• Clean Technology
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• v.15 no.1
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• pp.60-66
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• 2009

Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) that were widely used sulfur odorants in pipeline natural gas was studied using various ion-exchanged NaY zeolites at ambient temperature and atmospheric pressure. In order to improve the adsorption ability, ion exchange was performed on NaY zeolites with alkali metal cations of $Li^+,\;Na^+,\;K^+$ and transition metal cations of $Cu^{2+},\;Ni^{2+},\;Co^{2+},\;Ag^+$. Among the adsorbents tested, Cu-NaY and Ag-NaY showed good adsorption capacities for THT and TBM. These good behaviors of removal of sulfur compound for Cu-NaY and Ag-NaY zeolites probably was influenced by their acidity. The adsorption capacity for THT and TBM on the best adsorbent Cu-NaY-0.5, which was ion exchanged with 0.5 M copper nitrate solution, was 1.85 and 0.78 mmol-S/g at breakthrough, respectively. It was the best sulfur capacity so far in removing organic sulfur compounds from fuel gas by adsorption on zeolites. While the desorption activation energy of TBM on the Cu-NaY-0.5 was higher than NaY zeolite, the difference of THT desorption activation energy between two zeolites was comparatively small.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.624-627
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• 2001

Two kinds of Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$, the sintering samples and zone melting samples, were heat treated under pure Ar at 95$0^{\circ}C$. The substitution of Nd ion for Ba ion in the Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$ before and after the heat treatment were investigated by XRD. In order to know the effects of the heat treatment, the T$_{c}$ and J$_{c}$ of samples with the heat treatment and those without the heat treatment by Ar were comparatively studied. The results show that the substitution of Nd for Ba decreased, T$_{c}$, and J$_{c}$ increased after the treatment under Ar at 95$0^{\circ}C$. The Nd$_{1+x}$Ba$_{2-x}$Cu$_3$O$_{7-{\delta}}$ samples were oxygenated under pure oxygen at 30$0^{\circ}C$. From the XRD pattern it was found that the sample with x< 0.4 could transfer from tetragonal phase to orthorhombic phase after the oxygenation, but the sample with x>0.4 could not make the phase transition even after a long time oxygenation.ion even after a long time oxygenation.ation.n.ation.ation.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.356-361
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• 2013

Lead (II) ion selective poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore as a sulfur containing sensing material is successfully developed. The electrode exhibits good linear response of 25.6 mV / decade (at $20{\pm}0.2^{\circ}C$, r2=0.995) within the concentration range of $1.0{\times}10^{-1}{\sim}4.0{\times}10^{-7}$ M Pb (II). The composition of this electrode was Ionophore : PVC : dioctylphthalate : potassiumtetrakis(4-chlorophenyl)borate : Oleic acid = 5.0 : 20.0 : 25.0 : 4.0 : 5.0. When we consider the results of using different composition electrodes based on only one potassiumtetrakis(4-chlorophenyl)borate or Oleic acid liphophlic additive, poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore with potassiumtetrakis(4-chlorophenyl)borate and Oleic acid liphophlic additive had the best result in response characteristics. The electrode shows good selectivity for lead (II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. This electrode is suitable for use with aqueous solutions of pH 3.0 ~ 7.0 and their standard deviation in the measured emf differences was ${\pm}2.94$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-2}$ M and ${\pm}2.82$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-3}$ M. Their stabilization time was less than 710 s. and response time was less than 16 s.

• Journal of Powder Materials
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• v.30 no.6
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• pp.516-520
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• 2023

Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO₄ is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO₄O has two redox reactions (V⁵⁺/V⁴⁺/V³⁺) but low electrochemical activity. In this study, LiVPO₄O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO₄O_1-xF_x, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

• Journal of the Korean Chemical Society
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• v.30 no.5
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• pp.456-464
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• 1986

The complex formation of branched poly(ethylene imine) (BPEI) with bivalent transition metal ions, such as Fe(II), Co(II), Ni(II) and Cu(II), have been investigated in terms of visible absorption and pH titration methods in an aqueous solution in 0.1M KCl at 30${\circ}$. The stability constants for M(II)-BPEI complexes was calculated with the modified Bjerrum method. The formation curves of M(II)-BPEI complexes showed that Fe(II), Co(II), Ni(II) and Cu(II) ions formed coordination compounds with four, two, two, and two ethylene imine group, respectively. In the case of Cu(II)-BPEI complex at pH 3.4 ∼ 3.8, ${\lambda}_{max}$ was shifted to the red region with a decrease in the acidity. The overall stability constants (log $K_2$) increased as the following order, Co(II) < Cu(II) < Ni(II) < Fe(II).

