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Sample records for cobalt 50

  1. Cobalt

    SciTech Connect

    1993-02-01

    Cobalt is typical a by- or co-product with copper or nickel. The average crustal abundance of cobalt is 23 pans per million. Cobalt-containing minerals include cobaltite, skutterudite, and linnaeite. Due to the diversity of cobalt deposits, several techniques are used to extract the ore. The copper/cobalt-bearing ores of Zaire are extracted by open pit and underground methods. In Zambia, similar deposits are mined using modified sublevel, and cut-and-fill underground stoping methods. The sulfide and oxide ore concentrates mined in Zaire are roasted and leached in sulfuric acid. Copper is subsequently recovered by electrolysis, and cobalt is precipitated in the form of a hydrate. Finally, the hydrate is dissolved in acid and cobalt is recovered by electrolysis.

  2. An investigation of fluidized bed electrowinning of cobalt using 50 and 1000 Amp cells

    NASA Astrophysics Data System (ADS)

    Dubrovsky, M.; Evans, J. W.

    1982-09-01

    50 Amp and 1000 Amp cells equipped with fluidized bed cathodes were used to investigate the electrowinning of cobalt from sulfate solutions. The catholytes employed ranged in cobalt concentration from 100 to 4.8 grams per liter of cobalt and from acid (pH ≃1) to near neutral (pH ≃6). Superficial current densities up to 1.09 A cm-2 were used. The cells were equipped with a nearly impermeable diaphragm, permitting the use of an anolyte of composition different from that of the catholyte. The current efficiency for cobalt deposition (as conveniently determined by measuring the rate of hydrogen evolution), electrical energy consumption, and appearance of the deposit were studied as a function of catholyte composition. Reasonable current efficiencies were observed. The electrical energy consumptions were much higher than that of conventional electrowinning, but this was shown to be due to the anode chamber and diaphragm resistance losses rather than the fluidized cathode.

  3. An investigation of fluidized bed electrowinning of cobalt using 50 and 1000 Amp cells

    NASA Astrophysics Data System (ADS)

    Dubrovsky, M.; Evans, J. W.

    1991-12-01

    50 Amp and 1000 Amp cells equipped with fluidized bed cathodes were used to investigate the electrowinning of cobalt from sulfate solutions. The catholytes employed ranged in cobalt concentration from 100 to 4.8 grams per liter of cobalt and from acid (pH ≏1) to near neutral (pH-6). Superficial current densities up to 1.09 A cm-2 were used. The cells were equipped with a nearly impermeable diaphragm, permitting the use of an anolyte of composition different from that of the catholyte. The current efficiency for cobalt deposition (as conveniently determined by measuring the rate of hydrogen evolution), electrical energy consumption, and appearance of the deposit were studied as a function of catholyte composition. Reasonable current efficiencies were observed. The electrical energy consumptions were much higher than that of conventional electrowinning, but this was shown to be due to the anode chamber and diaphragm resistance losses rather than the fluidized cathode.

  4. Hydrosoluble 50% N-acetylation-thiolated chitosan complex with cobalt as a pH-responsive renal fibrosis targeting drugs.

    PubMed

    Li, Min; Tan, Lishan; Tang, Liangfeng; Li, Aiqing; Hu, Jianqiang

    2016-07-01

    About 50% N-acetylation-thiolated chitosan possessing good water solubility was modified from commercial low-molecular-weight chitosan. Chitosan performed obvious target toward renal tubular epithelial cells, and bivalent cobalt ions improved the renal fibrosis inflammation significantly. There were many complexation sites on chitosan after being modified with sulfydryl. So sulfydryl played a role of connecting bridge between chitosan and cobalt ions. Then, this N-acetylation-thiolated chitosan cobalt (NTCC) nanocomplex was designed. The nanocomplex showed excellent stability under normal physiological conditions, and cobalt would be released from the biomaterials in acidic environment. As it was affected by inflammation, the pH in renal fibrosis lesion region was acidic. So there was a specific drug release process happening in lesion region. And drug release efficiency was determined by acidity, which demonstrated that lower the acidity, the faster and more the cobalt ion release. When this nanocomplex was intraperitoneally injected into ureter-obstructed mice, obvious attenuation of fibrotic progression was shown. It was demonstrated that NTCC exhibited special renal-targeting capacity and could be chosen as drug for treating renal fibrosis. PMID:27115330

  5. Ab-Initio Study of Cobalt Impurity Effects on Phonon Spectra, Mechanical and Thermal Properties of Single Wall Carbon Nanotube (5,0)

    NASA Astrophysics Data System (ADS)

    Tashakori, H.; Khoshnevisan, B.; Kanjouri, F.

    2014-04-01

    We use density functional perturbation theory based on the pseudo-potential to calculate the phonon spectrum, phonon density of states, specific heat capacity and mechanical properties of pristine and cobalt doped (5,0) single wall carbon nanotube (CNT). In the calculations, we consider one Co atom in the center of the unit cell of the tube and it is shown that the pristine (5,0) CNT is nonmagnetic while the Co-doped tube becomes magnetic. Young's modulus for both systems is about 1TPa (after Co-doping it goes slightly higher) and the Poisson ratio for the pristine tube becomes quite a bit larger than the doped one. On the other hand, the calculated value of radial breath mode for the pristine CNT is in good agreement with the experimental reports while after Co-doping it is increased. In addition, heat capacity of the doped CNT is reduced, which leads to some important empirical applications.

  6. Cobalt poisoning

    MedlinePlus

    ... and pigments (Cobalt Blue) Magnets Some metal-on-metal hip implants Tires Cobalt was once used as a stabilizer in beer foam. It caused a condition called "beer-drinker's heart," which resulted in heart muscle weakness. This list may not be all-inclusive.

  7. Cobalt poisoning

    MedlinePlus

    ... the wear and tear of some cobalt/chromium metal-on-metal hip implants. This type of implant is an ... hip socket that is created by fitting a metal ball into a metal cup. Sometimes, metal particles ( ...

  8. Chalcogenide Cobalt telluride nanotubes

    NASA Astrophysics Data System (ADS)

    Dahal, Bishnu; Dulal, Rajendra; Pegg, Ian L.; Philip, John

    Cobalt telluride nanotubes are grown using wet chemical and hydrothermal syntheses. Wet chemical synthesized nanotubes display nearly 1: 1 Co to Te ratio. On the other hand, CoTe nanotubes synthesized using hydrothermal method show excess Co content leading to the compound Co58Te42. Both CoTe and Co58Te42 display magnetic properties, but with totally different characteristics. The Curie temperature of CoTe is higher than 400 K. However, the Tc of Co58Te42 is below 50 K. Transport properties of cobalt telluride (CoTe) nanotube devices show that they exhibit p-type semiconducting behavior. The magnetoresistance measured at 10 K show a magnetoresistance of 54%. . National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  9. Cobalt free maraging steel

    SciTech Connect

    Floreen, S.

    1984-04-17

    The subject invention is directed to ferrous-base alloys, particularly to a cobalt-free maraging steel of novel chemistry characterized by a desired combination of strength and toughness, notwithstanding that cobalt is non-essential.

  10. Cobalt recycling in the United States in 1998

    USGS Publications Warehouse

    Shedd, Kim B.

    2002-01-01

    This report is one of a series of reports on metals recycling. It defines and quantifies the 1998 flow of cobalt-bearing materials in the United States, from imports and stock releases through consumption and disposition, with particular emphasis on the recycling of industrial scrap (new scrap) and used products (old scrap). Because of cobalt?s many and diverse uses, numerous types of scrap were available for recycling by a wide variety of processes. In 1998, an estimated 32 percent of U.S. cobalt supply was derived from scrap. The ratio of cobalt consumed from new scrap to that from old scrap was estimated to be 50:50. Of all the cobalt in old scrap available for recycling, an estimated 68 percent was either consumed in the United States or exported to be recycled.

  11. Relative transition probabilities of cobalt

    NASA Technical Reports Server (NTRS)

    Roig, R. A.; Miller, M. H.

    1974-01-01

    Results of determinations of neutral-cobalt transition probabilities measured relative to Co I 4150.43 A and Co II 4145.15 A, using a gas-driven shock tube as the spectroscopic light source. Results are presented for 139 Co I lines in the range from 3940 to 6640 A and 11 Co II lines in the range from 3840 to 4730 A, which are estimated to have reliabilities ranging from 8 to 50%.

  12. Synthesis and characterization of different nanostructures of cobalt phosphate

    SciTech Connect

    Badsar, M.; Edrissi, M.

    2010-09-15

    In this research, different nanostructures of cobalt phosphate were successfully prepared. Flowerlike cobalt phosphate and platelike ammonium cobalt phosphate were made by coprecipitation method without any use of surfactant or capping agent as structure directors. Reverse micelle route in water/CTAB/n-hexanol microemulsion system was used to synthesize cobalt phosphate nanoparticles. The synthesized nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), chemical analysis, and BET. The SEM images showed that the flowerlike nanostructure is an arrangement of cobalt phosphate plates. TEM images revealed that the nanoparticles are spherical with the diameter of 30-50 nm. The purity of cobalt phosphate nanoparticles was confirmed by chemical analysis. Finally, the possible mechanisms which can describe the formation of these nanostructures were discussed.

  13. Solubility of cobalt in cement.

    PubMed

    Fregert, S; Gruvberger, B

    1978-02-01

    Unlike chromate, cobalt occurring as cobalt oxides in cement is not water-soluble in a detectable amount. Cobalt oxides are to some extent soluble in the presence of amino acids with which cobalt forms complexes. Such complexes can elicit patch test reactions. It is postulated that cobalt is more readily dissolved by forming complexes in eczematous skin than in normal skin. This may explain why cobalt sensitization in cement eczemas is secondary to chromate sensitivity. PMID:657784

  14. Cobalt Biogeochemistry in the South Atlantic: A Full-Depth Zonal Ocean Section of Total Dissolved Cobalt, and Development of a High Throughput Cobalt ICP-MS Method

    NASA Astrophysics Data System (ADS)

    Noble, A. E.; Saito, M. A.; Goepfert, T. J.

    2008-12-01

    This study presents the first high-resolution full-depth zonal section of total dissolved cobalt from a recent cruise transecting the South Atlantic Ocean along approximately 11S. This section demonstrates that current electrochemical analytical techniques are capable of producing the high precision and high resolution datasets for total dissolved cobalt expected to be generated as a part of the international GEOTRACES Program. The micronutritive role of cobalt may affect community structure in different regions of the oceans, a compelling reason to include cobalt in the trace element analyses planned for the GEOTRACES Program. This cobalt section reveals an advective source of cobalt from the African coast near Namibia, which we propose to be due to the Benguela Current interacting with reducing shelf sediments. These high concentrations of cobalt were also observed within the oxygen minimum zone that extends across much of the South Atlantic basin in this section, and are likely indicative of redox cycling of cobalt in the water column. Nutrient-like vertical structure of cobalt was observed in the surface waters across the majority of the basin due to biological utilization, and the expected hybrid-type trend is observed at depth, with scavenging of cobalt below the nutricline. Deepwater concentrations of cobalt were around 50pM across the basin below 3000m. Analysis of the shelf-life of refrigerated filtered samples stored without acidification for electrochemical cobalt analysis demonstrated that those samples which were collected specifically within oxygen minimum zones may underestimate cobalt if not analyzed within a few weeks of collection. These results motivate our on-going development of a method to measure cobalt in acidified samples via inductively coupled plasma mass spectrometry (ICP-MS). The benefit of this technique would be twofold: acidification would extend the shelf-life of the samples significantly, and samples would be preserved identically

  15. Marine cobalt resources

    USGS Publications Warehouse

    Manheim, F. T.

    1986-01-01

    Ferromanganese oxides in the open oceans are more enriched in cobalt than any other widely distributed sediments or rocks. Concentrations of cobalt exceed 1 percent in ferromanganese crusts on seamounts, ocean ridges, and other raised areas of the ocean. The cobalt-rich crusts may be the slowest growing of any earth material, accumulating one molecular layer every 1 to 3 months. Attention has been drawn to crusts as potential resources because they contain cobalt, manganese, and platinum, three of the four priority strategic metals for the United States. Moreover, unlike abyssal nodules, whose recovery is complicated by their dominant location in international waters, some of the most cobalt-rich crusts occur within the exclusive economic zone of the United States and other nations. Environmental impact statements for crust exploitation are under current development by the Department of the Interior.

  16. Samarium/Cobalt Magnets

    NASA Technical Reports Server (NTRS)

    Das, D.; Kumar, K.; Frost, R.; Chang, C.

    1985-01-01

    Intrinsic magnetic coercivities of samarium cobalt magnets made to approach theoretical limit of 350 kA/m by carefully eliminating oxygen from finished magnet by hot isostatic pressing (HIP). HIP process viable alternative to currently used sintering process.

  17. Wrought cobalt- base superalloys

    NASA Astrophysics Data System (ADS)

    Klarstrom, D. L.

    1993-08-01

    Wrought cobalt-base superalloys are used extensively in gas turbine engines because of their excellent high-temperature creep and fatigue strengths and resistance to hot corrosion attack. In addition, the unique character of the oxide scales that form on some of the alloys provides outstanding resistance to high-temperature sliding wear. This article provides a review of the evolutionary development of wrought cobalt-base alloys in terms of alloy design and physical metallurgy. The topics include solid-so-lution strengthening, carbide precipitation characteristics, and attempts to introduce age hardening. The use of PHACOMP to enhance thermal stability characteristics and the incorporation of rare-earth ele-ments to improve oxidation resistance is also reviewed and discussed. The further development of cobalt-base superalloys has been severely hampered by past political events, which have accentuated the strategic vulnerability of cobalt as a base or as an alloying element. Consequently, alternative alloys have been developed that use little or no cobalt. One such alternative, Haynes® 230TMalloy, is discussed briefly.

  18. Mechanical properties of nanocrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Karimpoor, Amir A.; Erb, Uwe

    2006-05-01

    Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

  19. Halogenation of cobalt dicarbollide

    DOEpatents

    Hurlburt, Paul K.; Abney, Kent D.; Kinkead, Scott A.

    1997-01-01

    A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10' positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron.

  20. Halogenation of cobalt dicarbollide

    DOEpatents

    Hurlburt, P.K.; Abney, K.D.; Kinkead, S.A.

    1997-05-20

    A method for selectively adding chlorine, bromine, or iodine to cobalt dicarbollide anions by means of electrophilic substitution reactions. Halogens are added only to the B10 and B10{prime} positions of the anion. The process involves use of hypohalous acid or N-halosuccinimide or gaseous chlorine in the presence of iron. 1 fig.

  1. Coordination Complexes of Cobalt.

    ERIC Educational Resources Information Center

    Williams, Gregory M.; And Others

    1989-01-01

    Described is an experiment involving the synthesis and spectral studies of cobalt complexes that not only give general chemistry students an introduction to inorganic synthesis but allows them to conduct a systematic study on the effect of different ligands on absorption spectra. Background information, procedures, and experimental results are…

  2. Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds

    NASA Technical Reports Server (NTRS)

    Atwater, James E.; Akse, James R.; Jovanovic, Goran N.; Wheeler, Richard R Jr; Sornchamni, Thana

    2003-01-01

    Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co3O4 into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry. c2003 Elsevier Science Ltd. All rights reserved.

  3. Porous cobalt spheres for high temperature gradient magnetically assisted fluidized beds

    SciTech Connect

    Atwater, James E.; Akse, James R.; Jovanovic, Goran N.; Wheeler, Richard R.; Sornchamni, Thana

    2003-02-20

    Porous metallic cobalt spheres have been prepared as high temperature capable media for employment in gradient magnetically assisted fluidization and filtration technologies. Cobalt impregnated alginate beads are first formed by extrusion of an aqueous suspension of Co{sub 3}O{sub 4} into a Co(II) chloride solution. The organic polymer is thermally decomposed yielding cobalt oxide spheres, followed by reduction to the metallic state, and densification. Cobalt beads have been produced with porosities ranging between 10 and 50%, depending upon sintering conditions. The product media have been characterized by scanning electron microscopy (SEM), nitrogen adsorption porosimetry, and vibrating sample magnetometry.

  4. Development toxicity of cobalt in the rat

    SciTech Connect

    Paternain, J.L.; Domingo, J.L.; Corbella, J.

    1988-01-01

    To determine the potential developmental toxicity of cobalt, pregnant Sprague-Dawley rats were given by gavage a daily dose of 0, 25, 50, and 100 mg/kg cobalt(II) chloride on d 6-15 of gestation. Females were sacrificed on d 20. Maternal effects included significant reductions in weight gain and food consumption, particularly at 100 mk/kg x d. Hematocrit, hemoglobin concentration, mean corpuscular volume, mean corpuscular hemoglobin, and reticulocytes were increased significantly in the 100-mg/kg x d group. No treatment-related changes were recorded in the number of corpora lutea, total implants, resorptions, the number of live and dead fetuses, fetal size parameters, or fetal sex distribution data. Increased incidence of stunted fetuses per litter was the only adverse finding at 50 and 100 mg/kg x d group. However, this increase was not statistically significant. Examination of fetuses for gross external abnormalities, skeletal malformation, or ossification variations revealed that cobalt did not produce teratogenicity or significant fetotoxicity in the rat at doses as high as 100 mg/kg x d.

  5. A Rapid Synthetic Method for the Preparation of Two Tris-Cobalt(III) Compounds.

    ERIC Educational Resources Information Center

    Jackman, Donald C.; Rillema, D. Paul

    1989-01-01

    Reports a method of preparation for tris(ethylenediamine)cobalt(III) and tris(2,2'-bipyridine)cobalt(III) that will shorten the preparation time by approximately 3 hours. Notes the time for synthesis and isolation of compound one was 1 hour (yield 38 percent) while compound two took 50 minutes (yield 71%). (MVL)

  6. Cobalt ion-containing epoxies

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St.clair, A. K.

    1983-01-01

    Varying concentrations of an organometallic cobalt complex were added to an epoxy system currently used by the aerospace industry as a composite matrix resin. Methods for combining cobalt (III) acetylacetonate with a tetraglycidyl 4,4 prime - diaminodiphenylmethane-based epoxy were investigated. The effects of increasing cobalt ion concentration on the epoxy cure were demonstrated by epoxy gel times and differential scanning calorimetry cure exotherms. Analysis on cured cobalt-containing epoxy castings included determination of glass transition temperatures by thermomechanical analysis, thermooxidative stabilities by thermogravimetric analysis, and densities in a density gradient column. Flexural strength and stiffness were also measured on the neat resin castings.

  7. Blood doping by cobalt. Should we measure cobalt in athletes?

    PubMed Central

    Lippi, Giuseppe; Franchini, Massimo; Guidi, Gian Cesare

    2006-01-01

    Background Blood doping is commonplace in competitive athletes who seek to enhance their aerobic performances through illicit techniques. Presentation of the hypothesis Cobalt, a naturally-occurring element with properties similar to those of iron and nickel, induces a marked and stable polycythemic response through a more efficient transcription of the erythropoietin gene. Testing the hypothesis Although little information is available so far on cobalt metabolism, reference value ranges or supplementation in athletes, there is emerging evidence that cobalt is used as a supplement and increased serum concentrations are occasionally observed in athletes. Therefore, given the athlete's connatural inclination to experiment with innovative, unfair and potentially unhealthy doping techniques, cobalt administration might soon become the most suited complement or surrogate for erythropoiesis-stimulating substances. Nevertheless, cobalt administration is not free from unsafe consequences, which involve toxic effects on heart, liver, kidney, thyroid and cancer promotion. Implications of the hypothesis Cobalt is easily purchasable, inexpensive and not currently comprehended within the World Anti-Doping Agency prohibited list. Moreover, available techniques for measuring whole blood, serum, plasma or urinary cobalt involve analytic approaches which are currently not practical for antidoping laboratories. Thus more research on cobalt metabolism in athletes is compelling, along with implementation of effective strategies to unmask this potentially deleterious doping practice PMID:16863591

  8. Cobalt source calibration

    SciTech Connect

    Rizvi, H.M.

    1999-12-03

    The data obtained from these tests determine the dose rate of the two cobalt sources in SRTC. Building 774-A houses one of these sources while the other resides in room C-067 of Building 773-A. The data from this experiment shows the following: (1) The dose rate of the No.2 cobalt source in Building 774-A measured 1.073 x 10{sup 5} rad/h (June 17, 1999). The dose rate of the Shepherd Model 109 Gamma cobalt source in Building 773-A measured 9.27 x 10{sup 5} rad/h (June 25, 1999). These rates come from placing the graduated cylinder containing the dosimeter solution in the center of the irradiation chamber. (2) Two calibration tests in the 774-A source placed the graduated cylinder with the dosimeter solution approximately 1.5 inches off center in the axial direction. This movement of the sample reduced the measured dose rate 0.92% from 1.083 x 10{sup 5} rad/h to 1.073 x 10{sup 5} rad/h. and (3) A similar test in the cobalt source in 773-A placed the graduated cylinder approximately 2.0 inches off center in the axial direction. This change in position reduced the measured dose rate by 10.34% from 1.036 x 10{sup 6} to 9.27 x 10{sup 5}. This testing used chemical dosimetry to measure the dose rate of a radioactive source. In this method, one determines the dose by the chemical change that takes place in the dosimeter. For this calibration experiment, the author used a Fricke (ferrous ammonium sulfate) dosimeter. This solution works well for dose rates to 10{sup 7} rad/h. During irradiation of the Fricke dosimeter solution the Fe{sup 2+} ions ionize to Fe{sup 3+}. When this occurs, the solution acquires a slightly darker tint (not visible to the human eye). To determine the magnitude of the change in Fe ions, one places the solution in an UV-VIS Spectrophotometer. The UV-VIS Spectrophotometer measures the absorbency of the solution. Dividing the absorbency by the total time (in minutes) of exposure yields the dose rate.

  9. Splitting water with cobalt.

    PubMed

    Artero, Vincent; Chavarot-Kerlidou, Murielle; Fontecave, Marc

    2011-08-01

    The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable, and efficient systems for the conversion and storage of renewable energy sources, such as solar energy. The production of hydrogen, a fuel with remarkable properties, through sunlight-driven water splitting appears to be a promising and appealing solution. While the active sites of enzymes involved in the overall water-splitting process in natural systems, namely hydrogenases and photosystem II, use iron, nickel, and manganese ions, cobalt has emerged in the past five years as the most versatile non-noble metal for the development of synthetic H(2)- and O(2)-evolving catalysts. Such catalysts can be further coupled with photosensitizers to generate photocatalytic systems for light-induced hydrogen evolution from water. PMID:21748828

  10. Cobalt chloride attenuates hypobaric hypoxia induced vascular leakage in rat brain: Molecular mechanisms of action of cobalt chloride

    SciTech Connect

    Kalpana, S.; Dhananjay, S.; Anju, B. Lilly, G.; Sai Ram, M.

    2008-09-15

    This study reports the efficacy of cobalt preconditioning in preventing hypobaric hypoxia induced vascular leakage (an indicator of cerebral edema) using male Sprague-Dawley rats as model system. Exposure of animals to hypobaric hypoxia led to a significant increase in vascular leakage, reactive oxygen species (ROS), nitric oxide (NO), and vascular endothelial growth factor (VEGF) levels. There was a marked increase in Nuclear Factor {kappa}B (NF{kappa}B) DNA binding activity and levels of pro-inflammatory cytokines such as Monocyte chemoattractant protein (MCP-1), Interferon-{gamma} (IFN-{gamma}), Interleukin-1 (IL-1), and Tumor Necrosis Factor-{alpha} (TNF-{alpha}) and cell adhesion molecules such as Vascular Cell Adhesion Molecule-1 (VCAM-1), and P-selectin. Chemical preconditioning by cobalt for 7 days (12.5 mg Co/kg b.w., oral) significantly attenuated cerebral vascular leakage and the expression of inflammatory mediators induced by hypoxia. Administration of NF{kappa}B inhibitor, curcumin (50 mg/kg b.w.; i.p.) appreciably inhibited hypoxia induced vascular leakage indicating the involvement of NF{kappa}B in causing vascular leakage. Interestingly, cobalt when administered at 12.5 mg Co/kg b.w. (i.p.), 1 h before hypoxia could not prevent the vascular leakage indicating that cobalt per se did not have an effect on NF{kappa}B. The lower levels of NF{kappa}B observed in the brains of cobalt administered animals might be due to higher levels of antioxidant and anti-inflammatory proteins (hemeoxygenase-1 and metallothionein). To conclude cobalt preconditioning inhibited hypobaric hypoxia induced cerebral vascular leakage by lowering NF{kappa}B DNA binding activity and its regulated pro-inflammatory mediators. This is contemplated to be mediated by cobalt induced reduction in ROS/NO and increase in HO-1 and MT.

  11. Regression of posterior uveal melanomas following cobalt-60 plaque radiotherapy

    SciTech Connect

    Cruess, A.F.; Augsburger, J.J.; Shields, J.A.; Brady, L.W.; Markoe, A.M.; Day, J.L.

    1984-12-01

    A method has been devised for evaluating the rate and extent of regression of the first 100 consecutive patients with a posterior uveal melanoma that had been managed by Cobalt-60 plaque radiotherapy at Wills Eye Hospital. It was found that the average posterior uveal melanoma in the series did not regress rapidly to a flat, depigmented scar but shrank slowly and persisted as a residual mass approximately 50% of the thickness of the original tumor at 54 months following Cobalt-60 plaque radiotherapy. The authors also found that the rate and extent of regression of the tumors in patients who subsequently developed metastatic melanoma were not appreciably different from the rate and extent of regression of the tumors in patients who remained well systemically. These observations indicate that the rate and extent of regression of posterior uveal melanomas following Cobalt-60 plaque radiotherapy are poor indicators of the prognosis of the affected patients for subsequent development of clinical metastatic disease.

  12. Cobalt: for strength and color

    USGS Publications Warehouse

    Boland, Maeve A.; Kropschot, S.J.

    2011-01-01

    Cobalt is a shiny, gray, brittle metal that is best known for creating an intense blue color in glass and paints. It is frequently used in the manufacture of rechargeable batteries and to create alloys that maintain their strength at high temperatures. It is also one of the essential trace elements (or "micronutrients") that humans and many other living creatures require for good health. Cobalt is an important component in many aerospace, defense, and medical applications and is a key element in many clean energy technologies. The name cobalt comes from the German word kobold, meaning goblin. It was given this name by medieval miners who believed that troublesome goblins replaced the valuable metals in their ore with a substance that emitted poisonous fumes when smelted. The Swedish chemist Georg Brandt isolated metallic cobalt-the first new metal to be discovered since ancient times-in about 1735 and identified some of its valuable properties.

  13. Microstructure and characterization of a novel cobalt coating prepared by cathode plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Quan, Cheng; He, Yedong

    2015-10-01

    A novel cobalt coating was prepared by cathode plasma electrolytic deposition (CPED). The kinetics of the electrode process in cathode plasma electrolytic deposition was studied. The composition and microstructure of the deposited coatings were investigated by SEM, EDS, XRD and TEM. The novel cobalt coatings were dense and uniform, showing a typically molten morphology, and were deposited with a rather fast rate. Different from the coatings prepared by conventional electrodeposition or chemical plating, pure cobalt coatings with face center cubic (fcc) structure were obtained by CPED. The deposited coatings were nanocrystalline structure with an average grain size of 40-50 nm, exhibited high hardness, excellent adhesion with the stainless steels, and superior wear resistance. The properties of the novel cobalt coatings prepared by CPED have been improved significantly, as compared with that prepared by conventional methods. It reveals that cathode plasma electrolytic deposition is an effective way to prepare novel cobalt coatings with high quality.

  14. Hollow Cobalt Selenide Microspheres: Synthesis and Application as Anode Materials for Na-Ion Batteries.

    PubMed

    Ko, You Na; Choi, Seung Ho; Kang, Yun Chan

    2016-03-16

    The electrochemical properties of hollow cobalt oxide and cobalt selenide microspheres are studied for the first time as anode materials for Na-ion batteries. Hollow cobalt oxide microspheres prepared by one-pot spray pyrolysis are transformed into hollow cobalt selenide microspheres by a simple selenization process using hydrogen selenide gas. Ultrafine nanocrystals of Co3O4 microspheres are preserved in the cobalt selenide microspheres selenized at 300 °C. The initial discharge capacities for the Co3O4 and cobalt selenide microspheres selenized at 300 and 400 °C are 727, 595, and 586 mA h g(-1), respectively, at a current density of 500 mA g(-1). The discharge capacities after 40 cycles for the same samples are 348, 467, and 251 mA h g(-1), respectively, and their capacity retentions measured from the second cycle onward are 66, 91, and 50%, respectively. The hollow cobalt selenide microspheres have better rate performances than the hollow cobalt oxide microspheres. PMID:26918934

  15. Processing technologies for extracting cobalt from domestic resources. Information Circular/1988

    SciTech Connect

    Jordan, C.E.

    1988-01-01

    A summary of the cobalt processing technologies for the major domestic resources is presented. The processing technologies for the Blackbird, Madison Mine, Duluth Gabbro, iron ore pyrite, laterites, and manganese sea nodules are nearly complete, but the economics are not favorable. Research on these resources should be limited to approaches that promise to cut the total processing costs by at least 50 pct. The most-promising sources of cobalt are the spent-copper leach solutions and siegenite from the Missouri lead ores. Research on cobalt processing from these two sources needs to be completed.

  16. Wrought cobalt-base superalloys

    SciTech Connect

    Klarstrom, D.L. )

    1993-08-01

    Wrought cobalt-base superalloys are used extensively in gas turbine engines because of their excellent high-temperature creep and fatigue strength and resistance to hot corrosion attach. In addition, the unique character of the oxide scales that form on some of the alloys provides outstanding resistance to high-temperature sliding wear. This article provides a review of the evolutionary development of wrought cobalt-base alloys in terms of alloy design and physical metallurgy. The topics include solid-solution strengthening, carbide precipitation characteristics, and attempts to introduce age hardening. The use of PHACOMP to enhance thermal stability characteristics and the incorporation of rare-earth elements to improve oxidation resistance is also reviewed and discussed. The further development of cobalt-base superalloys has been severely hampered by past political events, which have accentuated the strategic vulnerability of cobalt as a base or as an alloying element. Consequently, alternative alloys have been developed that use little or no cobalt. One such alternative, Haynes 230 alloy, is discussed briefly.

  17. Cobalt Alums. A Demonstration Experiment

    NASA Astrophysics Data System (ADS)

    Schäffer, Claus E.; Steenberg, Paul

    2002-08-01

    The demonstration experiment describes the isolation of [Co(H2O)6]3+ both as the pure blue crystalline cesium cobalt alum, CsCo(SO4)2·12H2O, and as a light greenish-blue solid solution of ammonium cobalt alum in (NH4)Al(SO4)2·12H2O. The hexaaquacobalt(III) ion is prepared chemically by oxidation with hydrogen peroxide, taking advantage of the stabilization of CoIII relative to CoII by complexation with the carbonate ligand. A brief description of alum structure and a characterization of alum subclasses are included.

  18. Controlling the misuse of cobalt in horses.

    PubMed

    Ho, Emmie N M; Chan, George H M; Wan, Terence S M; Curl, Peter; Riggs, Christopher M; Hurley, Michael J; Sykes, David

    2015-01-01

    Cobalt is a well-established inducer of hypoxia-like responses, which can cause gene modulation at the hypoxia inducible factor pathway to induce erythropoietin transcription. Cobalt salts are orally active, inexpensive, and easily accessible. It is an attractive blood doping agent for enhancing aerobic performance. Indeed, recent intelligence and investigations have confirmed cobalt was being abused in equine sports. In this paper, population surveys of total cobalt in raceday samples were conducted using inductively coupled plasma mass spectrometry (ICP-MS). Urinary threshold of 75 ng/mL and plasma threshold of 2 ng/mL could be proposed for the control of cobalt misuse in raceday or in-competition samples. Results from administration trials with cobalt-containing supplements showed that common supplements could elevate urinary and plasma cobalt levels above the proposed thresholds within 24 h of administration. It would therefore be necessary to ban the use of cobalt-containing supplements on raceday as well as on the day before racing in order to implement and enforce the proposed thresholds. Since the abuse with huge quantities of cobalt salts can be done during training while the use of legitimate cobalt-containing supplements are also allowed, different urinary and plasma cobalt thresholds would be required to control cobalt abuse in non-raceday or out-of-competition samples. This could be achieved by setting the thresholds above the maximum urinary and plasma cobalt concentrations observed or anticipated from the normal use of legitimate cobalt-containing supplements. Urinary threshold of 2000 ng/mL and plasma threshold of 10 ng/mL were thus proposed for the control of cobalt abuse in non-raceday or out-of-competition samples. PMID:25256240

  19. Cobalt(II) and Cobalt(III) Coordination Compounds.

    ERIC Educational Resources Information Center

    Thomas, Nicholas C.; And Others

    1989-01-01

    Presents a laboratory experiment which illustrates the formation of tris(phenanthroline)cobalt complexes in the 2+ and 3+ oxidation states, the effect of coordination on reactions of the ligand, and the use of a ligand displacement reaction in recovering the transformed ligand. Uses IR, UV-VIS, conductivity, and NMR. (MVL)

  20. Cosine (Cobalt Silicide Growth Through Nitrogen-Induced Epitaxy) Process For Epitaxial Cobalt Silicide Formation For High Performance Sha

    DOEpatents

    Lim, Chong Wee; Shin, Chan Soo; Gall, Daniel; Petrov, Ivan Georgiev; Greene, Joseph E.

    2004-09-28

    A method for forming an epitaxial cobalt silicide layer on a MOS device includes sputter depositing cobalt in an ambient to form a first layer of cobalt suicide on a gate and source/drain regions of the MOS device. Subsequently, cobalt is sputter deposited again in an ambient of argon to increase the thickness of the cobalt silicide layer to a second thickness.

  1. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    SciTech Connect

    Ramesh, Thimmasandra Narayan

    2010-06-15

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co{sub 3}O{sub 4}. The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co{sub 3}O{sub 4} phase.

  2. Supported, Alkali-Promoted Cobalt Oxide Catalysts for NOx Removal from Coal Combustion Flue Gases

    SciTech Connect

    Morris D. Argyle

    2005-12-31

    A series of cobalt oxide catalysts supported on alumina ({gamma}-Al{sub 2}O{sub 3}) were synthesized with varying contents of cobalt and of added alkali metals, including lithium, sodium, potassium, rubidium, and cesium. Unsupported cobalt oxide catalysts and several cobalt oxide catalysts supported ceria (CeO{sub 2}) with varying contents of cobalt with added potassium were also prepared. The catalysts were characterized with UV-visible spectroscopy and were examined for NO{sub x} decomposition activity. The CoO{sub x}/Al{sub 2}O{sub 3} catalysts and particularly the CoO{sub x}/CeO{sub 2} catalysts show N{sub 2}O decomposition activity, but none of the catalysts (unsupported Co{sub 3}O{sub 4} or those supported on ceria or alumina) displayed significant, sustained NO decomposition activity. For the Al{sub 2}O{sub 3}-supported catalysts, N{sub 2}O decomposition activity was observed over a range of reaction temperatures beginning about 723 K, but significant (>50%) conversions of N{sub 2}O were observed only for reaction temperatures >900 K, which are too high for practical commercial use. However, the CeO{sub 2}-supported catalysts display N{sub 2}O decomposition rates similar to the Al{sub 2}O{sub 3}-supported catalysts at much lower reaction temperatures, with activity beginning at {approx}573 K. Conversions of >90% were achieved at 773 K for the best catalysts. Catalytic rates per cobalt atom increased with decreasing cobalt content, which corresponds to increasing edge energies obtained from the UV-visible spectra. The decrease in edge energies suggests that the size and dimensionality of the cobalt oxide surface domains increase with increasing cobalt oxide content. The rate data normalized per mass of catalyst that shows the activity of the CeO{sub 2}-supported catalysts increases with increasing cobalt oxide content. The combination of these data suggest that supported cobalt oxide species similar to bulk Co{sub 3}O{sub 4} are inherently more active than

  3. The respiratory effects of cobalt

    SciTech Connect

    Cugell, D.W.; Morgan, W.K.; Perkins, D.G.; Rubin, A. )

    1990-01-01

    We studied seven subjects with certain manifestations of cobalt-induced lung disease. All worked with cobalt and were involved in either the production or use of hard metal. The mode of presentation varied from an acute hypersensitivity pneumonitis that cleared completely when exposure ceased to progressive severe interstitial fibrosis of the lungs. In one subject reexposure was followed by a recurrence of the symptoms. All subjects showed restrictive ventilatory impairment and a reduction of their diffusing capacity. The radiologic appearances varied greatly. While two subjects had clear roentgenograms with small lung volumes, others had a micronodular pattern or small blotchy nodular infiltrates, and one had diffuse reticulonodulation as is seen in cryptogenic fibrosing alveolitis. The pathologic appearances varied between desquamative interstitial pneumonia and overt mural fibrosis of the alveoli. Six of the seven patients had multinucleated giant cells in their biopsy specimens or bronchoalveolar lavage fluid.

  4. Cobalt single-molecule magnet

    NASA Astrophysics Data System (ADS)

    Yang, En-Che; Hendrickson, David N.; Wernsdorfer, Wolfgang; Nakano, Motohiro; Zakharov, Lev N.; Sommer, Roger D.; Rheingold, Arnold L.; Ledezma-Gairaud, Marisol; Christou, George

    2002-05-01

    A cobalt molecule that functions as a single-molecule magnet, [Co4(hmp)4(MeOH)4Cl4], where hmp- is the anion of hydroxymethylpyridine, is reported. The core of the molecule consists of four Co(II) cations and four hmp- oxygen atom ions at the corners of a cube. Variable-field and variable-temperature magnetization data have been analyzed to establish that the molecule has a S=6 ground state with considerable negative magnetoanisotropy. Single-ion zero-field interactions (DSz2) at each cobalt ion are the origin of the negative magnetoanisotropy. A single crystal of the compound was studied by means of a micro-superconducting quantum interference device magnetometer in the range of 0.040-1.0 K. Hysteresis was found in the magnetization versus magnetic field response of this single crystal.

  5. Technical and business considerations of cobalt hydrometallurgy

    NASA Astrophysics Data System (ADS)

    Peek, Edgar; Åkre, Torjus; Asselin, Edouard

    2009-10-01

    Approximately 55,000 tonnes of cobalt are produced annually worldwide, which represents an estimated 1-3 billion in annual sales depending on cobalt price changes. Cobalt is a common impurity in both non-ferrous mineral sulfide and oxide processing. In this paper some business and technical considerations are presented to facilitate the decision-making process required to produce either an intermediate or a finished cobalt product via a hydrometallurgical route. Methods currently available and practiced for the recovery of cobalt are considered, and process requirements up- and down-stream associated with each chosen method are discussed. In particular, some environmental, energy, or other sustainable development implications of each process are mentioned. An outlook on the future of the cobalt industry and anticipated future trends is included.

  6. Magnetic dipolar interaction induced cobalt nanowires.

    PubMed

    Gong, Maogang; Dai, Qilin; Ren, Shenqiang

    2016-02-19

    The dipolar interaction of magnetic nanoparticles is of intense interest to engineer material self-assembly for anisotropic functional nanostructures. Here we report the solution synthesis of cobalt nanowires, where the one-dimensional nanowire formation is ultimately dependent on the magnetic dipolar interaction to realize in situ assembly of cobalt nanoparticles. The morphology transition of cobalt nanostructures is well controlled via the ligand-free synthesis and thermal decomposition of zero-valent cobalt precursor. This study provides a self-assembly approach to the development of anisotropic cobalt nanostructures and a better understanding of nucleation parameters, which are demonstrated to correlate strongly with the size and morphology of final cobalt nanowires. This approach may be extended to other magnetic materials for the control of their nanostructure and magnetic performance. PMID:26783195

  7. Mineral resource of the month: cobalt

    USGS Publications Warehouse

    Shedd, Kim B.

    2009-01-01

    Cobalt is a metal used in numerous commercial, industrial and military applications. On a global basis, the leading use of cobalt is in rechargeable lithium-ion, nickel-cadmium and nickel-metal hydride battery electrodes. Cobalt use has grown rapidly since the early 1990s, with the development of new battery technologies and an increase in demand for portable electronics such as cell phones, laptop computers and cordless power tools.

  8. Cobalt silica magnetic nanoparticles with functional surfaces

    NASA Astrophysics Data System (ADS)

    Vadala, Michael L.; Zalich, Michael A.; Fulks, David B.; St. Pierre, Tim G.; Dailey, James P.; Riffle, Judy S.

    2005-05-01

    Cobalt nanoparticles encased in polysiloxane block copolymers have been heated at 600-700 °C to form protective shells around the particles, which contain crosslinked Si-O structures, and to anneal the cobalt. Methods to functionalize and modify the surfaces of the pyrolyzed/annealed silica-cobalt complexes with amines, isocyanates, poly(ethylene oxide), poly( L-lactide) and polydimethylsiloxane (PDMS) are presented.

  9. Oxidation of low cobalt alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1982-01-01

    Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

  10. Sorption of cobalt on activated carbons from aqueous solutions

    SciTech Connect

    Paajanen, A.; Lehto, J.; Santapakka, T.; Morneau, J.P.

    1997-01-01

    The efficiencies of 15 commercially available activated carbons were tested for the separation of trace cobalt ({sup 60}Co) in buffer solutions at pH 5.0, 6.7, and 9.1. On the basis of the results four carbon products, Diahope-006, Eurocarb TN5, Hydraffin DG47, and Norit ROW Supra, were selected for further study. These carbons represented varying (low, medium and high) cobalt removal efficiencies and were prepared of three typical raw materials: peat, coconut shell, or coal. Study was made of the effects on sorption efficiencies of factors of interest in metal/radionuclide-bearing waste effluents. These factors were pH, sodium ions, borate, and citrate.

  11. Mass spectrometric and modeling investigations of bimetallic silver-cobalt clusters

    NASA Astrophysics Data System (ADS)

    Janssens, Ewald; van Hoof, Thibaut; Veldeman, Nele; Neukermans, Sven; Hou, Marc; Lievens, Peter

    2006-05-01

    The stability of bimetallic silver-cobalt clusters with less than 50 atoms is studied experimentally and their associated geometries are predicted by classical modeling. The clusters are created by laser vaporization and inert gas condensation. Their mass distribution is analyzed with time-of-flight mass spectrometry. For clusters containing mainly silver, we find strong quantum size effects related to itinerant behavior of the silver and cobalt valence electrons. In the case of clusters containing mainly cobalt, no pronounced size effects appear in the mass spectra. Photofragmentation experiments reveal that neutral silver atom evaporation is the favorable channel, suggesting that the AgCo bonds are weaker than the CoCo bonds. Consistently, and for both sets of clusters, Metropolis Monte-Carlo simulations predict these clusters to have icosahedral based structures that may depend on temperature. In clusters containing mainly silver, cobalt sits at the cluster center and fragmentation proceeds by the evaporation of silver surface atoms. In clusters containing mainly cobalt, silver atoms also locate at the periphery and are more weakly bound to the cluster than cobalt surface atoms.

  12. Cobalt Reduction Guidelines, Revision 1. Final report

    SciTech Connect

    Not Available

    1993-12-01

    This report, which updates and supersedes an earlier report (EPRI NP-6737) on the same subject, describes methods for establishing a program to identify nuclear power plant valves with high-cobalt hardfacing that are potential significant contributors to the cobalt inventory that is irradiated in the reactor core. The resulting radioactive cobalt isotope, cobalt-60, is a major contributor to plant radiation levels and therefore occupational doses received by plant operational and maintenance personnel. A methodology to determine whether hardfacing is actually required on specific valves is also described as is the physical, mechanical and wear properties of high-cobalt and potential replacement cobalt-free hardfacing and trim alloys. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. Current world-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The regulatory and industry code issues related to replacing and/or changing valve hardfacing materials are discussed. The actions and responsibilities of utility management in implementing an effective cobalt-reduction program are also delineated.

  13. Cobalt and nickel content of Asian cements.

    PubMed

    Goh, C L; Kwok, S F; Gan, S L

    1986-09-01

    The total cobalt and nickel concentration of 11 brands of Asian cement ranged from 8.1 to 14.2 micrograms/g and 14.9 to 28.5 micrograms/g, respectively. These metals exist mainly as insoluble salts; the water-soluble concentration of cobalt and nickel in the cements ranged from 0.39 to 0.65 micrograms/g and from 0-1.2 micrograms/g, respectively. 1.5% (4/272) of construction workers in a prefabrication construction factory had cobalt sensitivity. All had allergic contact dermatitis from chromate in cement. No worker had isolated cobalt sensitivity and cement dermatitis. It appeared that sensitization to cobalt in cement occurs only secondarily to an existing cement dermatitis. 1.8% (5/272) workers had nickel sensitivity: 2 with allergic contact dermatitis to nickel in their watches, 2 were asymptomatic and 1 had allergic contact dermatitis to chromate and cobalt in cement. The low prevalence of cobalt and nickel sensitivity from cement was probably related to the low concentration of soluble cobalt and nickel salts in the cement. However, these insoluble salts can form soluble complexes with body fluids on eczematous skin and sensitize the skin. PMID:2946537

  14. Inhalation cancer risk assessment of cobalt metal.

    PubMed

    Suh, Mina; Thompson, Chad M; Brorby, Gregory P; Mittal, Liz; Proctor, Deborah M

    2016-08-01

    Cobalt compounds (metal, salts, hard metals, oxides, and alloys) are used widely in various industrial, medical and military applications. Chronic inhalation exposure to cobalt metal and cobalt sulfate has caused lung cancer in rats and mice, as well as systemic tumors in rats. Cobalt compounds are listed as probable or possible human carcinogens by some agencies, and there is a need for quantitative cancer toxicity criteria. The U.S. Environmental Protection Agency has derived a provisional inhalation unit risk (IUR) of 0.009 per μg/m(3) based on a chronic inhalation study of soluble cobalt sulfate heptahydrate; however, a recent 2-year cancer bioassay affords the opportunity to derive IURs specifically for cobalt metal. The mechanistic data support that the carcinogenic mode of action (MOA) is likely to involve oxidative stress, and thus, non-linear/threshold mechanisms. However, the lack of a detailed MOA and use of high, toxic exposure concentrations in the bioassay (≥1.25 mg/m(3)) preclude derivation of a reference concentration (RfC) protective of cancer. Several analyses resulted in an IUR of 0.003 per μg/m(3) for cobalt metal, which is ∼3-fold less potent than the provisional IUR. Future research should focus on establishing the exposure-response for key precursor events to improve cobalt metal risk assessment. PMID:27177823

  15. Cobalt Complexes as Antiviral and Antibacterial Agents

    PubMed Central

    Chang, Eddie L.; Simmers, Christa; Knight, D. Andrew

    2010-01-01

    Metal ion complexes are playing an increasing role in the development of antimicrobials. We review here the antimicrobial properties of cobalt coordination complexes in oxidation state 3+. In addition to reviewing the cobalt complexes containing polydentate donor ligands, we also focus on the antimicrobial activity of the homoleptic [Co(NH3)6]3+ ion.

  16. Cobalt and possible oxidant-mediated toxicity.

    PubMed

    Nemery, B; Lewis, C P; Demedts, M

    1994-06-30

    The occurrence of interstitial lung disease similar to hard metal lung disease in diamond polishers who had been exposed to cobalt (in the absence of tungsten carbide) through the use of polishing disks containing microdiamonds sintered with cobalt, led us to experimentally test the hypothesis that cobalt has pro-oxidant activity in lung tissue. Several experiments were carried out in which we measured indices of oxidant stress, mainly changes in the oxidation state of glutathione and in the activity of the pentose phosphate pathway, upon exposure of hamster pulmonary tissue to CoCl2 in vivo by intratracheal instillation, or in vitro by incubating lung slices. These experiments indicated that cobalt ions are capable of causing thiol oxidation in lung tissue as an early manifestation of oxidant stress, but more studies are needed to establish the relevance of this mechanism in the causation of lung disease in subjects exposed to cobalt-containing dusts. PMID:7939609

  17. Exposure to cobalt in the production of cobalt and cobalt compounds and its effect on the heart

    PubMed Central

    Linna, A; Oksa, P; Groundstroem, K; Halkosaari, M; Palmroos, P; Huikko, S; Uitti, J

    2004-01-01

    Aims: To investigate whether exposure to cobalt in cobalt plants has any measurable effect on the cardiovascular system. Methods: Occupational, cross sectional study, using a self administered questionnaire, blood pressure measurement, electrocardiography, and laboratory tests in which 203 male workers with at least one year of exposure to cobalt and 94 unexposed controls participated. Echocardiography was performed on a subset of 122 most highly exposed cobalt workers, of which 109 were analysed, and on 60 controls, of which 57 were analysed. Analysis of covariance and a multiple regression analysis were used to evaluate the data. Results: Two of the echocardiography parameters measured were associated with cobalt exposure. In the higher exposure group the left ventricular isovolumic relaxation time (mean 53.3, 49.1, and 49.7 ms in the high exposure, low exposure, and control groups respectively) and the deceleration time of the velocity of the early rapid filling wave (mean 194.3, 180.5, and 171.7 ms for those in the high exposure, low exposure, and control groups respectively) were prolonged, indicating altered left ventricular relaxation and early filling. Conclusion: Cumulative exposure to cobalt was found to be associated with the results of Doppler echocardiography measurements, indicating altered diastole. This finding supports the hypothesis that cobalt accumulation in the myocardium could affect myocardial function. Whether this finding has clinical implications remains to be evaluated. PMID:15477280

  18. Electronic transitions of cobalt monoboride.

    PubMed

    Ng, Y W; Pang, H F; Cheung, A S-C

    2011-11-28

    Electronic transition spectrum of cobalt monoboride (CoB) in the visible region between 495 and 560 nm has been observed and analyzed using laser-induced fluorescence spectroscopy. CoB molecule was produced by the reaction of laser-ablated cobalt atom and diborane (B(2)H(6)) seeded in argon. Fifteen vibrational bands with resolved rotational structure have been recorded, which included transitions of both Co(10)B and Co(11)B isotopic species. Our analysis showed that the observed transition bands are ΔΩ = 0 transitions with Ω" = 2 and Ω" = 3 lower states. Four transition systems have been assigned, namely, the [18.1](3)Π(2)-X(3)Δ(2), the [18.3](3)Φ(3)-X(3)Δ(3), the [18.6]3- X(3)Δ(3), and the [19.0]2-X(3)Δ(2) systems. The bond length, r(o), of the X(3)Δ(3) state of CoB is determined to be 1.705 Å. The observed rotational lines showed unresolved hyperfine structure arising from the nuclei, which conforms to the Hund's case (a(β)) coupling scheme. This work represents the first experimental investigation of the CoB spectrum. PMID:22128936

  19. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Cobaltous salts and its derivatives. 189.120... or Use as Human Food § 189.120 Cobaltous salts and its derivatives. (a) Cobaltous salts are the... and to prevent “gushing.” (b) Food containing any added cobaltous salts is deemed to be adulterated...

  20. Effect of Co/Ni ratios in cobalt nickel mixed oxide catalysts on methane combustion

    SciTech Connect

    Lim, Tae Hwan; Cho, Sung June; Yang, Hee Sung; Engelhard, Mark H.; Kim, Do Heui

    2015-07-31

    A series of cobalt nickel mixed oxide catalysts with the varying ratios of Co to Ni, prepared by co-precipitation method, were applied to methane combustion. Among the various ratios, cobalt nickel mixed oxides having the ratios of Co to Ni of (50:50) and (67:33) demonstrate the highest activity for methane combustion. Structural analysis obtained from X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) evidently demonstrates that CoNi (50:50) and (67:33) samples consist of NiCo2O4and NiO phase and, more importantly, NiCo2O4spinel structure is largely distorted, which is attributed to the insertion of Ni2+ions into octahedral sites in Co3O4spinel structure. Such structural dis-order results in the enhanced portion of surface oxygen species, thus leading to the improved reducibility of the catalysts in the low temperature region as evidenced by temperature programmed reduction by hydrogen (H2TPR) and X-ray photoelectron spectroscopy (XPS) O 1s results. They prove that structural disorder in cobalt nickel mixed oxides enhances the catalytic performance for methane combustion. Thus, it is concluded that a strong relationship between structural property and activity in cobalt nickel mixed oxide for methane combustion exists and, more importantly, distorted NiCo2O4spinel structure is found to be an active site for methane combustion.

  1. Computational Characterization of Redox Non-Innocence in Cobalt-Bis(Diaryldithiolene)-Catalyzed Proton Reduction.

    PubMed

    Panetier, Julien A; Letko, Christopher S; Tilley, T Don; Head-Gordon, Martin

    2016-01-12

    Localized orbital bonding analysis (LOBA) was employed to probe the oxidation state in cobalt-bis(diaryldithiolene)-catalyzed proton reduction in nonaqueous media. LOBA calculations provide both the oxidation state and chemically intuitive views of bonding in cobalt-bis(diaryldithiolene) species and therefore allow characterization of the role of the redox non-innocent dithiolene ligand. LOBA results show that the reduction of the monoanion species [1Br](-) is metal-centered and gives a cobalt(II) ion species, [1Br](2-), coordinated to two dianionic ene-1,2-dithiolates. This electronic configuration is in agreement with the solution magnetic moment observed for the analogous salt [1F](2-) (μeff = 2.39 μB). Protonation of [1Br](2-) yields the cobalt(III)-hydride [1Br(CoH)](-) species in which the Co-H bond is computed to be highly covalent (Löwdin populations close to 0.50 on cobalt and hydrogen atoms). Further reduction of [1Br(CoH)](-) forms a more basic cobalt(II)-H intermediate [1Br(CoH)](2-) (S = 0) from which protonation at sulfur gives a S-H bond syn to the Co-H bond. Formation of a cobalt-dihydrogen [1Br(CoH2)](-) intermediate is calculated to occur via a homocoupling (H(•) + H(•) → H2) step with a free energy of activation of 5.9 kcal/mol in solution (via C-PCM approach). PMID:26598074

  2. Sputtering of cobalt and chromium by argon and xenon ions near the threshold energy region

    NASA Technical Reports Server (NTRS)

    Handoo, A. K.; Ray, P. K.

    1993-01-01

    Sputtering yields of cobalt and chromium by argon and xenon ions with energies below 50 eV are reported. The targets were electroplated on copper substrates. Measurable sputtering yields were obtained from cobalt with ion energies as low as 10 eV. The ion beams were produced by an ion gun. A radioactive tracer technique was used for the quantitative measurement of the sputtering yield. Co-57 and Cr-51 were used as tracers. The yield-energy curves are observed to be concave, which brings into question the practice of finding threshold energies by linear extrapolation.

  3. Skin reactivity to metallic cobalt in patients with a positive patch test to cobalt chloride.

    PubMed

    de Fine Olivarius, F; Menné, T

    1992-10-01

    458 consecutive patients were patch tested with a metallic cobalt disc as a supplement to the standard series. 23 patients had a positive reaction to CoCl2 1% pet. Of these, 19 were tested with the cobalt disc. 11 had a positive reaction and 5 a questionable reaction. There were no positive reactions to the cobalt disc in patients with a negative patch test to CoCl2 1% pet. Patch testing with CoCl2 1% pet. diagnoses all patients with allergy to metallic cobalt, but the test method is limited by a high number of irritant and questionable reactions. PMID:1451489

  4. Magnetic hyperthermia heating of cobalt ferrite nanoparticles prepared by low temperature ferrous sulfate based method

    NASA Astrophysics Data System (ADS)

    Yadavalli, Tejabhiram; Jain, Hardik; Chandrasekharan, Gopalakrishnan; Chennakesavulu, Ramasamy

    2016-05-01

    A facile low temperature co-precipitation method for the synthesis of crystalline cobalt ferrite nanostructures using ferrous sulfate salt as the precursor has been discussed. The prepared samples were compared with nanoparticles prepared by conventional co-precipitation and hydrothermal methods using ferric nitrate as the precursor. X-ray diffraction studies confirmed the formation of cubic spinel cobalt ferrites when dried at 110 °C as opposed to conventional methods which required higher temperatures/pressure for the formation of the same. Field emission scanning electron microscope studies of these powders revealed the formation of nearly spherical nanostructures in the size range of 20-30 nm which were comparable to those prepared by conventional methods. Magnetic measurements confirmed the ferromagnetic nature of the cobalt ferrites with low magnetic remanance. Further magnetic hyperthermia studies of nanostructures prepared by low temperature method showed a rise in temperature to 50 °C in 600 s.

