• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.5-16
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• 1991

It was grown Cubic $ZrO_2(10 mol% Y_2O_3)$ single crystals doped with 1 wt% rare earth metal oxides (RE=Ce, Pr, Nd, Eu, Er) by Skull method. It was investigated electrical properties on (111) plane of grown single crystals by Impedance Spectroscopy. It was potted relation between temperature and electrical conductivities and observed the transition at $약300-400^{\circ}$ It was obtained activation energy on the migration of oxygen vacancy between low temperature (before the transition) and high temperature (after the transition till ${\11}500^{\circ}$) and its difference can be seen the activation energy of the formation of oxygen vacancies by break up defect complexes. It was obtained the activation energy according as add yttria and rare earth metal oxides and discussed ionic conduction mechanism. Grown single crystals showed Ce: orange - red, Pr: golden - yellow, Nd: lilac, Eu: light pink, Er: pink due to dopant effect from the light absorption data in the visible range.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.417-422
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• 2009

국내에는 충주 어래산 광화대와 홍천 광화대에 대한 탐사 결과 약 4,600,000 톤의 자원량을 확보하였으나 시추량의 제한에 따른 자원량의 부족과 낮은 가격으로 인해 경제성이 없는 것으로 잠정적으로 판단된 바 있다. 그러나 최근 희토류 가격이 2000년대 초에 비해 2~3배까지 상승하였으며 최저개발 품위가 REO 2%대로 낮아짐으로써 두 광화대에 대한 체계적인 정밀탐사를 통하여 보다 정확한 자원평가가 요구된다. 이 두 지역은 REE 뿐만 아니라 Fe, Sr 등이 수반됨으로써 그 잠재적인 가치를 높일 수 있을 것으로 판단된다. 하동 광화대는 Ti외 REE와 Li의 추출이 가능하여 경제성을 상승시킬 수 있을 것으로 판단된다. 양양 광화대는 Zr-Nb-REE 광화대로 알려져 있으나 체계적 탐사가 수행되지 않아 자원량의 산정은 수행되지 않았으나 REE 외 희유금속인 Nb을 수반하여 그 잠재적인 가치가 높다고 판단된다. 국내 REE 자원탐사는 체계적이고 계획적인 탐사가 진행 된 적이 없어 단일 광상에 대해 정확한 매장량 산정이나 경제성 분석 등이 이루어지지 않아 그 가치 판단이 모호함으로써 개발에 제한을 가지고 있다. 세계적인 수요량이 현재 REO 100,000톤에서 2013년에는 거의 200,000톤으로의 증가가 전망되고, Eu의 가격은 2000년 중반에 비해 최근 2배 상승하였으며, Dy의 가격은 3배 이상 급상승 추세에 있어 대부분 희토류 산화물 가격은 점차 증가될 것으로 전망한다. 전 세계 희토류 생산의 95%를 중국이 독점하고 있어 자원이 1개국에 편재된 극히 좋지 않은 자원환경으로 세계 각국에서 희토류 탐사에 전념하고 있는 실정이다. 아울러 하이브리드 카 생산이 증대되면 중국만이 생산하는 중희토류의 수요가 급증하여 가격 상승과 함께 수급에 차질이 있을 것으로 추측된다. 따라서 국내 희토류 자원에 대한 체계적이고 단계적인 중장기적 탐사를 통하여 REE 자원을 확보하여 개발한다면 국내 REE 자원의 수급을 원활히 할 수 있을 것으로 기대된다.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.21-25
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• 2007

In this study, the properties of Sn-0.7wt%Cu-Xwt%Re(X=$0.01{\sim}1.0$) older were investigated by using DSC(differential scanning calorimetry), wetting balance, victors hardness and tensile testers. The melting temperature of solder was increased with increasing the contents of rare earth element, and the melting temperature range of Sn-0.7Cu-($0.01{\sim}1.0$)Re solder was $233.9{\sim}234.7^{\circ}C$. The wettability with Sn-0.7Cu-0.1Re solder was higher than that of Sn-0.7Cu-0.01Re and Sn-0.7Cu-1.0Re solders, and the wettability of Sn-0.7Cu-0.1Re solder was higher than that of Sn-0.7wt%Cu-0.01w%P solder. Also, the hardness and tensile strength of solder were increased with increasing the contents of rare earth element.

