Search results for "Cobalt"
showing 10 items of 1098 documents
Electrochemical characterization of cobalt cordierites attached to paraffin-impregnated graphite electrodes
2004
The electrochemistry of α, β and μ cobalt-containing cordierites (Co2Al4Si5O18) attached to paraffin-impregnated graphite electrodes has been studied by linear scan and cyclic voltammetries in HCl+NaCl and NaOH electrolytes. This electrochemistry is compared with that of vitreous cobalt cordierite, cobalt(II) oxide and cobalt spinel aluminate (CoAl2O4), the two last taken as reference materials. Electrochemical processes involve the site-characteristic reduction of Co(II) species to cobalt metal near to −0.5 V vs. SCE and their oxidative dissolution near +0.3 V, accompanied by solid state interconversion between Co(II) and Co(III) at potentials above +0.45 V. Cordierite-modified electrodes …
The different catalytic behaviour in the propane total oxidation of cobalt and manganese oxides prepared by a wet combustion procedure
2013
Abstract Cobalt oxide and manganese oxide catalysts have been prepared through aqueous synthesis using a wet combustion procedure. These materials have been tested as catalysts for the total oxidation of propane. It has been observed a different catalytic behaviour between cobalt and manganese oxides although for both oxides a very high catalytic activity has been obtained. Cobalt oxides prepared by the wet combustion procedure are less reactive than a simple cobalt oxide prepared without the addition of organic acids. However, in the case of manganese oxide the use of organic acids highly increases the catalytic activity. The different catalytic behaviour has been related to the variation …
Inhibitoren der Korrosion 25(1) - Über die Rolle der Kationen in Neutralsalzen bei der Korrosion von Eisenwerkstoffen in Gegenwart von Sauerstoff
1979
Die Geschwindigkeit des Sauerstoffverbrauchs bei der Korrosion von jeweils 500 mg DAB6-Eisenpulver wird in Abhangigkeit von der Art des Kations in Neutralsalzen (Chloriden) unter Standardbedingungen bestimmt. In Gegenwart von Alkali-, Quartaren Ammonium, Quartaren Phosphonium-und Erdalkalichloriden ist die Geschwindigkeit des Sauerstoffverbrauches vergleichbar gros. Mit Zink-, Cadmium-, Nickel-und Kobaltchloriden wird aber im Bereich von pH5 bis pH7 eine uberraschend grose Verzogerung der Sauerstoffaufnahme beobachtet. Es handelt sich mit hoher Wahrscheinlichkeit um eine Blockade der kathodischen Bezirke in der Eisengrenzflache durch Abscheidung der schwerloslichen basischen Hydroxyde von Z…
Determination of Cd, Co, Cu, Fe, Pb, Mn, Ni and Zn in diets: Development of a method
1991
A method useful for the determination of cadmium, cobalt, copper, iron, lead, manganese, nickel and zinc in diets is described. Organic matter is destroyed applying a wet procedure, and element content is measured by flame atomic absorption spectroscopy (FAAS) in the case of copper, iron, manganese, nickel and zinc, and by graphite furnace (GF-AAS) in the case of cadmium, cobalt and lead. The matrix interference study is carried out. Values found for linearity, detection and quantitation limits as well as accuracy show that the described method is useful to determine the elements taken into account at usual levels in diets.
TAP reactor study of the deep oxidation of propane using cobalt oxide and gold-containing cobalt oxide catalysts
2009
Abstract A transient reactor study of the oxidation of propane to CO 2 on gold-free and gold-doped CoO x catalysts has been carried out. It has been demonstrated that the presence of gold markedly promotes the catalytic reactivity of cobalt oxide in the total oxidation of propane. Both catalysts oxidised propane directly to CO 2 via a Mars–Van Krevelen mechanism, and this was confirmed using isotopically labelled oxygen experiments. The increased activity of the gold catalyst is related to the faster reoxidation of the cobalt oxide when gold is present in the catalyst, since the reaction step in which the catalyst is reduced, due to propane oxidation, is similar for both catalysts. The fast…
Graphitically encapsulated cobalt nanocrystal assemblies
2010
Graphitically encapsulated cobalt nanocrystal assemblies are chemically prepared by one-pot reaction at380 degrees C followed by a reversed etching process to produce porous graphitic structure for revealing their self-assembling nature.
Trivalent cation substitution of pulverulent cobalt—iron molybdates Co1 − xFexMoO4
1998
Abstract Different mixed cobalt—iron molybdates Co1 − xFexMoO4 (0 ≤ x ≤ 1) have been prepared by means of a ceramic process. The oxidation of pulverulent samples leads to ferric molybdate Fe2(MoO4)3, spinelle Co3O4 and cobalt molybdate CoMoO4. After a strong grinding which reduces the grain size (about 0.1 μm) and induces crystallographic defects in the grains, the cobalt—iron molybdates can be partially oxidized into cation-deficient phases. This oxidation corresponds to an isostructural substitution of part of the Fe2+ and Co2+ ions by Fe3+ and Co3+ ions and the creation of cation vacancies. The concomitant presence of trivalent cations and associated cation vacancies in the lattice stabi…
Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles in metal–dielectric nanocomposites
2008
We report the preparation of a new type of nanocomposite containing cobalt and silver nanoparticles organized in parallel layers with a well controlled separation. This arrangement allows the observation of an enhanced low-frequency Raman signal at the vibration frequency of cobalt nanoparticles excited through the surface plasmons of silver nanoparticles. Numerical simulations of the electric field confirm the emergence of hot spots when the separation between silver and cobalt nanoparticles is small enough. © IOP Publishing Ltd.
Total oxidation of VOCs on Au nanoparticles anchored on Co doped mesoporous UVM-7 silica
2012
Abstract Gold deposited on a cobalt containing siliceous mesoporous structure, UVM-7, presents a good catalytic performance in the total oxidation of propane and toluene. The presence of both gold and cobalt is necessary as bimetallic Au/Co-UVM-7 catalysts are remarkably more active than monometallic Au/UVM-7 or Co-UVM-7 catalysts. The improved activity of the bimetallic AuCo-samples if compared to gold free cobalt catalysts can be explained on the basis of the enhanced reducibility of some cobalt species in the presence of gold, which facilitates the redox cycle. This high reducibility of cobalt species in the bimetallic samples is probably due to the formation of Co 3 O 4 domains at the g…
Hydrodesulfurization cobalt-based catalysts modified by gold
2007
Cobalt catalysts supported on amorphous SiO2 and ordered mesoporous silica (MCM-41) were prepared by incipient wetness impregnation. Gold was added by consecutive impregnation or by co-impregnation. The materials were characterised by XPS, XRD and TPR techniques and evaluated in the hydrodesulfurization (HDS) of thiophene in order to investigate the effect of the noble metal on the structure and on the catalytic behaviour of the supported cobalt. Co/MCM-41 exhibited higher HDS activity and higher stability than the Co/SiO2. Moreover, in contrast to silica case, the gold impregnated MCM-41, produced an enhancement of the cobalt catalytic activity, and this is likely to be related to an incre…