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Volume 42, Issue 6
Displaying 1-17 of 17 articles from this issue
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[in Japanese]1995 Volume 42 Issue 6 Pages 684
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (84K) -
Nanao Horiishi1995 Volume 42 Issue 6 Pages 685-689
Published: June 15, 1995
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSMagnetic recording medias have been developed in response to the recording system itself. The development of magnetic media industry of today is due to the invention of coated magnetic tape developed by P.F.Pfleumer in around 1930. I tried to survey the hystory of development on magnetic recoerding technologies, and to investigate into the magnetic recording materials made from magnetic oxides, especialy cobalt contained ironoxide particles powder. In the trends proceeding the social netwark of imformation system against the age of 2001, some thin films of metalalloy seems to be better for the recording multimedia than coated one. I was confirmed that the formation of Co-r-Fe2O3 films which have high magneto-optical effect and large perpendicular magnetic anisotropy can be obtained only by the sputtering method. It may be insinuated that ironoxide materials have more possibility to be used as multimedia recording materials.View full abstractDownload PDF (346K) -
Masao Kiyama1995 Volume 42 Issue 6 Pages 690-694
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe conditions had been studied for the formation of ferromagnetic precipitates of MxFe3-xO4 (M = divalent metal ion, such as Fe2+, Zn2+, Co2+or Mn2+), BaFe12O19 and SrFe12O19 in the presence of aqueos media. We succeeded in preparing the needlelike xCoFe2O4(1-x)Fe3O4 and platelike 6xFe3O4(1-x) BaFe12O19 particles for magnetic recording materials. This paper describes the conditions for their formation and their magnetic properties at room temperature.View full abstractDownload PDF (270K) -
Akira Suzuki, Miyuki Kasahara1995 Volume 42 Issue 6 Pages 695-701
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe metal powder first used in the audio field (around 1980) had an Hc value of 1100 to 12000e, and a particle length of 0.5μm. Since audio systems have not changed, the situation is basically the same today, but improvements are constantly being made in electromagnetic conversion and coating characteristics. With the development of eightmillimeter video, the characteristics of metal powder changed significantly, with an Hc value of 15000e and a particle length as small as 0.3μm (around 1985). With the development of high-band eight-millimeter video around 1990, the degree of fineness was further improved, with an Hc value of 16000e and a particle length of 0.2μm being achieved.
Current metal powder has an He value of 1700 to 18000e and a particle length of 0.15μm. With the development of next-generation systems already underway, even greater degrees of fineness and higher He and σs values are being demanded. As time pass on, the realization of characteristics, such as 0.1μm in length and 20000e, will soon become an accomplished fact.View full abstractDownload PDF (336K) -
Jiro Yoshinari, Norio Higuchi1995 Volume 42 Issue 6 Pages 702-707
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSOblique-evaporated tape has widely been used for Hi8 VTR and has recently attracted major interest as high density recording tape for digital home-use VTR. In order to obtain high output signal at high densities, the magnetic recording mechanism was investigated by computer simulation, considering the recording magnetization and the phase shift. According to the simulation, the magnetic properties to perform high output signal at high densities were derived. Considering this simulation, evaporated tapes were produced. Columnar growth direction, Co composition, oxygen flow rate, number of the layers and film thickness were optimized. Consequently, oblique-evaporated tape with high output signal at high densities was realized under this simulation results.View full abstractDownload PDF (325K) -
Nobuyuki Hiratsuka, Satoshi Suzuki, Koichi Kakizaki, Mitsuo Sugimoto1995 Volume 42 Issue 6 Pages 708-711
Published: June 15, 1995
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSAcicular cobalt ferrite fine particles were prepared by using conventional ceramic method. Acicular α-FeOOH and C10H14O4Co⋅2H2O were sintered at 900°C for 5 hours in air, and then were quenched. The acicular cobalt ferrite fine particles, length of about 1.2μm and an aspest ratio of about 12, had coercivity of 1 kOe (80 kA/m) and magnetization values of 67 emu/g (0.45 Wb/m2). Therefore, they were applicable to magnetic recording medium. The torque curve of a coated film which were admixed with the fine particles and binders indicated the magnetic anisotropy of the fine particles was in the direction parallel to long axis of them. The magnetic anisotropy constant was 1.22 × 103 J/m3. The acicular fine particles had several crystallites, which were arranged parallel to <111> direction of spinet structure.View full abstractDownload PDF (3208K) -
Hiroshi Yamamoto, Haruhito Kumehara, Hiroaki Nishio1995 Volume 42 Issue 6 Pages 712-717
Published: June 15, 1995
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe preparation of fine particles of SrO.6Fe2O3 with single phase has been realized by controlling the chemical coprecipitation and heat treatment . A solution containing Fe3+ and Sr2+ in the ratio 8.0 was poured into a solution of NaOH (pH=13.0). The precipitated products were boiled for 2hs and they were carefully washed and dried. The obtained powder was heated at 900°C for 2hs in air, and resulted in Sr-M single phase. The maximum values of magnetic properties are σs=87.0×10-6 wb-m/kg, HcJ=501.3 kA/m, average anisotropy filed HAave=945.4 kA/m, and Tc=462°C.View full abstractDownload PDF (2457K) -
