• Journal of the Korean Chemical Society
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• 제12권3호
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• pp.121-127
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• 1968

In the oligomerization of p-aminophenol under the catalytic action of the metallic complexes, the effects of the ligands are studied. When the initial velocity of $O_2$ uptake at pH 8 using Fe(Ⅲ) as the central metal and N-hydroxylethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,2-cyclohexanediaminetetraacetic acid(CyDTA) as the ligands respectively are compared, the velocities are as the following order: HEDTA > EDTA > DTPA > CyDTA. Further when the effect of the ligands, nitrilotriacetic acid (NTA), HEDTA, EDTA, and DTPA, on the yields of oligomers are compared, the result shows as the following order: NTA > HEDTA > EDTA > DTPA. These are nearly reverse order of the stability constants of the complexes. In order to determine the composition of the mixed complexes at the initial step, the method of continuous variation is used, and it is found that the composition ratio of Fe-EDTA complex to monomer in the mixed complexes is one at pH 5-8 range. It is also found that at pH 9 or in the more alkaline range, side reactions occur to form water soluble dimer of quinone type and the catalytic action of the metallic complex markedly decreases on account of the hydrolysis of the central metal by the $OH^-$ ion.

• Analytical Science and Technology
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• 제11권3호
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• pp.174-178
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• 1998

A chelating resin was prepared by the reaction of formaldehyde and resorcinol. It possesses high adsorption selectivity for transition metal ions such as Pb(II) and Ni(II). The adsorption and desorption yields of Pb(II), Ni(II), Co(II), Fe(II) and Zn(II) were determined using batch method. The significant characteristics of the chelating resin is the exchange processes between its hydrogen and metal ions. The mechanism of metal adsorption and desorption seems to be the competing protonation and complexation reaction of the functional group of the resin. This resin was applied to the rapid concentration of trace amounts of these metal ions and to the separation of Pb(II) from other metal ions in bulk solution.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.213-213
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• 2014

$300^{\circ}C$와 $500^{\circ}C$에서 아크 이온 증착된 도포층의 조성은 각각 Fe : Al : Ti : Si : N = 1.31 : 36.52 : 31.31 : 0.48 : 30.38 [wt.%]와 Fe : Cr : Al : Ti : Si : N = 1.24 : 0.56 : 36.82 : 32.72 : 0.59 : 28.07 [wt.%] 이었다. 0.1N $H_2SO_4$ 수용액과 인공해수 (ASTM D1141-98) 분위기에서 $300^{\circ}C$, $500^{\circ}C$에서 증착된 도포층의 부식전압과 부식속도는 각각 $-0.2787V_{SHE}$, $0.002A/cm^2$, $-2.764V_{SHE}$, $0.002A/cm^2$ 와 $-0.2799V_{SHE}$, $0.002A/cm^2$, $-0.0394V_{SHE}$, $0.002A/cm^2$이었다. 나노 경도값은 각각 23.6, 25.8 GPa 이었다. 이는 각각 2208.2, $2434.2H_V$에 해당되었다.

• Corrosion Science and Technology
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• 제14권5호
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• pp.232-238
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• 2015

Corrosion is of greatest concern for metallic materials exposed to corrosive seawater or aggressive marine atmospheres. Marine structures and components made of metallic materials incur an initial cost and additional large costs for corrosion control and maintenance. There have been worldwide efforts to minimize marine corrosion and extend service life of the materials. It is believed that various factors are associated with corrosion of marine grade metallic materials, particularly the temperature of the solution affecting the corrosion rate by changing dissolved oxygen solubility and concentrations of chloride. In the present study, the electrochemical characteristics of S355ML steel are investigated to identify corrosion acceleration tendencies with changes in solution temperature under marine environments. It was found that increasing seawater temperature, promoted not only activation of chloride ion transfer, but also the formation of porous $Fe(OH)_3$ or $Fe_2O_3$, leading to the acceleration of corrosion.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제7권1호
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• pp.67-74
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• 2008

In this paper, the surface characteristics of the AIP-TiN coated of the SKH51 and SKD11 steels under various deposition times are presented with emphasis on the comparison of the two materials. The micro-particle, the surface roughness, the micro-hardness, the coated layer thickness, the atomic distribution of Ti, N and Fe elements and the adhesion are measured for various deposition times. It has been shown that the micro-particle, the surface roughness, the coated layer thickness and the atomic distribution of Ti, N and Fe elements are similar for the two cases regardless of the test deposition time from 10 to 180 minutes. However, it has been shown that the micro-hardness and the adhesion of the SKH51 steel are higher than the SKD11 steel, indicating that they are much affected by the hardness of the material to be coated.

