• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.74-77
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• 1994

Rare earth elements (REE) were individual separated by applying the gradient elution via HPLC using ${\alpha}-hydroxyisobutyric$ acid (HIBA) as an eluent. However, the overlap of Y and Dy peaks was too severe to obtain the resolution of these two peaks. The target transformation factor analysis (TTFA) was applied to resolve the elution peaks of Y and Dy. [A]$_{raw}$ formed from the absorbances of mixed solution was factor analyzed. The abstract factor analysis(AFA) was used to determine the number of components that contributed to the poorly resolved peaks. The error theory in the AFA showed that the number of components was 2. The test vectors which correspond to pure component were selected from the standard solutions of Y and Dy. TTFA was accomplished by target testing. The results showed that the resolution of two peaks as well as the determination of Y and Dy were possible by the factor analysis.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.946-954
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• 1995

The physico-chemical nature of the rare earth oxide which was produced by the caustic fritting of monazite was studied to furnish fundamental data that are required for its efficient use and processing. It was found that the material which was mainly constituted of light rare earths and thorium was a solid solution phase of oxide whose structure was fluorite-type face centered cubic. Its density was 6.75 g/$cm^3$ and it had a uniform particle size distribution at around 1 ${\mu}m.$ The crystallinity improved by heating to elevated temperatures, whereas the solubility in HCl decreased as the crystallinity improved. Complete dissolution in conc. HCl solution in short time (30 min.) was attained by heating to 70$^{\circ}C$. The measurement of zeta potential showed its I.E.P. to be at pH 8.6 of the suspension.

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.553-562
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• 2000

Daejeonsa basalt in the Mt. Juwang area is composed of 12 lava flows alternate with 9 peperites, and each lava and peperite has variable thickness. Globular peperites yielded in Daejeonsa basalt are mixed basalt clasts with reddish shale. Based on field description, when lava flows over unconsolidated wet shale or injectes into unconsolidated wet shale, peperites were formed at the contacts between lava and shale. Daejeonsa basalt are massive lava flows with rare vesicules: some vesicules are found in upper part of a flow unit. The basalt has mainly pseudomorphs of olivine as phenocryst, and also plagioclase and clinopyroxene phenocrysts in rocks with higher Mg-number. Matrix is mainly subophitic texture, sometimes showing ophitic and intergranular textures due to different cooling rate. Clinopyroxene is augite(Wo$_{41.6}$En$_{45.1}$Fs$_{13.3}$), and plagioclase is mostly labradorite(An$_{55.0}{\sim}_{67.7}$), but some is andesine(An$_{44.3}$) and bytownite(An$_{74.5}$). Oxide minerals are composed of titanomagnetite and ilmenite.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1656-1662
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• 2013

The ternary phase $EuZn_xIn_{4-x}$ has been identified as the main product of reactions of Eu, Zn, and In by using the In-flux method and characterized by both powder and single-crystal X-ray diffraction. The structure belongs to the common $BaAl_4$-type (tetragonal space group I4/mmm, Pearson code tI10) with lattice parameters of a = 4.5610(9) ${\AA}$, c = 12.049(3) ${\AA}$ for composition $EuZn_{1.10(12)}In_{2.90}$ and a = 4.5463(3) ${\AA}$, c = 12.028(2) ${\AA}$ for composition $EuZn_{1.18(2)}In_{2.82}$, respectively. In this structure, the Eu atoms are situated at the center of 18-vertex Fedorov polyhedra made of Zn and In atoms, where the 4d site is preferentially occupied by In and the 4e site is occupied by randomly mixed Zn and In atoms. Theoretical investigations using tight-binding linear muffintin orbital (TB-LMTO) method provide rationale for the observed site preferences and suggest potentially wider homogeneity range than the experimentally established for $EuZn_xIn_{4-x}$ ($x{\approx}1.1$).

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.70.1-70.1
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• 2012

In-situ X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies of SOFC cathode materials will be discussed in this presentation. The mixed conducting perovskites (ABO3) containing rare and alkaline earth metals on the A-site and a transition metal on the B-site are commonly used as cathodes for solid oxide fuel cells (SOFC). However, the details of the oxygen reduction reaction are still not clearly understood. The information about the type of adsorbed oxygen species and their concentration is important for a mechanistic understanding of the oxygen incorporation into these cathode materials. XPS has been widely used for the analysis of adsorbed species and surface structure. However, the conventional XPS experiments have the severe drawback to operate at room temperature and with the sample under ultrahigh vacuum (UHV) conditions, which is far from the relevant conditions of SOFC operation. The disadvantages of conventional XPS can be overcome to a large extent with a "high pressure" XPS setup installed at the BESSY II synchrotron. It allows sample depth profiling over 2 nm without sputtering by variation of the excitation energy, and most importantly measurements under a residual gas pressure in the mbar range. It is also well known that the catalytic activity for the oxygen reduction is very sensitive to their electrical conductivity and oxygen nonstoichiometry. Although the electrical conductivity of perovskite oxides has been intensively studied as a function of temperature or oxygen partial pressure (Po2), in-situ measurements of the conductivity of these materials in contact with the electrolyte as a SOFC configuration have little been reported. In order to measure the in-plane conductivity of an electrode film on the electrolyte, a substrate with high resistance is required for excluding the leakage current of the substrate. It is also hardly possible to measure the conductivity of cracked thin film by electrical methods. In this study, we report the electrical conductivity of perovskite $La_{0.6}Sr_{0.4}CoO_{3-{\delta}}$ (LSC) thin films on yttria-stabilized zirconia (YSZ) electrolyte quantitatively obtained by in-situ IR spectroscopy. This method enables a reliable measurement of the electronic conductivity of the electrodes as part of the SOFC configuration regardless of leakage current to the substrate and cracks in the film.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.3-9
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• 2002

