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Volume 55, Issue 7
July
Displaying 1-10 of 10 articles from this issue
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Paper
Paper
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Masashi Yoshinaga, Ken Hirota, Masaki Kato, Hideki Taguchi, Hiroyasu K ...2008 Volume 55 Issue 7 Pages 497-501
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSRuddlesden-Popper type compounds, being presented as (ABO3)n-AO or An+1BnO3n+1 (n=1, 2, 3…∞), have a layer structure where perovskite layer ABO3 and rock salt type layer AO are alternately in place; Can+1(Mn1-xVx)nO3n+1 (0≤x≤1) belongs also to this compound. As CaO layer shows low thermal conductivity whereas CaMnO3 layer reveals high electrical conductivity and high Seebeck coefficient, therefore, Can+1(Mn1-xVx)nO3n+1 seems to become a promising module as a thermoelectric conversion material. However, there was no report concerning about the thermoelectric conversion characteristic of this compound. In this study we have investigated electrical conductivity, Seebeck coefficient, and thermal conductivity of Can+1(Mn1-xVx)nO3n+1 and discussed about the possibility of the application as thermoelectric conversion elements from dimensionless performance index ZT.View full abstractDownload PDF (954K)
Review
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Hiroshi Kimura2008 Volume 55 Issue 7 Pages 502-508
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSThis article overviews the mechanical characterization of nanocrystalline ceramics synthesized by consolidating MA amorphous powder without additive. Berkovich indentation with depth-sensing enables to obtain a yield stress (σy) under constrained compression and the strain rate sensitivity exponent (m) as an accepted parameter of micro-plasticity; for nanocrystalline (ZrO2)80(Al2O3)20, the σy is a low level of 4.4 GPa when non-strain hardening is assumed, and the m has a considerably low value of 0.014 suggesting the appearance of non-homogeneous flow in a nearly ideal plastic solid. For monolithic tetragonal (ZrO2-3mol%Y2O3)80 (Al2O3)20 with the longitudinal crystallite size of 40 nm, the flexural strength shows a size effect with the aspect ratio of sample width (W) to height (H) having nearly 2 GPa at the maximum in the case of W/H≈1, and a proportionality to the fracture toughness as obtained from the indentation-microfracture method, being apart from a trade off relationship. Then, the isothermal superplastic forming up to a compressibility of 0.75 is used to derive the constitutive equation; m is given as a function of strain rate reduced by Zener-Hollomon parameter (ZH) and reciprocal stress, εσ−1exp(Q/kT) with the activation energy (Q) of 312 kJ·mol−1, having the constancy of 0.7 and a decreasing value to 0.3 at its higher and lower ZH respectively.View full abstractDownload PDF (1043K)
Paper
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Satoshi Kawamura, Tomoaki Abe, Hisashi Kuwano2008 Volume 55 Issue 7 Pages 509-514
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSA consolidation process of the nanocrystalline iron powder has been investigated to produce a high strength bulk plate of superfine grained (SFG) pure iron. The nanocrystalline iron powder was prepared by mechanical milling (MM) of a high purity carbonyl iron powder in argon or hydrogen atmosphere. The consolidation was done at a pressure of 300 MPa using a spark plasma sintering (SPS) machine. The SFG iron which was sintered at 570°C for 600 s using the powder milled in hydrogen has a relative density of 98.5 %, a grain size of 102 nm and a fracture strength of 1370 MPa. The fracture strength is strongly sensitive to the relative density and the oxygen content.View full abstractDownload PDF (1305K)
Special Issue: Permanent Magnet Materials and Their Applications
Summarization
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Hiroshi Yamamoto2008 Volume 55 Issue 7 Pages 516
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSDownload PDF (109K)
Memorial Lecture of JSPM Award
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Chikara Okada, Yuuichi Miyake, Kazuhiko Yamamoto, Takayuki Shibamoto2008 Volume 55 Issue 7 Pages 517-521
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSNd-Fe-B magnetic materials yield many different compounds in solidification process. For this reason, conventional mold-casting method used for Sm-Co magnetic materials was not suitable for quality and productivity. To solve their problem, rapid solidification was required. To rapidly solidify the alloy melt, thin mold gap in conventional mold-casting method was tried, but it was not suitable for productivity. New production method was developed; it was mold-free and able to rapidly and uniformly solidify the alloy melt. It was devised as the method between continuous casting and single roll casting based on melt-spinning. Several conditions were tried and followed effects were acquired. Milling and sintering were improved due to microscopic and uniform constitutions. We call the method as "Strip-casting method".
