• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.115-119
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• 2008

Single particle of nickel hydroxide and the surface-treated one with cobalt element were performed to review the effect of LiOH additive in alkaline electrolyte for Ni-MH batteries using microelectrode test system. As a result of cyclic voltammetry, the electrochemical behaviors such as the oxidation/reduction and oxygen evolution reaction are clearly observed for a single particle of nickel hydroxide, respectively. Furthermore, the reduction current peak of nickel hydroxide added with LiOH in electrolyte was very low and broad compared with the normal nickel hydroxide without an additive LiOH, which had a bad effect to the crystallization structure of nickel hydroxide. However, it was found that capacity and cycle properties of the nickel hydroxide treated with cobalt greatly increased by the addition of LiOH.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.710-718
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• 2021

Recently, due to high theoretical capacitance and excellent ion diffusion rate caused by the 2D layered crystal structure, transition metal hydroxides (TMHs) have generated considerable attention as active materials in supercapacitors (or electrochemical capacitors). However, TMHs should be designed using morphological or structural modification if they are to be used as active materials in supercapacitors, because they have insulation properties that induce low charge transfer rate. This study aims to modify the morphological structure for high cycling stability and fast charge storage kinetics of TMHs through the use of nickel cobalt hydroxide [NiCo(OH)₂] decorated on nickel foam. Among the samples used, needle-like NiCo(OH)₂ decorated on nickel foam offers a high specific capacitance (1110.9 F/g at current density of 0.5 A/g) with good rate capability (1110.9 - 746.7 F/g at current densities of 0.5 - 10.0 A/g). Moreover, at a high current density (10.0 A/g), a remarkable capacitance (713.8 F/g) and capacitance retention of 95.6% after 5000 cycles are noted. These results are attributed to high charge storage sites of needle-like NiCo(OH)₂ and uniformly grown NiCo(OH)₂ on nickel foam surface.

• Journal of Powder Materials
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• v.28 no.6
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• pp.497-501
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• 2021

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

• Resources Recycling
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• v.22 no.6
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• pp.48-54
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• 2013

The methods to separate and remove copper in the mixed solution ((399 ppm Cu, 208 ppm Fe, 15.3 g/L Ni, 2.1 g/L Co) with nickel, cobalt and iron were investigated. With hydroxide precipitation method, copper and iron ions were completely precipitated and removed from the solution at pH 7 while some nickel and cobalt also were precipitated. 99.75% copper could be precipitated and removed as copper sulfide from the solution with adding $Na_2S$ (1.25 w/v concentration) of 2 times equivalent of Cu at pH 1. Copper was selectively absorbed on TP 207 ion exchange resin at equilibrium pH 2.0 and could be eluted from copper-loaded resin using 5% $H_2SO_4$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.3
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• pp.143-148
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• 2021

Alkaline oxygen evolution reaction (OER) electrocatalysts have been widely studied for improving the efficiency and green hydrogen production through electrochemical water splitting. Transition metal-based electrocatalysts have emerged as promising materials that can significantly reduce the hydrogen production costs. Among the available electrocatalysts, transition metal-based layered double hydroxides (LDHs) have demonstrated outstanding OER performance owing to the abundant active sites and favorable adsorption-desorption energies for OER intermediates. Currently, cobalt doped nickel LDHs (NiCo LDHs) are regarded as the benchmark electrocatalyst for alkaline OER, primarily owing to the physicochemical synergetic effects between Ni and Co. We report effects of heat-treatment of the as-grown NiCo LDH on electrocatalytic activities in a temperature range from 250 to 400℃. Electrocatalytic OER properties were analysed by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The heat-treatment temperature was found to play a crucial role in catalytic activity. The optimum heat-treatment temperature was discussed with respect to their OER performance.