Kazunori Sakamoto, Kazunori Kubota, Hiroshi Suzuki, Keijiro Terashita1995 Volume 42 Issue 6 Pages 718-722
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn this work, in order to make clear the effect of kneading process for high dispersion as well as the stability of the magnetic paint, fine metal particles were continuously kneaded by twin screw extruder, and followed a dispersion by beads agitator mill. The degree of kneading and dispersion were evaluated by the rheological property of magnetic paint, . the gloss and surface roughness of a coated magnetic film. The adhesiveness of binder resins for the surface of metal particles was evaluated by mesuring the amount of adsorbtion of binder resins and fatty acids. It was clear that binder resins adhered to the many adsorbtion points existed on the surface of the metal particles by use of kneading process. Since the surface adhesion force was very strong, the binder resins didn't separate from the surface of metal particles, even the use of a dilute of magnetic paint. It was anticipated that the kneading process would be very usefull for the stability of magnetic paint.View full abstractDownload PDF (362K) -
Kenji Higashi1995 Volume 42 Issue 6 Pages 725-734
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPositive exponent superplasticity (exhibits superplastic behavior at very high strain rates over 1 s-1) has been observed in nano or near-nano scale aluminum alloys, which have been developed to be 50-500 nm in grain sizes by advanced processing methods. The experimental results on high-strain-rate superplastic materials are reviewed and related to the dependencies of the ability of superplasticity on grain size and the nature of grain boundaries, as well as the state of materials. The optimum superplastic strain rates are found to be strongly dependent on the refinement of grain structures, also the superplastic elongations were critically controlled by the accommodation process to relax the stress concentration resulting from grain boundary sliding, involving an accommodation helper such as soft phases, amorphous phases or liquid phases.View full abstractDownload PDF (5143K) -
Masato Kakihana, Toshiya Abiko, Sugitani Yoshinori, Minoru Osada, Masa ...1995 Volume 42 Issue 6 Pages 735-740
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHigh-purity ceramic samples of the modulation-free Bi2-xPbxSr2Ca1-yYyCu2Oz with a wide range of composition (x=(l+y)/2±0.2, 0.25≤y≤0.8) have been prepared by the polymerized complex method. The method is based on the formation of a polymer complex which is obtained through polyesterfication between metal citrate complexes and ethylene glycol. This method yielded almost homogeneous x=0.8 materials with Y compositions of y=0.2, 0.6 and 0.8 through relatively short sintering periods of 32 hours. The corresponding X-ray diffraction and Raman scattering analyses have shown that the materials are virtually of single phase with only minor traces of Sr2.5Bi0.5Pb3Ca2CuOz (< 1 %). The lattice parameters a and b increase, while the c-axis value decreases with increasing Y content, y. Complex magnetic susceptibility measurements have confirmed the presence of a single bulk Bi2212 phase. For Bi1.2Pb0.8Sr2Ca0.8Y0.2Cu2Oz, the onset temperature of superconducting transition Tc was 89.5 K and the transition width (10-90 %) of full diamagnetism was 6.4 K for the measuring field of 100 mOe. The variation of Tc with Y content in the modulation-free Bi2212 phase was similar with that observed in the modulated Bi2Sr2Ca1-yYyCu2Oz.View full abstractDownload PDF (400K) -
Melting of the Electrode and the Formation of DropletRyohei Kumagae, Masami Yoshitake, Kensuke Hidaka, Masaharu Tokizane1995 Volume 42 Issue 6 Pages 741-745
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe study on the operation practice of plasma rotating electrode process (PREP) was carried out. The experiments were performed under the condition with and without deflection of the center of the plasma from that of the electrode. It was concluded that the application of an appropriate deviation of the plasma center from rotating electrode center was suitable for obtaining uniformly sized particles, since the electrode consumed keeping nearly flat surface which caused the occurence of smooth flow of molten metal to the edge of the surface. In such a situation, at the edge of the molten surface, a stable cyclic undulation of liquid layer which supplies nearly uniform droplet was produced, although the changes in heat input were occured during PREP.View full abstractDownload PDF (2674K) -
Kazuo Asaka1995 Volume 42 Issue 6 Pages 746-751
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThis report shows the results of diffusion bonding of compacts consist of Fe-1C and Fe-3Cu, and some kinds of Fe-Cu-C compacts with different compositions during sintering. The diffusion bonding of the combination of Fe-1C inner and Fe-3Cu outer starts at relatively low sintering temperature which is around 1100K. Contrary to this, that of the opposite combination of Fe-3Cu inner and Fe-1C outer starts at 1356K which is the melting point of Cu. However, the bonding strength of both combinations sintered at 1403K shows approximately equal value.