• Journal of environmental and Sanitary engineering
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• v.14 no.1
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• pp.31-41
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• 1999

Several new ion exchange resins have been synthesized from chloromethyl styrene-1, 4-di-vinylbenzene with 1%, 2%, 5% and 10%-crosslinking and macrocyclic ligands of cryptand type by interpolymerization method. The adsorption characteristics and the pH, time, solvents and concentration dependence of the adsorption of metal ions by this resin were studied. The correlation between the separation characteristics of uranium and transition metal on the resins and the stability constants of complexes with macrocyclic ligands have been examined. The resins were very stable in both acidic and basic media and had good resistance to heat at $280^{\circ}C$. The $UO_2^{2+}$ aqueous solution was not adsorbed on the resins below pH 3.0, but the power of adsorption of $UO_2^{2+}$ increased rapidly above pH 4.0. The optimum equilibrium time for adsorption of metallic ions was twenty minutes and adsorptive power decreased in proportion to crosslinking size of the resins and order of dielectric constants of solvents used and the selective sequence for metal cations is in the order of $UO_2^{2+}$, $Cu^{2+}$ and $Ce^{3+}$ .

• Journal of the Korean Chemical Society
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• v.23 no.4
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• pp.198-205
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• 1979

A valence bond method of calculation of the dipole moments for octahedral $(M(III)0_3S_3)$ type complexes are developed, using $d^2sp^3 $hybrid orbitals of the central metal ions and the single basis set orbital of ligands. (M (III) =V (III), Cr (III), Mn (III), Fe (III), Co (III), Ru (III), Rh (III) and OS (III)). In this method the mixing coefficient of the valence basis sets for the central metal ion with the appropriate ligand orbitals is not required to be the same, differently from the molecular orbital method. The valence bond method is much more easier to calculate the dipole moments for octahedral complexes than the approximate molecular orbital method and the calculated results are also in the range of the experimental vaues.

• Journal of the Korean Magnetics Society
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• v.18 no.2
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• pp.75-78
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• 2008

$AB_2X_4$(A, B=Transition Metal, X=O, S, Se) are cubic spinel normal ferrimagnets, in which M ions occupy the tetrahedral sites and Cr ions occupy the octahedral sites. Recently, they have been investigated for behaviour of B site ions and A-B interaction. Polycrystalline $[Co_{0.9}Zn_{0.1}]_A[Cr_{1.98}{^{57}Fe_{0.02}}]_BO_4$ compound was prepared by wet-chemical process. The ferrimagnetic transition was observed around 90K. $M\"{o}ssbauer$ absorption spectra at 4.2K show that the well-developed two sextets are superposed with small difference in hyperfine fields($H_{hf}$). The hyperfine fields of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$ and $Co_{0.9}Zn_{0.1}Cr_{1.98}{^{57}Fe_{0.02}}O_4$ were determined to be 488, 478 kOe and 486, 468 kOe, respectively. We notice that the one of the magnetic hyperfine field values changes with Zn ion substitution. These results suggest the incommensurate states and spin-reorientation temperature($T_S=18K$) changes with Zn ions substitution below spin-reorientation temperature($T_S=28K$) of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$

• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.39-42
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• 2008

[ $AB_2X_4$ ](A, B=Transition Metal, X=O, S, Se) are cubic spinel normal ferrimagnets, in which M ions occupy the tetrahedral sites and Cr ions occupy the octahedral sites. Recently, they have been investigated for behaviour of B site ions and A-B interaction. Polycrystalline $[Co_{0.9}Zn_{0.1}]_A[Cr_{1.98}{^{57}Fe_{0.02}}]_BO_4$ compound was prepared by wet-chemical process. The ferrimagnetic transition was observed around 90K. $M\"{o}ssbauer$ absorption spectra at 4.2K show that the well-developed two sextets are superposed with small difference in hyperfine fields($H_{hf}$). The hyperfine fields of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$ and $Co_{0.9}Zn_{0.1}Cr_{1.98}{^{57}Fe_{0.02}}O_4$ were determined to be 488, 478 kOe and 486, 468 kOe, respectively. We notice that the one of the magnetic hyperfine field values changes with Zn ion substitution. These results suggest the incommensurate states and spin-reorientation temperature($T_S=18K$) changes with Zn ions substitution below spin-reorientation temperature($T_S=28K$) of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.421-429
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• 2018

Hydrazine based reductive dissolution applied on magnetite oxide was investigated. Dissolution of Fe(II) and Fe(III) from magnetite takes place either by protonation, surface complexation, or reduction. Solution containing hydrazine and sulfuric acid provides hydrogen to break bonds between Fe and oxygen by protonation and electrons for the reduction of insoluble Fe(III) to soluble Fe(II) in acidic solution of pH 3. In terms of dissolution rate, numerous transition metal ions were examined and Cu(II) ion was found to be the most effective to speed up the dissolution. During the cycle of Cu(I) ions to Cu(II) ions, the released electron promoted the reduction of Fe(III) and Cu(II) ions returned to Cu(I) ion due to the oxidation of hydrazine. In the experimental results, the addition of a very low amount of cupric ion (about 0.5 mM) to the solution increased the dissolution rate about 40% on average and up to 70% for certain specific conditions. It is confirmed that even though the coordination structure of copper ions with hydrazine is not clear, the $Cu(II)/H^+/N_2H_4$ system is acceptable regarding the dissolution performance as a decontamination reagent.