; Roelofs, Jan G. M.; Smolders, Alfons J. P.

    2013-01-01

    In wetland soils and underwater sediments of marine, brackish and freshwater systems, the strong phytotoxin sulfide may accumulate as a result of microbial reduction of sulfate during anaerobiosis, its level depending on prevailing edaphic conditions. In this review, we compare an extensive body of literature on phytotoxic effects of this reduced sulfur compound in different ecosystem types, and review the effects of sulfide at multiple ecosystem levels: the ecophysiological functioning of individual plants, plant-microbe associations, and community effects including competition and facilitation interactions. Recent publications on multi-species interactions in the rhizosphere show even more complex mechanisms explaining sulfide resistance. It is concluded that sulfide is a potent phytotoxin, profoundly affecting plant fitness and ecosystem functioning in the full range of wetland types including coastal systems, and at several levels. Traditional toxicity testing including hydroponic approaches generally neglect rhizospheric effects, which makes it difficult to extrapolate results to real ecosystem processes. To explain the differential effects of sulfide at the different organizational levels, profound knowledge about the biogeochemical, plant physiological and ecological rhizosphere processes is vital. This information is even more important, as anthropogenic inputs of sulfur into freshwater ecosystems and organic loads into freshwater and marine systems are still much higher than natural levels, and are steeply increasing in Asia. In addition, higher temperatures as a result of global climate change may lead to higher sulfide production rates in shallow waters. PMID:23885259

  9. Iron sulfide deposits at Wadi Wassat, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Roberts, R.J.; Rossman, D.L.; Bagdady, A.Y.; Conway, C.M.; Helaby, A.M.

    1981-01-01

    Massive and disseminated iron sulfide deposits in Wadi Wassat form lenticular, stratabound deposits in cherty Precambrian sedimentary rocks interlayered with Precambrian calcareous sedimentary rocks, pyroclastic rocks, and andesitic flow rocks. These rocks have been cut by a wide variety of plutonic and dike rocks including gabbro, diorite, granodiorite, diabase, rhyolite, and granite. The zone containing the sulfide lenses is nearly 16 km long and is cut off by granitic rocks at both the northern and southern ends. The lenses are as much as 200 m thick; one can be traced along strike for more than 4 km. The lenses consist mostly of iron sulfides. Pyrite is the principal sulfide mineral; near intrusive bodies the pyrite has been partially converted to pyrrhotite and locally mobilized into fractures. The sulfides have been oxidized to a depth of about 25 m. Preliminary calculations indicate that about 107,500,000 tons of sulfides, averaging 40 percent iron and 35 percent sulfur, are available to a depth of i00 m. Small amounts of nickel, cobalt, zinc, and copper are also present, but at metal prices prevailing in early 1981, these do not constitute significant resources.

  10. Sulfide oxidation in fluidized bed bioreactor using nylon support material.

    PubMed

    Midha, Varsha; Jha, M K; Dey, Apurba

    2012-01-01

    A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 20 m/hr. The effects of upflow velocity, hydraulic retention time and reactor operation time on sulfide oxidation rate were studied using statistical model. Mixed culture obtained from the activated sludge, taken from tannery effluent treatment plant, was used as a source for microorganisms. The diameter and density of the nylon particles were 2-3 mm and 1140 kg/m3, respectively. Experiments were carried out in the reactor at a temperature of (30 +/- 2) degrees C, at a fixed bed height of 16 cm after the formation of biofilm on the surface of support particles. Biofilm thickness reached (42 +/- 3) microm after 15 days from reactor start-up. The sulfide oxidation, sulfate and sulfur formation is examined at all hydraulic retention times and upflow velocities. The results indicated that almost 90%-92% sulfide oxidation was achieved at all hydraulic retention times. Statistical model could explain 94% of the variability and analysis of variance showed that upflow velocity and hydraulic retention time slightly affected the sulfide oxidation rate. The highest sulfide oxidation of 92% with 70% sulfur was obtained at hydraulic retention time of 75 min and upflow velocity of 14 m/hr.

  11. Mobility and bioavailability of trace metals in sulfidic coastal sediments.

    PubMed

    Sundelin, B; Eriksson, A K

    2001-04-01

    High concentrations of Hg, Cd, Pb, Cu, and Zn were found in the euxinic sediment of the inner archipelago of Stockholm. In the sulfide-rich sediment, they are precipitated as metal sulfides with low dissolving capacity and bioavailability. In two experiments, the significance of acid-volatile sulfide (AVS) and dissolved sulfides for mobility, bioavailability, and toxicity of metals were studied by oxygenation of intact sediment cores. Influence of bioturbating deposit-feeding amphipods, that is, Monoporeia affinis, was examined on studied sediment processes. Results showed a low mobility of most metals except Cd and Zn. Bioturbation did not enhance mobility. Cd and Zn, released from the sediment, were not bioaccumulated in amphipods. In contrast, the less mobile metals Hg and Pb were bioaccumulated. A low toxicity of contaminated sediments, in terms of mortality and embryonic malformations of amphipods, was recorded. Results indicate that Cd, Zn, and Cu are comparatively unavailable after oxygenation of the metal sulfides. Similar results were recorded in contaminated sediments differing in redox potential, AVS, dissolved sulfides, and organic contents, suggesting that other metal ligands, in addition to AVS, are important for metal bioavailability and toxicity in anoxic and suboxic environments. PMID:11345449

  12. Metal Sulfides as Sensing Materials for Chemoresistive Gas Sensors

    PubMed Central

    Gaiardo, Andrea; Fabbri, Barbara; Guidi, Vincenzo; Bellutti, Pierluigi; Giberti, Alessio; Gherardi, Sandro; Vanzetti, Lia; Malagù, Cesare; Zonta, Giulia

    2016-01-01

    This work aims at a broad overview of the results obtained with metal-sulfide materials in the field of chemoresistive gas sensing. Indeed, despite the well-known electrical, optical, structural and morphological features previously described in the literature, metal sulfides present lack of investigation for gas sensing applications, a field in which the metal oxides still maintain a leading role owing to their high sensitivity, low cost, small dimensions and simple integration, in spite of the wide assortment of sensing materials. However, despite their great advantages, metal oxides have shown significant drawbacks, which have led to the search for new materials for gas sensing devices. In this work, Cadmium Sulfide and Tin (IV) Sulfide were investigated as functional materials for thick-film chemoresistive gas-sensors fabrication and they were tested both in thermo- and in photo-activation modes. Furthermore, electrical characterization was carried out in order to verify their gas sensing properties and material stability, by comparing the results obtained with metal sulfides to those obtained by using their metal-oxides counterparts. The results highlighted the possibility to use metal sulfides as a novel class of sensing materials, owing to their selectivity to specific compounds, stability, and the possibility to operate at room temperature. PMID:26927120

  13. Metal Sulfides as Sensing Materials for Chemoresistive Gas Sensors.

    PubMed

    Gaiardo, Andrea; Fabbri, Barbara; Guidi, Vincenzo; Bellutti, Pierluigi; Giberti, Alessio; Gherardi, Sandro; Vanzetti, Lia; Malagù, Cesare; Zonta, Giulia

    2016-01-01

    This work aims at a broad overview of the results obtained with metal-sulfide materials in the field of chemoresistive gas sensing. Indeed, despite the well-known electrical, optical, structural and morphological features previously described in the literature, metal sulfides present lack of investigation for gas sensing applications, a field in which the metal oxides still maintain a leading role owing to their high sensitivity, low cost, small dimensions and simple integration, in spite of the wide assortment of sensing materials. However, despite their great advantages, metal oxides have shown significant drawbacks, which have led to the search for new materials for gas sensing devices. In this work, Cadmium Sulfide and Tin (IV) Sulfide were investigated as functional materials for thick-film chemoresistive gas-sensors fabrication and they were tested both in thermo- and in photo-activation modes. Furthermore, electrical characterization was carried out in order to verify their gas sensing properties and material stability, by comparing the results obtained with metal sulfides to those obtained by using their metal-oxides counterparts. The results highlighted the possibility to use metal sulfides as a novel class of sensing materials, owing to their selectivity to specific compounds, stability, and the possibility to operate at room temperature. PMID:26927120

  14. Metal Sulfides as Sensing Materials for Chemoresistive Gas Sensors.

    PubMed

    Gaiardo, Andrea; Fabbri, Barbara; Guidi, Vincenzo; Bellutti, Pierluigi; Giberti, Alessio; Gherardi, Sandro; Vanzetti, Lia; Malagù, Cesare; Zonta, Giulia

    2016-02-26

    This work aims at a broad overview of the results obtained with metal-sulfide materials in the field of chemoresistive gas sensing. Indeed, despite the well-known electrical, optical, structural and morphological features previously described in the literature, metal sulfides present lack of investigation for gas sensing applications, a field in which the metal oxides still maintain a leading role owing to their high sensitivity, low cost, small dimensions and simple integration, in spite of the wide assortment of sensing materials. However, despite their great advantages, metal oxides have shown significant drawbacks, which have led to the search for new materials for gas sensing devices. In this work, Cadmium Sulfide and Tin (IV) Sulfide were investigated as functional materials for thick-film chemoresistive gas-sensors fabrication and they were tested both in thermo- and in photo-activation modes. Furthermore, electrical characterization was carried out in order to verify their gas sensing properties and material stability, by comparing the results obtained with metal sulfides to those obtained by using their metal-oxides counterparts. The results highlighted the possibility to use metal sulfides as a novel class of sensing materials, owing to their selectivity to specific compounds, stability, and the possibility to operate at room temperature.