The corrosion behavior of alloys in a molten salt was investigated along with the oxidation characteristics in the air. The basic composition of alloys in the study was Fe-25Ni-7Cr with Si and RE(rare-earth metal) as additives. The corrosion rate of the alloys was low in a molten salt of LiCl while the rate was high in the mixed molten salt of LiCl and $Li_2O$. When Si is added to the base alloy of Fe-25Ni-7Cr, corrosion resistance was improved as the Si content is increased up to 3%, however, it was observed that the corrosion resistance was getting worse as the Si content is increased. The base alloy with 2.43% of Si and 0.9% of RE(KSA-65), showed higher corrosion rate compared to that of KSA-63 alloy with an equivalent amount of only Si. The corrosion resistance of KSA-65 was similar to that of the base alloy(KSA-60). The oxidation resistance of KSA-65 alloy was greatly increased even at $850^{\circ}C$ for a long term exposure.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.147-147
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• 2013

Multiferroic material $BiFeO_3$ (BFO) is a typical multiferroic material with a room-temperature magnetoelectric coupling in view of high magnetic- and ferroelectric-ordering temperatures (Neel temperature $T_N$ ~ 647 K and Curie temperature TC ~1,103 K). Rare-earth ion substitution at the Bi sites is very interesting, which induces suppressed volatility of the Bi ion and improved ferroelectric properties. At the same time, the Fe-site substitution with magnetic ions is also attracting, since the enhanced ferromagnetism was reported. In this study, BFO, $Bi_{0.9}Dy_{0.1}FeO_3$ (BDFO), $BiFe_{0.97}Co_{0.03}O_3$ (BFCO) and $Bi_{0.9}Dy_{0.1}Fe_{0.97}Co_{0.03}O_3 $ (BDFCO) compounds were prepared by conventional solid-state reaction and wet-mixing method. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ for 24 h. The samples were immediately put into an oven, which was heated up to 800oC and sintered in air for 1 h. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies). Dy and Co co-doping at the Bi and the Fe sites induce the enhancement of both magnetic and ferroelectric properties of $BiFeO_3$.

• Clean Technology
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• v.26 no.3
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• pp.228-236
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• 2020

Korea has an economy based on manufacturing industrial fields, which produce high amounts of hazardous wastes, in spite of few landfill candidates, and a significant concern for fine airborne particulates; therefore, traditional waste management is difficult to apply in this country. Moreover, waste collection and accumulation have recently been intensified by the waste import prohibitions or regulations in developing nations, the universalization of delivery services in Korea, and the global COVID-19 crisis. This study thus presents a domestic waste management strategy that aims to address the recent issues on waste. The contents of the strategy as the main results of the study include the (1) improvement of the compatibility of the classification codes between the domestic hazardous waste and the international ones such as those of the Basel Convention; (2) consideration of the mixed hazard indices to represent toxicity from low-content components such as rare earth metals often contained in electrical and electronic equipment waste; (3) management application based on risks throughout the life cycles of waste; (4) establishment of detailed material flow information of waste by integrating the Albaro system, Pollutant Release and Transfer Register (PRTR) system, and online trade databases; (5) real-time monitoring and prediction of the waste movement or discharge using positional sensors and geographic information systems, among others; and (6) selection and implementation of optimal treatment or recycling practices through Life Cycle Assessment (LCA) and clean technologies.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.1006-1013
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• 1997

This study was carried out to elucidate the chemical characteristics of mutual separation for Am and Eu, which were selected as a stand-in from minor actinide and rare earth elements, by solvent extraction with di-(2-ethylhexyl)phosphoric acid containing zirconium at batch system. As results, 92.3% of Am and 99.1% of Eu were coextracted with 1M DEHPA/n-dodecane containing zirconium (Zr $concentration=8.7g/{\ell}$) at 0.5M $HNO_3$ in the extraction step. The extraction yields of Am and Eu were proportionally increased with the concentration of Zr in Zr salt of 1M DEHPA/n-dodecane having the synergistic effect. In the lst stripping step for the selective separation of Am, 38.1% of Am and 3% of Eu were stripped with the mixed solution of 0.05M DTPA and 1M lactic acid adjusted pH of 3.0. At that time, the separation factor calculated from the distribution coefficients of Am and Eu was 14.2. In the 2nd Stipping step to remove the Eu remained the organic phase after the lst stripping step, 94.4% 0f Eu was stripped into aqueous phase with 6M $HNO_3$.