  5. Electrochemical characterization of cobalt-encapsulated nickel as cathodes for MCFC

    NASA Astrophysics Data System (ADS)

    Durairajan, Anand; Colon-Mercado, Hector; Haran, Bala; White, Ralph; Popov, Branko

    The stability of the NiO cathodes in molten carbonate fuel cell (MCFC) has been improved through microencapsulation of the NiO cathode with nanostructured Co. Cobalt was deposited on the NiO cathode using an electroless deposition process. The electrochemical oxidation behavior of the Co-coated electrodes is similar to that of the bare NiO cathode. The cobalt-coated electrodes have a lower solubility in the molten carbonate melt when compared to bare nickel oxide electrodes in the presence of cathode gas. The solubility decreased more than 50% due to microencapsulation with cobalt. The thermal oxidation rate was also lower in case of the cobalt-encapsulated electrode. Impedance data from the modified electrode indicate that the oxygen reduction reaction depended inversely on the CO 2 and directly on the oxygen partial pressures respectively suggesting a similar reaction mechanism to that of nickel oxide. The results indicated that cobalt-encapsulated NiO is a viable solution in the development of alternate cathodes for MCFC applications.

  6. Controlled cobalt doping in biogenic magnetite nanoparticles.

    PubMed

    Byrne, J M; Coker, V S; Moise, S; Wincott, P L; Vaughan, D J; Tuna, F; Arenholz, E; van der Laan, G; Pattrick, R A D; Lloyd, J R; Telling, N D

    2013-06-01

    Cobalt-doped magnetite (CoxFe3 -xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe(2+) site with Co(2+), with up to 17 per cent Co substituted into tetrahedral sites. PMID:23594814

  7. 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].

  8. 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}.

  9. Nanocrystalline cobalt oxides for carbon nanotube growth

    NASA Astrophysics Data System (ADS)

    Guo, Kun; Jayatissa, Ahalapitiya H.; Jayasuriya, Ambalangodage C.

    2007-09-01

    Thin Films of nanocrystalline cobalt oxide were formed by sol-gel method. Structure, optical properties and surface properties of these films were investigated by numerous characterization techniques. These films were successfully fabricated on glass substrates below 500°C. . Micropatterns of cobalt oxide thin films were also fabricated on glass and silicon substrates by employing a lift-off method. Crystal size of these nanocrystalline cobalt films could be successfully controllable by varying the amount of cobalt precursors and number of layers. These films were used as the seeding layers for carbon nanotube growth in a CVD process By changing the concentration of monomer precursors in the solgel coating solutions, different size nanoclusters hence different size carbon nanotubes could be synthesized in CVD process. This method can be used for controlled growth of carbon nanotubes for many different applications. In this paper, detail of these experimental results will be presented.

  10. Verification timer for AECL 780 Cobalt unit.

    PubMed

    Smathers, J B; Holly, F E

    1984-05-01

    To obtain verification of the proper time setting of the motorized run down timer for a AECL 780 Cobalt Unit, a digital timer is described, which can be added to the system for under $300. PMID:6735762

  11. Role of cobalt in nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Jarrett, R.; Barefoot, J.; Tien, J.; Sanchez, J.

    1982-01-01

    The effect of cobalt or substituting for cobalt on the mechanical properties of nickel-based superalloys is discussed. Waspaloy, UDIMET 700, and NIMONIC 115, which are representative of Ni-Cr-Co-Al-Ti-Mo superalloys having different gamma prime contents which are strengthened by a heavily alloyed matrix, coherent gamma prime precipitates, and carbides at the grain boundaries. Microstructure and in situ and extracted phase STEM micro-analysis were used to evaluate the three alloys.

  12. Photorelease and Cellular Delivery of Mitocurcumin from Its Cytotoxic Cobalt(III) Complex in Visible Light.

    PubMed

    Garai, Aditya; Pant, Ila; Banerjee, Samya; Banik, Bhabatosh; Kondaiah, Paturu; Chakravarty, Akhil R

    2016-06-20

    Ternary cobalt(III) complexes of curcumin (Hcur) and mitocurcumin [Hmitocur, a dicationic bis(triphenylphosphonium) derivative of curcumin] having a tetradentate phenolate-based ligand (H2L), namely, [Co(cur)(L)] (1) and [Co(mitocur)(L)]Cl2 (2), were prepared and structurally characterized, and their photoinduced cytotoxicity was studied. The diamagnetic cobalt(III) complexes show an irreversible Co(III)-Co(II) redox response and a quasireversible curcuminoid-based reduction near -1.45 and -1.74 V SCE, respectively, in DMF/0.1 M [(n)Bu4N](ClO4). The complexes exhibit a curcumin/mitocurcumin-based absorption band near 420 nm. Complex 1 was structurally characterized by X-ray crystallography. The structure contains the metal in a CoN2O4 distorted octahedral coordination arrangement with curcumin binding to the metal in its enolic form. Binding to cobalt(III) increases the hydrolytic stability of curcumin. Complex 2, having a dicationic curcuminoid, shows significant cellular uptake and photoinduced cytotoxicity compared to its curcumin analogue 1. The dicationic cobalt(III) complex 2 has significantly better cellular uptake and bioactivity than the neutral species 1. Complex 2 with mitochondrial localization releases the mitocurcumin dye upon exposure to visible light (400-700 nm) in human breast cancer MCF-7 cells through photoreduction of cobalt(III) to cobalt(II). Complex 2 displays a remarkable photodynamic therapy (PDT) effect, giving an IC50 value of ∼3.9 μM in visible light (400-700 nm) in MCF-7 cells while being much less toxic in the dark (>50 μM). The released mitocurcumin acts as a phototoxin, generating intracellular reactive oxygen species (ROSs). The overall process leads to light-controlled delivery of a curcuminoid (mitocur) into the tumor cells while the dye alone suffers from hydrolytic instability and poor bioavailability. PMID:27244480

  13. [Are the cobalt hip prosthesis dangerous?].

    PubMed

    Mistretta, Virginie; Kurth, William; Charlier, Corinne

    The placement of a hip prosthesis is one of the most common orthopedic surgical procedures. Some implants contain metal and are therefore capable of releasing metal particles like cobalt in patients who wear metal prostheses. Cobalt can be responsible of local toxicity (including metallosis, hypersensitivity reaction, and benign tumor) or systemic toxicity (including cardiomyopathy, polycythemia, hypothyroidism, and neurological disorders). To monitor potential toxicity of metal hip prostheses, an annual monitoring of patients implanted is recommended and includes clinical examination, radiological examination and blood cobalt determination. The cobalt concentration in blood allows to estimate the risk of toxicity and to evaluate the performance of the implant. The currently recommended threshold value is equal to 7 µg of cobalt per liter of blood. Our study, conducted on 251 patients over a period of 4 years, has shown that the cobalt concentration average was 2.51 µg/l in blood, with 51 patients having a cobaltemia higher than the threshold of 7 µg/l. PMID:27615181

  14. The standard enthalpies of combustion and formation of crystalline cobalt tetrakis(4-metoxyphenyl)porphin complex

    NASA Astrophysics Data System (ADS)

    Tarasov, R. P.; Volkov, A. V.; Bazanov, M. I.; Semeikin, A. S.

    2009-05-01

    The energy of combustion of cobalt tetrakis(4-metoxyphenyl)porphin was determined in an isothermic-shell liquid calorimeter with a stationary calorimetric bomb. The standard enthalpies of combustion and formation of the complex were calculated, -Δ c H o = 27334.06 ± 50.98 kJ/mol and Δf H o = 3062.90 ± 50.97 kJ/mol.

  15. 40 CFR 415.650 - Applicability; description of the cobalt salts production subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... cobalt salts production subcategory. 415.650 Section 415.650 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Cobalt Salts Production Subcategory § 415.650 Applicability; description of the cobalt... cobalt salts....

  16. 40 CFR 415.650 - Applicability; description of the cobalt salts production subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... cobalt salts production subcategory. 415.650 Section 415.650 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Cobalt Salts Production Subcategory § 415.650 Applicability; description of the cobalt... cobalt salts....

  17. 40 CFR 415.650 - Applicability; description of the cobalt salts production subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... cobalt salts production subcategory. 415.650 Section 415.650 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Cobalt Salts Production Subcategory § 415.650 Applicability; description of the cobalt... cobalt salts....

  18. 40 CFR 415.650 - Applicability; description of the cobalt salts production subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... cobalt salts production subcategory. 415.650 Section 415.650 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Cobalt Salts Production Subcategory § 415.650 Applicability; description of the cobalt... cobalt salts....

  19. 40 CFR 415.650 - Applicability; description of the cobalt salts production subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... cobalt salts production subcategory. 415.650 Section 415.650 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Cobalt Salts Production Subcategory § 415.650 Applicability; description of the cobalt... cobalt salts....

  20. Synergetic interactions improve cobalt leaching from lithium cobalt oxide in microbial fuel cells.

    PubMed

    Huang, Liping; Li, Tianchi; Liu, Chuan; Quan, Xie; Chen, Lijie; Wang, Aijie; Chen, Guohua

    2013-01-01

    Cobalt leaching from lithium cobalt oxide is a promising reduction process for recovery of cobalt and recycle of spent lithium ion batteries, but suffers from consumption of large amount of reductants and energy, and generation of excess secondary polluted sludge. Thus, effective and environmental friendly processes are needed to improve the existing process limitations. Here we reported microbial fuel cells (MFCs) to effectively reduce Co(III) in lithium cobalt oxide with concomitant energy generation. There was a synergetic interaction in MFCs, leading to a more rapid Co(III) leaching at a rate 3.4 times the sum of rates by conventional chemical processes and no-acid controls. External resistor, solid/liquid ratio, solution conductivity, pH and temperature affected system performance. This study provides a new process for recovery of cobalt and recycle of spent lithium ion batteries with concomitant energy generation from MFCs. PMID:23211478

  1. Decrease in hepatic cytochrome P-450 by cobalt. Evidence for a role of cobalt protoporphyrin.

    PubMed Central

    Sinclair, J F; Sinclair, P R; Healey, J F; Smith, E L; Bonkowsky, H L

    1982-01-01

    Exposure of cultured chick-embryo hepatocytes to increasing concentrations of CoCl2 in the presence of allylisopropylacetamide results in formation of cobalt protoporphyrin, with a reciprocal decrease in haem and cytochrome P-450. Treatment of rats with CoCl2 (84 mumol/kg) and 5-aminolaevulinate (0.2 mmol/kg) also results in formation of cobalt protoporphyrin and a decrease in cytochrome P-450 in the liver. Hepatic microsomal fractions from rats treated with phenobarbital, CoCl2 and 5-aminolaevulinate were analysed by polyacrylamide gel electrophoresis. Cobalt protoporphyrin was associated mainly with proteins of 50000-53000 mol.wt. The results suggest that the formation of cobalt protoporphyrin occurred at the expense of the synthesis of haem, leading to a decrease in cytochrome P-450. Furthermore, the cobalt protoporphyrin that was formed may itself have been incorporated into apocytochrome P-450. Images Fig. 2. PMID:7115319

  2. Synthesis of Samarium Cobalt Nanoblades

    SciTech Connect

    Darren M. Steele

    2010-08-25

    As new portable particle acceleration technologies become feasible the need for small high performance permanent magnets becomes critical. With particle accelerating cavities of a few microns, the photonic crystal fiber (PCF) candidate demands magnets of comparable size. To address this need, samarium cobalt (SmCo) nanoblades were attempted to be synthesized using the polyol process. Since it is preferable to have blades of 1-2 {micro}m in length, key parameters affecting size and morphology including method of stirring, reaction temperature, reaction time and addition of hydroxide were examined. Nanoparticles consisting of 70-200 nm spherical clusters with a 3-5 nm polyvinylpyrrolidone (PVP) coating were synthesized at 285 C and found to be ferromagnetic. Nanoblades of 25nm in length were observed at the surface of the nanoclusters and appeared to suggest agglomeration was occurring even with PVP employed. Morphology and size were characterized using a transmission electron microscope (TEM). Powder X-Ray Diffraction (XRD) analysis was conducted to determine composition but no supportive evidence for any particular SmCo phase has yet been observed.

  3. One-pot laser-assisted synthesis of porous carbon with embedded magnetic cobalt nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghimbeu, Camélia Matei; Sopronyi, Mihai; Sima, Felix; Delmotte, Luc; Vaulot, Cyril; Zlotea, Claudia; Paul-Boncour, Valérie; Le Meins, Jean-Marc

    2015-05-01

    A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid) independent of a catalyst presence. The influence of three metallic salts (acetate, nitrate and chloride) on the phenolic resin and carbon characteristics (structure, texture and particle size/distribution) was systematically studied. When exposed to UV laser, the metallic salt exhibited a strong influence on the particle size and distribution in the carbon matrix rather than on the textural carbon properties. Using cobalt acetate, very small (3.5 nm) and uniformly dispersed particles were obtained by this simple, fast and green one-pot synthesis approach. An original combined 13C CP-MAS and DP-DEC solid state NMR spectroscopy analysis allowed to determine the structure of phenolic resins as well as the location of the cobalt salt in the resin. Complementarily, the 1H solid-state and relaxation NMR provided unique insights into the rigidity (cross-linking) of the phenolic resin and dispersion of the cobalt salt. The magnetic properties of cobalt nanoparticles were found to be size-dependent: large Co nanoparticles (~50 nm) behave as bulk Co whereas small Co nanoparticles are superparamagnetic.A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid

  4. Cobalt: A vital element in the aircraft engine industry

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1981-01-01

    Recent trends in the United States consumption of cobalt indicate that superalloys for aircraft engine manufacture require increasing amounts of this strategic element. Superalloys consume a lion's share of total U.S. cobalt usage which was about 16 million pounds in 1980. In excess of 90 percent of the cobalt used in this country was imported, principally from the African countries of Zaire and Zambia. Early studies on the roles of cobalt as an alloying element in high temperature alloys concentrated on the simple Ni-Cr and Nimonic alloy series. The role of cobalt in current complex nickel base superalloys is not well defined and indeed, the need for the high concentration of cobalt in widely used nickel base superalloys is not firmly established. The current cobalt situation is reviewed as it applies to superalloys and the opportunities for research to reduce the consumption of cobalt in the aircraft engine industry are described.

  5. One-pot laser-assisted synthesis of porous carbon with embedded magnetic cobalt nanoparticles.

    PubMed

    Ghimbeu, Camélia Matei; Sopronyi, Mihai; Sima, Felix; Delmotte, Luc; Vaulot, Cyril; Zlotea, Claudia; Paul-Boncour, Valérie; Le Meins, Jean-Marc

    2015-06-14

    A novel one-pot laser-assisted approach is reported herein for the synthesis of ordered carbons with embedded cobalt nanoparticles. The process is based on a UV pulsed laser exposure of an ethanolic solution consisting of green carbon precursors, a structure directing agent and a cobalt salt. Very short irradiation times (5 to 30 min) are only required to polymerize and cross-link carbon precursors (i.e. phloroglucinol and glyoxylic acid) independent of a catalyst presence. The influence of three metallic salts (acetate, nitrate and chloride) on the phenolic resin and carbon characteristics (structure, texture and particle size/distribution) was systematically studied. When exposed to UV laser, the metallic salt exhibited a strong influence on the particle size and distribution in the carbon matrix rather than on the textural carbon properties. Using cobalt acetate, very small (3.5 nm) and uniformly dispersed particles were obtained by this simple, fast and green one-pot synthesis approach. An original combined (13)C CP-MAS and DP-DEC solid state NMR spectroscopy analysis allowed to determine the structure of phenolic resins as well as the location of the cobalt salt in the resin. Complementarily, the (1)H solid-state and relaxation NMR provided unique insights into the rigidity (cross-linking) of the phenolic resin and dispersion of the cobalt salt. The magnetic properties of cobalt nanoparticles were found to be size-dependent: large Co nanoparticles (∼50 nm) behave as bulk Co whereas small Co nanoparticles are superparamagnetic. PMID:25981107

  6. Equilibrium phase boundary between hcp-cobalt and fcc-cobalt

    NASA Astrophysics Data System (ADS)

    Cynn, Hyunchae; Lipp, Magnus J.; Evans, William J.; Baer, Bruce J.

    In 2000 (Yoo et al., PRL), fcc-cobalt was reported as a new high pressure phase transforming from ambient hcp-cobalt starting at around 105 GPa and 300 K. Both cobalts coexist up to 150 GPa and thereafter only fcc-cobalt was found to be the only stable phase to 200 GPa. Our recent synchrotron x-ray diffraction data on cobalt are at odds with the previous interpretation. We will present our new finding and elaborate on our understanding in terms of the equilibrium phase boundary of cobalt. We will also compare our previous work on xenon (Cynn et al., 2001, PRL) with our new results on cobalt. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Portions of this work were performed at HPCAT (Sector 16), APS, Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Award No. DENA0001974 and DOE-BES under Award No. DE-FG02-99ER45775. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

  7. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium...

  8. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  9. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  10. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium...

  11. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  12. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  13. Palladium-cobalt particles as oxygen-reduction electrocatalysts

    DOEpatents

    Adzic, Radoslav; Huang, Tao

    2009-12-15

    The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

  14. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium-cobalt-aluminum oxide. 73.1015 Section 73... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1015 Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide is a blue-green pigment obtained by calcining...

  15. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium...

  16. Cobalt and marine redox evolution

    NASA Astrophysics Data System (ADS)

    Swanner, Elizabeth D.; Planavsky, Noah J.; Lalonde, Stefan V.; Robbins, Leslie J.; Bekker, Andrey; Rouxel, Olivier J.; Saito, Mak A.; Kappler, Andreas; Mojzsis, Stephen J.; Konhauser, Kurt O.

    2014-03-01

    Cobalt (Co) is a bio-essential trace element and limiting nutrient in some regions of the modern oceans. It has been proposed that Co was more abundant in poorly ventilated Precambrian oceans based on the greater utilization of Co by anaerobic microbes relative to plants and animals. However, there are few empirical or theoretical constraints on the history of seawater Co concentrations. Herein, we present a survey of authigenic Co in marine sediments (iron formations, authigenic pyrite and bulk euxinic shales) with the goal of tracking changes in the marine Co reservoir throughout Earth's history. We further provide an overview of the modern marine Co cycle, which we use as a platform to evaluate how changes in the redox state of Earth's surface were likely to have affected marine Co concentrations. Based on sedimentary Co contents and our understanding of marine Co sources and sinks, we propose that from ca. 2.8 to 1.8 Ga the large volume of hydrothermal fluids circulating through abundant submarine ultramafic rocks along with a predominantly anoxic ocean with a low capacity for Co burial resulted in a large dissolved marine Co reservoir. We tentatively propose that there was a decrease in marine Co concentrations after ca. 1.8 Ga resulting from waning hydrothermal Co sources and the expansion of sulfide Co burial flux. Changes in the Co reservoir due to deep-water ventilation in the Neoproterozoic, if they occurred, are not resolvable with the current dataset. Rather, Co enrichments in Phanerozoic euxinic shales deposited during ocean anoxic events (OAE) indicate Co mobilization from expanded anoxic sediments and enhanced hydrothermal sources. A new record of marine Co concentrations provides a platform from which we can reevaluate the role that environmental Co concentrations played in shaping biological Co utilization throughout Earth's history.

  17. Nickel cobalt phosphorous low stress electroplating

    NASA Technical Reports Server (NTRS)

    Engelhaupt, Darell E. (Inventor); Ramsey, Brian D. (Inventor)

    2002-01-01

    An electrolytic plating process is provided for electrodepositing a nickel or nickel cobalt alloy which contains at least about 2% to 25% by atomic volume of phosphorous. The process solutions contains nickel and optionally cobalt sulfate, hypophosphorous acid or a salt thereof, boric acid or a salt thereof, a monodentate organic acid or a salt thereof, and a multidentate organic acid or a salt thereof. The pH of the plating bath is from about 3.0 to about 4.5. An electroplating process is also provided which includes electroplating from the bath a nickel or nickel cobalt phosphorous alloy. This process can achieve a deposit with high microyield of at least about 84 kg/mm.sup.2 (120 ksi) and a density lower than pure nickel of about 8.0 gm/cc. This process can be used to plate a deposit of essentially zero stress at plating temperatures from ambient to 70.degree. C.

  18. Rapid phase synthesis of nanocrystalline cobalt ferrite

    SciTech Connect

    Shanmugavel, T.; Raj, S. Gokul; Rajarajan, G.; Kumar, G. Ramesh

    2014-04-24

    Synthesis of single phase nanocrystalline Cobalt Ferrite (CoFe{sub 2}O{sub 4}) was achieved by single step autocombustion technique with the use of citric acid as a chelating agent in mono proportion with metal. Specimens prepared with this method showed significantly higher initial permeability's than with the conventional process. Single phase nanocrystalline cobalt ferrites were formed at very low temperature. Surface morphology identification were carried out by transmission electron microscopy (TEM) analysis. The average grain size and density at low temperature increased gradually with increasing the temperature. The single phase formation is confirmed through powder X-ray diffraction analysis. Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behaviors. Temperature dependent magnetization results showed improved behavior for the nanocrystalline form of cobalt ferrite when compared to the bulk nature of materials synthesized by other methods.

  19. Controlled cobalt doping in biogenic magnetite nanoparticles

    PubMed Central

    Byrne, J. M.; Coker, V. S.; Moise, S.; Wincott, P. L.; Vaughan, D. J.; Tuna, F.; Arenholz, E.; van der Laan, G.; Pattrick, R. A. D.; Lloyd, J. R.; Telling, N. D.

    2013-01-01

    Cobalt-doped magnetite (CoxFe3 −xO4) nanoparticles have been produced through the microbial reduction of cobalt–iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites. PMID:23594814

  20. International strategic minerals inventory summary report; cobalt

    USGS Publications Warehouse

    Crockett, R.N.; Chapman, G.R.; Forrest, M.D.

    1987-01-01

    Major world resources of cobalt are described in this summary report of information in the International Strategic Minerals Inventory {ISMI}. ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, and the United States of America. This report, designed to be of benefit to policy analysts, contains two parts. Part I presents an overview of the resources and potential supply of cobalt on the basis of inventory information. Part II contains tables of some of the geologic information and mineral-resource and production data that were collected by ISMI participants.

  1. Cation distributions on rapidly solidified cobalt ferrite

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

    1990-01-01

    The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

  2. Cobalt plaque therapy of posterior uveal melanomas

    SciTech Connect

    Shields, J.A.; Augsburger, J.J.; Brady, L.W.; Day, J.L.

    1982-10-01

    One hundred patients with choroidal melanomas who were treated by the authors with cobalt plaque radiotherapy were analyzed with regard to tumor regression, visual results, complications, and mortality rate. The follow-up period at the time of this writing ranged from one to five years. These preliminary observations indicate that cobalt plaque radiotherapy induces tumor regression in 96% of cases, preserves useful vision in many cases and has fewer complications during the one- to five-year follow-up period than previously believed.

  3. Effect of cobalt on the primary productivity of Spirulina platensis

    SciTech Connect

    Sharma, R.M.; Panigrahi, S.; Azeez, P.A.

    1987-10-01

    Cobalt, a micronutrient for biological organisms, is a metal of wide use. Main sources of Co to the environment are combustion of fossil fuels, smelters, cobalt processing facilities, sewage and industrial wastes. Atomic power plants and nuclear weapon detonations form an important source of radioisotopes of this metal to the environment. Cobalt has been included in the 14 toxic trace elements of critical importance from the point of view of environmental pollution and health hazards. Cobalt deficiency leads to diseases like stunted growth. At toxic level, Co inhibits heme biosynthesis and enzyme activities. The present study reports the effect of cobalt on biomass productivity of blue-green alga Spirulina platensis.

  4. Isolation, identification and characterization of indigenous fungi for bioremediation of hexavalent chromium, nickel and cobalt

    NASA Astrophysics Data System (ADS)

    Hernahadini, Nelis; Suhandono, Sony; Choesin, Devi N.; Chaerun, Siti K.; Kadarusman, Ade

    2014-03-01

    Waste from nickel mining of Sorowako in South Sulawesi contains hexavalent chromium, nickel and cobalt metals in high concentration and may have a negative impact to the environment. Common waste treatment systems such as chemical treatment using a reducing reagent may still have a negative impact. Bioremediation using fungi or bacteria becomes more popular because it is an environmentally friendly alternative. The purposes of this study are to isolate and identify indigenous fungi that are resistant to heavy metals (hexavalent chromium, nickel, and cobalt) and are capable of reducing the concentration of metals in mining wastes. Ten fungal isolates were successfully isolated from the soils and pond sediments in the area of nickel mining in Sorowako. Selection of superior isolate was carried out by growing all the isolates on PDA medium, which contained all of the three metals. One superior isolate was identified to be able to grow on medium with concentrations of 6400 ppm hexavalent chromium, 200 ppm nickel and 50 ppm cobalt. Molecular identification and phylogenetic studies of the isolate using fungal PCR primers developed to amplify the ITS (internal transcribed spacer) region showed that the isolate sequence was very close to Trichoderma atroviride with 99.8% similarity. Optimum incubation time for the uptake of hexavalent chromium was 3 days, nickel and cobalt was 5 days, respectively, with an optimum pH of 4.

  5. Embryotoxicity of cobalt ferrite and gold nanoparticles: a first in vitro approach.

    PubMed

    Di Guglielmo, Claudia; López, David Ramos; De Lapuente, Joaquín; Mallafre, Joan Maria Llobet; Suàrez, Miquel Borràs

    2010-09-01

    Nanoparticles (NPs) are emerging as promising biomedical tools thanks to their peculiar characteristics. Our purpose was to investigate the embryotoxicity of cobalt ferrite and gold NPs through the Embryonic Stem Cell Test (EST). The EST is an in vitro standard assay, which permits to classify substances as strongly, weakly or non-embryotoxic. Due to the particular physical-chemical nature of nanoparticles, we introduced a modification to the standard protocol exposing the Embryonic Stem Cells (ES-D3) to nanoparticles only during the first 5 days of the assay. Moreover, we proposed a method to discriminate and compare the embryotoxicity of the substances within the weakly embryotoxic range. Our ID(50) results permit to classify cobalt ferrite nanoparticles coated with gold and silanes as non-embryotoxic. The remaining nanoparticles have been classified as weakly embryotoxic in this decreasing order: gold salt (HAuCl(4).3H(2)O)>cobalt ferrite salt (CoFe(2)O(4))>cobalt ferrite nanoparticles coated with silanes (Si-CoFe)>gold nanoparticles coated with hyaluronic acid (HA-Au). PMID:20566333

  6. Equilibrium sorption of cobalt, cesium, and strontium on Bandelier Tuff: analysis of alternative mathematical modeling

    SciTech Connect

    Polzer, W.L.; Fuentes, H.R.; Essington, E.H.; Roensch, F.R.

    1985-01-01

    Sorption isotherms are derived from batch equilibrium data for cobalt, cesium and strontium on Bandelier Tuff. Experiments were conducted at an average temperature of 23/sup 0/C and equilibrium was defined at 48 hours. The solute concentrations ranged from 0 to 500 mg/L. The radioactive isotopes /sup 60/Co, /sup 137/Cs, and /sup 85/Sr were used to trace the sorption of the stable solutes. The Linear, Langmuir, Freundlich and a Modified Freundlich isotherm equations are evaluated. The Modified Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of the three solutes. The empirical constants derived from the Modified Freundlich isotherm equation indicate that under dynamic flow conditions strontium will move most rapidly and cobalt least rapidly. On the other hand, chemical dispersion will be greatest for cesium and least for strontium. Hill Plots of the sorption data suggest that in the region of low saturation sorption of all three solutes is impeded by interactions among sorption sites; cobalt exhibits the greatest effect of interactions and strontium shows only a minimal effect. In the saturation region of 50% or more, sorption of cobalt is enhanced slightly by interactions among sorption sites whereas sorption of cesium and strontium appears to be independent of site interactions. 9 references, 4 figures, 2 tables.

  7. Hydrometallurgical separation of rare earth elements, cobalt and nickel from spent nickel-metal-hydride batteries

    NASA Astrophysics Data System (ADS)

    Rodrigues, Luiz Eduardo Oliveira Carmo; Mansur, Marcelo Borges

    The separation of rare earth elements, cobalt and nickel from NiMH battery residues is evaluated in this paper. Analysis of the internal content of the NiMH batteries shows that nickel is the main metal present in the residue (around 50% in weight), as well as potassium (2.2-10.9%), cobalt (5.1-5.5%), rare earth elements (15.3-29.0%) and cadmium (2.8%). The presence of cadmium reveals that some Ni-Cd batteries are possibly labeled as NiMH ones. The leaching of nickel and cobalt from the NiMH battery powder with sulfuric acid is efficient; operating variables temperature and concentration of H 2O 2 has no significant effect for the conditions studied. A mixture of rare earth elements is separated by precipitation with NaOH. Finally, solvent extraction with D2EHPA (di-2-ethylhexyl phosphoric acid) followed by Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) can separate cadmium, cobalt and nickel from the leach liquor. The effect of the main operating variables of both leaching and solvent extraction steps are discussed aiming to maximize metal separation for recycling purposes.

  8. Magnetization dynamics of cobalt grown on graphene

    SciTech Connect

    Berger, A. J.; White, S. P.; Adur, R.; Pu, Y.; Hammel, P. C.; Amamou, W.; Kawakami, R. K.

    2014-05-07

    Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which has demonstrated promising results in a variety of material systems. This technique utilizes the resonant precession of magnetization in a ferromagnet to inject spin into an adjacent non-magnetic material. Spin pumping into graphene is attractive on account of its exceptional spin transport properties. This article reports on FMR characterization of cobalt grown on chemical vapor deposition graphene and examines the validity of linewidth broadening as an indicator of spin pumping. In comparison to cobalt samples without graphene, direct contact cobalt-on-graphene exhibits increased FMR linewidth—an often used signature of spin pumping. Similar results are obtained in Co/MgO/graphene structures, where a 1 nm MgO layer acts as a tunnel barrier. However, magnetometry, magnetic force microscopy, and Kerr microscopy measurements demonstrate increased magnetic disorder in cobalt grown on graphene, perhaps due to changes in the growth process and an increase in defects. This magnetic disorder may account for the observed linewidth enhancement due to effects such as two-magnon scattering or mosaicity. As such, it is not possible to conclude successful spin injection into graphene from FMR linewidth measurements alone.

  9. Cobalt processing - flask positioner location sensing system

    SciTech Connect

    Braun, P.F.

    1986-01-01

    Canada deuterium uranium (CANDU) reactors offer unique opportunities for economical production of /sup 60/Co in the adjuster rods used for xenon override and maximization of core output. Cobalt is effectively a by-product in CANDU reactors with the standards stainless steel adjuster rods replaced with cobalt adjuster rods. The Flask Positioner unit is a part of the cobalt adjuster element processing system (CAEPS) equipment which is used for removing irradiated cobalt adjuster elements from the reactor and safely transporting them to the irradiated fuel bay, where they are dismantled and prepared for shipment. The flask positioner equipment is similar to a crane, carries the CAEPS flask and locates it in an accurate position concentric with any adjuster site centerline. This enables the required operations for safe transfer of the irradiated adjuster element into the flask. The positioner is located above the reactivity mechanism deck. The CAEPS system has been made operational on several CANDU reactors. The location sensing system has been demonstrated to work very satisfactorily on all installations.

  10. Localized comedo formation after cobalt irradiation

    SciTech Connect

    Myskowski, P.L.; Safai, B.

    1981-10-01

    Following Cobalt-60 irradiation for a left frontotemporal tumor, a 61-year-old woman developed comedones on the forehead. These changes responded to conventional acne therapy with retinoic acid. Multiple acneigenic factors were implicated in the pathogenesis of her lesions.

  11. Sintered diamond compacts using metallic cobalt binders

    NASA Technical Reports Server (NTRS)

    Libby, W. F.; Katzman, H.

    1972-01-01

    Method is developed for sintering diamond powder which uses metallic cobalt as binder. Present samples show maximum microhardness of over 3000 kg/sq mm on Knoop scale. Material may be used as hard surface coating or may compete with cubic boron nitride as abrasive grain.

  12. Magnetization dynamics of cobalt grown on graphene

    NASA Astrophysics Data System (ADS)

    Berger, A. J.; Amamou, W.; White, S. P.; Adur, R.; Pu, Y.; Kawakami, R. K.; Hammel, P. C.

    2014-05-01

    Ferromagnetic resonance (FMR) spin pumping is a rapidly growing field which has demonstrated promising results in a variety of material systems. This technique utilizes the resonant precession of magnetization in a ferromagnet to inject spin into an adjacent non-magnetic material. Spin pumping into graphene is attractive on account of its exceptional spin transport properties. This article reports on FMR characterization of cobalt grown on chemical vapor deposition graphene and examines the validity of linewidth broadening as an indicator of spin pumping. In comparison to cobalt samples without graphene, direct contact cobalt-on-graphene exhibits increased FMR linewidth—an often used signature of spin pumping. Similar results are obtained in Co/MgO/graphene structures, where a 1 nm MgO layer acts as a tunnel barrier. However, magnetometry, magnetic force microscopy, and Kerr microscopy measurements demonstrate increased magnetic disorder in cobalt grown on graphene, perhaps due to changes in the growth process and an increase in defects. This magnetic disorder may account for the observed linewidth enhancement due to effects such as two-magnon scattering or mosaicity. As such, it is not possible to conclude successful spin injection into graphene from FMR linewidth measurements alone.

  13. Water splitting: Taking cobalt in isolation

    NASA Astrophysics Data System (ADS)

    Wang, Aiqin; Zhang, Tao

    2016-01-01

    The sustainable production of hydrogen is key to the delivery of clean energy in a hydrogen economy; however, lower-cost alternatives to platinum electrocatalysts are needed. Now, isolated, earth-abundant cobalt atoms dispersed over nitrogen-doped graphene are shown to efficiently electrolyse water to generate hydrogen.

  14. Controlled cobalt doping of magnetosomes in vivo.

    PubMed

    Staniland, Sarah; Williams, Wyn; Telling, Neil; Van Der Laan, Gerrit; Harrison, Andrew; Ward, Bruce

    2008-03-01

    Magnetotactic bacteria biomineralize iron into magnetite (Fe3O4) nanoparticles that are surrounded by lipid vesicles. These 'magnetosomes' have considerable potential for use in bio- and nanotechnological applications because of their narrow size and shape distribution and inherent biocompatibility. The ability to tailor the magnetic properties of magnetosomes by chemical doping would greatly expand these applications; however, the controlled doping of magnetosomes has so far not been achieved. Here, we report controlled in vivo cobalt doping of magnetosomes in three strains of the bacterium Magnetospirillum. The presence of cobalt increases the coercive field of the magnetosomes--that is, the field necessary to reverse their magnetization--by 36-45%, depending on the strain and the cobalt content. With elemental analysis, X-ray absorption and magnetic circular dichroism, we estimate the cobalt content to be between 0.2 and 1.4%. These findings provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties. PMID:18654488

  15. A cobalt-NHC complex as an improved catalyst for photochemical hydrogen evolution from water.

    PubMed

    Kawano, Ken; Yamauchi, Kosei; Sakai, Ken

    2014-09-01

    A macrocyclic N-heterocyclic carbene (NHC)-cobalt complex was found to act as an improved H2-evolving catalyst in a [Ru(bpy)3](2+)-sensitized photosystem using methylviologen as a redox acceptor (MV(2+) + e(-) → MV(+)˙, MV(2+) = N,N'-dimethyl-4,4'-bipyridinium), which provides a driving force of only 150 meV for H2 evolution at pH 5.0. PMID:25025392

  16. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells

    SciTech Connect

    Smith, Leah J.; Holmes, Amie L.; Kandpal, Sanjeev Kumar; Mason, Michael D.; Zheng, Tongzhang; Wise, John Pierce

    2014-08-01

    Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity. - Highlights: • Particulate and soluble cobalt are cytotoxic and genotoxic to human lung cells. • Soluble cobalt induces more cytotoxicity compared to particulate cobalt. • Soluble and particulate cobalt induce similar levels of genotoxicity. • Particle-cell contact is required for particulate cobalt-induced toxicity.

  17. Re-manufacture of cobalt-manganese-bromide as a liquid catalyst from spent catalyst containing cobalt generated from petrochemical processes via hydrometallurgy.

    PubMed

    Joo, Sung-Ho; Shin, Dong Ju; Oh, Chang Hyun; Wang, Jei-Pil; Shin, Shun Myung

    2016-11-15

    Cobalt and manganese have been the subject of individual separation studies because their fields of application are different. However, this study shows that high-value products can be manufactured in the form of a cobalt-manganese-bromide (CMB) liquid catalyst by simultaneously recovering cobalt and manganese. Na-bis-(2,4,4-tri-methyl-pentyl)phosphinic acid was employed in order to manufacture the CMB liquid catalyst from the spent catalyst generated from petroleum chemistry processes. The pH-isotherm, degree of saponification of solvent and separation factor values were investigated. ΔpH50 and separation factor values show that Co and Mn can be separated from impurities such as Mg and Ca. Further, the extraction stages and organic/aqueous ratio isotherms were investigated using counter-current simulation extraction batch tests. To prepare CMB from a loaded organic phase obtained in a stripping study using hydrogen bromide, the Co and Mn were completely stripped and concentrated by a factor of 6 using a 2M hydrogen bromide solution. When compared with manufactured and commercial CMB, the CMB liquid catalyst could be produced by supplying a shortage of Mn in the form of manganese bromide. Finally, the method of manufacture of CMB was subjected to a real pilot plant test. PMID:27391861

  18. Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction

    PubMed Central

    2013-01-01

    A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too. PMID:24229351

  19. Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction.

    PubMed

    Yuan, Xianxia; Hu, Xin-Xin; Ding, Xin-Long; Kong, Hai-Chuan; Sha, Hao-Dong; Lin, He; Wen, Wen; Shen, Guangxia; Guo, Zhi; Ma, Zi-Feng; Yang, Yong

    2013-01-01

    A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too. PMID:24229351

  20. Magnetization reversal studies in structurally tailored cobalt nanowires

    NASA Astrophysics Data System (ADS)

    Kaur, Daljit; Chaudhary, Sujeet; Pandya, Dinesh K.; Gupta, Rekha; Kotnala, R. K.

    2013-10-01

    Cobalt nanowires (NWs) having hcp crystal structure are structurally tailored for different preferred orientations (PO) of (0002), (101¯0), (112¯0) and (101¯1) by varying bath temperature and bath concentration in commercially available 50 nm pore diameter polycarbonate (PCT) and 20 nm pore diameter anodic alumina (AAO) membranes. The magnetization studies show orientation dependent competition of magneto-crystalline anisotropy with shape anisotropy. The large effective anisotropy, Keff (along longitudinal direction) of 1.42×106 erg/cc is observed in (0002) PO NWs, which changes sign (-1.50×106 erg/cc) in (101¯0) PO NWs. The angular dependence of coercivity [HC(θ)] in (0002) oriented Co NWs exhibits a non-monotonic behavior in both the 50 nm and 20 nm samples. The fitting of HC(θ) data reveals that the magnetization reversal mechanism initially takes place by curling and subsequently changes to coherent rotation mode after a certain transition angle, which is higher in case of denser NW array. This increase in transition angle can be attributed to the increased magneto-static interactions in the AAO membrane array having 103 times higher NW areal-density than that in PCT membrane array. Role of dipolar/ magnetostatic anisotropy studied by varying NW areal-density and NW diameter.

  1. Low-cobalt single crystal Rene 150

    NASA Technical Reports Server (NTRS)

    Scheuermann, C. M.

    1982-01-01

    The effects of cobalt content on a single crystal version of the advanced, high gamma prime content turbine airfoil alloy Rene 150 were investigated. Cobalt contents under investigation include 12 wt.% (composition level of Rene 150), 6 wt.%, and 0 wt.%. Preliminary test results are presented and compared with the properties of standard DS Rene 150. DTA results indicate that the liquidus goes through a maximum of about 1435 C near 6 wt.% Co. The solidus remains essentially constant at 1390 C with decreasing Co content. The gamma prime solvus appears to go through a minimum of about 1235 C near 6 wt.% Co content. Preliminary as-cast tensile and stress rupture results are presented along with heat treat schedules and future test plans.

  2. Creep-fatigue of low cobalt superalloys

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1982-01-01

    Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.

  3. Are cobaltates conventional? An ARPES viewpoint

    SciTech Connect

    Hasan, M.Z. . E-mail: mzhasan@Princeton.edu; Qian, D.; Foo, M.L.; Cava, R.J.

    2006-07-15

    Recently discovered class of cobaltate superconductors (Na{sub 0.3}CoO{sub 2}.nH{sub 2}O) is a novel realization of interacting quantum electron system in a triangular network with low-energy degrees of freedom. We employ angle-resolved photoemission spectroscopy to study the quasiparticle parameters in the parent superconductors. Results reveal a large hole-like Fermi surface generated by the crossing of heavy quasiparticles. The measured quasiparticle parameters collectively suggest two orders of magnitude departure from the conventional weak coupling (such as Al) Bardeen-Cooper-Schrieffer electron dynamics paradigm and unveils cobaltates as a rather hidden class of relatively high temperature superconductors. These parameters also form the basis for a microscopic Hamiltonian of the system.

  4. Hard Machinable Machining of Cobalt Super Alloys

    NASA Astrophysics Data System (ADS)

    Čep, Robert; Janásek, Adam; Petrů, Jana; Čepová, Lenka; Sadílek, Marek; Kratochvíl, Jiří

    2012-12-01

    The article deals with difficult-to-machine cobalt super alloys. The main aim is to test the basic properties of cobalt super alloys and propose suitable cutting materials and machining parameters under the designation 188 when machining. Although the development of technology in chipless machining such as moulding, precision casting and other manufacturing methods continues to advance, machining is still the leading choice for piece production, typical for energy and chemical engineering. Nowadays, super alloys are commonly used in turbine engines in regions that are subject to high temperatures, which require high strength, high temperature resistance, phase stability, as well as corrosion or oxidation resistance.

  5. Influence of cobalt on fermentative methylation.

    PubMed

    Claridge, C A; Rossomano, V Z; Buono, N S; Gourevitch, A; Lein, J

    1966-03-01

    Streptomyces rishiriensis produces at least five closely related antibiotics. Strain selection yielded a culture producing only the most active component, coumermycin A. Hydrolysis of this antibiotic by barium hydroxide yielded both 5-methyl-pyrrole-2-carboxylic acid and pyrrole-2-carboxylic acid, which could be separated by paper chromatography. Coumermycin A was thus shown to be two fractions, designated A(1) and A(2) depending upon the nature of the pyrrole carboxylic acid portion. The addition of cobalt to the fermentation medium at a level as low as 0.01 mug/ml shifted the fermentation exclusively to the production of coumermycin A(1). Other ions were ineffective, except nickel, whose activity could be explained by the presence of contaminating cobalt. PMID:5959861

  6. Interfacial Structure Dependent Spin Mixing Conductance in Cobalt Thin Films.

    PubMed

    Tokaç, M; Bunyaev, S A; Kakazei, G N; Schmool, D S; Atkinson, D; Hindmarch, A T

    2015-07-31

    Enhancement of Gilbert damping in polycrystalline cobalt thin-film multilayers of various thicknesses, overlayered with copper or iridium, was studied in order to understand the role of local interface structure in spin pumping. X-ray diffraction indicates that cobalt films less than 6 nm thick have strong fcc(111) texture while thicker films are dominated by hcp(0001) structure. The intrinsic damping for cobalt thicknesses above 6 nm is weakly dependent on cobalt thickness for both overlayer materials, and below 6 nm the iridium overlayers show higher damping enhancement compared to copper overlayers, as expected due to spin pumping. The interfacial spin mixing conductance is significantly enhanced in structures where both cobalt and iridium have fcc(111) structure in comparison to those where the cobalt layer has subtly different hcp(0001) texture at the interface. PMID:26274431

  7. The Idaho cobalt belt, northwestern United States — A metamorphosed Proterozoic exhalative ore district

    NASA Astrophysics Data System (ADS)

    Nold, J. L.

    1990-07-01

    where Proterozoic Roan sedimentary rocks contain stratiform copper-cobalt ore-bodies over a distance of more than 500 kilometers, and the Sheep Creek district of Meagher County, Montana, which contains strata-bound copper-cobalt mineralization. The Idaho cobalt belt is a strata-bound copper-cobalt district hosted by the Proterozoic Yellowjacket Formation and located in east-central Idaho within Lemhi County, approximately 40 kilometers west of Salmon, Idaho, northwestern United States (Fig. 1). Of the four main deposits described here (from southeast to northwest, the Iron Creek, Blackpine, Blackbird, and the Salmon Canyon deposits), the Blackbird mine is the most important in the district. It was discovered in 1893 and sporadically produced copper and cobalt until about 1960. The Yellowjacket Formation has undergone an increasing degree of metamorphism toward the northwest. The deposits are largely strata-bound in a belt over 50 km in length, strongly suggesting a syngenetic mode of origin. However, the proximity of the district to satellitic granitic plutons of the Idaho batholith has prompted many investigators to suggest an epigenetic hydrothermal origin (Anderson 1947 and Purdue 1975). Remobilization of some of the mineralization into veins at the Blackbird mine, where most of the previous work has been concentrated, has also suggested an epigenetic origin. A more district-wide view of the mineralization points to a strong degree of stratigraphic control.

  8. High-Spin Cobalt Hydrides for Catalysis

    SciTech Connect

    Holland, Patrick L.

    2013-08-29

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

  9. Atomically flat ultrathin cobalt ferrite islands.

    PubMed

    Martín-García, Laura; Quesada, Adrián; Munuera, Carmen; Fernández, Jose F; García-Hernández, Mar; Foerster, Michael; Aballe, Lucía; de la Figuera, Juan

    2015-10-21

    A route for fabricating structurally perfect cobalt ferrite magnetic nanostructures is demonstrated. Ultrathin islands of up to 100 μm(2) with atomically flat surfaces and free from antiphase boundaries are developed. The extremely low defect concentration leads to a robust magnetic order, even for thicknesses below 1 nm, and exceptionally large magnetic domains. This approach allows the evaluation of the influence of specific extrinsic effects on domain wall pinning. PMID:26306027

  10. Structure and magnetism of cobalt at high pressure and low temperature

    NASA Astrophysics Data System (ADS)

    Torchio, R.; Marini, C.; Kvashnin, Y. O.; Kantor, I.; Mathon, O.; Garbarino, G.; Meneghini, C.; Anzellini, S.; Occelli, F.; Bruno, P.; Dewaele, A.; Pascarelli, S.

    2016-07-01

    The magnetic and structural properties of cobalt were investigated under high pressure (160 GPa) and low temperature (50 K), by synchrotron K-edge x-ray magnetic circular dichroism and x-ray diffraction. A quasihydrostatic equation of state was measured up to 160 GPa. We found that uniaxial stress plays a role in the hexagonal close packed-face centered cubic (hcp-fcc) structural transition pressure. Also, our data provide the first experimental evidence that changes of the c /a ratio pressure derivative are related to the magnetic behavior. The complete extinction of ferromagnetism is observed above 130 GPa in a mixed hcp-fcc phase with no recovery upon cooling to 50 K, indicating that cobalt at 150 GPa is very likely nonmagnetic, i.e., characterized by zero local spin polarization. Density functional theory calculations point out that the K-edge x-ray magnetic circular dichroism (XMCD) signal is related to the 4 p orbital moment rather than to the total spin moment and allow us to get a deeper insight into the K-edge XMCD measurements interpretation. The combination of novel theoretical results and experimental outputs provides a detailed scenario of the structural and magnetic properties of cobalt at these extreme conditions answering some previously unsolved issues.

  11. Cobalt(II) Complex of a Diazoalkane Radical Anion.

    PubMed

    Bonyhady, Simon J; Goldberg, Jonathan M; Wedgwood, Nicole; Dugan, Thomas R; Eklund, Andrew G; Brennessel, William W; Holland, Patrick L

    2015-06-01

    β-Diketiminate cobalt(I) precursors react with diphenyldiazomethane to give a compound that is shown by computational studies to be a diazoalkane radical anion antiferromagnetically coupled to a high-spin cobalt(II) ion. Thermolysis of this complex results in formal N-N cleavage to give a cobalt(II) ketimide complex. Experimental evaluation of the potential steps in the mechanism suggests that free azine is a likely intermediate in this reaction. PMID:25986783

  12. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Cobaltous salts and its derivatives. 189.120... Generally Prohibited From Direct Addition or Use as Human Food § 189.120 Cobaltous salts and its derivatives. (a) Cobaltous salts are the chemicals, CoC4H6O4, CoCl2, and CoSO4.They have been used in...

  13. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Cobaltous salts and its derivatives. 189.120... Generally Prohibited From Direct Addition or Use as Human Food § 189.120 Cobaltous salts and its derivatives. (a) Cobaltous salts are the chemicals, CoC4H6O4, CoCl2, and CoSO4.They have been used in...

  14. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Cobaltous salts and its derivatives. 189.120... Generally Prohibited From Direct Addition or Use as Human Food § 189.120 Cobaltous salts and its derivatives. (a) Cobaltous salts are the chemicals, CoC4H6O4, CoCl2, and CoSO4.They have been used in...

  15. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Cobaltous salts and its derivatives. 189.120... Generally Prohibited From Direct Addition or Use as Human Food § 189.120 Cobaltous salts and its derivatives. (a) Cobaltous salts are the chemicals, CoC4H6O4, CoCl2, and CoSO4.They have been used in...

  16. Hot corrosion of low cobalt alloys

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.

    1982-01-01

    The hot corrosion attack susceptibility of various alloys as a function of strategic materials content are investigated. Preliminary results were obtained for two commercial alloys, UDIMET 700 and Mar-M 247, that were modified by varying the cobalt content. For both alloys the cobalt content was reduced in steps to zero. Nickel content was increased accordingly to make up for the reduced cobalt but all other constituents were held constant. Wedge bar test samples were produced by casting. The hot corrosion test consisted of cyclically exposing samples to the high velocity flow of combustion products from an air-fuel burner fueled with jet A-1 and seeded with a sodium chloride aqueous solution. The flow velocity was Mach 0.5 and the sodium level was maintained at 0.5 ppm in terms of fuel plus air. The test cycle consisted of holding the test samples at 900 C for 1 hour followed by 3 minutes in which the sample could cool to room temperature in an ambient temperature air stream.

  17. Atomic layer deposition of metallic cobalt

    NASA Astrophysics Data System (ADS)

    Kwon, Jinhee; Saly, Mark; Kanjolia, Ravi; Chabal, Yves; University of Texas at Dallas Collaboration; SAFC Collaboration

    2011-03-01

    Metallic cobalt has rich catalytic, electronic and magnetic properties, which makes it critical to have a better control of Co thin film deposition for various applications. This work focuses on the atomic layer deposition (ALD) of cobalt using (tertiarybutylallyl)cobalttricarbonyl (t BuAllyl)Co(CO)3 and dimethylhydrazine (DMHy) on H-terminated Si to uncover the growth mechanisms. The first pulse of (t BuAllyl)Co(CO)3 reacts with surface H--Si bonds completely, forming one monolayer of metallic silicide. In situ infrared absorption spectra show that further deposition of Co is made possible only after linear carbonyl groups which remain after the first (t BuAllyl)Co(CO)3 pulse as the surface ligand are removed by subsequent ALD cycles. Further ALD cycles give rise to metallic Co growth through ligand exchange after a nucleation period of 8--10 cycles. The derived growth rate of cobalt is 0.6 +/- 0.1 Å/cycle. The resultant Co film shows low concentration of carbon and nitrogen impurities in the bulk according to X-ray photoemission spectroscopy.

  18. Kinetics of cobalt cementation on zinc powder

    SciTech Connect

    Polcaro, A.M.; Palmas, S.; Dernini, S.

    1995-09-01

    The cementation process may be considered an interesting method to treat dilute solutions containing metal ions. The aim of the process may be either the removal of pollutant metals or the recovery of economically valuable metals such as Ag from spent photographic liquors. The kinetics of cobalt cementation on Zn powder from zinc sulfate concentrated solutions in the presence of copper and antimony ions was investigated in stirred tank reactors. The composition of the solutions was in the range usually utilized in industrial zinc electrowinning plants. The results showed that the reaction occurs by means of the formation of crystallization nuclei of noble metals on the zinc powder, followed by the cementation of cobalt ions on these newly-formed nuclei. Mass transfer to the reaction surface is shown to be the controlling step in copper and antimony reduction, and an equation correlating mass transfer coefficients has been determined. A kinetic equation, which interprets the influence of stirring speed and solution composition on cobalt cementation, has also been proposed.

  19. Cobalt Ions Improve the Strength of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; St. Clair, A. K.

    1986-01-01

    Technique developed for improving mechanical strength of epoxy resins by adding cobalt ions in form of tris(acetylacetonato)cobalt (III) complex. Solid cast disks prepared from cobalt ion-containing epoxy resins tested for flexural strength and stiffness. Incorporation of cobalt ions into epoxies increased flexural strength of resins by 10 to 95 percent. Suitable resins for this technique include any liquid or solid TGMDA resins. Improved epoxy formulation proves useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft.

  20. Compact magnetooptical isolator with cobalt ferrite on silicon photonic circuits

    NASA Astrophysics Data System (ADS)

    Yanaga, Megumi; Shoji, Yuya; Takamura, Yota; Nakagawa, Shigeki; Mizumoto, Tetsuya

    2015-08-01

    In the telecom wavelength range, the magnetooptical effect of cobalt ferrites is approximately 10 times larger than that of conventional magnetooptical materials such as yttrium iron garnets. In this study, we focus on an application of cobalt ferrite to a magnetooptical isolator that is to be miniaturized and made suitable for integration. First, we prepare polycrystalline cobalt ferrite films deposited on a silicon substrate using a MgO buffer layer. Next, we fabricate a waveguide optical isolator of silicon waveguides by the partial deposition of the cobalt ferrite films. An optical isolation ratio of 5.5 dB is demonstrated.

  1. Solvent extraction of cobalt from laterite-ammoniacal leach liquors

    SciTech Connect

    Nilsen, D.N.; Siemens, R.E.; Rhoads, S.C.

    1980-01-01

    The Bureau of Mines is developing a method to recover Ni, Co, and Cu from laterites containing less than 1.2% Ni and 0.25% Co. The method consists of the following basic unit operations: (1) reduction roasting, (2) leaching, (3) solvent extraction, and (4) electrowinning. The method reflects three Bureau of Mines objectives: (1) recovery of critical minerals that are domestically in short supply from low-grade domestic laterites, (2) lower processing energy requirements, and (3) solution recycling. This report deals with the extraction of cobalt and the preparation of a suitable cobalt electrolyte by solvent extraction from liquor produced by this method. Nickel and copper are coextracted with LIX64N from an ammoniacal ammonium sulfate leach liquor containing about 1.00 g/1 Ni, 0.30 g/1 Co, 0.03 g/1 Cu, and 0.02 g/1 Zn. Cobalt (III) in the nickel-copper barren raffinate is reduced to cobalt (II) with cobalt metal. Reduction of cobalt (III) to cobalt (II) greatly aids subsequent extraction. Commercially available XI-51 extracts about 94% of the cobalt from the treated raffinate in one stage in a laboratory mixer-settler continuous circuit. Ammonia loaded on the solvent is removed in two washing steps. About 94% of the cobalt then is stripped from the XI-51 in one stage with spent cobalt electrolyte containing about 77 g/1 Co and 18 g/1 sulfuric acid (H/sub 2/SO/sub 4/). Electrolytes containing less H/sub 2/SO/sub 4/ also may be used. Preliminary data indicate that coextracted zinc may be removed from pregnant cobalt electrolyte containing 3 g/1 or less H/sub 2/SO/sub 4/ with di-(2 ethylhexyl) phosphoric acid (D2EHPA).

  2. The role of cobalt on the creep of Waspaloy

    NASA Technical Reports Server (NTRS)

    Jarrett, R. N.; Chin, L.; Tien, J. K.

