• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 2000년도 Proceedings of 2000 International Nano Crystals/Ceramics Forum and International Symposium on Intermaterials
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• pp.65-86
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• 2000

Rare earth-doped ceria powders with a composition of Ce0.8R0.2O1.9(R=Yb, Y, Gd, Sm, Nd and La) were prepared by heating the oxalate coprecipitate. The green compacts began to shrink at 600$^{\circ}$-700$^{\circ}C$. The relative density after the sintering at 1200$^{\circ}$ and 1400$^{\circ}C$ became higher for the higher green density. The samples were densified above 98% relative density by the sintering ant 1600$^{\circ}C$ for 4 h and the grain sizes (4.7-7.6$\mu\textrm{m}$) showed a tendency to become larger with increasing ionic radius of doped-rare earth element. In the intial stag of sintering at 700$^{\circ}$-800$^{\circ}C$, the dominant mass transport process changed from lattice diffusion to grain boundary diffusion to grain boundary diffusion with heating time. The porosity during the intermediated and final stage of the sintering at 1200$^{\circ}$ and 1400$^{\circ}C$ decreased by the mass transport through lattice diffusion with grain growth.

• 한국주조공학회지
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• 제23권4호
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• pp.187-194
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• 2003

The effect of rare earth elements (R.E)(from 0.0 to 0.04%) on the microstructure formation and mechanical properties of thin-wall ductile iron castings were investigated. Tensile strength and hardness were decreased with an addition of up to 0.03% rare-earth elements. After addition of more than 0.03%, those were increased. Graphite nodule sizes were the finest, nodule count was the highst regardless of thickness and volume fraction of ferrite was the largest when that was 0.02%. However, the nodule count was decreased with increasing R.E. Futhermore. nodule size increased with increasing thickness and the volume fraction of ferrite decreased as that was increased. Nodularity was increased regardless of the thickness as that was increased. The castings of minium thickness up to 3 mm was possible without the formation of chill.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2926-2936
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• 2021

Rare-earth (RE) industries generate a massive amount of radioactive residue containing high thorium concentrations. Due to the fact that thorium is considered a non-economic element, large volume of these RE processed residues are commonly disposed of without treatment. It is essential to study an appropriate treatment that could reduce the volume of waste for final disposition. To this end, this research investigates the applicability of carbon-based adsorbent in separating thorium from aqueous phase sulphate is obtained from the cracking and leaching process of solid rare-earth by-product residue. Adsorption of thorium from the aqueous phase sulphate by carbon-based electrodes was investigated through electrosorption experiments conducted at a duration of 180 minutes with a positive potential variable range of +0.2V to +0.6V (vs. Ag/AgCl). Through this research, the specific capacity obtained was equivalent to 1.0 to 5.14 mg-Th/g-Carbon. Furthermore, electrosorption of thorium ions from aqueous phase sulphate is found to be most favorable at a higher positive potential of +0.6V (vs. Ag/AgCl). This study's findings elucidate the removal of thorium from the rare-earth residue by carbon-based electrodes and simultaneously its potential to reduce disposal waste of untreated residue.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1565-1570
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• 2020

Photons with the energy of 60 keV are regularly used for some kinds of bone density examination devices, like the single photon absorptiometry (SPA). This article reports a flexible and lightweight rare earth/polymer composite for enhancing shielding efficiency against photon radiation with the energy of 60 keV. Lead oxide (PbO) and several rare earth element oxides (La₂O₃, Ce₂O₃, Nd₂O₃) were dispersed into natural rubber (NR) and the photon radiation shielding performance of the composites were assessed using monte carlo simulation method. For 60 keV photons, the shielding efficiency of rare earthbased composites were found to be much higher than that of the traditional lead-based composite, which has bad absorbing ability for photons with energies between 40 keV and 88 keV. In comparison with the lead oxide based composite, Nd₂O₃-NR composite with the same protection standard (the lead equivalent is 0.25 mmPb, 0.35 mmPb and 0.5 mmPb, respectively), can reduce the thickness by 35.29%, 37.5% and 38.24%, and reduce the weight by 38.91%, 40.99% and 41.69%, respectively. Thus, a flexible, lightweight and lead-free rare earth/NR composite could be designed, offering efficient photon radiation protection for the users of the single photon absorptiometry (SPA) with certain energy of 60 keV.

• 분석과학
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• 제10권1호
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• pp.53-59
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• 1997

$Cl^-$형 음이온 교환수지에서 희토류-EDTA 용리액을 사용하여 희토류 원소 혼합물 중의 원하는 한 원소를 분리 회수하는 연구를 하였다. 음이온 교환수지에 $Sm^{3+}$, $La^{3+}$, $Ce^{4+}$의 EDTA-착물을 흡착시키고, Sm-EDTA 용액으로 용리시키면, 수지에 흡착된 희토류 원소 중 $Sm^{3+}$ 외의 희토류 원소는 용리된다. 수지에 남아 있는 $Sm^{3+}$는 단계적으로 1M HCl 용액으로 용리시켜 분리하였다. Sm-EDTA 용액 대신 La-EDTA 용액으로 용리시키면 $Sm^{3+}$과 $Ce^{4+}$이 $La^{3+}$과 같이 용리되어 완전한 분리가 되지 않았고, Ce-EDTA 용액으로 용리시킬 때도 분리가 불가능하였다. Sm-EDTA 용액으로 용리시킬 때 용리 구조는 다음과 같다. 흡착과정 : $RCl+Ln-Y^-{\leftrightarrows}RLnY+Cl^-$, Sm-EDTA 용리 : $RLnY+Sm-Y^-{\leftrightarrows}RSmY+Ln-Y^-$, HCl 용리 : $RSmY+HCl{\leftrightarrows}RCl+Sm-Y^-$.