  15. Dihydrogen Activation by Titanium Sulfide Complexes

    PubMed Central

    Sweeney, Zachary K.; Polse, Jennifer L.; Bergman*, Robert G.; Andersen*, Richard A.

    2005-01-01

    The titanocene sulfido complex Cp*2Ti(S)py (1, Cp* = pentamethylcyclopentadienyl; py = pyridine) is synthesized by addition of a suspension of S8 to a toluene solution of Cp*2Ti-(CH2CH2) (2) and py. The rate of rotation of the pyridine ligand in solution was determined by 1H NMR spectroscopy, and the structure of 1 was determined by X-ray crystallography. Complex 1 reacts reversibly with dihydrogen to give Cp*2Ti(H)SH (6) and py. Reaction of 1 with HD gives an equilibrium mixture of Cp*2Ti(D)SH and Cp*2Ti(H)SD; H2 and D2 are not formed in this reaction. 1D 1H NMR magnetization transfer spectra and 2D EXSY 1H NMR spectra of 6 in the presence of H2 show that in solution the H2, hydride, and hydrosulfido hydrogen atoms exchange. A four-center mechanism for this exchange is proposed. The EXSY studies show that the Ti–H and S–H hydrogens exchange with each other more rapidly than either of those hydrogens exchanges with external H2. A transient dihydrogen complex intermediate is proposed to explain this observation. The infrared spectrum of 6 shows an absorption assigned to the Ti–H stretching mode at 1591 cm−1 that shifts upon deuteration to 1154 cm−1. Reaction of 1 with trimethylsilane, diethylsilane, or dimethylsilane gives Cp*2-Ti(H)SSiMe3 (7), Cp*2Ti(H)SSiHEt2 (8), or Cp*2Ti(H)SSiHMe2 (9), respectively. The isotope effect for the reaction producing 7 has been measured, and a mechanism is proposed. Treatment of 1 with an additional equivalent of S8 results in the formation of the disulfide Cp*2Ti(S2) (4). Acetylene inserts into the Ti–S bond of 4 to produce the vinyl disulfide complex 5. The structures of 4 and 5 have been determined by X-ray diffraction. Compound 4 reacts with 2 in the presence of py to produce 1. Phosphines react with 4 in the presence of H2 to provide 6 and the corresponding phosphine sulfide. Reaction of hydrogen with 4 gives Cp*2-Ti(SH)2 (3). The reactions of 1 and 4 with dihydrogen provide a model for possible mechanisms of H2

  16. Lithium-aluminum/iron sulfide batteries

    NASA Astrophysics Data System (ADS)

    Henriksen, G. L.; Vissers, D. R.

    Lithium-alloy/metal sulfide batteries have been under development at Argonne National Laboratory since 1972. ANL's technology employs a two-phase Li alloy negative electrode, low-melting point LiCl-rich LiCl-LiBr-KBr molten salt electrolyte, and either an FeS or an upper-plateau (UP) FeS 2 positive electrode. These components are assembled in an 'electrolyte-starved' bipolar cell configuration. Use of the multi-phase Li alloy ((α+β)-Li-Al and Li 5Al 5Fe 2) negative electrode provides in situ overcharge tolerance that renders the bipolar design viable. Employing LiCl-rich LiCl-LiBr-KBr electrolyte is 'electrolyte-starved" cells achieves low-burdened cells that possess low area-specific impedance, comparable with that of flooded cells using LiCl-LiBr-KBr eutectic electrolyte. The combination of dense UP FeS 2 electrodes and low-melting electrolyte produces a stable and reversible couple, achieving over 1000 cycles in flooded cells, with high power capabilities. In addition, a new class of stable chalcogenide ceramic/sealant materials was developed. These materials produce high-strength bonds between a variety of metals and ceramics, which make fabrication of lithium/iron sulfide bipolar stacks practical. Bipolar Li-Al/FeS and Li-Al/FeS 2 cells and four-cell stacks using these seals have been built and tested for electric vehicle (EV) applications. When cell performance characteristics are used to model full-scale EV ad hybrid vehicle (HV) batteries, they are projected to meet or exceed the performance requirements for a large variety of EV and HV applications. In 1992, the US Advanced Battery Consortium awarded contracts to ANL and SAFT America to continue the development of the bipolar Li-Al/FeS 2 battery to meet their long-term criteria. Both ANL and sAFT are working together to refine this technology for EV applications and scale it up to larger stacks and fully integrated battery modules.

  17. Hydrogen sulfide production from subgingival plaque samples.

    PubMed

    Basic, A; Dahlén, G

    2015-10-01

    Periodontitis is a polymicrobial anaerobe infection. Little is known about the dysbiotic microbiota and the role of bacterial metabolites in the disease process. It is suggested that the production of certain waste products in the proteolytic metabolism may work as markers for disease severity. Hydrogen sulfide (H2S) is a gas produced by degradation of proteins in the subgingival pocket. It is highly toxic and believed to have pro-inflammatory properties. We aimed to study H2S production from subgingival plaque samples in relation to disease severity in subjects with natural development of the disease, using a colorimetric method based on bismuth precipitation. In remote areas of northern Thailand, adults with poor oral hygiene habits and a natural development of periodontal disease were examined for their oral health status. H2S production was measured with the bismuth method and subgingival plaque samples were analyzed for the presence of 20 bacterial species with the checkerboard DNA-DNA hybridization technique. In total, 43 subjects were examined (age 40-60 years, mean PI 95 ± 6.6%). Fifty-six percent had moderate periodontal breakdown (CAL > 3 < 7 mm) and 35% had severe periodontal breakdown (CAL > 7 mm) on at least one site. Parvimonas micra, Filifactor alocis, Porphyromonas endodontalis and Fusobacterium nucleatum were frequently detected. H2S production could not be correlated to periodontal disease severity (PPD or CAL at sampled sites) or to a specific bacterial composition. Site 21 had statistically lower production of H2S (p = 0.02) compared to 16 and 46. Betel nut chewers had statistically significant lower H2S production (p = 0.01) than non-chewers. Rapid detection and estimation of subgingival H2S production capacity was easily and reliably tested by the colorimetric bismuth sulfide precipitation method. H2S may be a valuable clinical marker for degradation of proteins in the subgingival pocket. PMID:25280920

  18. Airborne measurements of sulfur dioxide, dimethyl sulfide, carbon disulfide, and carbonyl sulfide by isotope dilution gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Bandy, Alan R.; Thornton, Donald C.; Driedger, Arthur R., III

    1993-01-01

    A gas chromatograph/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and dimethyl sulfide and 0.2 pptv for carbon disulfide and carbonyl sulfide. All four species were simultaneously determined with a sample frequency of one sample per 6 min or greater. When only one or two species were determined, a frequency of one sample per 4 min was achieved. Because a calibration is included in each sample, no separate calibration sequence was needed. Instrument warmup was only a few minutes. The instrument was very robust in field deployments, requiring little maintenance.

  19. An intercomparison of aircraft instrumentation for tropospheric measurements of carbonyl sulfide, hydrogen sulfide, and carbon disulfide

    NASA Technical Reports Server (NTRS)

    Gregory, Gerald L.; Davis, Douglas D.; Thornton, Donald C.; Johnson, James E.; Bandy, Alan R.; Saltzman, Eric S.; Andreae, Meinrat O.; Barrick, John D.

    1993-01-01

    This paper reports results of NASA's Chemical Instrumentation and Test Evaluation (CITE 3) during which airborne measurements for carbonyl sulfide (COS), hydrogen sulfide (H2S), and carbon disulfide (CS2) were intercompared. Instrumentation included a gas chromatograph using flame photometric detection (COS, H2S, and CS2), a gas chromatograph using mass spectrometric detection (COS) and CS2), a gas chromatograph using fluorination and subsequent SF6 detection via electron capture (COS and CS2), and the Natusch technique (H2S). The measurements were made over the Atlantic Ocean east of North and South America during flights from NASA's Wallops Flight Center, Virginia, and Natal, Brazil, in August/September 1989. Most of the intercomparisons for H2S and CS2 were at mixing ratios less than 25 pptv and less than 10 pptv, respectively, with a maximum mixing ratio of about 100 pptv and 50 pptv, respectively. Carbonyl sulfide intercomparisons were at mixing ratios between 400 and 600 pptv. Measurements were intercompared from data bases constructed from time periods of simultaneous or overlapping measurements. Agreement among the COS techniques averaged about 5%, and individual measurements were generally within 10%. For H2S and at mixing ratio greater than 25 pptv, the instruments agreed on average to about 15%. At mixing ratios less than 25 pptv the agreement was about 5 pptv. For CS2 (mixing ratios less than 50 pptv), two techniques agreed on average to about 4 pptv, and the third exhibited a bias (relative to the other two) that varied in the range of 3-7 pptv. CS2 mixing ratios over the ocean east of Natal as measured by the gas chromatograph-mass spectrometer technique were only a few pptv and were below the detection limits of the other two techniques. The CITE 3 data are used to estimate the current uncertainty associated with aircraft measurements of COS, H2S, and CS2 in the remote troposphere.