    1984-01-01

    Cobalt was systematically replaced with nickel in Waspaloy (which normally contains 13% Co) to determine the effects of cobalt on the creep behavior of this alloy. Effects of cobalt were found to be minimal on tensile strengths and microstructure. The creep resistance and the stress rupture resistance determined in the range from 704 to 760 C (1300 to 1400 C) were found to decrease as cobalt was removed from the standard alloy at all stresses and temperatures. Roughly a ten-fold drop in rupture life and a corresponding increase in minimum creep rate were found under all test conditions. Both the apparent creep activation energy and the matrix contribution to creep resistance were found to increase with cobalt. These creep effects are attributed to cobalt lowering the stacking fault energy of the alloy matrix. The creep resistance loss due to the removal of cobalt is shown to be restored by slightly increasing the gamma' volume fraction. Results are compared to a previous study on Udimet 700, a higher strength, higher gamma' volume fraction alloy with similar phase chemistry, in which cobalt did not affect creep resistance. An explanation for this difference in behavior based on interparticle spacing and cross-slip is presented.

  3. Microwave Mapping Demonstration Using the Thermochromic Cobalt Chloride Equilibrium

    ERIC Educational Resources Information Center

    Nguyen, Vu D.; Birdwhistell, Kurt R.

    2014-01-01

    An update to the thermochromic cobalt(II) chloride equilibrium demonstration is described. Filter paper that has been saturated with aqueous cobalt(II) chloride is heated for seconds in a microwave oven, producing a color change. The resulting pink and blue map is used to colorfully demonstrate Le Châtelier's principle and to illuminate the…

  4. [The cobalt lung in diamond cutters: a new disease].

    PubMed

    Demedts, M; Gyselen, A

    1989-01-01

    Although for forty years already broncho-pulmonary pathology has been described in workers exposed to hard-metal (i.e. alloys of tungsten carbide and cobalt) and although cobalt is considered the offending agent of this hazard, these abnormalities have almost not been found after exposure to cobalt alone except in animal experiments. Recently we detected clearcut broncho-pulmonary pathology in 48 diamond polishers (i.e. nearly 1% of those exposed) attributable to the ultrafine cobalt dust from the cutting surface of polishing disks, in which it was used as a cementing matrix for microdiamonds without any tungsten carbide. Nineteen of these patients presented with a fibrosing alveolitis documented in 6 by lung biopsy and in 12 by broncho-alveolar lavage, both of which revealed characteristic multinucleated giant cells. Thirteen suffered from asthma of occupational origin, in 9 proven by cobalt-inhalation tests, and in 5 by peak flow measurements at the workplace. Sixteen had mixed bronchial and alveolar pathology or were incompletely documented. A cross-sectional study in about 200 diamond polishers showed a significant correlation between exposure to cobalt and decrease in lung function. The strikingly harmful effects of cobalt can be explained by the chronic exposure to very small particles with markedly increased solubility. The pathogenesis of the broncho-pulmonary pathology may be attributed to the cytotoxic as well as to the sensitising (i.e. allergic and/or idiosyncratic) actions of cobalt. PMID:2561412

  5. Effect of cobalt on Escherichia coli metabolism and metalloporphyrin formation

    PubMed Central

    Majtan, Tomas; Frerman, Frank E.

    2011-01-01

    Toxicity in Escherichia coli resulting from high concentrations of cobalt has been explained by competition of cobalt with iron in various metabolic processes including Fe–S cluster assembly, sulfur assimilation, production of free radicals and reduction of free thiol pool. Here we present another aspect of increased cobalt concentrations in the culture medium resulting in the production of cobalt protoporphyrin IX (CoPPIX), which was incorporated into heme proteins including membrane-bound cytochromes and an expressed human cystathionine beta-synthase (CBS). The presence of CoPPIX in cytochromes inhibited their electron transport capacity and resulted in a substantially decreased respiration. Bacterial cells adapted to the increased cobalt concentration by inducing a modified mixed acid fermentative pathway under aerobiosis. We capitalized on the ability of E. coli to insert cobalt into PPIX to carry out an expression of CoPPIX-substituted heme proteins. The level of CoPPIX-substitution increased with the number of passages of cells in a cobalt-containing medium. This approach is an inexpensive method to prepare cobalt-substituted heme proteins compared to in vitro enzyme reconstitution or in vivo replacement using metalloporphyrin heme analogs and seems to be especially suitable for complex heme proteins with an additional coenzyme, such as human CBS. PMID:21184140

  6. Potential for cobalt recovery from lateritic ores in Europe

    NASA Astrophysics Data System (ADS)

    Herrington, R.

    2012-04-01

    Cobalt is one of the 'critical metals' identified under the EU Raw Materials Initiative. Annually the global mine production of cobalt is around 55,000 tonnes,with Europe's industries consuming around 30% of that figure. Currently Europe produces around 27 tonnes of cobalt from mines in Finland although new capacity is planned. Co-bearing nickel laterite ores being mined in Greece, Macedonia and Kosovo where the cobalt is currently not being recovered (ores have typical analyses of 0.055% Co and >1% Ni,). These ores are currently treated directly in pyrometallurgical plants to recover the contained nickel and this process means there is no separate cobalt product produced. Hydrometallurgical treatment of mineralogically suitable laterite ores can recover the cobalt; for example Cuba recovers 3,500 tonnes of cobalt from its laterite mining operations, which are of a similar scale to the current European operations. Implementation of hydrometallurgical techniques is in its infancy in Europe with one deposit in Turkey planning to use atmospheric heap leaching to recover nickel and copper from oxide-dominated ores. More widespread implementation of these methods to mineralogically suitable ore types could unlock the highly significant undeveloped resources (with metal contents >0.04% Co and >1% Ni), which have been defined throughout the Balkans eastwards into Turkey. At a conservative estimate, this region has the potential to supply up to 30% of the EU cobalt requirements.

  7. Experimental evaluation of cobalt behavior on BWR fuel rod surface

    SciTech Connect

    Karasawa, H.; Asakura, Y.; Sakagami, M.; Uchida, S. )

    1988-06-01

    Cobalt behavior on the boiling water reactor (BWR) fuel rod surface was experimentally evaluated at 285 C and with various pH values. Adsorption of cobalt ions on hematite particles proceeded via the exchange reaction of cobalt ion with the surface hydroxyl of the hematite. The equilibrium constant for the adsorption at 285 C was found to be -- 570 times as large as that at 20 C. The adsorbate formed cobalt ferrite at the rate of 3.4 x 10/sup -2/ g-Co/g-Co adsorbed/h. The dissolution rates of cobalt ferrite and cobalt oxide particles were found to depend on (H/sup -/)/sup 1.1/ and (H/sup -/)/sup 1.2/, respectively, where (H/sup -/) means the H/sup -/ concentration. Cobalt ions were released from these oxides when O/sup 2-/ ions in them combined with two aqueous protons to form water at the oxide-water interface. Cobalt behavior on the fuel rod surface under BWR conditions was discussed using the experimental results.

  8. Comparative toxicity and carcinogenicity of soluble and insoluble cobalt compounds.

    PubMed

    Behl, Mamta; Stout, Matthew D; Herbert, Ronald A; Dill, Jeffrey A; Baker, Gregory L; Hayden, Barry K; Roycroft, Joseph H; Bucher, John R; Hooth, Michelle J

    2015-07-01

    Occupational exposure to cobalt is of widespread concern due to its use in a variety of industrial processes and the occurrence of occupational disease. Due to the lack of toxicity and carcinogenicity data following exposure to cobalt, and questions regarding bioavailability following exposure to different forms of cobalt, the NTP conducted two chronic inhalation exposure studies in rats and mice, one on soluble cobalt sulfate heptahydrate, and a more recent study on insoluble cobalt metal. Herein, we compare and contrast the toxicity profiles following whole-body inhalation exposures to these two forms of cobalt. In general, both forms were genotoxic in the Salmonella T98 strain in the absence of effects on micronuclei. The major sites of toxicity and carcinogenicity in both chronic inhalation studies were the respiratory tract in rats and mice, and the adrenal gland in rats. In addition, there were distinct sites of toxicity and carcinogenicity noted following exposure to cobalt metal. In rats, carcinogenicity was observed in the blood, and pancreas, and toxicity was observed in the testes of rats and mice. Taken together, these findings suggest that both forms of cobalt, soluble and insoluble, appear to be multi-site rodent carcinogens following inhalation exposure. PMID:25896363

  9. Cobalt ferrite nanoparticles under high pressure

    SciTech Connect

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V.; Errandonea, D.

    2015-08-21

    We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20–27 GPa to 7.5–12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B{sub 0} = 204 GPa) is considerably larger than the value previously reported for bulk CoFe{sub 2}O{sub 4} (B{sub 0} = 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B{sub 0} = 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible.

  10. Unconventional magnetisation texture in graphene/cobalt hybrids

    NASA Astrophysics Data System (ADS)

    Vu, A. D.; Coraux, J.; Chen, G.; N’Diaye, A. T.; Schmid, A. K.; Rougemaille, N.

    2016-04-01

    Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism.

  11. Effects of cobalt in lead/acid batteries

    NASA Astrophysics Data System (ADS)

    Bagshaw, N. B.

    The effects of cobalt additions (0.1-1 g/1) to the electrolyte have been studied by anodic corrosion tests on sheets of various alloys, and by continuous charge, cycling and charge retention tests on thick plate automotive-type of batteries. Positive grid corrosion decreases with increase in cobalt concentration but the effect is less marked for alloys with high intrinsic corrosion resistance. Cobalt oxidizes some types of separator even at a relatively low concentration. The top-of-charge voltage is reduced by the presence of cobalt, the effect occurring mainly at the positive plate. Cobalt causes increased open-circuit losses but the effect is fairly small at low concentrations (0.1-0.15 g/1).

  12. Unconventional magnetisation texture in graphene/cobalt hybrids

    PubMed Central

    Vu, A. D.; Coraux, J.; Chen, G.; N’Diaye, A. T.; Schmid, A. K.; Rougemaille, N.

    2016-01-01

    Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism. PMID:27114039

  13. Unconventional magnetisation texture in graphene/cobalt hybrids.

    PubMed

    Vu, A D; Coraux, J; Chen, G; N'Diaye, A T; Schmid, A K; Rougemaille, N

    2016-01-01

    Magnetic domain structure and spin-dependent reflectivity measurements on cobalt thin films intercalated at the graphene/Ir(111) interface are investigated using spin-polarised low-energy electron microscopy. We find that graphene-covered cobalt films have surprising magnetic properties. Vectorial imaging of magnetic domains reveals an unusually gradual thickness-dependent spin reorientation transition, in which magnetisation rotates from out-of-the-film plane to the in-plane direction by less than 10° per cobalt monolayer. During this transition, cobalt films have a meandering spin texture, characterised by a complex, three-dimensional, wavy magnetisation pattern. In addition, spectroscopy measurements suggest that the electronic band structure of the unoccupied states is essentially spin-independent already a few electron-Volts above the vacuum level. These properties strikingly differ from those of pristine cobalt films and could open new prospects in surface magnetism. PMID:27114039

  14. Nitrogen oxides storage catalysts containing cobalt

    DOEpatents

    Lauterbach, Jochen; Snively, Christopher M.; Vijay, Rohit; Hendershot, Reed; Feist, Ben

    2010-10-12

    Nitrogen oxides (NO.sub.x) storage catalysts comprising cobalt and barium with a lean NO.sub.x storage ratio of 1.3 or greater. The NO.sub.x storage catalysts can be used to reduce NO.sub.x emissions from diesel or gas combustion engines by contacting the catalysts with the exhaust gas from the engines. The NO.sub.x storage catalysts can be one of the active components of a catalytic converter, which is used to treat exhaust gas from such engines.

  15. Low-Cobalt Powder-Metallurgy Superalloy

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1986-01-01

    Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

  16. HYDROCARBON FORMATION ON POLYMER-SUPPORTED COBALT

    SciTech Connect

    Benner, Linda S.; Perkins, Patrick; Vollhardt, K.Peter C.

    1980-10-01

    In this report we detail the synthesis catalytic chemistry of polystyrene supported {eta}{sup 5} ~cyclopentadienyl- dicarbonyl cobalt, CpCo(CO){sub 2}. This material is active in the hydrogenation of CO to saturated linear hydrocarbons and appears to retain its "homogeneous", mononuclear character during the course of its catalysis, During ·the course of our work 18% and 20% crosslinked analogs of polystyrene supported CpCo(CO){sub 2} were shown to exhibit limited catalytic activity and no CO activation.

  17. Cold-Sprayed Nanostructured Pure Cobalt Coatings

    NASA Astrophysics Data System (ADS)

    Cavaliere, P.; Perrone, A.; Silvello, A.

    2016-08-01

    Cold-sprayed pure cobalt coatings were deposited on carbon-steel substrate. Submicrometer particles for spraying were produced via cryomilling. Deposits were produced using different processing conditions (gas temperature and pressure, nozzle-to-substrate distance) to evaluate the resulting variations in grain size dimension, microhardness, adhesion strength, and porosity. The coating mechanical properties improved greatly with higher temperature and carrying-gas pressure. The coating microstructure was analyzed as a function of spraying condition by transmission electron microscopy (TEM) observations, revealing many different microstructural features for coatings experiencing low or high strain rates during deposition.

  18. Fischer-Tropsch cobalt catalyst development

    SciTech Connect

    Oukaci, R.; Goodwin, J.G. Jr.; Marcelin, G.; Singleton, A.

    1994-12-31

    Based on the information provided in patents assigned to Gulf, Shell, Exxon, and Statoil, a series of catalysts has been prepared consisting of 12-20 wt% cobalt, a second metal promoter (Ru or Re), and an oxide promoter such as lanthana, zirconia, or alkali oxide, the support being alumina, silica, or titania. All catalysts have been extensively characterized by different methods. The catalysts have been evaluated in terms of their activity, selectivity both in a fixed bed reactor and in a slurry bubble column reactor, and the results correlated with their physico-chemical properties.

  19. Electronic structure of cobalt nanocrystals suspended inliquid

    SciTech Connect

    Liu, Hongjian; Guo, Jinghua; Yin, Yadong; Augustsson, Andreas; Dong, Chungli; Nordgren, Joseph; Chang, Chinglin; Alivisatos, Paul; Thornton, Geoff; Ogletree, D. Frank; Requejo, Felix G.; de Groot, Frank; Salmeron, Miquel

    2007-07-16

    The electronic structure of cobalt nanocrystals suspended in liquid as a function of size has been investigated using in-situ x-ray absorption and emission spectroscopy. A sharp absorption peak associated with the ligand molecules is found that increases in intensity upon reducing the nanocrystal size. X-ray Raman features due to d-d and to charge-transfer excitations of ligand molecules are identified. The study reveals the local symmetry of the surface of {var_epsilon}-Co phase nanocrystals, which originates from a dynamic interaction between Co nanocrystals and surfactant + solvent molecules.

  20. Preparation and characterization of undoped and cobalt doped ZnO for antimicrobial use.

    PubMed

    Stoica, Angelica Oprea; Andronescu, Ecaterina; Ghitulica, Cristina Daniela; Voicu, Georgeta; Grumezescu, Alexandru Mihai; Popa, Marcela; Chifiriuc, Mariana Carmen

    2016-08-30

    The objective of this study was to carry out the synthesis by sol-gel method of undoped and cobalt doped ZnO, with different cobalt concentrations (0.5-5mol%), using as stabilizer monoethanolamine (MEA) in a molar ratio ZnO:MEA=1:2. The dry gel was thermally treated at 500°C/5h, respectively at 1100°C/30min. All the thermal treated samples were of wurtzite type with an hexagonal structure. The doping with Co(2+) induced change of lattice parameters and of crystallite size, proving the successful interleaving of Co(2+) into the ZnO lattice. From the morphological point of view, the thermal treatment at 1100°C/30min led to a higher degree of compactness of the ZnO granules. At 500°C/5h there were formed polyhedral or spherical nanometric particles (25-50nm) which have been agglomerated into aggregates with sizes over 1μm. From the biological point of view, the quantitative analyses of antimicrobial activity have shown that the ZnO doped with cobalt has inhibited the ability of the Bacillus subtilis and Escherichia coli bacterial strains to colonize the inert substrate and therefore, can be used in the design of new antimicrobial strategies. PMID:26394121

  1. Complete cobalt recovery from lithium cobalt oxide in self-driven microbial fuel cell - Microbial electrolysis cell systems

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Yao, Binglin; Wu, Dan; Quan, Xie

    2014-08-01

    Complete cobalt recovery from lithium cobalt oxide requires to firstly leach cobalt from particles LiCoO2 and then recover cobalt from aqueous Co(II). A self-driven microbial fuel cell (MFC)-microbial electrolysis cell (MEC) system can completely carry out these two processes, in which Co(II) is firstly released from particles LiCoO2 on the cathodes of MFCs and then reduced on the cathodes of MECs which are powered by the cobalt leaching MFCs. A cobalt leaching rate of 46 ± 2 mg L-1 h-1 with yield of 1.5 ± 0.1 g Co g-1 COD (MFCs) and a Co(II) reduction rate of 7 ± 0 mg L-1 h-1 with yield of 0.8 ± 0.0 g Co g-1 COD (MECs), as well as a overall system cobalt yield of 0.15 ± 0.01 g Co g-1 Co can be achieved in this self-driven MFC-MEC system. Coulombic efficiencies reach 41 ± 1% (anodic MFCs), 75 ± 0% (anodic MECs), 100 ± 2% (cathodic MFCs), and 29 ± 1% (cathodic MECs) whereas overall system efficiency averages 34 ± 1%. These results provide a new process of linking MFCs to MECs for complete recovery of cobalt and recycle of spent lithium ion batteries with no external energy consumption.

  2. Biosorptive removal of copper and cobalt from aqueous solutions: Shewanella spp. put to the test

    NASA Astrophysics Data System (ADS)

    Mamba, B. B.; Dlamini, N. P.; Mulaba–Bafubiandi, A. F.

    Biosorption of copper and cobalt by Shewanella spp. was investigated in this study. The biosorption capabilities of Shewanella spp. for copper and cobalt were monitored at different ion concentrations (0.002 M, 0.07 M and 0.2 M), biomass dosages (50, 100 and 150 (×10 4 CFU/ml)) and pH (values 2-8) in batch mode. At optimum concentration (0.002 M/3.86 gl -1), biosorbent dosage (150 × 10 4 CFU/ml) and solution pH 6.5, Shewanella spp. recorded maximum copper and cobalt uptakes of 38% and 27%, respectively. The kinetic data obtained at different concentrations suggested that the biosorption rate was fast and in most cases the biosorption took place within 8 h followed by a slow attainment of equilibrium and the Langmuir sorption model fitted the data well with very high correlation efficiencies (>0.95). The results obtained in this study suggest that biosorbents, with further research, can in future be viewed as suitable sorbents in the recovery of precious metals such as copper after being discharged as effluent or as a result of mineral processing. In managing water resources, it is important that metallic species such as copper and cobalt be removed from water or reduced to acceptable levels since these metal species may cause ill-health effects to humans and livestock if the required concentration levels are exceeded. The required levels should fall within with World Health Organization (WHO) water quality guidelines and the water quality standards for various purposes (e.g. agriculture, drinking, domestic, water-reuse) as prescribed by individual countries.

  3. Azido- and chlorido-cobalt complex as carrier-prototypes for antitumoral prodrugs.

    PubMed

    Pires, Bianca M; Giacomin, Letícia C; Castro, Frederico A V; Cavalcanti, Amanda dos S; Pereira, Marcos D; Bortoluzzi, Adailton J; Faria, Roberto B; Scarpellini, Marciela

    2016-04-01

    Cobalt(III) complexes are well-suited systems for cytotoxic drug release under hypoxic conditions. Here, we investigate the effect of cytotoxic azide release by cobalt-containing carrier-prototypes for antitumoral prodrugs. In addition, we study the species formed after reduction of Co(3+) → Co(2+) in the proposed models for these prodrugs. Three new complexes, [Co(III)(L)(N3)2]BF4(1), [{Co(II)(L)(N3)}2](ClO4)2(2), and [Co(II)(L)Cl]PF6(3), L=[(bis(1-methylimidazol-2-yl)methyl)(2-(pyridyl-2-yl)ethyl)amine], were synthesized and studied by several spectroscopic, spectrometric, electrochemical, and crystallographic methods. Reactivity and spectroscopic data reveal that complex 1 is able to release N3(-) either after reduction with ascorbic acid, or by ambient light irradiation, in aqueous phosphate buffer (pH6.2, 7.0 and 7.4) and acetonitrile solutions. The antitumoral activities of compounds 1-3 were tested in normoxia on MCF-7 (human breast adenocarcinoma), PC-3 (human prostate) and A-549 (human lung adenocarcinoma epithelial) cell lines, after 24h of exposure. Either complexes or NaN3 presented IC50 values higher than 200 μM, showing lower cytotoxicity than the clinical standard antitumoral complex cisplatin, under the same conditions. Complexes 1-3 were also evaluated in hypoxia on A-549 and results indicate high IC50 data (>200 μM) after 24h of exposure. However, an increase of cancer cell susceptibility to 1 and 2 was observed at 300 μM. Regarding complex 3, no cytotoxic activity was observed in the same conditions. The data presented here indicate that the tridentate ligand L is able to stabilize both oxidation states of cobalt (+3 and +2). In addition, the cobalt(III) complex generates the low cytotoxic cobalt(II) species after reduction, which supports their use as as carrier prototypes for antitumoral prodrugs. PMID:26881993

  4. Preparation and characterization of electrodeposited cobalt nanowires

    SciTech Connect

    Irshad, M. I. Mohamed, N. M.; Ahmad, F. Abdullah, M. Z.

    2014-10-24

    Electrochemical deposition technique has been used to deposit cobalt nanowires into the nano sized channels of Anodized Aluminium Oxide (AAO) templates. CoCl{sub 2}Ðœ‡6H2O salt solution was used, which was buffered with H{sub 3}BO{sub 3} and acidified by dilute H{sub 2}SO{sub 4} to increase the plating life and control pH of the solution. Thin film of copper around 150 nm thick on one side of AAO template coated by e-beam evaporation system served as cathode to create electrical contact. FESEM analysis shows that the as-deposited nanowires are highly aligned, parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. The TEM results show that electrodeposited cobalt nanowires are crystalline in nature. The Hysteresis loop shows the magnetization properties for in and out of plane configuration. The in plane saturation magnetization (Ms) is lower than out of plane configuration because of the easy axis of magnetization is perpendicular to nanowire axis. These magnetic nanowires could be utilized for applications such as spintronic devices, high density magnetic storage, and magnetic sensor applications.

  5. Cobalt distribution during copper matte smelting

    NASA Astrophysics Data System (ADS)

    Kho, T. S.; Swinbourne, D. R.; Lehner, T.

    2006-04-01

    Many smelter operators subscribe to the “precautionary principle” and wish to understand the behavior of the metals and impurities during smelting, especially how they distribute between product and waste phases and whether these phases lead to environmental, health, or safety issues. In copper smelting, copper and other elements are partitioned between copper matte, iron silicate slag, and possibly the waste gas. Many copper concentrates contain small amounts of cobalt, a metal of considerable value but also of some environmental interest. In this work, the matte/slag distribution ratio (weight percent) of cobalt between copper matte (55 wt pct) and iron silicate slag was thermodynamically modeled and predicted to be approximately 5. Experiments were performed using synthetic matte and slag at 1250 °C under a low oxygen partial pressure and the distribution ratio was found to be 4.3, while between industrial matte and slag, the ratio was found to be 1.8. Both values are acceptably close to each other and to the predicted value, given the errors inherent in such measurements. The implications of these results for increasingly sustainable copper production are discussed.

  6. Cataractogenesis after Cobalt-60 eye plaque radiotherapy

    SciTech Connect

    Kleineidam, M.; Augsburger, J.J. ); Hernandez, C.; Glennon, P.; Brady, L.W. )

    1993-07-15

    This study was designed to estimate the actuarial incidence of typical postirradiation cataracts and to identify prognostic factors related to their development in melanoma-containing eyes treated by Cobalt-60 plaque radiotherapy. A special interest was the impact of calculated radiation dose and dose-rate to the lens. The authors evaluated the actuarial occurrence of post-irradiation cataract in 365 patients with primary posterior uveal melanoma treated by Cobalt-60 plaque radiotherapy between 1976 and 1986. Only 22% (S.E. = 4.6%) of the patients who received a total dose of 6 to 20 Gy at the center of the lens developed a visually significant cataract attributable to the radiation within 5 years after treatment. Using multivariate Cox proportional hazards modeling, the authors identified thickness of the tumor, location of the tumor's anterior margin relative to the equatorward and the ora serrata, and diameter of the eye plaque used as the best combination of covariables for predicting length of time until development of cataract. Surprisingly, the dose of radiation delivered to the lens, which was strongly correlated to all of these covariables, was not a significant predictive factor in multivariate analysis. The results suggest that success of efforts to decrease the occurrence rate of post-irradiation cataracts by better treatment planning might be limited in patients with posterior uveal melanoma. 21 refs., 2 figs., 5 tabs.

  7. Mechanical properties of iron-cobalt alloys for power applications

    SciTech Connect

    Fingers, R.T.; Coate, J.E.; Dowling, N.E.

    1997-12-31

    The United States Air Force is in the process of developing magnetic bearings as well as an aircraft Integrated Power Unit and an Internal Starter/Generator for main propulsion engines. These developments are the driving force for the new emphasis on high temperature, high strength magnetic materials for power applications. Analytical work, utilizing elasticity theory, in conjunction with design requirements, indicates a need for magnetic materials to have strengths in excess of 80 ksi up to about 1000 F. Two specific iron-cobalt alloys have been tested as part of a magnetic materials characterization program at Wright Laboratory. The first material is Hiperco{reg_sign} Alloy 50HS from Carpenter Technology Corporation and the second is HS50 from Carpenter Technology Corporation and the second is HS50 from Telcon Limited. Specimens of each alloy have been heat treated by various recipes ranging in temperature from 1300 F to 1350 F and times of one and two hours. Tensile testing was performed in accordance with ASTM Standard E-8 for the room temperature tests and ASTM Standard E-21 for the elevated temperature tests. The tests were performed at room temperature and at 900 F. Stress versus strain behavior was measured and analyzed. The curves clearly indicate: a yield point, a heterogeneous deformation described as Lueders elongation and most often a section of homogeneous deformation that concluded with necking and fracture. Limited creep testing was also conducted in accordance with ASTM Standard E-139 and time to one percent, two percent, and failure was measured and the behavior is discussed. The effect of composition and heat treatment of these two soft magnetic materials on mechanical behavior and the impact on potential aircraft power applications is discussed.

  8. Enhancing electrochemical properties of silicon-graphite anodes by the introduction of cobalt for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Liang, Yunhui; Zhou, Qian; Peng, Yi; Yang, Huabin

    2015-09-01

    A Si-Co-C composite material has been prepared by a simple high energy mechanical milling process (HEMM). The crystal structures and morphologies of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), indicating that silicon and cobalt elements uniformly distribute in graphite sheets. Electrochemical tests show that the initial discharge and charge capacities of the Si20Co10C70 composite are 1283.3 mAh g-1 and 1068.8 mAh g-1, respectively, with an initial coulombic efficiency of 83.3%. It maintains a reversible capacity of 620 mAh g-1 after 25 cycles and remains stable above 610 mAh g-1 after 50 cycles. The results of cyclic voltammetry (CV) prove that cobalt acts as an inactive matrix, and the result of electrochemical impedance spectroscopy (EIS) reveals that the polarization resistance (Rp) decreases after the Co addition. It is believed that uniform dispersed cobalt nanoparticles relieve the destruction of the graphite. Furthermore, the existence of carbon and cobalt not only restrains the agglomeration of Si particles, but also suppresses the volume expansion of Si. This extraordinary microstructure is believed to be responsible for the excellent electrochemical performance.

  9. High doses of cobalt induce optic and auditory neuropathy.

    PubMed

    Apostoli, Pietro; Catalani, Simona; Zaghini, Anna; Mariotti, Andrea; Poliani, Pietro Luigi; Vielmi, Valentina; Semeraro, Francesco; Duse, Sarah; Porzionato, Andrea; Macchi, Veronica; Padovani, Alessandro; Rizzetti, Maria Cristina; De Caro, Raffaele

    2013-09-01

    The adverse biological effects of continuous exposure to cobalt and chromium have been well defined. In the past, this toxicity was largely an industrial issue concerning workers exposed in occupational setting. Nevertheless, recent reports have described a specific toxicity mediated by the high levels of cobalt and chromium released by metallic prostheses, particularly in patients who had received hip implants. Clinical symptoms, including blindness, deafness and peripheral neuropathy, suggest a specific neurotropism. However, little is known about the neuropathological basis of this process, and experimental evidence is still lacking. We have investigated this issue in an experimental setting using New Zealand White rabbits treated with repeated intravenous injections of cobalt and chromium, alone or in combination. No evident clinical or pathological alterations were associated after chromium administration alone, despite its high levels in blood and tissue while cobalt-chromium and cobalt-treated rabbits showed clinical signs indicative of auditory and optic system toxicity. On histopathological examination, the animals showed severe retinal and cochlear ganglion cell depletion along with optic nerve damage and loss of sensory cochlear hair cells. Interestingly, the severity of the alterations was related to dosages and time of exposure. These data confirmed our previous observation of severe auditory and optic nerve toxicity in patients exposed to an abnormal release of cobalt and chromium from damaged hip prostheses. Moreover, we have identified the major element mediating neurotoxicity to be cobalt, although the molecular mechanisms mediating this toxicity still have to be defined. PMID:23069009

  10. Polyvinyl alcohol functionalized cobalt ferrite nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Salunkhe, A. B.; Khot, V. M.; Thorat, N. D.; Phadatare, M. R.; Sathish, C. I.; Dhawale, D. S.; Pawar, S. H.

    2013-01-01

    In the present work, cobalt ferrite nanoparticles (CoFe2O4 NPs) have been synthesized by combustion method. The surface of the CoFe2O4 NPs was modified with biocompatible polyvinyl alcohol (PVA). To investigate effect and nature of coating on the surface of CoFe2O4 NPs, the NPs were characterized X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The transmission electron microscopy (TEM) and dynamic light scattering (DLS) results demonstrate the monodispersed characteristics of CoFe2O4 NPs after surface modification with PVA. The decrease in contact angle from 162° to 50° with PVA coating on NPs indicates the transition from hydrophobic nature to hydrophilic. The Magnetic properties measurement system (MPMS) results show that the NPs have ferromagnetic behavior with high magnetization of 75.04 and 71.02 emu/g of uncoated and coated CoFe2O4 NPs respectively. These PVA coated NPs exhibit less toxicity over uncoated CoFe2O4 NPs up to 1.8 mg mL-1 when tested with mouse fibroblast L929 cell line.

  11. Recovery of copper and cobalt from ancient slag.

    PubMed

    Bulut, Gülay

    2006-04-01

    About 2.5 million tonnes of copper smelter slag are available in Küre, northern part of Turkey. This slag contains large amounts of metallic values such as copper and cobalt. A representative slag sample containing 0.98% Cu, 0.49% Co and 51.47% Fe was used in the experimental studies. Two different methods, direct acid leaching and acid baking followed by hot water leaching were used for recovering Cu and Co from the slag. The effects of leaching time, temperature and acid concentration on Cu- and Co-dissolving efficiencies were investigated in the direct acid leaching tests. The optimum leaching conditions were found to be a leaching time of 2 h, acid concentration of 120 g L(-1), and temperature of 60 degrees C. Under these conditions, 78% Cu and 90% Co were extracted. In the acid baking + hot water leaching tests, 74% Co was dissolved after 1 h of roasting at 200 degrees C using a 3:1 acid:slag ratio, whereas the Cu-dissolving efficiency was 79% and the total slag weight loss was approximately 50%. PMID:16634226

  12. Reoxidation and deactivation of supported cobalt Fischer-Tropsch catalysts

    SciTech Connect

    Schanke, D.; Hilmen, A.M.; Bergene, E.

    1995-12-01

    The Fischer-Tropsch synthesis is an attractive possibility for conversion of natural gas into high quality liquid fuels. Due to its low water-gas shift activity, good activity/selectivity properties and relatively low price, cobalt is the choice of catalytic metal for natural gas conversion via Fischer-Tropsch synthesis. In the cobalt-catalyzed Fischer-Tropsch reaction, oxygen is mainly rejected as water. In this paper we describe the influence of water on supported cobalt catalysts. The deactivation of supported Co catalysts was studied in a fixed-bed reactor using synthesis gas feeds containing varying concentrations of water vapour.

  13. Magnetoelastic coupling in epitaxial cobalt ferrite/barium titanate heterostructures

    NASA Astrophysics Data System (ADS)

    Gräfe, Joachim; Welke, Martin; Bern, Francis; Ziese, Michael; Denecke, Reinhard

    2013-08-01

    Ultra-thin cobalt ferrite films have been synthesised on ferroelectric barium titanate crystals. The cobalt ferrite films exhibit a magnetic response to strain induced by structural changes in the barium titanate substrate, suggesting a pathway to multiferroic coupling. These structural changes are achieved by heating through the phase transition temperatures of barium titanate. In addition the ferromagnetic signal of the substrate itself is taken into account, addressing the influence of impurities or defects in the substrate. The cobalt ferrite/barium titanate heterostructure is a suitable oxidic platform for future magnetoelectric applications with an established ferroelectric substrate and widely tuneable magnetic properties by changing the transition metal in the ferrite film.

  14. Oxygen Evolution Electrocatalysis on Cobalt Oxide surfaces

    NASA Astrophysics Data System (ADS)

    Bajdich, Michal; Norskov, Jens K.; García-Mota, Monica; Bell, Alexis T.

    2012-02-01

    The oxidation of water for hydrogen production using sunlight is of high importance to photo-fuel cell research. The electrochemical approach via heterogeneous catalysis to water splitting is a very promising route. The key challenge of this method lies in reduction of the loses, i.e., over-potential, for the oxygen evolution reaction (OER) on the anode. In this work, we investigate the dependence of theoretical over-potential of OER on type of anode by applying standard density functional theory (DFT). We attempt to explain recent experimental observation of enhanced activity on gold supported Cobalt Oxide surfaces [1]. We explore variety of possible CoO structures and associated surfaces which could emerge under operating conditions of catalyst. Finally, we also explore the influence of environment and admixtures of CoO with other elements. [4pt] [1] B.S. Yeo, A.T. Bell, AT, J. Am. Chem. Soc., 133, 5587-5593 (2011).

  15. Aqua-bromidobis(dimethyl-glyoximato)cobalt(III).

    PubMed

    Meera, Parthasarathy; Amutha Selvi, Madhavan; Jothi, Pachaimuthu; Dayalan, Arunachalam

    2011-04-01

    In the title complex, [CoBr(C(4)H(7)N(2)O(2))(2)(H(2)O)], a crystallo-graphic mirror plane bis-ects the mol-ecule, perpendicular to the glyoximate ligands. The geometry around the cobalt(III) atom is approximately octa-hedral with the four glyoximate N atoms forming the square base. A bromide ion and the O atom of a water mol-ecule occupy the remaining coordination sites. The N-Co-N bite angles are 82.18 (4) and 80.03 (16)°. The glyoximate moieties form strong intra-molecular O-H⋯O hydrogen bonds. The coordinated water mol-ecule forms an inter-molecular O-H⋯O hydrogen bond with a glyoximate O atom, thereby generating supra-molecular chains parallel to [010]. PMID:21753964

  16. Role of Surface Cobalt Silicate in Single-Walled Carbon Nanotube Synthesis from Silica-Supported Cobalt Catalysts

    SciTech Connect

    Li, N.; Wang, X; Derrouiche, S; Haller, G; Pfefferle, L

    2010-01-01

    A silica-supported cobalt catalyst has been developed via incipient wetness impregnation for high-yield synthesis of single-walled carbon nanotubes (SWNTs). Co/SiO{sub 2}-impregnated catalysts have not been observed to be efficient for SWNT synthesis. Using an appropriately chosen precursor, we show that effective catalysts can be obtained for SWNT synthesis with yields up to 75 wt %. Detailed characterization indicates that the active sites for SWNT synthesis are small cobalt particles resulting from the reduction of a highly dispersed surface cobalt silicate species. The SWNTs produced by this catalyst are of high quality and easy to purify, and the process is simple and scalable.

  17. Reaction of cobalt in SO2 atmospheric at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Worrell, W. L.

    1983-01-01

    The reaction rate of cobalt in SO2 argon environments was measured at 650 C, 700 C, 750 C and 800 C. Product scales consist primarily of an interconnected sulfide phase in an oxide matrix. At 700 C to 800 C a thin sulfide layer adjacent to the metal is also observed. At all temperatures, the rapid diffusion of cobalt outward through the interconnected sulfide appears to be important. At 650 C, the reaction rate slows dramatically after five minutes due to a change in the distribution of these sulfides. At 700 C and 750 C the reaction is primarily diffusion controlled values of diffusivity of cobalt (CoS) calculated from this work show favorable agreement with values of diffusivity of cobalt (CoS) calculated from previous sulfidation work. At 800 C, a surface step becomes rate limiting.

  18. The Study of a Cobalt Complex--A Laboratory Project.

    ERIC Educational Resources Information Center

    Loehlin, James H.; And Others

    1982-01-01

    Describes an 8-week project involving the synthesis of cobalt compounds. Once synthesized, compounds are qualitatively and quantitatively analyzed. Background information, laboratory procedures, and results/discussion are provided for three project experiments. (Author/JN)

  19. Cobalt Oxide Hollow Nanoparticles Derived by Bio-Templating

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Choi, Sang H.; Lillehei, Peter T.; Chu, Sang-Hyon; King, Glen C.; Watt, Gerald D.

    2005-01-01

    We present here the first fabrication of hollow cobalt oxide nanoparticles produced by a protein-regulated site-specific reconstitution process in aqueous solution and describe the metal growth mechanism in the ferritin interior.

  20. Determination of traces of cobalt in soils: A field method

    USGS Publications Warehouse

    Almond, H.

    1953-01-01

    The growing use of geochemical prospecting methods in the search for ore deposits has led to the development of a field method for the determination of cobalt in soils. The determination is based on the fact that cobalt reacts with 2-nitroso-1-naphthol to yield a pink compound that is soluble in carbon tetrachloride. The carbon tetrachloride extract is shaken with dilute cyanide to complex interfering elements and to remove excess reagent. The cobalt content is estimated by comparing the pink color in the carbon tetrachloride with a standard series prepared from standard solutions. The cobalt 2-nitroso-1-naphtholate system in carbon tetrachloride follows Beer's law. As little as 1 p.p.m. can be determined in a 0.1-gram sample. The method is simple and fast and requires only simple equipment. More than 40 samples can be analyzed per man-day with an accuracy within 30% or better.

  1. Recovery of Silver and Cobalt from Laboratory Wastes.

    ERIC Educational Resources Information Center

    Foust, Donald F.

    1984-01-01

    Procedures for recovering silver and cobalt from laboratory wastes (including those resulting from student experiments) are presented. The procedures are generally applicable since only common, inexpensive laboratory reagents are needed. (JN)

  2. Studies of the Codeposition of Cobalt Hydroxide and Nickel Hydroxide

    NASA Technical Reports Server (NTRS)

    Ho, C. H.; Murthy, M.; VanZee, J. W.

    1997-01-01

    Topics considered include: chemistry, experimental measurements, planar film model development, impregnation model development, results and conclusion. Also included: effect of cobalt concentration on deposition/loading; effect of current density on loading distribution.

  3. Reaction of cobalt in SO2 atmospheres at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Worrell, W. L.

    1984-01-01

    The reaction rate of cobalt in SO2 argon environments was measured at 650 C, 700 C, 750 C and 800 C. Product scales consist primarily of an interconnected sulfide phase in an oxide matrix. At 700 C to 800 C, a thin sulfide layer adjacent to the metal is also observed. At all temperatures, the rapid diffusion of cobalt outward through the interconnected sulfide appears to be important. At 650 C, the reaction rate slows dramatically after five minutes due to a change in the distribution of these sulfides. At 700 C and 750 C, the reaction is primarily diffusion controlled; values of diffusivity of cobalt (CoS) calculated from this work show favorable agreement with values of diffusivity of cobalt (CoS) calculated from previous sulfidation work. At 800 C, a surface step becomes rate limiting. Previously announced in STAR as N83-35104

  4. Battery related cobalt and REE flows in WEEE treatment.

    PubMed

    Sommer, P; Rotter, V S; Ueberschaar, M

    2015-11-01

    In batteries associated with waste electrical and electronic equipment (WEEE), battery systems can be found with a higher content of valuable and critical raw materials like cobalt and rare earth elements (REE) relative to the general mix of portable batteries. Based on a material flow model, this study estimates the flows of REE and cobalt associated to WEEE and the fate of these metals in the end-of-life systems. In 2011, approximately 40 Mg REE and 325 Mg cobalt were disposed of with WEEE-batteries. The end-of-life recycling rate for cobalt was 14%, for REE 0%. The volume of waste batteries can be expected to grow, but variation in the battery composition makes it difficult to forecast the future secondary raw material potential. Nevertheless, product specific treatment strategies ought to be implemented throughout the stages of the value chain. PMID:26054962

  5. Size-dependent dissociation of carbon monoxide on cobalt nanoparticles.

    PubMed

    Tuxen, Anders; Carenco, Sophie; Chintapalli, Mahati; Chuang, Cheng-Hao; Escudero, Carlos; Pach, Elzbieta; Jiang, Peng; Borondics, Ferenc; Beberwyck, Brandon; Alivisatos, A Paul; Thornton, Geoff; Pong, Way-Faung; Guo, Jinghua; Perez, Ruben; Besenbacher, Flemming; Salmeron, Miquel

    2013-02-13

    In situ soft X-ray absorption spectroscopy (XAS) was employed to study the adsorption and dissociation of carbon monoxide molecules on cobalt nanoparticles with sizes ranging from 4 to 15 nm. The majority of CO molecules adsorb molecularly on the surface of the nanoparticles, but some undergo dissociative adsorption, leading to oxide species on the surface of the nanoparticles. We found that the tendency of CO to undergo dissociation depends critically on the size of the Co nanoparticles. Indeed, CO molecules dissociate much more efficiently on the larger nanoparticles (15 nm) than on the smaller particles (4 nm). We further observed a strong increase in the dissociation rate of adsorbed CO upon exposure to hydrogen, clearly demonstrating that the CO dissociation on cobalt nanoparticles is assisted by hydrogen. Our results suggest that the ability of cobalt nanoparticles to dissociate hydrogen is the main parameter determining the reactivity of cobalt nanoparticles in Fischer-Tropsch synthesis. PMID:23339635

  6. Formation of cobalt silicide by ion beam mixing

    NASA Astrophysics Data System (ADS)

    Min, Ye; Burte, Edmund P.; Ryssel, Heiner

    1991-07-01

    The formation of cobalt silicides by arsenic ion implantation through a cobalt film which causes a mixing of the metal with the silicon substrate was investigated. Furthermore, cobalt suicides were formed by rapid thermal annealing (RTA). Sheet resistance and silicide phases of implanted Co/Si samples depend on the As dose. Ion beam mixing at doses higher than 5 × 10 15 cm -2 and RTA at temperatures T ⩾ 900° C result in almost equal values of Rs. RBS and XRD spectra of these samples illustrate the formation of a homogeneous CoSi 2 layer. Significant lateral growth of cobalt silicide beyond the edge of patterned SiO 2 was observed in samples which were only subjected to an RTA process ( T ⩾ 900 ° C), while this lateral suicide growth could be reduced efficiently by As implantation prior to RTA.

  7. Use of phosphate for separation of cobalt from iron

    USGS Publications Warehouse

    North, V.; Wells, R.C.

    1942-01-01

    The well-known tendency of cobalt to be retained by the iron-alumina precipitate produced by ammonia has generally been ascribed to a specific adsorption by the large surface of this gelatinous precipitate. Whatever its cause, it can be overcome by precipitating the iron as phosphate at a pH of 3.5. The precipitate is easily filterable and practically all the cobalt passes into the filtrate.

  8. Annealing effects on microstrain of cobalt oxide nanoparticles

    SciTech Connect

    Deotale, Anjali Jain Nandedkar, R. V.; Sinha, A. K.; Singh, M. N.; Upadhyay, Anuj

    2014-04-24

    Cobalt oxide nanoparticles in different phases have been synthesized using ash supported method. The effect of isochronal annealing on micro-strain of cobalt oxide nanoparticles has been studied. The lattice strain contribution to the x-ray diffraction line broadening in the nanoparticles was analyzed using Williamson Hall (W-H) plot. It is observed that micro-strain was released at higher annealing temperature.

  9. Synthesis and structural characterization of polyaniline/cobalt chloride composites

    NASA Astrophysics Data System (ADS)

    Asha, Goyal, Sneh Lata; Kishore, Nawal

    2016-05-01

    Polyaniline (PANI) and PANI /cobalt chloride composites were synthesized by in situ chemical oxidative polymerization of aniline with CoCl2.6H2O using ammonium peroxidisulphate as an oxidant. These composites were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The XRD study reveals that both PANI and composites are amorphous. The XRD and SEM results confirm the presence of cobalt chloride in the composites.

  10. Electro-oxidation of ascorbic acid by cobalt core-shell nanoparticles on a H-terminated Si(100) and by nanostructured cobalt-coated Si nanowire electrodes.

    PubMed

    Zhao, Liyan; Liao, Kristine; Pynenburg, Mark; Wong, Louis; Heinig, Nina; Thomas, Joseph P; Leung, K T

    2013-04-10

    Determination of the concentration of ascorbic acid in a solution has attracted intense recent interest. Here we demonstrate the feasibility of electro-oxidation of ascorbic acid on spherical cobalt core-shell nanoparticles (10-50 nm dia.) prepared by electrochemical deposition on a H-terminated Si(100) substrate. Depth-profiling X-ray photoelectron spectroscopy reveals that these nanoparticles consist of a metallic cobalt core covered by a Co(OH)2 shell without any evidence of CoOx. Glancing-incidence X-ray diffraction studies further show that the metallic Co core consists of a mixture of hexagonal close packed and face centered cubic structures, the relative composition of which can be easily controlled by the deposition potential. We further demonstrate that when these Co nanoparticles are deposited on a high-surface-area electrode as provided by a Si nanowire template, the resulting nanostructured Co-coated Si nanowire electrode offers a promising high-performance sensor platform for ascorbic acid detection. PMID:23488767

  11. Ion-beam mixed ultra-thin cobalt suicide (CoSi2) films by cobalt sputtering and rapid thermal annealing

    NASA Astrophysics Data System (ADS)

    Kal, S.; Kasko, I.; Ryssel, H.

    1995-10-01

    The influence of ion-beam mixing on ultra-thin cobalt silicide (CoSi2) formation was investigated by characterizing the ion-beam mixed and unmixed CoSi2 films. A Ge+ ion-implantation through the Co film prior to silicidation causes an interface mixing of the cobalt film with the silicon substrate and results in improved silicide-to-silicon interface roughness. Rapid thermal annealing was used to form Ge+ ion mixed and unmixed thin CoSi2 layer from 10 nm sputter deposited Co film. The silicide films were characterized by secondary neutral mass spectroscopy, x-ray diffraction, tunneling electron microscopy (TEM), Rutherford backscattering, and sheet resistance measurements. The experi-mental results indicate that the final rapid thermal annealing temperature should not exceed 800°C for thin (<50 nm) CoSi2 preparation. A comparison of the plan-view and cross-section TEM micrographs of the ion-beam mixed and unmixed CoSi2 films reveals that Ge+ ion mixing (45 keV, 1 × 1015 cm-2) produces homogeneous silicide with smooth silicide-to-silicon interface.

  12. Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

    DOEpatents

    Zelenay, Piotr; Wu, Gang

    2014-04-29

    A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

  13. Effects of cobalt in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Tien, J. K.; Jarrett, R. N.

    1983-01-01

    The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys.

  14. Pulsed Laser Synthesized Magnetic Cobalt Oxide Nanoparticles for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Bhatta, Hari; Gupta, Ram; Ghosh, Kartik; Kahol, Pawan; Delong, Robert; Wanekawa, Adam

    2011-03-01

    Nanomaterials research has become a major attraction in the field of advanced materials research in the area of Physics, Chemistry, and Materials Science. Biocompatible and chemically stable magnetic metal oxide nanoparticles have biomedical applications that includes drug delivery, cell and DNA separation, gene cloning, magnetic resonance imaging (MRI). This research is aimed at the fabrication of magnetic cobalt oxide nanoparticles using a safe, cost effective, and easy to handle technique that is capable of producing nanoparticles free of any contamination. Cobalt oxide nanoparticles have been synthesized at room temperature using cobalt foil by pulsed laser ablation technique. These cobalt oxide nanoparticles were characterized using UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and dynamic laser light scattering (DLLS). The magnetic cobalt oxides nanoparticles were stabilized in glucose solutions of various concentrations in deionized water. The presence of UV-Vis absorption peak at 270 nm validates the nature of cobalt oxide nanoparticles. The DLLS size distributions of nanoparticles are in the range of 110 to 300 nm, which further confirms the presence nanoparticles. This work is partially supported by National Science Foundation (DMR- 0907037).

  15. Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst

    PubMed Central

    Kim, Hyunah; Park, Jimin; Park, Inchul; Jin, Kyoungsuk; Jerng, Sung Eun; Kim, Sun Hee; Nam, Ki Tae; Kang, Kisuk

    2015-01-01

    The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt- and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (∼0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry. PMID:26365091

  16. Reoxidation and deactivation of supported cobalt Fischer-Tropsch catalysts

    SciTech Connect

    Schanke, D.; Bergene, E.; Adnanes, E.

    1995-12-31

    As a result of the highly exothermic nature of the Fischer-Tropsch reaction, heat transfer considerations limit the maximum conversion per pass in fixed-bed processes, whereas slurry reactors can operate at higher conversions. During Fischer-Tropsch synthesis on cobalt catalysts, high conversions will generate high partial pressures of water at the reactor exit, due to the low water gas shift activity of cobalt. In addition, the extensive back-mixing in slurry reactors will give a relatively uniform concentration profile in the reactor, characterized by a high concentration of water and low reactant concentrations. From the commercial iron-catalyzed Fischer-Tropsch synthesis in fixed-bed (Arge) reactors it is known that the catalyst deactivates by oxidation of iron by CO{sub 2} and H{sub 2}O near the exit of the reactor. Although bulk oxidation of cobalt during Fischer-Tropsch synthesis is not thermodynamically favored, it was early speculated that surface oxidation of cobalt could occur during Fischer-Tropsch synthesis. The purpose of the present work is to describe the influence of water on the deactivation behavior of Al{sub 2}O{sub 3} supported cobalt catalysts. The possibility of cobalt oxidation during Fischer-Tropsch synthesis was investigated by model studies.

  17. Cobalt mineral exploration and supply from 1995 through 2013

    USGS Publications Warehouse

    Wilburn, David R.

    2011-01-01

    The global mining industry has invested a large amount of capital in mineral exploration and development over the past 15 years in an effort to ensure that sufficient resources are available to meet future increases in demand for minerals. Exploration data have been used to identify specific sites where this investment has led to a significant contribution in global mineral supply of cobalt or where a significant increase in cobalt production capacity is anticipated in the next 5 years. This report provides an overview of the cobalt industry, factors affecting mineral supply, and circumstances surrounding the development, or lack thereof, of key mineral properties with the potential to affect mineral supply. Of the 48 sites with an effective production capacity of at least 1,000 metric tons per year of cobalt considered for this study, 3 producing sites underwent significant expansion during the study period, 10 exploration sites commenced production from 1995 through 2008, and 16 sites were expected to begin production by 2013 if planned development schedules are met. Cobalt supply is influenced by economic, environmental, political, and technological factors affecting exploration for and production of copper, nickel, and other metals as well as factors affecting the cobalt industry. Cobalt-rich nickel laterite deposits were discovered and developed in Australia and the South Pacific and improvements in laterite processing technology took place during the 1990s and early in the first decade of the 21st century when mining of copper-cobalt deposits in Congo (Kinshasa) was restricted because of regional conflict and lack of investment in that country's mining sector. There was also increased exploration for and greater importance placed on cobalt as a byproduct of nickel mining in Australia and Canada. The emergence of China as a major refined cobalt producer and consumer since 2007 has changed the pattern of demand for cobalt, particularly from Africa and

  18. Cobalt(I) Olefin Complexes: Precursors for Metal-Organic Chemical Vapor Deposition of High Purity Cobalt Metal Thin Films.

    PubMed

    Hamilton, Jeff A; Pugh, Thomas; Johnson, Andrew L; Kingsley, Andrew J; Richards, Stephen P

    2016-07-18

    We report the synthesis and characterization of a family of organometallic cobalt(I) metal precursors based around cyclopentadienyl and diene ligands. The molecular structures of the complexes cyclopentadienyl-cobalt(I) diolefin complexes are described, as determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis and thermal stability studies of the complexes highlighted the isoprene, dimethyl butadiene, and cyclohexadiene derivatives [(C5H5)Co(η(4)-CH2CHC(Me)CH2)] (1), [(C5H5)Co(η(4)-CH2C(Me)C(Me)CH2)] (2), and [(C5H5)Co(η(4)-C6H8)] (4) as possible cobalt metal organic chemical vapor deposition (MOCVD) precursors. Atmospheric pressure MOCVD was employed using precursor 1, to synthesize thin films of metallic cobalt on silicon substrates under an atmosphere (760 torr) of hydrogen (H2). Analysis of the thin films deposited at substrate temperatures of 325, 350, 375, and 400 °C, respectively, by scanning electron microscopy and atomic force microscopy reveal temperature-dependent growth features. Films grown at these temperatures are continuous, pinhole-free, and can be seen to be composed of hexagonal particles clearly visible in the electron micrograph. Powder X-ray diffraction and X-ray photoelectron spectroscopy all show the films to be highly crystalline, high-purity metallic cobalt. Raman spectroscopy was unable to detect the presence of cobalt silicides at the substrate/thin film interface. PMID:27348614

  19. Nickel-cobalt alloy nanosheets obtained from reductive hydrothermal-treatment of nickel-cobalt hydroxide carbonate

    SciTech Connect

    Ghotbi, Mohammad Yeganeh; Jolagah, Ali; Afrasiabi, Hasan-ali

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer An anionic layered material, nickel-cobalt hydroxide carbonate was synthesized. Black-Right-Pointing-Pointer Reductive hydrothermal-treatment of the layered precursor produced an alloy. Black-Right-Pointing-Pointer The alloy is a bimetallic nanostructured nickel-cobalt and a soft magnet material. -- Abstract: Nickel-cobalt hydroxide carbonate, a layered material was synthesized by the co-precipitation method using urea as precipitant agent. This anionic layered material with hexagonal structure is constructed from nickel and cobalt ions within the layers and carbonate anions between the layers. Nickel-cobalt alloy with pure cubic phase was obtained by a reductive hydrothermal-treatment of the layered precursor. Powder X-ray diffraction pattern and Fourier transform infrared spectroscopy confirmed the formation of the initial layered material and its metallic alloy product. That is, the nickel-cobalt alloy has really produced via a wet chemical route for the first time. Magnetic measurement revealed that the alloy sample is a soft magnet material.

  20. Cobalt ferrite based magnetostrictive materials for magnetic stress sensor and actuator applications

    NASA Technical Reports Server (NTRS)

    Jiles, David C. (Inventor); Paulsen, Jason A. (Inventor); Snyder, John E. (Inventor); Lo, Chester C. H. (Inventor); Ring, Andrew P. (Inventor); Bormann, Keith A. (Inventor)

    2008-01-01

    Magnetostrictive material based on cobalt ferrite is described. The cobalt ferrite is substituted with transition metals (such manganese (Mn), chromium (Cr), zinc (Zn) and copper (Cu) or mixtures thereof) by substituting the transition metals for iron or cobalt to form substituted cobalt ferrite that provides mechanical properties that make the substituted cobalt ferrite material effective for use as sensors and actuators. The substitution of transition metals lowers the Curie temperature of the material (as compared to cobalt ferrite) while maintaining a suitable magnetostriction for stress sensing applications.