• Resources Recycling
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• v.27 no.1
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• pp.22-30
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• 2018

In order to industrially recycle nickel, cobalt and rare earth elements included in waste NiMH batteries, electrode powder scraps were recovered by dismantle, crushing and classification from automobile waste battery module. As a result of leaching recovered electrode powder scrap with sulfuric acid solution, 99% of nickel, cobalt and rare earth elements were leached under reaction conditions of 1.0 M sulfuric acid solution, pulp density 25 g/L and reaction temperature $90^{\circ}C$ for 4 hours. In addition, the rare earth elements were able to separate from nickel / cobalt solution as cerium, lanthanum and neodymium precipitated under pH 2.0 using 10 M NaOH.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.440-450
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• 1992

Three type extraction processes of rare earth metal component from rare earth metal bearing ore were sulfuric acid digestion, caustic soda leaching and decomposition with $(NH_4)_2SO_4$. From the overall results, both caustic soda leaching and sulfuric acrid digestion were better extraction processes for domestic monazite ore. The proper conditions of sulfuric acid digestion for domestic monazite ore were reaction temperature $210^{\circ}C$, reaction time 40 min, weight ratio of $H_2SO_4$ to monazite ore 1.5 and concentration of $H_2SO_4$ 95%. Under these conditions, 98% of rare earth metal component was extracted and also the reasonable conditions for caustic soda leaching were reaction temperature $140^{\circ}C$, weight ratio of NaOH to monazite 3.0, concentration of caustic soda solution 50% and leaching time 3hrs. Under these conditions, 97% of rare earth metal component was extracted.

• Analytical Science and Technology
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• v.17 no.2
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• pp.108-116
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• 2004

The adsorption characteristics of raw and crosslinked chitosan for rare earth elements (REEs) have been studied. The range of optimum pH for the maximum adsorption was observed: pH 4.5~5.5 for $Nd^{3+}$, $Tm^{3+}$ on raw and crosslinked chitosan; pH 4.0~5.5 for $La^{3+}$ and $Ce^{3+}$ on crosslinked chitosan and pH 2.0 for those on raw chitosan. The adsorption rate of REE at pH 4.0 has been found in the order of $Er^{3+}$ > $Gd^{3+}$ > $Yb^{3+}$ > $Nd^{3+}$ > $Lu^{3+}$ > $Eu^{3+}$ > $Tm^{3+}$ > $Ho^{3+}$ > $Dy^{3+}$ > $La^{3+}$ > $Ce^{3+}$ > $Y^{3+}$ > $Pr^{3+}$ in single metal system and that of $Lu^{3+}$ > $Yb^{3+}$ > $Tm^{3+}$ > $Dy^{3+}$ > $Ho^{3+}$ > $Er^{3+}$ > $Eu^{3+}$ > $Gd^{3+}$ > $Nd^{3+}$ > $Y^{3+}$ > $La^{3+}=Ce^{3+}=Pr^{3+}$ in multi metal system. In the competitive adsorption of multi metal system, the amount of metal adsorption generally increased with increasing atomic number and with decreasing ionic radius. On the adsorption studies of metal ions on chitosan, the time of equilibrium adsorption which was reached at the maximum adsorption was about 5 hours. 83~95 % for $Nd^{3+}$ ion and 90~106 % for $Tm^{3+}$ ion, were recovered from the crosslinked chitosan.

• Resources Recycling
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• v.27 no.3
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• pp.8-15
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• 2018

Solvent extraction behavior of light rare earth elements (Pr, Nd) and medium rare erath elements (Tb, Dy) in the HCl-PC88A-kerosene extraction system was investigated in order to separate high-purity light rare earths (Pr, Nd) and medium rare earths (Tb, Dy) in the mixed rare earth chloride solution. In the batch test step, it was confirmed that the separation efficiency was good when the extractant concentration (PC88A) was 0.5 M, the equilibrium pH after extraction was 0.8 to 1.0 (initial pH 1.3 of the feed), the concentrations of hydrochloric acid in scrubbing solution was set as 0.1 M, the concentrations of hydrochloric acid in stripping solution was set as 2.0 M or more. Based on the experimental data obtained from the batch test, the mixer-settler was composed as follows; 4 stages of extraction, 8 stages of scrubbing, 4 stages of stripping, and 3 stages of pickling organic solution. The Mixer-settler was operated for 180 hours, and the operating conditions were continuously adjusted to obtain the high-purity light/medium rare earths. Finally, the purity of light (Pr, Nd) and medium rare earth elements (Tb, Dy) was reached as 3 N class.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.12a
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• pp.238-239
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.50-51
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• 2013

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.304-308
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• 1989

The spectrophotometric determination of $Lu^{3+},\;Eu^{3+}$ and some other rare earths have been investigated using Methyl Thymol Blue(MTB) as spectrophotometric reagent. Rare earth elements form a stable complex with MTB abount pH 6.5 and the ratio of its complex is 1 to 1. MTB has a absorption maxima at 440nm and rare earth MTB complex has absorption maxima 610nm at pH 6.5, respectively. The absorbance of the rare earth MTB complex is stable in 7 hours after color developing and obey the Beer law in the range of $0{\sim}110{\mu}g/50ml$. The ligand such as phosphate, citrate and EDTA decrease the absorbance of its complex considerably, and this method has a poor selectivity of each rare earth element and the molar absorptivity is $1.2{\sim}2.0{\times}10^4mol^{-1}{\cdot}l{\cdot}cm^{-1}$. In methyl alcohol, ethyl alcohol and acetone medium we did not find out any absorption change of the rare earth MTB complex.