Cobalt Inclusions Research Articles

Magnetic carbon xerogels for the catalytic wet peroxide oxidation of sulfamethoxazole in environmentally relevant water matrices

Novel magnetic carbon xerogels consisting of interconnected carbon microspheres with iron and/or cobalt microparticles embedded in their structure were developed by a simple route. As inferred from the characterization data, materials with distinctive properties may be directly obtained upon inclusion of iron and/or cobalt precursors during the sol-gel polymerization of resorcinol and formaldehyde, followed by thermal annealing. The unique properties of these magnetic carbon xerogels were explored in the catalytic wet peroxide oxidation (CWPO) of an antimicrobial agent typically found throughout the urban water cycle – sulfamethoxazole (SMX).A clear synergistic effect arises from the inclusion of cobalt and iron in carbon xerogels (CX/CoFe), the resulting magnetic material revealing a better performance in the CWPO of SMX at the ppb level (500μgL−1) when compared to that of monometallic carbon xerogels containing only iron or cobalt. This effect was ascribed to the increased accessibility of highly active iron species promoted by the simultaneous incorporation of cobalt.The performance of the CWPO process in the presence of CX/CoFe was also evaluated in environmentally relevant water matrices, namely in drinking water and secondary treated wastewater, considered in addition to ultrapure water. It was found that the performance decreases when applied to more complex water and wastewater samples. Nevertheless, the ability of the CWPO technology for the elimination of SMX in secondary treated wastewater was unequivocally shown, with 96.8% of its initial content being removed after 6h of reaction in the presence of CX/CoFe, at atmospheric pressure, room temperature (T=25°C), pH=3, [H2O2]0=500mgL−1 and catalyst load=80mgL−1. A similar performance (97.8% SMX removal) is obtained in 30min when the reaction temperature is slightly increased up to 60°C in an ultrapure water matrix. Synthetic water containing humic acid, bicarbonate, sulphate or chloride, was also tested. The results suggest the scavenging effect of the different anions considered, as well as the negative impact of dissolved organic matter typically found in secondary treated wastewater, as simulated by the presence of humic acid.An in-situ magnetic separation procedure was applied for catalyst recovery and re-use during reusability cycles performed to mimic real-scale applications. CWPO runs performed with increased SMX concentration (10mgL−1), under a water treatment process intensification approach, allowed to evaluate the mineralization levels obtained, the antimicrobial activity of the treated water, and to propose a degradation mechanism for the CWPO of SMX.

Influence of coated SiC particulates on the mechanical and magnetic behaviour of Fe–Co alloy composites

Near-equiatomic Fe–Co alloy composites containing 0, 5 and 10 vol% of uncoated and coated SiC particles were prepared by applying a uniaxial pressure of 80 MPa at 900 °C for 5 min in a spark plasma sintering furnace. The SiC particles used in this study were coarse, with an average particle size of 20 μm and their surfaces were coated with four different types of coatings, namely Ni–P, Cu, Co and duplex Cu and Ni–P by an electroless plating method. Quasi D.C. magnetic, bending and hardness tests were performed on the composites. The influence of particulate coatings on the magnetic and mechanical behaviour of the composites was investigated by correlating their properties with their microstructures as observed using scanning electron microscopy and optical microscopy and crystallographic information as obtained using X-ray diffraction. The cobalt coated particles were found to exhibit the best wettability with the matrix without the formation of deleterious intermetallic compounds at the interface. Because of the better interfacial bonding in the composites with Co coated particles, there was an enhancement in flexural strength and permeability compared to the uncoated and other coated particulate composites studied. In addition, inclusion of cobalt coated SiC particulates produced an increase in hardness and a decrease in coercivity compared to the monolithic material.

ChemInform Abstract: Magneto‐optic Studies of Magnetic Oxides

AbstractReview: 21 refs.

Magneto-optic studies of magnetic oxides

A brief review of the use of magneto-optic methods to study magnetic oxides is given. A simple method to obtain the magnetic circular dichroism (MCD) of a thin film on a transparent substrate is described. The method takes full account of multiple reflections in the film and substrate. Examples of the magneto-optic spectra of Co-doped ZnO, Fe3O4, and GdMnO3 are given. The Maxwell–Garnett method is used to describe the effects of metallic cobalt inclusions in Co:ZnO samples, and the change of the MCD spectra of Fe3O4 at the Verwey temperature is discussed. Data showing different MCD signals at different energies is presented for GdMnO3.