  1. Electromagnetic containerless reaction of samarium with cobalt for the formation of samarium-cobalt alloys

    NASA Technical Reports Server (NTRS)

    Chang, C. W.; Das, D. K.; Kumar, K.; Frost, R. T.

    1982-01-01

    The electromagnetic levitation technique has been used to obtain nearly stoichiometric SmCo5, with the reaction temperature controlled by a gas jet. The results of several experiments carried out at a 450 kHz, 25 kw RF power levitation facility using different reaction times and cooling rates are presented. It is shown that reaction rates achieved with the levitation technique are larger than the expected diffusion rate in the system liquid samarium-solid cobalt. It is also shown that substantial mixing occurs in the RF-levitated melt.

  2. Tuning of magnetic parameters in cobalt-polystyrene nanocomposites by reduction cycling

    SciTech Connect

    Nair, Swapna S.; Sunny, Vijutha; Anantharaman, M.R.

    2011-10-15

    Graphical abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores. A porous polymer network (polystyrene) was chosen as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process. Highlights: {yields} Elementary cobalt nanoparticles were synthesized inside polystyrene by a novel process. {yields} The self protection is achieved by the auto-shelling with the metal oxide. {yields} The magnetisation and coercivity could be tuned by repeating the cycles. {yields} Tuning of magnetic properties (both coercivity and magnetisation) could be achieved by the repetition of reduction cycles. {yields} Synthesized nanocomposite can act as a catalyst for carbon nanotube synthesis. -- Abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO{sub 4}.7H{sub 2}O and NaBH{sub 4}. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The

  3. Gulosibacter molinativorax ON4T Molinate Hydrolase, a Novel Cobalt-Dependent Amidohydrolase ▿ ‡

    PubMed Central

    Duarte, Márcia; Ferreira-da-Silva, Frederico; Lünsdorf, Heinrich; Junca, Howard; Gales, Luís; Pieper, Dietmar H.; Nunes, Olga C.

    2011-01-01

    A new pathway of molinate mineralization has recently been described. Among the five members of the mixed culture able to promote such a process, Gulosibacter molinativorax ON4T has been observed to promote the initial breakdown of the herbicide into ethanethiol and azepane-1-carboxylate. In the current study, the gene encoding the enzyme responsible for molinate hydrolysis was identified and heterologously expressed, and the resultant active protein was purified and characterized. Nucleotide sequence analysis revealed that the gene encodes a 465-amino-acid protein of the metal-dependent hydrolase A subfamily of the amidohydrolase superfamily with a predicted molecular mass of 50.9 kDa. Molinate hydrolase shares the highest amino acid sequence identity (48 to 50%) with phenylurea hydrolases of Arthrobacter globiformis and Mycobacterium brisbanense. However, in contrast to previously described members of the metal-dependent hydrolase A subfamily, molinate hydrolase contains cobalt as the only active-site metal. PMID:21840982

  4. Magnetization measurements on fine cobalt particles

    NASA Astrophysics Data System (ADS)

    Respaud, M.; Broto, J. M.; Rakoto, H.; Ousset, J. C.; Osuna, J.; Ould Ely, T.; Amiens, C.; Chaudret, B.; Askenazy, S.

    1998-05-01

    We measure the magnetization of fine cobalt particles by SQUID and pulsed magnetic fields up to 35 T. These measurements have been made on two samples (C1, C2) with nonagglomerated particles. The analysis of the magnetic meaurements evidences very narrow log-normal size distribution centered around 1.5 nm (≅150 atoms) and 1.9 nm (≅310 atoms) for C1 and C2, respectively. Magnetization at 4.2 K seems to saturate in fields up to 5 T leading to an enhanced mean magnetic moment per atom compared to bulk value (1.72 μB). However, magnetization measurements up to 35 T do not permit to reach saturation, and show a continuous increase of μCo reaching 2.1±0.1 μB (C1) and 1.9±0.1 μB (C2). The effective magnetic anisotropies are found to be larger than those of bulk materials and decrease with increasing particle size. These features are associated with the large influence of the surface atoms.

  5. COBALT-60 Gamma Irradiation of Shrimp.

    NASA Astrophysics Data System (ADS)

    Sullivan, Nancy L. B.

    Meta- and ortho-tyrosine were measured using high performance liquid chromatography (HPLC) in conjunction with electrochemical detection in shrimp irradiated using cobalt-60 gamma radiation in the absorbed dose range 0.8 to 6.0 kGy, in nonirradiated shrimp, and in bovine serum albumin (BSA) irradiated in dilute aqueous solution at 25.0 kGy. Ortho-tyrosine was measured in nonirradiated BSA. Para-, meta-, and ortho-tyrosine were measured using HPLC in conjunction with uv-absorption detection in dilute aqueous solutions of phenylalanine irradiated in the absorbed dose range 16.0 to 195.0 kGy. The measured yields of tyrosine isomers were approximately linear as a function of absorbed dose in shrimp, and in irradiated solutions of phenylalanine up to 37.0 kGy. The occurrence of meta- and ortho-tyrosine, which had formerly been considered unique radiolytic products, has not previously been reported in nonirradiated shrimp or BSA. The conventional hydrolyzation and analytical techniques used in the present study to measure meta- and ortho-tyrosine may provide the basis for a method to detect and determine the dose used in food irradiation.

  6. Spinel cobalt ferrite by complexometric synthesis

    NASA Astrophysics Data System (ADS)

    Thang, Pham D.; Rijnders, Guus; Blank, Dave H. A.

    2005-09-01

    Magnetic fine particles of cobalt ferrite (CoFe 2O 4) have been synthesized using complexometric method in which ethylene diamine tetra acetic acid C 10H 16N 2O 8 (EDTA) acts as a complexing agent. The crystallographic structure, microstructure and magnetic properties of the synthesized powder were characterized by using X-ray diffraction (XRD), particle size analysis and vibrating sample magnetometry (VSM). The material crystallized in cubic spinel structure with lattice parameter of about 8.38 Å. Depending on the calcining temperature, the particle size of the powders varies in the range of hundreds of nanometers to tens of micrometers. A desired relative density above 95% of the theoretical value is obtained for the bulk sample after sintering. The calcined powders and sintered sample exhibit saturation magnetizations around 80 Am 2/kg which is expected for inverse CoFe 2O 4. With increasing calcining temperature the coercivity of these samples decreases. This simple synthesis route leads to a reproducible and stoichiometric material.

  7. Water Adsorption on Free Cobalt Cluster Cations.

    PubMed

    Kiawi, Denis M; Bakker, Joost M; Oomens, Jos; Buma, Wybren Jan; Jamshidi, Zahra; Visscher, Lucas; Waters, L B F M

    2015-11-01

    Cationic cobalt clusters complexed with water Con(+)-H2O (n = 6-20) are produced through laser ablation and investigated via infrared multiple photon dissociation (IR-MPD) spectroscopy in the 200-1700 cm(-1) spectral range. All spectra exhibit a resonance close to the 1595 cm(-1) frequency of the free water bending vibration, indicating that the water molecule remains intact upon adsorption. For n = 6, the frequency of this band is blue-shifted, but it gradually converges to the free water value with increasing cluster size. In the lower-frequency range (200-650 cm(-1)) the spectra contain several bands which show a very regular frequency evolution, suggesting that the exact cluster geometry has little effect on the water-surface interaction. Density functional theory (DFT) calculations are carried out at the OPBE/TZP level for three representative sizes (n = 6, 9, 13) and indicate that the vibrations responsible for the resonances correspond to bending and torsional modes between the cluster and water moieties. The potential energy surfaces describing these interactions are very shallow, making the calculated harmonic frequencies and IR intensities very sensitive to small geometrical perturbations. We conclude that harmonic frequency calculations on (local) minima structures provide insufficient information for these types of cluster complexes and need to be complemented with calculations that provide a more extensive sampling of the potential energy surface. PMID:26447780

  8. Cobalt-60 gamma irradiation of shrimp

    SciTech Connect

    Sullivan, N.L.B.

    1993-01-01

    Meta- and ortho-tyrosine were measured using high performance liquid chromatography (HPLC) in conjunction with electrochemical detection in shrimp irradiated using cobalt-60 gamma radiation in the absorbed dose range 0.8 to 6.0 kGy, in nonirradiated shrimp, and in bovine serum albumin (BSA) irradiated in dilute aqueous solution at 25.0 kGy. Ortho-tyrosine was measured in nonirradiated BSA. Para-, meta-, and ortho-tyrosine was measured using HPLC in conjunction with uv-absorption detection in dilute aqueous solutions of phenylalanine irradiated in the absorbed dose range 16.0 to 195.0 kGy. The measured yields of tyrosine isomers were approximately linear as a function of absorbed dose in shrimp, and in irradiated solutions of phenylalanine up to 37.0 kGy. The occurrence of meta- and ortho-tyrosine, which had formerly been considered unique radiolytic products, has not previously been reported in nonirradiated shrimp or BSA. The conventional hydrolyzation and analytical techniques used in the present study to measure meta- and ortho-tyrosine may provide the basis for a method to detect and determine the dose used in food irradiation.

  9. Structure of yttrium cobaltate from neutron diffraction

    SciTech Connect

    Mehta, A.; Berliner, R.; Smith, R.W.

    1997-05-01

    The crystal structure of YCoO{sub 3} has been determined from Rietveld analysis of the powder neutron diffraction data at 17, 100, and 300 K. At each temperature, the structure is a distorted perovskite with orthorhombic symmetry, space group Pbnm (Z = 4). The lattice parameters, at 300 K, are 5.1388 (5) x 5.4191(5) x 7.3658(7) {angstrom}. Structural analysis indicates that the formal valence of cobalt in YCoO{sub 3} is +3. Analysis of the Co-O distances and the absence of magnetic structure indicates that the majority of the Co{sup 3+} ions in YCoO{sub 3} are in the low-spin (i.e. t{sub 2g}{sup 6}e{sub g}{sup 0}) state. The data also show that perhaps 10% of the CO{sup 3+} ions at 300 K (but insignificant fractions at 100 and 17 K) are in the high-spin state.

  10. Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.

    PubMed

    Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2013-12-01

    Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan δ) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces. PMID:24145704

  11. Two dimensionality in quasi-one-dimensional cobalt oxides

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Nozaki, H.; Brewer, J. H.; Ansaldo, E. J.; Morris, G. D.; Takami, T.; Ikuta, H.; Mizutani, U.

    2006-03-01

    Magnetism of quasi-one-dimensional (1D) cobalt oxides ACoO ( A=Ca, Sr and Ba, n=1-5 and ∞) was investigated by μ+SR using polycrystalline samples, at temperatures from 300 K down to 1.8 K. The wTF- μ+SR experiments showed the existence of a magnetic transition in all six samples investigated. The onset temperature of the transition (Tcon) was found to decrease with n; that is, 100±25, 90±10, 85±10, 65±10 50±10, and 15±1 K for n=1-5, and ∞, respectively. In particular, for the samples with n=2-5, Tcon was detected only by the present μ+SR measurements. A muon spin oscillation was clearly observed in both Ca 3Co 2O 6(n=1) and BaCoO 3(n=∞), whereas only a fast relaxation is apparent even at 1.8 K in the other four samples ( n=2-5). Taking together with the fact that the paramagnetic Curie temperature ranges from -150 to -200 K for the compound with n=2 and 3, the μ+SR result indicates that a two-dimensional (2D) short-range antiferromagnetic (AF) order, which has been thought to be unlikely to exist at high T due to a relatively strong 1D F interaction, appears below Tcon for all compounds with n=1-5; but quasi-static long-range AF order formed only in Ca 3Co 2O 6, below 25 K. For BaCoO 3(n=∞), as T decreased from 300 K, 1D F order appeared below 53 K, and a sharp 2D AF transition occurred at 15 K.

  12. Determination of cobalt in samples containing cobalt and tungsten carbide by electrothermal atomic absorption spectrometry

    SciTech Connect

    Firriolo, J.M.; Kutzman, R.S.

    1985-09-01

    A method has been developed to determine the amount of cobalt (Co) in atmospheric dust samples which include free and sintered Co. Cobalt and tungsten carbide (WC) mixtures ranging from 0-100% Co were prepared for atomic absorption analysis by dissolving the Co in aqua regia. Using this method, the amount of Co in the samples assayed ranged from 90.9-100.1% of that gravimetrically added to the mixtures. The results of this aqua regia dissolution procedure for Co were compared to a hydrofluoric acid method which solubilized both the Co and the WC. Application of the aqua regia dissolution method to samples of sintered WC and Co dust resulted in complete recovery of the Co from these materials. These results were supported by x-ray analysis of the samples before and after dissolution of the Co with aqua regia. The described procedure is advantageous because it avoids the use of highly-caustic hydrofluoric acid and the results are quickly available.

  13. Microstructure and Magnetic Properties of Electrodeposited Cobalt Film

    SciTech Connect

    Bhuiyan, Md S; Taylor, B. J.; Paranthaman, Mariappan Parans; Thompson, James R; Sinclair, J.

    2008-01-01

    Cobalt films were electrodeposited onto both iron and copper substrates from an aqueous solution containing a mixture of cobalt sulfate, boric acid, sodium citrate, and vanadyl sulfate. The structural, intermetallic diffusion and magnetic properties of the electrodeposited films were studied. Cobalt electrodeposition was carried out in a passively divided cell aided by addition of vanadyl sulfate to keep the counter electrode clean. The divided electrolytic cell with very negative current densities cause the electrodeposited Co to adopt a face-centered cubic (fcc) structure, which is more magnetically reversible than the hexagonally close-packed (hcp) structured Co. The coercive field is also significantly less in the fcc-electrodeposited cobalt than in the hcp. SEM images show dense, uniform Co films without any cracks or porosity. Beside the deposition current, thickness of the film was also found to affect the crystal orientation particularly on iron substrates. Diffusion of cobalt film into the iron substrate was studied under reduced environment and a fast process was observed.

  14. Graphene/cobalt nanocarrier for hyperthermia therapy and MRI diagnosis.

    PubMed

    Hatamie, Shadie; Ahadian, Mohammad Mahdi; Ghiass, Mohammad Adel; Iraji Zad, Azam; Saber, Reza; Parseh, Benyamin; Oghabian, Mohammad Ali; Shanehsazzadeh, Saeed

    2016-10-01

    Graphene/cobalt nanocomposites are promising materials for theranostic nanomedicine applications, which are defined as the ability to diagnose, provide targeted therapy and monitor the response to the therapy. In this study, the composites were synthesized via chemical method, using graphene oxide as the source material and assembling cobalt nanoparticles of 15nm over the surface of graphene sheets. Various characterization techniques were then employed to reveal the morphology, size and structure of the nanocomposites, such as X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high resolution transmission electron microscopy and ultraviolet visible spectroscopy. Using ion-coupled plasma optical emission spectroscopy, cobalt concentration in the nanocomposites was found to be 80%. In addition, cytotoxicity of graphene/cobalt nanocomposites were evaluated using 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide or MTT assay. MTT viability assay exhibited biocompatibility to L929 mouse fibroblasts cells, under a high dose of 100μg/mL over 24h. Hyperthermia results showed the superior conversion of electromagnetic energy into heat at 350kHz frequency for 0.01 and 0.005g/L of the nanocomposites solution. The measured heat generation and energy transfer results were anticipated by the finite element analysis, conducted for the 3D structure. Magnetic resonance imaging characteristics also showed that negatively charge graphene/cobalt nanocomposites are suitable for T1-weighted imaging. PMID:27351138

  15. 40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium cobalt lead titanium tungsten... Specific Chemical Substances § 721.10599 Calcium cobalt lead titanium tungsten oxide. (a) Chemical... cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1) is subject to reporting...

  16. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  17. 40 CFR 471.30 - Applicability; description of the nickel-cobalt forming subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... nickel-cobalt forming subcategory. 471.30 Section 471.30 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Nickel-Cobalt Forming Subcategory § 471.30 Applicability; description of the nickel-cobalt forming subcategory. This subpart applies to discharges of pollutants...

  18. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  19. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cobalt iron manganese oxide... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35)...

  20. 40 CFR 421.230 - Applicability: Description of the primary nickel and cobalt subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary nickel and cobalt subcategory. 421.230 Section 421.230 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Nickel and Cobalt Subcategory § 421.230 Applicability: Description of the primary nickel and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  1. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting...

  2. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt iron manganese oxide... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35)...

  3. 40 CFR 471.30 - Applicability; description of the nickel-cobalt forming subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... nickel-cobalt forming subcategory. 471.30 Section 471.30 Protection of Environment ENVIRONMENTAL... POINT SOURCE CATEGORY Nickel-Cobalt Forming Subcategory § 471.30 Applicability; description of the nickel-cobalt forming subcategory. This subpart applies to discharges of pollutants to waters of...

  4. Comparison of different supplemental cobalt forms on fiber digestion and cobalamin levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cobalt (Co) is essential for rumen microbial metabolism to synthesize methane, acetate and methionine. It also serves as a structural component of vitamin B*12, which functions as a coenzyme in energy metabolism. A study was conducted to determine if Co form (cobalt carbonate vs cobalt glucoheptona...

  5. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  6. 40 CFR 471.30 - Applicability; description of the nickel-cobalt forming subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... nickel-cobalt forming subcategory. 471.30 Section 471.30 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Nickel-Cobalt Forming Subcategory § 471.30 Applicability; description of the nickel-cobalt forming subcategory. This subpart applies to discharges of pollutants...

  7. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  8. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  9. 40 CFR 421.230 - Applicability: Description of the primary nickel and cobalt subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary nickel and cobalt subcategory. 421.230 Section 421.230 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Nickel and Cobalt Subcategory § 421.230 Applicability: Description of the primary nickel and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  10. 40 CFR 471.30 - Applicability; description of the nickel-cobalt forming subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... nickel-cobalt forming subcategory. 471.30 Section 471.30 Protection of Environment ENVIRONMENTAL... POINT SOURCE CATEGORY Nickel-Cobalt Forming Subcategory § 471.30 Applicability; description of the nickel-cobalt forming subcategory. This subpart applies to discharges of pollutants to waters of...

  11. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting...

  12. 40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject...

  13. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  14. Comparison of different supplemental cobalt forms on digestion and cobalamin levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cobalt (Co) is essential for rumen microbial metabolism to synthesize methane, acetate and methionine. It also serves as a structural component of vitamin B12, which functions as a coenzyme in energy metabolism. A study was conducted to determine if Co form (cobalt carbonate vs cobalt glucoheptonat...

  15. 40 CFR 721.5315 - Nickel, cobalt mixed metal oxide (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Nickel, cobalt mixed metal oxide... Specific Chemical Substances § 721.5315 Nickel, cobalt mixed metal oxide (generic). (a) Chemical substance... nickel, cobalt mixed metal oxide. (PMN P-02-90) is subject to reporting under this section for...

  16. 40 CFR 471.30 - Applicability; description of the nickel-cobalt forming subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... nickel-cobalt forming subcategory. 471.30 Section 471.30 Protection of Environment ENVIRONMENTAL... METAL POWDERS POINT SOURCE CATEGORY Nickel-Cobalt Forming Subcategory § 471.30 Applicability; description of the nickel-cobalt forming subcategory. This subpart applies to discharges of pollutants...

  17. The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.

    1985-01-01

    The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.

  18. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  19. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  20. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting...

  1. 40 CFR 721.10600 - Calcium cobalt lead strontium titanium tungsten oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Calcium cobalt lead strontium titanium... Specific Chemical Substances § 721.10600 Calcium cobalt lead strontium titanium tungsten oxide. (a... calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS No. 1262279-30-0) is subject...

  2. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting...

  3. 40 CFR 721.10599 - Calcium cobalt lead titanium tungsten oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Calcium cobalt lead titanium tungsten... Specific Chemical Substances § 721.10599 Calcium cobalt lead titanium tungsten oxide. (a) Chemical... cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1) is subject to reporting...

  4. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the secondary tungsten and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting...

  5. 40 CFR 421.230 - Applicability: Description of the primary nickel and cobalt subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary nickel and cobalt subcategory. 421.230 Section 421.230 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Nickel and Cobalt Subcategory § 421.230 Applicability: Description of the primary nickel and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  6. 40 CFR 421.230 - Applicability: Description of the primary nickel and cobalt subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary nickel and cobalt subcategory. 421.230 Section 421.230 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Nickel and Cobalt Subcategory § 421.230 Applicability: Description of the primary nickel and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  7. 40 CFR 421.230 - Applicability: Description of the primary nickel and cobalt subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary nickel and cobalt subcategory. 421.230 Section 421.230 Protection of Environment ENVIRONMENTAL... CATEGORY Primary Nickel and Cobalt Subcategory § 421.230 Applicability: Description of the primary nickel and cobalt subcategory. The provisions of this subpart are applicable to discharges resulting from...

  8. 21 CFR 73.3110a - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium-cobalt-aluminum oxide. 73.3110a Section... LISTING OF COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3110a Chromium-cobalt-aluminum oxide. (a) Identity. The color additive chromium-cobalt-aluminum oxide (Pigment Blue 36) (CAS Reg....

  9. Toxicity of cobalt. (Latest citations from the Life Sciences Collection database). Published Search

    SciTech Connect

    Not Available

    1993-02-01

    The bibliography contains citations concerning the toxicity effects of cobalt. Citations include cobalt fetotoxicity, renal toxicity, bioaccumulation, contact dermatitis, carcinogencity, and respiratory disorders. Toxicology assays and industrial sources of cobalt poisoning are considered. In vivo and in vitro human and animal studies are described. (Contains a minimum of 129 citations and includes a subject term index and title list.)

  10. Lignite recovery of cobalt(+3) from an ammoniacal ammonium sulfate solution. Report of investigations/1984

    SciTech Connect

    Slavens, G.J.; Traut, D.E.; Penner, L.R.; Henry, J.L.

    1984-01-01

    The Bureau of Mines has devised technology to recover cobalt, nickel, and byproduct copper from domestic lateritic material using an oxidative, ammoniacal ammonium sulfate leach. Nickel, cobalt, and copper were recovered by solvent extraction and electrowinning. To reduce the cost and complexity of cobalt recovery, an alternate method using lignite to extract Co(+3) was investigated as reported herein.

  11. Thermal fatigue resistance of cobalt-modified UDIMET 700

    NASA Technical Reports Server (NTRS)

    Bizon, P. T.

    1982-01-01

    The determination of comparative thermal fatigue resistances of five cobalt composition modifications of UDIMET 700 from fluidized bed tests is described. Cobalt compositional levels of 0.1, 4.3, 8.6, 12.8, 17.0 percent were being investigated in both the bare and coated (NiCrAlY overlay) conditions. Triplicate tests of each variation including duplicate tests of three control alloys are under investigation. Fluidized beds were maintained at 550 and 1850 F for the first 5500 cycles at which time the hot bed was increased to 1922 F. Immersion time in each bed is always 3 minutes. Upon the completion of 10,000 cycles, it appears that the 8.6 percent cobalt level gives the best thermal fatigue life. Considerable deformation of the test bars was observed.

  12. Nanosize cobalt boride particles: Control of the size and properties

    NASA Astrophysics Data System (ADS)

    Petit, C.; Pileni, M. P.

    1997-02-01

    Cobalt boride is obtained by the reduction of cobalt (2-ethyl hexyl) sulfosuccinate, Co(AOT) 2, by sodium borohydride either in reverse micelles or in a diphasic system. In Co(AOT) 2/Na(AOT)/H 2O reverse micellar solution, the size and polydispersity of the Co 2B particles is controlled by the size of the water droplets, which increases from 4 to 7.5 nm by increasing the water content. In a diphasic system of Co(AOT) 2/isooctane and sodium borohydride in aqueous solution, large and polydisperse particles of cobalt boride are formed (˜ 10 nm), and their magnetization properties are presented. The smallest particles are in a superparamagnetic regime at room temperature, whereas the largest particles show ferromagnetic behavior.

  13. Tungsten-nickel-cobalt alloy and method of producing same

    DOEpatents

    Dickinson, James M.; Riley, Robert E.

    1977-03-15

    An improved tungsten alloy having a tungsten content of approximately 95 weight percent, a nickel content of about 3 weight percent, and the balance being cobalt of about 2 weight percent is described. A method for producing said tungsten-nickel-cobalt alloy is further described and comprises (a) coating the tungsten particles with a nickel-cobalt alloy, (b) pressing the coated particles into a compact shape, (c) heating said compact in hydrogen to a temperature in the range of 1400.degree. C and holding at this elevated temperature for a period of about 2 hours, (d) increasing this elevated temperature to about 1500.degree. C and holding for 1 hour at this temperature, (e) cooling to about 1200.degree. C and replacing the hydrogen atmosphere with an inert argon atmosphere while maintaining this elevated temperature for a period of about 1/2 hour, and (f) cooling the resulting alloy to room temperature in this argon atmosphere.

  14. Effect of Cobalt Particle Size on Acetone Steam Reforming

    SciTech Connect

    Sun, Junming; Zhang, He; Yu, Ning; Davidson, Stephen D.; Wang, Yong

    2015-06-11

    Carbon-supported cobalt nanoparticles with different particle sizes were synthesized and characterized by complementary characterization techniques such as X-ray diffraction, N-2 sorption, acetone temperature-programmed desorption, transmission electron microscopy, and CO chemisorption. Using acetone steam reforming reaction as a probe reaction, we revealed a volcano-shape curve of the intrinsic activity (turnover frequency of acetone) and the CO2 selectivity as a function of the cobalt particle size with the highest activity and selectivity observed at a particle size of approximately 12.8nm. Our results indicate that the overall performance of acetone steam reforming is related to a combination of particle-size-dependent acetone decomposition, water dissociation, and the oxidation state of the cobalt nanoparticles.

  15. Activation of cobalt by neutrons from the Hiroshima bomb

    SciTech Connect

    Kerr, G.D.; Dyer, F.F.; Emery, J.F.; Pace, J.V. III ); Brodzinski, R.L. ); Marcum, J. )

    1990-02-01

    A study has been completed of cobalt activation in samples from two new locations in Hiroshima. The samples consisted of a piece of steel from a bridge located at a distance of about 1300 m from the hypocenter and pieces of both steel and concrete from a building located at approximately 700 m. The concrete was analyzed to obtain information needed to calculate the cobalt activation in the two steel samples. Close agreement was found between calculated and measured values for cobalt activation of the steel sample from the building at 700 m. It was found, however, that the measured values for the bridge sample at 1300 m were approximately twice the calculated values. Thus, the new results confirm the existence of a systematic error in the transport calculations for neutrons from the Hiroshima bomb. 52 refs., 32 figs., 16 tabs.

  16. Transition metal-substituted cobalt ferrite nanoparticles for biomedical applications.

    PubMed

    Sanpo, Noppakun; Berndt, Christopher C; Wen, Cuie; Wang, James

    2013-03-01

    Transition metals of copper, zinc, chromium and nickel were substituted into cobalt ferrite nanoparticles via a sol-gel route using citric acid as a chelating agent. The microstructure and elemental composition were characterized using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. Phase analysis of transition metal-substituted cobalt ferrite nanoparticles was performed via X-ray diffraction. Surface wettability was measured using the water contact angle technique. The surface roughness of all nanoparticles was measured using profilometry. Moreover, thermogravimetric analysis and differential scanning calorimetry were performed to determine the temperature at which the decomposition and oxidation of the chelating agents took place. Results indicated that the substitution of transition metals influences strongly the microstructure, crystal structure and antibacterial property of the cobalt ferrite nanoparticles. PMID:23137676

  17. Sorption and desorption of cobalt by Oscillatoria anguistissima.

    PubMed

    Ahuja, P; Gupta, R; Saxena, R K

    1999-07-01

    Oscillatoria anguistissima rapidly adsorbs appreciable amounts of cobalt from the aqueous solutions within 15 min of initial contact with the metal solution. O. anguistissima showed a high sequestration of cobalt at low equilibrium concentrations, and it followed the Freundlich model of adsorption. The adsorption is a strongly pH-dependent and temperature-independent phenomenon. The presence of Mg2+ and Ca2+ (100-200 ppm) resulted in decline in Co2+ adsorption capacity of Oscillatoria biomass. Sulphate and nitrate (0. 75-10 mM) drastically reduced the extent of Co2+ biosorption. The biosorption of cobalt is an ion-exchange process as the Co2+ binding was accompanied by release of a large amounts of Mg2+ ions. Na2CO3 (1.0 mM) resulted in about 76% desorption of Co2+ from the loaded biomass. PMID:10387117

  18. Recovery of cobalt and copper from complex sulfide concentrates

    SciTech Connect

    Dannenberg, R.O.; Gardner, P.C.; Crane, S.R.; Seidel, D.C.

    1987-01-01

    The Bureau conducted bench-scale research on a process for treating cobaltite concentrates, comprising (1) oxidative pressure leaching, (2) jarosite precipitation followed by H/sub 2/O/sub 2/ oxidation and pH control to remove iron and arsenic, (3) copper solvent extraction with a mixed hydroxyoxime-amine extractant, (4) copper electrowinning from recirculating acidic strip liquor, (5) selective cobalt extraction from copper solvent extraction raffinate with a phosphinic and extractant, and (6) electrowinning of cobalt from a recirculating weak acid strip liquor. Overall cobalt and copper recoveries were 91.7 and 84.1 pct, respectively. Electrowon products assayed 99.8 pct Co and 99.89 ct Cu.

  19. Spin relaxation in graphene with self-assembled cobalt porphyrin molecules

    NASA Astrophysics Data System (ADS)

    Omar, S.; Gurram, M.; Vera-Marun, I. J.; Zhang, X.; Huisman, E. H.; Kaverzin, A.; Feringa, B. L.; van Wees, B. J.

    2015-09-01

    In graphene spintronics, interaction of localized magnetic moments with the electron spins paves a new way to explore the underlying spin-relaxation mechanism. A self-assembled layer of organic cobalt porphyrin (CoPP) molecules on graphene provides a desired platform for such studies via the magnetic moments of porphyrin-bound cobalt atoms. In this work a study of spin-transport properties of graphene spin-valve devices functionalized with such CoPP molecules as a function of temperature via nonlocal spin-valve and Hanle spin-precession measurements is reported. For the functionalized (molecular) devices, we observe a decrease in the spin-relaxation time τs even up to 50%, which could be an indication of enhanced spin-flip scattering of the electron spins in graphene in the presence of the molecular magnetic moments. The effect of the molecular layer is masked for low-quality samples (low mobility), possibly due to dominance of Elliot-Yafet-type spin relaxation mechanisms.

  20. Synthesis and catalytic properties of eggshell cobalt catalysts for the Fischer-Tropsch synthesis

    SciTech Connect

    Iglesia, E.; Soled, S.L.; Baumgartner, J.E.

    1995-04-15

    CO diffusional restrictions decrease the rate and C{sup +}{sub 5} selectivity in large (1-3 mm) catalyst pellets required for Fischer-Tropsch synthesis in packed bed reactors. Eggshell catalysts, in which the active Co component is preferentially located near the outer pellet surface, decrease these transport restrictions and increase Fischer-Tropsch synthesis rates and C{sup +}{sub 5} selectivity. Maximum C{sup +}{sub 5} selectivities occur on catalysts with intermediate shell thickness, because these catalysts avoid intrapellet CO concentration gradients but still restrict the diffusive removal of reactive olefin products, which can readsorb and continue to grow to higher molecular weight hydrocarbons. Eggshell catalysts were prepared by a novel impregnation technique using molten cobalt nitrate. The eggshell thickness is controlled by the melt viscosity and by the contact time between the melt and the support pellet. These impregnation procedures and the slow reduction of the impregnated nitrate salts lead to relatively high cobalt dispersions (0.05-0.07) even at the high Co concentrations (40-50 wt%) present within the shell region. 51 refs., 8 figs., 4 tabs.

  1. 50 CFR 32.50 - New Mexico.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 6 2010-10-01 2010-10-01 false New Mexico. 32.50 Section 32.50 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE... § 32.50 New Mexico. The following refuge units have been opened for hunting and/or fishing, and...

  2. Mycobacterial Cells Have Dual Nickel-Cobalt Sensors

    PubMed Central

    Campbell, Duncan R.; Chapman, Kaye E.; Waldron, Kevin J.; Tottey, Stephen; Kendall, Sharon; Cavallaro, Gabriele; Andreini, Claudia; Hinds, Jason; Stoker, Neil G.; Robinson, Nigel J.; Cavet, Jennifer S.

    2011-01-01

    A novel ArsR-SmtB family transcriptional repressor, KmtR, has been characterized from mycobacteria. Mutants of Mycobacterium tuberculosis lacking kmtR show elevated expression of Rv2025c encoding a deduced CDF-family metal exporter. KmtR-dependent repression of the cdf and kmtR operator-promoters was alleviated by nickel and cobalt in minimal medium. Electrophoretic mobility shift assays and fluorescence anisotropy show binding of purified KmtR to nucleotide sequences containing a region of dyad symmetry from the cdf and kmtR operator-promoters. Incubation of KmtR with cobalt inhibits DNA complex assembly and metal-protein binding was confirmed. KmtR is the second, to NmtR, characterized ArsR-SmtB sensor of nickel and cobalt from M. tuberculosis suggesting special significance for these ions in this pathogen. KmtR-dependent expression is elevated in complete medium with no increase in response to metals, whereas NmtR retains a response to nickel and cobalt under these conditions. KmtR has tighter affinities for nickel and cobalt than NmtR consistent with basal levels of these metals being sensed by KmtR but not NmtR in complete medium. More than a thousand genes encoding ArsR-SmtB-related proteins are listed in databases. KmtR has none of the previously defined metal-sensing sites. Substitution of His88, Glu101, His102, His110, or His111 with Gln generated KmtR variants that repress the cdf and kmtR operator-promoters even in elevated nickel and cobalt, revealing a new sensory site. Importantly, ArsR-SmtB sequence groupings do not correspond with the different sensory motifs revealing that only the latter should be used to predict metal sensing. PMID:17726022

  3. Temporal Variability of Tungsten and Cobalt in Fallon, Nevada

    PubMed Central

    Sheppard, Paul R.; Speakman, Robert J.; Ridenour, Gary; Witten, Mark L.

    2007-01-01

    Background Since 1997, Fallon, Nevada, has experienced a cluster of childhood leukemia that has been declared “one of the most unique clusters of childhood cancer ever reported.” Multiple environmental studies have shown airborne tungsten and cobalt to be elevated within Fallon, but the question remains: Have these metals changed through time in correspondence with the onset of the leukemia cluster? Methods We used dendrochemistry, the study of element concentrations through time in tree rings, in Fallon to assess temporal variability of airborne tungsten and cobalt since the late 1980s. The techniques used in Fallon were also tested in a different town (Sweet Home, OR) that has airborne tungsten from a known source. Results The Sweet Home test case confirms the accuracy of dendrochemistry for showing temporal variability of environmental tungsten. Given that dendrochemistry works for tungsten, tree-ring chemistry shows that tungsten increased in Fallon relative to nearby comparison towns beginning by the mid-1990s, slightly before the onset of the cluster, and cobalt has been high throughout the last ~ 15 years. Other metals do not show trends through time in Fallon. Discussion Results in Fallon suggest a temporal correspondence between the onset of excessive childhood leukemia and elevated levels of tungsten and cobalt. Although environmental data alone cannot directly link childhood leukemia with exposure to metals, research by others has shown that combined exposure to tungsten and cobalt can be carcinogenic to humans. Conclusion Continued biomedical research is warranted to directly test for linkage between childhood leukemia and tungsten and cobalt. PMID:17520058

  4. The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1986-01-01

    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m(PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. The cobalt levels ranged from 0 wt % to the nominal commercial content in each alloy. The alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200 and 100 hr respectively. An oxidation attack parameter, Ka derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the CR/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr alloys while a 5.0 wt % Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides perhaps due to the formation of the omni-present trirutile Ni(Ta,Cb,Mo,W)2O6. Both scales break down as increasing amounts of NiO is formed.

  5. The effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.

    1987-01-01

    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m (PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. the cobalt levels ranged from 0 wt pct to the nominal commercial content in each alloy. the alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200, and 100 hr, respectively. An oxidation attack parameter, Ka, derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr2O3/chromite spinel or Al2O3/aluminate spinel depending on the Cr/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al2O3/aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr allys while a 5.0 wt pct Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides, perhaps due to the formation of the omnipresent trirutile Ni(Ta, Cb, Mo, W)2O6. Both scales break down as increasing amounts of NiO are formed.

  6. Improvements in cobalt determination by thermospray flame furnace atomic absorption spectrometry using an on-line derivatization strategy.

    PubMed

    Matos, Geraldo Domingues; Arruda, Marco Aurélio Zezzi

    2008-07-15

    An on-line derivatization strategy was developed for improving cobalt sensitivity using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) as the analytical technique. This strategy involves the generation of a volatile cobalt compound, providing better sample vaporization efficiency. The effect of sodium diethyldithiocarbamate (DDTC) as complexing agent on the integrated absorbance signal was evaluated. Parameters including the pH of complex formation, complex concentration and volume, sample volume, flame gas composition and tube atomization configuration were optimized. A wide linear range (from 23 microg L(-1) to 3 mg L(-1); r(2)=0.9786) was obtained, with the best one (r(2)=0.9992) attained from 23 to 400 microg L(-1) with a sample throughput of 30 h(-1). The improvement in the detection power was 17-fold when compared to FAAS, which provides 7 microg L(-1) as the limit of detection when considered TS-FF-AAS technique. A relative standard deviation (n=10) of 4% for a cobalt solution containing 50 microg L(-1) was attained, and the accuracy of the procedure was evaluated through certified reference materials (IAEA-SL-1, lake sediment; and ISS-MURST-A1, Antarctic marine sediment). Good agreement between the results at the 95% confidence level was observed. PMID:18585309

  7. Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method

    SciTech Connect

    Prathapani, Sateesh; Jayaraman, Tanjore V. E-mail: tvjayaraman@gmail.com; Varaprasadarao, Eswara K.; Das, Dibakar E-mail: tvjayaraman@gmail.com

    2014-07-14

    Er-substituted cobalt-ferrites CoFe{sub 2−x}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04) were synthesized by sol-gel assisted auto-combustion method. The precursor powders were calcined at 673–873 K for 4 h, subsequently pressed into pellets and sintered at 1273 K for 4 h. X-ray diffraction (XRD) confirmed the presence of the spinel phase for all the compositions and, additional orthoferrite phase for higher compositions (x = 0.03 and 0.04). The XRD spectra and the Transmission Electron Microscopy micrographs indicate that the nanocrystalline particulates of the Er-substituted cobalt ferrites have crystallite size of ∼120–200 nm. The magnetization curves show an increase in saturation magnetization (M{sub S}) and coercivity (H{sub C}) for Er-substituted cobalt-ferrites at sub-ambient temperatures. M{sub S} for CoFe{sub 2}O{sub 4}, CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.97}Er{sub 0.03}O{sub 4} peak at 89.7 Am{sup 2}/kg, 89.3 Am{sup 2}/kg, 88.8 Am{sup 2}/kg, and 87.1 Am{sup 2}/kg, respectively, at a sub-ambient temperature of ∼150 K. H{sub C} substantially increases with decrease in temperature for all the compositions, while it peaks at x = 0.01−0.02 at all temperatures. The combination of Er content—x ∼ 0.02 and the temperature—∼5 K provides the maximum H{sub C} ∼ 984 kA/m. Er-substituted cobalt-ferrites have higher cubic anisotropy constant, K{sub 1}, compared to pure cobalt-ferrite at ambient/sub-ambient temperatures. K{sub 1} gradually increases for all compositions in the temperature decreasing from 300 to 100 K. While K{sub 1} peaks at ∼150 K for pure cobalt-ferrite, it peaks at ∼50 K for CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.96}Er{sub 0.04}O{sub 4}. The M{sub S} (∼88.7 Am{sup 2}/kg), at 5 K, for Er substituted cobalt-ferrite is close to the highest values reported for Sm and Gd

  8. Occupational exposure to heavy metals: DNA damage induction and DNA repair inhibition prove co-exposures to cadmium, cobalt and lead as more dangerous than hitherto expected.

    PubMed

    Hengstler, Jan G; Bolm-Audorff, Ulrich; Faldum, Andreas; Janssen, Kai; Reifenrath, Michael; Götte, Walter; Jung, Detlev; Mayer-Popken, Otfried; Fuchs, Jürgen; Gebhard, Susanne; Bienfait, Heinz Günter; Schlink, Kirsten; Dietrich, Cornelia; Faust, Dagmar; Epe, Bernd; Oesch, Franz

    2003-01-01

    instance increasing lead air concentrations from 1.6 to 50 micro g/m(3) in the presence of constant exposures to cobalt and cadmium (8 micro g/m(3) and 3.8 micro g/m(3)) leads to an almost 5-fold increase in the odds ratio, although lead alone does not increase DNA-SSB. The mechanism behind these interactions might be repair inhibition of oxidative DNA damage, since a decrease in repair capacity will increase susceptibility to reactive oxygen species generated by cadmium or cobalt. Indeed, repair of 8-oxoguanine decreased with increasing exposures and inversely correlated with the level of DNA-SSB (P = 0.001, R = -0.427). Protein expression patterns of individuals exposed to cobalt concentrations of approximately 10 micro g/m(3) were compared with those of unexposed individuals using two-dimensional gel electrophoresis. Qualitative and apparent quantitative alterations in protein expression were selective and certainly occurred in <0.1% of all proteins. In conclusion, the hazard due to cobalt exposure - that has been classified only as IIB by the IARC - seems to be underestimated, especially when individuals are co-exposed to cadmium or lead. Co-exposure may cause genotoxic effects, even if the concentrations of individual heavy metals do not exceed TRK-values. PMID:12538350

  9. Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method

    NASA Astrophysics Data System (ADS)

    Prathapani, Sateesh; Jayaraman, Tanjore V.; Varaprasadarao, Eswara K.; Das, Dibakar

    2014-07-01

    Er-substituted cobalt-ferrites CoFe2-xErxO4 (0 ≤ x ≤ 0.04) were synthesized by sol-gel assisted auto-combustion method. The precursor powders were calcined at 673-873 K for 4 h, subsequently pressed into pellets and sintered at 1273 K for 4 h. X-ray diffraction (XRD) confirmed the presence of the spinel phase for all the compositions and, additional orthoferrite phase for higher compositions (x = 0.03 and 0.04). The XRD spectra and the Transmission Electron Microscopy micrographs indicate that the nanocrystalline particulates of the Er-substituted cobalt ferrites have crystallite size of ˜120-200 nm. The magnetization curves show an increase in saturation magnetization (MS) and coercivity (HC) for Er-substituted cobalt-ferrites at sub-ambient temperatures. MS for CoFe2O4, CoFe0.99Er0.01O4, CoFe0.98Er0.02O4, and CoFe0.97Er0.03O4 peak at 89.7 Am2/kg, 89.3 Am2/kg, 88.8 Am2/kg, and 87.1 Am2/kg, respectively, at a sub-ambient temperature of ˜150 K. HC substantially increases with decrease in temperature for all the compositions, while it peaks at x = 0.01-0.02 at all temperatures. The combination of Er content—x ˜ 0.02 and the temperature—˜5 K provides the maximum HC ˜ 984 kA/m. Er-substituted cobalt-ferrites have higher cubic anisotropy constant, K1, compared to pure cobalt-ferrite at ambient/sub-ambient temperatures. K1 gradually increases for all compositions in the temperature decreasing from 300 to 100 K. While K1 peaks at ˜150 K for pure cobalt-ferrite, it peaks at ˜50 K for CoFe0.99Er0.01O4, CoFe0.98Er0.02O4, and CoFe0.96Er0.04O4. The MS (˜88.7 Am2/kg), at 5 K, for Er substituted cobalt-ferrite is close to the highest values reported for Sm and Gd substituted cobalt-ferrites. The MS (˜83.5 Am2/kg) at 300 K for Er-substituted cobalt-ferrite is the highest among the lanthanide series element substituted cobalt-ferrites. The HC (at 5 K) for Er substituted cobalt-ferrite is close to the highest values observed for La, Ce, Nd, Sm, and Gd substituted

  10. PLUTONIUM-CERIUM-COBALT AND PLUTONIUM-CERIUM-NICKEL ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-08-25

    >New plutonium-base teroary alloys useful as liquid reactor fuels are described. The alloys consist of 10 to 20 atomic percent cobalt with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 88 atomic percent; or, of from 10 to 25 atomic percent nickel (or mixture of nickel and cobalt) with the remainder plutonium and cerium in any desired proportion, with the plutonium not in excess of 86 atomic percent. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are a lower melting point and a wide range of permissible plutonium dilution.

  11. Low energy sputtering of cobalt by cesium ions

    NASA Technical Reports Server (NTRS)

    Handoo, A.; Ray, Pradosh K.

    1989-01-01

    An experimental facility to investigate low energy (less than 500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of 1 times 10(exp -6) Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected on a cobalt foil surrounding the target. Co-57 was used as a tracer to determine the sputtering yield.

  12. Countercation-sensitive electrochromism of cobalt hexacyanoferrate films

    SciTech Connect

    Kulesza, P.J.; Malik, M.A.; Miecznikowski, K.; Wolkiewicz, A.; Zamponi, S.; Berrettoni, M.; Marassi, R.

    1996-01-01

    Cobalt(II) hexacyanoferrate(III,II) a system analogous to prussian blue, is a unique electrochromic material: its color is not only dependent on the oxidation potential, but also on the nature of the countercations sorbed from electrolyte during reduction. The electrodeposition of cobalt hexacyanoferrate thin films, their voltammetric behavior and spectroelectrochemical identity are reported here in potassium and sodium electrolytes. The oxidized film is purple brown in both electrolytes, but following reduction, the system turns olive-brown in 1 M KCl and becomes green in 1 M NaCl.

  13. Hydrogen Evolution Catalyzed by Cobalt Diimine-Dioxime Complexes

    PubMed Central

    Kaeffer, Nicolas; Chavarot-Kerlidou, Murielle; Artero, Vincent

    2015-01-01

    Conspectus Mimicking photosynthesis and producing solar fuels is an appealing way to store the huge amount of renewable energy from the sun in a durable and sustainable way. Hydrogen production through water splitting has been set as a first-ranking target for artificial photosynthesis. Pursuing that goal requires the development of efficient and stable catalytic systems, only based on earth abundant elements, for the reduction of protons from water to molecular hydrogen. Cobalt complexes based on glyoxime ligands, called cobaloximes, emerged ten years ago as a first generation of such catalysts. They are now widely utilized for the construction of photocatalytic systems for hydrogen evolution. In this Account, we describe our contribution to the development of a second generation of catalysts, cobalt diimine-dioxime complexes. While displaying similar catalytic activities as cobaloximes, these catalysts prove more stable against hydrolysis under strongly acidic conditions thanks to the tetradentate nature of the diimine-dioxime ligand. Importantly, H2 evolution proceeds via proton-coupled electron transfer steps involving the oxime bridge as a protonation site, reproducing the mechanism at play in the active sites of hydrogenase enzymes. This feature allows H2 to be evolved at modest overpotentials, i.e. close to the thermodynamic equilibrium over a wide range of acid-base conditions in non-aqueous solutions. Derivatization of the diimine-dioxime ligand at the hydrocarbon chain linking the two imine functions enables the covalent grafting of the complex onto electrode surfaces in a more convenient manner than for the parent bis-bidentate cobaloximes. Accordingly we attached diimine-dioxime cobalt catalysts onto carbon nanotubes and demonstrated the catalytic activity of the resulting molecular-based electrode for hydrogen evolution from aqueous acetate buffer. The stability of immobilized catalysts was found to be orders of magnitude higher than that of catalysts

  14. Structural and magnetic study of dysprosium substituted cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Hemaunt; Srivastava, R. C.; Pal Singh, Jitendra; Negi, P.; Agrawal, H. M.; Das, D.; Hwa Chae, Keun

    2016-03-01

    The present work investigates the magnetic behavior of Dy3+ substituted cobalt ferrite nanoparticles. X-ray diffraction studies reveal presence of cubic spinel phases in these nanoparticles. Raman spectra of these nanoparticles show change in intensity of Raman bands, which reflects cation redistribution in cubic spinel lattice. Saturation magnetization and coercivity decrease with increase of Dy3+concentration in these nanoparticles. Room temperature Mössbauer measurements show the cation redistribution in these nanoparticles and corroborates the results obtained from Raman Spectroscopic measurements. Decrease in magnetization of Dy3+ substituted cobalt ferrite is attributed to the reduction in the magnetic interaction and cation redistribution.

  15. Hydrogen evolution catalyzed by cobalt diimine-dioxime complexes.

    PubMed

    Kaeffer, Nicolas; Chavarot-Kerlidou, Murielle; Artero, Vincent

    2015-05-19

    Mimicking photosynthesis and producing solar fuels is an appealing way to store the huge amount of renewable energy from the sun in a durable and sustainable way. Hydrogen production through water splitting has been set as a first-ranking target for artificial photosynthesis. Pursuing that goal requires the development of efficient and stable catalytic systems, only based on earth abundant elements, for the reduction of protons from water to molecular hydrogen. Cobalt complexes based on glyoxime ligands, called cobaloximes, emerged 10 years ago as a first generation of such catalysts. They are now widely utilized for the construction of photocatalytic systems for hydrogen evolution. In this Account, we describe our contribution to the development of a second generation of catalysts, cobalt diimine-dioxime complexes. While displaying similar catalytic activities as cobaloximes, these catalysts prove more stable against hydrolysis under strongly acidic conditions thanks to the tetradentate nature of the diimine-dioxime ligand. Importantly, H2 evolution proceeds via proton-coupled electron transfer steps involving the oxime bridge as a protonation site, reproducing the mechanism at play in the active sites of hydrogenase enzymes. This feature allows H2 to be evolved at modest overpotentials, that is, close to the thermodynamic equilibrium over a wide range of acid-base conditions in nonaqueous solutions. Derivatization of the diimine-dioxime ligand at the hydrocarbon chain linking the two imine functions enables the covalent grafting of the complex onto electrode surfaces in a more convenient manner than for the parent bis-bidentate cobaloximes. Accordingly, we attached diimine-dioxime cobalt catalysts onto carbon nanotubes and demonstrated the catalytic activity of the resulting molecular-based electrode for hydrogen evolution from aqueous acetate buffer. The stability of immobilized catalysts was found to be orders of magnitude higher than that of catalysts in the

  16. The role of cobalt ferrite magnetic nanoparticles in medical science.

    PubMed

    Amiri, S; Shokrollahi, H

    2013-01-01

    The nanotechnology industry is rapidly growing and promises that the substantial changes that will have significant economic and scientific impacts be applicable to a wide range of areas, such as aerospace engineering, nano-electronics, environmental remediation and medical healthcare. In this area, cobalt ferrite nanoparticles have been regarded as one of the competitive candidates because of their suitable physical, chemical and magnetic properties like the high anisotropy constant, high coercivity and high Curie temperature, moderate saturation magnetization and ease of synthesis. This paper introduces the magnetic properties, synthesis methods and some medical applications, including the hyperthermia, magnetic resonance imaging (MRI), magnetic separation and drug delivery of cobalt ferrite nanoparticles. PMID:25428034

  17. Cobalt-Catalyzed N-Alkylation of Amines with Alcohols.

    PubMed

    Zhang, Guoqi; Yin, Zhiwei; Zheng, Shengping

    2016-01-15

    A well-defined nonprecious metal cobalt(II) catalyst based on a pincer PNP ligand has been employed for the efficient N-alkylation of both aromatic and aliphatic amines with alcohols. A subtle change of reaction conditions (simply adding 4 Å molecular sieves) was observed to readily switch the resulting products (amines vs imines) with high chemoselectivity. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted to secondary amines in good-to-excellent yields when 2 mol % cobalt catalyst was used. Additional experiments indicate that a hydrogen-borrowing mechanism is responsible for the tandem acceptorless dehydrogenation/condensation/hydrogenation process. PMID:26695594

  18. Copper and cobalt in aquatic mosses and stream sediments from the Idaho Cobalt Belt

    USGS Publications Warehouse

    Erdman, J.A.; Modreski, P.J.

    1984-01-01

    Samples of stream sediments and aquatic mosses were collected from nine sites across several mineralized zones at the southeasternmost extension of the Idaho Cobalt Belt. Because the steepness of the terrain and the attendant high flow rate of the streams made it difficult to obtain adequate sediment samples, mosses were considered as an alternative sampling medium. The results not only showed that the Cu and Co content of the mosses correlated almost perfectly with that of the sediments, but that the contrast between samples taken from mineralized and background areas was greater in mosses, especially for Co. Maximum concentrations of 35,000 ??g/g Cu and 2000 ??g/g Co were observed in the ash of mosses, compared to maximum concentrations of 1700 ??g/g and 320 ??g/g, respectively, in the associated sediments. Species identification was considered unimportant, which should dispel some reluctance to use mosses in mineral exploration. ?? 1984.

  19. Development of a stable cobalt-ruthenium Fischer-Tropsch catalyst. Technical progress report No. 10, January 1, 1992--March 31, 1992

    SciTech Connect

    Frame, R.R.; Gala, H.B.

    1992-12-31

    In this report, and the three before it, progress has been reviewed toward finding a support for cobalt/ruthenium-based Fischer-Tropsch catalysts. Of the support materials investigated three have so far shown promise: magnesium oxide, carbon and 50/50 alumina/titania. However, as yet catalysts supported on these three materials have proven inferior to the reference TC 211 Y zeolite-supported catalyst with regard to both activity and selectivity. Ruthenium is considered to be a promoter of activity, however, if this effect is manifested in the experimental catalysts it is not enough to make the catalysts more active than the ruthenium-free reference catalyst. The advantages due to reverse micelle are, so far, minimal at best. When the experimental catalysts were operated at higher conversions through evaluation at Conditions 2 and 3, the magnesium oxide-supported catalysts appeared to be closest to the desired low methane selectivity of the reference catalyst at similar conversion. The catalysts prepared on the above supports were not superior to the reference catalyst TC 211. Since the main objective of the current contract is to determine whether cobalt/ruthenium catalysts can be prepared which are superior to cobalt only catalysts, the Y zeolite support will be used in the future. In this special Y zeolite-derived support crystallite size is controlled by the pore size distribution. Thus, the catalyst development objective of controlling the crystallite size will be achieved. In the following quarters, work carried out on the cobalt and cobalt/ruthenium catalysts supported on the Y zeolite-derived support will be reported.

  20. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-04-29

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  1. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2003-05-13

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  2. Fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing

    DOEpatents

    Bates, John B.

    2002-01-01

    Systems and methods are described for fabrication of highly textured lithium cobalt oxide films by rapid thermal annealing. A method of forming a lithium cobalt oxide film includes depositing a film of lithium cobalt oxide on a substrate; rapidly heating the film of lithium cobalt oxide to a target temperature; and maintaining the film of lithium cobalt oxide at the target temperature for a target annealing time of at most, approximately 60 minutes. The systems and methods provide advantages because they require less time to implement and are, therefore less costly than previous techniques.

  3. Cobalt Fischer-Tropsch catalysts having improved selectivity

    DOEpatents

    Miller, James G.; Rabo, Jule A.

    1989-01-01

    The promoter(s) Mn oxide or Mn oxide and Zr oxide are added to a cobalt Fischer-Tropsch catalyst combined with the molecular sieve TC-103 or TC-123 such that the resultant catalyst demonstrates improved product selectivity, stability and catalyst life. The improved selectivity is evidenced by lower methane production, higher C5+ yield and increased olefin production.

  4. Cobalt Fischer-Tropsch catalysts having improved selectivity

    DOEpatents

    Miller, James G.; Rabo, Jule A.

    1989-01-01

    A cobalt Fischer-Tropsch catalyst having an improved steam treated, acid extracted LZ-210 support is taught. The new catalyst system demonstrates improved product selectivity at Fischer-Tropsch reaction conditions evidenced by lower methane production, higher C.sub.5.sup.+ yield and increased olefin production.

  5. Energy levels scheme simulation of divalent cobalt doped bismuth germanate

    SciTech Connect

    Andreici, Emiliana-Laura; Petkova, Petya; Avram, Nicolae M.