  20. Alumina-supported sulfided catalysts: V. Effect of P and F on the catalytic activity of hydrodesulfurization sulfided catalysts

    SciTech Connect

    Startsev, A.N.; Klimov, O.V.; Kalinkin, A.V.; Mastikhin, V.M.

    1994-07-01

    Phosphorus and flourine additives incorporated into the Ni-Mo/Al{sub 2}O{sub 3} sulfided catalysts on various stages of their preparation considerably lower the activation energy of the thiophene hydrogenolysis reaction. The interaction of promoting additives with the active component of the hydrodesulfurization catalyst is proved by XPS and {sup 31}P NMR. The effect of additives is discussed in terms of a synchronous mechanism involving interaction of reacting molecules in the coordination sphere of a bimetallic sulfide compound.

  1. Initial Stages of Copper Sulfide Film Growth

    NASA Astrophysics Data System (ADS)

    Campin, M. J.; Zhu, J. G.; Barbour, J. C.; Braithwaite, J. W.; Provencio, P. P.

    2001-11-01

    Cu corrosion is a significant problem in electrical systems. We've used transmission electron microscopy (TEM) and ion beam scattering to study the surface instability and Cu-S surface alloying when Cu is exposed to a dilute H_2S atmosphere at 0.5% to 80% relative humidity (RH). Initially, Cu and S react and form the low chalcocite phase, Cu_2S. Cu then diffuses through the Cu_2S layer leaving Kirkendall voids at the Cu/Cu_2S interface; also, other Cu and S phases including sulfates and/or hydroxide hydrates appear. For long times, the Cu_2S growth rate is higher for sulfides formed at low RH compared to high RH. TEM revealed that the Cu_2S grains at both low and high RH are 10 nm to 50 nm with no apparent preferred orientation. However, the high RH samples exhibit many bar or plate-like structures (25x75 nm) which are numerous at higher temperatures and have some grains that span the entire Cu_2S layer. The connection between Cu_2S grain morphology and the solid-state diffusivity of Cu will be discussed. Sandia is operated under DOE contract DE-AC04-94AL85000.

  2. High temperature calorimetry of sulfide systems

    NASA Astrophysics Data System (ADS)

    Cemič, L.; Kleppa, O. J.

    1987-01-01

    Enthalpies of solution of synthetic pentlandite Fe4.5Ni4.5S8, natural violarite (Fe0.2941Ni0.7059)3S4 from Vermillion mine, Sudbury, Ontario, synthetic pyrrhotite, FeS, synthetic high temperature NiS, synthetic vaesite, NiS2, synthetic pyrite, FeS2, Ni and Fe have been measured in a Ni0.6S0.4 melt at 1,100 K. Using these data and the standard enthalpies of formation of binary sulfides, given in literature, standard enthalpies of formation of pentlandite and violarite were calculated. The following values are reported: Δ H {f/o, Pent}=-837.37±14.59 kJ mol-1 and Δ H {f/o, Viol}=-378.02±11.81 kJ mol-1. While there are no thermo-chemical data for pentlandite with which our new value can be compared, an equilibrium investigation of stoichiometric violarite by Craig (1971) gives a significantly less negative enthalpy of formation. It is suggested that the difference may be due to the higher degree of order in the natural sample.

  3. Nitrogen sulfide in giant molecular clouds.

    PubMed

    McGonagle, D; Irvine, W M

    1997-03-10

    We report a survey for nitrogen sulfide (NS) toward regions of massive star formation. NS was observed by means of its 2 pi 1/2, J = 3/2 --> 1/2, J = 5/2 --> 3/2, and J = 7/2 --> 5/2 transitions at 69, 115, and 161 GHz, respectively, and was detected toward 12 of 14 giant molecular clouds (GMCs) observed. Analysis of the hyperfine component relative line strengths suggests that NS emission is optically thin toward these sources, with the possible exception of Sgr B2(M). The fractional abundance of NS relative to molecular hydrogen is best defined for the Orion molecular cloud, where it is typically (1-4) x 10(-10), which is about an order of magnitude larger than found by some recent gas-phase chemistry models developed for quiescent clouds. Toward OMC-1, the NS integrated intensity is strongly peaked toward KL, but also extends all along the Orion ridge, resembling the distribution of SO and CH3OH. We have identified a spectral feature seen toward several sources as the ortho-NKK = 4(04) --> 3(13) J = 3 --> 2, fine-structure component of methylene (CH2; cf. Hollis, Jewell, & Lovas). We also report the first detection of the SO+ 2 pi 1/2, J = 3/2 --> 1/2, parity-e transition toward W51(MS) and L134N.

  4. Nitrogen sulfide in quiescent dark clouds.

    PubMed

    McGonagle, D; Irvine, W M; Ohishi, M

    1994-02-20

    We report the first detection of interstellar nitrogen sulfide (NS) in cold dark clouds. Several components of the 2 pi 1/2, J = 3/2 --> 1/2 and J = 5/2 --> 3/2 transitions were observed in TMC-1 and L134N. The inferred column density for TMC-1 is NNS approximately 8 x 10(12)cm-2 toward the NH3 peak in that cloud, and in L134N is NNS approximately 3 x 10(12)cm-2 toward the position of peak NH3 emission. These values correspond to fractional abundances relative to molecular hydrogen of fNS approximately 8 x 10(-10) for TMC-1, and fNS approximately 6 x 10(-10) for L134N. The NS emission is extended along the TMC-1 ridge and is also extended in L134N. The measured abundances are significantly higher than those predicted by some recent gas phase ion-molecule models.

  5. Hydrogen Sulfide and Cellular Redox Homeostasis

    PubMed Central

    Xie, Zhi-Zhong; Liu, Yang; Bian, Jin-Song

    2016-01-01

    Intracellular redox imbalance is mainly caused by overproduction of reactive oxygen species (ROS) or weakness of the natural antioxidant defense system. It is involved in the pathophysiology of a wide array of human diseases. Hydrogen sulfide (H2S) is now recognized as the third “gasotransmitters” and proved to exert a wide range of physiological and cytoprotective functions in the biological systems. Among these functions, the role of H2S in oxidative stress has been one of the main focuses over years. However, the underlying mechanisms for the antioxidant effect of H2S are still poorly comprehended. This review presents an overview of the current understanding of H2S specially focusing on the new understanding and mechanisms of the antioxidant effects of H2S based on recent reports. Both inhibition of ROS generation and stimulation of antioxidants are discussed. H2S-induced S-sulfhydration of key proteins (e.g., p66Shc and Keap1) is also one of the focuses of this review. PMID:26881033

  6. Enamel surface changes caused by hydrogen sulfide

    PubMed Central

    Yamaguchi, Takao; Hanabusa, Masao; Hosoya, Noriyasu; Chiba, Toshie; Yoshida, Takumasa; Morito, Akiyuki

    2015-01-01

    Background: Volatile sulfur compounds (VSCs) produced inside the mouth are a well-known cause of halitosis. Recent studies have suggested that VSCs modify the pathology of periodontitis by encouraging the migration of bacterial toxins associated with increased permeability of gingival epithelia, and enhancing the production of matrix metalloproteinases in gingival connective tissue. Nonetheless, the effects on the enamel of direct exposure to VSCs within the oral cavity remain unclear. In the present study, we observed the effects of VSCs in the form of hydrogen sulfide (H2S) on enamel surfaces and determined their effects on restorations. Materials and Methods: Extracted human tooth and bovine tooth samples were divided into the H2S experimental side and the control side. We observed the effects of H2S on enamel surfaces using electron microscopy and conducted a shear test. Results: We found that exposure to H2S obscured the enamel surface's crystal structure. The surface also exhibited coarseness and reticular changes. Shear testing did not reveal any differences in bond strength. Conclusions: Our findings suggested that H2S occurring inside the mouth causes changes to the crystal structure of the enamel surface that can lead to tooth wear, but that it does not diminish the effects of dental bonding in adhesive restorations. PMID:26752833

  7. Fluorescence sensing system for seafloor massive sulfides

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Okanishi, D.; Nagano, H.; Nakatani, N.; Arai, R.

    2010-12-01

    Seafloor Massive Sulfides (SMS) including Au, Ag, Cu, Zn, Pb and some rare earth elements exist in exclusive economic zones (EEZ) of Pacific island countries and the ones in Japan’s EEZ are the largest and very much attractive. However, there are many problems to be solved for the development. The most important point is the location of ore dressing. If SMS were dressed in the water, energy and cost of transport would drastically decrease. Therefore, fundamental ore dressing method which is an optical measurement, fluorescence sensing system in water is studied. It seems to be able to apply to exploration and mining. No sun light means that ideal optical measurements are possible under artificial one in deep water. However, quite less studies have been done for the optical measurements because general sensing methods at deep water are sound and supersonic waves. Using a light system, the light attenuation and fluorescence characteristics in water are studied. From this study, it is revealed that fluorescence sensing system is applicable and useful for the development of SMS.