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.

The effect of cobalt on the electrochemical performance of β-nickel hydroxide electrodes

Crystalline β-nickel hydroxide comprises of a periodic stacking of charge neutral nickel hydroxide layers. Translation or rotation of nickel hydroxide layers with respect to each other generates stacking faults while an intergrowth of one polymorphic modification in the other generates interstratification. These changes generate structural disorder within the sample and the phases are designated as β bc (bc-badly crystalline) nickel hydroxide. The structure, composition and morphology of these phases differ significantly compared to highly ordered crystalline β-nickel hydroxide. Crystalline β-nickel hydroxide exchanges 0.3e/Ni whereas stacking faulted β-nickel hydroxide and β bc-nickel hydroxide exchanges 0.8–0.9e/Ni. Inclusion of cobalt metal as a conducting additive during the electrode fabrication of pasted electrodes is expected to enhance the electrochemical performance of nickel hydroxide. In contrast to the literature reports, partial substitution of cobalt for graphite to highly ordered crystalline phase of β-nickel hydroxide does not show any improvement in their electrochemical activity. Stacking faulted β-nickel hydroxide, β bc-nickel hydroxide and chemically substituted nickel hydroxide samples also does not show any enhancement in their reversible discharge capacity on inclusion of cobalt. This clearly demonstrates that the electrochemical activity is mainly dictated by the structural disorders at 25–30 °C.

Influence of oxygen and nitrogen addition during growth of CVD diamond on pure cobalt substrates

It was shown that in MPCVD reactors the use of common H and CH 4 flows, can lead to the formation of free-standing diamond films directly on pure cobalt substrates. The characteristic low adhesion of these films can be explained by the formation of a graphitic layer between the substrate and the film. Scanning electron microscopy analysis shows special areas at the film grain boundaries that were subsequently identified as cobalt inclusions by EDS. In this work we have studied the influence of oxygen and nitrogen addition on the film's growth morphology. Once again SEM and EDS were used to access respectively the films growth morphology and cobalt content. Our results clearly indicate that the addition of oxygen during the initial stages of diamond nucleation prevents diffusion of cobalt into the film. Further, we believed that this effect is likely due to the formation of a cobalt-oxide layer between the film and the substrate. Also, the addition of nitrogen and oxygen the later during nucleation or during growth leads to an increase in the film's growth rate. A preferential (111) surface morphology with clear octahedron facets and films with dominant (100) crystallographic planes are detected. A model is presented for the growth of CVD diamond on cobalt substrates with the addition of oxygen and nitrogen.

Addition of nickel to Murashige and Skoog medium in plant tissue culture activates urease and may reduce metabolic stress

Nickel has been identified as an essential element for plant growth. The lack of nickel and the inclusion of cobalt leads to absence of urease activity in plants grown on MS medium in tissue culture. To avoid leaf damage and metabolic stress, nickel should be included in tissue culture growth media.

Electrochemical behaviour of lead alloys as anodes in zinc electrowinning

Abstract The electrochemical and corrosion properties of the ternary and quaternary lead alloys Pb–0·18Ag–0·012Co, Pb–0·2Ag–0·06Sn–0·03Co, and Pb–0·2Ag–0·12Sn–0·06Co (wt-%) have been investigated. The formation of oxide layers on the surface of these alloys was traced by cyclic voltammetric methods and the composition of the anodic oxide layers was determined by X-ray and SEM analyses. The cobalt inclusions reduce the anodic polarisation and improve the corrosion resistance of the alloy. The Pb–0·2Ag–0·12Sn–0·06Co alloy displays electrochemical and corrosion properties similar to those of Pb–1Ag and can be used as a substitute for the latter as a material for anodes in the electrowinning of zinc from sulphate electrolytes.