    2015-12-07

    The aim of this paper is to simulate the energy levels scheme for Bismuth Germanate (BGO) doped with divalent cobalt, in order to give a reliable explanation for spectral experimental data. In the semiempirical crystal field theory we first modeled the Crystal Field Parameters (CFPs) of BGO:Cr{sup 2+} system, in the frame of Exchange Charge Model (ECM), with actually site symmetry of the impurity ions after doping. The values of CFPs depend on the geometry of doped host matrix and by parameter G of ECM. First, we optimized the geometry of undoped BGO host matrix and afterwards, that of doped BGO with divalent cobalt. The charges effect of ligands and covalence bonding between cobalt cations and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the CFPs we simulate the energy levels scheme of cobalt ions, by diagonalizing the matrix of the doped crystal Hamiltonian. Obviously, energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison of obtained results with experimental data shows quite satisfactory, which justify the model and simulation schemes used for the title system.

  6. Tracking the metal of the goblins: cobalt's cycle of use.

    PubMed

    Harper, E M; Kavlak, G; Graedel, T E

    2012-01-17

    Cobalt is a vital element in many technological applications, which, together with its increasing end-use in batteries, makes it important to quantify its cycle of use. We have done so for the planet as a whole and for the three principal cobalt-using countries - China, Japan, and the United States - for 2005. Together, China, Japan, and the United States accounted for approximately 65% of the cobalt fabricated and manufactured into end-use products (a total of 37 Gg Co). A time residence model allowed calculations of in-use stock accumulation and recycled and landfilled flows. China had the largest accumulation of in-use stock at some 4.3 Gg Co, over half of which was comprised of consumer battery stock. More than half of the stock accumulation in the United States was estimated to be in aircraft, rocket, and gas turbine engines, with a total in-use stock accumulation of approximately 3 Gg Co. The largest amounts of cobalt landfilled in China, the United States, and the planet were from the "chemical and other uses" category, and Japan's largest landfilled flow was in consumer batteries. PMID:22142288

  7. Effects of cobalt in nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Tien, J. K.; Jarrett, R. N.

    1982-01-01

    A study has been carried out to assess the role of cobalt in Udimet 700, a representative nickel-base superalloy containing 17 percent or more cobalt. The study spans the spectrum of microstructural, microchemical, and mechanical behavior aspects which together form a basis for superalloy performance in jet engines. The results suggest that cobalt affects the solubility of elements in the gamma matrix, which leads to enhanced gamma-prime volume fraction and to the stabilization of MC-type carbides and sigma phase. However, these microstructural and microchemical changes are too slight to significantly affect the strength and ductile properties. Depending on the heat treatment, the creep and stress rupture resistance can be cobalt-sensitive. In the coarse-grained, fully solutioned and aged condition, all of the alloy's 17 percent Co can be replaced by nickel without decreasing the creep and stress rupture resistance. These findings are discussed with reference to existing theories and experimental data obtained by other workers.

  8. Co-Cu-Si (Cobalt-Copper-Silicon)

    NASA Astrophysics Data System (ADS)

    Materials Science International Team MSIT

    This document is part of Subvolume C2 'Non-Ferrous Metal Systems. Part 2: Selected Copper Systems' of Volume 11 'Ternary Alloy Systems - Phase Diagrams, Crystallographic and Thermodynamic Data critically evaluated by MSIT®' of Landolt-Börnstein - Group IV 'Physical Chemistry'. It provides data of the ternary system Cobalt-Copper-Silicon.

  9. Reaction of ethanol on oxidized and metallic cobalt surfaces

    NASA Astrophysics Data System (ADS)

    Hyman, Matthew P.; Vohs, John M.

    2011-02-01

    The reaction of ethanol on metallic and oxidized cobalt surfaces was studied using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) in order to determine the dependence of the reaction pathways on the cobalt oxidation state. The primary reaction for ethoxide species on metallic cobalt surfaces was decarbonylation producing CO, H 2 and carbon. This reaction was facile and occurred below 400 K. In contrast, CoO x surfaces which predominantly contained Co 2+ were selective for the dehydrogenation of ethoxide groups to produce acetaldehyde at 400 K. A fraction of the acetaldehyde molecules produced by this pathway were further oxidized to acetate which decomposed to produce CO 2 at 495 K. More highly oxidized Co surfaces that contained both CO 2+ and Co 3+ were active for the complete oxidation of ethanol producing CO, CO 2, and H 2O as the primary products. The insights that these results provide for understanding the mechanism of the steam reforming of ethanol on cobalt catalysts is discussed.

  10. A Mercurial Route to a Cobalt Dihydrogen Complex

    SciTech Connect

    Bullock, R. Morris

    2011-03-30

    Recent results by Heinekey and co-workers provide evidence for an unusual route to a cobalt dihydrogen complex. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  11. Study of DNA interaction with cobalt ferrite nanoparticles.

    PubMed

    Pershina, A G; Sazonov, A E; Novikov, D V; Knyazev, A S; Izaak, T I; Itin, V I; Naiden, E P; Magaeva, A A; Terechova, O G

    2011-03-01

    Interaction of cobalt ferrite nanopowder and nucleic acid was investigated. Superparamagnetic cobalt ferrite nanoparticles (6-12 nm) were prepared by mechanochemical synthesis. Structure of the nanopowder was characterized using X-ray diffraction. It was shown that cobalt ferrite nanoparticles were associated with ssDNA and dsDNA in Tris-buffer resulting in bionanocomposite formation with mass weight relation nanoparticles: DNA 1:(0.083 +/- 0.003) and 1:(0.075 +/- 0.003) respectively. The mechanism of interaction between a DNA and cobalt ferrite nanoparticles was considered basing on the whole set of obtained data: FTIR-spectroscopy, analyzing desorption of DNA from the surface of the particles while changing the chemical content of the medium, and on the modeling interaction of specific biomolecule fragments with surface of a inorganic material. It was supposed that the linkage was based on coordination interaction of the phosphate groups and oxygen atoms heterocyclic bases of DNA with metal ions on the particle surface. These data can be used to design specific magnetic DNA-nanoparticles hybrid structures. PMID:21449452

  12. Effect of rare earth substitution in cobalt ferrite bulk materials

    NASA Astrophysics Data System (ADS)

    Bulai, G.; Diamandescu, L.; Dumitru, I.; Gurlui, S.; Feder, M.; Caltun, O. F.

    2015-09-01

    The study was focused on the influence of small amounts of rare earth (RE=La, Ce, Sm, Gd, Dy, Ho, Er, Yb) addition on the microstructure, phase content and magnetic properties of cobalt ferrite bulk materials. The X-Ray diffraction measurements confirmed the formation of the spinel structure but also the presence of secondary phases of RE oxides or orthoferrite in small percentages (up to 3%). Density measurements obtained by Archimedes method revealed a ~1 g cm-3 decrease for the RE doped cobalt ferrite samples compared with stoichiometric one. Both the Mössbauer and Fourier Transform Infrared Spectrocopy analysis results confirmed the formation of the spinel phase. The saturation magnetization and coercive field values of the doped samples obtained by Vibrating Sample Magnetometry were close to those of the pure cobalt ferrite. For magnetostrictive property studies the samples were analyzed using the strain gauge method. Higher maximum magnetostriction coefficients were found for the Ho, Ce, Sm and Yb doped cobalt ferrite bulk materials as related to the stoichiometric CoFe2O4 sample. Moreover, improved strain derivative was observed for these samples but at higher magnetic fields due to the low increase of the coercive field values for doped samples.

  13. Technology development for cobalt F-T catalysts

    SciTech Connect

    Not Available

    1993-03-04

    A computer search of both the open and the patent literature was conducted in order to ascertain the current state of cobalt-based catalyst technology for F-T synthesis. Two series of literature searches were conducted, one dealing specifically with cobalt catalysts for F-T synthesis and the other focusing on the preparation and/or characterization of supported cobalt catalysts including those not used for F-T synthesis. An initial screening of the literature was carried out by examining the 942 abstracts obtained from these searches. The main objective of this initial screening was the selection of the most pertinent publications for this work. out of the 230 patent references obtained from the computer search, about 90 were found to be directly related the preparation of cobalt catalysts and their use in FT synthesis. Copies of patents (78 patents) not available within the group have been ordered but not yet received. Based on a preliminary analysis,of the abstracts of the most pertinent patents a distribution among the various patent assignees is given in Table 1. As can be seen in Table 1, most of the patents for Co FT catalysts have been assigned to very few companies, the first four, i.e. Exxon, Shell, Gulf, and Statoil representing the most relevant ones. This preliminary analysis of the patent literature permitted a selection of a number of benchmark catalysts the formulations of which will be based on the patents of these four companies.

  14. Segregation of Fischer-Tropsch reactants on cobalt nanoparticle surfaces.

    PubMed

    Lewis, E A; Le, D; Jewell, A D; Murphy, C J; Rahman, T S; Sykes, E C H

    2014-06-21

    Using scanning tunnelling microscopy, we have visualized the segregation of carbon monoxide and hydrogen, the two reactants in Fischer-Tropsch synthesis, on cobalt nanoparticles at catalytically relevant coverages. Density functional theory was used to interrogate the relevant energetics. PMID:24825772

  15. Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application.

    PubMed

    Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S; Maiti, Tapas K; Banerjee, Indranil

    2016-01-01

    The present study delineates the synthesis and characterization of cobalt doped proangiogenic-osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co(2+)) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP-OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic-osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. PMID:26478356

  16. Control of Particle Size and Morphology of Cobalt-Ferrite Nanoparticles by Salt-Matrix during Annealing

    NASA Astrophysics Data System (ADS)

    Azizi, A.; Sadrnezhaad, S. K.; Mostafavi, M.

    Salt-matrix annealing of mechanically alloyed Co-ferrite nanopowder was used to modify its particle size and morphology. Efficiency improvement due to suppression of sintering and growth resulted in reduction of average particle size from 100nm for salt-less to 40nm for salt-full annealing procedure. Nanosized single-phase cobalt-ferrite particles were observed after 2h annealing at 750°C in the samples milled for 20 hours both with and without NaCl. NaCl:CoFe2O4 ratio of 10:1 resulted in cabbage-like clusters containing particles smaller than 50 nm.

  17. Arthroprosthetic cobaltism: identification of the at-risk patient.

    PubMed

    Tower, Stephen

    2010-09-01

    MoM hip bearings are being scrutinized due to high early failure rates and concerns that the results of the revision surgeries will be poor. However, orthopedic surgeons and the general medical community are unaware that patients with MoM bearings are also at risk for cobaltism. Medical providers need to know that hip arthroplasty implantees that present with symptom complexes that include tinnitus, deafness, vertigo, visual changes, rashes, hypothyroidism, tremor, dyspnea on exertion, mood disorders, dementia, heart failure, and peripheral neuropathy may be presenting arthroprosthetic cobaltism. These patients need to be asked if they have had a hip replacement and if so what type. For those patients implanted with a MoM bearing or those with a history of hip revision for a failed ceramic bearing obtaining a [Co] is indicated. MoM implantees with renal failure are a particularly high risk for cobaltism. A [Co] can be measured by many reference laboratories from royal blue top trace elements tube of venous blood. Venipuncture with a standard needle is adequate as long as a red stoppered tube is drawn first. The radiographic appearance of a MoM bearing is readily apparent to an orthopedic surgeon. The patient's operative report will usually specify the bearing type. Given that the publicity of the recent ASR bearing recall medical providers will be contacted by worried patients concerned about their hip implants. Most patients with hip replacements will not know the brand or material of their bearings. Providing patients with copies of their hip implant inventory might avoid worry by the majority of patients with hip arthroplasties that are not at risk. Patients with a cobalt levels of greater than 7 mcg/l bear observation of neurologic and cardiac function. Those patients with levels greater than 20 should be advised to have revision of their hip arthroplasty to a bearing that eliminates cobalt. Most patients implanted with MoM bearing have cobalt levels greater

  18. 50 CFR 253.50 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 11 2013-10-01 2013-10-01 false Definitions. 253.50 Section 253.50 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE AID TO FISHERIES FISHERIES ASSISTANCE PROGRAMS Interjurisdictional Fisheries §...

  19. 50 CFR 253.50 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false Definitions. 253.50 Section 253.50 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE AID TO FISHERIES FISHERIES ASSISTANCE PROGRAMS Interjurisdictional Fisheries §...

  20. Cobalt-Boride: An efficient and robust electrocatalyst for Hydrogen Evolution Reaction

    NASA Astrophysics Data System (ADS)

    Gupta, Suraj; Patel, Nainesh; Miotello, Antonio; Kothari, D. C.

    2015-04-01

    This work presents Cobalt-Boride (Co-B) as a non-noble, efficient and robust electrocatalyst for Hydrogen Evolution Reaction (HER) active in aqueous solution of wide pH values. In neutral solution, amorphous Co-B nanoparticles (30-50 nm size) generate high current density (10 mA/cm2) at low overpotential (250 mV) with Tafel slope of 75 mV/dec following Volmer-Heyrovsky reaction mechanism. Highly active Co surface sites created by electronic transfer from B to Co (as inferred from XPS analysis and supported by theoretical calculations) are responsible for this significant HER activity in wide range of pH (4-9) values. Stability and reusability tests also demonstrate the robust nature of the catalyst.

  1. Conducting dimerized cobalt complexes with tetrathiafulvalene dithiolate ligands.

    PubMed

    Fujiwara, Emiko; Hosoya, Kazumasa; Kobayashi, Akiko; Tanaka, Hisashi; Tokumoto, Madoka; Okano, Yoshinori; Fujiwara, Hideki; Kobayashi, Hayao; Fujishiro, Yuichi; Nishibori, Eiji; Takata, Masaki; Sakata, Makoto

    2008-02-01

    To obtain novel single-component molecular metals, we attempted to synthesize several cobalt complexes coordinated by TTF (tetrathiafulvalene)-type dithiolate ligands. We succeeded in the syntheses and structure determinations of ((n)Bu(4)N)(2)[Co(chdt)(2)](2) (1), ((n)Bu(4)N)(2)[Co(dmdt)(2)](2) (2), [Co(dmdt)(2)](2) (3), and [Co(dt)(2)](2) (4) (chdt = cyclohexeno-TTF-dithiolate, dmdt = dimethyl-TTF-dithiolate, and dt = TTF-dithiolate). Structure analyses of complexes 1-4 revealed that two monomeric [Co(ligand)2]- or [Co(ligand)(2)](0) units are connected by two Co-S bonds resulting in dimeric [Co(ligand)(2)](2)(2-) or [Co(ligand)(2)](2) molecules. Complex 1 has a cation-anion-intermingled structure and exhibited Curie-Weiss magnetic behavior with a large Curie constant (C = 2.02 K x emu x mol(-1)) and weak antiferromagnetic interactions (theta = -8.3 K). Complex 2 also has a cation-anion-intermingled structure. However, the dimeric molecules are completely isolated by cations. Complexes 3 and 4 are single-component molecular crystals. The molecules of complex 3 form two-dimensional molecular stacking layers and exhibit a room-temperature conductivity of sigmart = 1.2 x 10(-2) S.cm(-1) and an activation energy of E(a) = 85 meV. The magnetic behavior is almost consistent with Curie-Weiss law, where the Curie constant and Weiss temperature are 8.7 x 10(-2) K x emu x mol(-1) and -0.85 K, respectively. Complex 4 has a rare chair form of the dimeric structure. The electrical conductivity was fairly large (sigmart = 19 S.cm(-1)), and its temperature dependence was very small (sigma(0.55K)/sigma(rt) = ca. 1:10), although the measurements were performed on the compressed pellet sample. Complex 4 showed an almost constant paramagnetic susceptibility (chi(300) (K) = 3.5 x 10(-4) emu x mol(-1)) from 300 to 50 K. The band structure calculation of complex 4 suggested the metallic nature of the system. Complex 4 is a novel single-component molecular conductor with a dimeric

  2. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    SciTech Connect

    Barry, Aliou Hamady; Dirras, Guy; Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  3. Magnetic and microwave absorption properties of self-assemblies composed of core-shell cobalt-cobalt oxide nanocrystals.

    PubMed

    Wang, Zhongzhu; Bi, Hong; Wang, Peihong; Wang, Min; Liu, Zhiwei; Shen, Lei; Liu, Xiansong

    2015-02-01

    Core-shell structure cobalt-cobalt oxide nanocomposites were directly synthesized via annealing Co nanocrystals in air at 300 °C. Their microstructure and magnetic properties were characterized by XRD, TEM, XPS and VSM, respectively. The microwave absorbing properties of the nanocomposite powders by dispersing them in wax were investigated in the 2-18 GHz frequency range. The sample that was annealed for 1 h exhibits the maximum reflection loss of -30.5 dB and a bandwidth of less than -10 dB covering the 12.6-17.3 GHz range with the coating thickness of only 1.7 mm. At the same thickness, the sample annealed for 3 h exhibits the maximum reflection loss of -24 dB and a bandwidth that almost covers the whole X-band (8-11.5 GHz). With increase in the insulating cobalt oxide shell, the enhanced permeability could contribute to the decrease of eddy current loss, and the permittivity could be easily adjusted; thus, the microwave absorption properties of the cobalt oxide nanocrystals could be easily adjusted. PMID:25559407

  4. Separation of cobalt from synthetic intermediate and decontamination radioactive wastes using polyurethane foam

    SciTech Connect

    Rao, S.V.S.; Lal, K.B.; Narasimhan, S.V.; Ahmed, J.

    1997-12-01

    Studies have been carried out on the removal of radioactive cobalt ({sup 60}Co) from synthetic intermediate level waste (ILW) and decontamination waste using neat polyurethane (PU) foam as well as n-tributyl phosphate-polyurethane (TBP-PU) foam. The radioactive cobalt has been extracted on the PU foam as cobalt thiocyanate from the ILW. Maximum removal of cobalt has been observed when the concentration of thiocyanate in the solution is about 0.4 M. Cobalt can be separated from decontamination waste containing ethylenediaminetetraacetic acid (EDTA) and iron(II). The extent of extraction of cobalt is slow and the separation of iron and cobalt is better with the neat PU foam compared to the TBP-PU foam. The presence of iron in the decontamination waste facilitates the extraction of cobalt thiocyanate on the PU foam. Column studies have been carried out in order to extend these studies to the plant scale. The capacities of the PU foams for cobalt have been determined. The effect of density and the surface area of PU foam have been investigated. Fourier Transform Infrared (FT-IR) spectral studies have been conducted to find out the interaction between PU foam and cobalt thiocyanate species.

  5. Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo

    NASA Astrophysics Data System (ADS)

    Decrée, Sophie; Deloule, Étienne; Ruffet, Gilles; Dewaele, Stijn; Mees, Florias; Marignac, Christian; Yans, Johan; de Putter, Thierry

    2010-10-01

    The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves. They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks. Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs. The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class “manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar-Ar analyses of oxidized Mn ore and in situ U-Pb SIMS measurements of heterogenite yield Mio-Pliocene ages. The Ar-Ar ages suggest a multi-phase process, starting in the Late Miocene (10-5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional uplift. Further oxidation took place in the Pliocene (3.7-2.3 Ma) and formed most of the observed deposits under humid conditions: Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot slopes.

  6. Shape and Size of Cobalt Nanoislands Formed Spontaneously on Cobalt Terraces during Fischer-Tropsch Synthesis.

    PubMed

    Banerjee, Arghya; Navarro, Violeta; Frenken, Joost W M; van Bavel, Alexander P; Kuipers, Herman P C E; Saeys, Mark

    2016-06-01

    Cobalt-based catalysts undergo a massive and spontaneous reconstruction to form uniform triangular nanoislands under Fischer-Tropsch (FT) conditions. This reconstruction is driven by the unusual and synergistic adsorption of square-planar carbon and CO at the 4-fold edge sites of the nanoislands, driving the formation of triangular islands. The size of the nanoislands is determined by the balance between energy gain from creating C/CO-covered edges and energy penalty to create C/CO-covered corners. For carbon chemical potentials corresponding to FT conditions, triangular Co islands with 45 Co atoms (about 2 nm) are the most stable surface structure. Decreasing the carbon chemical potential and hence the stability of square-planar carbon favors the formation of larger islands, until reconstruction becomes unfavorable and CO-covered terraces are thermodynamically the most stable. The predicted structure of the islands is consistent with in situ scanning tunneling microscopy images obtained for the first time under realistic FT reaction conditions on a Co(0001) surface. PMID:27176712

  7. Crystallization behaviour of hydroxide cobalt carbonates by aging: Environmental implications.

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Fernández-González, Angeles; Jimenez, Amalia

    2014-05-01

    Cobalt is a naturally occurring element widely distributed in water, sediments and air that is essential for living species, since it is a component of B12 vitamin and it is also a strategic and critical element used in a number of commercial, industrial and military applications. However, relatively high accumulations of cobalt in environment can be toxic for human and animal health. Cobalt usually occurs as Co2+ and Co3+ in aqueous solutions, where Co2+ is the most soluble and hence its mobility in water is higher. The study of the precipitation of cobalt carbonates is of great interest due to the abundance of carbonate minerals in contact with surface water and groundwater which can be polluted with Co2+. Previous works have demonstrated that the formation of Co-bearing calcium carbonates and Co-rich low crystallinity phases takes place at ambient conditions. With the aim of investigating the crystallization behavior of Co- bearing carbonates at ambient temperature, macroscopic batch-type experiments have been carried out by mixing aqueous solutions of CoCl2 (0.05M) and Na2CO3 (0.05M) during increasing reaction times (5 minutes and 1, 5, 24, 48, 96, 168, 720 and 1440 hours). The main goals of this work were (i) to analyse the physicochemical evolution of the system and (ii) to study the evolution of the crystallinity of the solid phases during aging. After a given reaction period, pH, alkalinity and dissolved Co2+ in the aqueous solutions were analysed. The evolution of the morphology and chemical composition of the solids with aging time was examined by SEM and TEM. The precipitates were also analyzed by X-ray powder diffraction (XRD) and the crystallinity degree was followed by the intensity and the full width at high medium (FWHM) of the main peaks. The results show that a low crystallinity phase was obtained at the very beginning of aging. This phase evolves progressively to form hydroxide carbonate cobalt (Co2CO3(OH)2) which crystallize with the spatial

  8. A preliminary evaluation of stream sediment sampling for the detection of cobalt mineralization in the Bou Azzer District, Morocco

    USGS Publications Warehouse

    Foose, M.P.

    1983-01-01

    Analyses of 28 stream sediment samples collected in the Bou Azzer district, Morocco, show that this sampling technique may be useful in locating the cobalt arsenide mineralization that exists in this area. The absence of exceptionally high values of cobalt and arsenic, the nearly lognormal distribution of cobalt values, and the lack of correlation between the highest values of cobalt and arsenic were unanticipated results that do not support the use of this sampling technique. However, highest values of several metals, including cobalt, were associated with an identified area of cobalt mineralization, and high cobalt was present near a second area in which cobalt mineralization is suspected. Although probably mostly reflecting the geochemistry of unexposed ultramafic rocks, the association of these metals with mineralization shows that this type of sampling can independently locate areas of known or potential cobalt mineralization.

  9. Pairwise cobalt doping of boron carbides with cobaltocene

    NASA Astrophysics Data System (ADS)

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A.

    2007-10-01

    We have performed Co K-edge x-ray absorption fine structure and x-ray absorption near edge structure measurements of Co-doped plasma enhanced chemical vapor phase deposition (PECVD) grown "C2B10Hx" semiconducting boron carbides, using cobaltocene. Cobalt does not dope PECVD grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated (R=2.10±0.02Å) and are chemically bonded to the icosahedral cages of B10CHx or B9C2Hy. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28±0.02Å apart.

  10. Iron, lead, and cobalt absorption: similarities and dissimilarities

    SciTech Connect

    Barton, J.C.; Conrad, M.E.; Holland, R.

    1981-01-01

    Using isolated intestinal segments in rats, the absorption of iron, lead, and cobalt was increased in iron deficiency and decreased in iron loading. Similarly, the absorption of these metals was decreased in transfusional erythocytosis, after intravenous iron injection and after parenteral endotoxin injection. Acute bleeding or abbreviated intervals of dietary iron deprivation resulted in increased iron absorption from isolated intestinal segments and in intact animals, while the absorption of lead and cobalt was unaffected. These results suggest that the specificity of the mucosal metal absorptive mechanism is either selectively enhanced for iron absorption by phlebotomy or brief periods of dietary iron deprivation, or that two or more mucosal pathways for iron absorption may exist.

  11. Radiation dose distributions due to sudden ejection of cobalt device.

    PubMed

    Abdelhady, Amr

    2016-09-01

    The evaluation of the radiation dose during accident in a nuclear reactor is of great concern from the viewpoint of safety. One of important accident must be analyzed and may be occurred in open pool type reactor is the rejection of cobalt device. The study is evaluating the dose rate levels resulting from upset withdrawal of co device especially the radiation dose received by the operator in the control room. Study of indirect radiation exposure to the environment due to skyshine effect is also taken into consideration in order to evaluate the radiation dose levels around the reactor during the ejection trip. Microshield, SHLDUTIL, and MCSky codes were used in this study to calculate the radiation dose profiles during cobalt device ejection trip inside and outside the reactor building. PMID:27423021

  12. Cobalt Hexacyanoferrate as Cathode Material for Na+ Secondary Battery

    NASA Astrophysics Data System (ADS)

    Takachi, Masamitsu; Matsuda, Tomoyuki; Moritomo, Yutaka

    2013-02-01

    We investigated structural and electrochemical properties of thin film electrodes of cobalt hexacyanoferrate, NaxCo[Fe(CN)6]0.902.9H2O, against x. The compound exhibits a high capacity of 135 mAh/g and an average operating voltage of 3.6 V against Na, with a good cyclability. The discharge curve exhibits two plateaus at ≈3.8 and ≈3.4 V, which are ascribed to the reduction processes of Fe3+ and Co3+, respectively. The ex situ X-ray diffraction (XRD) profiles reveal the robust nature of the host framework against Na+ intercalation/deintercalation. Thus, cobalt hexacyanoferrate is a promising candidate for the cathode material of sodium-ion secondary battery (SIB).

  13. Accurate determination of cobalt traces in several biological reference materials.

    PubMed

    Dybczyński, R; Danko, B

    1994-01-01

    A newly devised, very accurate ("definitive") method for the determination of trace amounts of cobalt in biological materials was validated by the analysis of several certified reference materials. The method is based on a combination of neutron activation and selective and quantitative postirradiation isolation of radiocobalt from practically all other radionuclides by ion-exchange and extraction chromatography followed by gamma-ray spectrometric measurement. The significance of criteria that should be fulfilled in order to accept a given result as obtained by the "definitive method" is emphasized. In view of the demonstrated very good accuracy of the method, it is suggested that our values for cobalt content in those reference materials in which it was originally not certified (SRM 1570 spinach, SRM 1571 orchard leaves, SRM 1577 bovine liver, and Czechoslovak bovine liver 12-02-01) might be used as provisional certified values. PMID:7710879

  14. Pairwise cobalt doping of boron carbides with cobaltocene

    SciTech Connect

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A.

    2007-10-15

    We have performed Co K-edge x-ray absorption fine structure and x-ray absorption near edge structure measurements of Co-doped plasma enhanced chemical vapor phase deposition (PECVD) grown 'C{sub 2}B{sub 10}H{sub x}' semiconducting boron carbides, using cobaltocene. Cobalt does not dope PECVD grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated (R=2.10{+-}0.02 A) and are chemically bonded to the icosahedral cages of B{sub 10}CH{sub x} or B{sub 9}C{sub 2}H{sub y}. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28{+-}0.02 A apart.

  15. Hierarchical cobalt-based hydroxide microspheres for water oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Ye; Cui, Bai; Derr, Olivia; Yao, Zhibo; Qin, Zhaotong; Deng, Xiangyun; Li, Jianbao; Lin, Hong

    2014-02-01

    3D hierarchical cobalt hydroxide carbonate hydrate (Co(CO3)0.5(OH).0.11H2O) has been synthesized featuring a hollow urchin-like structure by a one-step hydrothermal method at modest temperature on FTO glass substrates. The functionalities of precursor surfactants were isolated and analyzed. A plausible formation mechanism of the spherical urchin-like microclusters has been furnished through time-dependent investigations. Introduction of other transitional metal doping (Cu, Ni) would give rise to a substantial morphological change associated with a surface area drop. The directly grown cobalt-based hydroxide composite electrodes were found to be capable of catalyzing oxygen evolution reaction (OER) under both neutral pH and alkaline conditions. The favorable 3D dendritic morphology and porous structure provide large surface areas and possible defect sites that are likely responsible for their robust electrochemical activity.

  16. Electrocatalytic hydrogen evolution in acidic water with molecular cobalt tetraazamacrocycles.

    PubMed

    McCrory, Charles C L; Uyeda, Christopher; Peters, Jonas C

    2012-02-15

    A series of water-soluble molecular cobalt complexes of tetraazamacrocyclic ligands are reported for the electrocatalytic production of H(2) from pH 2.2 aqueous solutions. The comparative data reported for this family of complexes shed light on their relative efficiencies for hydrogen evolution in water. Rotating disk electrode voltammetry data are presented for each of the complexes discussed, as are data concerning their respective pH-dependent electrocatalytic activity. In particular, two diimine-dioxime complexes were identified as exhibiting catalytic onset at comparatively low overpotentials relative to other reported homogeneous cobalt and nickel electrocatalysts in aqueous solution. These complexes are stable at pH 2.2 and produce hydrogen with high Faradaic efficiency in bulk electrolysis experiments over time intervals ranging from 2 to 24 h. PMID:22280515

  17. Electrodeposition of cobalt-chromium alloy from trivalent chromium solutions

    SciTech Connect

    Dasarathy, H.; Riley, C.; Coble, H.D. . Dept. of Chemistry and Materials Science)

    1994-07-01

    Cobalt-chromium alloy was deposited from plating solutions containing cobalt(II) chloride and chromium(III) chloride at 3.5 pH. The deposits were obtained using both single and mixed complex solutions. Deposit morphology showed significant dependence on the complexing agent(s) used. Partitioning of the two components in the deposit as determined by energy dispersive spectroscopy depended on plating parameters such as concentration ratio of the two salts in the solution, complexing agent, type of current (both dc and pulsed current were studied), and current density. X-ray photoelectron spectroscopy spectra collected from as-deposited alloy revealed the presence of both oxides and metals. X-ray diffraction spectra for the alloy deposit indicated solid solution formation.

  18. Thin films of tetrafluorosubstituted cobalt phthalocyanine: Structure and sensor properties

    NASA Astrophysics Data System (ADS)

    Klyamer, Darya D.; Sukhikh, Aleksandr S.; Krasnov, Pavel O.; Gromilov, Sergey A.; Morozova, Natalya B.; Basova, Tamara V.

    2016-05-01

    In this work, thin films of tetrafluorosubstituted cobalt phthalocyanine (CoPcF4) were prepared by organic molecular beam deposition and their structure was studied using UV-vis, polarization dependent Raman spectroscopy, XRD and atomic force microscopy. Quantum chemical calculations (DFT) have been employed in order to determine the detailed assignment of the bands in the CoPcF4 IR and Raman spectra. The electrical sensor response of CoPcF4 films to ammonia vapours was investigated and compared with that of unsubstituted cobalt phthalocyanine films. In order to explain the difference in sensitivity of the unsubstituted and fluorinated phthalocyanines to ammonia, the nature and properties of chemical binding between CoPc derivatives and NH3 were described by quantum-chemical calculations utilizing DFT method. The effect of post-deposition annealing on surface morphology and gas sensing properties of CoPcF4 films was also studied.

  19. Monte Carlo simulation of a cobalt-60 beam

    SciTech Connect

    Han, K.; Ballon, D.; Chui, C.; Mohan, R.

    1987-05-01

    We have used the Stanford Electron Gamma Shower (EGS) Monte Carlo code to compute photon spectra from an AECL Theratron 780 cobalt-60 unit. Particular attention has been paid to the careful modeling of the geometry and material construction of the cobalt-60 source capsule, source housing, and collimator assembly. From our simulation, we conclude that the observed increase in output of the machine with increasing field size is caused by scattered photons from the primary definer and the adjustable collimator. We have also used the generated photon spectra as input to a pencil beam model to calculate the tissue--air ratios in water and compared it to a model which uses a monochromatic photon energy of 1.25 MeV.

  20. Effects of cobalt on structure, microchemistry and properties of a wrought nickel-base superalloy

    NASA Technical Reports Server (NTRS)

    Jarrett, R. N.; Tien, J. K.

    1982-01-01

    The effect of cobalt on the basic mechanical properties and microstructure of wrought nickel-base superalloys has been investigated experimentally by systematically replacing cobalt by nickel in Udimet 700 (17 wt% Co) commonly used in gas turbine (jet engine) applications. It is shown that the room temperature tensile yield strength and tensile strength only slightly decrease in fine-grained (disk) alloys and are basically unaffected in coarse-grained (blading) alloys as cobalt is removed. Creep and stress rupture resistances at 760 C are found to be unaffected by cobalt level in the blading alloys and decrease sharply only when the cobalt level is reduced below 8 vol% in the disk alloys. The effect of cobalt is explained in terms of gamma prime strengthening kinetics.

  1. Effect of particle size on CO hydrogenation activity of silica supported cobalt catalysts

    SciTech Connect

    Ho, Suiwen; Houalla, M.; Hercules, D.M. )

    1990-08-09

    Two series of silica supported cobalt catalysts were prepared by incipient wetness impregnation, one by varying the calcination temperature (200-400{degree}C, 3 wt % Co) and the other by changing the cobalt loading (1-10 wt % Co). Examination by ESCA, XRD, and H{sub 2} chemisorption showed that Co{sub 3}O{sub 4} is the dominant phase. The cobalt phase is reduced to cobalt metal at 400{degree}C. The cobalt particle sizes obtained from ESCA correlated well with those derived from H{sub 2} chemisorption and XRD line broadening. The turnover frequency of Co/SiO{sub 2} for CO hydrogenation was invariant with cobalt dispersion in the range of 6-20% dispersion.

  2. Copper catalysis for enhancement of cobalt leaching and acid utilization efficiency in microbial fuel cells.

    PubMed

    Liu, Yaxuan; Shen, Jingya; Huang, Liping; Wu, Dan

    2013-11-15

    Enhancement of both cobalt leaching from LiCoO2 and acid utilization efficiency (AUE) in microbial fuel cells (MFCs) was successfully achieved by the addition of Cu(II). A dosage of 10mg/L Cu(II) improved both cobalt leaching up to 308% and AUE of 171% compared to the controls with no presence of Cu(II). The apparent activation energy of cobalt leaching catalyzed by Cu(II) in MFCs was only 11.8 kJ/mol. These results demonstrate cobalt leaching in MFCs using Cu(II) as a catalyst may be an effective strategy for cobalt recovery and recycle of spent Li-ion batteries, and the evidence of influence factors including solid/liquid ratio, temperature, and pH and solution conductivity can contribute to improving understanding of and optimizing cobalt leaching catalyzed by Cu(II) in MFCs. PMID:24007993

  3. Toxicity, bio-distribution and metabolism of CO-releasing molecules based on cobalt.

    PubMed

    Gong, Yaguo; Zhang, Taofeng; Li, Meng; Xi, Na; Zheng, Yawen; Zhao, Quanyi; Chen, Yonglin; Liu, Bin

    2016-08-01

    CO-releasing molecules (CORMs) containing [Co2(CO)6] moiety show many bioactivities, such as anti-inflammatory and antitumor cell proliferation. However, so far, no one knows their properties in vivo. So, here, we evaluated some these kind CORMs from drug-like properties including cytotoxicity, toxicity in vivo, distribution and metabolism. The results show all the tested complexes displayed antiproliferative activity to HeLa cell and HepG2 cell lines, and their IC50 values were 36-110µM against HeLa cells and 39-140µM against HepG2 cells. Toxicity tests of mice, we used oral acute toxic class method and got their LD50 values; among them, LD50 of complex 1 and complex 4 were in 2500-5000mgkg(-1) and complex 7 over 5000mgkg(-1). The developmental toxicities of the complexes were investigated in embryonic zebrafish. The mortality, hatch rate, malformation, heart rate, spontaneous movement, and larval behavior were examined, and we found both complexes 4 and 7 have not toxicity at low concentration (<1.0μM) but have higher toxicity at high concentration (>5.0μM). After several consecutive i.p administrations, tested complexes severely damaged rat liver and kidney in both functional and morphological aspects. Through metal ion measurement using ICP-AES, we found the tested complexes were unevenly distributed in tissues and organs; complex 4 has a big prone to collect in liver, whereas complex 7 easily enters to kidney. After administration 480min later, most of complex 7 excreted from kidney and entered urine, while complex 4 needed 9h at least. This results show cobalt did not accumulate, and could excrete with the urine. In vivo, Co(0) in complexes was oxidised to Co(II). In addition, the substituents significantly affected the rate of CO-release, cytotoxicity and their bio-distribution. In the view of these aspects, the CORMs based cobalt has a potential property to be a medicine. PMID:27375229

  4. Cobalt-Catalyzed Enantioselective Vinylation of Activated Ketones and Imines.

    PubMed

    Huang, Yuan; Huang, Rui-Zhi; Zhao, Yu

    2016-05-25

    We present here an unprecedented cobalt-catalyzed enantioselective vinylation of α-ketoesters, isatins, and imines to deliver a range of synthetically useful allylic alcohols and amines in high enantiopurity. This method employs commercially available and easy to handle catalysts and reagents and exhibits a high degree of practicality. The efficiency, selectivity, and operational simplicity of this catalytic system coupled with the substrate generality render this method a valuable tool in organic synthesis. PMID:27139596

  5. Protective Agent-Free Synthesis of Colloidal Cobalt Nanoparticles

    SciTech Connect

    Balela, M. D. L.; Lockman, Z.; Azizan, A.; Matsubara, E.; Amorsolo, A. V. Jr.

    2010-03-11

    Spherical colloidal cobalt (Co) nanoparticles of about 2-7 nm were synthesized by hydrazine reduction in ethylene glycol at 80 deg. C. The mean diameter of the Co nanoparticles was varied to some extent by changing the pH, temperature, Co(II) chloride hexahydrate concentration, and amount of hydrazine. The Co particle size was reduced by decreasing Co(II) chloride concentration and increasing amount of hydrazine.

  6. Certain physical properties of cobalt and nickel borides

    NASA Technical Reports Server (NTRS)

    Kostetskiy, I. I.; Lvov, S. N.

    1981-01-01

    The temperature dependence of the electrical resistivity, the thermal conductivity, and the thermal emf of cobalt and nickel borides were studied. In the case of the nickel borides the magnetic susceptibility and the Hall coefficient were determined at room temperature. The results are discussed with allowance for the current carrier concentration, the effect of various mechanisms of current-carrier scattering and the location of the Fermi level in relation to the 3d band.

  7. Towards the elimination of excessive cobalt supplementation in racing horses: A pharmacological review.

    PubMed

    Kinobe, Robert T

    2016-02-01

    Cobalt is an essential trace element for many vital physiological functions. Cobalt is also known to stabilise hypoxia-inducible transcription factors leading to increased expression of erythropoietin which activates production of red blood cells. This implies that cobalt can be used to enhance aerobic performance in racing horses. If this becomes a pervasive practice, the welfare of racing animals would be at risk because cobalt is associated with cardiovascular, haematological, thyroid gland and reproductive toxicity as observed in laboratory animals and humans. It is expected that similar effects may manifest in horses but direct evidence on equine specific effects of cobalt and the corresponding exposure conditions leading to such effects is lacking. Available pharmacokinetic data demonstrates that intravenously administered cobalt has a long elimination half-life (42-156 h) and a large volume of distribution (0.94 L/kg) in a horse implying that repeated administration of cobalt would accumulate in tissues over time attaining equilibrium after ~9-33 days. Based on these pharmacokinetic data and surveys of horses post racing, threshold cobalt concentrations of 2-10 μg/L in plasma and 75-200 μg/L in urine have been recommended. However, there is no clearly defined, presumably normal cobalt supplementation regimen for horses and characterisation of potential adverse effects of any established threshold cobalt concentrations has not been done. This review outlines the strengths and limitations of the existing literature on the pharmacological effects of cobalt in horses with some recommendations on what gaps to bridge to enable the determination of optimal threshold cobalt concentrations in racing horses. PMID:26850547

  8. Physicochemical state of cobalt and chromium in natural waters of the arid zone of the USSR

    SciTech Connect

    Isamatov, E.E.; Kist, A.A.; Kulmatov, R.A.; Volkov, A.A.; Rakhmatov, U.

    1988-01-01

    The authors discuss results of a comprehensive study of the environmental and chemical behavior of trace amounts of cobalt and chromium ions and compounds in waters of the Aral Sea and Amu Darya and Syr Darya rivers in the Soviet Union. The methods used in the determinations include thermodynamic assessments of the ionic composition of the waters and a direct determination of the cobalt and chromium compounds using neutron activation analysis and isotopic and ion exchange analysis for chromium 51 and cobalt 60.

  9. Fabrication of Discrete Nanosized Cobalt Particles Encapsulated Inside Single-Walled Carbon Nanotubes

    SciTech Connect

    Zoican Loebick, C.; Majewska, M; Ren, F; Haller, G; Pfefferle, L

    2010-01-01

    Single-walled carbon nanotubes (SWNT) with encapsulated nanosized cobalt particles have been synthesized by a facile and scalable method. In this approach, SWNT were filled with a cobalt acetylacetonate solution in dichloromethane by ultrasonication. In a second step, exposure to hydrogen at different temperatures released discrete cobalt particles of controllable size inside the SWNT cavity. The SWNT-Co particles systems were characterized by transmission electron microscopy, X-ray absorption spectroscopy, Raman spectroscopy, and thermal gravimetric analysis.

  10. Structure and magnetism in rare earth strontium-doped cobaltates

    NASA Astrophysics Data System (ADS)

    James, Michael; Morales, Liliana; Wallwork, Kia; Avdeev, Maxim; Withers, Ray; Goossens, Darren

    2006-11-01

    Substantial interest has recently been generated by rare earth cobaltate compounds as cathode materials for solid oxide fuel cells. We have synthesised a wide range of single-phase perovskite-based rare earth cobaltates (Ln 1-xSr xCoO 3-δ) (Ln=La 3+-Yb 3+). A combination of electron and X-ray diffraction of these phases reveals a complex family of tetragonal and orthorhombic superstructures. The nature of structural and magnetic ordering relies on both cation and oxygen vacancy distribution. Phase boundaries exists between compounds containing large, medium and small rare earths (between Nd 3+ and Sm 3+, and also between Gd 3+ and Dy 3+) and also at different Sr-doping levels. Powder neutron diffraction has been used in conjunction with the other techniques to reveal cation and oxygen vacancy ordering within these materials. These phases show mixed valence (3+/4+) cobalt oxidation states that increases with Sr content. A range of magnetic behaviours has been observed, including ordered antiferromagnetism at elevated temperatures (>300 K) in Ho 0.2Sr 0.8CoO 2.75.

  11. Cobalt-60 plaque radiotherapy vs enucleation for posterior uveal melanoma

    SciTech Connect

    Augsburger, J.J.; Gamel, J.W.; Lauritzen, K.; Brady, L.W. )

    1990-05-15

    We compared the survival of 302 patients with a primary choroidal or ciliary body melanoma treated by cobalt-60 plaque radiotherapy between 1976 and 1982 with the survival of 134 patients treated by enucleation during the same period. Tumor size, location of the anterior margin of the tumor, and patient age at the time of treatment were identified as simultaneous significant clinical variables for predicting melanoma-specific mortality by multivariate Cox proportional hazards modeling. We computed a prognostic index for each patient based on this model and found that patients in the enucleation group had slightly higher values of this index than did patients in the cobalt-60 plaque radiotherapy group. Risk ratios for the treatment effect computed from a Cox model incorporating prognostic index and the treatment variable were found to be approximately equal to 1, both for analysis of melanoma-specific mortality and total mortality. These results indicate that when one controls for differences in prognostic index between the groups, cobalt-60 plaque therapy and enucleation are essentially equivalent in their effect on survival.

  12. [Differentiation activity of pyridoxal thiosemicarbazone and its copper and cobalt complexes on Friend erythroleukemia cells].

    PubMed

    Albertini, R; Gasparri Fava, G; Pinelli, S; Tarasconi, P; Starcich, B

    1991-07-01

    Thiosemicarbazones are a wide group of organic derivatives whose biological activities are a function of the parent aldehyde or ketone and of the coordination metal type. Some thiosemicarbazones possess a broad spectrum of potentially useful chemotherapeutic properties (antitumor, antibacterial, antiviral, antimalarial). The present study reports the biological effects of pyridoxal thiosemicarbazone, H2L, and relative complexes with copper, [(Cu(HL)(OH2))2]++ and with cobalt, [Co(III)(L)(HL)] on the differentiation of Friend erythroleukemia cells (FLC). They are murine proerythroblasts chronically infected by a producing Friend leukemia virus complex; their exposure to dimethylsulfoxide (Me2SO) or other chemical agents induces these cells to terminal erythroid differentiation, therefore these cells represent a good model of differentiation in vitro. Here we describe induction differentiation experiment of pyridoxal thiosemicarbazone and relative complexes of copper and cobalt on FLC performed with concentrations of 50 ug/ml (ligand), 2 ug/ml (complexes). These have little effects on cell proliferation at doses used in these experiments. Higher doses have evident cytotoxic effects. The treatment with the copper complex induces a moderate differentiation of FLC and enhances effects on erythroid differentiation of Me2SO-induced FLC. On the contrary H2L and [Co(III)(L)(HL)] haven't inducing effects or enhancing effects on Me2SO-induced FLC hemopoietic differentiation. In conclusion, the present study shows that copper complexes of pyridoxal thiosemicarbazone exert action of inducing agent and are able to enhance Me2SO-induced FLC hemopoietic differentiation. PMID:1818592

  13. Preparation of cobalt ferrite nanoparticles via a novel solvothermal approach using divalent iron salt as precursors

    SciTech Connect

    Ma, Jie; Green Bio- and Eco-Chem. Eng. Lab, University of Shanghai for Science and Technology ; Zhao, Jiantao; Li, Wenlie; Zhang, Shuping; Green Bio- and Eco-Chem. Eng. Lab, University of Shanghai for Science and Technology ; Tian, Zhenran; Basov, Sergey

    2013-02-15

    Graphical abstract: CoFe{sub 2}O{sub 4} nanoparticles are obtained via solvothermal approach using Fe{sup 2+} salt as iron resource. The magnetic properties can be modified by some additives. Display Omitted Highlights: ► CoFe{sub 2}O{sub 4} nanoparticles are synthesized by a facile one-step novel solvothermal method. ► The system is firstly performed in water–glycol mixture solvent with an ordinary air surrounding. ► The ferrous ions are used as iron source without adding oxidant. ► It is firstly found the low-coercivity CoFe{sub 2}O{sub 4} nanoparticles can be obtained with the help of some additives in the synthesis system. -- Abstract: Cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles are synthesized by a facile novel solvothermal method. The reactions are firstly performed in water–glycol system and Fe{sup 2+} salt is used as iron source without oxidant help. Some factors influenced the reactions, including temperature, reaction time, additives, are investigated. The samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. The magnetic properties of some samples are detected by vibrating sample magnetometry techniques (VSM). It is firstly found that the magnetism of cobalt ferrites nanomaterials can be modified by some additives. The coercivity of CoFe{sub 2}O{sub 4} nanoparticles evidently decreases from 600 to 50 Oe in the presence of PEG-4000 in the system.

  14. Chiral Cobalt(III) Complexes as Bifunctional Brønsted Acid-Lewis Base Catalysts for the Preparation of Cyclic Organic Carbonates.

    PubMed

    Rulev, Yuri A; Larionov, Vladimir A; Lokutova, Anastasia V; Moskalenko, Margarita A; Lependina, Ol'ga L; Maleev, Victor I; North, Michael; Belokon, Yuri N

    2016-01-01

    Stereochemically inert cationic cobalt(III) complexes were shown to be one-component catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa carbon dioxide pressure. The optimal catalyst possessed an iodide counter anion and could be recycled. A catalytic cycle is proposed in which the ligand of the cobalt complexes acts as a hydrogen-bond donor, activating the epoxide towards ring opening by the halide anion and activating the carbon dioxide for subsequent reaction with the halo-alkoxide. No kinetic resolution was observed when terminal epoxides were used as substrates, but chalcone oxide underwent kinetic resolution. PMID:26663897

  15. Suitability of cation substituted cobalt ferrite materials for magnetoelastic sensor applications

    SciTech Connect

    Nlebedim, Ikenna Catjetan; Jiles, David C

    2015-02-01

    The results of a study on the suitability of materials derived from cobalt ferrite for sensor and actuator applications are presented. The mechanism responsible for the superior sensor properties of Ge-substituted cobalt ferrite compared with Ti and other cation substituted cobalt ferrite materials is believed to be due to the tetrahedral site preference of Ge4+ and its co-substitution with Co2+. Results also showed that the higher strain derivative of Ge-substituted cobalt ferrite compared with Ti-substitution is due to a higher magnetostrictive coupling in response to applied field in the material.

  16. Cobalt cluster effects in zirconium promoted Co/SiO{sub 2} Fischer-Tropsch catalysts

    SciTech Connect

    Feller, A.; Claeys, M.; Steen, E. van

    1999-07-01

    The effect of zirconium addition to the catalyst formulation of Co/SiO{sub 2} Fischer-Tropsch catalysts was investigated. With increasing zirconium content the strong interaction between silica and cobalt is reduced and a somewhat weaker cobalt-zirconium interaction is observed. Therefore the degree of reduction of catalysts, which were reduced at 400 C for 16 h, increases strongly. The cobalt crystallite size increases with increasing zirconium content, leading to smaller cobalt metal surface areas for the freshly reduced catalyst. Cobalt particles can be found in clusters on the silica support. The size of cobalt clusters decreases and thus the number of cobalt particles within a cluster decreases with increasing zirconium content. At steady-state conditions the CO-conversion of the promoted catalyst in the Fischer-Tropsch synthesis increases with increasing zirconium content. The C{sub 5+}-selectivity and the secondary hydrogenation activity pass a maximum with increasing zirconium content. The observed changes in activity and selectivity are explained in terms of an increase in the amount of metallic cobalt available under reaction conditions, leading to an increased activity, and a decrease in the cobalt cluster size, which diminishes the probability for secondary reactions. Furthermore, it was concluded that secondary double bond isomerization can be catalyzed to some extent by zirconia.

  17. Influence of initial particle size on the magnetostriction of sintered cobalt ferrite derived from nanocrystalline powders

    NASA Astrophysics Data System (ADS)

    Khaja Mohaideen, K.; Joy, P. A.

    2013-11-01

    The role of initial particle size on the magnetostriction coefficient of sintered cobalt ferrite derived from nanocrystalline powders is studied. Nanoparticles of cobalt ferrite with different sizes in the range 3-80 nm are synthesized by an autocombustion method using metal nitrates and glycine. It has been observed that the initial particle size of the starting powders has a strong influence on the magnetostrictive behavior of sintered cobalt ferrite. Highest magnetostrictive strain and strain derivative are obtained for sintered ferrite derived from nanoparticles of size < 5 nm. The results show that higher magnetostriction coefficient for sintered cobalt ferrite can be achieved by compacting nanocrystalline particles of very small size.

  18. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion.

    PubMed

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  19. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    NASA Astrophysics Data System (ADS)

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-06-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones.

  20. In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion

    PubMed Central

    Wang, Han; Chen, Chunlin; Zhang, Yexin; Peng, Lixia; Ma, Song; Yang, Teng; Guo, Huaihong; Zhang, Zhidong; Su, Dang Sheng; Zhang, Jian

    2015-01-01

    Combustion catalysts have been extensively explored to reduce the emission of hydrocarbons that are capable of triggering photochemical smog and greenhouse effect. Palladium as the most active material is widely applied in exhaust catalytic converter and combustion units, but its high capital cost stimulates the tremendous research on non-noble metal candidates. Here we fabricate highly defective cobalt oxide nanocrystals via a controllable oxidation of carbon-encapsulated cobalt nanoparticles. Strain gradients induced in the nanoconfined carbon shell result in the formation of a large number of active sites featuring a considerable catalytic activity for the combustion of a variety of hydrocarbons (methane, propane and substituted benzenes). For methane combustion, the catalyst displays a unique activity being comparable or even superior to the palladium ones. PMID:26074206

  1. Cobalt substitution studies on bovine erythrocyte superoxide dismutase: evidence for a novel cobalt-superoxide dismutase derivative.

    PubMed

    Salvato, B; Beltramini, M; Ricchelli, F; Tallandini, L

    1989-09-14

    Three cobalt derivatives of bovine erythrocyte superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) have been prepared under different pH conditions using a cobalt-thiocyanate complex which has already proved to yield specific substitutions on other copper proteins. The cobalt-protein derivatives have been characterized by optical, circular dichroism and fluorescence spectroscopies. One derivative, referred to as Co2Co2-protein, contains Co(II) ions specifically bound at both Zn(II) and Cu(II) sites. On the basis of their spectroscopic properties, the other two derivatives can be referred as E2Co2- and Co2E2-superoxide dismutase, with cobalt substituting, respectively, at the zinc and the copper sites leaving the contiguous site empty (E). The Co2E2-protein complex represents a novel derivative, since it has never been described in literature. The optical spectrum in the visible region of Co2-Co2-protein well corresponds to the sum of the spectra of the other two derivatives. The circular dichroism spectrum of Co2Co2-derivative, however, is not the sum of individual E2Co2- and Co2E2-proteins, suggesting that the presence of Co(II) in one site strongly affects the geometry of the neighbouring site. Some discrepancies between our spectroscopic data and those reported in literature are discussed. The results obtained from fluorescence experiments indicate that Co(II) ions exert a different quenching effect on the tyrosine emission, depending on whether they are located in the Zn(II) or in the Cu(II) site. The fluorescence quenching can be attributed to a 'heavy atom' and 'paramagnetic ion' effect by Co(II) ions. PMID:2790051

  2. Hydroxamate-induced spectral perturbations of cobalt Aeromonas aminopeptidase.

    PubMed

    Wilkes, S H; Prescott, J M

    1987-06-25

    The absorption spectrum of cobalt(II)-substituted Aeromonas aminopeptidase is markedly perturbed by the presence of equimolar concentrations of D-amino acid hydroxamates and acyl hydroxamates that have previously been shown to be powerful inhibitors of this enzyme (Wilkes, S. H., and Prescott, J. M. (1983) J. Biol. Chem. 258, 13517-13521). D-Valine hydroxamate produces the most distinctive perturbation, splitting the characteristic 527 nm absorption peak of the cobalt enzyme to form peaks at 564, 520, and 487 nm with molar extinction values of 126, 98, and 67 M-1 cm-1, respectively. A qualitatively similar perturbation, albeit with lower extinction values, results from the addition of D-leucine hydroxamate, whereas D-alanine hydroxamate perturbs the spectrum, but does not evoke the peak at 564 nm. In contrast, hydroxamates of L-valine and L-leucine in concentrations equi-molar to that of the enzyme produce only faint indications of change in the spectrum, but the hydroxamates of several other L-amino acids perturb the spectrum essentially independently of the identity of the side chain and in a qualitatively different manner from that of D-valine hydroxamate and D-leucine hydroxamate. At the high enzyme:substrate ratios used in the spectral experiments, L-leucine hydroxamate and L-valine hydroxamate proved to be rapidly hydrolyzed, hence their inability to perturb the spectrum of the cobalt-substituted enzyme during the time course of a spectral experiment. Values of kcat for L-amino acid hydroxamates, all of which are good reversible inhibitors of the hydrolysis of L-leucine-p-nitroanilide by Aeromonas aminopeptidase, were found to range from 0.01 min-1 to 5.6 min-1 for the native enzyme and from 0.27 min-1 to 108 min-1 for the cobalt-substituted enzyme; their km values toward the cobalt aminopeptidase range from 1.2 X 10(-7) M to 1.9 X 10(-5) M. The mutual exclusivity of binding for hydroxamate inhibitors and 1-butaneboronic acid, previously shown by kinetics

  3. Processing of functionally graded tungsten carbide-cobalt-diamond composites

    NASA Astrophysics Data System (ADS)

    Jain, Mohit

    Polycrystalline diamond compacts (PDCs) are widely used as drill bit cutters in rock drilling and as tool bits in machining non-ferrous materials. A typical PDC comprises a thin layer of sintered polycrystalline diamond bonded to a tungsten carbide-cobalt substrate. A well recognized failure mechanism is delamination at the interface between diamond and cemented carbide. High stresses at the diamond/carbide interface, due to thermal expansion and modulus mismatch, are the primary cause of in-service failure under impact loading conditions. This work was undertaken to develop a tungsten carbide-cobalt-diamond composite, which has a continuously graded interface between the diamond and tungsten carbide. The process developed comprised the following steps: (i) generation of a pore size gradient by electrochemical etching of cobalt from the surface of a partially sintered tungsten carbide-cobalt preform; (ii) chemical vapor infiltration of the porous preform with carbon by catalytic decomposition of a methane/hydrogen mixture, resulting in a graded carbon concentration; and (iii) consolidation of the carbon infiltrated preforms at 8GPa/1500°C to complete densification and to transform the carbon into diamond. Thus, the final product consists of a functionally graded WC-Co-diamond composite, with controlled distribution of the constituent phases. Tungsten carbide-cobalt powders with mean tungsten carbide particle size of 0.8mum(micro-grain) and 100 nm(nano-grain) were used as starting materials. Processing conditions were adjusted to obtain an optimal distribution of carbon in porous preforms. After high pressure/high temperature consolidation, both micro- and nano-composites showed a diffused interface between inner and outer regions of the fully dense materials. A micro-composite showed columnar-like tungsten carbide grains and faceted diamond grains in the outer region of the sintered material. The grain size of the diamond in this region was ˜2mum, and the

  4. Heat treatment of cobalt-chromium alloy wire.

    PubMed

    Fillmore, G M; Tomlinson, J L

    1976-04-01

    This study shows that the ability of cobalt-chromium wire to resist permanent deformation is definitely affected by the temperature of heat treatment. For each temperature of heat treatment up to 1200 degrees F there is progressively greater resistance to permanent deformation; at temperatures of heat treatment above 1200 degrees F, however, there is a rapid decline in resistance to permanent deformation due to partial annealing. The maximum resistance to permanent deformation occurs from heat treatment in the temperature range of 1100 degrees to 1200 degrees F. A clinician desiring maximum resistance to permanent deformation from a .016 inches x .022 inches cobalt-chromium archwire should heat-treat the wire at 1100 degrees to 1200 degrees F for 5 minutes in a dental furnace. If the wire was in a highly work-hardened condition as were the wire specimens of this study, he could expect an increase in resistance to permanent deformation of approximately 174 percent. Heat treatment at lower temperatures could be used in situations requiring less than maximum resistance to permanent deformation. Heat treatment at 900 degrees F would give approximately a 95 percent increase in resistance to permanent deformation. Of course, heat treatment would not be indicated when the desired level of resistance to permanent deformation was not greater than the amount exhibited in the untreated wires of this study. When an electrical resistance heat-treatment unit and 950 degrees F temper-indicating paste were used, the clinician would expect increased resistance to permanent deformation similar to that seen in the wires heat-treated with a dental furnace at 800 degrees and 900 degrees F, i.e., about half of that obtained by the 1200 degrees F treatment. This study has determined the effects that various temperatures of heat treatment have on the resistance to permanent deformation of cobalt-chromium wire specimens which were formed into a specific pattern of loops. The following

  5. The formation of volatile corrosion products during the mixed oxidation-chlorination of cobalt at 650 C

    NASA Technical Reports Server (NTRS)

    Jacobson, N. S.; Mcnallan, M. J.; Lee, Y. Y.

