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Hiroshi Yamamoto, Hiromichi Horie
1993 Volume 113 Issue 4 Pages
241
Published: April 20, 1993
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Motofumi Homma
1993 Volume 113 Issue 4 Pages
242-245
Published: April 20, 1993
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Yuji Kaneko, Koki Tokuhara, Naoyuki Ishigaki, Kazuhiko Majima
1993 Volume 113 Issue 4 Pages
246-250
Published: April 20, 1993
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Effects of the constituent phase of Nd-Fe-B magnets on sintering behavior are investigated. In the case of Nd-Fe-B magnets, a liquid phase forms by ternary eutectic reaction of Nd
2Fe
14B, Nd
1.1Fe
4B
4 and Nd-rich phase at 938K. When sintering temperature is raised above 1, 273K, a remarkable shrinking occures because of an increase in the amount of a liquid phase which is supplied by a reaction between Nd
2Fe
14B and Nd
1.1Fe
4B
4 phase. The residual flux density (
Br) of Nd-Fe-B magnets increases in proportion to the increase in the amount of the Nd
2Fe
14B phase. On the contrary, the intrinsic coercivity (
iHc) declined because of a decrease in the amount of the Nd
1.1 Fe
4B
4 and the Nd-rich phase. As a result, new high-performance Nd-Fe-B magnets having the maximum energy product of above 366kJ/m
3 (46 MGOe) has been developed by means of controlling the component ratios of these phases in Nd-Fe-B magnets.
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Nobuaki Takahashi, Satoshi Sugimoto, Masuo Okada, Motofumi Homma
1993 Volume 113 Issue 4 Pages
251-260
Published: April 20, 1993
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Present work describes the magnetic properties of Nd-Fe-B melt-spun ribbons which have lower Nd content than the Nd
2Fe
14B compound. The studied alloys were (1) Nd
xFe
94-xB
6, (2) (Fe
3B)
1-x-(Nd
2Fe
14B)
x and (3) Fe
1-x-(Nd
2Fe
14B)
x. The grain refinement were underwent by studying the conditions of annealing for crystallization. It results in disappearing noticeable knicks in the demagnetization curves, which is attributed to precipitations of α-Fe and Fe
3B phases. The Nd
8Fe
86B
6 melt-spun ribbon annealed at 650°C for 30 min exhibits the highest (
BH)
max of 126kJm
-3(15.8MGOe). The V addition is effective for improving the coercivity.
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Hiroshi Yamamoto, Eito Katagiri
1993 Volume 113 Issue 4 Pages
261-267
Published: April 20, 1993
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Melt-spun ribbons of Nd-Fe-Co-B-Cu-Nb system alloys were prepared by the single roller rapid-quenching method. The effects of composition, wheel velocity and heat-treatment on the magnetic properties were investigated. The magnetic properties of bonded magnets prepared by compression molding of optimally annealed ribbons were also measured. A maximum energy product of 152.1kJ/m
3 was obtained for the Nd
11Fe
72Co
8B
7.5Cu
0.5Nb
1.0 alloy ribbon prepared at a wheel velocity of 17.1m/s. From TEM observation in the Nd
11Fe
72Co
8B
7.5Cu
0.5Nb
1.0 ribbon, the particle size of these ribbons was determined to be between 10 and 40nm. It is conjectured that the high remanence is observed by the magnetic interaction of these fine particles. It was found that these fine particles were achieved by Nd-Fe-Co-B compound in addition with Nb and Cu, at the same time. The amorphous Nd
11Fe
72Co
8B
7.5Cu
0.5Nb
1.0 ribbons prepared at a wheel velocity of 20.7m/s were crystallized by heat treatment, and the optimum annealing condition was found to be at 650°C for 15min. Its corresponding value of (
BH)max is 144.5kJ/m
3. A maximum energy product of 88.1kJ/m
3 was achieved with Nd
11Fe
72Co
8B
7.5Cu
0.5Nb
1.0 bonded magnets made from the optimally prepared ribbons.
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Testuo Kato, Masami Suzuki, Takashi Furuya
1993 Volume 113 Issue 4 Pages
268-275
Published: April 20, 1993
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Mecaeical grinding and subsequent heat treatment on the Nd
15Fe
77B
8 alloy powder made by means of centrifugal atomization causes high coercive force equal to the known value by former methods. The transition of magnetic properties during these process was studied by apparent specific heat and X-ray analysis. Mechanical grinding for 6 hours keeps the state of preceeding process to amorphous. Change to amorphous state is improved by mechanical grinding for 12-24 hours. The crystallization makes progress by subsequent heat treatment at 450-500°C. It was concluded that the high coercive force was obtained during the crystallization. After heat treatment at 600°C, advance of crystallization causes the lower coercive force.
Similar change of magnetic properties was also observed for the Nd
13Dy
2Fe
77B
8 alloy power.
