• Title/Summary/Keyword: rare earth element

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Sintering and Grain Growth of Rare Earth-Doped Ceria Particles

  • Sameshima, Soichiro;Higashi, Kenji;Hirata, Yoshihiro
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • 2000.06a
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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.

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Effect of Rare Earth Elements on the Microstructures of Thin-Wall Ductile Iron Castings (희토류원소에 의한 박육구상흑연주철품의 조직변화)

  • Kim, Ji-Yeong;Choi, Jun-Oh;Park, Sung-Tak;Han, Yun-Sung;Choi, Chang-Ock
    • Journal of Korea Foundry Society
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    • v.23 no.4
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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.

Investigation of thorium separation from rare-earth extraction residue via electrosorption with carbon based electrode toward reducing waste volume

  • Aziman, Eli Syafiqah;Ismail, Aznan Fazli;Muttalib, Nabilla Abdul;Hanifah, Muhammad Syafiq
    • Nuclear Engineering and Technology
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    • v.53 no.9
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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.

Enhanced photon shielding efficiency of a flexible and lightweight rare earth/polymer composite: A Monte Carlo simulation study

  • Wang, Ying;Wang, Guangke;Hu, Tao;Wen, Shipeng;Hu, Shui;Liu, Li
    • Nuclear Engineering and Technology
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    • v.52 no.7
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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.

Separation of Rare Earth Elements Using Ln-EDTA Eluent in an Anion Exchanger (음이온 교환수지에서의 희토류-EDTA 용리액에 의한 희토류 원소의 분리)

  • Cha, Ki-Won;Park, Chan-Il;Chang, Byung-Doo;Hong, Sung-Wook
    • Analytical Science and Technology
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    • v.10 no.1
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    • pp.53-59
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    • 1997
  • Chloride form anion exchange resin was used to separate one of the elements from the rare earth mixture using respectable Ln-EDTA eluent. $Sm^{3+}$, $La^{3+}$ or $Ce^{4+}$ complexed with EDTA was passed through the resin column and eluted with a Sm-EDTA solution as an eluent. Here all the rare earth element ions except $Sm^{3+}$ were passed. Adsorbed $Sm^{3+}$ in resin was eluted with 1.0 M HCl solution. If La-EDTA solution as an eluent was used to separate lanthanum ions, lanthanum ions were eluted together with other rare earth elements. When Ce-EDTA solution was also used for separation of $Ce^{4+}$, it was eluted in the region of other rare earth elements. In the case of Sm-EDTA elution, the elution mechanism was as follows : Absorption : $RCl+Ln-Y^-{\leftrightarrows}RLnY+Cl^-$, Sm-EDTA elution : $RLnY+Sm-Y^-{\leftrightarrows}RSmY+Ln-Y^-$, HCl elution : $RSmY+HCl{\leftrightarrows}RCl+Sm-Y^-$.

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Content and Distribution of Transition Metals and Rare Earth Elements in Magnetically and Mechanically Separated Brown Coal Ash

  • Malikov, Sh.R.;Pikul, V.P.;Mukhamedshina, N.M.;Sandalov, V.N.;Kudiratov, S.;Ibragimova, E.M.
    • Journal of Magnetics
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    • v.18 no.3
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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.

Amorphous Chalcogenide Solids Doped with Rare-Earth Element : Fluorescence Lifetimes and the Glass Structural Changes (희토류 원소 첨가 비정질 찰코지나이드 : 형광 수명과 유리 구조 변화의 관계)

  • Choi Yong Gyu
    • Journal of the Korean Ceramic Society
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    • v.41 no.9
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    • pp.696-702
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    • 2004
  • Lifetime of excited electronic states inside the 4f configuration of rare-earth elements embedded in chalcogenide glasses is very sensitive to medium-range structural changes of the host glasses. We have measured lifetimes of the 1.6$\mu\textrm{m}$ emission originating from Pr$\^$3+/ : ($^3$F$_3$, $^3$F$_4$)\longrightarrow$^3$H$_4$ transition in amorphous chalcogenide samples consisting of Ge, Sb, and Se elements. The measured lifetimes fumed out to have their maximum at the mean coordination number of -2.67, which arises accordingly from structural changes of the host glasses from 2 dimensional layers to 3 dimensional networks. This new finding supports that the so-called topological structure model together with chemically ordered network model is adequate to explain relationship between the emission properties of rare-earth elements and the medium-range structures of amorphous chalcogenide hosts with a large covalent bond nature. Thus, it is validated to predict site distribution and lifetime of rare-earth elements doped in chalcogenide glasses simply based on their mean coordination number.

Differences of Rare Earth Element Concentrations of Plants in Top Soils of Gapyeong Serpentine Area: Based on the M. sinensis, A. vulgaris and R. crataegitolius (가평 사문암 지역의 토양 별 식물체내 희토류 원소 함량 차이: 억세, 쑥, 산딸기를 근거로)

  • Song, Suck-Hwan;Shin, Byung-Cheol
    • Journal of Environmental Science International
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    • v.18 no.6
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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.

Study on Characteristics of Sn-0.7wt%Cu-Xwt%Re Solder (Sn-0.7wt%Cu-Xwt%Re 솔더의 특성에 관한 연구)

  • Noh, Bo-In;Won, Sung-Ho;Jung, Seung-Boo
    • 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.

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