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The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide

100%
Lendzion-Bieluń Z., Jędrzejewski R., Arabczyk W.
Open Chemistry
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2011
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vol. 9
|
issue 5
834-839
EN
During precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction. [...]
2
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Determination of cobalt in water samples by atomic absorption spectrometry after pre-concentration with a simple ionic liquid-based dispersive liquid-liquid micro-extraction methodology

88%
Abdolmohammad-Zadeh H., Ebrahimzadeh E.
Open Chemistry
|
2010
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vol. 8
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issue 3
617-625
EN
A rapid dispersive liquid-liquid micro-extraction (DLLME) methodology based on the application of 1-hexylpyridinium hexafluorophosphate [C6py][PF6] ionic liquid (IL) as an extractant solvent was applied for the pre-concentration of trace levels of cobalt prior to determination by flame atomic absorption spectrometry (FAAS). 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was employed as a chelator forming a Co-PMBP complex to extract cobalt ions from aqueous solution into the fine droplets of [C6py][PF6]. Some effective factors that influence the micro-extraction efficiency include the pH, the PMBP concentration, the amount of ionic liquid, the ionic strength, the temperature and the centrifugation time which were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and the enrichment factor were 0.70 µg L−1 and 60, respectively. The relative standard deviation (RSD) for six replicate determinations of 50 µg L−1 Co was 2.36%. The calibration graph using the pre-concentration system was linear at levels 2–166 µg L−1 with a correlation coefficient of 0.9982. The applicability of the proposed method was evaluated by the determination of trace amounts of cobalt in several water samples. [...]
3
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Cobalt electrodeposition onto polycrystalline gold from ammoniacal solutions

88%
Mendoza-Huizar L., Rios-Reyes C.
Open Chemistry
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2013
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vol. 11
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issue 8
1381-1392
EN
In the present work, the cobalt electrodeposition onto polycrystalline gold electrodes from aqueous solutions containing 0.01M CoSO4 + 1 M (NH4)2SO4 at pH=7 was analyzed. Linear voltammetry results suggested a change in the kinetic of the cobalt electrodeposition. In all cases, the nucleation rate (A), the number of active nucleation sites (N 0) and the saturation number of nuclei (N s ) values were potential dependent. The calculated Gibbs free energy (ΔG) for this system was 1.88×10−20 J nuclei−1 and the transfer coefficient for the Hydrogen Electroreduction Reaction (HER) was 0.47. [...]
4
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Phase equilibria in the Er-Co-In system and crystal structure of Er8CoIn3 compound

88%
Dzevenko M., Hamyk A., Tyvanchuk Y., Kalychak Y.
Open Chemistry
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2013
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vol. 11
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issue 4
604-609
EN
Isothermal section of the Er-Co-In system at T = 870 K was constructed by means of X-ray powder diffraction, microstructure, and EDX-analyses. Twelve ternary compounds, namely ErCoIn5 (HoCoGa5-type), Er6Co17.92In14 (Lu6Co17.92In14-type), ErCo4In (MgCu4Sn-type), Er2CoIn8 (Ho2CoGa8-type), Er10Co9In20 (Ho10Ni9In20-type), Er3Co1.87In4 (Lu3Co1.87In4-type), ErCoIn, Er11Co4In9 (Nd11Pd4In9-type), Er11Co3In6, Er8CoIn3 (Pr8CoGa3-type), Er6Co2.19In0.81 (Ho6Co2Ga-type), and Er13.83Co2.88In3.10 (Lu14Co2In3-type) exist in the Er-Co-In system at this temperature. The crystal structure of the Er8CoIn3 compound was determined by means of X-ray powder method (Pr8CoGa3-type, P63mc space group, a = 1.02374(2) nm, c = 0.68759(2) nm). Almost none of the binary compounds dissolve the third component. The exception is the existence of the solid solution based on ErCo3 binary compound, which dissolves up to 8 at.% of In. [...]
5
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Antioxidant Enzyme Mechanism of Cluster Bean (Cyamopsis tetragonaloba (L.) Taub). Under Cobalt Stress

88%
Jayakumar K.
World News of Natural Sciences
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2019
|
vol. 24
64-70
EN
The research work has been carried out to estimate the low level cobalt application enhance antioxidant enzyme activities of cluster bean plants. The experiments were conducted in earthen pots containing 3 kg of air dried soil. The inner surface of pots was lined with polythene sheet. Cluster bean plants were raised in soil amended with different concentration of cobalt (0, 50, 100, 150, 200 and 250 mg/kg). The antioxidant enzyme activities were analysed at 30, 60, and 90 days after sowing (DAS). There found a significant enhance antioxidant enzyme activities at 50 mg/kg cobalt application in the soil in all the sampling days when compared to control. Further increase in the cobalt level (100-250 mg/kg) in the soil decreased antioxidant enzyme activities of cluster bean plants in all the sampling days.
6
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Evaluation of dispersive liquid-liquid microextraction for the determination of cobalt and cadmium by flame atomic absorption spectrometry: application in water and food samples

75%
Bosch Ojeda C., Sánchez Rojas F.
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issue 1
EN
Dispersive liquid-liquid microextraction (DLLME) was applied to the separation and preconcentration of Cd(II) and Co(II) from water and food samples. The influence of the following analytical parameters on the quantitative recoveries of cadmium and cobalt were investigated: pH, extraction solvent volume, dispersing solvent volume and type, and concentration of chelating agent. Under the optimized conditions, the detection limits were 2 μg L-1 and 13 μg L-1 for Cd(II) and Co(II), respectively. The proposed method was validated by the analysis of certified samples and has been applied to the determination of these ions in environmental water samples, with recoveries of 98 – 101% for Co(II) and 94 – 120% for Cd(II). In food samples the recoveries fell between 100 – 110% and 101-120% for Co(II) and Cd(II), respectively.
7
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Mechanical magnetometry of Cobalt nanospheres deposited by focused electron beam at the tip of ultra-soft cantilevers

63%
Lavenant H., Naletov V., Klein O., de Loubens G., Casado L., De Teresa J. M.
Nanofabrication
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2014
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vol. 1
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issue 1
EN
Using focused-electron-beam-induced deposition, Cobalt magnetic nanospheres with diameter ranging between 100 nm and 300 nm are grown at the tip of ultra-soft cantilevers. By monitoring the mechanical resonance frequency of the cantilever as a function of the applied magnetic field, the hysteresis curve of these individual nanospheres are measured. This enables the evaluation of their saturation magnetization, found to be around 430 emu/cm3 independent of the size of the particle, and to infer that the magnetic vortex state is the equilibrium configuration of these nanospheres at remanence. SEM image of a 200 nm Co nanosphere grown at the tip of an ultra-soft cantilever by focus electron beam induced deposition.
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