• Journal of the Korean Magnetic Resonance Society
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• v.20 no.3
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• pp.76-81
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• 2016

Copper is an elemental ion in living organisms. CopP from Helicobacter Pylori (HpCopP) is a copper(I)-binding protein and was suggested as regulator of copper metabolism in vivo. Previously, the metal binding property of HpCopP for Ag(I), Cu(I), and Cu(II) as well as the tertiary structure of HpCopP was shown. In this study, the dynamic profiles of HpCopP depending on metal binding were studied using ${^1H}-^{15}N$ steady-state NOE analysis. The heteroNOE experiment was performed for apo-CopP or metal-bound CopP. The obtained NOE values were analyzed and compared to figure out the effect of metals on the structural flexibility of HpCopP. As a result, Ag(I) and Cu(I) ions improved the rigidity of the structure while Cu(II) ion increased the flexibility of the structure, suggesting the oxidation of the CXXC motif decreases the structural stability of HpCopP.

• Journal of Magnetics
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• v.17 no.2
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• pp.83-85
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• 2012

Magnetic particles in a novel, wound-healing ointment were studied using M$\ddot{o}$ssbauer spectroscopy and VSM to estimate the stability of the properties of the magnetic particles. The isomer shifts of $Fe_3O_4(A)$ were found to be 0.49-0.56 mm/s relative to iron metal, this indicates that the iron ions in $Fe_3O_4(A)$ are $Fe^{3+}$. On the other hand, the isomer shifts of $Fe_3O_4(B)$ were found to be 0.91-1.13 mm/s relative to iron metal, this shows that the ion state of $Fe_3O_4(B)$ is a mixed state of $Fe^{2+}$ and $Fe^{3+}$. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (${\sim}10\;{\AA}$), differs from the stoichiometric one. It was found that the area ratio of the M$\ddot{o}$ssbauer subspectra of $Fe_3O_4(A)$ / $Fe_3O_4(B)$ taken at 87 and 181 K linearly increased in comparison to the initial pure magnetic particles, but the rate of increase of the area ratio at 181 K was about two times that at 87 K. From the magnetic hyperfine field, despite their small size, the particles exhibit no superparamagnetism.

• Journal of Sensor Science and Technology
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• v.13 no.4
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• pp.282-286
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• 2004

${\alpha}-Fe_{2}O_{3}$ films were prepared by ultrasonic spray pyrolysis (USP) on $SiO_{2}$ coated Si wafers using iron acetylacetonate as an iron precursor. The crystallographic properties and surface morphologies of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray photoelectron spectroscopy (XPS) was carried out to determine the Fe oxidation states. In order to observe stability of the films to temperature, the resistance variation of the films with an ambient temperature was measured. The effects of substrate temperature on the structural and electrical properties of the ${\alpha}-Fe_{2}O_{3}$ films were studied. The films were densified from the substrate temperature of $350^{\circ}C$. The grain size of the films grown at $400^{\circ}C$ was shown to be increased abruptly comparing with that of $350^{\circ}C$. The films showed a low resistance variation between the ambient temperature of $300^{\circ}C$ and $350^{\circ}C$.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.727-732
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• 2016

A simple and rapid spectrophotometric method has been developed to enable the determination of plutonium concentration in an irradiated fuel solution in the presence of all fission products. An excess of ceric ammonium nitrate solution was employed to oxidize all the valence states of plutonium to +6 oxidation state. Interference due to the presence of fission products such as ruthenium and zirconium, and corrosion products such as iron in the envisaged concentration range, as in the irradiated fuel solution, was studied in the determination of plutonium concentration by the direct spectrophotometric method. The stability of plutonium in +6 oxidation state was monitored under experimental conditions as a function of time. Results obtained are reproducible, and this method is applicable to radioactive samples resulting before the solvent extraction process during the reprocessing of fast reactor spent fuel. An analysis of the concentration of plutonium shows a relative standard deviation of <1.2% in standard as well as in simulated conditions. This reflects the fast reactor fuel composition with respect to uranium, plutonium, fission products such as ruthenium and zirconium, and corrosion products such as iron.

• Journal of Industrial Technology
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• v.39 no.1
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• pp.7-14
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• 2019

Carbon nanotubes (CNT) on metal substrates are definitely beneficial because they can maintain robust mechanical stability and high conductivity between CNT and metal interfaces. Here, we report direct growth of CNT on Ni-based superalloy, Inconel 600, using thermal chemical vapor deposition (CVD) with acetylene feedstock in the growth temperature range of $400-725^{\circ}C$. Furthermore, we studied the effect of substrate pretreatment on the growth yield enhancement and growth temperature decrease of CNT on Inconel 600. Activation energy (AE) for CNT growth was estimated from the CNT height change with respect to the growth temperature. The AE values significantly decreased from 205.03 to 24.35 kJ/mol by the pretreatment of thermal oxidation of Inconel substrate at $725^{\circ}C$ under ambient. Higher oxidation temperature tends to have lower activation energy. The results have shown the importance of pretreatment temperature on CNT growth yield and growth temperature decrease.