• Journal of Powder Materials
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• v.21 no.2
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• pp.131-136
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• 2014

Cathode materials and their precursors are prepared with transition metal solutions recycled from the the waste lithium-ion batteries containing NCM (nickel-cobalt-manganese) cathodes by a $H_2$ and C-reduction process. The recycled transition metal sulfate solutions are used in a co-precipitation process in a CSTR reactor to obtain the transition metal hydroxide. The NCM cathode materials (Ni:Mn:Co=5:3:2) are prepared from the transition metal hydroxide by calcining with lithium carbonate. X-ray diffraction and scanning electron microscopy analyses show that the cathode material has a layered structure and particle size of about 10 ${\mu}m$. The cathode materials also exhibited a capacity of about 160 mAh/g with a retention rate of 93~96% after 100 cycles.

• The Korea Journal of Herbology
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• v.33 no.6
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• pp.87-92
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• 2018

Objectives: The aim of the study was to analyze the constituents of Pyrolusitum, which was used to eliminate static blood and inflammation, to establish the basis of clinical application. Methods: Qualitative analysis was performed by X-Ray Diffraction (XRD) using the sample as a powder, and the elemental content of granular sample was measured by X-Ray Fluorescence (XRF). 1 M hydrochloric acid and 5% sodium hydroxide aqueous solution were added to observe the changing shape, respectively. Results: Qualitative analysis by XRD revealed that the Pyrolusitum samples used in the study contained quarts and kaolinite. Quantitative analysis by XRF revealed that the manganese content in the samples used in the study was 6.16% on average, while iron was contained the highest amount of 22.99%. The minor constituents include 1.08% of titanium, 0.30% of barium, 0.18% of lead, 0.06% of zirconium, 0.05% of chromium, 0.04% of zinc, 0.03% of cadnium, 0.02% of nickel, 0.01% of arsenic, 0.01% of copper, 0.01% of rubidium, 0.01% of strontium, 0.00% of molybdenum, respectively. And cobalt, which is reported to be a constituent of Pyrolusitum, was not detected at all in the samples of the study. Pyrolusitum was dissolved in dark brown when it was put into 1 M hydrochlorid acid, and there was brown precipitate when sodium hydroxide solution was added to Pyrolusitum and stirred. Conclusions: It was found that manganese and iron were the major constituents of Pyrolusitum, and it could be identified by using concentrated hydrochloric acid and sodium hydroxide solution.

• Journal of the Korean institute of surface engineering
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• v.56 no.5
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• pp.299-308
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• 2023

In this study, phosphorus (P)-doped nickel cobaltite (P-NiCo₂O₄) and nickel-cobalt layered double hydroxide (P-NiCo-LDH) were synthesized on nickel (Ni) foam as a conductive support using hydrothermal synthesis. The thermal properties, crystal structure, microscopic surface morphology, chemical distribution, electronic state of the constituent elements on the sample surface, and electrical properties of the synthesized P-NiCo₂O₄ and P-NiCo-LDH samples were analyzed using thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The P-NiCo₂O₄ electrode exhibited a specific capacitance of 1,129 Fg^-1 at a current density of 1 Ag^-1, while the P-NiCo-LDH electrode displayed a specific capacitance of 1,012 Fg^-1 at a current density of 1 Ag-1. When assessing capacity changes for 3,000 cycles, the P-NiCo₂O₄ electrode exhibited a capacity retention rate of 54%, whereas the P-NiCo-LDH electrode showed a capacity retention rate of 57%.

• Journal of the Korean Chemical Society
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• v.17 no.1
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• pp.15-19
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• 1973

A method was developed for the separation of titanium, niobium and zirconium together in a group from the coexisting ions of various metals such as iron, cobalt, nickel, yttrium and rare earths by means of the cation exchange column using ${\alpha}$-hydroxyisobutyric acid as the eluent. In the course of the present investigation, it was found that the tailing phenomena of zirconium were attributable to the hydroxide precipitation which was made prior to the elution. For example, if zirconium was precipitated by sodium hydroxide, the tailing of zirconium became very serious in contrast to the results reported by others. This paper describes how these tailing phenomena of zirconium were prevented and how a practical procedure for the separation of these ions was, achieved using ion-exchange method. Using the present method the nuclides of $^{90m}Y$ and $^{90}Y$ were separated with radiochemical purity from the irradiated zirconium.