• Journal of Powder Materials
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• v.20 no.3
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• pp.169-173
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• 2013

High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd-Fe-B powder yielded samples with densities greater than 98%. $(Nd,Dy)_2Fe_{14}B$ phases may have effectively penetrated into the boundaries between neighboring $Nd_2Fe_{14}B$ grains during the sputtering coating process, thereby forming a $(Nd,Dy)_2Fe_{14}B$ phase at the grain boundary. The maximum thickness of the Dy shell was approximately 70 nm. The maximum coercivity of the Dy sputter coated samples(sintered samples) increased from 1162.42 to 2020.70 kA/m. The microstructures of the $(Nd,Dy)_2Fe_{14}B$ phases were effectively controlled, resulting in improved magnetic properties. The increase in coercivity of the Nd-Fe-B sintered magnet is discussed from a microstructural point of view.

• Journal of Powder Materials
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• v.23 no.6
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• pp.437-441
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• 2016

Recently, the grain boundary diffusion process (GBDP), involving heavy rare-earth elements such as Dy and Tb, has been widely used to enhance the coercivity of Nd-Fe-B permanent magnets. For example, a Dy compound is coated onto the surface of Nd-Fe-B sintered magnets, and then the magnets are heat treated. Subsequently, Dy diffuses into the grain boundaries of Nd-Fe-B magnets, forming Dy-Fe-B or Nd-Dy-Fe-B. The dip-coating process is also used widely instead of the GBDP. However, it is quite hard to control the thickness uniformity using dip coating. In this study, first, a $DyF_3$ paste is fabricated using $DyF_3$ powder. Subsequently, the fabricated $DyF_3$ paste is homogeneously coated onto the surface of a Nd-Fe-B sintered magnet. The magnet is then subjected to GBDP to enhance its coercivity. The weight ratio of binder and $DyF_3$ powder is controlled, and we find that the coercivity enhances with decreasing binder content. In addition, the maximum coercivity is obtained with the paste containing 70 wt% of $DyF_3$ powder.

• Advances in materials Research
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• v.4 no.4
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• pp.227-233
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• 2015

We present a method, supported by theoretical analysis, for optimizing the usage of the critical rare earth element dysprosium in $Nd_2Fe_{14}B$ (NdFeB)-based permanent magnets. In this method, we use Dy selectively in locations such as magnet edges and faces, where demagnetization factors are largest, rather than uniformly throughout the bulk sample. A200 nm thick Dy film was sputtered onto a commercial N-38, NdFeB magnets with a thickness of 3 mm and post-annealed at temperatures from $600-700^{\circ}C$. Magnets displayed enhanced coercivities after post-annealing and as much as a 5 % increase in the energy product, while requiring a total Dy content of 0.06 wt. % - a small fraction of that used in the commercial grade Dy-NdFeB magnets. By assuming all Dy diffused into NdFeB magnets, the improvement in energy product corresponds to a saving of over 1% Dy (critical element). Magnets manufactured using this technique will therefore be higher performing which would potentially broaden the application space of these magnets in the traction motors of hybrid and pure electric vehicles, and wind generators.

• Proceedings of the Korean Magnestics Society Conference
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• 2013.05a
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• pp.79-80
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• 2013

• Journal of radiological science and technology
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• v.14 no.1
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• pp.49-60
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• 1991

Thermoluminescent phosphors, which are now being used widely in radiation dosimetry, have an excellent sensitivity to ionizing radiation. In this study, thermoluminescent phosphors of $CaSO_4$ : Mn, $CaSO_4$ : Dy and $CaSO_4$ : Tm are prepared and their physical properties are investigated by measuring the trapping parameters and their luminescent spectra. By considering the sensitivity to X-ray and fading characteristics, $CaSO_4$ : Dy is most adequate to imaging plate. The imaging plate are prepared by coating the $CaSO_4$ : Dy powder on the Al substrate and its dose dependence is linear within the range of 40 mGy-20 Gy X-ray. The sensitivity of imaging plate depends linearly on the thickness of coated phosphor layer up to $35\;mg/cm^2$ and is independent on the grain size of the phosphor in the range of $70{\sim}250\;{\mu}m$. By photographing the imaging plate, X-ray images of the test object are obtained and better than those of X-ray films.