• Journal of Electrochemical Science and Technology
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• v.7 no.4
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• pp.277-285
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• 2016

There is a growing demand for simple, cost-effective, and accurate analytical tools to determine the concentrations of biological and environmental compounds. In this study, a stable electroactive thin film of cobalt hexacyanoferrate (Cohcf) was prepared as an in situ chemical precipitant using electrostatic adsorption of $Co^{2+}$ on a silicate sol-gel matrix (SSG)-modified indium tin oxide electrode pre-adsorbed with $[Fe(CN)_6]^{3-}$ ions. The modified electrode was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. Electrocatalytic oxidation of hydrazine on the modified electrode was studied. An electrochemical sensor for hydrazine was constructed on the SSG-Cohcf-modified electrode. The oxidation peak currents showed a linear relationship with the hydrazine concentration. This study provides insight into the in situ growth and stability behavior of Cohcf nanostructures and has implications for the design and development of advanced electrode materials for fuel cells and sensor applications.

• Bulletin of the Korean Chemical Society
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• v.25 no.9
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• pp.1355-1360
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• 2004

The oxidative decomposition of trichloroethylene (TCE) was investigated using palladium catalysts supported on pure and sulfated zirconia. The reactions were performed under dry and wet conditions in the temperature between 200 and $550^{\circ}C$ keeping GHSV of 14,000 $h^{-1}.$ The products such as $C_2Cl_4,\;C_2HCl_5,\;CO\;and\;CO_2$ were observed in the reaction. The addition of water in the feed affected the distribution of reaction product with dramatically improved catalytic activity. The spectroscopic investigations gave an evidence that the strong acid sites play an important role on controlling the catalytic activity. Among the catalysts investigated, the Pd-loaded sulfated zirconia catalyst with 1 wt% Pd was found to exhibit the highest catalytic activity in the presence of water vapor having the stability for 30 h of the reaction at $500^{\circ}C$. The successful performance of the catalyst might be attributed to promotional effect of Pd active sites and strong acid sites induced from surface sulfate species on zirconia.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.43-52
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• 2021

The Ni-based superalloy, Inconel 740, was corroded between 800 and 1100℃ for up to 100 hr in air and Ar-0.2%SO₂ gas in order to study its corrosion behavior in air and sulfur/oxygen environment. It displayed relatively good corrosion resistance in both environment, because its corrosion was primarily dominated by not sulfidation but oxidation especially in Ar-0.2%SO₂ gas. Such was attributed to the thermodynamic stability of oxides of alloying elements when compared to corresponding sulfides. The scales consisted primarily of Cr₂O₃, together with some NiAl₂O₄, MnCr₂O₄, NiCrMnO₄, and rutile-TiO₂. Sulfur from SO₂ gas made scales prone to spallation, and thicker. It also widened the internal corrosion zone when compared to air. The corrosion resistance of IN740 was mainly indebted to the formation of protective Cr₂O₃-rich oxides, and suppression of the sulfide formation.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.5
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• pp.1-10
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• 2011

In this study, 13 water soluble polymers(6 natural polymer, 7 synthetic polymer) were treated on Hanji. Mechanical properties, morphology and oxidation index with thermal aging were measured on the aged Hanji, dewaxed Hanji and polymer treated Hanji. 3 natural polymer(such as CMC, EC, MC) and 3 synthetic polymers(such as PVA 1500, 2000, PEG 1500) treated Hanji had higher strength than other polymer treated Hanji. The oxidation index of 3% methyl cellulose solution treated Hanji did a little increase with thermal aging. Finally, methyl cellulose was found to be the most efficient method for strengthening the dewaxed Hanji. The best aging safety and thermal stability were obtained at the methyl cellulose 3% water solution.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2865-2870
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• 2013

Ni-Ag core-shell nanoparticles were synthesized by polyol process and microemulsion technique successfully. In the polyol process, a chemical reduction method for preparing highly dispersed pure nickel and Ag shell formation have been reported. The approach involved the control of reaction temperature and reaction time in presence of organic solvent (ethylene glycol) as a reducing agent for Ag cation with poly(vinyl-pyrrolidone) (PVP. Mw = 40000) as a capping agent. In microemulsion method, the emulsion was prepared by water/cetyltrimetylammonium bromide (CTAB)/cyclohexane. The size of microemulsion droplet was determined by the molar ratio of water to surfactant (${\omega}_o$). The core-shell formation along with the change in structural phase and stability against oxidation at high temperature heat treatments of nanoparticles were investigated by X-ray diffraction and TEM analysis. Under optimum conditions the polyol process gives the Ni-Ag core-shell structures with 13 nm Ni core covered with 3 nm Ag shell, while the microemulsion method gives Ni core diameter of 8 nm with Ag shell of thickness 6 nm. The synthesized Ni-Ag core-shell nanoparticles were stable against oxidation up to $300^{\circ}C$.