Small Amounts Of Cobalt Research Articles

Co enrichment and Au–Cu–Co association in the Yundukala deposit in East Junggar, NW China: An in situ LA-ICP-MS study

The Yundukala deposit is a newly discovered Au–Cu–Co deposit located in the northern margin of Junggar in the Central Asian Orogenic Belt. The Au–Cu–Co mineralization is associated with the contact zone between a dioritic intrusion and basalt. The formation of the vein mineralization can be divided into three mineralization stages: chlorite + pyrite, quartz + polymetallic sulfide, and quartz + calcite. Ore microscopy and in-situ laser ablation inductively coupled plasma mass spectrometry were used to investigate textural and compositional relationship between pyrite, chalcopyrite, arsenopyrite, and cobaltite. The gold in the deposit is present in two main mineralogical forms: native gold (micron inclusions of the gold) and invisible gold (solid solution of gold). Cobalt in the vein mineralization is primarily associated with cobaltite, whereas pyrite, chalcopyrite, arsenopyrite, and pyrrhotite contain small amounts of cobalt. There is a positive correlation between As and Au in Py-Ⅱ (R2Au-As = 0.9211; R2Au-As = 0.4306) and cobaltite and a positive correlation between Co and Au in cobaltite (R2Au-Co = 0.8168). This relationship supports a model in which arsenic plays a role in the occurrence of gold. The correlation of trace elements in minerals and the formation sequence and interpenetration relationship between minerals indicate the progressive geochemical evolution of a single ore-forming fluid arising from a single vein mineralizing event. Hydrothermal processes led to alteration of the surrounding rocks while simultaneously extracting Au, Cu, and Co, forming ore-forming fluids. As physical conditions changed, minerals began to precipitate, ultimately resulting in the formation of ore deposits during the Carboniferous period (354–353 Ma).

Ni composite electrodes for hydrogen generation: Activation of Nb-based semiconductors

The hydrogen evolution reaction depends on the accumulation of electrons on the catalytic center to enable the two-electron processes involved in water reduction. This work reports on the modification of inexpensive nickel (Ni) composite electrodes with engineered semiconductor heterojunctions based on earth-abundant transition metals that show superior hydrogen generation activity in the presence of a non-toxic electrolyte (K2CO3). This is, small amounts of cobalt (Co) or copper (Cu) oxides can improve the reactivity of composite electrodes formed by deposition of titanium (Ti) or niobium (Nb) semiconductors onto Ni surfaces. In general, modified Nb-based semiconductors show better performance and their enhanced activity can be understood in terms of modified surface potentials upon formation of semiconductor-Ni heterojunctions. Photoelectrochemical activity can be detected in the presence of Cu oxides, where hydrogen generation onset potential is reduced under UV–Vis light irradiation. The study demonstrates that small composition changes can greatly affect the activity of Nb-based Ni composite electrodes, showing exciting new applications for Nb-based materials.

Interfacial compliance, energy dissipation, frequency effects, and long-term fretting corrosion performance of Ti-6Al-4V/CoCrMo interfaces.

Fretting corrosion in modular orthopedic implants is a well-documented process that may be associated with adverse local tissue reactions, pain, and revisions. Engineering modular junction interfaces to withstand applied fretting motion without surface abrasion could prevent implant degradation and surface damage. Previous work on geometrically modified Ti-6Al-4V/CoCrMo interfaces with increased compliance showed reduced fretting currents and surface damage during short term, variable-load in vitro testing. This study assesses the same interfaces under long-term conditions using an in vitro pin-on-disk fretting corrosion test apparatus. Preliminary variable-load frequency testing of typical control pin geometries showed a frequency-dependent current response, with underlying contact conditions of metal-metal interfaces that remained unchanged. One-million-cycle testing showed diminished fretting currents in all groups by 5× 105 cycles, but consistently lower currents in the high-compliance group. Corresponding fretting currents and work of fretting measurements of high-compliance pins confirmed that minimal fretting was experienced at the interface, with elastic bending of the pin accounting for almost all applied displacement. Debris generated during testing were composed of titanium and chromium oxides, small amounts of cobalt and molybdenum oxides, and sodium and phosphate originating from the surrounding test solution. Post-test analyses of sample surfaces revealed substantially more surface damage on CoCrMo disks than Ti-6Al-4V pins, thought to be a result of adhesive wear of mixed oxide debris on the pin and abrasion of the disk by the oxide debris layer. Surface damage to high-compliance pins suggests some abrasion is unavoidable with geometric modifications.