  8. Nitrogen sulfide in quiescent dark clouds

    NASA Technical Reports Server (NTRS)

    Mcgonagle, Douglas; Irvine, William M.; Ohishi, Masatoshi

    1994-01-01

    We report the first detection of interstellar nitrogen sulfide (NS) in cold dark clouds. Several components of the (2)Pi(sub 1/2), J = 3/2 to 1/2 and J = 5/2 to 3/2 transitions were observed in TMC-1 and L134N. The inferred column density for TMC-1 is N(sub NS) approximately 8 x 10(exp 12)/sq cm toward the NH3 peak in that cloud, and in L134N is N(sub NS) approximately 3 x 10(exp 12)/sq cm toward the position of peak NH3 emission. These values correspond to fractional abundances relative to molecular hydrogen of f(sub NS) approximately 8 x 10(exp -10) for TMC-1, and f(sub NS) approximately 6 x 10(exp -10) for L134N. The NS emission is extended along the TMC-1 ridge and is also extended in L134N. The measured abundances are significantly higher than those predicted by some recent gas phase ion-molecule models.

  9. Nitrogen sulfide in giant molecular clouds

    NASA Technical Reports Server (NTRS)

    McGonagle, D.; Irvine, W. M.

    1997-01-01

    We report a survey for nitrogen sulfide (NS) toward regions of massive star formation. NS was observed by means of its 2 pi 1/2, J = 3/2 --> 1/2, J = 5/2 --> 3/2, and J = 7/2 --> 5/2 transitions at 69, 115, and 161 GHz, respectively, and was detected toward 12 of 14 giant molecular clouds (GMCs) observed. Analysis of the hyperfine component relative line strengths suggests that NS emission is optically thin toward these sources, with the possible exception of Sgr B2(M). The fractional abundance of NS relative to molecular hydrogen is best defined for the Orion molecular cloud, where it is typically (1-4) x 10(-10), which is about an order of magnitude larger than found by some recent gas-phase chemistry models developed for quiescent clouds. Toward OMC-1, the NS integrated intensity is strongly peaked toward KL, but also extends all along the Orion ridge, resembling the distribution of SO and CH3OH. We have identified a spectral feature seen toward several sources as the ortho-NKK = 4(04) --> 3(13) J = 3 --> 2, fine-structure component of methylene (CH2; cf. Hollis, Jewell, & Lovas). We also report the first detection of the SO+ 2 pi 1/2, J = 3/2 --> 1/2, parity-e transition toward W51(MS) and L134N.

  10. Signaling Molecules: Hydrogen Sulfide and Polysulfide

    PubMed Central

    2015-01-01

    Abstract Significance: Hydrogen sulfide (H2S) has been recognized as a signaling molecule as well as a cytoprotectant. It modulates neurotransmission, regulates vascular tone, and protects various tissues and organs, including neurons, the heart, and kidneys, from oxidative stress and ischemia-reperfusion injury. H2S is produced from l-cysteine by cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase. Recent Advances: In addition to these enzymes, we recently identified a novel pathway to produce H2S from d-cysteine, which involves d-amino acid oxidase (DAO) along with 3MST. These enzymes are localized in the cytoplasm, mitochondria, and peroxisomes. However, some enzymes translocate to organelles under specific conditions. Moreover, H2S-derived potential signaling molecules such as polysulfides and HSNO have been identified. Critical Issues: The physiological stimulations, which trigger the production of H2S and its derivatives and maintain their local levels, remain unclear. Future Directions: Understanding the regulation of the H2S production and H2S-derived signaling molecules and the specific stimuli that induce their release will provide new insights into the biology of H2S and therapeutic development in diseases involving these substances. Antioxid. Redox Signal. 22, 362–376. PMID:24800864

  11. Hydrogen Sulfide Signaling in the Gastrointestinal Tract

    PubMed Central

    2014-01-01

    Abstract Significance: The current literature regarding the effects of the gaseous signal molecule hydrogen sulfide (H2S) in the gastrointestinal system is reviewed. Bacterial, host and pharmaceutical-derived H2S are all considered and presented according to the physiological or pathophysiological effects of the gaseous signal molecule. These subjects include the toxicology of intestinal H2S with emphasis on bacterial-derived H2S, especially from sulfate-reducing bacteria, the role of endogenous and exogenous H2S in intestinal inflammation, and the roles of H2S in gastrointestinal motility, secretion and nociception. Recent Advances: While its pro- and anti-inflammatory, smooth muscle relaxant, prosecretory, and pro- and antinociceptive actions continue to remain the major effects of H2S in this system; recent findings have expanded the potential molecular targets for H2S in the gastrointestinal tract. Critical Issues: Numerous discrepancies remain in the literature, and definitive molecular targets in this system have not been supported by the use of competitive antagonism. Future Directions: Future work will hopefully resolve discrepancies in the literature and identify molecular targets and mechanisms of action for H2S. It is clear from the current literature that the long-appreciated relationship between H2S and the gastrointestinal tract continues to be strong as we endeavor to unravel its mysteries. Antioxid. Redox Signal. 20, 818–830. PMID:23582008

  12. Production and Physiological Effects of Hydrogen Sulfide

    PubMed Central

    2014-01-01

    Abstract Significance: Hydrogen sulfide (H2S) has been recognized as a physiological mediator with a variety of functions. It regulates synaptic transmission, vascular tone, inflammation, transcription, and angiogenesis; protects cells from oxidative stress and ischemia-reperfusion injury; and promotes healing of ulcers. Recent Advances: In addition to cystathionine β-synthase and cystathionine γ-lyase, 3-mercaptopyruvate sulfurtransferase along with cysteine aminotransferase was recently demonstrated to produce H2S. Even in bacteria, H2S produced by these enzymes functions as a defense against antibiotics, suggesting that the cytoprotective effect of H2S is a universal defense mechanism in organisms from bacteria to mammals. Critical Issues: The functional form of H2S—undissociated H2S gas, dissociated HS ion, or some other form of sulfur—has not been identified. Future Directions: The regulation of H2S production by three enzymes may lead to the identification of the physiological signals that are required to release H2S. The identification of the physiological functions of other forms of sulfur may also help understand the biological significance of H2S. Antioxid. Redox Signal. 20, 783–793. PMID:23581969

  13. Metallorganic chemical vapor deposition and atomic layer deposition approaches for the growth of hafnium-based thin films from dialkylamide precursors for advanced CMOS gate stack applications

    NASA Astrophysics Data System (ADS)

    Consiglio, Steven P.

    To continue the rapid progress of the semiconductor industry as described by Moore's Law, the feasibility of new material systems for front end of the line (FEOL) process technologies needs to be investigated, since the currently employed polysilicon/SiO2-based transistor system is reaching its fundamental scaling limits. Revolutionary breakthroughs in complementary-metal-oxide-semiconductor (CMOS) technology were recently announced by Intel Corporation and International Business Machines Corporation (IBM), with both organizations revealing significant progress in the implementation of hafnium-based high-k dielectrics along with metal gates. This announcement was heralded by Gordon Moore as "...the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s." Accordingly, the study described herein focuses on the growth of Hf-based dielectrics and Hf-based metal gates using chemical vapor-based deposition methods, specifically metallorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). A family of Hf source complexes that has received much attention recently due to their desirable properties for implementation in wafer scale manufacturing is the Hf dialkylamide precursors. These precursors are room temperature liquids and possess sufficient volatility and desirable decomposition characteristics for both MOCVD and ALD processing. Another benefit of using these sources is the existence of chemically compatible Si dialkylamide sources as co-precursors for use in Hf silicate growth. The first part of this study investigates properties of MOCVD-deposited HfO2 and HfSixOy using dimethylamido Hf and Si precursor sources using a customized MOCVD reactor. The second part of this study involves a study of wet and dry surface pre-treatments for ALD growth of HfO2 using tetrakis(ethylmethylamido)hafnium in a wafer scale manufacturing environment. The third part of this study is an investigation of

  14. Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

    2008-01-01

    Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

  15. H2S exposure elicits differential expression of candidate genes in fish adapted to sulfidic and non-sulfidic environments.

