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Journal Articles

Small-angle neutron scattering measurements of the averaged internal structures in neodymium-iron-boron (Nd-Fe-B) sintered magnets

Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*

Nihon Kinzoku Gakkai-Shi, 76(3), p.165 - 176, 2012/03

 Times Cited Count:1 Percentile:79.87(Metallurgy & Metallurgical Engineering)

Journal Articles

Correlation between the averaged internal structure and the coercive force of neodymium-iron-boron (Nd-Fe-B) sintered magnets investigated by small-angle neutron scattering

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.

Oral presentation

Interface nanostructure of Cu-added Nd-Fe-B sintered magnets processed by high magnetic fields

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$$_{2}$$Fe$$_{14}$$B main phase with about 5$$mu$$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$$sim$$600$$^{circ}$$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 500$$^{circ}$$C or 550$$^{circ}$$C. 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.

Oral presentation

Small angle neutron scattering study of interface nanostructure in sintered Nd-Fe-B magnets processed under high magnetic fields

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 $$H_{c}$$ is required because of the high operating temperature beyond 450 K. As a symptomatic treatment, Nd has been replaced partly by Dy to enhance $$H_{c}$$. 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 $$H_{c}$$ 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 $$H_{c}$$ 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 $$q > 0.3 nm^{-1}$$ 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 $$H_{c}$$ enhancement by the high field annealing.

Oral presentation

Evaluation of averaged structures of sintered Nd-Fe-B magnets by small angle neutron scattering

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Akiya, Takahiro*; Kato, Hiroaki*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Characterization of average interface structure in sintered Nd-Fe-B magnets by small angle neutron scattering

Akiya, Takahiro*; Kato, Hiroaki*; Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Koizumi, Satoshi; Sagawa, Masato*; Koyama, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

Polarized small-angle neutron scattering measurements of averaged internal structure in Nd-Fe-$$^{11}$$B sintered magnets

Takeda, 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$$_{rm max}$$ 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-$$^{11}$$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 $$vec{M}$$. The relation between the inhomogeneity and the coercivity force is unclear at the moment, but we will present possible interpretation.

Oral presentation

Correlation between the coercivity and the averaged internal structures of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets studied by small-angle neutron scattering measurements, 2

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.

Oral presentation

Magnetization process of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets investigated by small-angle neutron scattering under external magnetic fields

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 (Nd$$_{2}$$Fe$${}_{14}$$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 $$c$$-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.

Oral presentation

Small-angle neutron scattering measurements of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets

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 $$T_{c}$$, 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 Nd$$_{2}$$Fe$$_{14}$$B 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.

Oral presentation

Small-angle neutron scattering study of sintered Nd-Fe-$$^{11}$$B magnets with different coercivity values

Akiya, 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 ($$H_{c}$$) seems to be still unclear. The purpose of this work is to perform small-angle neutron scattering experiments on the sintered Nd-Fe-$$^{11}$$B magnets with different $$H_{c}$$ values and to investigate whether there exists any correlation between the average structure and the magnitude of $$H_{c}$$. We found that the value of characterized intensity $$I(0)$$ did not depend on the $$H_{c}$$ when $$vec{q}$$ is parallel to the $$c$$-axis of the main Nd$$_{2}$$Fe$$_{14}$$B grain. On the other hand, for the $$vec{q} perp c{rm -axis}$$ configuration, we found that log $$I(0)$$ linearly increases with increasing $$H_{c}$$, for five different samples with $$H_{c}$$ ranging from 13 to 16 kOe owing to different annealing conditions.

Oral presentation

Study of the correlation between the coercivity and averaged internal structure of Nd-Fe-B sintered magnets

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 $$H_{rm c}$$ 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.

Oral presentation

Small-angle neutron scattering measurements of Nd-Fe-B sintered magnets

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Simulation of the small-angle neutron scattering pattern of Nd-Fe-B sintered magnet

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Simulation of small-angle neutron scattering pattern of Nd-Fe-B sintered magnets, 2

Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*; Takeda, Masayasu

no journal, , 

no abstracts in English

Oral presentation

Small-angle neutron scattering measurements of Nd-Fe-B sintered magnets, 2

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Study of averaged internal structures of Nd-Fe-B sintered magnets studied by small-angle neutron scattering

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Small-angle neutron scattering patterns and real-space image of Nd-Fe-B sintered magnets

Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

Oral presentation

Average internal structures of Nd-Fe-B sintered magnets studied by small-angle neutron scattering

Takeda, Masayasu; Suzuki, Junichi*; Akiya, Takahiro*; Kato, Hiroaki*; Une, Yasuhiro*; Sagawa, Masato*

no journal, , 

no abstracts in English

19 (Records 1-19 displayed on this page)
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