Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 45, Issue 7
Displaying 1-17 of 17 articles from this issue
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  • [title in Japanese]
    [in Japanese]
    1998 Volume 45 Issue 7 Pages 614
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.614
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  • The Past and Future of the Magnetic Recording Media
    Tatsuji Kitamoto
    1998 Volume 45 Issue 7 Pages 615-620
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.615
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    The crystal structure of goethite (α-FeOOH) is orthorhombic. When precipitated from aqueous solution, goethite particles are fine and acicular. The fine size and acicular shape were essential to the evolution of high performance magnetic recording media such as audio tapes, video tapes and floppy discs. A series of studies on the preparation, the topochemical reaction and the characterization of iron oxyhydroxides and related oxides were one of the most important fields of the Japan Society of Powder and Powder Metallurgy in the 1960's and 1970's. They had contributed greately for the establishment and eventual spectacular development of magnetic recording industries. In this paper, the author wish to describe the past important milestones and personal expectations to the future of magnetic recording media.
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  • Iron Acicular Particles in Metal Audio Tapes
    Osamu Kohmoto, Toshiki Hanafusa
    1998 Volume 45 Issue 7 Pages 621-623
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.621
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    The lattice constant (a0), crystallite size (d) and the crystallite orientation of a-Fe acicular particles in commerciallyavailable audio metal tapes were studied using x-ray diffraction. The value of a0 is determined to be 0.28669 ± 0.00005 nm, which is slightly larger than that of pure Fe. The reason of the small discrepancy of a0 was estimated to be due to 0.1 at%-Al addition into Fe. The acicular particle consists of many crystallite: the crystallite sizes along long axis of acicular particle (22 nm) is larger than the short axis (14 nm). The tendency that the [100] axis of Fe crystallite aligns with the long axis of the acicular particle is observed.
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  • Development of Ferrite Raw Powder Production Process with Thermal Decomposition of Iron and Manganese Chloride Solution by Spray Roaster
    Tatsushiro Ochiai
    1998 Volume 45 Issue 7 Pages 624-629
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.624
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    The present review is concerned with the development of the power ferrite with high performance and low cost, which is especially manufactured by use of the spray roasting of Fe-Mn binary system. Electro-magnetic properties of ferrite are influenced by chemical composition and microstructure and also being very sensitive for stress induced in the grain and bulk. Therefore, to obtain the ferrite having high performance by the conventional solid phase reaction process, it is very important to use raw material powder with high purity and good dispersion itself. The highly homogeneous dispersion of Fe and Mn ions which are consist of the main composition of power ferrite, was successfully carried out by our new process which is characterized by the spray roasting the mixed solution of both Fe and Mn chloride, purified in advance. We finally established the whole process from raw materials to sintering process for the production of ferrite with higher performance and lower cost.
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  • Effect of anion on the formation of ferrite
    Takuya Aoki, Naoyoshi Sato, Takeshi Nomura
    1998 Volume 45 Issue 7 Pages 630-635
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.630
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    Ferric oxide which is a principal raw material for ferrite production contains anion as impurities. Because it has been generally produced from iron chloride or iron sulfate solutions obtained from acid-cleaning waste liquid. In this paper, we have investigated the effect of anions on the formation of Ni ferrite. It is shown that the spinel phase is formed at lower temperature in the case of using iron oxide containing a small amount of chloride ions compare with that case of sulfate ions. It was also found that the formation of nickel chloride during calcination resulted in the low temperature formation of Ni ferrite, and that iron oxide was not affected in its own activity. The reaction mechanism for the low temperature formation of Ni ferrite is considered to being via the formation of nickel chloride. Solid state reaction for the formation of Ni ferrite in the NiC12-Fe2O3 system is phase boundary controlled. The activation energy in the NiC12-Fe2O3 system was much lower than that of the value of Ni ferrite formation in the NiO-Fe2O3 system.
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  • Electric and Magnetic Properties of Newly Synthesized Spinel Manganites
    Kazumasa Uchida, Ikuka Chiba, Atsunori Kamegawa, Hitoshi Takamura, Mas ...
