• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.150-157
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• 2006

The alternate plating method was suggested by a tin-cobalt alloy plating process which has excellent mechanical characteristics and also favorable to environment. Tin-cobalt alloy plating has many advantages such as nontoxicity, variable color-tone, and no post-treatment process. In this study, the plating conditions such as temperature, pH, current density, plating time, and amount of additive (glycine) were determined in the tin-cobalt alloy plating process through Hull-cell test and surface analysis. As the result of Hull-cell analysis, brightness became superior as the amount of glycine increased. It was found that the optimum alloy ratio was 0.03 M of $SnCl_{2}{\cdot}2H_{2}O$ and 0.05 M of $CoSO_{4}{\cdot}7H_{2}O$ at $50^{\circ}C$, pH 8.5, and $0.5A/dm^2$. The optimum amount of additive was 15 g/L of glycine and 0.1 g/L of organic acid. Then, the solution including glycine was recommended as an optimum plating solution for a chromium plating process.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.277-284
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• 2014

Using the spray pyrolysis process, nano-sized cobalt oxide powder with average particle size below 50 nm was prepared from cobalt chloride solution. The influences of the raw material solution on the properties of the powder formed examined. When the concentration of Co was low(20 g/L), the average particle size of the powder formed was roughly 20 nm, and the cohesion between these particles was significantly strong. When the concentration of Co increased to 100 g/L, the droplets nearly failed to exist in circular form and reflected a severely divided form. Furthermore, the average size of the particles formed was roughly 40 nm, and the particles reflected a polygonal form. When the solution was increased to nearly saturation level (Co at 200 g/L), the particle size distribution reflected significant unevenness due to severe droplet division while the surface also reflected significant unevenness. Furthermore, the average size of the particles formed increased significantly to 70 nm. The results of XRD analysis showed that the strength of the peaks reflected very little change when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration was increased to 100 g/L, the strength of the peaks increased compared to when the concentration was 50 g/L. However, when the concentration was increased to 200 g/L, the strength of the peaks failed to reflect significant change compared to when the concentration was 100 g/L. The specific surface area dramatically decreased by 30 % when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration of Co the solution increased to 100 g/L, the specific surface area decreased by roughly 15 %. Furthermore, when the concentration of Co was increased to nearly saturation level(200 g/L), the specific surface area decreased by roughly 35%.

• Journal of the Korean Magnetics Society
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• v.20 no.5
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• pp.182-186
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• 2010

Effect of cobalt substitution on the sintering behavior and magnetic properties of a NiZnCu ferrite was studied. $Ni_{0.36-x}Co_xZn_{0.44}Cu_{0.22}Fe_{1.98}O_4(0{\leq}x{\leq}0.04)$ ferrite was fabricated by a solid stat reaction method. It was proposed and experimentally verified that $Co^{2+}$ substituted NiZnCu ferrite was effective on improving the quality factor and magnetic properties of NiZnCu ferrites for multilayer chip inductors. The ferrite was sintered without sintering aids, at $880{\sim}920^{\circ}C$, for 2 h and the initial permeability, quality factor, density, shrinkage, saturation magnetization, and coercivity were also measured. The quality factor (Q) was increased linearly up to x = 0.01 and decreased rapidly over x = 0.01. As the cobalt content increased, the initial permeability and density of the ferrites decreases. The initial permeability of toroidal sample for $Ni_{0.35}Co_{0.01}Zn_{0.44}Cu_{0.22}Fe_{1.98}O_4$ ferrites sintered at $900^{\circ}C$ was 130 at 1 MHz and quality factor was 230.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1129-1135
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• 1999

The reduction of $SO_2$ by CO over supported cobalt catalysts was investigated within the temperature range of $350{\sim}550^{\circ}C$, initial $SO_2$ concentration of 1000~10000 ppm, $CO/SO_2$ molar ratio of 1.0~3.0 and space velocity of $5000{\sim}15000h^{-1}$. Several types of supports such as ${\gamma}-Al_2O_3$, $TiO_2$ were tested. The $SO_2$ conversion and selectivity to elemental sulfur were investigated using a differential fixed bed reactor at atmospheric pressure. The catalyst prepared by wet impregration of 5 wt % cobalt on ${\gamma}-Al_2O_3$ showed $SO_2$ conversion higher than 90% and COS yield lower than 6% at temperature above $400^{\circ}C$. The optimum $CO/SO_2$ molar ratio was investigated as 2.0. At higher $CO/SO_2$ molar ratio, the $SO_2$ conversion became higher but the main product was COS. The effect of $SO_2$ concentration and space velocity over $SO_2$ conversion and COS yield was not appreciable in the experimental range. The activated cobalt phase was detected as $CoS_2$ and the $CoS_2$ phase unchanged even after reaction.

• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.861-867
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• 2017

In order to improve the capacity and cycling stability of Ni-rich NCA cathode materials for lithium ion batteries, the boron and cobalt were doped in commercial $Li_{1.06}Ni_{0.91}Co_{0.08}Al_{0.01}O_2$ (NCA) powders. Commercial NCA particles are mixed composites such as secondary particles of about $5{\mu}m$ and $12{\mu}m$, and the particle size was decreased by doping boron and cobalt. The initial discharge capacities of the boron and cobalt doped NCA-B and NCA-Co were found to be 214 mAh/g and 200 mAh/g, respectively, which are higher values than that of the raw NCA cathode material. In particular, NCA-Co exhibits the best discharge capacity of 157 mAh/g after 20 cycles, which is probably due to the enhanced diffusion of lithium ion by crystal growth along with the c-axis direction.