In this paper, constitution characteristics of alloys produced by Strip-casting and conventional mold-casting method, and the influence for production of magnet using those alloys are summarized. Transition of production and development for other products are also reported.View full abstractDownload PDF (1064K)
Paper
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Hiroshi Yamamoto, Kenta Osanai2008 Volume 55 Issue 7 Pages 522-528
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSThis experiment was carried out to investigate the effect of Y addition on magnetic properties of Sm-Fe-Co-Mn-Ti system nitride with TbCu7-type structure. Sm10(Fe0.9Co0.1)89−xMn0.5Ti0.5Yx (x=0∼2.0) alloy ribbons were prepared by the single roller rapid-quenching method. And the effect of alloy composition, and conditions of heat-treatment and nitrogenation on the magnetic properties were examined. The typical preparation conditions of the compound with high coercivity are as follows. Composition: {Sm10(Fe0.9Co0.1)87.7Mn0.5Ti0.5Y1.3}85.3N14.7, roller velocity: 50 m/s, heat treatment condition: 660°C×60 min in high-purity Ar gas, and nitrogenation condition: 420°C×15 h in high-purity N2 gas. Typical magnetic properties of the obtained powder are Jr=0.77 T, HcJ=1649.6 kA/m, (BH)max=104.1 kJ/m3, and TC=532°C. The average crystal particle size of heat treated ribbon was 13 nm. The value of (BH)max for the isotropic compression molding bonded magnet prepared from the {Sm10(Fe0.9Co0.1)87.7Mn0.5Ti0.5Y1.3}85.3N14.7 powder is 57.50 kJ/m3, when the density of bonded magnet is 6.00 Mg/m3. And the relative temperature coefficient of Jr is α(Jr)=−0.044 %/°C, the temperature coefficient of HcJ in the range from 25°C to 125°C obtained by a linear interpolation is α(HcJ)=−0.488 %/°C. And we examined the temperature dependence of the flux loss rate on Sm-Fe-Co-Mn-Ti-Y-N and MQP-A bonded magnet. When the temperature is 150°C, the flux loss rate of MQP-A bonded magnet is −3.09%, that of Sm-Fe-Co-Mn-Ti-Y-N bonded magnet is −2.36%.View full abstractDownload PDF (879K) -
Hiroshi Yamamoto, Tomonori Sato2008 Volume 55 Issue 7 Pages 529-534
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSThe melt-spun ribbons of Didymium-Fe-Co-Nb-V-Y-Hf-B system alloys were prepared by single roller liquid rapid-quenching method, and the effects of composition, wheel velocity and heat treatment on the magnetic properties were investigated. As the result, Didymium11.0Fe69.6Co10Nb1V1Y0.7Hf0.7B6 optimum composition ribbons prepared at a wheel velocity of 22.5 m/s were crystallized by heat treatment, and the optimum heat treatment condition was found to be at 725°C for 5 min, and then the values of (BH)max and HcJ were 105.7 kJ/m3, 1307.4 kA/m, respectively. The temperature coefficients of Jr and HcJ for the ribbons crystallized from the melt-spun Didymium11.0Fe69.6Co10Nb1V1Y0.7Hf0.7B6 alloy were α(Jr)ave.=−0.10 %/°C (reversible) and α(HcJ)=−0.48 %/°C (irreversible), respectively. The value of (BH)max for the isotropic compression molding Didymium11.0Fe69.6Co10Nb1V1Y0.7Hf0.7B6 bonded magnet prepared by using the ribbons annealed at 725°C for 5 min is 56.6 kJ/m3 and the density is 6.14 Mg/m3. Irreversible loss of the isotropic bonded magnet are −1.21% (at 150°C) and −2.42% (at 200°C).View full abstractDownload PDF (888K) -
Hiroshi Yamamoto, Akinori Tadokoro2008 Volume 55 Issue 7 Pages 535-540
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSThis experiment was carried out to investigate the magnetic properties of Sr-Zn-Ni system W-type hexagonal ferrite powders, and bonded magnets were prepared from these powders. It was found that Sr-Zn-Ni system W-type hexagonal ferrite can be easily produced in the air. The preparation conditions for a typical sample were as follows; chemical composition: SrO·0.5ZnO·1.0NiO·0.5FeO·8Fe2O3 with added 0.3 wt% SiO2, 0.7 wt% CaO, 1.0 wt% SrCO3; reaction sintering condition: 1300°C×4.0 h in air; annealing condition: 1025°C×5 min in air. The magnetic properties of Sr-Zn-Ni system W-type hexagonal ferrite powder are σs=88.63×10−6 Wb·m/kg, HcJ=217.8 kA/m. The magnetic properties of hybrid (mixed 80% M-type ferrite powder and 20% W-type ferrite powder) bonded magnets are Br=284 mT, (BH)max=15.3 kJ/m3, HcJ=183 kA/m.View full abstractDownload PDF (762K) -
Yoshinori Kobayashi, Seiichi Hosokawa, Etsushi Oda, Sachio Toyota2008 Volume 55 Issue 7 Pages 541-546
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSA synthesis and magnetic properties of Ca-La-Co M-type (Ca1-xLaxCoyFen-yOa) ferrite magnets were investigated. A M-type singlephase calcined powder was synthesized with a composition of x=0.5, y=0.2-0.3 and n=10.0-10.8. And a very high magnetic properties of Jr=0.453 T (4530 G) and HcJ=435 kA/m (5470 Oe) were obtained with a composition of x=0.5, y=0.3 and n=10.4 in sintered magnets. The magnetic properties greatly exceeds that of Sr-La-Co M-type ferrite, which has been the highest grade M-type hard ferrite. The improvement can be attributed to the 20% increase in anisotropic magnetic field in comparison to that of Sr-La-Co M-type ferrite. The temperature dependence of coercivity was also improved to ΔHcJ/HcJ/ΔT=0.11 %/K, compared to 0.16 %/K in Sr-La-Co ferrites.View full abstractDownload PDF (1622K)
Errata (Vol.55, No.5)
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Takayuki Narushima, Kyosuke Ueda, Takashi Goto, Tomoyuki Katsube, Hiro ...2008 Volume 55 Issue 7 Pages 551
Published: 2008
Released on J-STAGE: November 26, 2008
JOURNAL OPEN ACCESSAbout the paper by Takayuki Narushima et al. published in the May 2008 issue of the Journal, the authors requested that some errors in the Table 1 (p322) of the original paper should be corrected.View full abstractDownload PDF (25K)
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