    1986-01-01

    The reaction of cobalt with 1 pct Cl2 in 1, 10, and 50 pct O2/Ar atmospheres has been studied at 650 C with thermogravimetry and mass spectrometry. The principal vapor species appear to be CoCl2 and CoCl3. In all cases, CoCl2(s) forms at the oxide/metal interface and equilibration of the volatile chlorides with Co3O4 does not occur in the early stages of the reaction. In the 1 pct Cl2 1 pct O2-Ar case, continuous volatilization occurs. In the 1 pct Cl2-10 pct O2-Ar and 1 pct CL2-50 pct O2-Ar cases, volatilization occurs only in the first few minutes of reaction. Afterwards, the reaction is predominantly oxidation.

  6. Effect of variations of cobalt content on the cyclic oxidation resistance of selected Ni-base superalloys

    SciTech Connect

    Barrett, C.A.

    1986-03-01

    Cobalt levels were systematically varied in the Ni-base turbine alloys U-700 (cast), U-700m(PM/HIP), Waspaloy, Mar-M-247, In-738, Nimonic-115, U-720, and SX-R-150. The cobalt levels ranged from 0 wt % to the nominal commercial content in each alloy. The alloys were tested in cyclic oxidation in static air at 1000, 1100 and 1150 C for 500, 200 and 100 hr respectively. An oxidation attack parameter, Ka derived from the specific weight change versus time data was used to evaluate the oxidation behavior of the alloys along with X-ray diffraction analysis of the surface oxides. The alloys tend to form either Cr/sub 2/O/sub 3//chromite spinel or Al/sub 2/O/sub 3//aluminate spinel depending on the CR/Al ratio in the alloys. Alloys with a ratio of 3.5 or higher tend to favor the Cr oxides while those under 3.0 form mostly Al oxides. In general the Al/sub 2/O/sub 3//aluminate spinel forming alloys have the better oxidation resistance. Increased cobalt content lowers the scaling resistance of the higher Cr alloys while a 5.0 wt % Co content is optimum for the Al controlling alloys. The refractory metals, particularly Ta, appear beneficial to both types of oxides perhaps due to the formation of the omni-present trirutile Ni(Ta,Cb,Mo,W)2O6. Both scales break down as increasing amounts of NiO is formed.

  7. Eco-friendly microbial route to synthesize cobalt nanoparticles using Bacillus thuringiensis against malaria and dengue vectors.

    PubMed

    Marimuthu, Sampath; Rahuman, Abdul Abdul; Kirthi, Arivarasan Vishnu; Santhoshkumar, Thirunavukkarasu; Jayaseelan, Chidambaram; Rajakumar, Govindasamy

    2013-12-01

    The developments of resistance and persistence to chemical insecticides and concerns about the non-target effects have prompted the development of eco-friendly mosquito control agents. The aim of this study was to investigate the larvicidal activities of synthesized cobalt nanoparticles (Co NPs) using bio control agent, Bacillus thuringiensis against malaria vector, Anopheles subpictus and dengue vector, Aedes aegypti (Diptera: Culicidae). The synthesized Co NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy, and Transmission electron microscopy (TEM). XRD analysis showed three distinct diffraction peaks at 27.03°, 31.00°, and 45.58° indexed to the planes 102, 122, and 024, respectively on the face-centered cubic cobalt acetate with an average size of 85.3 nm. FTIR spectra implicated role of the peak at 3,436 cm(-1) for O-H hydroxyl group, 2924 cm(-1) for methylene C-H stretch in the formation of Co NPs. FESEM analysis showed the topological and morphological appearance of NPs which were found to be spherical and oval in shape. TEM analysis showed polydispersed and clustered NPs with an average size of 84.81 nm. The maximum larvicidal mortality was observed in the cobalt acetate solution, B. thuringiensis formulation, and synthesized Co NPs against fourth instar larvae of A. subpictus and A. aegypti with LC50 values of 29.16, 8.12, 3.59 mg/L; 34.61, 6.94, and 2.87 mg/L; r (2) values of 0.986, 0.933, 0.942; 0.962, 0.957, and 0.922, respectively. PMID:24013343

  8. Characterization of cobalt doped ZnSe and ZnS crystals as saturable absorbers for alexandrite lasers

    NASA Astrophysics Data System (ADS)

    Sims, Robert A.; Kernal, John; Fedorov, Vladimir V.; Mirov, Sergey B.

    2006-02-01

    Cobalt doped ZnSe and ZnS crystals have been studied to determine their effectiveness for passive Q-switching for 700-800nm spectral range (Alexandrite laser). Samples were prepared using Bridgeman technique for single-step growth of Co doped crystals as well as after growth thermal diffusion of Co in undoped crystals. ZnS:Co:Cr crystals, which have been produced using the Bridgeman technique, show maximum initial absorption coefficients of 17 cm -1 at 725nm. Experimental results are reported on effective thermal diffusion of Co 2+ in ZnSe and ZnS polycrystals and thermal diffusion constants of cobalt ions in ZnSe and ZnS are estimated. The nonlinear saturation properties of cobalt doped ZnSe and ZnS crystals have been investigated experimentally. The induced transparency measurements were performed using electro-optically Q-switched, alexandrite laser radiation at 731, 741, and 778 nm with a pulse duration of about 70 ns. The induced transmission measurements were analyzed using a four-level absorber model and the absorption cross sections have been estimated at both 731nm and 741nm to be 9.5 × 10 -18 cm2 and 8.2 × 10 -18 cm2, respectively. Absorption cross sections calculated from saturation measurements at 4A II--> 4T I(4P) transition are in agreement with results earlier reported for mid-infrared spectral region 4A II--> 4T II of Co 2+ ions. The described Co-doped crystals are very promising as passive Q-switches for alexandrite laser resonators. Co 2+ centers feature high cross section of saturation and their absorption bands are nicely matched to the spectral emission of the tunable alexandrite laser. An efficient ZnS:Co:Cr passive Q-switching of the alexandrite laser cavity was realized with output energy of 15 mJ and 50 ns pulse duration.

  9. An hydrothermal experimental study of the cobalt-cobalt oxide redox buffer

    USGS Publications Warehouse

    Lemke, K.H.; Rosenbauer, R.J.; Bischoff, J.L.; Bird, D.K.

    2008-01-01

    Equilibrium aqueous hydrogen concentration and corresponding energies of reaction, ??Grxno(T, P), for the reaction Co(s) + H2O(l) = CoO(s) + H2(aq) have been determined at temperatures between 256 and 355 ??C and at 400 bar. Steady-state concentrations of hydrogen were approached in experiments under conditions of both H2 excess and deficiency containing the solids Co, CoO and liquid water. All experiments were carried out in flexible gold and titanium reactors with the capability of on-line fluid sampling. Measured equilibrium molal concentrations of H2(aq) at 256, 274, 300, 324 and 355 ??C are 0.81(?? 0.01) ?? 10- 3 1.11(?? 0.01) ?? 10- 3, 1.92(?? 0.01) ?? 10- 3, 3.71(?? 0.06) ?? 10- 3, 7.54(?? 0.12) ?? 10- 3, respectively, and corresponding values of ??Grxno(T, P) in units kJ ?? mol- 1 are 31.4(?? 0.1), 31.0(?? 0.1), 29.8(?? 0.1), 27.7(?? 0.5) and 25.5(?? 0.9), respectively. Using published heat capacity data for Co(s) and CoO(s) and - 79.6 J ?? mol- 1 ?? K- 1 for the entropy of formation of CoO we calculated for this study a value for ??GCoO,Tr,Pro = - 214.5(?? 0.9) kJ ?? mol- 1 and ??HCoO,Tr,Pro = - 238.3(?? 0.9) kJ ?? mol- 1 at 25 ??C and 1 bar. The value of ??HCoO,Tr,Pro determined in this study compares well with the reported calorimetric value of - 238.9(?? 1.2) kJ ?? mol- 1 [Boyle, B.J., King, E.G., Conway, K.C., 1954. Heats of formation of nickel and cobalt oxides (NiO and CoO) by combustion calorimetry. Journal of the American Chemical Society, 76, 3835-3837]. ?? 2008 Elsevier B.V. All rights reserved.

  10. Effect of cobalt supplementation and fractionation on the biological response in the biomethanization of Olive Mill Solid Waste.

    PubMed

    Pinto-Ibieta, F; Serrano, A; Jeison, D; Borja, R; Fermoso, F G

    2016-07-01

    Due to the low trace metals concentration in the Olive Mill Solid Waste (OMSW), a proposed strategy to improve its biomethanization is the supplementation of key metals to enhance the microorganism activity. Among essential trace metals, cobalt has been reported to have a crucial role in anaerobic degradation. This study evaluates the effect of cobalt supplementation to OMSW, focusing on the connection between fractionation of cobalt in the system and the biological response. The highest biological responses was found in a range from 0.018 to 0.035mg/L of dissolved cobalt (0.24-0.65mg total cobalt/L), reaching improvements up to 23% and 30% in the methane production rate and the methane yield coefficient, respectively. It was found that the dissolved cobalt fraction is more accurately related with the biological response than the total cobalt. The total cobalt is distorted by the contribution of dissolved and non-dissolved inert fractions. PMID:26998798

  11. Effect of Temperature and Grain Size on Magnetic Properties of Soft Magnetic Iron-Cobalt Alloys

    NASA Astrophysics Data System (ADS)

    Kozlowski, G.; Fingers, R. T.; Coate, J. E.; Rogacki, K.; Dabrowski, B.

    1997-03-01

    Two specific iron-cobalt alloys have been tested as part of the magnetic materials characterization program at Wright Laboratory. The first material is Hiperco Alloy 50HS from Carpenter Technology and the second is HS50 from Telcon Ltd. The planned use of such materials in cyclic high temperature high stress environments (generators and magnetic bearings) gives impetus to determining material properties. These soft magnetic alloys exhibit high magnetic saturation, high yield strength, and moderate core loss. In order to better understand the overall behavior of these alloys, both mechanical and magnetic phenomena have been investigated. Specimens of these materials have been heat treated by various recipes ranging in temperature from 1300 degF to 1350 degF and magnetic saturation along hysteresis loop measurements were made using a vibrating sample magnetometer and an a.c. susceptometer. Measurements of remanence, coercivity, permeabilities and saturation were made as a function of temperature. Mechanical testing was also conducted and these results were used in conjunction with the magnetic behavior to characterize the two specific alloys. Etching and sample preparation processes were developed and microstructural analyses were performed. The effect of composition and heat treatment of these two soft magnetic materials and how they may influence potential applications is discussed.

  12. Electrooxidation and Determination of Dopamine Using a Nafion®-Cobalt Hexacyanoferrate Film Modified Electrode

    PubMed Central

    Castro, Suely S. L.; Mortimer, Roger J.; de Oliveira, Marcelo F.; Stradiotto, Nelson R.

    2008-01-01

    The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%.

  13. Synthesis, structures and urease inhibitory activity of cobalt(III) complexes with Schiff bases.

    PubMed

    Jing, Changling; Wang, Cunfang; Yan, Kai; Zhao, Kedong; Sheng, Guihua; Qu, Dan; Niu, Fang; Zhu, Hailiang; You, Zhonglu

    2016-01-15

    A series of new cobalt(III) complexes were prepared. They are [CoL(1)(py)3]·NO3 (1), [CoL(2)(bipy)(N3)]·CH3OH (2), [CoL(3)(HL(3))(N3)]·NO3 (3), and [CoL(4)(MeOH)(N3)] (4), where L(1), L(2), L(3) and L(4) are the deprotonated form of N'-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide, N'-(2-hydroxybenzylidene)-3-hydroxylbenzohydrazide, 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol, and N,N'-bis(5-methylsalicylidene)-o-phenylenediamine, respectively, py is pyridine, and bipy is 2,2'-bipyridine. The complexes were characterized by infrared and UV-Vis spectra, and single crystal X-ray diffraction. The Co atoms in the complexes are in octahedral coordination. Complexes 1 and 4 show effective urease inhibitory activities, with IC50 values of 4.27 and 0.35 μmol L(-1), respectively. Complex 2 has medium activity against urease, with IC50 value of 68.7 μmol L(-1). While complex 3 has no activity against urease. Molecular docking study of the complexes with Helicobacter pylori urease was performed. PMID:26712097

  14. Transport properties of lead phosphate glass doped by cobalt, vanadium and chromium oxides

    NASA Astrophysics Data System (ADS)

    Roumaih, Kh.; Kaiser, M.; Elbatal, Fatma H.; Ali, I. S.

    2011-10-01

    The electrical transport properties were investigated of a glass system of basic composition 50 mol. % Pb3O4-50 mol. % P2O5 containing CoO, Cr2O3 or V2O5 dopanys. The ac conductivity and the thermoelectric power were measured as a function of temperature. Properties such as dielectric constant, loss factor tangent and electrical conductivity are reported in the frequency range 200 Hz-100 kHz and temperature range 300-450 K. The variation in electrical conductivity with temperature was found to depend on the types of transition metal ions involved. The temperature dependence of the frequency exponent, s, was analyzed using different theoretical models. The variation of the thermoelectric power with temperature indicated the presence of more than one conduction mechanism for the investigated samples. This result was confirmed with the results of the dielectric properties at different frequencies. The introduction of cobalt ions in glass formers improves the electrical properties of non-crystalline ionic conductors.

  15. 77 FR 3750 - Notice of Intent To Grant a Partially Exclusive License; Cobalt Technologies, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF DEFENSE Department of the Navy Notice of Intent To Grant a Partially Exclusive License; Cobalt Technologies, Inc... notice of its intent to grant to Cobalt Technologies, Inc., a revocable, nonassignable,...

  16. Understanding the roles of the strategic element cobalt in nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Dreshfield, R. L.

    1983-01-01

    The United States imports over 90% of its cobalt, chromium, columbium, and tantalum, all key elements in high temperature nickel base superalloys for aircraft gas turbine disks and airfoils. Research progress in understanding the roles of cobalt and some possible substitutes effects on microstructure, mechanical properties, and environmental resistance of turbine alloys is discussed.

  17. Effects of Cobalt on Structure, Microchemistry and Properties of a Wrought Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Jarrett, Robert N.; Tien, John K.

    1982-06-01

    Cobalt in a 17 pct cobalt containing wrought nickel-base superalloy is systematically substituted for by nickel in order to determine the role of cobalt. The eventual goal is to reduce the levels of cobalt, a critical strategic element, in superalloys. It is found that the strengthening γ microstructure is highly heat treatment sensitive. Reducing cobalt did not result in a reduction of the fine γ precipitates after a coarse grain type (blading) heat treatment, but did after a fine grain type (disk) heat treatment. Representative mechanical properties were determined for each case to isolate microstructural and microchemistry effects. Ambient yield strength and tensile strength were seen to decrease by no more than 15 pct and 7 pct, respectively, even when all the cobalt was removed. The decrease in strength is quantitatively discussed and shown to be consistent with the observed microstructural results and microchemistry results obtained using STEM/EDS. Elevated temperature creep and stress rupture resistances were concluded to be affected by alloy cobalt content through its effect on strengthening γ volume fraction. Significant decreases in these properties were observed for the lower cobalt content alloys. Long term aging, precipitate coarsening, and carbide stability results are also presented and discussed.

  18. Cobalt-Catalyzed Alkyne Hydrosilylation and Sequential Vinylsilane Hydroboration with Markovnikov Selectivity.

    PubMed

    Zuo, Ziqing; Yang, Ji; Huang, Zheng

    2016-08-26

    A pyridinebis(oxazoline) cobalt complex is a very efficient precatalyst for the hydrosilylation of terminal alkynes with Ph2 SiH2 , providing α-vinylsilanes with high (Markovnikov) regioselectivity and broad functional-group tolerance. The vinylsilane products can be further converted into geminal borosilanes through Markovnikov hydroboration with pinacolborane and a bis(imino)pyridine cobalt catalyst. PMID:27479796

  19. Cobalt catalysts for the conversion of methanol to hydrocarbons and for Fischer-Tropsch Synthesis

    SciTech Connect

    Mauldin, C.H.

    1986-02-04

    This patent describes a catalyst useful for the conversion at reaction conditions of methanol or synthesis gas to hydrocarbons by contact with a catalyst. The catalyst cobalt and thorium in catalytically active amounts, and rhenium, composited with an inorganic oxide support in weight ratio of rhenium:cobalt ranging from about 0.025:1 to about 0.10:1.

  20. The impact of rare earth cobalt permanent magnets on electromechanical device design

    NASA Technical Reports Server (NTRS)

    Fisher, R. L.; Studer, P. A.

    1979-01-01

    Specific motor designs which employ rare earth cobalt magnets are discussed with special emphasis on their unique properties and magnetic field geometry. In addition to performance improvements and power savings, high reliability devices are attainable. Both the mechanism and systems engineering should be aware of the new performance levels which are currently becoming available as a result of the rare earth cobalt magnets.

  1. [Activity of Ca(2+)-dependent neutral proteinases in rat organs under cobalt and mercury chloride injection].

    PubMed

    Kaliman, P A; Samokhin, A A; Samokhina, L M

    2003-01-01

    The activity of Ca(2+)-dependent neutral proteinases in rats under cobalt and mercury chloride injection was investigated. The calpains activity increase in the lungs, heart, liver and kidneys was revealed after 2 h cobalt chloride action. The mercury chloride gives a reliable increase of calcium-dependent neutral proteinases only in the kidneys. PMID:14574747

  2. Chitosan-modified cobalt oxide nanoparticles stimulate TNF-α-mediated apoptosis in human leukemic cells.

    PubMed

    Chattopadhyay, Sourav; Dash, Sandeep Kumar; Kar Mahapatra, Santanu; Tripathy, Satyajit; Ghosh, Totan; Das, Balaram; Das, Debasis; Pramanik, Panchanan; Roy, Somenath

    2014-03-01

    The objective of this study was to develop chitosan-based delivery of cobalt oxide nanoparticles to human leukemic cells and investigate their specific induction of apoptosis. The physicochemical properties of the chitosan-coated cobalt oxide nanoparticles were characterized using transmission electron microscopy, dynamic light scattering, X-ray diffraction, and Fourier transform infrared spectroscopy. The solubility of chitosan-coated cobalt oxide nanoparticles was higher at acidic pH, which helps to release more cobalt ions into the medium. Chitosan-coated cobalt oxide nanoparticles showed good compatibility with normal cells. However, our results showed that exposure of leukemic cells (Jurkat cells) to chitosan-coated cobalt oxide nanoparticles caused an increase in reactive oxygen species generation that was abolished by pretreatment of cells with the reactive oxygen species scavenger N-acetyl-L-cysteine. The apoptosis of Jurkat cells was confirmed by flow-cytometric analysis. Induction of TNF-α secretion was observed from stimulation of Jurkat cells with chitosan-coated cobalt oxide nanoparticles. We also tested the role of TNF-α in the induction of Jurkat cell death in the presence of TNF-α and caspase inhibitors. Treatment of leukemic cells with a blocker had a greater effect on cancer cell viability. From our findings, oxidative stress and caspase activation are involved in cancer cell death induced by chitosan-coated cobalt oxide nanoparticles. PMID:24445996

  3. Cobalt(III)Hexaammine-Dependent Photocrosslinks in the Hairpin Ribozyme

    PubMed Central

    Kraemer-Chant, Christina M.; Heckman, Joyce E.; Lambert, Dominic; Burke, John M.

    2014-01-01

    We have utilized the hairpin ribozyme, an RNA enzyme whose structure has been solved by high-resolution methods, to develop a new tool for mapping nucleobase-stacking interactions and potential metal-binding sites in RNA molecules. This tool involves the photoactivation of a specifically bound cobalt(III)hexaammine molecule at wavelengths corresponding to excitation of the metal ion complex only; no base excitation is involved. The photoexcitation initiates a process which strongly promotes the formation of a novel covalent bond or crosslink between one base (termed the “first base”), which is close in space to the excited cobalt(III)hexaammine complex, and another base upon which the first base is closely stacked. These crosslinked species can be isolated and sequenced; their activities can be analyzed to ensure that the crosslinked structures represent an active conformation of the molecule. We have shown that, as in electron transfer in DNA, several criteria must be met to result in the successful formation of these crosslinks. These include the appropriate oxidation potential of the first donor base, the stacking and close interaction of the two donor bases involved in the crosslink, and the binding of a specific cobalt(III)hexaammine molecule to the first donor base. Additionally, we have determined that this crosslinking is pH-sensitive, although the cause of this sensitivity remains unknown. This tool has proven useful in the past for the analysis of the hairpin ribozyme folded structure, and has been applied to identifying potential metal-binding sites on the hairpin and extended hammerhead ribozymes. PMID:24295878

  4. Synthesis and properties of a few 1-D cobaltous fumarates

    SciTech Connect

    Bora, Sanchay J.; Das, Birinchi K.

    2012-08-15

    Metal fumarates are often studied in the context of metal organic framework solids. Preparation, structure and properties of three cobalt(II) fumarates, viz. [Co(fum)(H{sub 2}O){sub 4}]{center_dot}H{sub 2}O 1, [Co(fum)(py){sub 2}(H{sub 2}O){sub 2}] 2, and [Co(fum)(4-CNpy){sub 2}(H{sub 2}O){sub 2}] 3 (fum=fumarate, py=pyridine, 4-CNpy=4-cyanopyridine) are described. All three are chain polymers involving bridging fumarato ligands between each pair of octahedral Co(II) centres, but while the first one is zigzag in structure, the latter two are linear. Indexed powder X-ray diffraction patterns, solid state electronic spectra and magnetic properties of the species are reported. Thermal decomposition behaviour of the compounds suggests that they may be suitable as precursors to make Co{sub 3}O{sub 4} via pyrolysis below 600 Degree-Sign C. - Graphical abstract: Structure and properties of three chain-polymeric cobalt(II) fumarates are described. Highlights: Black-Right-Pointing-Pointer Three fumarate bridged 1-D coordination polymers of cobalt(II) are reported. Black-Right-Pointing-Pointer While Co(II) fumarate pentahydrate is zigzag, the species having both pyridine and water as co-ligands are linear in structure. Black-Right-Pointing-Pointer Prominent lines in the powder X-ray diffraction patterns have been indexed. Black-Right-Pointing-Pointer Thermal decomposition of the species yields Co{sub 3}O{sub 4} as the final product.

  5. Preparation-morphology-performance relationships in cobalt aerogels as supercapacitors.

    PubMed

    Peterson, Geneva R; Hung-Low, Fernando; Gumeci, Cenk; Bassett, Will P; Korzeniewski, Carol; Hope-Weeks, Louisa J

    2014-02-12

    The ability to direct the morphology of cobalt sol-gel materials by using the simple synthetic parameters in epoxide-driven polycondensations has been dramatically demonstrated, and the influence of such morphological differences upon the supercapacity of the materials has been explored. Precursor salt, epoxide, and solvent all influence the speed of the sol-gel transition and the size and shape of the features observed in the as-prepared materials, thereby leading to highly varied microstructures including spheres, sponge-like networks, and plate assemblies of varied size. These morphological features of the as-prepared cobalt aerogels were observed for the first time by high resolution scanning electron microscopy (HRSEM). The as-prepared aerogel materials were identified by powder X-ray diffraction and thermogravimetry as weakly crystalline or amorphous cobalt basic salts with the general formula Co(OH)(2-n)X(n) where X = Cl or NO3 according to the precursor salt used in the synthesis. For all samples, the morphology was preserved through mild calcining to afford spinel phase Co3O4 in a variety of microstructures. Wide-ranging specific surface areas were determined for the as-prepared and calcined phases by physisorption analysis in agreement with the morphologies observed by HRSEM. The Co3O4 aerogels were evaluated for their supercapacitive performance by cyclic voltammetry. The various specimens exhibit capacitances ranging from 110 to 550 F g(-1) depending upon the attributes of the particular aerogel material, and the best specimen was found to have good cycle stability. These results highlight the epoxide-driven sol-gel condensation as a versatile preparative route that provides wide scope in materials' properties and enables the analysis of structure-performance relationships in metal oxide materials. PMID:24417220

  6. Cobalt-based magnetic nanocomposites: fabrication, fundamentals and applications

    NASA Astrophysics Data System (ADS)

    Wen, Tianlong; Krishnan, Kannan M.

    2011-10-01

    Recently, magnetic nanocomposites (MNC) have aroused significant scientific and technological interests because their properties strongly rely on the interplay between those of the constituent components. Here, using three types of cobalt-based MNCs, we demonstrate how their physical behaviour, including thermal, electrical and magnetic, can be strongly affected by such interplays. First, using Aucore-Coshell nanoparticles (NPs), we demonstrate that their thermal stabilities are critically dependent on various boundaries and they structurally transform from the core-shells to the peanut structures via several intermediate states by a series of energy minimizations including the grain boundaries, Co/Au interface and strain. Second, the microstructures of the MNC are co-determined by the properties of the individual components, which in turn will strongly affect their overall properties. We illustrate this by a careful study of the electron transport in cobalt/poly (3-hexylthiophene, 2, 5-diyl) (P3HT) hybrid thin films, and show that they satisfy a fluctuation-induced tunnelling model that is strongly depended on their microstructures; moreover, a magnetoresistance in these thin films was also observed. Finally, the magnetic properties and phase stability of MNCs can also be strongly altered as a result of this interplay. Three phase transformations are observed in cobalt ferrofluids for T ~ 10-300 K, namely second order magnetic phase transformations (blocked-unblocked transition) at the blocking temperature of the magnetic NP, first order magnetic and structural phase transformations at the solvent melting temperature, TM, and second order premelting transformation at TPM < T < TM. These transformations show specific magnetic signatures in field-cool and zero-field-cool magnetization measurements and are qualitatively in agreement with predictions using M-spectrum theory.

  7. Treatment of spent electropolishing solution for removal of cobalt-60

    SciTech Connect

    Taylor, P.A.; Youngblood, E.L.; Macon, R.J.

    1996-02-01

    The Irradiated Materials Examination and Testing (IMET) Facility at Oak Ridge National Laboratory electropolishes various types of irradiated metal specimens prior to examination of metallurgical and mechanical properties. The standard electropolishing solution used at IMET for most specimens consists of a 7:1 methanol/sulfuric acid mixture, with smaller amounts of a 3:1 methanol/nitric acid solution and a 10:6:1 methanol/2-butoxyethanol/perchloric acid solution also being used. Cobalt-60 is the primary source of gamma radiation in the spent solutions, with lesser amounts from manganese-54 and iron-59. A treatment method is needed to remove most of the Co-60 from these solutions to allow the waste solutions to be contact-handled for disposal. A wide range of adsorbents was tested for removing cobalt from the electropolishing solutions. No adsorbent was found that would treat full strength solution, but a complexing ion exchange resin (Chelex 100, BioRad Labs, or Amberlite IRC-718, Rohm and Haas Co.) will remove cobalt and other heavy metals from partially neutralized (pH=3) solution. A 5 wt% sodium hydroxide solution is used for pH adjustment, since more concentrated caustic caused sodium sulfate precipitates to form. Lab-scale column tests have shown that about 10 bed volumes of methanol/sulfuric acid solution, 30 bed volumes of methanol/nitric acid solution or 15 bed volumes of methanol/2-butoxyethanol/perchloric acid solution can be treated prior to initial Co-60 breakthrough.

  8. Preparation and characterization of cobalt-substituted anthrax lethal factor

    SciTech Connect

    Saebel, Crystal E.; Carbone, Ryan; Dabous, John R.; Lo, Suet Y.; Siemann, Stefan

    2011-12-09

    Highlights: Black-Right-Pointing-Pointer Cobalt-substituted anthrax lethal factor (CoLF) is highly active. Black-Right-Pointing-Pointer CoLF can be prepared by bio-assimilation and direct exchange. Black-Right-Pointing-Pointer Lethal factor binds cobalt tightly. Black-Right-Pointing-Pointer The electronic spectrum of CoLF reveals penta-coordination. Black-Right-Pointing-Pointer Interaction of CoLF with thioglycolic acid follows a 2-step mechanism. -- Abstract: Anthrax lethal factor (LF) is a zinc-dependent endopeptidase involved in the cleavage of mitogen-activated protein kinase kinases near their N-termini. The current report concerns the preparation of cobalt-substituted LF (CoLF) and its characterization by electronic spectroscopy. Two strategies to produce CoLF were explored, including (i) a bio-assimilation approach involving the cultivation of LF-expressing Bacillus megaterium cells in the presence of CoCl{sub 2}, and (ii) direct exchange by treatment of zinc-LF with CoCl{sub 2}. Independent of the method employed, the protein was found to contain one Co{sup 2+} per LF molecule, and was shown to be twice as active as its native zinc counterpart. The electronic spectrum of CoLF suggests the Co{sup 2+} ion to be five-coordinate, an observation similar to that reported for other Co{sup 2+}-substituted gluzincins, but distinct from that documented for the crystal structure of native LF. Furthermore, spectroscopic studies following the exposure of CoLF to thioglycolic acid (TGA) revealed a sequential mechanism of metal removal from LF, which likely involves the formation of an enzyme: Co{sup 2+}:TGA ternary complex prior to demetallation of the active site. CoLF reported herein constitutes the first spectroscopic probe of LF's active site, which may be utilized in future studies to gain further insight into the enzyme's mechanism and inhibitor interactions.

  9. Atomic-absorption spectrometric determination of cobalt, nickel, and copper in geological materials with matrix masking and chelation-extraction

    USGS Publications Warehouse

    Sanzolone, R.F.; Chao, T.T.; Crenshaw, G.L.

    1979-01-01

    An atomic-absorption spectrometric method is reported for the determination of cobalt, nickel, and copper in a variety of geological materials including iron- and manganese-rich, and calcareous samples. The sample is decomposed with HP-HNO3 and the residue is dissolved in hydrochloric acid. Ammonium fluoride is added to mask iron and 'aluminum. After adjustment to pH 6, cobalt, nickel, and copper are chelated with sodium diethyl-dithiocarbamate and extracted into methyl isobutyl ketone. The sample is set aside for 24 h before analysis to remove interferences from manganese. For a 0.200-g sample, the limits of determination are 5-1000 ppm for Co, Ni, and Cu. As much as 50% Fe, 25% Mn or Ca, 20% Al and 10% Na, K, or Mg in the sample either individually or in various combinations do not interfere. Results obtained on five U.S. Geological Survey rock standards are in general agreement with values reported in the literature. ?? 1979.

  10. Enhancement of direct urea-hydrogen peroxide fuel cell performance by three-dimensional porous nickel-cobalt anode

    NASA Astrophysics Data System (ADS)

    Guo, Fen; Cao, Dianxue; Du, Mengmeng; Ye, Ke; Wang, Guiling; Zhang, Wenping; Gao, Yinyi; Cheng, Kui

    2016-03-01

    A novel three-dimensional (3D) porous nickel-cobalt (Ni-Co) film on nickel foam is successfully prepared and further used as an efficient anode for direct urea-hydrogen peroxide fuel cell (DUHPFC). By varying the cobalt/nickel mole ratios into 0%, 20%, 50%, 80% and 100%, the optimized Ni-Co/Ni foam anode with a ratio of 80% is obtained in terms of the best cell performance among five anodes. Effects of the KOH and urea concentrations, the flow rate and operation temperature on the fuel cell performance are investigated. Results show DUHPFC with the 3D Ni-Co/Ni foam anode exhibits a higher performance than those reported direct urea fuel cells. The cell gives an open circuit voltage of 0.83 V and a peak power density as high as 17.4 and 31.5 mW cm-2 at 20 °C and 70 °C, respectively, when operating on 7.0 mol L-1 KOH and 0.5 mol L-1 urea as the fuel at a flow rate of 15 mL min-1. Besides, when the human urine is directly fed as the fuel, direct urine-hydrogen peroxide fuel cell reaches a maximum power density of 7.5 mW cm-2 with an open circuit voltage of 0.80 V at 20 °C, showing a good application prospect in wastewater treatment.

  11. Global flows of critical metals necessary for low-carbon technologies: the case of neodymium, cobalt, and platinum.

    PubMed

    Nansai, Keisuke; Nakajima, Kenichi; Kagawa, Shigemi; Kondo, Yasushi; Suh, Sangwon; Shigetomi, Yosuke; Oshita, Yuko

    2014-01-01

    This study, encompassing 231 countries and regions, quantifies the global transfer of three critical metals (neodymium, cobalt, and platinum) considered vital for low-carbon technologies by means of material flow analysis (MFA), using trade data (BACI) and the metal contents of trade commodities, resolving the optimization problem to ensure the material balance of the metals within each country and region. The study shows that in 2005 international trade led to global flows of 18.6 kt of neodymium, 154 kt of cobalt, and 402 t of platinum and identifies the main commodities and top 50 bilateral trade links embodying these metals. To explore the issue of consumption efficiency, the flows were characterized according to the technological level of each country or region and divided into three types: green ("efficient use"), yellow ("moderately efficient use"), and red ("inefficient use"). On this basis, the shares of green, yellow, and red flows in the aggregate global flow of Nd were found to be 1.2%, 98%, and 1.2%, respectively. For Co, the respective figures are 53%, 28%, and 19%, and for Pt 15%, 84%, and 0.87%. Furthermore, a simple indicator focusing on the composition of the three colored flows for each commodity was developed to identify trade commodities that should be prioritized for urgent technical improvement to reduce wasteful use of the metals. Based on the indicator, we discuss logical, strategic identification of the responsibilities and roles of the countries involved in the global flows. PMID:24387330

  12. Development of high efficiency 100% aqueous cobalt electrolyte dye-sensitised solar cells.

    PubMed

    Ellis, Hanna; Jiang, Roger; Ye, Sofie; Hagfeldt, Anders; Boschloo, Gerrit

    2016-03-28

    In this study we report the application of three cobalt redox shuttles in 100% aqueous electrolyte dye-sensitised solar cells (DSCs). By using chloride as a counter-ion for cobalt bipyridine, cobalt phenanthroline and cobalt bipyridine pyrazole, the redox shuttles were made water soluble; no surfactant or further treatment was necessary. A simple system of merely the redox shuttles and 1-methylbenzimidazole (MBI) in water as an electrolyte in combination with an organic dye and a mesoporous PEDOT counter electrode was optimised. The optimisation resulted in an average efficiency of 5.5% (record efficiency of 5.7%) at 1 sun. The results of this study present promising routes for further improvements of aqueous cobalt electrolyte DSCs. PMID:26931779

  13. Tailoring the oxidation state of cobalt through halide functionality in sol-gel silica

    PubMed Central

    Olguin, Gianni; Yacou, Christelle; Smart, Simon; Diniz da Costa, João C.

    2013-01-01

    The functionality or oxidation state of cobalt within a silica matrix can be tailored through the use of cationic surfactants and their halide counter ions during the sol-gel synthesis. Simply by adding surfactant we could significantly increase the amount of cobalt existing as Co3O4 within the silica from 44% to 77%, without varying the cobalt precursor concentration. However, once the surfactant to cobalt ratio exceeded 1, further addition resulted in an inhibitory mechanism whereby the altered pyrolysis of the surfactant decreased Co3O4 production. These findings have significant implications for the production of cobalt/silica composites where maximizing the functional Co3O4 phase remains the goal for a broad range of catalytic, sensing and materials applications. PMID:24022785

  14. Structural, morphological, and electrical characteristics of the electrodeposited cobalt oxide electrode for supercapacitor applications

    SciTech Connect

    Kandalkar, Sunil G.; Lee, Hae-Min; Chae, Heeyeop; Kim, Chang-Koo

    2011-01-15

    Cobalt oxide (Co{sub 3}O{sub 4}) thin films were prepared through electrodeposition on copper substrates using an ammonia-complexed cobalt chloride solution. The structural and morphological properties of the film were studied using an X-ray diffractometer and scanning electron microscopy, and the results showed that the electrodeposited cobalt oxide film had a nanocrystalline and porous structure. The electrochemical behavior of the electrodeposited cobalt oxide electrode was evaluated in a KOH solution using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The electrodeposited cobalt oxide electrode exhibited a specific capacitance of 235 F/g at a scan rate of 20 mV/s. The specific energy and the specific power of the electrode were 4.0 Wh/kg and 1.33 kW/kg, respectively.

  15. Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation.

    PubMed

    Spentzos, Ariana Z; Barnes, Charles L; Bernskoetter, Wesley H

    2016-08-15

    The pincer ligand MeN[CH2CH2(P(i)Pr2)]2 ((iPr)PNP) was employed to support a series of cobalt(I) complexes, which were crystallographically characterized. A cobalt monochloride species, ((iPr)PNP)CoCl, served as a precursor for the preparation of several cobalt precatalysts for CO2 hydrogenation, including a cationic dicarbonyl cobalt complex, [((iPr)PNP)Co(CO)2](+). When paired with the Lewis acid lithium triflate, [((iPr)PNP)Co(CO)2](+) affords turnover numbers near 30 000 (at 1000 psi, 45 °C) for CO2-to-formate hydrogenation, which is a notable increase in activity from previously reported homogeneous cobalt catalysts. Though mechanistic information regarding the function of the precatalysts remains limited, multiple experiments suggest the active species is a molecular, homogeneous [((iPr)PNP)Co] complex. PMID:27454669

  16. Effects of cobalt on the microstructure of Udimet 700. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Engel, M. A.

    1982-01-01

    Cobalt, a critical and "strategic" alloying element in many superalloys, was systematically substituted by nickel in experimental alloys Udimet 700 containing 0.1, 4.3, 8.6, 12.8 and the standard 17.0 wt.% cobalt. Electrolytic and chemical extraction techniques, X-ray diffraction, scanning electron and optical microscopy were used for the microstructural studies. The total weight fraction of gamma' was not significantly affected by the cobalt content, although a difference in the size and quantities of the primary and secondary gamma' phases was apparent. The lattice parameters of the gamma' were found to increase with increasing cobalt content while the lattice mismatch between the gamma matrix and gamma' phases decreased. Other significant effects of cobalt on the weight fraction, distribution and formation of the carbide and boride phases as well as the relative stability of the experimental alloys during long-time aging are also discussed.

  17. Consequence of cobalt on structural, optical and dielectric properties in ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Zia, Amir; Ahmed, S.; Shah, N. A.; Anis-ur-Rehman, M.; Khan, E. U.; Basit, M.

    2015-09-01

    The critical role of cobalt dopant in ZnO nanostructures with different cobalt concentrations has been explored on the basis of structural, optical and dielectric mechanisms. X-ray diffraction (XRD) analysis shows that the Co+2 ions replace Zn+2 ions in the ZnO matrix, producing lattice strain. Diffused Reflectance Spectroscopy (DRS) shows a red shift in optical energy band gap with increase in cobalt content, along with the presence of transitions in high spin states due to tetrahedrally coordinated cobalt ions. The dielectric characterization explains the disparity in dynamic dielectric parameters like capacitance, dielectric constant, tangent loss, AC conductivity and impedance as a function of frequency. Capacitance and both static and dynamic dielectric constants found to be decreasing with cobalt addition. The anomaly in these pronounced parameters can address the key problems of the material at higher frequencies device operation.

  18. Effect of cobalt incorporation and lithium enrichment in lithium nickel manganese oxides.

    SciTech Connect

    Deng, H.; Belharouak, I.; Wu, H.; Dambournet, D.; Amine, K.

    2010-05-10

    Candidate cathode materials of cobalt-incorporated and lithium-enriched Li{sub (1+x)}Ni{sub 0.25}Co{sub 0.15}Mn{sub 0.6}O{sub (2.175+x/2)} (x=0.225-0.65) have been prepared by a coprecipitation method and a solid-state reaction. We systematically investigated the effect of both cobalt presence and lithium concentration on the structure, physical properties, and electrochemical behavior of the studied samples. The electrochemical performance of the cobalt-containing compounds showed much less dependence on the variation in the lithium amounts compared to the cobalt-free counterpart. The study demonstrated that even with cobalt incorporation, proper lithium content is the key to desirable cathode materials with nanostructured primary particles that are indispensable to achieve high capacity and high rate capability and, therefore, both improved energy and power densities for lithium-ion batteries.

  19. Comparison of the dietary cobalt intake in three different Australian diets.

    PubMed

    Hokin, Bevan; Adams, Michelle; Ashton, John; Louie, Honway

    2004-01-01

    Differences in the dietary intake of cobalt were assessed for vegans, lacto-ovo-vegetarian and non-vegetarian Australians using food intake logs, and daily or average trend recall over three months. A significant decrease in cobalt intake was observed for the lacto-ovo-vegetarian population compared with the intake in vegans and omnivores. There is no RDI for cobalt, however, the cobalt intake of Australians was similar to that reported in other countries. Microflora above the terminal ileum have been shown to produce significant amounts of biologically available vitamin B12. This study was unable to demonstrate a correlation between elemental cobalt intake and serum vitamin B12 concentrations in humans, as has been shown in vitro. PMID:15331342

  20. Facile fabrication of cobalt oxalate nanostructures with superior specific capacitance and super-long cycling stability

    NASA Astrophysics Data System (ADS)

    Cheng, Guanhua; Si, Conghui; Zhang, Jie; Wang, Ying; Yang, Wanfeng; Dong, Chaoqun; Zhang, Zhonghua

    2016-04-01

    Transition metal oxalate materials have shown huge competitive advantages for applications in supercapacitors. Herein, nanostructured cobalt oxalate supported on cobalt foils has been facilely fabricated by anodization, and could directly serve as additive/binder-free electrodes for supercapacitors. The as-prepared cobalt oxalate electrodes present superior specific capacitance of 1269 F g-1 at the current density of 6 A g-1 in the galvanostatic charge/discharge test. Moreover, the retained capacitance is as high as 87.2% as the current density increases from 6 A g-1 to 30 A g-1. More importantly, the specific capacitance of cobalt oxalate retains 91.9% even after super-long cycling of 100,000 cycles. In addition, an asymmetric supercapacitor assembled with cobalt oxalate (positive electrode) and activated carbon (negative electrode) demonstrates excellent capacitive performance with high energy density and power density.

  1. Gas atomization of cobalt ferrite-phosphate melts

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; O'Handley, R. C.; Kalonji, G.

    1989-01-01

    XRD, Moessbauer spectroscopy, and EDXS have been used to characterize a rapidly-solidified (Co,Fe)3O4 spinel generated in a cobalt-iron-phosphate glass matrix by gas atomization of melts. Of the two compositions tested, that containing 20 mol pct P2O5 exhibited randomly-oriented ferrite crystallization whose growth appears to have been diffusion-controlled. Unlike the ferrite, in which the iron has both tetrahedral and octahedral coordination, the iron in the glassy matrix was primarily of distorted-octahedral coordination. Calculations indicate that the cooling rates obtained with oxide melts vary strongly with droplet size, but less strongly with melt temperature.

  2. Size dependence of magnetorheological properties of cobalt ferrite ferrofluid

    SciTech Connect

    Radhika, B.; Sahoo, Rasmita; Srinath, S.

    2015-06-24

    Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ∼30nm and ∼48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.

  3. Mapping the magnetic and crystal structure in cobalt nanowires

    SciTech Connect

    Cantu-Valle, Jesus; Betancourt, Israel; Sanchez, John E.; Ruiz-Zepeda, Francisco; Mendoza-Santoyo, Fernando; Ponce, Arturo; Maqableh, Mazin M.; Stadler, Bethanie J. H.

    2015-07-14

    Using off-axis electron holography under Lorentz microscopy conditions to experimentally determine the magnetization distribution in individual cobalt (Co) nanowires, and scanning precession-electron diffraction to obtain their crystalline orientation phase map, allowed us to directly visualize with high accuracy the effect of crystallographic texture on the magnetization of nanowires. The influence of grain boundaries and disorientations on the magnetic structure is correlated on the basis of micromagnetic analysis in order to establish the detailed relationship between magnetic and crystalline structure. This approach demonstrates the applicability of the method employed and provides further understanding on the effect of crystalline structure on magnetic properties at the nanometric scale.

  4. Polyamide preparation with pentaamine cobalt (III) complex catalyst

    SciTech Connect

    Wu, M.Y.M.; Ball, L.E.; Coffey, G.P.

    1987-11-17

    A process is described for preparing a polyamide containing amide groups as integral parts of the main polymer chain comprising polymerizing a polyamide forming system, chosen from (1) an alpha, beta-unsaturated carboxylic acid and ammonia, (2) an ammonium salt of an alpha, beta unsaturated carboxylic acid, (3) an alpha, beta-unsaturated nitrile and water, (4) an alpha, beta-unsaturated amine and ammonia, (5) or a beta-amino propionic acid or its alkyl derivatives, in contact with a catalyst comprising a pentaamine cobalt (III) complex.

  5. Cobalt dicarbollide containing polymer resins for cesium and strontium uptake

    SciTech Connect

    Steckle, W.P. Jr.; Duke, J.R. Jr.; Jorgensen, B.S.

    1994-04-01

    Cobalt(III) dicarbollide [(C{sub 2}B{sub 9}H{sub 11}){sub 2}Co]{sup {minus}} (CB{sub 2}) is being investigated for Cs and Sr extraction from nuclear waste. Because organic solvents should be avoided, bonding of CB{sub 2} to resins were investigated. CB{sub 2} was successfully covalently bonded to polystyrene and polybenzimidazole resins. Tetrahydrofuran was the most efficient solvent for grafting. Analysis is being performed, and separation coefficients are also being determined. 3 figs, 8 refs.

  6. Effect of the capping agents on cobalt nanoparticles

    NASA Astrophysics Data System (ADS)

    Sciortino, L.; Longo, A.; Giannici, F.; Martorana, A.

    2009-11-01

    The achievement of high information density and fast recording rate in memory devices crucially depends on the structure of magnetic domains. In this paper cobalt nanoparticles are synthesised using two capping agents (TOA, ODA) and two different preparation routes: thermal decomposition (TD) and Solvated Metal Atom Dispersion (SMAD). The interaction of capping agents with free metal clusters and their influence on Co nanoparticles size, atomic structure and oxidation state is investigated by means of X-ray diffraction and X-ray absorption spectroscopy.

  7. Ferric and cobaltous hydroacid complexes for forward osmosis (FO) processes.

    PubMed

    Ge, Qingchun; Fu, Fengjiang; Chung, Tai-Shung

    2014-07-01

    Cupric and ferric hydroacid complexes have proven their advantages as draw solutes in forward osmosis in terms of high water fluxes, negligible reverse solute fluxes and easy recovery (Ge and Chung, 2013. Hydroacid complexes: A new class of draw solutes to promote forward osmosis (FO) processes. Chemical Communications 49, 8471-8473.). In this study, cobaltous hydroacid complexes were explored as draw solutes and compared with the ferric hydroacid complex to study the factors influencing their FO performance. The solutions of the cobaltous complexes produce high osmotic pressures due to the presence of abundant hydrophilic groups. These solutes are able to dissociate and form a multi-charged anion and Na(+) cations in water. In addition, these complexes have expanded structures which lead to negligible reverse solute fluxes and provide relatively easy approaches in regeneration. These characteristics make the newly synthesized cobaltous complexes appropriate as draw solutes. The FO performance of the cobaltous and ferric-citric acid (Fe-CA) complexes were evaluated respectively through cellulose acetate membranes, thin-film composite membranes fabricated on polyethersulfone supports (referred as TFC-PES), and polybenzimidazole and PES dual-layer (referred as PBI/PES) hollow fiber membranes. Under the conditions of DI water as the feed and facing the support layer of TFC-PES FO membranes (PRO mode), draw solutions at 2.0 M produced relatively high water fluxes of 39-48 LMH (L m(-2) hr(-1)) with negligible reverse solute fluxes. A water flux of 17.4 LMH was achieved when model seawater of 3.5 wt.% NaCl replaced DI water as the feed and 2.0 M Fe-CA as the draw solution under the same conditions. The performance of these hydroacid complexes surpasses those of the synthetic draw solutes developed in recent years. This observation, along with the relatively easy regeneration, makes these complexes very promising as a novel class of draw solutes. PMID:24768702

  8. Hydrogenation of carboxylic acids with a homogeneous cobalt catalyst.

    PubMed

    Korstanje, Ties J; van der Vlugt, Jarl Ivar; Elsevier, Cornelis J; de Bruin, Bas

    2015-10-16

    The reduction of esters and carboxylic acids to alcohols is a highly relevant conversion for the pharmaceutical and fine-chemical industries and for biomass conversion. It is commonly performed using stoichiometric reagents, and the catalytic hydrogenation of the acids previously required precious metals. Here we report the homogeneously catalyzed hydrogenation of carboxylic acids to alcohols using earth-abundant cobalt. This system, which pairs Co(BF4)2·6H2O with a tridentate phosphine ligand, can reduce a wide range of esters and carboxylic acids under relatively mild conditions (100°C, 80 bar H2) and reaches turnover numbers of up to 8000. PMID:26472903

  9. Low-Pressure Cobalt-Catalyzed Enantioselective Hydrovinylation of Vinylarenes.

    PubMed

    Movahhed, Sohajl; Westphal, Julia; Dindaroğlu, Mehmet; Falk, Anna; Schmalz, Hans-Günther

    2016-05-23

    An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2 CoCl2 ] complexes are employed that are activated in situ with Et2 AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99 % ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2 , CN, and CO2 R, are tolerated. PMID:26998912

  10. Hot corrosion of S-57, 1 cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1977-01-01

    A cobalt base alloy, S-57, was hot corrosion tested in Mach 0.3 burner rig combustion gases at maximum alloy temperatures of 900 and 1000 C. Various salt concentrations were injected into the burner: 0.5, 2, 5, and 10 ppm synthetic sea salt and 4 ppm sodium sulfate (Na2SO4). S-57 underwent accelerated corrosion only under the most severe test conditions, for example, 4 ppm Na2SO4 at 900 C. The process of the accelerated corrosion was primarily sulfidation.

  11. Size dependence of magnetorheological properties of cobalt ferrite ferrofluid

    NASA Astrophysics Data System (ADS)

    Radhika, B.; Sahoo, Rasmita; Srinath, S.

    2015-06-01

    Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ˜30nm and ˜48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.

  12. Mapping the magnetic and crystal structure in cobalt nanowires

    PubMed Central

    Cantu-Valle, Jesus; Betancourt, Israel; Sanchez, John E.; Ruiz-Zepeda, Francisco; Maqableh, Mazin M.; Mendoza-Santoyo, Fernando; Stadler, Bethanie J. H.; Ponce, Arturo

    2015-01-01

    Using off-axis electron holography under Lorentz microscopy conditions to experimentally determine the magnetization distribution in individual cobalt (Co) nanowires, and scanning precession-electron diffraction to obtain their crystalline orientation phase map, allowed us to directly visualize with high accuracy the effect of crystallographic texture on the magnetization of nanowires. The influence of grain boundaries and disorientations on the magnetic structure is correlated on the basis of micromagnetic analysis in order to establish the detailed relationship between magnetic and crystalline structure. This approach demonstrates the applicability of the method employed and provides further understanding on the effect of crystalline structure on magnetic properties at the nanometric scale. PMID:26221057

  13. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  14. Dosimetry under pencil eye shields for cobalt-60 radiation

    SciTech Connect

    Chenery, S.G.; Leung, P.M.K.

    1981-05-01

    The use of pencil eye shields to reduce the dose to the anterior chamber of the eye during radiotherapy with Cobalt-60 beams has been evaluated. It was found that the optimum shield placement is about 1 cm from the surface. This keeps the size of the penumbra and the effect of electron contamination at a minimum. The dose under such shields is mainly produced by the transmission through the shield and the scattered radiation both from within the phantom and from the collimator. While the scattered component is a function of the beam size and otherwise cannot be altered, the transmission can easily be reduced to a negligible level.

  15. TECHNOLOGY DEVELOPMENT FOR IRON AND COBALT FISCHER-TROPSCH CATALYSTS

    SciTech Connect

    Burtron H. Davis

    1999-01-30

    The effects of copper on Fischer-Tropsch activity, selectivity and water-gas shift activity were studied over a wide range of syngas conversion. Three catalyst compositions were prepared for this study: (a) 100Fe/4.6Si/1.4K, (b) 100Fe/4.6Si/0.10Cu/1.4K and (c) 100Fe/4.6Si/2.0Cu/1.4K. The results are reported in Task 2. The literature review for cobalt catalysts is approximately 90% complete. Due to the size of the document, it has been submitted as a separate report labeled Task 6.

  16. Thermal evolution of cobalt deposits on Co3O4(111): atomically dispersed cobalt, two-dimensional CoO islands, and metallic Co nanoparticles.

