IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
Volume 124, Issue 10
Displaying 1-15 of 15 articles from this issue
Special Issue on Permanent Magnets and their Applications
Special Issue Review
  • Masaaki Tokunaga, Hirotoshi Fukunaga
    2004 Volume 124 Issue 10 Pages 847-850
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    Many kinds of permanent magnet materials have been developed and applied to industrial products for more than 80 years. Nd-Fe-B sintered magnets have been essential materials for applications in which miniaturization, energy conservation and anti-environmental pollution are required. R and D activities on permanent magnets and their applications should have been done in co-operation with each other for the expansion of permanent magnets. Recent trend of permanent magnets and their applications are reviewed from the viewpoint of high performance, new materials and applications.
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Special Issue Paper
  • Hiroshi Yamamoto, Takashi Nakanishi
    2004 Volume 124 Issue 10 Pages 851-856
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    The melt-spun ribbons of Pr-Fe-Co-V-W-Si-B system alloys were prepared by single roller rapid-quenching method. The effects of composition, surface velocity and heat-treatment on the magnetic properties were investigated. The Pr9Fe71Co8V0.5W0.5Si0.5B10.5 alloy ribbons prepared at a surface velocity of 12.5 m/s were crystallized by heat-treatment, and the optimum heat-treatment condition was found to be at 575 °C for 3 min, then the magnetic properties were (BH)max = 136.1 kJ/m3,, Jr = 0.93 T, HcJ = 652.2 kA/m, and HcB = 528.3 kA/m. The temperature coefficients of Jr and HcJ for the ribbons crystallized from melt-spun ribbons of Pr9Fe71Co8V0.5W0.5Si0.5B10.5 alloy were α(Jr)ave = -0.057 %/°C and α(HcJ) = -0.450 %/°C. The value of (BH)max for the compression molding Pr9Fe71Co8V0.5W0.5Si0.5B10.5 isotropic bonded magnet prepared by using the ribbons annealed at 575 °C for 3 min is 80.0 kJ/m3, and the density is 6.24 Mg/m3.
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  • Fumitoshi Yamashita, Shinichi Tsutsumi, Hidetsugu Toyoda, Hirotoshi Fu ...
    2004 Volume 124 Issue 10 Pages 857-862
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    Magnetic properties of radially-anisotropic ring-shaped magnets were deteriorated when their outer-diameter is decreased down. Therefore, anisotropic Nd2Fe14B bonded-magnets have not been mainly applied to small motors up to now. In order to overcome the above difficulty, we developed a new technique using self-organization of binder which enabled the alignment of molecular-chain. By using this technique, we controlled the flexibility of Nd2Fe14B /Sm2Fe17N3 rigid sheet-magnets (approximately 1 mm in thickness), transformed them into various shapes, and succeeded in preparing radially-anisotropic ring- or arc-shaped magnets. Optimizations of the solidification process of the binder under a transverse alignment-field and the transformation process into various specific shapes realized radially-anisotropic magnets with superior properties such as values of (BH)max and also magnetic stabilities. Their value of (BH)max exceeded 160 kJ/m3, even if their outer diameter is less than 25 mm.
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  • Kurima Kobayashi, Akiko Saito, Mika Nakamura
    2004 Volume 124 Issue 10 Pages 863-868
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    The observation using magnetic force microscopy (MFM) of the Sm2Fe17N3 (SFN) particles having 2-4μm in diameters (D), totally about 15 particles, revealed that the particles show single-domain state and/or more than 3 domain state. Magnetic and domain wall energies of the single-domain particle (SDP) and these of two and three domain particles (2DP, 3DP) were calculated using the measured saturated polarization (Js) and the domain wall energy (γ). The results of the calculation are as follows : (1) the energy difference between the 2DP and 3DP is less than 6% in the total energies, in the range of ESDP > E3DP> E2DP : (2) the 3DP becomes stable, E2DP > E3DP, in the particles of D>3.0μm assuming the critical diameter is 2μm. Local demagnetizing field and existence of macroscopic defects in a particle strongly influence on the nucleation of domain wall formation, and it is obvious that the 2DP has a higher static magnetic energy compared to that of the 3DP. Therefore, it can be considered that the morphological complexity of the real particles results in the increase of stability of the 3DP than that of the 2DP in the sample particles. On the other hand, the discrepancy between the calculated critical diameter of SDP (dc≈0.18μm) and the measured one (dc≈2μm) can be explained by the temperature dependence of relative ratio of crystal magnetic anisotropy and saturated polarization in the SFN particles, i. e. (K=K(T) / KR. T.) vs. (Js= Js(T) / JsR. T.). It is revealed that the decrease in the anisotropy is pronounced in the higher temperature region near the Curie temperature than that in the saturated polarization (K1Jsn (n>4)). It should be the origin of the measured large SDP size than that of theoretically calculated critical radius using K1, and Js at room temperature.