    PubMed

    Tobler, Michael; Henpita, Chathurika; Bassett, Brandon; Kelley, Joanna L; Shaw, Jennifer H

    2014-09-01

    Disentangling the effects of plasticity, genetic variation, and their interactions on organismal responses to environmental stressors is a key objective in ecological physiology. We quantified the expression of five candidate genes in response to hydrogen sulfide (H2S) exposure in fish (Poecilia mexicana, Poeciliidae) from a naturally sulfide-rich environment as well as an ancestral, non-sulfidic population to test for constitutive and environmentally dependent population differences in gene expression patterns. Common garden raised individuals that had never encountered environmental H2S during their lifetime were subjected to short or long term H2S exposure treatments or respective non-sulfidic controls. The expression of genes involved in responses to H2S toxicity (cytochrome c oxidase, vascular endothelial growth factor, and cytochrome P450-2J6), H2S detoxification (sulfide:quinone oxidoreductase), and endogenous H2S production (cystathionine γ lyase) was determined in both gill and liver tissues by real time PCR. The results indicated complex changes in expression patterns that--depending on the gene--not only differed between organs and populations, but also on the type of H2S exposure. Populations differences, both constitutive and H2S exposure dependent (i.e., plastic), in gene expression were particularly evident for sulfide:quinone oxidoreductase, vascular endothelial growth factor, and to a lesser degree for cytochrome P450-2J6. Our study uncovered putatively adaptive modifications in gene regulation that parallel previously documented adaptive changes in phenotypic traits.

  16. Geochemistry of the Kalatongke Ni-Cu-(PGE) sulfide deposit, NW China: implications for the formation of magmatic sulfide mineralization in a postcollisional environment

    NASA Astrophysics Data System (ADS)

    Song, Xie-Yan; Li, Xiang-Ren

    2009-04-01

    The Kalatongke (also spelt as Karatungk) Ni-Cu-(platinum-group element, PGE) sulfide deposit, containing 33 Mt sulfide ore with a grade of 0.8 wt.% Ni and 1.3 wt.% Cu, is located in the Eastern Junggar terrane, Northern Xinjiang, NW China. The largest sulfide ore body, which occupies more than 50 vol.% of the intrusion Y1, is dominantly comprised of disseminated sulfide with a massive sulfide inner zone. Economic disseminated sulfides also occur at the base of the intrusions Y2 and Y3. The main host rock types are norite in the lower part and diorite in the upper part of each intrusion. Enrichment in large ion lithophile elements and depletion in heavy rare earth elements relative to mid-ocean ridge basalt indicate that the mafic intrusions were produced from magmas derived from a metasomatized garnet lherzolite mantle. The average grades of the disseminated ores are 0.6 wt.% Ni and 1.1 wt.% Cu, whereas those of the massive ores are 2 wt.% Ni and 8 wt.% Cu. The PGE contents of the disseminated ores (14-69 ppb Pt and 78-162 ppb Pd) are lower than those of the massive ores (120-505 ppb Pt and 30-827 ppb Pd). However, on the basis of 100% sulfide, PGE contents of the massive sulfides are lower than those of the disseminated sulfides. Very high Cu/Pd ratios (>4.5 × 104) indicate that the Kalatongke sulfides segregated from PGE-depleted magma produced by prior sulfide saturation and separation. A negative correlation between the Cu/Pd ratio and the Pd content in 100% sulfide indicates that the PGE content of the sulfide is controlled by both the PGE concentrations in the parental silicate magma and the ratio of the amount of silicate to sulfide magma. The negative correlations between Ir and Pd indicate that the massive sulfides experienced fractionation.

  17. The effects of varying humidity on copper sulfide film formation.

    SciTech Connect

    Mayer, Thomas Michael; Missert, Nancy A.; Barbour, John Charles; Sullivan, John Patrick; Copeland, Robert Guild; Campin, Michael J.

    2004-02-01

    Detailed experiments involving extensive high resolution transmission electron microscopy (TEM) revealed significant microstructural differences between Cu sulfides formed at low and high relative humidity (RH). It was known from prior experiments that the sulfide grows linearly with time at low RH up to a sulfide thickness approaching or exceeding one micron, while the sulfide initially grows linearly with time at high RH then becomes sub-linear at a sulfide thickness less than about 0.2 microns, with the sulfidation rate eventually approaching zero. TEM measurements of the Cu2S morphology revealed that the Cu2S formed at low RH has large sized grains (75 to greater than 150 nm) that are columnar in structure with sharp, abrupt grain boundaries. In contrast, the Cu2S formed at high RH has small equiaxed grains of 20 to 50 nm in size. Importantly, the small grains formed at high RH have highly disordered grain boundaries with a high concentration of nano-voids. Two-dimensional diffusion modeling was performed to determine whether the existence of localized source terms at the Cu/Cu2S interface could be responsible for the suppression of Cu sulfidation at long times at high RH. The models indicated that the existence of static localized source terms would not predict the complete suppression of growth that was observed. Instead, the models suggest that the diffusion of Cu through Cu2S becomes restricted during Cu2S formation at high RH. The leading speculation is that the extensive voiding that exists at grain boundaries in this material greatly reduces the flux of Cu between grains, leading to a reduction in the rate of sulfide film formation. These experiments provide an approach for adding microstructural information to Cu sulfidation rate computer models. In addition to the microstructural studies, new micro-patterned test structures were developed in this LDRD to offer insight into the point defect structure of Cu2S and to permit measurement of surface reaction

  18. Airborne sulfur trace species intercomparison campaign: Sulfur dioxide, dimethylsulfide, hydrogen sulfide, carbon disulfide, and carbonyl sulfide

    NASA Technical Reports Server (NTRS)

    Gregory, Gerald L.; Hoell, James M., Jr.; Davis, Douglas D.

    1991-01-01

    Results from an airborne intercomparison of techniques to measure tropospheric levels of sulfur trace gases are presented. The intercomparison was part of the NASA Global Tropospheric Experiment (GTE) and was conducted during the summer of 1989. The intercomparisons were conducted on the Wallops Electra aircraft during flights from Wallops Island, Virginia, and Natal, Brazil. Sulfur measurements intercompared included sulfur dioxide (SO2), dimethylsulfide (DMS), hydrogen sulfide (H2S), carbon disulfide (CS2), and carbonyl sulfide (OCS). Measurement techniques ranged from filter collection systems with post-flight analyses to mass spectrometer and gas chromatograph systems employing various methods for measuring and identifying the sulfur gases during flight. Sampling schedules for the techniques ranged from integrated collections over periods as long as 50 minutes to one- to three-minute samples every ten or fifteen minutes. Several of the techniques provided measurements of more than one sulfur gas. Instruments employing different detection principles were involved in each of the sulfur intercomparisons. Also included in the intercomparison measurement scenario were a host of supporting measurements (i.e., ozone, nitrogen oxides, carbon monoxide, total sulfur, aerosols, etc.) for purposes of: (1) interpreting results (i.e., correlation of any noted instrument disagreement with the chemical composition of the measurement environment); and (2) providing supporting chemical data to meet CITE-3 science objectives of studying ozone/sulfur photochemistry, diurnal cycles, etc. The results of the intercomparison study are briefly discussed.

  19. Carbonyl sulfide removal with compost and wood chip biofilters, and in the presence of hydrogen sulfide.

    PubMed

    Sattler, Melanie L; Garrepalli, Divya R; Nawal, Chandraprakash S

    2009-12-01

    Carbonyl sulfide (COS) is an odor-causing compound and hazardous air pollutant emitted frequently from wastewater treatment facilities and chemical and primary metals industries. This study examined the effectiveness of biofiltration in removing COS. Specific objectives were to compare COS removal efficiency for various biofilter media; to determine whether hydrogen sulfide (H2S), which is frequently produced along with COS under anaerobic conditions, adversely impacts COS removal; and to determine the maximum elimination capacity of COS for use in biofilter design. Three laboratory-scale polyvinyl chloride biofilter columns were filled with up to 28 in. of biofilter media (aged compost, fresh compost, wood chips, or a compost/wood chip mixture). Inlet COS ranged from 5 to 46 parts per million (ppm) (0.10-9.0 g/m3 hr). Compost and the compost/wood chip mixture produced higher COS removal efficiencies than wood chips alone. The compost and compost/wood chip mixture had a shorter stabilization times compared with wood chips alone. Fresh versus aged compost did not impact COS removal efficiency. The presence of H2S did not adversely impact COS removal for the concentration ratios tested. The maximum elimination capacity is at least 9 g/m3 hr for COS with compost media.

  20. Chemical and colloidal aspects of collectorless flotation behavior of sulfide and non-sulfide minerals.

    PubMed

    Aghazadeh, Sajjad; Mousavinezhad, Seyed Kamal; Gharabaghi, Mahdi

    2015-11-01

    Flotation has been widely used for separation of valuable minerals from gangues based on their surface characterizations and differences in hydrophobicity on mineral surfaces. As hydrophobicity of minerals widely differs from each other, their separation by flotation will become easier. Collectors are chemical materials which are supposed to make selectively valuable minerals hydrophobic. In addition, there are some minerals which based on their surface and structural features are intrinsically hydrophobic. However, their hydrophobicities are not strong enough to be floatable in the flotation cell without collectors such as sulfide minerals, coal, stibnite, and so forth. To float these minerals in a flotation cell, their hydrophobicity should be increased in specific conditions. Various parameters including pH, Eh, size distribution, mill types, mineral types, ore characterization, and type of reaction in flotation cells affect the hydrophobicity of minerals. Surface analysis results show that when sulfide minerals experience specific flotation conditions, the reactions on the surface of these minerals increase the amount of sulfur on the surface. These phenomenons improve the hydrophobicity of these minerals due to strong hydrophobic feature of sulfurs. Collectorless flotation reduces chemical material consumption amount, increases flotation selectivity (grade increases), and affects the equipment quantities; however, it can also have negative effects. Some minerals with poor surface floatability can be increased by adding some ions to the flotation system. Depressing undesirable minerals in flotation is another application of collectorless flotation.

