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Volume 50, Issue 8
Displaying 1-11 of 11 articles from this issue
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Yoshihiro Tada, Masaki Imai2003 Volume 50 Issue 8 Pages 595-599
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffect of contamination of tobacco to cutting fluid on surface roughness has been investigated in finish turning of P/M aluminum alloy and wrought pure aluminum. Tobacco deteriorates the surface finish, so that the experiential knowledge in machining work shops is confirmed. The harmfulness of tobacco appears clearer at good finishing conditions. The deterioration in surface roughness depends on concentration of some tobacco component (s) exuded into cutting fluid; surface roughness is not influenced below a threshold concentration and the deterioration in surface roughness shows saturation at high concentrations. The adverse effect of contamination of tobacco to cutting fluid on surface roughness can be recovered by removing the harmful tobacco component (s) from the fluid by active carbon.View full abstractDownload PDF (434K) -
[in Japanese]2003 Volume 50 Issue 8 Pages 602
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (70K) -
Naoyoshi Sato, Hitoshi Saita, Tomofumi Kuroda2003 Volume 50 Issue 8 Pages 603-608
Published: August 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSWe studied the grain boundary chemistry in low loss MnZn ferrites. Some impurities and the sintering conditions, namely temperature and atmosphere, are effective to change the structures of grain boundaries. Especially, the distribution of Ca ions around grain boundaries is very important to attain low core loss. It was found that SO42- ions prevents the uniform distributions of Ca ions on grain boundaries, and oxygen partial pressure of sintering atmosphere can influence the amount of Ca ions that are on grain boundaries effectively.View full abstractDownload PDF (1594K) -
Tsuyoshi Miyamoto, Tatsuya Nakamura, Yoshihiro Yamada2003 Volume 50 Issue 8 Pages 609-612
Published: August 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSPolycrystalline Li-Zn ferrites were prepared by the ceramic sintering method, and their complex permeability spectra were measured. The low-frequency permeability decreased with an increase in the Li-ferrite fraction. However, the natural resonance frequency shifted higher when the fraction of Li-ferrite was increased. According to our previous model, the complex permeability spectra were numerically separated into spin rotation and domain wall motion contributions. For the spin rotational component, which played an important role in the high frequency region, the static spin susceptibility decreased and the spin resonance frequency shifted higher with an increase in the Li-ferrite fraction. The product values of the static spin susceptibility and the spin resonance frequency, corresponding to the Snoek's product value, took a maximum value at a certain fraction of Li-ferrite. This was reflected to the performance of the single layered electromagnetic wave absorber using the polycrystalline ferrites.View full abstractDownload PDF (288K) -
Nobuki Yanagiuchi, Tatsuya Nakamura, Tomonari Takeuchi, Hiroyuki Kagey ...2003 Volume 50 Issue 8 Pages 613-617
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPolycrystalline Ba3Co2Fe24O41 specimens were fabricated by usual solid state sintering or spark plasma sintering method. SEM observation showed that densification occurred simultaneously with grain growth in the solid state sintering. The spark plasma sintering produced dense ceramics with fine grain structure. Their complex permeability spectra were evaluated with a help of numerical calculation based on our previous model, which is related to the microstructure. Both spin rotation and domain wall motion affected the permeability in the solid state sintered specimens. The permeability of the spark plasma sintered specimens was mainly attributed to spin rotation.View full abstractDownload PDF (1784K) -
Yukio Takada, Takeshi Tachibana, Takashi Nakagawa, Takao A. Yamamoto, ...2003 Volume 50 Issue 8 Pages 618-625
Published: August 15, 2003
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSZ-type hexagonal barium ferrite samples in which a part and/or all of Ba2+ was substituted for Sr2+ were prepared by the ceramic method, Ba3Co2Fe24O41, Ba1.5Sr1.5Co2Fe24O41 and Sr3Co2Fe24O41. The Sr2+ substitution was found favorable for lowering temperature and oxygen partial pressure in the sintering process. Ba1.5Sr1.5Co2Fe24O41 and Sr3Co2Fe24O41 were obtained at 1523K under Po2=101.3kPa and at 1483K under Po2=21.3kPa, respectively. We investigated crystal and magnetic anisotropies of the materials by measuring the magnetizations and XRD patterns of specimens which were shaped by pressing the sample powders in a magnetic field. Both the results indicated that the magnetic moment lay in the basal plane of the hexagonal structure in Ba3Co2Fe24O41 and Ba1.5Sr1.5Co2Fe24O41, whilst was significantly off from the basal plane in of Sr3Co2Fe24O41. We measured their powder neutron diffraction patterns and analyzed them by the Rietveld method to estimate site distributions of Sr2+-Ba2+ and Fe3+-Co2+, and orientation of the magnetic moment. The analyses revealed (1) Sr2+ preferentially occupied a site out of two sites available for Ba2+, (2) the magnetic cation distribution in Sr3Co2Fe24O41 was significantly different from those of the others, and (3) the magnetic moment angle with respect to the c-axis was 52.3° in Sr3Co2Fe24O41 whilst almost 90° in the others.View full abstractDownload PDF (599K) -
