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Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*
Nihon Kinzoku Gakkai-Shi, 76(3), p.165 - 176, 2012/03
Times Cited Count：1 Percentile：78.66(Metallurgy & Metallurgical Engineering)Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
Proceedings of 21st International Workshop on Rare-Earth Permanent Magnets and their Applications (REPM 2010), p.161 - 164, 2010/08
We performed small-angle neutron scattering (SANS) measurements of Nd-Fe-B sintered magnets to get information on the averaged internal microstructure of Nd-Fe-B sintered magnets including the interfacial structure which is a key parameter to achieve a high-coercivity Dy-free Nd-Fe-B sintered magnet. SANS patterns from the Nd-Fe-B sintered magnets measured with a two-dimensional detector of a small-angle neutron scattering spectrometer SANS-J-II in the research reactor JRR-3 were sensitive to the sintering and annealing condition of the samples. These results indicate that the SANS measurement is a promising tool to investigate the correlation between the coercivity and the internal microstructure of Nd-Fe-B sintered magnets.
Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Sagawa, Masato*; Koyama, Keiichi*; Miyazaki, Terunobu*
no journal, ,
Sintered Nd-Fe-B magnets consist of Nd
Fe
B main phase with about 5
m diameter and Nd-rich grain boundary phase. It is well known that the coercivity of sintered Nd-Fe-B magnets is highly dominated by this Nd-rich phase, which is reported to change from discontinuous to continuous arrangement by a low temperature annealing around 500
600
C. We have shown that the coercivity of sintered Nd-Fe-B magnets can be further increased by applying a high magnetic field during the annealing. We found that such a coercivity enhancement phenomenon occurred only when a small amount of Cu is added, and when the annealing temperature is around 500C or 550C. In this paper, we report on the results of interface nanostructure analysis by DSC and Small Angle Neutron Scattering experiments to investigate the reason magnetic field effect occurs only in Cu-containing samples at specific annealing temperatures.
Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Sagawa, Masato*; Koyama, Keiichi*
no journal, ,
Sintered Nd-Fe-B magnets are the most promising materials for a driving motor of the hybrid electric vehicles(HV). In this application, a large value of coecivity 
is required because of the high operating temperature beyond 450 K. As a symptomatic treatment, Nd has been replaced partly by Dy to enhance . But the problem is an estimated short supply of Dy in the HV mass-production stage due to its low natural abundance. We have recently shown that of Nd-Fe-B magnets can be enhanced by applying a high magnetic field during the annealing. In order to elucidate the reason for the increase, we performed a small angle neutron scattering (SANS) study using SANS-J and PNO at JRR-3 of JAEA. We observed a marked deviation from the simple relation above for 
in the sample with Al and Cu additives. SANS results suggest that an existence of the Cu-containing liquid phases is strongly correlated with the enhancement by the high field annealing.
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Akiya, Takahiro*; Kato, Hiroaki*; Sagawa, Masato*
no journal, ,
no abstracts in English
Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Sagawa, Masato*; Koyama, Keiichi*
no journal, ,
no abstracts in English
B sintered magnetsTakeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Sagawa, Masato*; Koyama, Keiichi*
no journal, ,
Nd-Fe-B magnets are now widely used because of the highest BH
of them in the commercially available magnets. At the present, Dy, which is one of the rare metals, has to be added to maintain the coercivity especially in the operational temperatures higher than the room temperature. The key to achieve the Dy-free Nd-Fe-B magnets is how to control the grain size and the structure near the grain boundary. We have performed the small-angle neutron scattering (SANS) measurements of the sintered Nd-Fe-B magnets using unpolarized and polarized neutrons to obtain the averaged internal structures of samples with the different coercivity introduced by applying different high magnetic fields during the annealing. We found that inhomogeneity was induced by the magnetic fields applied parallel to 
. The relation between the inhomogeneity and the coercivity force is unclear at the moment, but we will present possible interpretation.
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
We have been investing the correlation between the coercive force and the averaged internal structure of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets using the small-angle neutron scattering (SANS) spectrometer, SANS-J-II installed at the beam hall of the research reactor JRR-3 in Tokai. The correlation is a clue to achieve the less or Dysprosium (Dy)-free Nd-Fe-B sintered magnets with high coercivity for high-temperature application. In this talk, we report that the coercivity is very sensitive to the averaged diameter of powder and the temperature in sintering process, and that the SANS patterns on 2-dimensional position-sensitive detector (2D-PSD) are also sensitively changed following the sintering condition.
Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Sagawa, Masato*
no journal, ,
The coercive force of Nd-Fe-B sintered magnets depends on several factors. Among those factors, the coercivity is easily affected by the temperature in the so-called low-temperature annealing process. A remarkable structural change of interface between the main phase (NdFe
B) and the Nd-rich phase is believed to occur at the temperature where the coercivity reaches the highest value. We performed the small-angle neutron scattering measurements to distinguish the SANS originating in nuclear structure from that in magnetic one. The external magnetic fields were applied parallel to the 
-axis, and were increased up to 10 kOe every 2 kOe during the measurements. Quantitative analysis of the change of scattering patterns and the magnetization process is reported at the meeting.
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
A Neodymium Iron Boron (Nd-Fe-B) sintered magnet is the most powerful permanent magnet among the commercially available ones. Because of the low 
, the coercivity of this magnet rapidly reduces above the room temperature. It is well known that substitution of dysprosium (Dy) for a part of Nd recovers the coercivity at the high temperatures. There are two key parameters to enhance the coercivity of Nd-Fe-B sintered magnets without the addition of Dy: grain refinement of microstructure in the magnets, and the microstructural control at the interface between NdFeB and Nd-rich phases surrounding the main phase. Small-angle neutron scattering (SANS) is very powerful tool to investigate such internal structures. We performed SANS measurements of the Nd-Fe-B sintered magnets using unpolarized and polarized neutrons on SANS-J-II installed at JRR-3. The information is essential to the achievement of the high-coercivity Dy-free Nd-Fe-B sintered magnet.
B magnets with different coercivity valuesAkiya, Takahiro*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Kato, Hiroaki*
no journal, ,
In spite of tremendous efforts, a role of intergranular Nd-rich phase in sintered Nd-Fe-B magnets on the coercivity () seems to be still unclear. The purpose of this work is to perform small-angle neutron scattering experiments on the sintered Nd-Fe-B magnets with different values and to investigate whether there exists any correlation between the average structure and the magnitude of . We found that the value of characterized intensity 
did not depend on the when 
is parallel to the -axis of the main NdFeB grain. On the other hand, for the 
configuration, we found that log linearly increases with increasing , for five different samples with ranging from 13 to 16 kOe owing to different annealing conditions.
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
A neodymium iron boron (Nd-Fe-B) sintered magnet is the most powerful permanent magnet among the commercially available ones. Dysprosium (Dy), however, has to be added in Nd-Fe-B sintered magnets to keep the high 
above the room temperature or high-temperature applications. Dy-less or Dy-free Nd-Fe-B sintered magnets are now highly demanded because Dy is one of the rare metals. We performed small-angle neutron scattering (SANS) measurements of sintered Nd-Fe-B sintered magnets to elucidate the correlation between the coercivity and averaged internal structures of this magnet. Such correlation is a clue to achieve the Dy-less or Dy-free Nd-Fe-B sintered magnets. In this talk, we report the detailed results of the experiments and the correlation revealed by the SANS measurements.
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*; Takeda, Masayasu
no journal, ,
no abstracts in English
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*
no journal, ,
no abstracts in English