In the combinations of Fe-Cu-C compacts with different compositions to each other, the choice of inner material which contains higher carbon than the outer results in high diffusion bonding strength, which is sufficient to applying for mechanical parts.View full abstractDownload PDF (1704K) -
Takehiko Miyazaki, Kenichi Kaneko, Koji Hayashi1995 Volume 42 Issue 6 Pages 752-757
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSIn powder metallurgy processings, oxide films on the surface of metallic powder particles are generally reduced during sintering. In some cases, however, the oxide films can be used as an important element for obtaining the special performance materials, such as SAP and flaky aluminum sintered compact having unique voltage-current characteristics. In this study, the conditions such as powder particle shape and size (d), relative green density (Dg), and sintering temperature (Ts) for remaining continuous oxide films in aluminum sintered and green compacts were investigated by electrical resistivity measurement .
The results obtained are as follows: (1) The measurement should be carried out under the breakdown voltage at which an electric current suddenly increases in voltage-current characteristic. (2) Semi-quantitative equations for the contiguity (C) of metal/metal or the continuity (1-C) of oxide films were proposed. (3) The continuous oxide films remained easily in the flaky powders as compared to the granular powders, and it was semi-quantitatively clarified that the continuous oxide films in the granular powders tended to remain in the case of smaller d, lower Dg and lower Ts.View full abstractDownload PDF (485K) -
Mamoru Mabuchi, Kenji Higashi1995 Volume 42 Issue 6 Pages 758-761
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSRecently, there has been a growing interest in the development of fine-grained microstructures for superplastic forming of aluminum alloy matrix composites. In the present paper, Si3N4w/Al-Zn-Mg and Si3N4p/Al-Zn-Mg composites were processed by a powder metallurgy route and constant true strain rate tensile tests were carried out in a wide strain rate range from 10-4 to 100 s-1 at 818 K in order to investigate superplastic properties of both composites.
The Si3N4w/Al-Zn-Mg composite exhibited a maximum elongation of 230 % at a strain rate of 10-1 s-1 and the Si3N4p/Al-Zn-Mg composite showed a maximum elongation of 330 % at a higher strain rate of I s-1. Thus, the Al-Zn-Mg alloy matrix composites exhibited superplastic behavior at high strain rates (>10-1 s-1).View full abstractDownload PDF (232K) -
Yuji Muramatsu, Tsuneo Ohokoshi, Hiroo Suga, Kunio Funami1995 Volume 42 Issue 6 Pages 762-766
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSTungsten dispersion Cu-1.0vol%W plates were prepared by conventional sintering of mixed powder compacts of Cu and W. Prepared plates were subjected to cyclic treatment of cold rolling and annealing to achieve further densification. In this study, the densification due to cold rolling and mechanical properties of cold rolled plates were examined in comparison with those of oxide dispersion Cu-1.0vol%Y2O3 prepared by the same methods as the tungsten dispersion copper plate.
In both W and Y2O3 dispersion Cu plates, the density increased effectively by repeating the treatment of cold rolling and annealing. However, it has been clarified to be difficult to attain the theoretical density by this method. Mechanical properties of both Cu plates were improved with the increase of density, but elongation property tended to become saturated or decreased when the reduction of thickness exceeded 50%.View full abstractDownload PDF (2970K) -
Saburo Sano, Kiichi Oda, Yasuo Shibasaki, Kenichi Koizumi, Tomoya Mata ...1995 Volume 42 Issue 6 Pages 767-770
Published: June 15, 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMicrowave sintering of ZrO2-3mol%Y2O3 green bodies formed by slip casting was studied using a 2.45GHz microwave in a cylindrical cavity. The onion-shape crack was observed after microwave sintering without SiC plate, but crack free sintering bodies have been obtained by microwave sintering with SiC plates. Final density was about 5.5g/cm 3 (relative density: about 90%) in the sintering temperature range of 1150-1450°C. By SEM observation, it was seen that the sintered body had pore free structure near surface, but there were many pores in inner part. A reason of low final density is that many pores remained in inner part since the shrinkage of surface part proceeded at the first stage of microwave sintering.View full abstractDownload PDF (2755K) -
1995 Volume 42 Issue 6 Pages 773
Published: 1995
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (18K)
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