  1. Atmospheric measurements of carbonyl sulfide, dimethyl sulfide, and carbon disulfide using the electron capture sulfur detector

    NASA Technical Reports Server (NTRS)

    Johnson, James E.; Bates, Timothy S.

    1993-01-01

    Measurements of atmospheric dimethyl sulfide (DMS), carbonyl sulfide (COS), and carbon disulfide (CS2) were conducted over the Atlantic Ocean on board the NASA Electra aircraft during the Chemical Instrumentation Test and Evaluation (CITE 3) project using the electron capture sulfur detector (ECD-S). The system employed cryogenic preconcentration of air samples, gas chromatographic separation, catalytic fluorination, and electron capture detection. Samples collected for DMS analysis were scrubbed of oxidants with NaOH impregnated glass fiber filters to preconcentration. The detection limits (DL) of the system for COS, DMS, and CS2 were 5, 5, and 2 ppt, respectively. COS concentrations ranged from 404 to 603 ppt with a mean of 489 ppt for measurements over the North Atlantic Ocean (31 deg N to 41 deg N), and from 395 to 437 ppt with a mean of 419 ppt for measurements over the Tropical Atlantic Ocean (11 deg S to 2 deg N). DMS concentrations in the lower marine boundary layer, below 600-m altitude, ranged from below DL to 150 ppt from flights over the North Atlantic, and from 9 to 104 ppt over the Tropical Atlantic. CS2 concentrations ranged from below DL to 29 ppt over the North Atlantic. Almost all CS2 measurements over the Tropical Atlantic were below DL.

  2. Carbonyl sulfide and dimethyl sulfide exchange between trees and the atmosphere

    NASA Astrophysics Data System (ADS)

    Geng, Chunmei; Mu, Yujing

    The exchange rates of carbonyl sulfide (COS) and dimethyl sulfide (DMS) between 19 tree species and the atmosphere were investigated under natural field conditions using a static enclosure. Most of the investigated trees acted as sinks for atmospheric COS and a few trees, such as Salix matsudana Koidz. and Ulmus pumila L. could emit COS. The distinct diurnal variations of COS uptake for the investigated trees indicated that COS uptake strongly depended on photosynthetically active radiation (PAR). The average COS uptake rates for most species were much higher in summer than in autumn, indicating leaf age and temperature also might be the important influencing factors for COS uptake. Platanus orientalis L., Sophara japonica var. P. loud., Magnolia denudata Desr. and Sophora japonica L. were capable of continuously absorbing COS in daytime as well as in nighttime. For Platanus orientalis L., the maximal COS uptake rate and DMS emission rate on a single leaf area basis were -15.29 and 0.42 pmol m -2 s -1, respectively. The COS exchange fluxes for the investigated tree species depended strongly on the ambient COS mixing ratios. Significant correlation between DMS emissions and temperature was observed in summer.

  3. Carbonyl sulfide removal with compost and wood chip biofilters, and in the presence of hydrogen sulfide.

    PubMed

    Sattler, Melanie L; Garrepalli, Divya R; Nawal, Chandraprakash S

    2009-12-01

    Carbonyl sulfide (COS) is an odor-causing compound and hazardous air pollutant emitted frequently from wastewater treatment facilities and chemical and primary metals industries. This study examined the effectiveness of biofiltration in removing COS. Specific objectives were to compare COS removal efficiency for various biofilter media; to determine whether hydrogen sulfide (H2S), which is frequently produced along with COS under anaerobic conditions, adversely impacts COS removal; and to determine the maximum elimination capacity of COS for use in biofilter design. Three laboratory-scale polyvinyl chloride biofilter columns were filled with up to 28 in. of biofilter media (aged compost, fresh compost, wood chips, or a compost/wood chip mixture). Inlet COS ranged from 5 to 46 parts per million (ppm) (0.10-9.0 g/m3 hr). Compost and the compost/wood chip mixture produced higher COS removal efficiencies than wood chips alone. The compost and compost/wood chip mixture had a shorter stabilization times compared with wood chips alone. Fresh versus aged compost did not impact COS removal efficiency. The presence of H2S did not adversely impact COS removal for the concentration ratios tested. The maximum elimination capacity is at least 9 g/m3 hr for COS with compost media. PMID:20066911

  4. Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs.

    PubMed

    Klatt, Judith M; Haas, Sebastian; Yilmaz, Pelin; de Beer, Dirk; Polerecky, Lubos

    2015-09-01

    We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2 S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2 S: (i) H2 S accelerated the recovery of photosynthesis after prolonged exposure to darkness and anoxia. We suggest that this is possibly due to regulatory effects of H2 S on photosystem I components and/or on the Calvin cycle. (ii) H2 S concentrations of up to 210 μM temporarily enhanced the photosynthetic rates at low irradiance. Modelling showed that this enhancement is plausibly based on changes in the light-harvesting efficiency. (iii) Above a certain light-dependent concentration threshold H2 S also acted as an inhibitor. Intriguingly, this inhibition was not instant but occurred only after a specific time interval that decreased with increasing light intensity. That photosynthesis is most sensitive to inhibition at high light intensities suggests that H2 S inactivates an intermediate of the oxygen evolving complex that accumulates with increasing light intensity. We discuss the implications of these three effects of H2 S in the context of cyanobacterial photosynthesis under conditions with diurnally fluctuating light and H2 S concentrations, such as those occurring in microbial mats and biofilms.

  5. Selenium content of sulfide ores related to ophiolites of Greece.

    PubMed

    Economou-Eliopoulos, M; Eliopoulos, D G

    1998-01-01

    Several deposits of sulfide mineralization have been described in the ophiolites of Greece. Based on their mineralogical and chemical composition and the host rocks, two types can be distinguished: (1) the Fe-Cu-Ni-Co type consisting of pyrrhotite, chalcopyrite, Co-pentlandite, pyrite, magnetite + arsenides, +/- chromite, hosted in serpentinites, gabbros or diabases, which have variable geochemical characteristics, and (2) sulfide mineralization of the Cyprus type containing variable proportions of pyrite, chalcopyrite, bornite, and sphalerite. The spatial association with shear zones and fault systems, which is a common feature in both types of mineralization, provided the necessary permeability for the circulation of the responsible mineralized hydrothermal fluids. The selenium (Se) content in representative samples of both types of mineralization from the ophiolites of Pindos (Kondro, Perivoli, and Neropriona), Othrys (Eretria and A. Theodoroi), Veria (Trilofon), and Argolis (Ermioni) shows a wide variation. The highest values of Se (130 to 1900 ppm) were found in massive Fe-Cu sulfide ores from Kondro, in particular the Cu-rich portions (average 1300 ppm Se). The average values of Se for the Othrys sulfides are low (< 40 ppm Se). The Se content in a diabase breccia pipe (50 x 200 m) with disseminated pyrite mineralization (Neropriona) ranges from < 1 to 35 ppm Se. The highest values were noted in strongly altered samples that also exhibited a significant enrichment in platinum (1 ppm Pt). Sulfide mineralization (irregular to lens-like masses and stringers) associated with magnetite, hosted in gabbros exposed in the Perivoli area (Tsouma hill), shows a content ranging from 40 to 350 ppm Se. The distribution of Se in the studied type of the sulfide mineralization may be of genetic significance, indicating that the Se level, which often is much higher than in typical magmatic sulfides related to mafic-ultramafic rocks (average 90-100 ppm Se), may positively affect

  6. Selenium content of sulfide ores related to ophiolites of Greece.

    PubMed

    Economou-Eliopoulos, M; Eliopoulos, D G

    1998-01-01

    Several deposits of sulfide mineralization have been described in the ophiolites of Greece. Based on their mineralogical and chemical composition and the host rocks, two types can be distinguished: (1) the Fe-Cu-Ni-Co type consisting of pyrrhotite, chalcopyrite, Co-pentlandite, pyrite, magnetite + arsenides, +/- chromite, hosted in serpentinites, gabbros or diabases, which have variable geochemical characteristics, and (2) sulfide mineralization of the Cyprus type containing variable proportions of pyrite, chalcopyrite, bornite, and sphalerite. The spatial association with shear zones and fault systems, which is a common feature in both types of mineralization, provided the necessary permeability for the circulation of the responsible mineralized hydrothermal fluids. The selenium (Se) content in representative samples of both types of mineralization from the ophiolites of Pindos (Kondro, Perivoli, and Neropriona), Othrys (Eretria and A. Theodoroi), Veria (Trilofon), and Argolis (Ermioni) shows a wide variation. The highest values of Se (130 to 1900 ppm) were found in massive Fe-Cu sulfide ores from Kondro, in particular the Cu-rich portions (average 1300 ppm Se). The average values of Se for the Othrys sulfides are low (< 40 ppm Se). The Se content in a diabase breccia pipe (50 x 200 m) with disseminated pyrite mineralization (Neropriona) ranges from < 1 to 35 ppm Se. The highest values were noted in strongly altered samples that also exhibited a significant enrichment in platinum (1 ppm Pt). Sulfide mineralization (irregular to lens-like masses and stringers) associated with magnetite, hosted in gabbros exposed in the Perivoli area (Tsouma hill), shows a content ranging from 40 to 350 ppm Se. The distribution of Se in the studied type of the sulfide mineralization may be of genetic significance, indicating that the Se level, which often is much higher than in typical magmatic sulfides related to mafic-ultramafic rocks (average 90-100 ppm Se), may positively affect

