• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.219-222
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• 2001

Separation of lithium isotopes was investigated by chemical ion exchange with a hydrous manganese(IV) oxide ion exchanger using an elution chromatography. The capacity of manganese(IV) oxide ion exchanger was 0.5 meq/g. The heavier lithium isotope was enriched in the solution phase, while the lighter isotope was enriched in the ion exchanger phase. The separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assays. The separation factor of $^6Li^+$-$^7Li^+$ isotope pair fractionation was 1.018.

• Journal of Magnetics
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• v.19 no.3
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• pp.221-226
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• 2014

Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {$(dMR/dH)_{max}$} values were successfully achieved from $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMO-$xMn_2O_3$ (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at $1450^{\circ}C$, above the eutectic temperature of $1430^{\circ}C$, for 1 h in air. The highest LFMR value of 1.28% with the highest $(dMR/dH)_{max}$ value of 21.1% $kOe^{-1}$ was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and $(dMR/dH)_{max}$ values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

• 한국전기화학회:학술대회논문집
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• 2002.10a
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• pp.19-19
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• 2002

• 한국전기화학회:학술대회논문집
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• 1999.10a
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• pp.66-66
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• 1999

• 한국전기화학회:학술대회논문집
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• 1998.10a
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• pp.78-78
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• 1998

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.17-17
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• 2005

• Environmental Engineering Research
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• v.20 no.3
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• pp.230-236
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• 2015

26 multi-regional water treatment plants (WTPs) were investigated, to determine the characteristics of manganese (Mn) concentration and removal in Korea. Mn concentrations of raw water in most WTPs were higher than the drinking water standard (i.e., 0.05 mg/L); thus, proper removal of Mn at the WTPs is needed. Mn concentration was generally higher in lakes than rivers due to seasonal lake turnovers. The Mn concentrations of treated water at 26 WTPs in 2012 were less than 0.05 mg/L, due to strict law enforcement and water treatment processes optimization. However, before 2010, those concentrations were more than 0.05 mg/L, which could have led to an accumulation of Mn oxides in the distribution system. This could be one of the main reasons for black water occurrence. Therefore, regular monitoring of Mn concentration in the distribution system, flushing, and proper Mn removal at WTPs are needed, to supply clean and palatable tap water.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.10a
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• pp.205-207
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• 2008

• Journal of the Korean Chemical Society
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• v.48 no.1
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• pp.46-52
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• 2004

The effect of crystallinity on the structural stability of layered manganese oxide has been systematically investigated. While well-crystalline manganate was prepared by solid-state reaction-ion exchange method, nanocrystalline one was obtained by Chimie-Douce reaction at room temperature. According to micro-Raman and Mn K-edge X-ray absorption spectroscopic results, manganese ions in both the manganese oxides are stabilized in the octahedral sites of the layered lattice consisting of edge-shared MnO6 octahedra. The differential potential plot clarifies that the layered structure of nanocrystalline material is well maintained during electrochemical cycling, in contrast to the well-crystalline homologue. From the micro-Raman results, it was found that delithiation-relithiation process for well-crystalline material gives rise to the structural transition from layered to spinel-type structure. On the basis of the present experimental findings, it can be concluded that nanocrystalline nature plays an important role in enhancing the structural stability of layered manganese oxides.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.455-466
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• 2010

Seabed mineral resources explored by Korea are categorized into major three types of deposit; manganese nodule, manganese crust and polymetallic sulfides. Pt displays high enrichment factors (400, ore/crust ratios) in manganese nodule. Rare earth oxide content in manganese nodule ranges from 0.037 to 0.302 REO % with mean value of 0.12 REO %. Both of Te and Pt are enriched elements in manganese crust, displaying enrichment factors of 10800 and 150, respectively. Rare earth oxide's contents of manganese crust are slightly higher than manganese nodule's (0.013~0.387 REO %, average = 0.18 REO %). Se and In are outstanding rare metals from seabed polymetallic sulfides, showing enrichment factors of 1300 and 110, respectively. Au (0.8~26.3 g/t) and Ag (0.9~348.0 g/t) are another enriched elements in polymetallic sulfides. The main concern at exploiting seabed mineral resource will be a securing rare metals for high-technology industries and rare metals from subsea mineral deposits will add economic values to commodity candidates such like Co, Ni and Cu.