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  • Shinichi Kanazawa, Norio Takahashi, Takeharu Kubo
    2004 Volume 124 Issue 10 Pages 869-875
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    NdFeB sintered magnets are widely used in rotating machines. As the conductivity of NdFeB sintered magnet is fairly high compared with that of ferrite magnet, the eddy current loss due to slot ripple etc. cannot be neglected. If the eddy current loss of permanent magnet becomes large, the temperature of permanent magnet becomes high and the thermal demagnetization becomes serious. Therefore, it is required to evaluate ac loss of permanent magnet. But the measurement of ac loss of permanent magnet under serious operating condition is not reported yet. In this paper, the ac loss of NdFeB sintered magnet was measured using newly developed closed-type measuring equipment. It is shown that the coaxial double coil is useful for accurate measurement of magnetic field. The eddy current loss and hysteresis loss of permanent magnet are obtained by the loss separation. It is illustrated that the hysteresis loss is larger than the eddy current loss in the range of less than several hundred Hertz. The appropriateness of measurement is verified by the numerical analysis.
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  • Tetsuji Saito
    2004 Volume 124 Issue 10 Pages 876-880
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    The structures and magnetic properties of Co-Zr and Co-Zr-M (M=B, C, Si, Al) melt-spun ribbons and those annealed specimens were studied with a x-ray diffractometer and a vibrating sample magnetometer. The Co-Zr melt-spun ribbons consisted of Co5Zr and Co23Zr6 phases and showed a high coercivity. The small substitution of C for Zr in the Co-Zr alloy resulted in the increase in the saturation magnetization, but resulted in the decrease in both the remanence and coercivity. On the other hand, the small substitution of B for Zr in the Co-Zr alloy resulted in the increase in the remanence and coercivity. The small substitution of either Si or Al for Zr in the Co-Zr alloy resulted in the decrease in both the remanence and coercivity. Heat treatment of the melt-spun ribbons resulted in the further increase in the coercivity of Co-Zr-B alloys. However, annealing resulted in the decrease in the coercivity of the other Co-Zr-M (M=C, Si, Al) alloys.
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  • Takashi Ishikawa, Takashi Iseki, Koichi Yokosawa, Kunio Watanabe, Kenj ...
    2004 Volume 124 Issue 10 Pages 881-886
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    We have produced Sm2(Fe, Mn)17Nx coarse powders by a reduction and diffusion (R/D) method and investigated the characteristics. The Sm2(Fe, Mn)17 mother alloy powder made by the R/D method showed rounded shape and sharp particle size distribution, and was consisting of almost only Th2Zn17-type phase with minor α-Fe. For the nitrided Sm2(Fe, Mn)17N3 compound, the Mn addition increased the lattice constants of the Th2Zn17 structure and decreased both Curie temperature and magnetization of the compound. The nitrogen content of Sm2(Fe,Mn)17Nx coarse powder increased with increasing coercive force and decreasing magnetization. The nitrogenation of x>5 resulted in high corecive force more than 900 kA/m. The highest magnetic properties of Sm2(Fe0.95Mn0.05)17Nx coarse powder is Br=1.10 T, HcJ=720 kA/m and (BH)max=193 kJ/m3 at x=4.2. The Sm2(Fe0.95Mn0.05)17Nx magnet powder indicated good thermal stability. The deterioration of coercive force of Sm2(Fe0.95Mn0.05)17N4.5 powder after exposure at 160 °C for 160 h was as small as those of MQP-O and Sm2Co17 powders. The coercive force of an Sm2(Fe0.95Mn0.05)17Nx injection molded magnet with PPS was almost the same as the powder used. The time dependence of irreversible flux loss at 180 °C was similar to that of Sm2Co17 bonded magnets.
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  • Tomohito Maki, Satoshi Sugimoto, Toshio Kagotani, Koichiro Inomata, Ju ...
    2004 Volume 124 Issue 10 Pages 887-891
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    In this study, the relationship among magnetic properties, Aerosol Deposition (AD) conditions and microstructures in Sm-Fe-N AD films were investigated. The maximum thickness of 145 μm was obtained in the AD conditions of gas flow rate (gfr) = 6 L/min for 10 min. The density of Sm-Fe-N films were in the range of 5.43 - 6.24 g/cm3, which were 71 - 81 % of the X-ray density of the Sm2Fe17N3 compound reported (7.67 g/cm3). The Sm-Fe-N AD films showed remanence in the range of 0.38 - 0.42 T, which were 61 - 68 % of that of Sm-Fe-N host powder (0.62 T). The coercivities increased from 1.16 to 1.74 - 1.79 T after the deposition because the grain size decreased from 1.94 to 0.32 μm.
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  • Masaki Nakano, Ryutaro Kato, Hirotoshi Fukunaga, Fumitoshi Yamashita
    2004 Volume 124 Issue 10 Pages 892-896
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    We succeeded to deposite 200-300 μm thick Nd-Fe-B film magnets with (BH)max of approximately 55 kJ/m3 on Fe substrates by using PLD method. In addition, we confirmed that a milli-size motor, which was prepared from the obtained film, rotates at 15160 r/min under a no-load test.
