• Title/Summary/Keyword: Rare metals

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Refractive-index Prediction for High-refractive-index Optical Glasses Based on the B2O3-La2O3-Ta2O5-SiO2 System Using Machine Learning

  • Seok Jin Hong;Jung Hee Lee;Devarajulu Gelija;Woon Jin Chung
    • Current Optics and Photonics
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    • v.8 no.3
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    • pp.230-238
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    • 2024
  • The refractive index is a key material-design parameter, especially for high-refractive-index glasses, which are used for precision optics and devices. Increased demand for high-precision optical lenses produced by the glass-mold-press (GMP) process has spurred extensive studies of proper glass materials. B2O3, SiO2, and multiple heavy-metal oxides such as Ta2O5, Nb2O5, La2O3, and Gd2O3 mostly compose the high-refractive-index glasses for GMP. However, due to many oxides including up to 10 components, it is hard to predict the refractivity solely from the composition of the glass. In this study, the refractive index of optical glasses based on the B2O3-La2O3-Ta2O5-SiO2 system is predicted using machine learning (ML) and compared to experimental data. A dataset comprising up to 271 glasses with 10 components is collected and used for training. Various ML algorithms (linear-regression, Bayesian-ridge-regression, nearest-neighbor, and random-forest models) are employed to train the data. Along with composition, the polarizability and density of the glasses are also considered independent parameters to predict the refractive index. After obtaining the best-fitting model by R2 value, the trained model is examined alongside the experimentally obtained refractive indices of B2O3-La2O3-Ta2O5-SiO2 quaternary glasses.

Transdermal Drug Delivery Devices Based on Microneedles: A Review

  • Kim, Byeong Hee;Seo, Young Ho
    • Journal of mucopolysaccharidosis and rare diseases
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    • v.1 no.1
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    • pp.5-14
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    • 2015
  • This paper addresses the state of arts of microneedles for the transdermal drug delivery applications. Microneedles can be classified based on materials and shapes. For the materials, microneedles could be made of ceramics, metals and polymers. The shape of the microneedles can be classified into solid and hollow microneedles. Methods of transdermal drug delivery based on microneedle patch are discussed, and various fabrication methods of microneedle patches are introduced.

Correlation between rare earth elements in the chemical interactions of HT9 cladding

  • Lee, Eun Byul;Lee, Byoung Oon;Shim, Woo-Yong;Kim, Jun Hwan
    • Nuclear Engineering and Technology
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    • v.50 no.6
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    • pp.915-922
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    • 2018
  • Metallic fuel has been considered for sodium-cooled fast reactors because it can maximize the uranium resources. It generates rare earth elements as fission products, where it is reported by aggravating the fuel-cladding chemical interaction at the operating temperature. Rare earth elements form a multicomponent alloy (Ce-Nd-Pr-La-Sm-etc.) during reactor operation, where it shows a higher reaction thickness than a single element. Experiments have been carried out by simplifying multicomponent alloys for mono or binary systems because complex alloys have difficulty in the analysis. In previous experiments, xCe-yNd was fabricated with two elements, Ce and Nd, which have a major effect on the fuel-cladding chemical interaction, and the thickness of the reaction layer reached maximum when the rare earth elements ratio was 1:1. The objective of this study is to evaluate the effect and relationship of rare earth elements on such synergistic behavior. Single and binary rare earth model alloys were prepared by selecting five rare earth elements (Ce, Nd, Pr, La, and Sm). In the single system, Nd and Pr behaviors were close to diffusion, and Ce showed a eutectic reaction. In the binary system, Ce and Sm further increased the reaction layer, and La showed a non-synergy effect.

The Separation of Ce, Pr, Nd and Sm from Rare Earth Oxides (1차 분리된 희토류산화물 중 Ce, Pr, Nd 및 Sm의 분리)

  • Yong-Kuen Lee;In-Wha Woo;Young-Gu Ha
    • Journal of the Korean Chemical Society
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    • v.24 no.6
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    • pp.434-443
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    • 1980
  • The purpose of this work was to separate Ce, Pr, Nd and Sm from rare-earth oxides by column chromatography. Rare earth solution were adsorbed into the Amberlite IR-120 resin and were eluted by the ammonia alkali solution of the EDTA. As a result of determinating rare earth metals of each fraction, Ce was separated very effectively and Nd and Sm partially separaed but Pr never separated.