Preparation and characterization of ZnO/PEG-Co(II)-PbO2 nanocomposite electrode and an investigation of the electrocatalytic degradation of phenol

A ZnO/PEG (polyethylene glycol) -Co(II)-PbO2 nanocomposite electrode was constructed by using the anodic electrodeposition method and used for the electrocatalytic degradation phenol. The results showed that the electrode surface formed numerous PbO2 nanosphere structures, and the average size of a single nanosphere is approximately 0.4 μm. XRD and EDS results showed the active layer consisted of β-PbO2, and contained small amounts of cobalt and carbon. The electrochemical measurements showed that the electrode possessed a lower activation energy (Ea = 17.517 kJ∙mol−1) and charge transfer resistance (Rct = 7.564 Ω cm2) and a larger exchange current density (i°=1.476 × 10-4 mA cm-2). The phenol degradation process was controlled by the adsorption process and kinetic parameters were obtained with an initial concentration of 100 mg L−1. The electrode possessed a shorter half-life, larger reaction rate constant, and degradation efficiency (RE = 91.1 %) after 180 min. Reaction order was also calculated, and the degradation followed the pseudo-first-order reaction kinetics. HPLC results showed that the degradation pathway is as follows: firstly, phenol is gradually decomposed into o-diphenol, p-diphenol and benzoquinone under hydroxyl radicals attack. Then, benzoquinone is broken into maleic acid and fumaric acid. Finally, these acidic compounds are broken into oxalic acid, which is eventually mineralized.

Suppression of superconductivity and resistivity anomaly in Rh17S15 by cobalt substitution

The chalcogenide superconductor Rh17S15 is known for having an upper critical field of nearly twice the Pauli limit and an unusual temperature dependence of the resistivity. When doped with small amounts of cobalt, superconductivity in Rh17−xCoxS15 (0 < x < 3) is systematically suppressed. We explore the evolution of the electrical transport properties from 2–300 K as a function of x. We identify three temperature regimes which are differently affected by doping. The disappearance of an electron-like contribution to the transport at low temperature is correlated with the suppression of superconductivity.

Synergy of Cobalt and Silver Microparticles Electrodeposited on Glassy Carbon for the Electrocatalysis of the Oxygen Reduction Reaction: An Electrochemical Investigation.

The combination of two different metals, each of them acting on different steps of the oxygen reduction reaction (ORR), yields synergic catalytic effects. In this respect, the electrocatalytic effect of silver is enhanced by the addition of cobalt, which is able to break the O–O bond of molecular oxygen, thus accelerating the first step of the reduction mechanism. At the same time, research is to further reduce the catalyst’s cost, reducing the amount of Ag, which, even though being much less expensive than Pt, is still a noble metal. From this point of view, using a small amount of Ag together with an inexpensive material, such as graphite, represents a good compromise. The aim of this work was to verify if the synergic effects are still operating when very small amounts of cobalt (2–10 μg·cm−2) are added to the microparticles of silver electrodeposited on glassy carbon, described in a preceding paper from us. To better stress the different behaviour observed when cobalt and silver are contemporarily present in the deposit, the catalytic properties of cobalt alone were investigated. The analysis was completed by the Levich plots to evaluate the number of electrons involved and by Tafel plots to show the effects on the reaction mechanism.