    1998 Volume 45 Issue 7 Pages 636-640
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.636
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    The crystal structure and electric and magnetic properties of newly synthesized spinel manganites were investigated. CuNi0.5Mn1.5O4 had cubic spinel structure, and magnetoresistance effect like CMR in perovskite manganites was observed in this system for the first time. Judging from the calculation of effective-valency according to the result of Rietveld analysis, it was estimated that both of Mn3+ and Mn4+ are in octahedral site. This fact may be related with the reason why magnetoresistance effect appealed in this system.
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  • Effect of Solid Reducing Agent of Si on Formative Condition of SrFe2-W Type Ferrite and Magnetic Properties
    Ken Unno, Atsunori Kamegawa, Hitoshi Takamura, Motofumi Homma, Masuo O ...
    1998 Volume 45 Issue 7 Pages 641-645
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.641
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    The W-type hexagonal ferrite, with the chemical formula of Sr(Ba)Fe2+Fe3+16O27, is the future candidate ferrite because of its 10% higher saturation magnetization in comparing with that of M-type ferrites. A complicated atmosphere control during sintering process is, however, required in manufacturing of W-type ferrites, which will be unsuitable for industrial production. Recently, it is reported that a high performance SrFe2-W type ferrite can be produced with using a carbon powder as a solid reducing agent and controlling the drying temperature of green compacts. The energy product (BH)max of this SrFe2-W type ferrite is reported to be 5.3MGOe. The purpose of this study is to clarify the effects of drying treatment of green compacts, and addition of Si as a new solid reducing agent on the formative condition of SrFe2-W type ferrite.
    The drying treatment at 373K and following by firing at 1473K for 10 hours in Po2=250 Pa are the suitable formative conditions for silicon addition to achieve high volume fraction of SrFe2-W phase and this sample has the(BH)max of 10.3kJ.m-3.
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  • Thermal Decomposition Behavior of PVA as Organic Binder of Spray Dried Nd-Fe-B System Powder
    Ken Makita, Osamu Yamashita, Tetsuya Senda
    1998 Volume 45 Issue 7 Pages 646-651
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.646
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    Debinding process under hydrogen atmosphere is effective to eliminate the residual carbon contents in Nd-Fe-B system green body which is compacted by using spray dried powder. But it is not effective for elimination of residual oxygen contents comparatively. The emitted gas from compacted body of Nd-Fe-B system spray dried powder including poly(vinyl alcohol)(PVA) as a binder was analyzed by mass spectroscopy. Much emission of a fragment with m/z=16 was observed only when spray dried powder was heated under hydrogen atmosphere. The fragment was proved to be methane by gas chromatography. DTA curve measured simultaneously for spray dried powder showed absorption of hydrogen by Nd-Fe-B in the vicinity of 220°C, and the desorption of hydrogen started above 230°C. The latter was accompanied by enhancement of the emission of hydrocarbon such as methane. Hydrogen atom sent out from Nd-Fe-B powder would make the fragments from main chain of PVA stable, and accelerates the debinding by vaporization of methane and other hydrocarbon with low mass number. In contrast, degraded side-chain of PVA would immediately combine with neodymium of Nd-Fe-B powder and form Nd2O3 which remains in the sintered body.
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  • Effect of Weak DC Magnetic Fields on the AC Magnetization of a Melt-Processed YBa2Cu3Oy
    Ken-ichiro Harashima, Shinjiro Tochihara, Hiroshi Yasuoka, Hiromasa Ma ...
