• Title/Summary/Keyword: Nd-Fe-B magnets

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A Study for Magnetic Orientation Enhancement in Nd-Fe-B Sintered Magnets (Nd-Fe-B계 소결자석의 이방화율 향상을 위한 연구)

  • 김동환;임광윤;김효준;조재완;서응석;김승호;김상면
    • Journal of the Korean Magnetics Society
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    • v.11 no.1
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    • pp.8-13
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    • 2001

  • Effects of casting Processes and lubricant addition were studied to improve remanence of 31RE-68TM-lB based sintered magnet by using axial pressing process. Strip casting was effective to get the fine and homogeneous microstructure without ${\alpha}$-Fe segregation. The strip cast flake resulted in narrower particle size distribution after jet milling with respect to the conventional cast ingot. During pressing step with a magnetic field, the particle alignment was increased by appropriate addition of liquid lubricant. In this study, it was revealed that narrow particle size distribution and appropriate addition of liquid lubricant were essential to improve the grain alignment and thus the remanence of Nd-Fe-B sintered magnet.

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A binder system for low carbon residue and debinding behaviors in injection molding of NdFeB powder (NbFeB 분말사출성형에소 저잔류탄소를 위한 결합제 및 탈지거동)

  • 최준환
    • Journal of Powder Materials
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    • v.6 no.2
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    • pp.132-138
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    • 1999

  • A new binder system and debinding process for low carbon residue in the injection molding of Nd(Fe, Co)B powder are investigated. In the injection molding of magnetic materials, it is demanded to reduce carbon residue which deteriorates their magnetic properties. The binder system developed is composed of polyethylene glycols (PEGs) and polypropylene (PP). PEG was selected as a major binder is component to be extracted in a molecular state by solvent extraction in ethanol, which step would leave no residue. PP was selected as a minor binder component to be subsequently removed by thermolysis which step would leave carbon residue. The behaviors of solvent extraction with the variations of PEG molecular weight, temperature, and time were examined. The dependency of residual carbon content on thermolysis atmosphere was also studied. Opened pore channels introduced in a green body by the solvent extraction and microstructures of the sintered magnets were observed using SEM.

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The effect of a static magnetic field of Nd-Fe-B magnet on alkaline phosphatase activity of MC3T3-E1 cells (Nd-Fe-B 자석의 정자기장이 MC3T3-E1 세포의 alkaline phosphatase 활성도에 미치는 영향)

  • Kim, Sook-Hee;Kwon, Oh-Won;Ryoo, Hyun-Mo
    • The korean journal of orthodontics
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    • v.30 no.2 s.79
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    • pp.205-214
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    • 2000

  • Recently, the magnetic force has been considered as a method for a more efficient tooth movement. The purpose of this study was to evaluate the effects of different static magnetic fields of Nd-Fe-B magnet on MC3T3-E1 cells by measuring the alkaline phosphatase activity and observing the amount of stained alkaline phosphatase. For measuring of alkaline phosphatase activity, MC3T3-E1 cells were seeded in first and third row of 12 well culture plates. And Nd-Fe-B magnets were positioned under the first column of first and third row to apply different static magnetic fields(first column:100mT ; second column:4.6mT ; third column:0.5mT ; forth column:0.0mT) to the cells for 7, 13, 19, and 25 days. For staining of alkaline phosphatase, MC3T3-E1 cells were seeded in 100mm culture plates. And Nd-Fe-B magnets were positioned under the corner of plates to apply different static magnetic fields(magnet side:100mT : the opposite side:0.5mT) to the cells for 7, 13, 19, and 25 days. The results were as follows : 1. ALP activity was increased until day 19 in biochemical determination as well as in histochemical staining, 2. The application of higher magnetic field(100mT) suppressed ALP activity at day 13, 19, 25. On the contrary, the application of the lower magnetic field(4.6mT, 0.5mT) significantly enhanced the ALP activity. 3. Consistent with enzyme assay, histochemical staining of ALP also demonstrated that higher magnetic field(100mT) suppressed ALP activity, lower one(0.5mT) enhanced.

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