• Economic and Environmental Geology
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• v.36 no.6
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• pp.407-413
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• 2003

The geology of the Apdong Nb-Ta deposit, is hosted by alkali metasomatites, consist of Upper Proterozoic sedimentary rocks, alkali syenites(Hoamsan intrusive) of Phyonggang Complex(late Paleozoic to early Mesozoic), Jurassic granite and Quaternary basalt. Alkali syenites are distinguished as alkali amphibole-pyroxene syenite, alkali amphibole-biotite syenite, biotite-nepheline syenite, biotite syenite, and quartz-alkali amphibole-pyroxene syenite. Alkali metasomatites are the products of intense post-magnatic metasomatism, and form the Nb-Ta ore bodies as the belt, irregular vein and lenticular types in the southern part of Hoamsan intrusive. The ore mineralization is characterized by the occurrence of pyrochlore, zircon, and small amounts of columbite, fergusonite. magnetite, fluorite, molybdenite, ilmenite, titanite, apatite, and monazite. Pyrochlore is one of the niobium/tantalum oxides and contains substantial amounts of rare earths and radioactive elements. The compositional varieties of pyrochlore can be defined: (1) enriched in tantalum, uranium and cerium, (2) substantially tantalum- and fluorine-poor, and (3) enriched in thorium or barium. The geochemical characteristics, ore textures and mineral occurrences indicate that alkali metasomatism of the mineralizing fluid was the dominant ore-forming process.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.496-503
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• 1989

The chemical behavior of trivalent lanthanide (Pr(III) and Yb(III)) and 2, 2, 6, 6-tetramethyl-3, 5-heptanedione(dipivaloylmethane) complexes was investigated by the use of direct current, differential pulse polarography and cyclic voltammetry. In this study, it was founded that the reduction of trivalent lanthanide complexes was observed by one electron transfer process at Epc = -0. 13 V and -0.80 V of Pr(III), and -0.02 V of Yb(III) vs. Ag-AgCl electrode. Also, it was founded that the treatment of DP and CV to the case of a first-order chemical equilibrium reaction preceding a reversible and irreversible one electron transfer reaction, (a >0. 5) the socalled ErCr electrode process. The equilibrium constant (lnK) obtained, of various solvents, these constant were founded to be increases with decreasing dielectric constant of the solvents. Plots of lnK for these reaction against ln(l/D) for the solvents was fairly straight lines, and the behavior of the heavier lanthanides was decreased equilibrium constant with increasing atomic number.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.653-659
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• 1994

The fluorescence intensities of europium and samarium can be greatly enhanced in the presence 2-thenoyltrifluoroacetone(TTA), n-octanol and Triton X-100 in aqueous solution of pH 7. It was also found that the fluorescence intensity can be greatly increased by the addition of excess of $La^{3+}$. The excitation and emission wavelengths of europium and samarium were 345 nm, 380 nm and 617 nm, 567 nm, respectively. The fluorescence intensity was a linear function of the concentration of europium and samarium in the range TEX>$1{\times}10^{-7}∼1{\tiems}10^{-9}\;M,\;1{\tiems}10^{-5}∼1{\times}10^{-7}\;M$, respectively, and the detection limits were 1$1{\times}10^{-11}\;M$ for europium and $1{\times}10^{-8}\;M$ for samarium and the luminescence mechanism of the system is discussed.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.43-48
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• 2018

An etchant capable of forming a circuit in an FTO film that can replace ITO, which depends on full imports, was prepared. The etching solution is composed of 1 to 30% by weight of fluoride, 1 to 20% by weight of acid, 0.5 to 5% by weight of surfactant, 5 to 20% by weight of solvent, 0.5 to 10% by weight of corrosion inhibitor and the balance of water. This etchant can be etched using a dry film, thereby reducing the cost, and is free from bubbles and residue of the etchant. The characteristics of the etchant were etched in a time of 2 minute with a 100 nm thick FTO, and the etchant temperature was maintained at $50^{\circ}C$. An undercut of -0.00364% was obtained when put into a 2 minute etching solution. No harmful substances such as Cd, Pb, Hg and Cr components were measured. The use of FTO in Korea where rare earths do not exist can achieve localization and import substitution effect.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.41-53
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• 2022

After industrialization has been started, mankind needs and consumes more resources. Now, the resources depletion is a serious problem in the Earth. However, there are infinite resources in the Space. Especially, the Moon is the closest planet and has much resources, including Helium-3 and rare earths, which are needed to human being in the future. Humanity needs to reside on the moon to harvest these resources. For the resident, much resources, such as food, construction, and industrial materials, are needed. However, to transport these resources to the Moon from the Earth, an astronomical cost should be consumed. Thus, research is underway to support human activities by procuring resources locally. This is called In-Situ Resources Utilization (ISRU), which is the essential technology for the space development. In this paper, the reason why ISRU is essential and the its status are introduced and future research projects will be explained.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.358-370
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• 1988

Several new ion exchange resins have been synthesized from chloromethyl styrene-1,4-divinylbenzene(DVB) with 1%, 2%, 4%, 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, rare earths 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 have good resistance to heat at $280^{\circ}C$. The $UO_2^{+2}$ aqueous solution are 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 $UO_2^{2+},\;Cu^{2+}\;and\;Nd^{3+}$.

• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.618-622
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• 2004

Excitation spectra of the 1.6 rm emission originating from $Ho^{3＋}$：$^{5}$ I$_{5}$ \longrightarrow$^{5}$ I$_{7}$ transition in fluoride, sulfide, and selenide glasses were measured at wavelengths around 900nm where the fluorescing $^{5}$ I$_{5}$ level is located. In specific energy range where the frequency upconversion populating $^{5}$ F$_{1}$ state happens, the excitation efficiency of the 1.6 fm emission was deteriorated in fluoride and sulfide hosts. In selenide however spectral line shapes of the excitation spectrum and the '$^{5}$ I$_{8}$ \longrightarrow$^{5}$ I$_{5}$ absorption spectrum looked seemingly identical to each other. Differences in optical nonlinearity as well as electronic band gap energy of the host glasses used are responsible for the experimental observations. On the other hand, codoping of rare earths such as Tb$^{3+}$, Dy$^{3+}$, Eu$^{3+}$, and Nd$^{3+}$ was effective in decreasint the terminating $^{5}$ I$_{7}$ level lifetime. However, at the same time, some of the codopants increased unnecessary absorption at the 1.6 $\mu$m wavelengths via their ground state absorption. Though the lifetime quenching effect of Eu$^{3+}$ was moderate, it exhibited no additional extrinsic absorption at the 1.6 $\mu$m band.EX>m band.

• Resources Recycling
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• v.26 no.5
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• pp.12-21
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• 2017

Red mud generated in the alumina manufacturing process contains various valuable resources, but it is not comprehensively recycled yet causing severe environmental problems. In Korea, red mud is producing about 200,000 tons annually and most of them are landfilled or disposed. Red mud's recycling technology is also being developed in many countries, but red mud's recycling technologies are still lacking compared to the production rate. In this study, we analyzed the characteristics and the amount of red mud, and the current status and technology development trend. Red mud has shown that recycling studies are being carried out in fields such as construction, recycling, metal recovery, adsorbent, and pollution stabilization. In particular, technologies for recovering rare earths have been developed as worldwide because of their high economic value. The data analyzed in this study will be used as basic data for the further development of technologies in the future.