    PubMed

    Mehl, S; Ferstl, P; Schuler, M; Toghan, A; Brummel, O; Hammer, L; Schneider, M A; Libuda, J

    2015-09-28

    Cobalt oxide nanomaterials show high activity in several catalytic reactions thereby offering the potential to replace noble metals in some applications. We have developed a well-defined model system for partially reduced cobalt oxide materials aiming at a molecular level understanding of cobalt-oxide-based catalysis. Starting from a well-ordered Co3O4(111) film on Ir(100), we modified the surface by deposition of metallic cobalt. Growth, structure, and adsorption properties of the cobalt-modified surface were investigated by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and infrared reflection absorption spectroscopy (IRAS) using CO as a probe molecule. The deposition of a submonolayer of cobalt at 300 K leads to the formation of atomically dispersed cobalt ions distorting the surface layer of the Co3O4 film. Upon annealing to 500 K the Co ions are incorporated into the surface layer forming ordered two-dimensional CoO islands on the Co3O4 grains. At 700 K, Co ions diffuse from the CoO islands into the bulk and the ordered Co3O4(111) surface is restored. Deposition of larger amounts of Co at 300 K leads to formation of metallic Co aggregates on the dispersed cobalt phase. The metallic particles sinter at 500 K and diffuse into the bulk at 700 K. Depending on the degree of bulk reduction, extended Co3O4 grains switch to the CoO(111) structure. All above structures show characteristic CO adsorption behavior and can therefore be identified by IR spectroscopy of adsorbed CO. PMID:26299410

  17. Cobalt Oxide Nanoparticles: Behavior towards Intact and Impaired Human Skin and Keratinocytes Toxicity.

    PubMed

    Mauro, Marcella; Crosera, Matteo; Pelin, Marco; Florio, Chiara; Bellomo, Francesca; Adami, Gianpiero; Apostoli, Piero; De Palma, Giuseppe; Bovenzi, Massimo; Campanini, Marco; Filon, Francesca Larese

    2015-07-01

    Skin absorption and toxicity on keratinocytes of cobalt oxide nanoparticles (Co3O4NPs) have been investigated. Co3O4NPs are commonly used in industrial products and biomedicine. There is evidence that these nanoparticles can cause membrane damage and genotoxicity in vitro, but no data are available on their skin absorption and cytotoxicity on keratinocytes. Two independent 24 h in vitro experiments were performed using Franz diffusion cells, using intact (experiment 1) and needle-abraded human skin (experiment 2). Co3O4NPs at a concentration of 1000 mg/L in physiological solution were used as donor phase. Cobalt content was evaluated by Inductively Coupled-Mass Spectroscopy. Co permeation through the skin was demonstrated after 24 h only when damaged skin protocol was used (57 ± 38 ng·cm⁻²), while no significant differences were shown between blank cells (0.92 ± 0.03 ng cm⁻²) and those with intact skin (1.08 ± 0.20 ng·cm⁻²). To further investigate Co3O4NPs toxicity, human-derived HaCaT keratinocytes were exposed to Co3O4NPs and cytotoxicity evaluated by MTT, Alamarblue and propidium iodide (PI) uptake assays. The results indicate that a long exposure time (i.e., seven days) was necessary to induce a concentration-dependent cell viability reduction (EC50 values: 1.3 × 10-4 M, 95% CL = 0.8-1.9 × 10⁻⁴ M, MTT essay; 3.7 × 10⁻⁵ M, 95% CI = 2.2-6.1 × 10⁻⁵ M, AlamarBlue assay) that seems to be associated to necrotic events (EC50 value: 1.3 × 10⁻⁴ M, 95% CL = 0.9-1.9 × 10⁻⁴ M, PI assay). This study demonstrated that Co3O4NPs can penetrate only damaged skin and is cytotoxic for HaCat cells after long term exposure. PMID:26193294

  18. Cobalt Oxide Nanoparticles: Behavior towards Intact and Impaired Human Skin and Keratinocytes Toxicity

    PubMed Central

    Mauro, Marcella; Crosera, Matteo; Pelin, Marco; Florio, Chiara; Bellomo, Francesca; Adami, Gianpiero; Apostoli, Piero; De Palma, Giuseppe; Bovenzi, Massimo; Campanini, Marco; Larese Filon, Francesca

    2015-01-01

    Skin absorption and toxicity on keratinocytes of cobalt oxide nanoparticles (Co3O4NPs) have been investigated. Co3O4NPs are commonly used in industrial products and biomedicine. There is evidence that these nanoparticles can cause membrane damage and genotoxicity in vitro, but no data are available on their skin absorption and cytotoxicity on keratinocytes. Two independent 24 h in vitro experiments were performed using Franz diffusion cells, using intact (experiment 1) and needle-abraded human skin (experiment 2). Co3O4NPs at a concentration of 1000 mg/L in physiological solution were used as donor phase. Cobalt content was evaluated by Inductively Coupled–Mass Spectroscopy. Co permeation through the skin was demonstrated after 24 h only when damaged skin protocol was used (57 ± 38 ng·cm−2), while no significant differences were shown between blank cells (0.92 ± 0.03 ng cm−2) and those with intact skin (1.08 ± 0.20 ng·cm−2). To further investigate Co3O4NPs toxicity, human-derived HaCaT keratinocytes were exposed to Co3O4NPs and cytotoxicity evaluated by MTT, Alamarblue® and propidium iodide (PI) uptake assays. The results indicate that a long exposure time (i.e., seven days) was necessary to induce a concentration-dependent cell viability reduction (EC50 values: 1.3 × 10−4 M, 95% CL = 0.8–1.9 × 10−4 M, MTT essay; 3.7 × 10−5 M, 95% CI = 2.2–6.1 × 10−5 M, AlamarBlue® assay) that seems to be associated to necrotic events (EC50 value: 1.3 × 10−4 M, 95% CL = 0.9–1.9 × 10−4 M, PI assay). This study demonstrated that Co3O4NPs can penetrate only damaged skin and is cytotoxic for HaCat cells after long term exposure. PMID:26193294

  19. Anchored thiol smectite clay-kinetic and thermodynamic studies of divalent copper and cobalt adsorption

    SciTech Connect

    Guerra, Denis Lima Airoldi, Claudio

    2008-09-15

    A natural smectite clay sample from Serra de Maicuru, Para State, Brazil, had aluminum and zirconium polyoxycations inserted within the interlayer space. The precursor and pillarized smectites were organofunctionalized with the silyating agent 3-mercaptopropyltrimethoxysilane. The basal spacing of 1.47 nm for natural clay increased to 2.58 and 2.63 nm, for pillared aluminum, S{sub Al/SH}, and zirconium, S{sub Zr/SH}, and increases in the surface area from 44 to 583 and 585 m{sup 2} g{sup -1}, respectively. These chemically immobilized clay samples adsorb divalent copper and cobalt cations from aqueous solutions of pH 5.0 at 298{+-}1 K. The Langmuir, Redlich-Peterson and Toth adsorption isotherm models have been applied to fit the experimental data with a nonlinear approach. From the cation/basic center interactions for each smectite at the solid-liquid interface, by using van't Hoff methodology, the equilibrium constant and exothermic thermal effects were calculated. By considering the net interactive number of moles for each cation and the equilibrium constant, the enthalpy, {delta}{sub int}H{sup 0} (-9.2{+-}0.2 to -10.2{+-}0.2 kJ mol{sup -1}) and negative Gibbs free energy, {delta}{sub int}G{sup 0} (-23.9{+-}0.1 to -28.7{+-}0.1 kJ mol{sup -1}) were calculated. These values enabled the positive entropy, {delta}{sub int}S{sup 0} (51.3{+-}0.3 to 55.0{+-}0.3 JK{sup -1} mol{sup -1}) determination. The cation-sulfur interactive process is spontaneous in nature, reflecting the favorable enthalpic and entropic results. The kinetics of adsorption demonstrated that the fit is in agreement with a second-order model reaction with rate constant k{sub 2}, varying from 4.8x10{sup -2} to 15.0x10{sup -2} and 3.9x10{sup -2} to 12.2x10{sup -2} mmol{sup -1} min{sup -1} for copper and cobalt, respectively. - Graphical abstract: A natural smectite clay sample from Serra de Maicuru, Para State, Brazil, had aluminum and zirconium polyoxycations inserted within the interlayer space. The

  20. Molecular mechanisms of cobalt-catalyzed hydrogen evolution

    PubMed Central

    Marinescu, Smaranda C.; Winkler, Jay R.; Gray, Harry B.

    2012-01-01

    Several cobalt complexes catalyze the evolution of hydrogen from acidic solutions, both homogeneously and at electrodes. The detailed molecular mechanisms of these transformations remain unresolved, largely owing to the fact that key reactive intermediates have eluded detection. One method of stabilizing reactive intermediates involves minimizing the overall reaction free-energy change. Here, we report a new cobalt(I) complex that reacts with tosylic acid to evolve hydrogen with a driving force of just 30 meV/Co. Protonation of CoI produces a transient CoIII-H complex that was characterized by nuclear magnetic resonance spectroscopy. The CoIII-H intermediate decays by second-order kinetics with an inverse dependence on acid concentration. Analysis of the kinetics suggests that CoIII-H produces hydrogen by two competing pathways: a slower homolytic route involving two CoIII-H species and a dominant heterolytic channel in which a highly reactive CoII-H transient is generated by CoI reduction of CoIII-H. PMID:22949704

  1. Cobalt silicate hierarchical hollow spheres for lithium-ion batteries.

    PubMed

    Yang, Jun; Guo, Yuanyuan; Zhang, Yufei; Sun, Chencheng; Yan, Qingyu; Dong, Xiaochen

    2016-09-01

    In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g(-1) at 100 mA g(-1)), a cycling durability (specific capacity of 791.4 mAh g(-1) after 100 cycles at 100 mA g(-1)), and a good rate capability (specific capacity of 349.4 mAh g(-1) at 10 A g(-1)). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes. PMID:27479691

  2. Lithium cobalt oxide thin film and its electrochromism

    NASA Astrophysics Data System (ADS)

    Wei, Guang; Haas, Terry E.; Goldner, Ronald B.

    1989-06-01

    Thin films of lithium cobalt oxide have been prepared by RF-sputtering from powdered LiCoO2. These films permit reversible electrolytic removal of lithium ions upon application of an anodic voltage in a propylene carbonate-lithium perchlorate electrolyte, the films changing in color from a pale amber transparent state to a dark brown. A polycrystalline columnar film structure was revealed with SEM and TEM. X ray examination of the films suggests that the layered rhombohedral LiCoO2 structure is the major crystalline phase present. Oxidation-reduction titration and atomic absorption were used for the determination of the film stoichiometry. The results show that the as deposited-films on glass slides are lithium deficient (relative to the starting material) and show a high average cobalt oxidation state near +3.5. The measurements of dc conductivity suggest a band to band conduction at high temperature (300 to 430 K) and hopping conduction in localized states at low temperature (4 to 270 K). The thermoelectric power data show that the films behave as p-type semiconductors. Transmission and reflectance measurements from 400 nm to 2500 nm show significant near-IR reflectivity.

  3. Oriented attachment explains cobalt ferrite nanoparticle growth in bioinspired syntheses.

    PubMed

    Wolff, Annalena; Hetaba, Walid; Wißbrock, Marco; Löffler, Stefan; Mill, Nadine; Eckstädt, Katrin; Dreyer, Axel; Ennen, Inga; Sewald, Norbert; Schattschneider, Peter; Hütten, Andreas

    2014-01-01

    Oriented attachment has created a great debate about the description of crystal growth throughout the last decade. This aggregation-based model has successfully described biomineralization processes as well as forms of inorganic crystal growth, which could not be explained by classical crystal growth theory. Understanding the nanoparticle growth is essential since physical properties, such as the magnetic behavior, are highly dependent on the microstructure, morphology and composition of the inorganic crystals. In this work, the underlying nanoparticle growth of cobalt ferrite nanoparticles in a bioinspired synthesis was studied. Bioinspired syntheses have sparked great interest in recent years due to their ability to influence and alter inorganic crystal growth and therefore tailor properties of nanoparticles. In this synthesis, a short synthetic version of the protein MMS6, involved in nanoparticle formation within magnetotactic bacteria, was used to alter the growth of cobalt ferrite. We demonstrate that the bioinspired nanoparticle growth can be described by the oriented attachment model. The intermediate stages proposed in the theoretical model, including primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron diffraction measurements. The change of particle diameter with time agrees with the recently proposed kinetic model for oriented attachment. PMID:24605288

  4. Tuning of magnetic properties in cobalt ferrite nanocrystals

    SciTech Connect

    Cedeno-Mattei, Y.; Roman, F.; Perales-Perez, O.; Tomar, M. S.; Voyles, P. M.; Stratton, W. G.

    2008-04-01

    Cobalt ferrite (CoFe{sub 2}O{sub 4}) possesses excellent chemical stability, good mechanical hardness, and a large positive first order crystalline anisotropy constant, making it a promising candidate for magneto-optical recording media. In addition to precise control of the composition and structure of CoFe{sub 2}O{sub 4}, its practical application will require the capability to control particle size at the nanoscale. The results of a synthesis approach in which size control is achieved by modifying the oversaturation conditions during ferrite formation in water through a modified coprecipitation approach are reported. X-ray diffraction, transmission electron microscopy (TEM) diffraction, and TEM energy-dispersive x-ray spectroscopy analyses confirmed the formation of the nanoscale cobalt ferrite. M-H measurements verified the strong influence of synthesis conditions on crystal size and hence, on the magnetic properties of ferrite nanocrystals. The room-temperature coercivity values increased from 460 up to 4626 Oe under optimum synthesis conditions determined from a 2{sup 3} factorial design.

  5. Cobalt Nanoparticle Inks for Printed High Frequency Applications on Polycarbonate

    NASA Astrophysics Data System (ADS)

    Nelo, Mikko; Myllymäki, Sami; Juuti, Jari; Uusimäki, Antti; Jantunen, Heli

    2015-12-01

    In this work the high frequency properties of low curing temperature cobalt nanoparticle inks printed on polycarbonate substrates were investigated. The inks consisted of 30-70 vol.% metallic cobalt nanoparticles and poly (methylene methacrylate) polymer, having excellent adhesion on polycarbonate and a curing temperature of 110°C. The influence of binder material content on the electromagnetic properties of the ink was investigated using the shorted microstrip transmission-line perturbation method. Changes in mechanical properties were evaluated with adhesion tests using the pull-out strength test and the ASTM D 3359-B cross-hatch tape peel test. The microstructure of the printed patterns was investigated with field emission scanning electron microscopy (FESEM). The inks remained mechanically durable with metal contents up to 60 vol.%, achieving pull-off strength of up to 5.2 MPa and the highest marks in adhesion of the tape peel test. The inks obtained a relative permeability of 1.5-3 in the 45 MHz-10 GHz band with a magnetic loss tangent of 0.01-0.06. The developed inks can be utilized in various printed electronics applications such as antenna miniaturization, antenna substrates and magnetic sensors or sensing.

  6. Mechanical strength of laser-welded cobalt-chromium alloy.

    PubMed

    Baba, N; Watanabe, I; Liu, J; Atsuta, M

    2004-05-15

    The purpose of this study was to investigate the effect of the output energy of laser welding and welding methods on the joint strength of cobalt-chromium (Co-Cr) alloy. Two types of cast Co-Cr plates were prepared, and transverse sections were made at the center of the plate. The cut surfaces were butted against one another, and the joints welded with a laser-welding machine at several levels of output energy with the use of two methods. The fracture force required to break specimens was determined by means of tensile testing. For the 0.5-mm-thick specimens, the force required to break the 0.5-mm laser-welded specimens at currents of 270 and 300 A was not statistically different (p > 0.05) from the results for the nonwelded control specimens. The force required to break the 1.0-mm specimens double-welded at a current of 270 A was the highest value among the 1.0-mm laser-welded specimens. The results suggested that laser welding under the appropriate conditions improved the joint strength of cobalt- chromium alloy. PMID:15116400

  7. Cobalt silicate hierarchical hollow spheres for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Guo, Yuanyuan; Zhang, Yufei; Sun, Chencheng; Yan, Qingyu; Dong, Xiaochen

    2016-09-01

    In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g‑1 at 100 mA g‑1), a cycling durability (specific capacity of 791.4 mAh g‑1 after 100 cycles at 100 mA g‑1), and a good rate capability (specific capacity of 349.4 mAh g‑1 at 10 A g‑1). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes.

  8. Size effects and Hall-Petch relation in polycrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Fleurier, Gwendoline; Hug, Eric; Martinez, Mayerling; Dubos, Pierre-Antoine; Keller, Clément

    2015-02-01

    The mechanical behaviour of polycrystalline hexagonal close-packed cobalt was investigated over a large range of grain size d in order to examine the occurrence of size effects. Crystallographic texture and amount of face centred cubic allotropic phase were maintained unchanged thanks to appropriate heat treatment procedures. The Hall-Petch (HP) relation exhibits two distinct behaviours from the very beginning of plastic strain levels. The conventional HP law is fulfilled for a number of grains across the thickness t higher than a critical value (t/d)c = 14. For t/d lower than (t/d)c, a multicrystalline regime is evidenced highlighting a strong reduction in flow stress. The high value of (t/d)c is related to the low-stacking fault energy of cobalt in the basal plane. The size effect is predominant in the first work hardening stage where slip mechanisms and stacking faults predominate. In the second stage, driven by mechanical twinning processes, this effect is less sensitive. Finally, the size effect could also affect the end of the elastic stage, in link with nonlinear elasticity mechanisms.

  9. Impact of wastewater reuse on cobalt status in Egyptian environment.

    PubMed

    Abdel-Sabour, M F

    2003-05-01

    Cobalt is used in the manufacture of alloys, catalysts in the petroleum industry, catalytic converters, and paint pigments. Thus the potential for Co releases into the environment is highly increased. Use of waste sludges and sewage effluent to fertilize and irrigate soils has also increased soil Co concentrations. Total cobalt contents of alluvial delta soil of Egypt show considerable variation ranging from 13.1 to 64.7 ppm. The impact of either wastewater irrigation or industrial activities on soil total Co was obvious due to accumulation of organic matter and solid waste in the surface soil samples. Food crops and vegetables should not be grown on soil highly contaminated by Co. It is noteworthy that the delayed neutron activation analysis (DNAA) technique could be used successfully for total Co determination due to its high sensitivity. It is quit clearly that dust samples of Cairo City contains higher Co level, as compared to Suez Canal Region (Ismailia, Port Said an El-Sues cities). The high values in Cairo City may be due to the existence of industries around the city and the intensive traffic. To minimize Co environmental hazards, waste effluents should be treated on site. Thus, levels of potentially toxic Co needs to be continuously monitored and should be removed during several treatment processes before the disposal of these wastes. PMID:12938992

  10. Synthesis and characterization of mononuclear, pseudotetrahedral cobalt(III) compounds.

    PubMed

    Kozhukh, Julia; Minier, Mikael A; Lippard, Stephen J

    2015-01-20

    The preparation and characterization of two mononuclear cobalt(III) tropocoronand complexes, [Co(TC-5,5)](BF4) and [Co(TC-6,6)](BPh4), are reported. The cobalt(III) centers exist in rare pseudotetrahedral conformations, with twist angles of 65° and 74° for the [Co(TC-5,5](+) and [Co(TC-6,6)](+) species, respectively. Structural and electrochemical characteristics are compared with those of newly synthesized [Ga(TC-5,5)](GaCl4) and [Ga(TC-6,6)](GaCl4) analogues. The spin state of the pseudotetrahedral [Co(TC-6,6)](BPh4) compound was determined to be S = 2, a change in spin state from the value of S = 1 that occurs in the square-planar and distorted square-planar complexes, [Co(TC-3,3)](X) (X = BPh4, BAr'4) and [Co(TC-4,4)](BPh4), respectively. PMID:25531129

  11. Synthesis and Characterization of Mononuclear, Pseudotetrahedral Cobalt(III) Compounds

    PubMed Central

    2015-01-01

    The preparation and characterization of two mononuclear cobalt(III) tropocoronand complexes, [Co(TC-5,5)](BF4) and [Co(TC-6,6)](BPh4), are reported. The cobalt(III) centers exist in rare pseudotetrahedral conformations, with twist angles of 65° and 74° for the [Co(TC-5,5]+ and [Co(TC-6,6)]+ species, respectively. Structural and electrochemical characteristics are compared with those of newly synthesized [Ga(TC-5,5)](GaCl4) and [Ga(TC-6,6)](GaCl4) analogues. The spin state of the pseudotetrahedral [Co(TC-6,6)](BPh4) compound was determined to be S = 2, a change in spin state from the value of S = 1 that occurs in the square-planar and distorted square-planar complexes, [Co(TC-3,3)](X) (X = BPh4, BAr′4) and [Co(TC-4,4)](BPh4), respectively. PMID:25531129

  12. Magnetic resonance imaging for adaptive cobalt tomotherapy: A proposal

    PubMed Central

    Kron, Tomas; Eyles, David; John, Schreiner L; Battista, Jerry

    2006-01-01

    Magnetic resonance imaging (MRI) provides excellent soft tissue contrast for oncology applications. We propose to combine a MRI scanner with a helical tomotherapy (HT) system to enable daily target imaging for improved conformal radiation dose delivery to a patient. HT uses an intensity-modulated fan-beam that revolves around a patient, while the patient slowly advances through the plane of rotation, yielding a helical beam trajectory. Since the use of a linear accelerator to produce radiation may be incompatible with the pulsed radiofrequency and the high and pulsed magnetic fields required for MRI, it is proposed that a radioactive Cobalt-60 (60Co) source be used instead to provide the radiation. An open low field (0.25 T) MRI system is proposed where the tomotherapy ring gantry is located between two sets of Helmholtz coils that can generate a sufficiently homogenous main magnetic field. It is shown that the two major challenges with the design, namely acceptable radiation dose rate (and therefore treatment duration) and moving parts in strong magnetic field, can be addressed. The high dose rate desired for helical tomotherapy delivery can be achieved using two radiation sources of 220TBq (6000Ci) each on a ring gantry with a source to axis-of-rotation distance of 75 cm. In addition to this, a dual row multi-leaf collimator (MLC) system with 15 mm leaf width at isocentre and relatively large fan beam widths between 15 and 30 mm per row shall be employed. In this configuration, the unit would be well-suited for most pelvic radiotherapy applications where the soft tissue contrast of MRI will be particularly beneficial. Non-magnetic MRI compatible materials must be used for the rotating gantry. Tungsten, which is non-magnetic, can be used for primary collimation of the fan-beam as well as for the MLC, which allows intensity modulated radiation delivery. We propose to employ a low magnetic Cobalt compound, sycoporite (CoS) for the Cobalt source material itself

  13. Celebrating 50 Years!

    ERIC Educational Resources Information Center

    Kristjansdottir, Anna

    2011-01-01

    The author congratulates members of the Association of Teachers of Mathematics (ATM) on celebrating the 50th anniversary of their annual conference. These conferences have kept the spirit alive from the early years, especially the engagement in investigative, collaborative, and reasoning activities. In the 50th year as an association, the author…

  14. Cobalt in ferromanganese crusts as a monitor of hydrothermal discharge on the Pacific sea floor

    USGS Publications Warehouse

    Manheim, F. T.; Lane-Bostwick, C. M.

    1988-01-01

    Ferromanganese oxide crusts, which accumulate on unsedimented surfaces in the open ocean1-6, derive most of their metal content from dissolved and particulate matter in ambient bottom water7,8, in proportions modified by the variable scavenging efficiency of the oxide phase for susceptible ions9. They differ in this respect from abyssal nodules, much of whose metals are remobilized from host sediments. Here we present maps of cobalt concentration and inferred accumulation rate of ferromanganese crusts from the Pacific Ocean. We propose that depletion of cobalt in Pacific crusts measures the location and intensity of submarine hydrothermal discharge. Use of the 'cobalt chronometer', an algorithm inversely relating cobalt content and crust growth rate, permits mapping of the accumulation rate of ferromanganese crusts with only indirect recourse to radioactivity-based dating methods. These maps show that crusts in hydrothermal areas grow from two to more than four orders of magnitude faster than in the Central Pacific Ocean. Cobalt-enriched crusts are found where water masses are most isolated from continental-coastal and hydrothermal sources of metals, now and in the past. This relationship can resolve the problem of cobalt enrichment in crusts without recourse to hypotheses invoking special cobalt sources or enrichment mechanisms. ?? 1988 Nature Publishing Group.

  15. Thermal-fatigue and oxidation resistance of cobalt-modified Udimet 700 alloy

    NASA Technical Reports Server (NTRS)

    Bizon, P. T.; Barrow, B. J.

    1986-01-01

    Comparative thermal-fatigue and oxidation resistances of cobalt-modified wrought Udimet 700 alloy (obtained by reducing the cobalt level by direct substitution of nickel) were determined from fluidized-bed tests. Bed temperatures were 1010 and 288 C (1850 and 550 C) for the first 5500 symmetrical 6-min cycles. From cycle 5501 to the 14000-cycle limit of testing, the heating bed temperature was increased to 1050 C (1922 F). Cobalt levels between 0 and 17 wt% were studied in both the bare and NiCrAlY overlay coated conditions. A cobalt level of about 8 wt% gave the best thermal-fatigue life. The conventional alloy specification is for 18.5% cobalt, and hence, a factor of 2 in savings of cobalt could be achieved by using the modified alloy. After 13500 cycles, all bare cobalt-modified alloys lost 10 to 13 percent of their initial weight. Application of the NiCrAlY overlay coating resulted in weight losses of 1/20 to 1/100 of that of the corresponding bare alloy.

  16. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation

    PubMed Central

    Bazylewski, Paul F.; Nguyen, Van Luan; Bauer, Robert P.C.; Hunt, Adrian H.; McDermott, Eamon J. G.; Leedahl, Brett D.; Kukharenko, Andrey I.; Cholakh, Seif O.; Kurmaev, Ernst Z.; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-01-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications. PMID:26486966

  17. Micronucleus test and erythropoiesis: effect of cobalt on the induction of micronuclei by mutagens.

    PubMed

    Suzuki, Y; Shimizu, H; Nagae, Y; Fukumoto, M; Okonogi, H; Kadokura, M

    1993-01-01

    The micronucleus test is used widely as an in vivo short-term assay for potential carcinogens. In the present study, results of the micronucleus test were affected by cobalt dichloride pretreatment. Cobalt dichloride was used to induce erythropoietin, a growth factor for erythropoiesis. The increase in mutagen-induced micronucleus response following cobalt pretreatment, therefore, may have been due to a change in the rate of erythropoiesis. The greatest interaction between cobalt pretreatment and mutagen treatment for the induction of micronucleated polychromatic erythrocytes (MPCE) occurred when mice were injected with 1,1-dimethylhydrazine (DMH) 12-24 hr after pretreatment with cobalt dichloride and killed 30 hr later. Increased sensitivity of the micronucleus test was attributable to the administration of mutagen during the differentiation and multiplication of erythroblast, which is presumed to have been accelerated by pretreatment with cobalt dichloride. An increased induction of MPCE in the bone marrow by two chemicals--benzo(a)pyrene, 2-naphthylamine--was also observed following pretreatment with cobalt dichloride. PMID:8359151

  18. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation

    NASA Astrophysics Data System (ADS)

    Bazylewski, Paul F.; Nguyen, Van Luan; Bauer, Robert P. C.; Hunt, Adrian H.; McDermott, Eamon J. G.; Leedahl, Brett D.; Kukharenko, Andrey I.; Cholakh, Seif O.; Kurmaev, Ernst Z.; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-10-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications.

  19. Mobile Phones: Potential Sources of Nickel and Cobalt Exposure for Metal Allergic Patients

    PubMed Central

    Mucci, Tania; Chong, Melanie; Lorton, Mark Davis; Fonacier, Luz

    2013-01-01

    The use of cellular phones has risen exponentially with over 300 million subscribers. Nickel has been detected in cell phones and reports of contact dermatitis attributable to metals are present in the literature. We determined nickel and cobalt content in popular cell phones in the United States. Adults (>18 years) who owned a flip phone, Blackberry®, or iPhone® were eligible. Seventy-two cell phones were tested using SmartPractice's® commercially available nickel and cobalt spot tests. Test areas included buttons, keypad, speakers, camera, and metal panels. Of the 72 cell phones tested, no iPhones or Droids® tested positive for nickel or cobalt. About 29.4% of Blackberrys [95% confidence interval (CI), 13%–53%] tested positive for nickel; none were positive for cobalt. About 90.5% of flip phones (95% CI, 70%–99%) tested positive for nickel and 52.4% of flip phones (95% CI, 32%–72%) tested positive for cobalt. Our study indicates that nickel and cobalt are present in popular cell phones. Patients with known nickel or cobalt allergy may consider their cellular phones as a potential source of exposure. Further studies are needed to examine whether there is a direct association with metal content in cell phones and the manifestation of metal allergy. PMID:24380018

  20. Studies on KIT-6 Supported Cobalt Catalyst for Fischer–Tropsch Synthesis

    SciTech Connect

    Gnanamani, M.; Jacobs, G; Graham, U; Ma, W; Pendyala, V; Ribeiro, M; Davis, B

    2010-01-01

    KIT-6 molecular sieve was used as a support to prepare cobalt catalyst for Fischer-Tropsch synthesis (FTS) using an incipient wetness impregnation method to produce cobalt loadings of 15 and 25 wt%. The catalysts were characterized by BET surface area, X-ray diffraction, scanning transmission election microscopy (STEM), extended X-ray absorption fine spectroscopy and X-ray absorption near edge spectroscopy. The catalytic properties for FTS were evaluated using a 1L CSTR reactor. XRD, pore size distribution, and STEM analysis indicate that the KIT-6 mesostructure remains stable during and after cobalt impregnation and tends to form smaller cobalt particles, probably located inside the mesopores. The mesoporous KIT-6 exhibited a slightly higher cobalt dispersion compared to amorphous SiO{sub 2} supported catalyst. With the higher Co loading (25 wt%) on KIT-6, partial structural collapse was observed after the FTS reaction. Compared to an amorphous SiO{sub 2} supported cobalt catalyst, KIT-6 supported cobalt catalyst displayed higher methane selectivity at a similar Co loading, likely due to diffusion effects.

  1. Cobalt and nickel stabilize stem cell transcription factor OCT4 through modulating its sumoylation and ubiquitination.

    PubMed

    Yao, Yixin; Lu, Yinghua; Chen, Wen-Chi; Jiang, Yongping; Cheng, Tao; Ma, Yupo; Lu, Lou; Dai, Wei

    2014-01-01

    Stem cell research can lead to the development of treatments for a wide range of ailments including diabetes, heart disease, aging, neurodegenerative diseases, spinal cord injury, and cancer. OCT4 is a master regulator of self-renewal of undifferentiated embryonic stem cells. OCT4 also plays a crucial role in reprogramming of somatic cells into induced pluripotent stem (iPS) cells. Given known vivo reproductive toxicity of cobalt and nickel metals, we examined the effect of these metals on expression of several stem cell factors in embryonic Tera-1 cells, as well as stem cells. Cobalt and nickel induced a concentration-dependent increase of OCT4 and HIF-1α, but not NANOG or KLF4. OCT4 induced by cobalt and nickel was due primarily to protein stabilization because MG132 stabilized OCT4 in cells treated with either metals and because neither nickel nor cobalt significantly modulated its steady-state mRNA level. OCT4 stabilization by cobalt and nickel was mediated largely through reactive oxygen species (ROS) as co-treatment with ascorbic acid abolished OCT4 increase. Moreover, nickel and cobalt treatment increased sumoylation and mono-ubiquitination of OCT4 and K123 was crucial for mediating these modifications. Combined, our observations suggest that nickel and cobalt may exert their reproductive toxicity through perturbing OCT4 activity in the stem cell compartment. PMID:24497960

  2. The nature of graphene-metal bonding probed by Raman spectroscopy: the special case of cobalt

    NASA Astrophysics Data System (ADS)

    Serrano-Esparza, Inés; Fan, Jiyu; Michalik, Jan M.; Alfredo Rodríguez, Luis; Ibarra, Manuel Ricardo; María de Teresa, José

    2016-03-01

    The nature of graphene-metal bonding is crucial for the performance of graphene-based electronic devices. Raman spectroscopy is a powerful technique for probing the electronic behaviour of graphene-metal interfaces. The changes in the Raman spectrum of pristine graphene upon contact with standard metal layers are reported here. In particular, the study is focused on metallization by electron-beam evaporation using chromium or titanium (commonly used as an adhesion layer to improve the bonding of other metals such as gold) and nickel or cobalt (ferromagnetic materials used for spintronics). The results obtained indicate that the main changes in the Raman spectra can be explained in terms of a biaxial strain generated by graphene trying to match the crystalline lattice of the metal. In the case of cobalt, we find that the strong binding of some cobalt atoms to graphene generates a spectrum with a duplication of the characteristic graphene peaks: those corresponding to cobalt physisorbed to graphene and those corresponding to cobalt chemisorbed to graphene, strongly redshifted. Such special behaviour of the graphene-cobalt interface is correlated to the low contact resistance and the enhanced perpendicular magnetic anisotropy of cobalt on graphene.

  3. Selective Area Band Engineering of Graphene using Cobalt-Mediated Oxidation.

    PubMed

    Bazylewski, Paul F; Nguyen, Van Luan; Bauer, Robert P C; Hunt, Adrian H; McDermott, Eamon J G; Leedahl, Brett D; Kukharenko, Andrey I; Cholakh, Seif O; Kurmaev, Ernst Z; Blaha, Peter; Moewes, Alexander; Lee, Young Hee; Chang, Gap Soo

    2015-01-01

    This study reports a scalable and economical method to open a band gap in single layer graphene by deposition of cobalt metal on its surface using physical vapor deposition in high vacuum. At low cobalt thickness, clusters form at impurity sites on the graphene without etching or damaging the graphene. When exposed to oxygen at room temperature, oxygen functional groups form in proportion to the cobalt thickness that modify the graphene band structure. Cobalt/Graphene resulting from this treatment can support a band gap of 0.30 eV, while remaining largely undamaged to preserve its structural and electrical properties. A mechanism of cobalt-mediated band opening is proposed as a two-step process starting with charge transfer from metal to graphene, followed by formation of oxides where cobalt has been deposited. Contributions from the formation of both CoO and oxygen functional groups on graphene affect the electronic structure to open a band gap. This study demonstrates that cobalt-mediated oxidation is a viable method to introduce a band gap into graphene at room temperature that could be applicable in electronics applications. PMID:26486966

  4. Cobalt whole blood concentrations in healthy adult male volunteers following two-weeks of ingesting a cobalt supplement.

    PubMed

    Tvermoes, Brooke E; Finley, Brent L; Unice, Kenneth M; Otani, Joanne M; Paustenbach, Dennis J; Galbraith, David A

    2013-03-01

    Recently, there has been an increase in the marketing and sales of dietary supplements, energy drinks, and other consumer products that may contain relatively high concentrations of essential elements. Cobalt-containing supplements are readily available in the U.S. and have been marketed to consumers as energy enhancers. However, little information is available regarding cobalt (Co) body burden and steady-state blood concentrations following the intake of Co dietary supplements. We assessed Co whole blood concentrations in four healthy adult male volunteers who ingested a commercially available Co supplement (0.4 mg Co/day) for 15 or 16 days. Pre-supplementation blood Co concentrations were less than the reporting limit of 0.5 μg/L, consistent with background concentrations reported to range between 0.1 and 0.4 μg/L. The mean whole blood Co concentration in the volunteers after 15 or 16 days of dosing was 3.6 μg Co/L and ranged from 1.8 to 5.1 μg Co/L. The mean observed concentration in the study group was approximately 9-36 times greater than background concentrations. Further studies of Co whole blood concentrations following supplementation over longer time periods with additional monitoring of physiological parameters may provide useful information for evaluating the health of persons who take various doses of Co. PMID:23207477

  5. Development of a stable cobalt-ruthenium Fisher-Tropsch catalyst. Final report

    SciTech Connect

    Frame, R.R.; Gala, H.B.

    1995-02-01

    The reverse micelle catalyst preparation method has been used to prepare catalysts on four supports: magnesium oxide, carbon, alumina- titania and steamed Y zeolite. These catalysts were not as active as a reference catalyst prepared during previous contracts to Union Carbide Corp. This catalyst was supported on steamed Y zerolite support and was impregnated by a pore-filling method using a nonaqueous solvent. Additional catalysts were prepared via pore- filling impregnation of steamed Y zeolites. These catalysts had levels of cobalt two to three and a half times as high as the original Union Carbide catalyst. On a catalyst volume basis they were much more active than the previous catalyst; on an atom by atom basis the cobalt was about of the same activity, i.e., the high cobalt catalysts` cobalt atoms were not extensively covered over and deactivated by other cobalt atoms. The new, high activity, Y zerolite catalysts were not as stable as the earlier Union Carbide catalyst. However, stability enhancement of these catalysts should be possible, for instance, through adjustment of the quantity and/or type of trace metals present. A primary objective of this work was determination whether small amounts of ruthenium could enhance the activity of the cobalt F-T catalyst. The reverse micelle catalysts were not activated by ruthenium, indeed scanning transmission electronic microscopy (STEM) analysis provided some evidence that ruthenium was not present in the cobalt crystallites. Ruthenium did not seem to activate the high cobalt Y zeolite catalyst either, but additional experiments with Y zeolite-supported catalysts are required. Should ruthenium prove not to be an effective promoter under the simple catalyst activation procedure used in this work, more complex activation procedures have been reported which are claimed to enhance the cobalt/ruthenium interaction and result in activity promotion by ruthenium.

  6. Evaluation of mechanical properties of a low-cobalt wrought superalloy

    NASA Astrophysics Data System (ADS)

    Dreshfield, R. L.

    1993-08-01

    In the late 1970s and early 1980s, cobalt was subjected to significant supply and market pressures. Those pressures caused renewed attention to the use of cobalt in aircraft engines. A NASA-sponsored program called Conservation of Strategic Aerospace Materials (COSAM) was created in response to the supply problems with cobalt and other aerospace metals. Among the work performed in the COSAM program and simultaneously by others were several studies on laboratory-size heats of wrought nickel-base super-alloys. These studies suggested that the cobalt levels of the alloys might be reduced by about half, with minimal negative impact on mechanical properties. The Lewis Research Center procured a 1365-kg (3000-lb) heat of a modified Waspaloy having a reduced cobalt level. This article reports the results of a program performed at four gas turbine manufacturers which evaluated the mechanical properties of forgings fabricated from that heat. The alloy chemistry selected reduced the nominal cobalt level from 13.5 to 7.75 wt%. To compensate for the anticipated strength reduction caused by a slight reduction in the amount of γ, the nominal aluminum was increased from 1.3 to 1.5% and the titanium was increased from 3.0 to 3.2%. The increase in aluminum and titanium were intended to increase the amount of γ in the al-loy. Tensile, creep-rupture, low-cycle fatigue, and cyclic crack growth tests were performed. In addition the effect of hydrogen on the alloy was determined. It was concluded that, in the event of a cobalt short-age, a low-cobalt modification of Waspaloy alloy could be substituted for Waspaloy with little develop-ment in those applications that are not creep-rupture limited. With some additional development to better control the grain size, it is probable that most of the current Waspaloy requirements might be met with a lower cobalt alloy.

  7. Evaluation of mechanical properties of a low-cobalt wrought superalloy

    SciTech Connect

    Dreshfield, R.L. . Lewis Research Center)

    1993-08-01

    In the late 1970's and early 1980's, cobalt was subjected to significantly supply and market pressures. Those pressures caused renewed attention to the use of cobalt in aircraft engines. A NASA-sponsored program called Conservation of Strategic Aerospace Materials (COSAM) was created in response to the supply problems with cobalt and other aerospace metals. Among the work performed in the COSAM program and simultaneously by others were several studies on laboratory-size heats of wrought nickel-base super-alloys. These studies suggested that the cobalt levels of the alloys might be reduced by about half, with minimal negative impact on mechanical properties. The Lewis Research Center procured a 1,365-kg (3,000-lb) heat of a modified Waspaloy having a reduced cobalt level. This article reports the results of a program performed at four gas turbine manufacturers which evaluated the mechanical properties of forgings fabricated from that heat. The alloy chemistry selected reduced the nominal cobalt level from 13.5 to 7.75 wt %. To compensate for the anticipated strength reduction caused by a slight reduction in the amount of [gamma][prime], the nominal aluminum was increased from 1.3 to 1.5% and the titanium was increased from 3.0 to 3.2%. The increase in aluminum and titanium were intended to increase the amount of [gamma][prime] in the alloy. Tensile, creep-rupture, low-cycle fatigue, and cyclic crack growth tests were performed. In addition the effect of hydrogen on the alloy was determined. It was concluded that, in the event of a cobalt shortage, a low-cobalt modification of Waspaloy alloy could be substituted for Waspaloy with little development in those applications that are not creep-rupture limited. With some additional development to better control the grain size, it is probable that most of the current Waspaloy requirements might be met with a lower cobalt alloy.

  8. Determination of trace cobalt concentrations in human serum by adsorptive stripping voltammetry.

    PubMed

    Kajic, Petra; Milosev, Ingrid; Pihlar, Boris; Pisot, Venceslav

    2003-01-01

    The goal of our study was to develop an accurate and reliable method for determining trace cobalt concentrations in human serum. The method was used to determine cobalt in the sera of healthy persons and patients with orthopaedic implants containing cobalt - a possible source of systemic release of cobalt into the human body. This goal is of vital interest since cobalt and its compounds are classified by IARC as potentially carcinogenic to humans. We used an electrochemical method, adsorptive stripping voltammetry (AdSV), which made possible the low detection limit and high sensitivity needed for measurements in human serum. The serum was acid digested by a combination of H2SO4, HNO3 and H2O2 in a 10 mL Kjeldhal flask. The digested sample was then dissolved in 0.1 mol/L ammonia buffer, pH 9.0 +/- 0.2. The determination is based on the adsorptive collection of the complex of cobalt (II) with dimethylglyoxime on a hanging mercury drop electrode (HMDE). The optimum values of adsorption potential and time were determined to be -0.8 V and 60 s. The optimisation of the sample digestion protocol and measurement procedures ensured the reliable assessment of low cobalt concentrations, down to 0.03 microg/L. The mean concentration of serum cobalt in four healthy persons was 0.11 +/- 0.06 microg/L, and in four patients with total hip replacements 0.34 +/- 0.07 microg/L. This method will be used routinely for measuring serum cobalt levels in patients with total hip replacements. PMID:14968926

  9. Cobalt oxide 2D nano-assemblies from infinite coordination polymer precursors mediated by a multidentate pyridyl ligand.

    PubMed

    Li, Guo-Rong; Xie, Chen-Chao; Shen, Zhu-Rui; Chang, Ze; Bu, Xian-He

    2016-05-01

    In this work, the construction of Co3O4 two dimensional (2D) nano-assemblies utilizing infinite coordination polymers (ICPs) as precursors was investigated, aiming at the morphology targeted fabrication and utilization of 2D materials. Based on the successful modulation of morphology, a rose-like Co based ICP precursor was obtained, which was further transformed into porous Co3O4 nanoflake assemblies with a well-preserved 2D morphology and a large surface area. The mechanism of the morphology modulation was illustrated by systematic investigation, which demonstrated the crucial role of a modulating agent in the formation of 2D nano-assemblies. In addition, the cobalt oxide 2D nano-assemblies are fabricated into a lithium anode combined with graphene, and the remarkable capacity and stability (900 mA h g(-1) after 50 cycles) of the resulting Co3O4/G nanocomposite indicates its potential in lithium battery applications. PMID:27064264

  10. Characterization of Nanocrystalline Nickel-Cobalt Alloys Synthesized by Direct and Pulse Electrodeposition

    NASA Astrophysics Data System (ADS)

    Salehi, M.; Saidi, A.; Ahmadian, M.; Raeissi, K.

    2014-01-01

    Nanocrystalline Ni-Co alloys are electrodeposited by direct (DC) and pulse current (PC) in an electrolyte solution which consisted of nickel sulfate, cobalt sulfate and boric acid. Electrodeposition parameters including current density, electrolyte pH and pulse times in a single electrolyte bath were changed. XRD pattern showed that the structure of the alloys depends on Co content and the synthesis parameter and changed from single phase structure (fcc) to dual phase structure (fcc + hcp). The Co content in the deposited alloys declined from 70 at.% to 50 at.% by increasing in direct current from 70 mA/cm2 to 115 mA/cm2 and also decreased from 75 at.% to 33 at.% with decrease in pH values from 4 to 2. By applying PC the Co content changed from 76 at.% to 41 at.%. Magnetic properties measurements showed the saturation magnetization (Ms) increased with increasing the Co content. There was no significant effect on coercivity values (Hc) with change in Co content and about 40 Oe was obtained for all samples. The grain size of deposited alloys obtained between 24-58 nm and 15-21 nm by applying DC and PC, respectively.

  11. Microfluxgate sensor with amorphous cobalt (Co-Nb-Zr) soft magnetic core for electronic compass

    SciTech Connect

    Na, Kyoung-Won; Yuan, Jingli; Ji, Joon-Ho; Choi, Sang-On

    2006-04-15

    A silicon based microfluxgate sensor with a cobalt based amorphous soft magnetic core for electronic compass is presented in this paper. A sputtered Co{sub 85}Nb{sub 12}Zr{sub 3} magnetic core having a rectangular ring shape is combined with microcopper solenoid coils for excitation and pickup, which were wound alternately around the core to increase the number of coil turns. The Co{sub 85}Nb{sub 12}Zr{sub 3} as a core material is adopted for improving properties of the magnetic core and easy integration with micromachining processes to achieve a small size of the sensor. The sputtered Co{sub 85}Nb{sub 12}Zr{sub 3} showed dc effective permeability of {approx}10 000 and an extremely low coercivity of {approx}0.03 Oe with the thickness of 1 {mu}m. The Co{sub 85}Nb{sub 12}Zr{sub 3} as a thin film core with high permeability and low coercivity was easily saturated by a low excitation magnetic field, enhancing the sensitivity and linearity of the microfluxgate sensor. Finally, the sensor showed excellent linearity response over the range of -300 to 300 {mu}T with sensitivity of 60 V/T at the excitation condition of 3.0 V{sub p-p} and 5.0 MHz square wave form. The sensor size excluding pad region is about 0.55x1.4 mm{sup 2}.

  12. New developments in cobalt-based Fischer-Tropsch catalysis and processes

    SciTech Connect

    Singleton, A.H.; Davis, B.E.; Oukaci, R.

    1997-12-31

    The Williams Companies, Inc. of Tulsa, Oklahoma, has announced a breakthrough in gas-to-liquids (GTL) technology that revolutionizes the production of transportation fuels from natural gas. Building on its twenty years of research in Fischer-Tropsch (F-T) conversion technology, Williams has developed a new process that significantly outperforms existing GTL technologies for large-scale (ca. 50,000 BPSD) applications and advances the state-of the-art of converting natural gas into high quality liquid transportation fuels. By employing a new generation of cobalt-based catalysts, Williams` GasCat{sup SM} F-T process achieves high productivity, resulting in superior catalytic reactor performance compared to existing F-T techniques. The GasCat process also reduces capital requirements and operating costs by employing advanced slurry bubble column reactor (SBCR) technology. Although the process is applicable to coal derived synthesis gas, GasCat has enormous implications for large remote gas reserves worldwide, due to the limited options previously available for exploiting the potential of such reservoirs. While the paper presents the details and significance of this new development as it relates to natural gas, it obviously has similar significance to the indirect liquefaction of coal.

  13. Implication of Structural Disorder in The Charge Transport Properties of Cobalt-phthalocyanine Thin Films

    SciTech Connect

    Debnath, A. K.; Kumar, A.; Samanta, S.; Singh, A.; Aswal, D. K.; Gupta, S. K.; Yakhmi, J. V.

    2011-07-15

    The charge transport properties of 100 nm thick cobalt phthalocyanine (CoPc) films grown on single crystal Al{sub 2}O{sub 3}(0001 oriented) and quartz substrates using molecular beam epitaxy, have been investigated as a function of applied bias ({+-} 50 V) at room temperature. Films grown on Al{sub 2}O{sub 3} are highly ordered and exhibited non-hysteretic current-voltage (J-V) characteristics. On the other hand, films grown on quartz substrates are highly disordered and exhibited hysteretic J-V characteristics due to charge trapping. The analysis of J-V characteristics of films on Al{sub 2}O{sub 3} substrates show that the transport is governed by shallow trap mediated space charge limited conduction (SCLC), while for the films grown on the quartz substrate transport is through the exponentially distributed traps mediated SCLC. X-ray photoelectron spectroscopy data show that charge trapping centers in the films grown on quartz substrates are created by chemisorbed oxygen.

  14. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-01

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1Terabit/in.2 The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15nm) and interwire spacing (24nm), whereas nanowire length (typically 50to1000nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7kOe at 300K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  15. Cobalt Zinc Ferrite Nanoparticles as a Potential Magnetic Resonance Imaging Agent: An In vitro Study

    PubMed Central

    Ghasemian, Zeinab; Shahbazi-Gahrouei, Daryoush; Manouchehri, Sohrab

    2015-01-01

    Background: Magnetic Nanoparticles (MNP) have been used for contrast enhancement in Magnetic Resonance Imaging (MRI). In recent years, research on the use of ferrite nanoparticles in T2 contrast agents has shown a great potential application in MR imaging. In this work, Co0.5Zn0.5Fe2O4 and Co0.5Zn0.5Fe2O4-DMSA magnetic nanoparticles, CZF-MNPs and CZF-MNPs-DMSA, were investigated as MR imaging contrast agents. Methods: Cobalt zinc ferrite nanoparticles and their suitable coating, DMSA, were investigated under in vitro condition. Human prostate cancer cell lines (DU145 and PC3) with bare (uncoated) and coated magnetic nanoparticles were investigated as nano-contrast MR imaging agents. Results: Using T2-weighted MR images identified that signal intensity of bare and coated MNPs was enhanced with increasing concentration of MNPs in water. The values of 1/T2 relaxivity (r2) for bare and coated MNPs were found to be 88.46 and 28.80 (mM−1 s−1), respectively. Conclusion: The results show that bare and coated MNPs are suitable as T2-weighted MR imaging contrast agents. Also, the obtained r2/r1 values (59.3 and 50) for bare and coated MNPs were in agreement with the results of other previous relevant works. PMID:26140183

  16. In vitro evaluation of anticancer and antibacterial activities of cobalt oxide nanoparticles.

    PubMed

    Khan, Shahanavaj; Ansari, Anees A; Khan, Abdul Arif; Ahmad, Rehan; Al-Obaid, Omar; Al-Kattan, Wael

    2015-12-01

    Cobalt oxide nanoparticles (Co3O4-NPs) were synthesized using simple urea-based thermal decomposition method. Phase purity and particle size of as-synthesized nanoparticles were characterized through X-ray diffraction pattern (XRD) and transmission electron microscopy. Through XRD morphology of the Co3O4-NPs was found to be variable in size with range of 36 nm. In our present study, we explored the potential cytotoxic and antibacterial effects of Co3O4-NPs in human colorectal types of cancerous cells (HT29 and SW620) and also nine Gram-positive and Gram-negative bacteria. Co3O4-NPs showed promising anticancer activity against HT29 and SW620 cells with IC50 value of 2.26 and 394.5 μg/mL, respectively. However, no significant effect of Co3O4-NPs was observed against bacterial strains. Furthermore, a detailed study has been carried out to investigate the possible mechanism of cell death in HT29 cancer cell line through the analysis of expression level of anti-apoptotic Bcl2 and BclxL markers. Western blot analysis results suggested significant role of Co3O4-NPs exposure in cell death due to apoptosis. PMID:26563952

  17. Cobalt double-ring and double-dot structures: Magnetic properties

    NASA Astrophysics Data System (ADS)

    López-Urías, F.; Torres-Heredia, J. J.; Muñoz-Sandoval, E.

    2016-02-01

    The magnetization reversal mechanism of nanostructures of cobalt double-rings (D-rings) and double-dots (D-dots) is investigated in the framework of micromagnetic simulations. The arrays contain two identical coupled rings (wide and narrow) or dots with outer diameter of 200 nm and thicknesses ranging from 2-20 nm. Hysteresis loops, dipole-dipole and exchange energies are systematically calculated for the cases of the structures touching and the structures with a 50-nm inter-magnet separation; moreover, magnetization states along the hysteresis curve are analyzed. The results of both dot and ring D-magnets are compared with the corresponding individual magnets. Our results reveal that all D-ring (in contact and separated) arrays containing narrow rings exhibit non-null remanent magnetization; furthermore, higher coercive fields are promoted when the magnet thickness is increased. It is observed that the magnetization reversal is driven mainly by a clockwise rotation of onion-states, followed by states of frustrated vortices. Our results could help improve the understanding of the magnetic interactions in nanomagnet arrays.

  18. Graphene-Encapsulated Nanosheet-Assembled Zinc-Nickel-Cobalt Oxide Microspheres for Enhanced Lithium Storage.

    PubMed

    Zhang, Qiaobao; Chen, Huixin; Han, Xiang; Cai, Junjie; Yang, Yong; Liu, Meilin; Zhang, Kaili

    2016-01-01

    The appropriate combination of hierarchical transition-metal oxide (TMO) micro-/nanostructures constructed from porous nanobuilding blocks with graphene sheets (GNS) in a core/shell geometry is highly desirable for high-performance lithium-ion batteries (LIBs). A facile and scalable process for the fabrication of 3D hierarchical porous zinc-nickel-cobalt oxide (ZNCO) microspheres constructed from porous ultrathin nanosheets encapsulated by GNS to form a core/shell geometry is reported for improved electrochemical performance of the TMOs as an anode in LIBs. By virtue of their intriguing structural features, the produced ZNCO/GNS core/shell hybrids exhibit an outstanding reversible capacity of 1015 mA h g(-1) at 0.1 C after 50 cycles. Even at a high rate of 1 C, a stable capacity as high as 420 mA h g(-1) could be maintained after 900 cycles, which suggested their great potential as efficient electrodes for high-performance LIBs. PMID:26676945

  19. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    SciTech Connect

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T.

    2005-05-15

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1 Terabit/in.{sup 2} The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15 nm) and interwire spacing (24 nm), whereas nanowire length (typically 50 to 1000 nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7 kOe at 300 K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  20. Characterization and kinetic investigation of electroless deposition of pure cobalt thin films on silicon substrates

    NASA Astrophysics Data System (ADS)

    Cheng, S. L.; Hsu, T. L.; Lee, T.; Lee, S. W.; Hu, J. C.; Chen, L. T.

    2013-01-01

    We present here the results of studies of the synthesis and growth behaviors of electroless pure Co thin films on Pd-activated Si substrates using hydrazine as the reductant. Using the hydrazine-modified electroless Co plating processes, dense and continuous pure Co films were deposited on (0 0 1)Si for samples plated at 30-45 °C. This electroless plating process could be explained by the electrochemical mechanism. After a series of transmission electron microscopic examinations, the deposited Co films were determined to be polycrystalline with a hexagonal crystal structure and the average Co film thickness at each temperature studied was found to follow a linear relationship with the plating time. The deposition rates of pure Co films increase with the plating temperatures from 7.3 nm/min to 12.6 nm/min. By measuring the Co deposition rates at different plating temperatures, the activation energy for linear growth of the electroless Co thin films on Si substrates derived from an Arrhenius plot is about 32.6 kJ/mol. As the plating temperature was increased to 50 °C or higher, the plating solution became turbid and the formation of dendritic cobalt deposits was observed.

  1. Cobalt oxyhydroxide nanoflake based fluorescence sensing platform for label-free detection of DNA.

    PubMed

    Chang, Yaqing; Zhang, Zhe; Liu, Huiqing; Wang, Nan; Tang, Jilin

    2016-08-01

    Detection of specific DNA sequences is critical in life science. In this study, we investigated the interaction of cobalt oxyhydroxide (CoOOH) nanoflakes with DNA and their fluorescence quenching mechanism of a FAM-labeled single-stranded DNA (ssDNA) probe. ssDNA could adsorb on the CoOOH surface via electrostatic interactions and therefore the fluorescence of FAM was quenched. However, upon addition of targets, ssDNA was hybridized with target DNA and the formed double-stranded DNA (dsDNA) had much weaker affinity to CoOOH, resulting in the retaining of fluorescence. Based on the affinity difference of CoOOH nanoflakes to ssDNA and dsDNA and fluorescence resonance energy transfer based fluorescence quenching, a mix-and-detect method was proposed for homogeneous detection of DNA. The proposed method is simple and can be finished in a few minutes with high sensitivity. Furthermore, it displays a wide linear range from 1 to 50 nM with a detection limit of 0.5 nM and is capable of detecting DNA in real biological samples. PMID:27251111

  2. Distribution ratios on Dowex 50W resins of metal leached in the caron nickel recovery process

    SciTech Connect

    Reynolds, B.A.; Metsa, J.C.; Mullins, M.E.