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Nobuyoshi Imaoka, Toshio Suzuki
1993 Volume 113 Issue 4 Pages
276-285
Published: April 20, 1993
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Magnetic properties and nitrogenation mechanism of Sm
2Fe
17N
x(0 _??_ x _??_ 6) are discussed in this review.
The Sm
2Fe
17N
x specimens with 0 _??_ x _??_ 6 can be prepared by nitrogenating Sm
2Fe
17 in a mixed-gas atmosphere of NH
3 and H
2. Both saturation magnetization and anisotropy field reach the maximum values at x=3.0 (4
πIs=15.7kG=1.57T,
Ha=260kOe=21MA/m). We have already attained to fabricate high performance powder compressed magnet with (
BH)
max of 21 MGOe (170kJ/m
3).
A linear relation between a thickness of nitrogenated layer and time of nitrogenation can be seen in a reaction using a mixed gas of NH
3 and H
2. This fact suggests that the rate of the nitrogenating reaction using a mixed-gas of NH
3 and H
2 is dominated by interface-reaction process.
The difference of nitrogenating mechanism between (NH
3-H
2)-nitrogenation and N
2-nitrogenation is also discussed.
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Akira Fukuno, Chikara Ishizaka, Tetsuhito Yoneyama
1993 Volume 113 Issue 4 Pages
286-291
Published: April 20, 1993
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The hard magnetic properties of newly developedi intermetalic compound Sm
2Fe
17N
x are enough high to become permanent magnet materials with their high saturation magnetization, a large uniaxial anisotropy and high Curie temperature.
High magnetic properties of (
BH)
max=240kJ/m
3, Br=1.27T and
Hcj=916kA/m were obtained as fine powder shape, which is preferable shape for raw materials of resin or metal bonded magnets. These magnetic properties promised (
BH)
max=160kJ/m
3 as bonded magnets applying standard technique for a fabrication of anisotropic bonded magnets.
Compositions, phase analysis and nitrogenation condition have been investigated. Single phase is necessary for high magnetic properties. Three main factors in process are as follows: composition of close to Sm
2Fe
17N
x stoichiomerty, hydrogen treatment before nitrogenation, lower temperature and longer time condition for nitrogenation
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Akio Hasebe, Tetsutaro Imai, Etuo Otsuki
1993 Volume 113 Issue 4 Pages
292-298
Published: April 20, 1993
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The magnetic properties of La
2Co
17-x-yFe
xTi
y and La
2Co
17-x-yFe
xTi
yN
δintermetallic compounds have been investigated. La
2Co
17-x-yFe
xTi
y has the rhombohedral Th
2Zn
17 structure and exhibits magnetic properties as follows: saturation magnetization >1.0T, Curie temperature >873K and easy c-axis.
Nitrogen is introduced into these compounds interstitially through nitrogenation process. The saturation magnetization and Curie temperature of La
2Co
17-x-yFe
xTi
yN
δis decreased by introduction of nitrogen, on the contrary to Sm
2Fe
17.
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1:12: N-type Compounds and Fe3B-Nd
Satoshi Hirosawa, Ken Makita, Yoshikazu Kanekiyo, Minoru Umemoto
1993 Volume 113 Issue 4 Pages
299-305
Published: April 20, 1993
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Hard magnetic properties of nitrogen interstitially-modified NdM
xFe
12-
xN
y compounds and Fe
3 B-based ultra-fine crystalline Nd-Fe-Co-T-B alloys of low Nd content of 3-5 at. % are studied. The nitrogen-modified compounds have been prepared via the rapid solidification route and the mechanical alloying route both followed by gas nitrogenation using N
2. The Fe
3B-based materials have been prepared by means of rapid solidification and crystallization heat treatment. The latter materials appear promising as the base material for high-remanence, easy-to-magnetize bonded magnets with small temperature coefficients of the remanence. A typical magnetic properties of compaction isotropic bonded magnets produced from this material are
Br=0.80T,
HcJ=350kA/m and
(BH)max=60.5kJ/m
3.
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Hiroshi Yamamoto, Akinori Ishii
1993 Volume 113 Issue 4 Pages
306-312
Published: April 20, 1993
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An experiment was carried out to investigate the effect of CaO and SiO
2 addition on the magnetic and physical properties of anisotropic Ba-Zn W-type hexagonal ferrite magnets. It was found that magnetic properties of BaO•2ZnO•8Fe
2O
3 compounds added with CaO and SiO
2 were improved. The optimum conditions of typical specimens are as follows: chemical analysis composition-Ba
0.857 Zn
1.643 Ca
0.150 Si
0.266 Fe
2+0.030 Fe
3+15.857 O
27; semisintering condition-1, 275°C×1.0h in air; sintering condition-1, 250°C×0.5h in air; magnetic and physical properties are
Jm=0.436T,
Jr=0.393T,
HcJ=64.4kA/m,
HcB=64.1kA/m, (
BH)
max=16.1kJ/m
3,
Tc=357°C,
HA=971kA/m,
KA=2.03×10
5J/m
3 and
nB=33.2μB.