  7. Adherence of sulfide mineral layers produced by corrosion of copper alloys

    SciTech Connect

    McNeil, M.B. . Office of Research); Amos, A.L.; Woods, T.L. . Dept. of Geology)

    1993-09-01

    Sulfiding corrosion of copper alloys can occur from microbiologically induced corrosion (MIC) mechanisms involving sulfate reducing bacteria (SRB) or from exposure to bulk waters containing reduced sulfur (S) species of microbiological, industrial, or geologic origin. The sulfide minerals produced generally are nonadherent. Under some circumstances, adherent sulfide layers can form and offer a degree of protection against further attack. Test were conducted in sterile synthetic seawater with various levels of dissolved sulfide, and the structure of the corrosion products was examined. Results, combined with MIC observations from literature and geochemical studies of copper sulfide paragenesis, revealed the nature of the reactions that produce dense, relatively protective sulfides.

  8. Hydrogen sulfide oxidation is coupled to oxidative phosphorylation in mitochondria of Solemya reidi

    SciTech Connect

    Powell, M.A.; Somero, G.N.

    1986-08-01

    Solemya reidi, a gutless clam found in sulfide-rich habitats, contains within its gills bacterial symbionts thought to oxidize sulfur compounds and provide a reduced carbon food source to the clam. However, the initial step or steps in sulfide oxidation occur in the animal tissue, and mitochondria isolated from both gill and symbiont-free foot tissue of the clam coupled the oxidation of sulfide to oxidative phosphorylation (adenosine triphosphate (ATP) synthesis). The ability of Solemya reidi to exploit directly the energy in sulfide for ATP synthesis is unprecedented, and suggests that sulfide-habitat animals that lack bacterial symbionts may also use sulfide as an inorganic energy source.

  9. Effects of vacuum ultraviolet and ultraviolet irradiation on ultrathin hafnium-oxide dielectric layers on (100)Si as measured with electron-spin resonance

    SciTech Connect

    Ren, H.; Shohet, J. L.; Cheng, S. L.; Nishi, Y.

    2010-05-10

    The effects of vacuum ultraviolet (VUV) (7.2 eV) and UV (4.9 eV) irradiation on hafnium-oxide dielectric layers were studied with electron-spin resonance to detect defect states. Silicon dangling-bond defects (P{sub b} centers) and positively charged oxygen vacancies (E{sup '} centers) were detected with g-factor fitting. VUV irradiation increases the level of P{sub b} states, while UV decreases the level of P{sub b} states but increases the level of E{sup '} states significantly. Rapid thermal annealing appears to mitigate these effects. Absolute values of the defect-state concentrations are presented.

  10. Enhanced effects of nonisotopic hafnium chloride in methanol as a substitute for uranyl acetate in TEM contrast of ultrastructure of fungal and plant cells.

    PubMed

    Ikeda, Ken-Ichi; Inoue, Kanako; Kanematsu, Satoko; Horiuchi, Yoshitaka; Park, Pyoyun

    2011-09-01

    This ultrastructural study showed that nonisotopic methanolic hafnium chloride and aqueous lead solution was an excellent new electron stain for enhancing TEM contrasts of fungal and plant cell structures. The ultrastructural definition provided by the new stain was often superior to that provided by conventional staining with uranyl acetate and lead. Definition of fine ultrastructure was also supported by quantitative data on TEM contrast ratios of organelles and components in fungal and plant cells. In particular, polysaccharides, which were localized in cell walls, glycogen particles, starch grains, and plant Golgi vesicle components, were much more reactive to the new stain than to the conventional one. The new nonisotopic stain is useful for enhancing the contrast of ultrastructure in biological tissues and is a safer alternative to uranyl acetate.

  11. High-energy X-ray detection by hafnium-doped organic-inorganic hybrid scintillators prepared by sol-gel method

    SciTech Connect

    Sun, Yan; Koshimizu, Masanori Yahaba, Natsuna; Asai, Keisuke; Nishikido, Fumihiko; Kishimoto, Shunji; Haruki, Rie

    2014-04-28

    With the aim of enhancing the efficiency with which plastic scintillators detect high-energy X-rays, hafnium-doped organic-inorganic hybrid scintillators were fabricated via a sol-gel method. Transmission electron microscopy of sampled material reveals the presence of Hf{sub x}Si{sub 1−x}O{sub 2} nanoparticles, dispersed in a polymer matrix that constitutes the active material of the X-ray detector. With Hf{sub x}Si{sub 1−x}O{sub 2} nanoparticles incorporated in the polymer matrix, the absorption edge and the luminescence wavelength is shifted, which we attribute to Mie scattering. The detection efficiency for 67.4-keV X-rays in a 0.6-mm-thick piece of this material is two times better than the same thickness of a commercial plastic scintillator-NE142.

  12. Crystal structure of (1,3-di-tert-butyl-η(5)-cyclo-penta-dien-yl)tri-methyl-hafnium(IV).

    PubMed

    Pérez-Redondo, Adrián; Varela-Izquierdo, Víctor; Yélamos, Carlos

    2015-05-01

    The mol-ecule of the title organometallic hafnium(IV) com-pound, [Hf(CH3)3(C13H21)] or [HfMe3(η(5)-C5H3-1,3- (t) Bu2)], adopts the classical three-legged piano-stool geometry for mono-cyclo-penta-dienylhafnium(IV) derivatives with the three methyl groups bonded to the Hf(IV) atom at the legs. The C atoms of the two tert-butyl group bonded to the cyclo-penta-dienyl (Cp) ring are 0.132 (5) and 0.154 (6) Å above the Cp least-squares plane. There are no significant inter-molecular inter-actions present between the mol-ecules in the crystal structure.

  13. Relaxation processes in an alternating-current electric field and energy loss mechanisms in hafnium diselenide cointercalated with copper and silver atoms

    NASA Astrophysics Data System (ADS)

    Pleshchev, V. G.; Melnikova, N. V.; Baranov, N. V.

    2016-09-01

    Samples based on hafnium diselenide intercalated with atoms of two types, Cu x Ag y HfSe2 at ( x + y) ≤ 0.2, have been synthesized for the first time. The frequency dependences of the components of the complex impedance have been measured using impedance spectroscopy in the frequency range from 1 Hz to 10 MHz, and the specific features of the relaxation processes occurring in samples of different compositions have been analyzed. It has been shown that the characteristic times of these processes depend not only on the total concentration of intercalated atoms, but also on the ratio between them. As the total concentration of copper and silver increases, the onset of frequency dispersion of the complex admittance shifts to the higher frequency range. The relative contributions from the conduction and relaxation polarization losses also change depending on the total and element concentrations of the intercalated atoms.

  14. Crystal structure of (1,3-di-tert-butyl-η5-cyclo­penta­dien­yl)tri­methyl­hafnium(IV)

    PubMed Central

    Pérez-Redondo, Adrián; Varela-Izquierdo, Víctor; Yélamos, Carlos

    2015-01-01

    The mol­ecule of the title organometallic hafnium(IV) com­pound, [Hf(CH3)3(C13H21)] or [HfMe3(η5-C5H3-1,3-tBu2)], adopts the classical three-legged piano-stool geometry for mono­cyclo­penta­dienylhafnium(IV) derivatives with the three methyl groups bonded to the Hf(IV) atom at the legs. The C atoms of the two tert-butyl group bonded to the cyclo­penta­dienyl (Cp) ring are 0.132 (5) and 0.154 (6) Å above the Cp least-squares plane. There are no significant inter­molecular inter­actions present between the mol­ecules in the crystal structure. PMID:25995884

  15. Hydrogen sulfide in the mammalian cardiovascular system.

    PubMed

    Liu, Yi-Hong; Lu, Ming; Hu, Li-Fang; Wong, Peter T-H; Webb, George D; Bian, Jin-Song

    2012-07-01

    For more than a century, hydrogen sulfide (H(2)S) has been regarded as a toxic gas. This review surveys the growing recognition of the role of H(2)S as an endogenous signaling molecule in mammals, with emphasis on its physiological and pathological pathways in the cardiovascular system. In biological fluids, H(2)S gas is a weak acid that exists as about 15% H(2)S, 85% HS(-), and a trace of S(2-). Here, we use "H(2)S" to refer to this mixture. H(2)S has been found to influence heart contractile functions and may serve as a cardioprotectant for treating ischemic heart diseases and heart failure. Alterations of the endogenous H(2)S level have been found in animal models with various pathological conditions such as myocardial ischemia, spontaneous hypertension, and hypoxic pulmonary hypertension. In the vascular system, H(2)S exerts biphasic regulation of a vascular tone with varying effects based on its concentration and in the presence of nitric oxide. Over the past decade, several H(2)S-releasing compounds (NaHS, Na(2)S, GYY4137, etc.) have been utilized to test the effect of exogenous H(2)S under different physiological and pathological situations in vivo and in vitro. H(2)S has been found to promote angiogenesis and to protect against atherosclerosis and hypertension, while excess H(2)S may promote inflammation in septic or hemorrhagic shock. H(2)S-releasing compounds and inhibitors of H(2)S synthesis hold promise in alleviating specific disease conditions. This comprehensive review covers in detail the effects of H(2)S on the cardiovascular system, especially in disease situations, and also the various underlying mechanisms.