    1998 Volume 45 Issue 7 Pages 655-660
    Published: July 15, 1998
    Released on J-STAGE: July 12, 2010
    DOIhttps://doi.org/10.2497/jjspm.45.655
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    We studied, both theoretically and experimentally, the ac magnetic response of type-II superconductors superimposed on a weak Hdc field. Theoretical simulations were made within the construct of the Kim-Anderson critical-state model, where the critical current density Jc is assumed to be given by Jc=k/(Bo+|Bi|). k and Bo are temperature-dependent material parameters, and Bi is the local flux density in the sample. We also measured complex susceptibilities Xn=X′n-iX″n (n=1, 2, 3, 5, 7) of a melt-processed YBa2Cu3Oy specimen and analyzed the observed Xn by applying the magnetization equations derived from the Kim-Anderson model. We found that the experimental results were qualitatively well reproduced. Present results indicate that, for a specimen of which Jc sensitively varies with Bi, the effect of a weak Hdc should be explicitly taken into consideration for studies of the ac magnetization.
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  • The Modulation and Synthesis for Bi2Sr2CuOδ under Ambient Oxygen Partial Pressure
    Toshinobu Niinae, Yasunori Ikeda, Yoshichika Bando, Yoshihiro Kusano, ...
    1998 Volume 45 Issue 7 Pages 661-665
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.661
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    The cation stoichiometric Bi2Sr2CuOδ was successfully obtained by solid state reaction under ambient oxygen pressures (Po2=0.2, 1atm). The modulation period as estimated by means of X-ray powder diffraction was λ ?? 4.7b for Bi2Sr2CuOδ synthesized under Po2=1atm, which is shorter than that for Bi2.125Sr1.875CuOz(λ ?? 15b). The Bi2Sr2CuOδ synthesized under Po2=1 atm showed metallic conductivity down to 2K, whereas it done under Po2=0.2 atm showed superconductivity with Tc ?? 8K. By annealing in Ar, Tc was raised up to 16K. At the same time, it was newly found that the modulation is disproportionate into two types with A, λ ?? 4.7b and λ ?? 5.5b.
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  • Lithium Intercalation/Deintercalation of the Bi-2212 Phase by Electrochemical Method
    Makoto Nakanishi, Yoshiaki Uwazumi, Masashi Fujiwara, Jun Takada, Yosh ...
    1998 Volume 45 Issue 7 Pages 666-669
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.666
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    The effects of electrochemical removal reaction of lithium from the Li-doped Bi-2212 phase on its structure and superconducting properties have been studied. Lithium was inserted into and removed from Bi2Sr1.5Ca1.5Cu2Oz through an electrochemical. method at a constant applied potential at room temperature. The original crystal symmetry, tetragonal structure, was maintained and any secondary phase was not formed throughout the electrochemical reactions. Lattice parameter c of the doped samples, LixBi2Sr1.5Ca1.5Cu2Oz, decreased and Tc changed reversibly as the lithium content x decreased, It reveals that the electrochemical reactions were intercalation/deintercalation of the Bi-2212 phase with lithium.
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  • Sintering Mechanisms of Mechanically Alloyed 2Nb/Al Powder by Puls Current Pressure Sintering
    Masateru Nose, Takekazu Nagae, Masaru Yokota
    1998 Volume 45 Issue 7 Pages 670-674
    Published: July 15, 1998
    Released on J-STAGE: July 12, 2010
    DOIhttps://doi.org/10.2497/jjspm.45.670
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    The mechanically alloyed powder of 2Nb/Al composition was sintered in the temperature ranges from 973K to 1173K using either the pulse current pressure sintering (PCPS) apparatus or a conventional electric furnace. X-ray diffraction patterns for the compacts sintered by PCPS showed the weak Al peaks in halo, although the diffraction patterns for the compacts sintered by conventional electric heating did not show the Al peaks. A set of 2Nb/Al powder compact and balls of SUS304 stainless steel were sintered at 973K by PCPS in order to make clear the reason why the Al peaks were detected. Using EDX, Nb were not, but Al were detected in the circumference area in contact with 2Nb/Al compact on the surface of SUS ball. This fact indicates that evaporation and deposition of Al occured during PCPS. It can be estimated that the contact area in the earlier stages of PCPS was heated up to the order of 2000 to 4000K.
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  • Consolidation of Stellite and Its Bonding to Stainless Steel by Spark Plasma Sintering
    Shigeaki Sugiyama, Yasushi Sugawara, Mitsuhiko Kimura, Koichi Asari, T ...