• Journal of the Korean Chemical Society
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• v.32 no.2
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• pp.122-129
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• 1988

The rates of aquation of sparteine cobalt(II) halide and sparteine copper(II) halide were investigated in the citrate buffer solutions. The aquation of cobalt(II) complexes proceeds via D-mechanism and the catalytic effect of halide ions is not observed. The aquation of copper(II) complexes proceeds via $I_d$-mechanism and is catalyzed by the presence of cyanide and halide ions, and the aquation rate is pH dependent. The different mechanistic behavior of cobalt(II) complexes from corresponding copper(II) complexes seems to be attributed to the weakness of Co-N bond in the coordination sphere.

• Resources Recycling
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• v.29 no.4
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• pp.51-57
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• 2020

Separation of Co and Ni over Mg from the sulfuric acid solutions using Cyanex272, PC88A and Versatic acid 10 as an extractant was carried out. From the comparative studies about the extraction behavior of Co, Ni and Mg, Versatic acid 10 was superior to Cyanex272 and PC88A for the selective extraction of cobalt and nickel from the mixed solutions. About 98% of Ni and Co were extracted at equilibrium pH 7.0 and less than 5% of Mg was co-extracted by Versatic acid 10. McCabe-Thiele diagram indicated two stages requirement for Co and Ni extraction by 10% Versatic acid 10 at pH 7.0 and phase ratio (A/O) of 2.0. The loaded Co and Ni in organic phase was stripped effectively the sulfuric acid concentration above 70 g/L. 99.78% of cobalt and 98.42% of nickel were stripped.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.267-271
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• 2004

Lithium cobalt oxide $(LiCoO_2)$ cathode powders for rechargeable battery have been successfully prepared using urea hydrolysis method. The obtained hydrolysis-derived precursors with different Li/Co molar ratio were calcined at various temperatures. Low temperature phase $(LT-LiCoO_2)$ and high temperature phase $(HT-LiCoO_2)$ were obtained after calcination at $500^{\circ}C$ for 2 hr, and phase transformation from $LT-LiCoO_2{\;}to{\;}HT-LiCoO_2$ was completely occurred over $700^{\circ}C$. The layered structure of $LiCoO_2$ was well developed with a rise in the calcination temperature. Charge-discharge test show that the lithium cobalt oxide with 1.2 molar ratio prepared at $800^{\circ}C$ has an initial discharge capacity as high as 152 mAh/g, and the relatively stable cycling characteristic with 9.2 % of capacity fading was obtained after 40th charge-discharge test.

• Analytical Science and Technology
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• v.12 no.5
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• pp.421-427
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• 1999

Two shapes of crystals have been isolated by the interdiffusion of $Co(NCS)_2$ dissolved in methanol with 1,2-bis(2,2'-bipyridyl-6-yl)ethane (bbpe) dissolved in chloroform. The two crystals have been elucidated as $trans-Co^{II}(NCS)_2(bbpe)$ and $trans-Co^{II}(NCS)_2(bbpe){\cdot}2CHCl_3$, by X-ray crystallography, elemental analysis, IR, and thermal analysis. The two molecular structures are very similar except for the absence or presence of chloroform solvate molecules. The bbpe ligand coordinates to the cobalt(II) ion in an open-ended tetradentate mode, resulting in discrete mononuclear cobalt(II) complex. The cobalt atom adopts a typical octahedral arrangement with six nitrogen donating atoms with two NCS groups in trans positions. A significant solid-to-solid phase transition occurs presumably due to the change of conformationally flexible bbpe ligand. The formation of both crystals oeeurs in a successive two-step process, the formation of $trans-Co^{II}(NCS)_2(bbpe)$ and its transformation into $trans-Co^{II}(NCS)_2(bbpe){\cdot}2CHCl_3$. The thermal stability and favorable formation of the solvate crystals may be ascribed to the interaction between S atom of NCS group and Cl of chloroform.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1929-1933
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• 2012

Two cobalt(II) compounds $[Co(2,2{^\prime}-bipy)(H_2O)_2(SO_4)]_n$ (1) and $[Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6]{\cdot}2H_2O$ (2) (2,2'-bipy = 2,2'-bipyridine, $H_4btec$ = 1,2,4,5-benzenetetracarboxylic acid), have been simultaneously synthesized by a one-pot slow solvent evaporation reaction. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction (XRPD), IR, elemental and thermogravimetric analysis (TGA). The structural analysis reveals that compound 1 exhibits an infinite 1D chain structure with the octahedral Co(II) centers bridging by the tetrahedral ${\mu}_2-SO{_4}^{2-}$ ligands, while compound 2 possesses a dinuclear $Co_2(2,2^{\prime}-bipy)_2(btec)(H_2O)_6$ unit and the two adjacent octahedral Co(II) ions are linked by the bismonodentately coordinated btec ligand. Additionally, compound 2 exhibits blue fluorescent emission in the solid state at room temperature.