  16. Electrical properties of seafloor massive sulfides

    NASA Astrophysics Data System (ADS)

    Spagnoli, Giovanni; Hannington, Mark; Bairlein, Katharina; Hördt, Andreas; Jegen, Marion; Petersen, Sven; Laurila, Tea

    2016-06-01

    Seafloor massive sulfide (SMS) deposits are increasingly seen as important marine metal resources for the future. A growing number of industrialized nations are involved in the surveying and sampling of such deposits by drilling. Drill ships are expensive and their availability can be limited; seabed drill rigs are a cost-effective alternative and more suitable for obtaining cores for resource evaluation. In order to achieve the objectives of resource evaluations, details are required of the geological, mineralogical, and physical properties of the polymetallic deposits and their host rocks. Electrical properties of the deposits and their ore minerals are distinct from their unmineralized host rocks. Therefore, the use of electrical methods to detect SMS while drilling and recovering drill cores could decrease the costs and accelerate offshore operations by limiting the amount of drilling in unmineralized material. This paper presents new data regarding the electrical properties of SMS cores that can be used in that assessment. Frequency-dependent complex electrical resistivity in the frequency range between 0.002 and 100 Hz was examined in order to potentially discriminate between different types of fresh rocks, alteration and mineralization. Forty mini-cores of SMS and unmineralized host rocks were tested in the laboratory, originating from different tectonic settings such as the intermediate-spreading ridges of the Galapagos and Axial Seamount, and the Pacmanus back-arc basin. The results indicate that there is a clear potential to distinguish between mineralized and non-mineralized samples, with some evidence that even different types of mineralization can be discriminated. This could be achieved using resistivity magnitude alone with appropriate rig-mounted electrical sensors. Exploiting the frequency-dependent behavior of resistivity might amplify the differences and further improve the rock characterization.

  17. Dimethyl sulfide in the Amazon rain forest

    NASA Astrophysics Data System (ADS)

    Jardine, K.; Yañez-Serrano, A. M.; Williams, J.; Kunert, N.; Jardine, A.; Taylor, T.; Abrell, L.; Artaxo, P.; Guenther, A.; Hewitt, C. N.; House, E.; Florentino, A. P.; Manzi, A.; Higuchi, N.; Kesselmeier, J.; Behrendt, T.; Veres, P. R.; Derstroff, B.; Fuentes, J. D.; Martin, S. T.; Andreae, M. O.

    2015-01-01

    Surface-to-atmosphere emissions of dimethyl sulfide (DMS) may impact global climate through the formation of gaseous sulfuric acid, which can yield secondary sulfate aerosols and contribute to new particle formation. While oceans are generally considered the dominant sources of DMS, a shortage of ecosystem observations prevents an accurate analysis of terrestrial DMS sources. Using mass spectrometry, we quantified ambient DMS mixing ratios within and above a primary rainforest ecosystem in the central Amazon Basin in real-time (2010-2011) and at high vertical resolution (2013-2014). Elevated but highly variable DMS mixing ratios were observed within the canopy, showing clear evidence of a net ecosystem source to the atmosphere during both day and night in both the dry and wet seasons. Periods of high DMS mixing ratios lasting up to 8 h (up to 160 parts per trillion (ppt)) often occurred within the canopy and near the surface during many evenings and nights. Daytime gradients showed mixing ratios (up to 80 ppt) peaking near the top of the canopy as well as near the ground following a rain event. The spatial and temporal distribution of DMS suggests that ambient levels and their potential climatic impacts are dominated by local soil and plant emissions. A soil source was confirmed by measurements of DMS emission fluxes from Amazon soils as a function of temperature and soil moisture. Furthermore, light- and temperature-dependent DMS emissions were measured from seven tropical tree species. Our study has important implications for understanding terrestrial DMS sources and their role in coupled land-atmosphere climate feedbacks.

  18. Hydrogen Sulfide as an Oxygen Sensor

    PubMed Central

    2015-01-01

    Abstract Significance Although oxygen (O2)-sensing cells and tissues have been known for decades, the identity of the O2-sensing mechanism has remained elusive. Evidence is accumulating that O2-dependent metabolism of hydrogen sulfide (H2S) is this enigmatic O2 sensor. Recent Advances The elucidation of biochemical pathways involved in H2S synthesis and metabolism have shown that reciprocal H2S/O2 interactions have been inexorably linked throughout eukaryotic evolution; there are multiple foci by which O2 controls H2S inactivation, and the effects of H2S on downstream signaling events are consistent with those activated by hypoxia. H2S-mediated O2 sensing has been demonstrated in a variety of O2-sensing tissues in vertebrate cardiovascular and respiratory systems, including smooth muscle in systemic and respiratory blood vessels and airways, carotid body, adrenal medulla, and other peripheral as well as central chemoreceptors. Critical Issues Information is now needed on the intracellular location and stoichometry of these signaling processes and how and which downstream effectors are activated by H2S and its metabolites. Future Directions Development of specific inhibitors of H2S metabolism and effector activation as well as cellular organelle-targeted compounds that release H2S in a time- or environmentally controlled way will not only enhance our understanding of this signaling process but also provide direction for future therapeutic applications. Antioxid. Redox Signal. 22, 377–397. “Nothing in Biology Makes Sense Except in the Light of Evolution” —Theodosius Dobzhansky (29) PMID:24801248

  19. Effect of sulfiding on an unsupported hydrotreating catalyst

    SciTech Connect

    Ho, T.C. )

    1991-09-01

    It is well known that sulfiding plays a very important role in determining the performance of commercial hydroprocessing catalysts. Recently, Ho and Reyes described the sulfiding behavior of an unsupported catalyst derived from tris(ethylenediamine) cobalt molybdate, or Co(NH{sub 2}CH{sub 2}CH{sub 2}NH{sub 2}){sub 3}MoO{sub 4}. This water soluble metallate upon sulfiding shows very high volumetric activities for both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). A major finding in Ho and Reyes study is that gas (H{sub 2}S/H{sub 2}) sulfiding of this bulk catalyst is accompanied by significant hot spotting, much more so than sulfiding of commercial catalysts. They developed a mathematical model for predicting the speed and magnitude of the traveling thermal wave. At the conditions used by Ho and Reyes, the model calculated that the catalysts could be some 20 C hotter than the gas, and the H{sub 2}S level could drop from 10% at the reactor inlet to as low as 0.5% at the outlet. This study was carried out to get some idea on the extent to which the activity of the bulk catalyst is affected by presulfiding conditions. The comparative experiments were done under somewhat exaggerated conditions.

  20. Role of sulfide and ligand strength in controlling nanosilver toxicity.

    PubMed

    Choi, Okkyoung; Clevenger, Thomas E; Deng, Baolin; Surampalli, Rao Y; Ross, Louis; Hu, Zhiqiang

    2009-04-01

    Nanosilver has been used broadly in nanotechnology enhanced consumer products because of its strong antimicrobial properties. Silver nanoparticles (AgNPs) released from these products will likely enter wastewater collection and treatment systems. This research evaluated the role of sulfide and ligand strength in controlling nanosilver toxicity to nitrifying bacteria that are important in wastewater treatment. The nanosilver toxicity in the absence and presence of ligands (SO(4)(2-), S(2-), Cl(-), PO(4)(3-), and EDTA(-)) commonly present in wastewater was determined from the oxygen uptake rate measurements. Sulfide appeared to be the only ligand to effectively reduce nanosilver toxicity. By adding a small aliquot of sulfide that was stoichiometrically complexed with AgNPs, the nanosilver toxicity to nitrifying organisms was reduced by up to 80%. Scanning electron microscopy coupled with energy dispersive X-ray analysis indicated that AgNPs were highly reactive with sulfide to form new Ag(x)S(y) complexes or precipitates. These complexes were not oxidized after a prolonged period of aeration (18h). This information is useful for wastewater treatment design and operation to reduce nanosilver toxicity via sulfide complexation. While the biotic ligand model was successful in predicting the toxicity of Ag(+) ions, it could not accurately predict the toxicity of AgNPs. Nevertheless, it could be one of the many tools useful in predicting and controlling nanosilver toxicity to wastewater microorganisms.