• Korean Journal of Materials Research
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• v.8 no.8
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• pp.720-725
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• 1998

As a basic study on the production of $Sm_{2}Fe_{17}N_{x}$ system rare earth permanent magnet by the reduction and diffusion(R- D) process, firstly the reduction reaction of $Sm_2O_3$ by metallic Ca and diffusion of Sm into Fe powder was investigated for the production the $Sm_{2}Fe_{17}$intermetallic compound. We concluded that the former case was very rapidly completed under the high temperature greater than 100$0^{\circ}C$ and the latter case of completion of diffusion reaction of Sm into the center of Fe powder(perfect homogenization condition) was required through 3h R- D reaction at 110$0^{\circ}C$ and identified as a rate determining step(RDS) on the whole reaction. Though $SmFe_2,SmFe_3$, and $Sm_{2}Fe_{17}$phases in the growth of phases of intermetallic compound in the Sm - Fe binary system were obseved below 100$0^{\circ}C$, but only $Sm_{2}Fe_{17}$phase was observed at lIOO$^{\circ}C$. Oxygen and Ca contents of the final sample in this work were 0.72wt% and O. 11 wt% respectively.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.182-186
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• 2003

A new axial pressing method using pulse magnetizing field was studied to improve the remanence of Nd-Fe-B sintered magnets. In order to make near-net shape green compacts of butterfly, disk, or coin magnets, conventional axial-type pressing has been normally used. However, compared to the transverse-type pressing, it is not possible to obtain higher remanence by this method because the magnetic alignment of powder begins to deteriorate when the density of green compacts increases over a critical value. On the other hand, we found that an axial pressing under pulse magnetizing field was very effective to increase the degree of magnetic alignment of powder, yielding remanences even higher than those obtained by the transverse pressing. In this study, it was revealed that appropriate tapping density and how to apply pulse magnetic held were important to improve the grain alignment and thus remanence of Nd-Fe-B sintered magnet.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.433-441
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• 1999

This paper presents a S-FES(Superconducting magnetic becuing Flywheel Energy Storage System) for the p purpose of replacing battery used to store the energy. Especially, the design elements of FES, such as the b beming, wheel mateηaI, and power converter, etc., are described. The design and manufacturing techniques of t the controllable IXlwer converter are proposed to generate the sinusoidal output current in the high speed operation and to get the const빠synchronous motor with halbach cuTay of high coesive I\d-Fe-B permanent magnet is used as the driver of F FES. The proposed S-FES system shows the stable rotation characteristics at high speed range about l 10,000[rpm]. To verify the validity of proposed system, the comparative study with the conventional ball b beming s~rstem is proceeded and it is well confirmed with the result of the lower friction losses of S-FES S system.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.609-614
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• 2001

This study was carried out to obtain a basic data on the production of the Nd-Fe-B system rare earth anisotropic bonded magnet by R-D & HDDR process. The reduction reaction of Nd$_2$O$_3$by metallic Ca and the diffusion reaction of Nd into Fe-B alloy powder were investigated for the production the Nd-Fe-B alloy powder. We concluded that a proper quantity of metallic Ca was about 1.3 times of theoretical equivalent from the yields of Nd and B after the R-D reaction at 100$0^{\circ}C$ for 1h. In the XRD analysis the diffusion reaction of Nd into the center of Fe-B alloy powder for the completed homogenization was required through about 45min at 110$0^{\circ}C$ for the R-D reaction, and also the maximum efficiency on the yield of Nd was obtained with such a condition. Residual Ca and oxygen contents of the final powder sample after washing were detected in 0.17wt% and 0.42wt% by ICP and oxygen analyzer, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.171-171
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• 2013