• Journal of the Korean Magnetic Resonance Society
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• 제17권2호
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• pp.105-110
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• 2013

HP1492 is a NifU-like protein of Helicobacter pylori (H. pylori) and plays a role as a scaffold which transfer Fe-S cluster to Fe-S proteins like Ferredoxin. To understand how to bind to iron ion or iron-sulfur cluster, HP1492 was expressed and purified in Escherichia coli (E. coli). From the NMR measurement, we could carry out the sequence specific backbone resonance assignment of HP1492. Approximately 91% of all resonances could be assigned unambiguously. By analyzing results of CSI and TALOS from NMR data, we could predict the secondary structure of HP1492, which consists of three ${\alpha}$-helices and three ${\beta}$-sheets. This study is an essential step towards the structural characterization of HP1492.

• Applied Chemistry for Engineering
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• 제30권3호
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• pp.324-330
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• 2019

Petal-like nickel cobaltite ($NiCo_2O_4$)/reduced graphene oxide (rGO) composites with different $rGO-to-NiCo_2O_4$ weight ratios were synthesized using a simple hydrothermal method and subsequent thermal treatment. In the $NiCo_2O_4/rGO$ composite, the $NiCo_2O_4$ 3-dimensional nanomaterials contributed to the improvement of electrochemical properties of the final composite material by preventing the restacking of the rGO sheet and securing ion movement passages. The composite structure was examined by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier-transform infrared (FT-IR) spectroscopy. The FE-SEM and TEM images showed that petal-like $NiCo_2O_4$ was supported on the rGO surface. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were used for the electrochemical analysis of composites. Among the prepared composites, $0.075g\;rGO/NiCo_2O_4$ composite showed the highest specific capacitance of $1,755Fg^{-1}$ at a current density of $2Ag^{-1}$. The cycle performance and rate capability of the composite material were higher than those of using the single $NiCo_2O_4$ material. These nano-structured composites could be regarded as valuable electrode materials for supercapacitors that require superior performance.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1892-1900
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• 2023

A protective oxide layer forms on the material surfaces of a Nuclear Power Plant during operation due to high temperature. These oxides can host radionuclides, the activated corrosion products of fission products, resulting in decommissioning workers' exposure. These deposited oxides are iron oxides such as Fe₃O₄, Fe₂O₃ and mixed ferrites such as nickel ferrites, chromium ferrites, and cobalt ferrites. Developing a new chemical decontamination technology for domestic CANDU-type reactors is challenging due to variations in oxide compositions from different structural materials in a Pressurized Water Reactor (PWR) system. The Korea Atomic Energy Research Institute (KAERI) has already developed a chemical decontamination process for PWRs called 'HyBRID' (Hydrazine-Based Reductive metal Ion Decontamination) that does not use organic acids or organic chelating agents at all. As the first step to developing a new chemical decontamination technology for the Pressurized Heavy Water Reactor (PHWR) system, we investigated magnetite dissolution behaviors in various HyBRID inorganic acidic solutions to assess their applicability to the PHWR reactor system, which forms a thicker oxide film.

• Journal of the Korean GEO-environmental Society
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• 제14권8호
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• pp.11-21
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• 2013

In-situ test to find the change of $Fe^{2+}$ and $Mn^{2+}$ concentrations and ion contents in groundwater was conducted during two pumping tests at the riverbank filtration site, where is the riverine area of the Nakdong River in Changnyeong-Gun. Groundwater was sampled at one pumping well and 10 monitoring wells during a 5 steps drawdown pumping test with the rates from $500m^3/day$ to $900m^3/day$ and a constant pumping test with $800m^3/day$. The change in ion concentration of groundwater was more remarkable during a step drawdown pumping test than a constant pumping test. Especially, the decrease in $Fe^{2+}$ and $Mn^{2+}$ concentrations was distinct in a step drawdown pumping test and it happens predominantly along the direction that the radius of pumping influence was small due to a good aquifer connectivity to a pumping position. The precipitation and the oxidation of iron and manganese were caused by an air inflow and a disturbance in groundwater flow due to an abrupt change in pumping rate. The pumping rate and spatial distribution of an aquifer around a pumping well need to be considered as an important factor for the development of in-situ iron and manganese treatment technology.

• Journal of the Korean Electrochemical Society
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• 제13권4호
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• pp.264-269
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• 2010

$LiNi_{0.5}Mn_{0.3}Co_{0.2}O_2$ active material was prepared by simple-combustion method and investigated as the cathode material for li-ion battery. The structural characterization was analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The XRD patterns of $LiNi_{0.5}Mn_{0.3}Co_{0.2}O_2$ sample was indicated a phase of layered hexagonal structure. The size of particles has not uniform diameters ranging from 100 to 300 nm. The electrochemical performance of the $LiNi_{0.5}Mn_{0.3}Co_{0.2}O_2$ was measured by Cyclic Voltammetry and galvanostatics. The $LiNi_{0.5}Mn_{0.3}Co_{0.2}O_2$ shows the discharge capacity of ~162 mAh/g in the range of 2.8 to 4.3 V at the first cycle.