Characterization of air-formed surface oxide film on a Co–Ni–Cr–Mo alloy (MP35N) and its change in Hanks’ solution

The air-formed surface oxide films used for stents were characterized to determine their composition and chemical state on a Co–Ni–Cr–Mo alloy. The change of the films in Hanks’ solution was used to estimate the reconstruction of the film in the human body. Angle-resolved X-ray photoelectron spectroscopy was used to characterize the composition of the film and substrate, as well as the film's thickness. The surface oxide film on the Co–Ni–Cr–Mo alloy (when mechanically polished) consists of oxide species of cobalt, nickel, chromium, and molybdenum, contains a large amount of OH−, and has a thickness of approximately 2.5nm. Cations exist in the oxide as Co2+, Ni2+, Cr3+, Mo4+, Mo5+, and Mo6+. Chromium is enriched and cobalt and nickel are depleted in the oxide; however, nickel is enriched and cobalt is depleted in the substrate alloy just under the surface oxide film. Concentration of chromium was low and that of nickel was high at small take-off angles. This indicates that distribution of chromium is greater in the inner layer, but nickel is distributed more in the outer layer of the surface oxide film. During immersion in Hanks’ solution, cobalt and nickel dissolved, and the film composition changed to mostly chromium oxide (Cr3+), along with small amounts of cobalt, nickel, and molybdenum oxides, and calcium phosphate containing magnesium, potassium, and carbonate. After immersion in Hanks’ solution, the thickness of the surface layer containing calcium phosphate increased to more than 4nm, while the amount of OH− increased. The amount of cobalt and nickel in the surface oxide film and in the substrate alloy just below the oxide decreased during immersion.

Characterization of whisker‐like crystals grown during the evaporation of Al‐Cu‐Co alloy

AbstractMorphological details and chemical composition of whisker‐like crystals (W‐LCs) were studied. The W‐LCs were grown on Al2O3 substrate as a result of evaporation of Al65Cu26Co9 alloy. Morphologically diverse W‐LCs formed groups in the shape of brushes. The two‐phase nature of W‐LCs was revealed. The W‐LCs consisted of an intermetallic on the Al matrix forming the core and of an external oxide shell of developed faces. The chemical composition of the core and the shell corresponded roughly to the stoichiometric formula Al3Cu and AlO accordingly. Additionally the core contained small amounts of cobalt and oxygen and the shell‐copper and cobalt. The growth mechanism of W‐LCs was proposed based on their morphological details and chemical compositions. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Use of water-insoluble surfactants for the removal of small amounts of transition metal nitrates from water

The removal of small amounts of cobalt and nickel nitrates from water with the use of water-insoluble surfactant, dioctadecyldimethylammonium bromide, was studied.

Separation of Cobalt and Zinc from Manganese, Magnesium, and Calcium using a Synergistic Solvent Extraction System Consisting of Versatic 10 and LIX 63

The Boleo leach solution contains large amounts of manganese (45 g/L), magnesium (25 g/L) and small amounts of cobalt (0.2 g/L) and zinc (1 g/L) in sea water. Due to the high manganese concentration, it is very difficult to separate cobalt and zinc from manganese, magnesium, and calcium using conventional solvent-extraction processes, which has led to the development of a synergistic solvent extraction (SSX) system consisting of Versatic 10 and LIX®63. By adding 0.4 M LIX 63 to 0.5 M Versatic 10, large synergistic shifts were obtained for cobalt (max. ΔpH50 4.24) and zinc (max. ΔpH50 1.62). After a single contact at pH 4.5, the extraction of cobalt was almost complete and that of zinc 80%. The extraction of manganese was 1.55%, and almost no magnesium and calcium were extracted, indicating excellent separation of cobalt and good separation of zinc from manganese, magnesium, and calcium. The SSX system was further optimized to reduce the co-extraction of manganese with the synthetic Boleo demonstration plant solution. It was found that with 0.33 M Versatic 10 and 0.30 M LIX 63, the SSX system composition approached optimum. After a single contact at pH 5.5, the extractions of cobalt and zinc were 93% and 70%, respectively, while the manganese concentration in the loaded organic solution was only 0.28 g/L. The extraction and stripping kinetics of cobalt and zinc were rapid. The SSX system was tested in two integrated pilot-plant trials with excellent results. Baja Mining has planned to implement the SSX circuit in their future Boleo plant.