최근에 희토류 이온이 도핑된 형광체를 램프, 플라즈마, 디스플레이 패널, 음극선관, 광전 소자에 응용하기 위한 연구에 많은 노력이 경주되고 있다. 특히 희토류 이온은 4f-껍질에 존재하는 전자의 독특한 성질 때문에 좁은 밴드폭과 강한 발광 특성을 나타내므로 발광 다이오드, 자석, 촉매, 디스플레이 패널용 형광체로 개발되고 있다, 본 연구에서는 고효율의 녹색과 적색 형광체를 개발하기 위하여 모체 결정은 SrSnO3, 활성제 이온은 Eu (유로퓸) 와 Tb (테르븀)을 선택하여 도핑하였다. 합성된 형광체 분말의 회절상을 XRD로 측정한 결과에 의하면, Eu3+와 Tb3+의 함량비에 관계없이 모든 세라믹 분말은 JCPDS #74-1298에 제시된 회절상과 일치하였으며, 주 피크는 $31.3^{\circ}$, $44.9^{\circ}$, $55.8^{\circ}$에서 최대값을 갖는 (110), (200), (211)면에서 발생한 회절 신호이며, 이밖에도 $22.04^{\circ}$, $65.4^{\circ}$, $74.3^{\circ}$에서 약한 회절 피크를 갖는 (100), (220), (013)면의 신호들이 관측되었다. Eu3+ 이온의 함량비가 0.05 mol 인 경우에 (110)과 (211) 피크의 세기가 최대값을 나타내었고, Eu3+의 함량비가 증가함에 따라 두 피크의 세기는 점점 감소하였다. XRD의 데이터를 Scherrer의 식에 대입하여 계산한 결정 입자의 크기는 Eu3+ 이온이 도핑된 경우에는 0 mol에서 최소의 크기를 나타내었고, Tb3+ 이온이 도핑된 경우에 입자의 크기는 0.05 mol에서 최소이었고 0 mol에서 최대값을 보였다. SEM으로 촬영한 표면 형상의 변화를 관측한 결과, Eu3+의 함량비가 0.15 mol인 경우에, 결정 입자의 평균 크기는 400~450nm이며, Tb3+의 함량비가 0.05 mol인 경우에, 결정 입자의 평균 크기는 270~290nm 이었으며, 입자의 형상은 균일하게 분포하는 구형 형태을 보였다. Eu3+와 Tb3+ 이온의 함량비가 점점 증가함에 따라 미립자들이 서로 뭉쳐져서 각각 약 720 nm와 580 nm의 크기를 갖는 큰 입자를 형성하였고, 불규칙적인 분포를 나타내었다. 여기 파장 293 nm에서 Tb3+가 도핑된 SrSnO3:Tb3+ 형광체 분말의 발광 스펙트럼을 측정한 결과에 의하면, Tb3+의 함량비에 관계없이 모든 시료는 주 피크인 550 nm (녹색)와 상대적으로 세기가 약한 500, 590, 630 nm에서 발광 스펙트럼을 나타내었다. 주 피크의 발광 세기는 0.01 mol~0.15 mol에서는 증가 하였고, 더욱 함량비를 증가함에 따라 급격하게 감소하였다. 이 현상은 활성제 이온의 mol 비가 증가함에 따라 이온 사이의 거리가 가까워져서 서로 뭉치는 현상이 주도적으로 작용하여 발광의 세기가 현저히 감소하는 것으로 판단된다. 0.10 mol 일 때 세기가 가장 강한 녹색 형광 신호를 얻었다. 여기 파장 400nm에서 Eu3+가 도핑된 SrSnO3:Eu3+ 형광체 분말의 형광 스펙트럼은 Eu3+의 함량비에 관계없이 590, 619, 696 nm에서 관측되었다. Eu3+의 몰 비가 0.01~0.05 mol 영역에서 619 nm가 주 피크이나, 몰 비가 더욱 증가함에 다라 주 피크의 파장은 590 nm로 이동하였다. 한편, 696 nm의 발광세기는 몰 비가 증가함에 따라 더욱 증가하였다.

• Resources Recycling
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• v.23 no.2
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• pp.3-16
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• 2014

Car exhaust $CO_2$ gas reduction and fuel efficiency of the car lighter for the current era is a big challenge. The developments of high-performance Nd magnets, Li-ion secondary battery and exhaust gas purification performance of PGM catalysts used in the lightweight EV and HEV are activated. Country in order to improve the car lighter and function that use the resources of rare metals are ubiquitous imported from China because of export supply control, as soaring prices have unstable supply and demand. Compared to the emissions from the next-generation automotive recycling, waste scarce resources need to be. This study investigated the recycling technology analysis and development of the information technology, or delivered to the researchers by giving national car industry aims to contribute to the development. Findings, pulmonary high-performance motor vehicle emissions in the exhaust gas purification PGM Catalysts, Li-ion battery and Nd magnets recycling technology, such as pre- and post-processing techniques to classify technology, pre-urban mining technology mechanical separation by screening techniques under development, the study and post-processing technology has, pyro and hydro metallurgical smelting technology is established. Waste Recycling in terms of economic efficiency of mechanical components for the intensive study of screening techniques is needed.