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A book review; "Rare earth elements in human and environmental health; at the crossroads between toxicity and safety"

  • Rim, Kyung-Taek
    • Journal of Applied Biological Chemistry
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    • v.60 no.3
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    • pp.207-211
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    • 2017
  • It is introduced an outstanding book about an important topic in occupational and environmental sciences i.e., the opportunities and challenges that may be connected with increasing the use and distribution of rare earth elements. These chemically similar elements, comprising the lanthanides, scandium, and yttrium, are involved in a number of essential technological applications, and their effects raise a number of human health issues of relevance to the occupational and environmental sciences. The book that I introduced here, "Rare Earth Elements in Human and Environmental Health; At the Crossroads between Toxicity and Safety" edited by Giovanni Pagano (Pan Stanford Publishing Pte. Ltd., Temasek Boulevard, Singapore) represents a break from that situation. It is essential to increase our knowledge about the environmental fate and biological effects of these technologically important metals in order to prevent unforeseen long-term man-made consequences to human health. This book is likely to become an important resource for scientists, engineers, and decision makers who understand the need for sensible exploitation of this resource.

Solvent Extraction of Zirconium and Hafnium from Hydrochloric Acid solution by LIX 63 and Cyanex 301 (염산용액(鹽酸溶液)에서 LIX 63 및 Cyanex 301에 의한 지르코늄과 하프늄의 용매추출(溶媒抽出))

  • Min, Soo-Hwan;Lee, Man-Seung
    • Resources Recycling
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    • v.22 no.6
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    • pp.19-25
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    • 2013
  • Solvent extraction experiments have been conducted to separate Zr(IV) and Hf(IV) from chloride solutions by using LIX63 and Cyanex301. Zr and Hf were extracted by cation exchange reaction in the pH range from 1 to 4 by the extratants. Since the extraction percentage of the two metals was similar to each other, it was difficult to separate the two metals by using LIX63 or Cyanex301. Use of a mixture of LIX63/TBP or Cyanex301/TBP resulted in antagonism in our experimental ranges. Our data showed that there is some possibility of separating the two metals by the mixture of Cyanex301 and TBP because the extraction percentage of Hf decreased more rapidly than that of Zr as HCl concentration was decreased. The mixture of LIX63 and Cyanex301 had little effect on the separation of the two metals.

Solvent Extraction of Tb(III) from Hydrochloric Acid Solution with Cyanex 272, Its Mixture and Ionic Liquid (염산용액에서 Cyanex 272 및 혼합용매와 이온성 액체에 의한 Tb(III)의 용매추출)

  • Oh, Chang Geun;Lee, Man Seung
    • Korean Journal of Metals and Materials
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    • v.56 no.12
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    • pp.870-877
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    • 2018
  • Cyanex 272 shows the highest separation factor for the rare earth elements from hydrochloric acid solution among the organophosporus acidic extractants, D2EHPA and PC 88A. Solvent extraction of Tb(III) from weak hydrochloric acid solution with an initial pH 3 to 6 was compared with Cyanex 272, its mixture with Alamine 336, and ionic liquid with Aliquat 336. The solvent extraction reaction of Tb(III) using Cyanex 272 was the same as that of light rare earth elements. Synergism was observed for the extraction of Tb(III) by the mixture with Alamine 336 when the initial concentration ratio of Cyanex 272 to Alamine 336 was higher than 5. Use of the ionic liquid led to a great increase in the extraction percentage of Tb(III) from the same initial extraction conditions. While the equilibrium pH of the mixture was always lower than the initial pH, under some conditions extraction with the ionic liquid resulted in a higher equilibrium pH than the initial pH. The loading capacity of the mixture and the ionic liquid was the same and 2.6 times larger than that using Cyanex 272 alone. Ionic liquid was recommended as a suitable extractant for the extraction of Tb(III) from hydrochloric acid solution based on the ease of handling and higher extraction percentage.

Standardization Status of Rare Earth Elements Recycling in ISO TC 298 (ISO TC 298에서의 희토류 재활용 관련 국제 표준화 현황)

  • Lee, Mi Hye;Song, Yosep;On, Ji Sun;Yoon, Seung Hwan;Han, Munhwan;Kim, Bum Sung;Kim, Taek-soo;Lee, Bin
    • Journal of Powder Materials
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    • v.29 no.2
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    • pp.159-165
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    • 2022
  • Rare earth elements, which are important components of motors, are in high demand and thus constantly get more expensive. This tendency is driven by the growth of the electric vehicle market, as well as environmental issues associated with rare-earth metal manufacturing. TC 298 of the ISO manages standardization in the areas of rare-earth recycling, measurement, and sustainability. Korea, a resource-poor country, is working on international standardization projects that focus on recycling and encouraging the domestic adoption of international standards. ITU-T has previously issued recommendations regarding the recycling of rare-earth metals from e-waste. ISO TC 298 expands on the previous recommendations and standards for promoting the recycling industry. Recycling-related rare earth standards and drafts covered by ISO TC 298, as well as Korea's strategies, are reviewed and discussed in this article.