Micro‐Raman and portable Raman spectroscopic investigation of blue pigments in selected Delft plates (17–20th Century)

AbstractThe blue pigment as well as other materials in a blue, white and ‘gold’ 17th century Delft dish were analysed and compared to the blue pigment(s) used in a modern blue‐and‐white Delft dish, obtained from a tourist shop in Amsterdam in 2004. The ancient Delft blue pigment was compared to a commercial Delft blue powder identified as a cobalt‐doped willemite, Zn2−xCoxSiO4. The 17th century Delft pigment showed a closer correspondence to the olivine, alpha‐cobalt silicate. The pigment in the modern blue Delft dish was mainly a vanadium‐doped zircon, ZrSiO4:V4+, with small amounts of cobalt, identified by EDX analysis. The cobalt compound could, however, not be characterised here for the modern dish. The pigment in the ‘golden’ rim was identified as pyrochlore yellow, PbSnSbO6.5. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Enhancement of ferroelectric and magnetic properties in BiFeO3 films by small amount of cobalt addition

Both the ferroelectric and magnetic properties of polycrystalline BiFeO3 films fabricated by chemical solution deposition were enhanced by adding small amounts of cobalt. Addition of 3at.% cobalt to BiFeO3 films increased the remanent polarization from 49to72μC∕cm2 and decreased the electric coercive field from 0.54to0.44MV∕cm. The ferroelectricity degraded when the cobalt concentration exceeded 9at.% due to the formation of the secondary phases of Bi2Pt. The saturation magnetization was drastically enhanced by the addition of cobalt up to 12at.%. This is because the magnetic moments are not canceled locally since the differences of magnetic moment between B-sites. The saturation magnetization decreased when the cobalt content exceeded 15at.%, thereby attributing to the formation of a nonmagnetic secondary phase of Bi2Pt. It is concluded that both ferroelectric and magnetic properties were enhanced, provided only small amount of cobalt were added to the films.

Extraction of pure metallic nickel from ores and plants at Ussangoda, Sri Lanka

Samples of serpentine from Ussangoda in the Hambantota District were found to contain 2-3% nickel of minable quality. Laterite from the same location contained 0.4% nickel. Nickel and several other metals in these rocks dissolved almost completely into hot 50% sulphuric acid. Nickel, cobalt, and any zinc that form complexes with ammonia were separated into the aqueous phase by addition of excess ammonia and filtration of precipitated hydroxides of magnesium, iron, manganese, chromium and aluminium. Acidification of the filtrate yielded a solution of nickel sulphate admixed with small amounts of cobalt and zinc. Electrolysis of the filtrate with a conducting tin oxide glass cathode after removal of cobalt yielded pure nickel. The process can also produce nickel ammonium sulphate. Extraction of metallic nickel from a nickel hyperaccumulating plant growing in Ussangoda is also demonstrated. The possibility of nickel mining in Sri Lanka and the importance of petrological, geochemical and ecological studies of the serpentine area at Ussangoda and other localities are discussed.

Cobalt distribution during copper matte smelting

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.

Studies of pasted nickel electrodes to improve cylindrical nickel–zinc cells

Abstract The aim of the present paper was to study the influence of foam type as well as nickel and cobalt additives on cell performance and cycle life of cylindrical nickel–zinc cells. Experiments have shown that discharge capacity depends on the foam type of nickel electrodes and is significantly improved by using thicker foam substrates (2.2 mm). AA-size nickel–zinc cells constructed of two thinner nickel electrode layers (1.6 mm) displayed stronger decline in capacity during cycle life due to a very low zinc/nickel hydroxide ratio (1.1–1.2). The addition of nickel and cobalt powder was investigated by means of resistivity measurements of PVA-bonded nickel hydroxide films. This study elucidated that small amounts of cobalt (2–8 wt.%) caused an extreme decline in resistivity. Admixture of nickel also lowered resistivity but not as great as cobalt. The cell performance turned out to be contrary to resistivity measurements; nickel–zinc cells prepared with a less conductive slurry delivered higher capacities. However, discharge capacity decreased rapidly after prolonged cell cycling, as the zinc/nickel hydroxide ratio of these cells was also considerably reduced.