• Journal of the Korean Magnetics Society
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• v.26 no.4
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• pp.115-118
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• 2016

We investigated the magnetocrystalline anisotropy of pure ${\alpha}^{{\prime}{\prime}}-Fe_{16}N_2$ by using full-potential linearized augmented plane wave method (FLAPW). A very high magnetic moment was obtained for Fe (4d) site due to the lattice expansion in the z-direction, while the magnetic moment of Fe (4e) and (8h) site were suppressed due to hybridization with neighboring N atom. The calculated spin magnetic moments for different Fe sites (4d, 4e and 8h) were in good agreement with previously reported values. Due to the tetragonal distortion, we found a very large uniaxial anisotropy constant of $0.58MJ/m^3$. Besides, a high value of magnetization of 1.76MA/m was obtained. In additon, the estimated coercive field and maximum energy product of 6.51 kOe and 71.7 MGOe were obtained for pure ${\alpha}^{{\prime}{\prime}}-Fe_{16}N_2$. This may suggest that the ${\alpha}^{{\prime}{\prime}}-Fe_{16}N_2$ can be utilized for potential rare-earth free permanent magnet material.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.519-527
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• 2005

Statement of problem : There are many articles that showed that the magnetism affected the bone formation around titanium implant. It means that a proper magnetism made the osseointegration improved around the implant. So after additional research on the other effect of magnetism on bone formation in implant therapy, we can conclude its possibility of clinical application on implant treatment. Purpose: The purposes of this study were to find out the intensity of magnetic field where magnetism in the titanium implant specimen inserted into the bone could affect the bone formation, and to discover the possibility of clinical application in the areas of dental implants and bone grafts. Material and method: Ten adult male rabbits(mean BW 2Kg) were used in this study. Titanium implant specimens were surgically implanted on the mesial side of the tibia of rabbits. Neodymium magnets(Magnedisc 500, Aichi Steel Corp. Japan) were placed into the implants of experimental group except control group, just after placement of the titanium implants. At 2, 4 and 8 weeks after the surgery, the animals were sacrificed, specimens were obtained and stained with Hematoxylin-Eosin for light microscopic evaluation and histomorphometric analysis. Conclusion : The results were as follows: 1. In radiographic findings, increased radiopacity downward from crestal bone was observed along the titanium implant specimen at experimental period passed by 2, 4, and 8 weeks in both control and experimental group. 2. In histoiogic findings, increased new bone formation was shown in both control and experimental group through the experiment performed for 2, 4, and 8 weeks. More new bone formation and bone remodeling were shown in experimental group. 3. In histomorphometric analysis, the bone contact ratios were 11.9% for control group and 38.5% for experimental group (p<0.05).

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.155-155
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• 2011

신재생에너지 수요가 확대됨에 따라 신재생에너지 관련 제품에 소요되는 물질에 대한 관심이 확대되고 있다. 이들 물질은 공급리스크가 존재하는 희유금속이 주를 이루고 있다. 본 연구에서는 신재생에너지 등의 high tech 기술 확대로 인한 희유금속의 수요 및 공급을 전망하고 있는 미국의 critical raw material 관리 전략을 살펴보고자 한다. 미국은 2010년 12월 미국 에너지성(DOE : Department of Energy)에서 위기 물질 전략(Critical Materials Strategy)에 관한 리포트를 공표하였다. 클린 에너지 기술 4개 분야(영구자석, 선진 전지, 태양전지 박막, 형광 물질)에서 핵심이 되는 물질(희유금속 등)의 수급 불균형이 일어날 가능성에 대해 조사를 실시하여 리스크 평가하여 단기, 중단기로 구분하여 위기물질을 선정하였다. 클린 에너지 기술 4개 분야에서 핵심이 되는 물질(네오디움, 디스프로슘, 코발트, 리튬, 랜턴, 세륨, 테룰, 인듐, 갈륨, 유로피움, 테르비움, 이트륨)의 12광종 수급을 2025년까지 전망한 결과 전체적으로 단기(2010년~2015년)보다 중기(2015년~2025년)에 공급 부족이 확대한다고 예측되었다. 단기적으로는 인듐이 약간 부족하는 것 외에 디스프로슘과 이트륨에 관해서도 공급 부족할 것으로 예측되었다. 중기적으로는 코발트(전지 기술에 사용)와 유로피움(고효율 조명용의 형광 물질에 사용) 외 대상이 된 다른 모든 물질은 공급 부족이 발생할 것으로 전망되었다. 이를 종합하여 단기적으로는 디스프리슘, 유로피움, 인듐, 테르븀, 네오디움, 이트륨 등이, 중기적으로는 디스프리슘, 유로피움, 테르븀, 네오디움, 이트륨 등이 위기물질(Critical Material)로 분석되었다. 에너지성은 위기물질을 공급원다각화, 대체물질개발, 리유즈, 리사이클링 등을 국제적 파트너와 함께 추진하여 리스크를 관리할 것이며, 2011년까지 최신정보를 구축하여 위기물질 전략을 재설정할 예정이다. 체계적인 위기물질 선정 및 관리전략 등을 참조하고, 신재생에너지기술 변화에 따른 원재료의 중요성 및 리스크 관리현황을 기초로 우리나라에 적합한 위기관리 물질 선정 및 관리가 필요할 것이다.