    1980-05-01

    Pressurized ion exchange on Dowex 50W-X8 and 50W-X12 resins was investigated using elution techniques to determine distribution ratios for copper, nickel, and cobalt complexes contained in ammonium carbonate solution, a mixture which approximates the waste liquor from the Caron nickel recovery process. Results were determined for different feed concentrations, as well as for different concentrations and pH values of the ammonium carbonate eluant. Distribution ratios were compared with those previously obtained from a continuous annular chromatographic system. Separation of copper and nickel was not conclusively observed at any of the conditions examined.

  3. Chemical Mechanical Polishing of Ruthenium, Cobalt, and Black Diamond Films

    NASA Astrophysics Data System (ADS)

    Peethala, Brown Cornelius

    Ta/TaN bilayer serves as the diffusion barrier as well as the adhesion promoter between Cu and the dielectric in 32 nm technology devices. A key concern of future technology devices (<32 nm) for Cu interconnects is the extendibility of TaN/Ta/Cu-seed to sustain the diffusion barrier performance without forming voids and meeting the requirements of low resistivity. These are very challenging requirements for the Ta/TaN bilayer at a thickness of < 5 nm. Hence, ruthenium (Ru) and cobalt (Co), among these, are being considered for replacing Ta/TaN as barrier materials for Cu interconnects in future technology devices. Both are very attractive for reasons such as the capability of direct electroplating of Cu, lower resistivity and for a single layer (vs. a bilayer of Ta/TaN) to act as a barrier. During patterning, they need to be planarized using conventional chemical mechanical polishing (CMP) to achieve a planar surface. However, CMP of these new barrier materials requires novel slurry compositions that provide adequate selectivity towards Cu and dielectric films, and minimize galvanic corrosion. Apart from the application as a barrier, Ru also has been proposed as a lower electrode material in metal-insulator-metal capacitors where high (> 50 nm/min) Ru removal rates (RRs) are required and as a stop layer in magnetic recording head fabrication where low (< 1 nm/min) Ru RRs are desired. A Ru removal rate of ˜60 nm/min was achieved with a colloidal silica-based slurry at pH 9 using potassium periodate (KIO4) as the oxidizer. At this pH, toxic RuO4 does not form eliminating a major challenge in Ru CMP. This removal rate was obtained by increasing the solubility of KIO4 by adding potassium hydroxide (KOH). It was also determined that increased the ionic strength is not responsible for the observed increase in Ru removal rate. Benzotirazole (BTA) and ascorbic acid were added to the slurry to reduce the open circuit potential (Eoc) difference between Cu and Ru to ˜20 m

  4. Systems and Methods for the Electrodeposition of a Nickel-cobalt Alloy

    NASA Technical Reports Server (NTRS)

    Ogozalek, Nance Jo (Inventor); Wistrand, Richard E. (Inventor)

    2013-01-01

    Systems and methods for electrodepositing a nickel-cobalt alloy using a rotating cylinder electrode assembly with a plating surface and an electrical contact. The assembly is placed within a plating bath and rotated while running a plating cycle. Nickel-cobalt alloy deposition is selectively controlled by controlling current density distribution and/or cobalt content in the plating bath while running the plating cycle to deposit an alloy of a desired yield strength onto the plating surface in a single plating cycle. In various embodiments, the rotating cylinder may be used as an insitu monitoring method to assist in obtaining the properties desired.

  5. Effects of cobalt on the hot workability of nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Jarrett, R. N.; Collier, J. P.; Tien, J. K.

    1984-01-01

    The effect of cobalt on the workability of nickel-base superalloys is examined with reference to experimental results for four heats of alloys based on the Nimonic 115 composition with varying amounts of nickel substituted for the nominal 14 percent cobalt. It is shown that Co lowers the gamma-prime solvus, which in turn lowers the Cr23C6 carbide solvus. It is further shown that these solvus temperatures bracket the hot working range for the alloys. However, thermomechanical processing modifications reflecting the effect of Co on the gamma-prime and carbide solvi are shown to restore the workability and the properties of alloys with little or no cobalt.

  6. A novel process from cobalt nanowire to Co3O4 nanotube

    NASA Astrophysics Data System (ADS)

    Li, Tao; Yang, Shaoguang; Huang, Lisheng; Gu, Benxi; Du, Youwei

    2004-11-01

    Cobalt oxide (Co3O4) nanotubes were synthesized by calcining cobalt nanowires embedded in an anodic alumina template (AAT) in air. The morphologies and phases of the nanowires/nanotubes were studied by transmission electron microscope (TEM) and x-ray diffraction (XRD) respectively. A hypothesis of the tube formation process is presented and illustrated by experimental results. According to the experimental results, it is concluded that competition between the oxidation and the evaporation of cobalt nanocrystals plays a crucial role in the formation of such tube-like nanostructures of Co3O4.

  7. Boryl-mediated reversible H2 activation at cobalt: catalytic hydrogenation, dehydrogenation, and transfer hydrogenation.

    PubMed

    Lin, Tzu-Pin; Peters, Jonas C

    2013-10-16

    We describe the synthesis of a cobalt(I)-N2 complex (2) supported by a meridional bis-phosphino-boryl (PBP) ligand. Complex 2 undergoes a clean reaction with 2 equiv of dihydrogen to afford a dihydridoboratocobalt dihydride (3). The ability of boron to switch between a boryl and a dihydridoborate conformation makes possible the reversible conversion of 2 and 3. Complex 3 reacts with HMe2N-BH3 to give a hydridoborane cobalt tetrahydridoborate complex. We explore this boryl-cobalt system in the context of catalytic olefin hydrogenation as well as amine-borane dehydrogenation/transfer hydrogenation. PMID:24079337

  8. Structure and Morphology Study of Cobalt Oxide Doped Silica Nanocomposite Films

    NASA Astrophysics Data System (ADS)

    Drasovean, Romana; Monteiro, Regina; Cherif, Mourad

    2010-01-01

    Cobalt oxide doped silica films were synthesized by a dip-coating technique. Initial compounds were cobalt acetate Co(CH3COO)2ṡ4H2O and tetraethoxysilane Si(OC2H5)4. The chemical composition was studied by X-ray diffraction and UV-Vis spectroscopy. The morphology analyses were carried out by means of atomic force microscopy. The average diameter of cobalt oxide dispersed particles increases with the molar ratio Co:Si and with the aging time of the initial colloidal solution.

  9. Investigation of Megavoltage Digital Tomosynthesis using a Cobalt-60 Source

    NASA Astrophysics Data System (ADS)

    MacDonald, Amy

    The ability for megavoltage computed tomography patient setup verification using a cobalt-60 (Co-60) gamma ray source has been established in the context of cobalt tomotherapy. However, it would be beneficial to establish improved cobalt imaging that could be used on more conventional units. In terms of safety and efficiency, this imaging technique would provide the patient with less exposure to radiation. Digital tomosynthesis (DT) is an imaging modality that may provide improved depth localization and in-plane visibility compared to conventional portal imaging in modern Co-60 radiation therapy. DT is a practical and efficient method of achieving depth localization from a limited gantry rotation and a limited number of projections. In DT, each plane of the imaging volume can be brought into focus by relatively displacing the composite images and superimposing the shifted dataset according to the acquisition geometry. Digital flat-panel technology has replaced the need for multiple film exposures and therefore the speed of imaging and capabilities for image processing has put DT in the forefront of both clinical and industrial imaging applications. The objective of this work is to develop and evaluate the performance of an experimental system for megavoltage digital tomosynthesis ( MVDT) imaging using a Co-60 gamma ray source. Linear and isocentric acquisition geometries are implemented using tomographic angles of 20--60° and 10--60 projections. Reconstruction algorithms are designed for both acquisition geometries. Using the backprojection approach, the data are shifted and added to reconstruct focal planes of interest. Depth localization and its dependence on tomographic angle and projection density are visualized with an anthropomorphic head phantom. High contrast resolution at localized depths is quantified using the modulation transfer function approach. Results show that focal-plane visibility is improved for larger tomographic angles and that focal

  10. Cobalt, manganese, and iron near the Hawaiian Islands: A potential concentrating mechanism for cobalt within a cyclonic eddy and implications for the hybrid-type trace metals

    NASA Astrophysics Data System (ADS)

    Noble, Abigail E.; Saito, Mak A.; Maiti, Kanchan; Benitez-Nelson, Claudia R.

    2008-05-01

    The vertical distributions of cobalt, iron, and manganese in the water column were studied during the E-Flux Program (E-Flux II and III), which focused on the biogeochemistry of cold-core cyclonic eddies that form in the lee of the Hawaiian Islands. During E-Flux II (January 2005) and E-Flux III (March 2005), 17 stations were sampled for cobalt ( n=147), all of which demonstrated nutrient-like depletion in surface waters. During E-Flux III, two depth profiles collected from within a mesoscale cold-core eddy, Cyclone Opal, revealed small distinct maxima in cobalt at ˜100 m depth and a larger inventory of cobalt within the eddy. We hypothesize that this was due to a cobalt concentrating effect within the eddy, where upwelled cobalt was subsequently associated with sinking particulate organic carbon (POC) via biological activity and was released at a depth coincident with nearly complete POC remineralization [Benitez-Nelson, C., Bidigare, R.R., Dickey, T.D., Landry, M.R., Leonard, C.L., Brown, S.L., Nencioli, F., Rii, Y.M., Maiti, K., Becker, J.W., Bibby, T.S., Black, W., Cai, W.J., Carlson, C.A., Chen, F., Kuwahara, V.S., Mahaffey, C., McAndrew, P.M., Quay, P.D., Rappe, M.S., Selph, K.E., Simmons, M.P., Yang, E.J., 2007. Mesoscale eddies drive increased silica export in the subtropical Pacific Ocean. Science 316, 1017-1020]. There is also evidence for the formation of a correlation between cobalt and soluble reactive phosphorus during E-Flux III relative to the E-Flux II cruise that we suggest is due to increased productivity, implying a minimum threshold of primary production below which cobalt-phosphate coupling does not occur. Dissolved iron was measured in E-Flux II and found in somewhat elevated concentrations (˜0.5 nM) in surface waters relative to the iron depleted waters of the surrounding Pacific [Fitzwater, S.E., Coale, K.H., Gordon, M.R., Johnson, K.S., Ondrusek, M.E., 1996. Iron deficiency and phytoplankton growth in the equatorial Pacific. Deep

  11. Absolute oscillator strengths for lines of neutral cobalt between 2276 A and 9357 A and a redetermination of the solar cobalt abundance

    NASA Astrophysics Data System (ADS)

    Cardon, B. L.; Smith, P. L.; Scalo, J. M.; Testerman, L.; Whaling, W.

    1982-09-01

    Absolute oscillator strengths of neutral cobalt have been determined from hook measurements for 159 transitions and emission intensity measurements for 314 transitions between 2276 Å and 9357 Å. Ninety-five of these transitions were subjected to the procedure developed by Cardon, Smith, and Whaling which fits combined absorption and emission data to a set of consistent, optimum, relative oscillator strengths and upper level lifetimes. These relative values were normalized to the radiative lifetimes of Figger et al. and of Marek and Vogt obtained by pulsed laser fluorescence. Absolute oscillator strengths for 362 transitions and 36 lifetimes were determined. Typical uncertainties in the reported absolute oscillator strengths are ±15-25% (2/3 confidence level). Equivalent widths were obtained for nineteen solar cobalt lines with the McMath solar telescope at Kitt Peak National Observatory. These widths were used to redetermine the solar cobalt abundance, assuming the photospheric model of Holweger and a microturbulence velocity of 1.0 km s-1. The adopted solar cobalt abundance is the mean value log Co/NH> + 12 = 4.92 ± 0.08 (±19%), from the 19 cobalt transitions. This value is in excellent agreement with the solar values of Ross and Aller, of Biemont, and of Holweger and that of Cameron for carbonaceous chondrites.

  12. Absolute oscillator strengths for lines of neutral cobalt between 2276 A and 9357 A and a redetermination of the solar cobalt abundance

    SciTech Connect

    Cardon, B.L.; Smith, P.L.; Scalo, J.M.; Testerman, L.; Whaling, W.

    1982-09-01

    Absolute oscillator strengths of neutral cobalt have been determined from hook measurements for 159 transitions and emission intensity measurements for 314 transitions between 2276 A and 9357 A. Ninety-five of these transitions were subjected to the procedure developed by Cardon, Smith, and Whaling which fits combined absorption and emission data to a set of consistent, optimum, relative oscillator strengths and upper level lifetimes. These relative values were normalized to the radiative lifetimes of Figger et al. and of Marek and Vogt obtained by pulsed laser fluorescence. Absolute oscillator strengths for 362 transitions and 36 lifetimes were determined. Typical uncertainties in the reported absolute oscillator strengths are +- 15-25% (2/3 confidence level). Equivalent widths were obtained for nineteen solar cobalt lines with the McMath solar telescope at Kitt Peak National Observatory. These widths were used to redetermine the solar cobalt abundance, assuming the photospheric model of Holweger and a microturbulence velocity of 1.0 km s/sup -1/. The adopted solar cobalt abundance is the mean value log +12 = 4.92 +- 0.08 ( +- 19%), from the 19 cobalt transitions. This value is in excellent agreement with the solar values of Ross and Aller, of Biemont, and of Holweger and that of Cameron for carbonaceous chondrites.

  13. Vitamin C interaction with cobalt-ammine cations. Synthesis, spectroscopic and structural characterization of cobalt-pentammine and cobalt-tetrammine sugar complexes containing L-ascorbate anion.

    PubMed

    Tajmir-Riahi, H A

    1986-11-01

    Interaction between [Co(NH3)5Cl]Cl2, [Co(NH3)4Cl2]Cl and L-ascorbic acid has been investigated in aqueous solution and solid complexes of the type [Co(NH3)5 ascorbate]Cl2 X H2O and [Co(NH3)4 ascorbate]Cl2 X H2O have been isolated and characterized by 13C-NMR, FT-IR and electron absorption spectroscopy. Spectroscopic and other evidence suggested that the sugar anion binds monodentately in the [Co(NH3)5 ascorbate]2+ cation via the ionized O3 oxygen atom and bidentately in [Co(NH3)4 ascorbate]2+ through the O1 and O4 oxygen atoms, resulting in a six-coordinate geometry around the Co(III) ion. The intermolecular sugar hydrogen-bonding network is perturbed upon sugar metalation and the sugar moiety shows a similar conformation to that of the sodium ascorbate compound in these series of cobalt-ammine complexes. PMID:3814746

  14. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, R.J.

    1986-12-23

    A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25 C and about 1,200 C, capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments. 2 figs.

  15. Cobalt doped lanthanum chromite material suitable for high temperature use

    DOEpatents

    Ruka, Roswell J.

    1986-01-01

    A high temperature, solid electrolyte electrochemical cell, subject to thermal cycling temperatures of between about 25.degree. C. and about 1200.degree. C., capable of electronic interconnection to at least one other electrochemical cell and capable of operating in an environment containing oxygen and a fuel, is made; where the cell has a first and second electrode with solid electrolyte between them, where an improved interconnect material is applied along a portion of a supporting electrode; where the interconnect is made of a chemically modified lanthanum chromite, containing cobalt as the important additive, which interconnect allows for adjustment of the thermal expansion of the interconnect material to more nearly match that of other cell components, such as zirconia electrolyte, and is stable in oxygen containing atmospheres such as air and in fuel environments.

  16. Characterization of cobalt-dipped nickel electrodes with fibrex substrates

    NASA Technical Reports Server (NTRS)

    Youngman, Carolyn A.; Reid, Margaret A.

    1995-01-01

    Nickel electrodes using fibrous substrates have poorer initial utilization of the active material than those using conventional nickel sinter substrates. Previous investigators had shown that utilization can be dramatically improved by dipping these electrodes in a cobalt solution immediately after the electrochemical impregnation, before formation and cycling is carried out. The present study looked at the gas evolution behavior of dipped and undipped electrodes, impedance curves, and the charge-discharge curves to try to understand the reasons for the improvement in utilization. Impedance measurements under open circuit conditions indicate that some of the improvement is due to a reduction in the ohmic resistance of the surface layer of the particles, in agreement with earlier work. The charge-discharge curves suggest that there may also be an additional increase in the ohmic resistance of the surface layer of the undipped electrode during charging.

  17. Electrodeposited cobalt sulfide hole collecting layer for polymer solar cells

    SciTech Connect

    Zampetti, Andrea; De Rossi, Francesca; Brunetti, Francesca; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

    2014-08-11

    In polymer solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester, the hole collecting layer has to be endowed with its ionization potential close to or greater than that of P3HT (∼5 eV). Conductive polymer blends such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and metal oxides such as vanadium pentoxide (V{sub 2}O{sub 5}) and molybdenum trioxide (MoO{sub 3}) satisfy this requirement and have been the most common materials used so far in bulk heterojunction structures. We report here cobalt sulfide (CoS) to be a promising hole collecting material deposited by convenient and room temperature electrodeposition. By simply tuning the CoS electrodeposition parameters, power conversion efficiencies similar (within 15%) to a reference structure with PEDOT:PSS were obtained.

  18. Direct evidence for charge stripes in a layered cobalt oxide.

    PubMed

    Babkevich, P; Freeman, P G; Enderle, M; Prabhakaran, D; Boothroyd, A T

    2016-01-01

    Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3Sr1/3CoO4, an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hourglass shape of the magnetic spectrum previously observed in neutron-scattering measurements of La2-xSrxCoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations. PMID:27212023

  19. Photorefractive properties of cobalt-doped strontium barium niobate crystals

    SciTech Connect

    Bogodaev, N V; Ivleva, Lyudmila I; Lykov, P A; Polozkov, N M; Osiko, Vyacheslav V

    1999-05-31

    The two-wave interaction (at {lambda} = 488 nm) in strontium barium niobate crystals doped with cobalt ions (Co:SBN) was studied. The experimental dependences of the gain coefficient on the grating period and of the grating response time on the writing beam intensity were used to calculate the Debye screening length, the diffusion length, the dark conductivity, and the effective concentration of carrier traps for a series of Co:SBN crystals with different dopant concentrations. The crystals were shown to have high coupling coefficients ({Gamma} = 33 cm{sup -1}) and short optical response times ({tau} = 140 ms for I = 1 W cm{sup -2} ). This, in combination with a high photorefractive sensitivity (S = 39 cm{sup 2} J{sup -1} ), determines the efficiency of their use in the storage of optical information and in laser phase conjugation. (nonlinear optical phenomena)

  20. Magnetic Cobalt Ferrite Nanocrystals For an Energy Storage Concentration Cell.

    PubMed

    Dai, Qilin; Patel, Ketan; Donatelli, Greg; Ren, Shenqiang

    2016-08-22

    Energy-storage concentration cells are based on the concentration gradient of redox-active reactants; the increased entropy is transformed into electric energy as the concentration gradient reaches equilibrium between two half cells. A recyclable and flow-controlled magnetic electrolyte concentration cell is now presented. The hybrid inorganic-organic nanocrystal-based electrolyte, consisting of molecular redox-active ligands adsorbed on the surface of magnetic nanocrystals, leads to a magnetic-field-driven concentration gradient of redox molecules. The energy storage performance of concentration cells is dictated by magnetic characteristics of cobalt ferrite nanocrystal carriers. The enhanced conductivity and kinetics of redox-active electrolytes could further induce a sharp concentration gradient to improve the energy density and voltage switching of magnetic electrolyte concentration cells. PMID:27440206

  1. Magnetic properties engineering of nanopatterned cobalt antidot arrays

    NASA Astrophysics Data System (ADS)

    Kaidatzis, Andreas; del Real, Rafael P.; Alvaro, Raquel; Palma, Juan Luis; Anguita, José; Niarchos, Dimitrios; Vázquez, Manuel; Escrig, Juan; García-Martín, José Miguel

    2016-05-01

    We report on the study of arrays of 60 nm wide cobalt antidots, nanopatterned using focused ion beam milling. Square and hexagonal symmetry arrays have been studied, with varying antidot densities and lattice constant from 150 up to 300 nm. We find a strong increase of the arrays’ magnetic coercivity with respect to the unpatterned film, which is monotonic as the antidot density increases. Additionally, there is a strong influence of the array symmetry to the in-plane magnetic anisotropy: square arrays exhibit fourfold symmetry and hexagonal arrays exhibit sixfold symmetry. The above findings are corroborated by magnetic imaging and micromagnetic modeling, which show the magnetic structure of the arrays to depend strongly on the array morphology.

  2. Single-electron tunneling at room temperature in cobalt nanoparticles

    NASA Astrophysics Data System (ADS)

    Graf, H.; Vancea, J.; Hoffmann, H.

    2002-02-01

    We report on the observation of the Coulomb blockade with Coulomb staircases at room temperature in cobalt nanoparticles, with sizes ranging between 1 and 4 nm. A monolayer of these particles is supported by a thin 1-2 nm thick Al2O3 film, deposited on a smooth Au(111) surface. The local electrical transport on isolated Co clusters was investigated with a scanning tunneling microscope (STM). The tunnel contact of the STM tip allowed us to observe single-electron tunneling in the double barrier system STM-tip/Co/Al2O3/Au. Very high values of the Coulomb blockade of up to 1.0 V were reproducibly measured at room temperature on different particles with this setup. The current-voltage characteristics fit well by simulations based on the orthodox theory of single-electron tunneling.

  3. Atomic cobalt on nitrogen-doped graphene for hydrogen generation

    NASA Astrophysics Data System (ADS)

    Fei, Huilong; Dong, Juncai; Arellano-Jiménez, M. Josefina; Ye, Gonglan; Dong Kim, Nam; Samuel, Errol L. G.; Peng, Zhiwei; Zhu, Zhuan; Qin, Fan; Bao, Jiming; Yacaman, Miguel Jose; Ajayan, Pulickel M.; Chen, Dongliang; Tour, James M.

    2015-10-01

    Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts.

  4. Magnetic relaxation of diluted and self-assembled cobalt nanocrystals

    NASA Astrophysics Data System (ADS)

    Zhang, X. X.; Wen, G. H.; Xiao, Gang; Sun, Shouheng

    2003-04-01

    We have studied the magnetic relaxation of monodispersed 4 nm cubic ɛ-cobalt nanocrystals in both randomly oriented and pre-aligned assemblies. The blocking temperature TB, for the closely packed Co nanocrystal assemblies, is 30% higher than that of the highly diluted and well-dispersed Co nanocrystal-organic composites. This increase is attributed to the strong magnetic dipole interaction induced from the close packing of the nanocrystals. It is found that the frequency-dependent susceptibility data, obtained from the diluted samples, can be fitted to the half-circle Argand Diagrams, indicating a single barrier (or very narrow energy distribution) of the nanocrystals. This agrees well with the physical observation from TEM that the nanocrystals are monodispersed. The long time magnetic relaxation measurements reveal that energy barrier distribution in a pre-aligned nanocrystal assembly is significantly different from that in a randomly oriented one.

  5. Direct evidence for charge stripes in a layered cobalt oxide

    PubMed Central

    Babkevich, P.; Freeman, P. G.; Enderle, M.; Prabhakaran, D.; Boothroyd, A. T.

    2016-01-01

    Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3Sr1/3CoO4, an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hourglass shape of the magnetic spectrum previously observed in neutron-scattering measurements of La2−xSrxCoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations. PMID:27212023

  6. Electrodeposited cobalt sulfide hole collecting layer for polymer solar cells

    NASA Astrophysics Data System (ADS)

    Zampetti, Andrea; De Rossi, Francesca; Brunetti, Francesca; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

    2014-08-01

    In polymer solar cells based on the blend of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester, the hole collecting layer has to be endowed with its ionization potential close to or greater than that of P3HT (˜5 eV). Conductive polymer blends such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and metal oxides such as vanadium pentoxide (V2O5) and molybdenum trioxide (MoO3) satisfy this requirement and have been the most common materials used so far in bulk heterojunction structures. We report here cobalt sulfide (CoS) to be a promising hole collecting material deposited by convenient and room temperature electrodeposition. By simply tuning the CoS electrodeposition parameters, power conversion efficiencies similar (within 15%) to a reference structure with PEDOT:PSS were obtained.

  7. Cobalt iontophoresis of sensory nerves in the rat lung.

    PubMed

    El-Bermani, A W; Chang, T L

    1979-02-01

    By iontophoretically introducing, first, cobalt and, subsequently, sulfide ions into the vagus nerve, it is possible to trace sensory nerves to their endings in the rat lung. Nerve fibers and terminals are found predominantly in the adventitia of the airways and blood vessels. Some nerves are found in the submucosa of the bronchi and bronchioles. Some are found in the cardiac muscle on the periphery of pulmonary veins, and a few nerves are seen to end among smooth muslces of the blood vessels and the airways. At least three types of nerve endings can be identified at the light microscopic level: (1) free nerve endings; (2) brush-like endings; (3) knob-like terminals. PMID:760496

  8. An evaluated neutronic data file for elemental cobalt

    SciTech Connect

    Guenther, P.; Lawson, R.; Meadows, J.; Sugimoto, M.; Smith, A.; Smith, D.; Howerton, R.

    1988-08-01

    A comprehensive evaluated neutronic data file for elemental cobalt is described. The experimental data base, the calculational methods, the evaluation techniques and judgments, and the physical content are outlined. The file contains: neutron total and scattering cross sections and associated properties, (n,2n) and (n,3n) processes, neutron radiative capture processes, charged-particle-emission processes, and photon-production processes. The file extends from 10/sup /minus/5/ eV to 20 MeV, and is presented in the ENDF/B-VI format. Detailed attention is given to the uncertainties and correlations associated with the prominent neutron-induced processes. The numerical contents of the file have been transmitted to the National Nuclear Data Center, Brookhaven National Laboratory. 143 refs., 16 figs., 5 tabs.

  9. Periodic magnetic domains in single-crystalline cobalt filament arrays

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Wang, Fan; Jia, Fei; Li, Jingning; Liu, Kai; Huang, Sunxiang; Luan, Zhongzhi; Wu, Di; Chen, Yanbin; Zhu, Jianmin; Peng, Ru-Wen; Wang, Mu

    2016-02-01

    Magnetic structures with controlled domain wall pattern may be applied as potential building blocks for three-dimensional magnetic memory and logic devices. Using a unique electrochemical self-assembly method, we achieve regular single-crystalline cobalt filament arrays with specific geometric profile and crystallographic orientation, and the magnetic domain configuration can be conveniently tailored. We report the transition of periodic antiparallel magnetic domains to compressed vortex magnetic domains depending on the ratio of height to width of the wires. A "phase diagram" is obtained to describe the dependence of the type of magnetic domain and the geometrical profiles of the wires. Magnetoresistance of the filaments demonstrates that the contribution of a series of 180∘ domain walls is over 0.15 % of the zero-field resistance ρ (H =0 ) . These self-assembled magnetic nanofilaments, with controlled periodic domain patterns, offer an interesting platform to explore domain-wall-based memory and logic devices.

  10. Reflection of cold atoms by a cobalt single crystal

    NASA Astrophysics Data System (ADS)

    Rosenbusch, P.; Retter, J. A.; Hall, B. V.; Hinds, E. A.; Lison, F.; Haubrich, D.; Meschede, D.

    2000-05-01

    We have demonstrated that a cobalt single crystal can be used to make a remarkably smooth retro-reflector for cold paramagnetic atoms. The crystal is cut so that its surface lies in the (0001) plane and the atoms are reflected by the magnetic field above the surface due to the self-organized pattern of magnetic domains in the material. We find that the reflectivity for suitably polarized atoms exceeds 90% and may well be unity. We use the angular spread of a reflected atom cloud to measure the roughness of the mirror. We find that the angular variation of the equivalent hard reflecting surface is (3.1±0.3°)rms for atoms dropped onto the mirror from a height of 2 cm.

  11. Controlled crystalline structure and surface stability of cobalt nanocrystals.

    PubMed

    Bao, Yuping; Beerman, Michael; Pakhomov, Alexandre B; Krishnan, Kannan M

    2005-04-21

    The synthesis of monodispersed 10 nm cobalt nanocrystals with controlled crystal morphology and investigation of the surface stability of these nanocrystals are described. Depending on the surfactants used, single crystalline or multiple grain nanocrystals can be reproducibly produced. The relative surface stability of these nanocrystals is analyzed using the temperature dependences of the dc magnetic susceptibility. The novel method, which allows sensitive monitoring of the surface stability, is based on the observation that, with particle oxidation, an anomalous peak appears at 8 K in zero-field-cooled magnetization measurements. It is found that the surfactant protective layer is more important for long-term stability at room temperature, while the high-temperature oxidation rate is controlled by the crystal morphology of the nanoparticles. PMID:16851825

  12. Atomic cobalt on nitrogen-doped graphene for hydrogen generation

    PubMed Central

    Fei, Huilong; Dong, Juncai; Arellano-Jiménez, M. Josefina; Ye, Gonglan; Dong Kim, Nam; Samuel, Errol L.G.; Peng, Zhiwei; Zhu, Zhuan; Qin, Fan; Bao, Jiming; Yacaman, Miguel Jose; Ajayan, Pulickel M.; Chen, Dongliang; Tour, James M.

    2015-01-01

    Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts. PMID:26487368

  13. Atomic cobalt on nitrogen-doped graphene for hydrogen generation.

    PubMed

    Fei, Huilong; Dong, Juncai; Arellano-Jiménez, M Josefina; Ye, Gonglan; Dong Kim, Nam; Samuel, Errol L G; Peng, Zhiwei; Zhu, Zhuan; Qin, Fan; Bao, Jiming; Yacaman, Miguel Jose; Ajayan, Pulickel M; Chen, Dongliang; Tour, James M

    2015-01-01

    Reduction of water to hydrogen through electrocatalysis holds great promise for clean energy, but its large-scale application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. Here we report an electrocatalyst for hydrogen generation based on very small amounts of cobalt dispersed as individual atoms on nitrogen-doped graphene. This catalyst is robust and highly active in aqueous media with very low overpotentials (30 mV). A variety of analytical techniques and electrochemical measurements suggest that the catalytically active sites are associated with the metal centres coordinated to nitrogen. This unusual atomic constitution of supported metals is suggestive of a new approach to preparing extremely efficient single-atom catalysts. PMID:26487368

  14. Large-scale synthesis and photoluminescence of cobalt tungstate nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Cuiling; Guo, Donglin; Hu, Chenguo; Chen, Yanxue; Liu, Hong; Zhang, Hulin; Wang, Xue

    2013-01-01

    Single-crystalline wolframite-type monoclinic structure cobalt tungstate (CoWO4) nanowires were obtained by a solvothermal method at 180 °C for 24 h with a width of 20 nm and length of 200 to 400 nm. Besides the strong blue-green light emission at 10-250 K, we found much stronger and broader near-infrared emission ranging from 700-1000 nm at about 300 K under the excitation wavelength of 325 nm. The emission and the dependence of emission intensity on temperature are discussed by introducing the effect of Co vacancies. This near-infrared emission material might have potential applications in infrared detection or stealth technology.

  15. Magnetic and ultrasonic studies on stable cobalt ferrite magnetic nanofluid.

    PubMed

    Nabeel Rashin, M; Hemalatha, J

    2014-03-01

    Stable cobalt ferrite nanofluids of various concentrations have been prepared through co-precipitation method. Structural and morphological studies of nanoparticles are made with the help of X-ray diffraction technique and Transmission Electron Microscope respectively and it is found that the particles exhibit face centered cubic structure with an average size of 14 nm. The magnetic properties of the nanofluids have been analyzed at room temperature which revealed ferromagnetic behavior and also the very low value of coupling constant which ensures the negligible interparticle interaction in the absence of magnetic field. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. The temperature effects are explained with the help of open and close-packed water structure. The inter particle interactions of surface modified CoFe2O4 particles and the cluster formation at higher concentrations are realized through the variations in ultrasonic parameters. PMID:24188514

  16. Aqua­bromidobis(dimethyl­glyoximato)cobalt(III)

    PubMed Central

    Meera, Parthasarathy; Amutha Selvi, Madhavan; Jothi, Pachaimuthu; Dayalan, Arunachalam

    2011-01-01

    In the title complex, [CoBr(C4H7N2O2)2(H2O)], a crystallo­graphic mirror plane bis­ects the mol­ecule, perpendicular to the glyoximate ligands. The geometry around the cobalt(III) atom is approximately octa­hedral with the four glyoximate N atoms forming the square base. A bromide ion and the O atom of a water mol­ecule occupy the remaining coordination sites. The N—Co—N bite angles are 82.18 (4) and 80.03 (16)°. The glyoximate moieties form strong intra­molecular O—H⋯O hydrogen bonds. The coordinated water mol­ecule forms an inter­molecular O—H⋯O hydrogen bond with a glyoximate O atom, thereby generating supra­molecular chains parallel to [010]. PMID:21753964

  17. Catalytic Oxygen Evolution by Cobalt Oxido Thin Films.

    PubMed

    Bediako, D Kwabena; Ullman, Andrew M; Nocera, Daniel G

    2016-01-01

    The contemporary demand to generate fuels from solar energy has stimulated intense effort to develop water splitting catalysts that can be coupled to light-absorbing materials. Cobalt oxido catalyst (Co-OECs) films deposited from buffered Co(II) solutions have emerged as arguably the most studied class of heterogeneous oxygen evolution catalysts. The interest in these materials stems from their formation by self-assembly, their self-healing properties, and their promising catalytic activity under a variety of conditions. The structure and function of these catalysts are reviewed here together with studies of molecular Co-O cluster compounds, which have proven invaluable in elucidating the chemistry of the Co-OECs. PMID:26245626

  18. Total body irradiation with a sweeping {sup 60}Cobalt beam

    SciTech Connect

    Hussein, S.; El-Khatib, E.

    1995-09-30

    This article describes the physical, technical, and dosimetric aspects of total body irradiation (TBI). The continuous head swivel motion of a standard {sup 60}Cobalt unit has been used to obtain a sweeping beam that encompases the entire length of the patient in TBI. A perspex beam flattener designed to remove the inverse square fall-off in beam intensity along the sweep axis provides a 90% field length of 200 cm in air at a treatment source-to-skin distance of 160 cm. The anterior-posterior parallel pair setup permits accurate placement of customized lead compensators to limit the dose to lungs. Measured beam profiles, dose buildup curves, and percentage depth dose for the technique are presented. With compensators in place, the variation in lung dose is shown to be within {plus_minus}5% of the prescribed tumor dose. 10 refs., 5 figs.

  19. Direct evidence for charge stripes in a layered cobalt oxide

    NASA Astrophysics Data System (ADS)

    Babkevich, P.; Freeman, P. G.; Enderle, M.; Prabhakaran, D.; Boothroyd, A. T.

    2016-05-01

    Recent experiments indicate that static stripe-like charge order is generic to the hole-doped copper oxide superconductors and competes with superconductivity. Here we show that a similar type of charge order is present in La5/3Sr1/3CoO4, an insulating analogue of the copper oxide superconductors containing cobalt in place of copper. The stripe phase we have detected is accompanied by short-range, quasi-one-dimensional, antiferromagnetic order, and provides a natural explanation for the distinctive hourglass shape of the magnetic spectrum previously observed in neutron-scattering measurements of La2-xSrxCoO4 and many hole-doped copper oxide superconductors. The results establish a solid empirical basis for theories of the hourglass spectrum built on short-range, quasi-static, stripe correlations.

  20. Itinerant Magnetism in Yttrium COBALT(2) and Related Systems

    NASA Astrophysics Data System (ADS)

    Michels, Donald William

    1990-01-01

    We have studied the pseudo-binary systems Y(Co,Al) _2, Y(Co,Si)_2, Y_{.7}Sc_ {.3}(Co,Al)_2, and Sc(Co,Si)_2. Measurements were made of magnetic susceptibility from 2 to 400K, resistivity from 1.5 to 300K, specific heat from 1.5 to 25K, and lattice constant at room temperature. In addition, some of the same measurements were made for (Y,Sc)Co_2 , Zr(Co,Al)_2 and Zr(Co,Si) _2. YCo_2 is a strongly paramagnetic system with a broad maximum in magnetic susceptibility versus temperature. A functional form for this maximum has been derived by proponents of fermi liquid theory. YCo _2 (and some related systems described in this work) can be driven to weak itinerant ferromagnetism by partial substitution of aluminum for cobalt. This can be explained qualitatively by either rigid band depletion or lattice expansion, either of which should increase the density of states at the fermi level. In this study we found that lattice expansion driven from the cobalt site was necessary for the appearance of ferromagnetism. Depletion of the d-electron band shifted the magnetic susceptibility maximum to lower temperatures without causing ferromagnetism; thus a rigid band model would appear inappropriate for ferromagnetism in these systems. The behavior of susceptibility in this study (as a function of impurity concentration) may represent an example of a modification of fermi liquid theory proposed in 1968, and correlates with the impurity behavior observed for the resistivity and specific heat. In addition, the temperature dependence of the magnetic susceptibility of YCo_2 was found to have a strong field dependence at low magnetic fields. It is shown that this dependence may be explained by the presence of a ferromagnetic impurity with a high ordering temperature.

  1. Cobalt excretion test for the assessment of body iron stores.

    PubMed

    Sorbie, J; Olatunbosun, D; Corbett, W E; Valberg, L S

    1971-05-01

    Iron absorption is under delicate control and the level of absorption is adjusted to comply with the body's need for iron. To measure the intestinal setting for iron absorption, and thereby indirectly assess body iron requirements, cobaltous chloride labelled with (57)Co or (60)Co was given by mouth and the percentage of the test dose excreted in the urine in 24 hours was measured in a gamma counter. Seventeen control subjects with normal iron stores excreted 18% (9-23%) of the dose. Increased excretion, 31% (23-42%), was found in 10 patients with iron deficiency anemia and in 15 patients with depleted iron stores in the absence of anemia. In contrast, 12 patients with anemia due to causes other than iron deficiency excreted amounts of radiocobalt within the normal control range. In patients with iron deficiency, replenishment of iron stores by either oral or parenteral iron caused the previously high results to return to normal.Excretion of the test dose was normal in portal cirrhosis with normal iron stores but it was markedly increased in patients with cirrhosis complicated by either iron deficiency or endogenous iron overload. It was also raised in primary hemochromatosis. Excretion of the dose was reduced in gluten-sensitive enteropathy. Gastrointestinal surgery and inflammatory disease of the lower small intestine had no effect on the results except that some patients with steatorrhea had diminished excretion.The cobalt excretion test provides the clinician with a tool for the assessment of iron absorption, the detection of a reduction in body iron stores below the level that is normal for the subject in question, the differentiation of iron deficiency anemia from anemia due to other causes, and the investigation of patients with iron-loading disorders. PMID:5578125

  2. Physical and electrochemical study of cobalt oxide nano- and microparticles

    SciTech Connect

    Alburquenque, D.; Vargas, E.; Denardin, J.C.; Escrig, J.; Marco, J.F.; Gautier, J.L.

    2014-07-01

    Cobalt oxide nanocrystals of size 17–21 nm were synthesized by a simple reaction between cobalt acetate (II) and dodecylamine. On the other hand, micrometric Co{sub 3}O{sub 4} was prepared using the ceramic method. The structural examination of these materials was performed using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM and HRTEM). XRD studies showed that the oxides were pure, well-crystallized, spinel cubic phases with a-cell parameter of 0.8049 nm and 0.8069 nm for the nano and micro-oxide, respectively. The average particle size was 19 nm (nano-oxide) and 1250 μm (micro-oxide). Morphological studies carried out by SEM and TEM analyses have shown the presence of octahedral particles in both cases. Bulk and surface properties investigated by X-ray photoelectron spectroscopy (XPS), point zero charge (pzc), FTIR and cyclic voltammetry indicated that there were no significant differences in the composition on both materials. The magnetic behavior of the samples was determined using a vibrating sample magnetometer. The compounds showed paramagnetic character and no coercivity and remanence in all cases. Galvanostatic measurements of electrodes formed with nanocrystals showed better performance than those built with micrometric particles. - Highlights: • Spinel Co{sub 3}O{sub 4} nanoparticles and microparticles with same structure but with different cell parameters, particle size and surface area were synthesized. • Oxide nanoparticles showed better electrochemical behavior than micrometric ones due to area effect.

  3. Impact of cadmium, cobalt and nickel on sequence-specific DNA binding of p63 and p73 in vitro and in cells

    SciTech Connect

    Adámik, Matej; Bažantová, Pavla; Navrátilová, Lucie; Polášková, Alena; Pečinka, Petr; Holaňová, Lucie; Brázdová, Marie

    2015-01-02

    Highlights: • DNA binding of p53 family core domains is inhibited by cadmium, cobalt and nickel. • Binding to DNA protects p53 family core domains from metal induced inhibition. • Cadmium, cobalt and nickel induced inhibition was reverted by EDTA in vitro. - Abstract: Site-specific DNA recognition and binding activity belong to common attributes of all three members of tumor suppressor p53 family proteins: p53, p63 and p73. It was previously shown that heavy metals can affect p53 conformation, sequence-specific binding and suppress p53 response to DNA damage. Here we report for the first time that cadmium, nickel and cobalt, which have already been shown to disturb various DNA repair mechanisms, can also influence p63 and p73 sequence-specific DNA binding activity and transactivation of p53 family target genes. Based on results of electrophoretic mobility shift assay and luciferase reporter assay, we conclude that cadmium inhibits sequence-specific binding of all three core domains to p53 consensus sequences and abolishes transactivation of several promoters (e.g. BAX and MDM2) by 50 μM concentrations. In the presence of specific DNA, all p53 family core domains were partially protected against loss of DNA binding activity due to cadmium treatment. Effective cadmium concentration to abolish DNA–protein interactions was about two times higher for p63 and p73 proteins than for p53. Furthermore, we detected partial reversibility of cadmium inhibition for all p53 family members by EDTA. DTT was able to reverse cadmium inhibition only for p53 and p73. Nickel and cobalt abolished DNA–p53 interaction at sub-millimolar concentrations while inhibition of p63 and p73 DNA binding was observed at millimolar concentrations. In summary, cadmium strongly inhibits p53, p63 and p73 DNA binding in vitro and in cells in comparison to nickel and cobalt. The role of cadmium inhibition of p53 tumor suppressor family in carcinogenesis is discussed.

  4. Shock sensitivity of the explosive 2-(5-Cyanotetrazolato) Pentaamine Cobalt(III) Perchlorate (CP)

    SciTech Connect

    Fogelson, D.J.; Schwarz, A.C.

    1982-01-01

    The inorganic explosive, 2-(5-Cyanotetrazolato) Pentaamine Cobalt(III) Perchlorate, more commonly designated CP, is used in a number of hot-wire initiated deflagration-to-detonation detonators. Analyses of the safety aspects of these detonators are dependent upon utilizing shock initiation sensitivity data on this explosive where sensitivity is defined as the amplitude (P) and duration (tau) of the shock stimulus which produces a 50% probability of initiation. In this work the shock sensitivity of CP powder pressed to 1.50 Mg/m/sup 3/ bulk density was determined using flyer plate impact techniques which provided pulse durations of 0.17 ..mu..s and 0.23 ..mu..s and pulse amplitudes of 0.8 to 2.3 GPa. Impact tests were conducted in air and vacuum, and with flyers of different area. It was necessary to develop a new test technique to generate flyer velocities to bracket the threshold of initiation for this study. This was done by electrically exploding a metal foil against a lucite shock-moderator from which a plastic flyer lifted off at a controlled velocity. The energy source was a large capacitor bank and provided flyer velocities repeatable within 7% and with a planarity of 30 ns or less. The pressure thresholds for detonation of CP were found to be 1.75 GPa and 1.40 GPa, for pulse durations of 0.17 ..mu..s and 0.23 ..mu..s respectively. There was no discernible difference in response between samples tested in air or vacuum, or with flyers of different area, within experimental error.

  5. Fluorescence spectrometry for quantitative characterization of cobalt(II) complexation by Leonardite humic acid.

    PubMed

    Monteil-Rivera, Fanny; Dumonceau, Jacques

    2002-11-01

    Quenching of the fluorescence of a Leonardite humic acid by Co(II) has been studied at different pH. The interaction was monitored by emission fluorescence and by synchronous fluorescence with two different offsets (deltalambda=20 and 80 nm). It was found that synchronous fluorescence performed with the smaller offset resolves the individual components of the heterogeneous material better than emission or synchronous fluorescence performed with the larger offset. Enhancement of the signal induced by Cobalt(II) complexation resulted in more complex behavior for measurements performed by synchronous fluorescence with an offset of 20 nm, however. The quenching profiles obtained for pH 5.0, 6.0, and 7.0 ([KNO(3)]=0.1 mol L(-1); [LHA]=3.3 mg(C) L(-1); [Co(II)]=1.0 x 10(-6)-1.6 x 10 (-3) mol L(-1)) by emission and synchronous (deltalambda=80 nm) fluorescence were analyzed by two methods: 1. a non-linear least-squares procedure that leads to conditional constants; and 2. a pH-dependent discrete logK spectrum model that leads to stability constants. The first method resulted in poor fitting and unreasonable values for maximum capacities. The second procedure resulted in smooth fitting that accounted well for the pH changes when results for pH 6.0 and 5.0 were predicted by use of the four values of logK(Co)(i) (4.31, 3.76, 7.32, and 7.67 corresponding to the four sites (i) of the respective pKa(i) values 4, 6, 8, and 10) calculated at pH 7.0 for the equilibrium PMID:12458428

  6. Synthesis, Characterization, and Use of a Cobalt(II) Complex as an NMR Shift Reagent.

    ERIC Educational Resources Information Center

    Goff, Harold M.; And Others

    1982-01-01

    Describes procedures for preparing acetylacetonate complex of cobalt(II), followed by spectrophotometric analysis to characterize the material, with additional characterization methods supplied by students to provide open-ended dimension for the experiment. (SK)

  7. Fischer-Tropsch activity for non-promoted cobalt-on-alumina catalysts

    DOEpatents

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2001-01-01

    Cobalt catalysts, and processes employing these inventive catalysts, for hydrocarbon synthesis. The inventive catalyst comprises cobalt on an alumina support and is not promoted with any noble or near noble metals. In one aspect of the invention, the alumina support preferably includes a dopant in an amount effective for increasing the activity of the inventive catalyst. The dopant is preferably a titanium dopant. In another aspect of the invention, the cobalt catalyst is preferably reduced in the presence of hydrogen at a water vapor partial pressure effective to increase the activity of the cobalt catalyst for hydrocarbon synthesis. The water vapor partial pressure is preferably in the range of from 0 to about 0.1 atmospheres.

  8. Structure of catabolite activator protein with cobalt(II) and sulfate

    SciTech Connect

    Rao, Ramya R.; Lawson, Catherine L.

    2014-04-15

    The crystal structure of E. coli catabolite activator protein with bound cobalt(II) and sulfate ions at 1.97 Å resolution is reported. The crystal structure of cyclic AMP–catabolite activator protein (CAP) from Escherichia coli containing cobalt(II) chloride and ammonium sulfate is reported at 1.97 Å resolution. Each of the two CAP subunits in the asymmetric unit binds one cobalt(II) ion, in each case coordinated by N-terminal domain residues His19, His21 and Glu96 plus an additional acidic residue contributed via a crystal contact. The three identified N-terminal domain cobalt-binding residues are part of a region of CAP that is important for transcription activation at class II CAP-dependent promoters. Sulfate anions mediate additional crystal lattice contacts and occupy sites corresponding to DNA backbone phosphate positions in CAP–DNA complex structures.

  9. Biological and protein-binding studies of newly synthesized polymer-cobalt(III) complexes.

    PubMed

    Vignesh, G; Pradeep, I; Arunachalam, S; Vignesh, S; Arthur James, R; Arun, R; Premkumar, K

    2016-03-01

    The polymer-cobalt(III) complexes, [Co(bpy)(dien)BPEI]Cl3 · 4H2O (bpy = 2,2'-bipyridine, dien = diethylentriamine, BPEI = branched polyethyleneimine) were synthesized and characterized. The interaction of these complexes with human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under physiological conditions using various physico-chemical techniques. The results reveal that the fluorescence quenching of serum albumins by polymer-cobalt(III) complexes took place through static quenching. The binding of these complexes changed the molecular conformation of the protein considerably. The polymer-cobalt(III) complex with x = 0.365 shows antimicrobial activity against several human pathogens. This complex also induces cytotoxicity against MCF-7 through apoptotic induction. However, further studies are needed to decipher the molecular mode of action of polymer-cobalt(III) complex and for its possible utilization in anticancer therapy. PMID:26278128

  10. Impedance spectroscopy studies in cobalt ferrite-reduced graphene oxide nanocomposite

    NASA Astrophysics Data System (ADS)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2016-05-01

    (1-x)Cobalt ferrite-(x)reduced graphene oxidenanocomposites with x=0, 0.1, 0.2 and 0.3 were prepared by the ultrasonic method. The crystal symmetry modification due to reduced graphene oxide and cobalt ferrite interaction has been studied by employing the X-ray diffraction technique. Morphology of the samples was studied by the Field emission scanning electron microscopy (FE-SEM). Study on electrical properties of the cobalt ferrite-reduced graphene oxide nanocomposites explores the possible application of these composites as anode material. Impedance decreases with an increase in frequency as well as temperature, which supports an increase in ac electrical conductivity. The modified Debye relaxation model can explain the behavior of impedance in cobalt ferrite-reduced graphene oxide nanocomposites.

  11. Cobalt-catalysed site-selective intra- and intermolecular dehydrogenative amination of unactivated sp3 carbons

    PubMed Central

    Wu, Xuesong; Yang, Ke; Zhao, Yan; Sun, Hao; Li, Guigen; Ge, Haibo

    2015-01-01

    Cobalt-catalysed sp2 C–H bond functionalization has attracted considerable attention in recent years because of the low cost of cobalt complexes and interesting modes of action in the process. In comparison, much less efforts have been devoted to the sp3 carbons. Here we report the cobalt-catalysed site-selective dehydrogenative cyclization of aliphatic amides via a C–H bond functionalization process on unactivated sp3 carbons with the assistance of a bidentate directing group. This method provides a straightforward synthesis of monocyclic and spiro β- or γ-lactams with good to excellent stereoselectivity and functional group tolerance. In addition, a new procedure has been developed to selectively remove the directing group, which enables the synthesis of free β- or γ-lactam compounds. Furthermore, the first cobalt-catalysed intermolecular dehydrogenative amination of unactivated sp3 carbons is also realized. PMID:25753366

  12. Influence of silicon on friction and wear of iron-cobalt alloys

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Brainard, W. A.

    1972-01-01

    Sliding friction and wear experiments were conducted with ternary ordered alloys of iron and cobalt containing various amounts of silicon to 5 weight percent. The friction and wear of these alloys were compared to those for binary iron-cobalt alloys in the ordered and disordered states and to those for the conventionally used bearing material, 440-C. Environments in which experiments were conducted included air, argon, and 0.25percent stearic acid in hexadecane. Results indicate that a ternary iron - cobalt - 5-percent-silicon alloy exhibits lower friction and wear than the simple binary iron-cobalt alloy. It exhibits lower wear than 440-C in all three environments. Friction was lower for the alloy in argon than in air. Auger analysis of the surface of the ternary alloy indicated segregation of silicon at the surface as a result of sliding.

  13. A Photoinduced Cobalt-Catalyzed Synthesis of Pyrroles through in Situ-Generated Acylazirines.

    PubMed

    Pusch, Stefan; Kowalczyk, Danuta; Opatz, Till

    2016-05-20

    Tetrasubstituted pyrroles can be synthesized in a one-pot procedure from isoxazoles. The process includes the photoinduced in situ formation of acylazirines combined with a subsequent cobalt(II)-catalyzed ring expansion with 1,3-diketones. PMID:27081704

  14. Cobalt oxide nanoparticles can enter inside the cells by crossing plasma membranes

    PubMed Central

    Bossi, Elena; Zanella, Daniele; Gornati, Rosalba; Bernardini, Giovanni

    2016-01-01

    The ability of nanoparticles (NPs) to be promptly uptaken by the cells makes them both dangerous and useful to human health. It was recently postulated that some NPs might cross the plasma membrane also by a non-endocytotic pathway gaining access to the cytoplasm. To this aim, after having filled mature Xenopus oocytes with Calcein, whose fluorescence is strongly quenched by divalent metal ions, we have exposed them to different cobalt NPs quantifying quenching as evidence of the increase of the concentration of Co2+ released by the NPs that entered into the cytoplasm. We demonstrated that cobalt oxide NPs, but not cobalt nor cobalt oxide NPs that were surrounded by a protein corona, can indeed cross plasma membranes. PMID:26924527

  15. Theoretical studies of the structure and properties of cobalt-substituted aluminophosphates

    SciTech Connect

    Henson, N.J.; Hay, P.J.; Redondo, A.

    1998-12-31

    Quantum chemical and atomistic forcefield based methods have been used to investigate models for the substitution of cobalt into aluminophosphate molecular sieves. Atomistic methods based on the Mott-Littleton approach were used to develop approximate models for cobalt substituted at the aluminum site in the AlPO{sub 4}-5 structure and from these structures clusters were constructed for quantum chemical calculations. The effect of termination with both hydride and hydroxyl groups was assessed. Full and constrained geometry optimization were performed to obtain geometrical parameters for the models which were compared to experimental data. Further calculations were performed on adducts consisting of the cluster models and small molecules to determine whether direct binding to the cobalt center is possible. The calculations were used to determine the stability of models proposed in the literature. Cobalt-substituted aluminophosphates have been shown to be active catalysts in a number of reactions including the homogeneous oxidation of cyclohexane to cyclohexanone.

  16. Preparation and Properties of Monodisperse Magnetic Cobalt Colloids Grafted with Polyisobutene.

    PubMed

    Pathmamanoharan; Philipse

    1998-09-15

    A single-step method to synthesize monodisperse metallic cobalt particles of diameter around 8 nm is described. The particles are sterically stabilized by modified polyisobutene and form stable ferrofluids in toluene. The core-shell cobalt spheres have a narrow size distribution and are nonaggregated. Various techniques, such as infrared spectroscopy, X-ray diffraction, and elemental analysis establishes the presence of grafted modified polyisobutene on the surface of cobalt particles. The hydrodynamic thickness of the grafted polyisobutene calculated from sedimentation and viscosity measurements and independently from the dynamic light scattering is ca. 10 nm. The dependence of magnetization has been measured for ferrofluid, showing superparamagnetic behavior above 247 K. Due to anisotropy, superposition of magnetic curves is not observed below this temperature. The concentration dependence of the sedimentation coefficient agrees qualitatively with the theory for dipolar spheres. SAXS data on concentrated ferrofluid dispersion indicate interpenetration of polyisobutene chains grafted to the cobalt particles. Copyright 1998 Academic Press. PMID:9735197

  17. The surface sulfur doping induced enhanced performance of cobalt catalysts in oxygen evolution reactions.

    PubMed

    Al-Mamun, Mohammad; Zhu, Zhengju; Yin, Huajie; Su, Xintai; Zhang, Haimin; Liu, Porun; Yang, Huagui; Wang, Dan; Tang, Zhiyong; Wang, Yun; Zhao, Huijun

    2016-08-01

    A novel surface sulfur (S) doped cobalt (Co) catalyst for the oxygen evolution reaction (OER) is theoretically designed through the optimisation of the electronic structure of highly reactive surface atoms which is also validated by electrocatalytic OER experiments. PMID:27377872

  18. 33 CFR 67.50-50 - Seventeenth Coast Guard District.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Seventeenth Coast Guard District. 67.50-50 Section 67.50-50 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Regulations § 67.50-50 Seventeenth Coast Guard District. (a) Description. See § 3.85-1 of this chapter....

  19. 33 CFR 67.50-50 - Seventeenth Coast Guard District.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Seventeenth Coast Guard District. 67.50-50 Section 67.50-50 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Regulations § 67.50-50 Seventeenth Coast Guard District. (a) Description. See § 3.85-1 of this chapter....

  20. 33 CFR 67.50-50 - Seventeenth Coast Guard District.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Seventeenth Coast Guard District. 67.50-50 Section 67.50-50 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Regulations § 67.50-50 Seventeenth Coast Guard District. (a) Description. See § 3.85-1 of this chapter....