Investigation of the cobalt distribution in the room temperature ferromagnet TiO2:Co

Recent reports of room temperature ferromagnetism in thin films of TiO2 doped with small amounts of cobalt have excited a great deal of interest due to the possible applications of this ferromagnetic, transparent semiconductor to spintronics devices. Ferromagnetism has been reported for TiO2 grown in both the anatase and rutile phases, although a range of magnetic moments has been reported by different groups. We have grown epitaxial thin films of Ti1−xCoxO2, with x=0.01–0.07 by pulsed laser deposition in both the anatase and rutile forms on single crystal substrates of LaAlO3, SrTiO3, and Al2O3. These films are ferromagnetic at room temperature with a magnetic moment of ∼1.7 μB/Co in the anatase phase and ∼0.6 μB/Co in the rutile phase. Detailed transmission electron microscopy measurements show a variation in the cobalt distribution in these materials that corresponds to the different magnetic moments. The cobalt does not appear to enter the anatase phase of TiO2, but rather forms crystallites of cobalt metal on the surface of anatase films. This results in a magnetic moment similar to that of bulk cobalt. In the rutile phase the cobalt has substituted uniformly throughout the lattice. We present the morphology and magnetization of TiO2:Co as a function of the TiO2 growth phase and substrate material. Preliminary electrical measurements are also mentioned.

Corrosion resistance of Nd‐Fe‐B permanent magnetic alloys. Part 1: Role of alloying elements

AbstractThe electrochemical behaviour of Nd‐Fe‐B magnetic alloys was investigated in acid and neutral solutions. The differences in the chemical composition of these materials have distinct influence on the corrosion rate and polarization behaviour. Small additions of cobalt, aluminium and gallium increase the corrosion resistance of the magnetic alloys at high cathodic potential. It was also observed that the increase of hydrogen evolution rate on the surface of the magnetic materials raises the rate of dissolution of these magnets. The electrostatic surface potential was examined by scanning probe microscopy. A relation between the electrostatic surface potential and electrochemical behaviour of these alloys was found. The high values of electrostatic surface potential of the intergranular phases reflect higher corrosion attack. Auger electron spectroscopy was used to analyse the surface layer which formed during anodic polarization of the magnet containing alloying additives. The result indicates the formation of (Nd,Fe)‐oxide with small amounts of cobalt and aluminium.

Composite ion exchangers based on KU-23 and KM-2p cation exchangers and nickel(III) hydroxide and their use for purification of nickel sulfate solutions to remove cobalt(II) impurity

A method of preparing composite ion exchangers based on macroporous cation exchangers and nickel(III) hydroxide was developed, and their suitability for deep purification of nickel(II) sulfate solutions to remove small amounts of cobalt(II) was demonstrated.

メカニカルアロイング処理による低Ｃｏ超硬合金の作製

Hard metals containing small amounts of cobalt were prepared by mechanical alloying using a vibrational ball mill in Ar atmosphere under reduced pressure. The contamination in the hard metal during mechanical alloying was attributed to wear of vibrational balls and could be reduced by using hard metal balls. Although mechanical alloying treatment was effective for the hard metals containing less than 3 mass%Co, increasing in cobalt content resulted in the formation of η phase (Co3W3C).A mechanical alloyed WC-lmass%Co hard metal, sintered at 1773K for 1.2ks in a vacuum, showed finer structure and higher hardness than a mixed WC-1mass%Co one.

Guidelines for the selection of hardfacing alloys for sliding wear resistant applications

The work presented in this report summarizes an evaluation of the relative sliding wear characteristics of several commonly used commercial hardfacing alloys. The alloys studied include cobalt-base, nickel-base and Fe-Cr-Ni alloys which also contain small amounts of cobalt. Selecting the most effective alloy combination to withstand sliding wear is a challenge for materials engineers, equipment designers and fabricators. Accurate guidelines for selecting compatible alloys from a wear resistance point of view are not available. On the basis of the results of this work several hardfacing alloy combinations were identified which provide good sliding wear resistance. In addition, several hardfacing alloy combinations were found to exhibit poor wear resistance compatibility. The guidelines presented in this report will aid in the selection of suitable hardfacing alloy combinations with adequate sliding wear resistance. The wear guidelines are also supplemented with corrosion data in several environments of importance in the chemical process industries. These data should assist in the selection and optimization of hardfacing alloys in the presence of aggressive environments.