Shinya Sakurada, Akihiko Tsutai, Tomohisa Arai2003 Volume 50 Issue 8 Pages 626-632
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have developed isotropic magnet powder with the composition of (Sm, Zr)(Fe, Co)zB0.1Nx (z=9-10) prepared by rapid quenching, annealing, and nitrogenation. The presence of both zirconium and cobalt make it possible to realize a nearly single phase of the TbCu7 structure with a c/a ratio as high as 0.87. These powders show a high saturation magnetization of 1.6-1.7 T. A small addition of boron is effective for forming the amorphous phase in the rapidly quenched alloys and for obtaining uniform and fine grains of the ThCu7 phase after annealing. The combination of the high saturation magnetization and the fine grains leads to high Br and high (BH)max. The magnetic properties of these powders are as follows: Br=1.00-1.07T, HcJ=640-880kA/m, (BH)max=160-180kJ/m3. Isotropic bonded magnets fabricated using such powder show highest (BH)max of 120kJ/m3. These bonded magnets also show good thermal stability and good oxidation resistance.View full abstractDownload PDF (2072K) -
Takashi Iseki, Takashi Ishikawa, Atsushi Kawamoto, Kenji Omori2003 Volume 50 Issue 8 Pages 633-635
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have developed heat-stable SmFeMnN magnet powder made by reduction and diffusion method. The average particle size was 20-30μm. Slightly crushing the powder enhanced remanence of the powder, which resulted in high magnetic properties: Br: 1.12T, iHc: 597kA/m, (BH)max: 178kJ/m3. The deterioration of the coercivity was only 7% after exposure in air at 433K for 1000h. The temperature coefficient of coercivity-0.26%/K is close to that of SmCo5 magnets. On the other hand, the analysis of the structures by field emission-transmission electron microscopy (FE-TEM) and energy-dispersive X-ray (EDX) revealed that the powder was composed of nanocrystalline grains surrounded by amorphous phase. It seems that the powder shows high coercivity (-955kA/m) due to these microstructures.View full abstractDownload PDF (1495K) -
Yasunobu Ogata, Takashi Takami, Yutaka Kubota2003 Volume 50 Issue 8 Pages 636-641
Published: August 15, 2003
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of the simultaneous partial substitution of Co2+ for Fe3+ and of La3+ for Sr2+ ion in Sr ferrite on the magnetic properties of anisotropic Sr ferrite magnets was investigated. It was found that the coercive force iHc of Sr ferrite magnets is increased without significant decrease in residual flux density Br by La-Co substitution. The temperature coefficient of coercive force was found to be also improved by La-Co substitution. The residual orbital magnetic moment of Co2+ ion is considered to play a main role to increase the coercive force of La-Co substituted Sr ferrite magnets.
Based on these results, the new grade (9B) Sr ferrite magnets were developed, whose typical magnetic properties are Br=440mT (4400 G), iHc=350kA/m (4400Oe).View full abstractDownload PDF (1924K) -
Hiroshi Yamamoto, Tetsuro Kobayashi2003 Volume 50 Issue 8 Pages 642-647
Published: August 15, 2003
Released on J-STAGE: November 19, 2010
JOURNAL FREE ACCESSA single-phase Sr-Nd-Co M-type ferrite fine particles have been produced by the chemical coprecipitation and heat treatment method for the sample having a formula {(SrO⋅n/2(Fe2O3))}100-x-y(Nd2O3)x(CoO)y (n = 7.0, x= 1.0-10.0, y =1.0-10.0). The chemical reagents used are FeCl3⋅6H2O, SrC12⋅6H2O, NdC13⋅6H2O, and CoCl2⋅6H2O. A solution containing Sr2+, Fe3+, Nd3+, and Co2+ is poured into a solution of NaOH (pH=13.0).
Then the precipitated products are boiled for 2 h and they are carefully washed and dried. The obtained fine particles are heated at a temperature between 950 and 1100°C for 2h in air to get a single-phase Sr-Nd-Co M-type ferrite fine particles. The most prominent magnetic properties have been observed for the sample with the compotion of { SrO⋅3.5(Fe2O3) }94.0(Nd2O3)2.0(CoO)4.0; they are as follows: σs=89.5 × 10-6 Wb⋅m/kg (71.2 emu/g), σr=45.3 × 10-6 Wb⋅m/kg (36.0 emu/g), HcJ=490.0 kA/m (6.16 kOe), α (σr) =-0.20 %/°C, α (HcJ)=0.08 %/°C and Tc=465.3°C.View full abstractDownload PDF (1549K) -
Yumi Kawaai, Takashi Takeda, Shinichi Kikkawa2003 Volume 50 Issue 8 Pages 648-652
Published: August 15, 2003
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSRf-sputter deposition was applied to investigate a possibility to obtain ferromagnetic Fe-Ni thin films having different coercivity for ferromagnetic layers in magnetic spin tunneling junction. Two kinds of targets were used in the deposition applying rf-power in a range up to 250 W; a composite target where Ni chips of 1 × 1 cm2 were distributed on an Fe target of 3 in diameter in 25% in area ratio, and a 75Fe-25Ni alloy target. The deposited thin films were more Ni rich than the target compositions due to different sputtering rates between Fe and Ni. The films were γ-(Fe, Ni) with Ni 40-55 at% composition in the usage of the former target and α-(Fe, Ni) with Ni 30-40 at% composition in the latter target. The latter films had large magnetization values of about 200 emu/g. They were metastable and converted to γ-(Fe, Ni) above 600 K. There was an enough coercivity difference between 55 Oe for the thin film prepared applying rf-power of 100 W and 30 Oe for the film prepared at 250 W using the alloy target.View full abstractDownload PDF (460K)
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