• Journal of Magnetics
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• 제18권3호
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• pp.365-369
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• 2013

Coal ash is known to contain a noticeable amount of valuable elements, including transition metals and lanthanides. Therefore it is quite actual problem to extract them for metallurgy and other applications. This paper presents the results of high gradient magnetic and mechanical separation, microscopy, element analyses and optical spectroscopy of brown coal ash taken from the combustion camera and chimney-stalk of Angren thermal power station. The separated magnetic fraction was 3.4 wt.%, where the content of Fe in ferrospheres increased to 58 wt.%. The highest contents of Fe and rare earth elements were found in the fine fractions of $50-100{\mu}m$. Optical absorption spectroscopy of water solutions of the magnetic fractions revealed $Fe^{2+}$ and $Fe^{3+}$ ions in the ratio of ~1:1. The separated coal ash could be used for cleaning of technological liquid waste by means of the high gradient magnetic field.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2004년도 춘계총회 및 연구발표회 초록집
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• pp.35.3-35.3
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• 2004

• 한국세라믹학회지
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• 제41권9호
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• pp.696-702
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• 2004

찰코지나이드 유리에 첨가된 희토류 원소의 4f 전자 궤도를 구성하는 여기 상태 에너지 준위의 수명은 기지 재료의 단거리 구조 변화뿐만 아니라 중거리 구조 변화에도 매우 민감하다 Pr$^{3+}$ 이온을 첨가한 다양한 조성의 Ge-Sb-Se 계열 찰코지나이드 샘플을 대상으로 Pr$^{3+}$ ($^3$F$_3$, $^3$F$_4$)\$\longrightarrow$$^3$H$_4$천이로부터 발생하는 1.6$\mu\textrm{m}$ 형광의 수명을 측정한 결과, 해당 형광 수명은 mean coordination number가 -2.67이 되는 조성에서 최대 값을 나타내었다. 이는 유리의 구조가 2차원 구조에서 3차원 구조로 전환됨에 따라 희토류 이온의 분포도가 변화하기 때문이며 소위 topological structure 모델과 chemically ordered network모델로써 공유 결합성이 강한 찰코지나이드 유리에 첨가된 희토류 이온의 발광 특성에 대한 해석이 가능하였다. 이러한 결과는 희토류 원소의 분포 및 형광 수명을 단지 찰코지나이드 재료의 성분비만으로 예측할 수 있다는 새로운 관점이 타당함을 의미한다

• 한국환경과학회지
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• 제18권6호
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• pp.621-632
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• 2009

Rare earth contents(REE) were analysed for the plants, M. sinensis. A. vulgaris and R. crataegitolius, from two different soils serpentine area consisting of serpentinite(SP) and non-serpentine area, containing amphibole schist(AS) of Gapyeong area, and were compared with soils and host rocks. The AS were high with the differences of several times in the top soils, and with the differences of several to ten times in the host rocks relative to the SP. In the same area, the SP were high in the soil, but the rocks for the AS. In the plants, the A. vulgaris were high, but low in the R. crataegitolius. Root parts were higher than the upper parts. Differences between the upper and root parts were big in the SP rather than the AS, and were big in the R. crataegitolius, but small in the M. sinensis. Among the parts of the plants, high elements were shown in the R. crataegitolius of the SP, and the A. vulgaris and M. sinensis of the AS. In the correlation coefficients, most of the REE showed positive relationships among the element pairs, especially high positive correlation coefficients in the upper parts of the SP.Differences of the soils and plants(average) were smalle in the M. sinensis and big in the R. crataegitolius. In the upper parts. contents of the A. vulgaris were close to the soils while the R. crataegitolius showed large discrepancies with the soils. In the root parts, contents of the A. vulgaris showed discrepancies with the soils regardless of soil types, but close in the R. crataegitolius of the SP and M. sinensis of the AS.

• 마이크로전자및패키징학회지
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• 제14권4호
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• pp.21-25
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• 2007

본 연구에서는 시차주사열량법, 젖음성 시험기, 비커스 경도계와 인장 시험기를 이용하여 Sn-0.7wt%Cu-Xwt%Re(X=$0.01{\sim}1.0$) 솔더의 특성에 관하여 평가하였다. 희토류 금속의 함량이 증가함에 따라 솔더의 용융 온도가 약간 상승하는 경향을 나타내었으나 $0.01{\sim}1.0%$의 희토류 금속이 첨가된 범위에서는 $233.9{\sim}234.7^{\circ}C$의 작은 용융 온도 범위를 갖는 것을 확인할 수 있었다. 솔더의 젖음성 시험 결과로부터 Sn-0.7Cu-0.1Re 솔더의 젖음성이 다른 솔더보다 우수한 것을 확인할 수 있었으며, Sn-0.7Cu-0.1Re 솔더의 젖음성이 Sn-0.7wt%Cu-0.01wt%P 솔더보다 우수한 것을 확인할 수 있었다. 또한 희토류 금속의 함량이 증가할수록 솔더의 경도와 인장 강도가 증가하는 경향을 확인할 수 있었다.