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Kazuto Sakai, Takashi Oishi, Tadashi Tokumasu
1993 Volume 113 Issue 4 Pages
313-320
Published: April 20, 1993
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Conventional magnet couplings which have been applied to productive machines of medicine and food-stuff are small power (10N•m-1, 200rpm). Recently, the magnet couplings of large power (high speed and large torque) are required for a fluid pump for oil and an apparatus of laser. Rareearth permanent magnets (Sm-Co, Nd-Fe-B) with high energy products allow us to develop the large permanent magnet coupling.
The small magnet coupling was developed by the way of trial and error or the macroscopic torque analysis. But it is difficult to design the large magnet coupling without the analysis of high accuracy. A finite element method makes it possible to analyze magnetic field with accuracy.
This paper presents the torque analysis of the large parmanent magnet coupling. The analysis is composed of two dimensional magnetostatic finite element method and the calculation, which compensates the decrease of torque by leakage flux at axial ends. We analyzed the large permanent magnet coupling with the rated power of 100N•m-8, 000rpm. Then, we measured the torque of the magnet coupling which was made of Sm-Co permanent magnet.
The analysis shows good agreements with test results within the error of few percent.
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Tadashi Amakawa, Kazuo Adachi, Masatoyo Shibuya, Tsuginori Inaba
1993 Volume 113 Issue 4 Pages
321-329
Published: April 20, 1993
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Compared with the conventional combustion, thermal plasma technology offers particular advantages for industrial heating and opens new applications. In order to support these applications theoretically, fundamental propeties of plasma are needed. So electrical and thermal conductivities of different compositions of the argon-iron mixture gases used in plasma torches have been calculated. The method we used was derived from Chapmann-Enskog's. Calculations were made for temperature between 2, 500-30, 000K and for pressure between 1-20atm assuming the hypothesis of local thermodynamic equilibrium. In the case of the pure argon, our results show good agreement with other experimental and calculated values. The effects of iron vapor and pressure on transport properties were clarified. Main results are as follows:
(1) Admixture of iron vapor causes the transport properties to increase in lower temperatures and to decrease in higher temperatures; this results from the lower ionization potentials of iron atoms and ions compared with those of argon atoms and ions.
(2) Increase of pressure causes the transport properties to decrease in lower temperatures and to increase in higher temperatures; this results from the upward shift of the temperature region in which the ionization reactions proceed efficiently.
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Naoki Hamamura, Motoshige Yumoto, Takao Sakai
1993 Volume 113 Issue 4 Pages
330-336
Published: April 20, 1993
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PTFE (Poly-tetra-fluoro-ethylene) is one of the most chemically stable polymers. This means the small surface energy and the poor adhesion property. However, the small surface energy means the difficulty on the surface treatment to give the chemical and/or physical functions to the surface. Many studies concerned with the surface processing of polymers by means of gaseous discharge have been carried out.
The authors have studied on the electron multiplication mechanism under high
E/n conditions. Consequently, it was predicted that many ions with high kinetic energy exist in the ionizing space. Their energies are some 10 or 100 times higher than binding energy of PTFE. Then, surface processing of PTFE by use of high
E/n discharge is expected to introduce new functions onto the PTFE surface. In this study, the adhesive strength of the processed PTFE was measured and was compared with the change of the surface energy, C
1s spectra by XPS, morphology observed by SEM and weight of sample. As a result, the surface energy increased with respect to the processing time, and the adhesive strength showed a maximum and decreased for long processing time. The weight of sample decreased with processing time. Therefore, it is concluded that the optimum condition for the improvement of the property exists.
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Masanori Hara, Kenji Saita, Hirokatsu Saito
1993 Volume 113 Issue 4 Pages
337-344
Published: April 20, 1993
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The behavior of bubbles in cryogenic liquids under non-uniform fields is studied analytically. A plane-to-cylinder with/without fins is given as an electrode system for producing non-uniform fields. The results show that the bubbles near the tip of high stress electrode like a triangular fin are blown away by the gradient force before breakdown and the force acting on the bubble produces more than an acceleration of 1, 000G, but those trapped in the groove between fins are pressed by the Maxwell stress in the direction of the groove bottom. This suggests that the heat transfer is promoted near the fin top while at the bottom of the groove the nucleate boiling turns to the local film boiling by the voltage application and the heat transfer is reduced there. In a plane-to-cylinder without fins, a spatial region balancing the gradient and gravitational forces appears even if the applied voltage is much lower than the breakdown one and a vapor column bridging between electrodes is believed to be formed in that region. However the vapor column may not seriously affect the breakdown voltage because its formation occurs away from the shortest gap.
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Hideomi Matsuzaki
1993 Volume 113 Issue 4 Pages
345-346
Published: April 20, 1993
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Akihiko Takahashi, Kiyoto Nishijima
1993 Volume 113 Issue 4 Pages
347-348
Published: April 20, 1993
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Hisashi Otsuka, Sumio Kogoshi, Makoto Matsushita
1993 Volume 113 Issue 4 Pages
349-350
Published: April 20, 1993
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