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  • Masaki Nakano, Naoyuki Fujita, Masashi Takase, Hirotoshi Fukunaga
    2004 Volume 124 Issue 10 Pages 897-901
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    Co-Pt alloy film magnets were prepared by electrodeposition. After annealing as-deposited films with face-centerd-cubic (fcc) crystal stracture, the structure of films with 24-50 at.% Co content transformed from disordered fcc phase to ordered face-centered-tetragonal (fct) L10 phase. It was clarified that Co-Pt film magnets with the Co content of 43 at. % have high coercivity of approximately 880 kA/m.
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Paper
  • Seiichi Ishizaki, Shuichi Sato, Yasuhiro Tanaka, Tadashi Fukao, Tatsuo ...
    2004 Volume 124 Issue 10 Pages 902-908
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    The aim of this research work is to establish an accurate measurement technique using pulsed electro-acoustic method for observing a dynamic space charge behavior in insulating materials during elevating temperature under high electric stress. When the high electric stress is applied to the dielectric materials, so-called space charge accumulates in the bulk of dielectrics. It is said that space charge accumulation strongly affects the characteristics of electrical conduction and breakdown strength in dielectrics. Therefore it is necessary to observe the space charge formation in dielectric materials. It is well known that the space charge accumulation in the insulating materials strongly depends on temperature of materials. However, most of the space charge measurement has been carried out at room temperature except for a few reports. It seems that these have been still remained some difficulties for measuring the charge distribution during elevating temperature. Therefore, in this research work, we would like to establish the measurement technique for dynamic behavior of space charge accumulation in insulating materials at high temperature under high electric stress.
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  • Shunsuke Iwasaki, Yoshimoto Murata, Daisuke Ito, Yoshiyasu Ehara, Haru ...
    2004 Volume 124 Issue 10 Pages 909-914
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    In this research, since it aims to improve NOx removal rate, the system using discharge, photocatalyst(titanium oxide, TiO2) and UV Lamp as substitution for sunlight is discussed. NOx is also removed at TiO2 surface activated by irradiating UV rays of discharge luminescence and UV lamp in addition to NOx removal by electric discharge. As a result of experiment, NOx removal rate was improved. Moreover, TiO2 sheet was stuck on the inner wall of the outer glass tube, and a UV lamp was installed inside the inner glass tube. By using discharge, TiO2, and UV lamp, NO removal rate became higher than that of the other conditions. Since TiO2 was irradiated with UV rays of discharge luminescence and UV lamp, photocatalytic action was promoted. Therefore, it is considered that in addition to NOx removal by discharge, NOx was removed on TiO2 surface.
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  • Eiichirou Kawamori, Takashi Sumikawa, Takuro Igarashi, Yasushi Ono
    2004 Volume 124 Issue 10 Pages 915-920
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    Ion kinetic effect on the low-n toroidal modes in Compact Torus (CT) plasmas such as Spherical Tokamak (ST), spheromak, Field-Reversed-Configuration and compact Reversed-Field-Pinch (RFP), was investigated by using different ion species. The experimental result that indicates ion kinetic stabilization of the low-n modes was obtained in the low q95 regime. It was clearly shown that the n=1 mode was stabilized in the FRC under the low S* regime (S*: averaged number of ion skin depth). The suppression of the n=2 mode activity in the low S* RFP plasma was also observed. In the high q95 (- 4) ST regime, all low-n (1-4) toroidal modes were stable in the both cases of the high S* and low S*.
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  • Nicolae Georgescu
    2004 Volume 124 Issue 10 Pages 921-926
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    A depollution system for gas treatment, using the repetitive pulsed corona plasmas, has been carried out. For the reactor chamber, various geometries are being tested: (a) point-plate; (b) wire-plate; (c) wire-cylinder. To compare different geometries, the following parameters are measured or calculated: pulsed voltage; pulsed current; electrical charge per pulse; density of the corona electrons; energy dissipation by corona effect. Depending on the geometry, for 25 - 30 kV maximum voltages, the density of the corona electrons is of 1010 - 1011cm-3, and the energy dissipation by corona effect is of 1 - 100 mJ per pulse. Considerations concerning the geometry optimization are proposed.
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  • Li Mingjia, Kang Qiang, Chang Anbi, Cao Shaoyun, Zhang Yonghui
    2004 Volume 124 Issue 10 Pages 927-930
    Published: 2004
    Released on J-STAGE: January 01, 2005
    JOURNAL FREE ACCESS
    In order to develop a repetitive frequency accelerator, a repetitive pulse transformer with output voltage (U2m) of 300kV, average power of 40kW, and more than 500ns pulse duration has been designed and tested. The primary and secondary windings are double coils, which consist of four shunt segments. Its characteristics consists in improving the electric field of windings uniformity. Using an amorphous alloy core helps to improve pulse waveform of output voltage and increase energy transfer efficiency. The experimental results show that the transformer can satisfy designed requirement.
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