    1998 Volume 45 Issue 7 Pages 675-679
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.675
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    Spark plasma sintering (SPS) was applied to consolidating Stellite powder and bonding Stellite to stainless steel. Sintered compacts with relative densities more than 99.5 % were obtained by the SPS conditions, applied pressure=50 MPa, heating rate=50°C min-1, sintering temperature=1070°C and holding time=l0 min. They have good mechanical properties due to their finely-dispersed structures of carbide particles. Stellite and stainless steel could be easily bonded by SPS of Stellite powder placed on rod like stainless steel under the same conditions as the consolidation of Stellite powder. Diffusion zones in junctions were very narrow because of short-time and low-temperature sintering.
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  • Influence of the charged amount of ball media on grinding speed in wet rotational ball milling
    Kozo Yokota, Hiroshi Watanabe, Hisakazu Tomino, Yoshihito Kondo
    1998 Volume 45 Issue 7 Pages 680-684
    Published: July 15, 1998
    Released on J-STAGE: December 04, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.680
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    This paper describes the correlation between particle reduction rate and charged amount of balls using alumina powder as a specimen. The reduction rate of particle size increased with increasing the rotation number. But in the case when ball was.charged more than half the amount of volume of the pot, there exist a critical rotation number where the smallest particle was produced. Beyond the critical rotation number where-balls moved along with inner wall of pot, the powder could not be ground effectively. The critical rotation number of pot depended on a charged amount of balls.
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  • Effect of Residual Pores on Magnetic Properties of PM Ferritic Stainless Steels
    Katsushi Kusaka, Tomoya Suzuki, Testuya Kondo
    1998 Volume 45 Issue 7 Pages 685-691
    Published: July 15, 1998
    Released on J-STAGE: July 12, 2010
    DOIhttps://doi.org/10.2497/jjspm.45.685
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    A fundamental study was made mainly on the magnetic properties of the two PM ferritic stainless steels with some residual pores. In this case, powder particle size and sintering conditions (1373-1573K×20-240min) were employed as parameters to the residual pore morphologies of sintered materials.
    The results were summarized as follows:
    (1) The magnetic properties are more or less sensitive to powder particle size, sintering temperature and time of powder compacts.
    (2) Magnetic induction(B10)behaves as well as electrical resistivity (ρ), almost only depending on sintered density in apparence.
    (3) Max.permeability (μm) is fairly changed by powder particle size and sintering conditions for a given sintered density, due to pore shape and crystal grain size.
    (4) Coersive force (Hc) is also changed by powder particle size and sintering conditions for a given sintered density, especially due to crystal grain size.
    (5) Tensile properties are not largely influenced by pore morphologies, probably because of stress relaxation rising near by residual pores.
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  • Production of Nd-Fe-B alloys by mechanical alloying
    Tetsuji Saito
    1998 Volume 45 Issue 7 Pages 692-696
    Published: July 15, 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.692
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    Elemental neodymium, iron, and boron powder mixtures were mechanically alloyed in argon, hydrogen and nitrogen atmospheres. The resultant powders and those annealed at various temperatures were examined by X-ray diffraction, optical microscopy, and vibrating sample magnetometer. It was found that these powder mixtures absorbed hydrogen and nitrogen during the mechanical alloying. Heat treatment of the mechanically alloyed powders prepared in hydrogen atmosphere resulted in desorption of hydrogen gas. The resultant powders consisted of Nd2Fe14B ferromagnetic crystallites and showed a high coercivity value. On the other hand, heat treatment of the mechanically alloyed powders prepared in nitrogen atmosphere did not result in desorption of nitrogen gas. The resultant powders consisted of iron and neodymium nitrides and showed a coercivity as low as that of the powder mixtures. The Nd-Fe-B powders prepared by mechanical alloying in hydrogen atmosphere were magnetically isotropic.
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  • ERRATUM
    1998 Volume 45 Issue 7 Pages 699
    Published: 1998
    Released on J-STAGE: May 22, 2009
    DOIhttps://doi.org/10.2497/jjspm.45.699
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