Micromechanical simulation of crack growth in WC/Co using embedded unit cells

Nowadays, hard metals are omnipresent as tool materials in industry. The material behavior is from decisive importance, from the safety point of view as well as from economical aspects. As a result of the manufacturing and coating process cracks are introduced into the surface of hard metal tools. A micromechanical model has been developed in order to simulate crack growth in a WC/Co hard metal. The elastic model consists of a unit cell with a cobalt island in a carbide environment, which is embedded in a composite surrounding. The energy release rate is calculated for a crack propagating along the symmetry plane of the model on a microscopic scale. The cobalt phase influences the crack driving force in an important way. The energy release rate of a crack approaching the cobalt phase increases, while it decreases rapidly for the crack propagating towards the center of the cobalt island. Parametric studies were carried out to determine the influence of different cobalt inclusion shapes and cobalt volume fractions on the energy release rate. Moreover, the energy release rate is calculated for a unit cell with two square cobalt inclusions and compared to crack propagation in a computational cell with a single inclusion.

Separation of Clethodim Herbicide from Acid and Photodegradation Products by Liquid Chromatography

Abstract Clethodim, (E,E)-(±)-2-[1-[[(3-chloro-2-propenyl)oxy]lmino] propyl]-5[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one, is stable in acetonitrlie, but the Inclusion of water induced degradation in the dark. Addition of acetic acid to the mobile phase did not increase degradation; however, it did improve peak symmetry and liquid chromatographic (LC) separation, with the optimum resolution at 0.75% acetic acid. The extinction coefficient for clethodim at 254 nm did not change in acetonitrlie with addition of water or acetic acid. The LC detector responded linearly to clethodim in the 0.7-400 ppm range. Separate solvent gradient programs (40 min each) were developed for separation of acid degradation products (ADPs) and the photodegradation products (PDPs). The inclusion of cobalt or silver nitrate to the mobile phase did not improve separations. A minimum of 31 and 19 products formed during photolytic and hydrolytic degradation of clethodim, respectively. PDPs were more polar than ADPs. Reproducibility of this method was considered to be acceptable for separation of ADPs and PDPs of clethodim.

Control of selenium and cobalt deficiency in lambs by supplementation of oral anthelmintics.

The benefits of the inclusion of cobalt and selenium supplements in anthelmintic preparations were demonstrated in a 10 week trial with cobalt- and selenium-deficient blackface wethers. The anthelmintics were based on oxfendazole and on levamisole plus oxyclozanide; three doses provided, in total, 38 mg cobalt and 7.2 or 11.3 mg selenium. Administration of the supplements prevented the weight loss and reduction in food intake observed in unsupplemented animals. Blood glutathione peroxidase activities were restored to normal and increases in serum vitamin B12 levels were observed which were consistent with the prevention of both cobalt and selenium deficiencies.

Characteristics of diamond regrowth in a synthetic diamond compact

A transmission electron microscopic study of a commercial sintered diamond compact is reported that identifies and characterizes the diamond that has regrown between the grains of the original diamond powder during the high-pressure, high-temperature manufacturing process of the compact. The majority of the original grains are strongly deformed whereas the regrown diamond shows little or no plastic deformation. The dislocations in diamond regrown between the original grains occur in low-angle boundaries and other configurations typical of grown-in dislocations in crystals. The manufacturing process involves infiltrating the diamond aggregate by molten cobalt, and the regrown diamond is characterized by the presence of cobalt inclusions in sizes ranging from a few tenths of a micrometre down to a few nanometres, possessing the same orientation and lattice parameter as the diamond host. Graphite inclusions also occur in regrown diamond, few in comparison with cobalt inclusions and in random orientation. The graphite crystals exhibit axial ratios, (c/a), lowered by several per cent due to the containment pressure exerted by the diamond host.

The influence of cobalt on the photo-luminescence of silver-activated ZnS : CdS Phosphors containing Nickel

The influence of cobalt inclusions in ZnS∶CdS∶Ag∶Ni phosphors on their excitation and emission spectra, temperature-dependence of fluorescence and thermoluminescence has been studied. Increase in cobalt concentration seems to have no effect on the excitation and emission spectra. The temperature-dependence of fluorescence af phosphors containing 0%–0.065% cobalt has been measured over the temperature range of 77 °K to 600 °K. The observed changes in the activation energy for the quenching process with increase in cobalt concentration are attributed to the presence of deep electron traps. Thermoluminescence curves show peaks identified as due to chlorine, cadmium, cobalt and nickel impurities. The corresponding energy depths are 0.26 eV, 0.52 eV, 0.53 eV and 0.78 eV. A thermoluminescence peak with an energy depth of 1.09 eV has also been found. An attempt has been made to identify the origin of this peak.