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Volume 47, Issue 1
Displaying 1-18 of 18 articles from this issue
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Kiyokata Iizumi, Daisuke Maezawa, Takeshi Sasaki, Katsuya Kudaka2000 Volume 47 Issue 1 Pages 3-8
Published: January 15, 2000
Released on J-STAGE: November 19, 2010
JOURNAL FREE ACCESSCrB2 obtained by the solid state reaction of chromium and boron could not be sintered even at high temperatures without being applied pressure, but it has been sintered by hot-pressing at about 1700°C. The pressureless and pressure sinterings of Cr-B (atomic ratio 1:2) mixed powder produced by mechanochemical processes were studied. These reactive sinterings were enhanced by the exthothermic heat of reaction of the unreacted Cr-B (1:2) mixture. Mechanochemical effects on the sinterability are interpretted by a negative factor, i.e., a decrease in the reaction heal which predominates the pressure sintering, and a positive factor, a pulverization of the mixed powders which predominates the pressureless sintering with grinding time. The optimum experimental conditions of the pressureless sintering were 30h and 1800°C for grinding time and sintering temperature, respectively, whereas those of the pressure sintering were 10h and 1500°C for grinding time and sintering temperature, respectively.View full abstractDownload PDF (6803K) -
Yoshikazu Tanaka, Akihiko Yanagitani2000 Volume 47 Issue 1 Pages 9-14
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMagnetic properties of Mn-AI-C alloy magnets produced from gas-atomized alloy powders were improved by using the finer particles because the cell size and the segregation of finer particles were very small. So, by using more rapidly solidified powders, the excellent characteristics of Mn-Al-C magnet was expected. In this work, the effect of the rapidly quenched ribbon on the characteristics of Mn-Al-C alloy was investigated, and discussed from the point of rapid solidification. The specimen were prepared by the rapid solidification apparatus with the single roll in the Ar gas atmosphere. Phase analysis of as-quenched and after heat treatment was done by X-ray diffraction analysis. Magnetic properties were estimated on the magnet made from the powder-extrusion process. Tile magnetic properties of Mn-Al-C alloy were improved by using of more rapidly solidified ribbons. Br, iHc, (BH)max and anisotropy of ferromagnetic T-phase were improved to higher level by using thiner thickness ribbons. At extrusion ratio 4, (BH)max value of 57.lkJ/m3 was obtained by the magnet prepared from rapidly solidified ribbons of 12gm average thickness, which was much higher than that by cast process or by gas atomization process. The improvement of magnetic properties of the extruded magnet from rapidly solidified ribbons was found to be caused by the finer microstructure and very small amount of non-magnetic phases such as γ2-phase and β-phase.View full abstractDownload PDF (2341K) -
Yoshikazu Tanaka, Yoshikazu Aikawa2000 Volume 47 Issue 1 Pages 15-22
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMn-Al-C magnet has been produced by powder-extrusion process since 1989. It is known that rapidly solidified powder improves the magnetic properties of magnet. In this work, the possibilities to improve magnetic properties for powder-extrude Mn-Al-C-alloy were studied by using heat treated gas atomized powders. The effect of isothermal annealing at 973K for gas atomized powders on the magnetic properties after extrusion was investigated. The effect of homogenization at 1373K for gas atomized powders was also investigated. After these heat treatments sphase volume ratio in powder-extruded magnet was increased. In consequence, better saturation magnetization (4πIs (at0.8MA/m)) and residual magnetization (Br) were obtained. By annealing at 973K maximumenergy product ((BH)max) was improved since Br was increased with keeping the consistent intrinsic coercivity (iHc). By 1373K homogenization for gas atomized powders, Br was significantly increased while iHc was decreased, so that (BH)max was inferior to the one without heat treatment. This iHc decreasemay be caused by the grain coarsening of sphase after extrusion, which was due to the coarsening of e phase during 1373K homogenization heat treatment. As a result, it can be said that the increasing sphase volume ratio as well as keeping fine structure is important to improve magnetic properties of Mn-Al-C magnet.View full abstractDownload PDF (2058K) -
Masahiro Yokouchi2000 Volume 47 Issue 1 Pages 23-29
Published: January 15, 2000
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSB4G(W, Mo)B2 hard materials were sintered by hot pressing, to develop a new hard material that is superior in heat resistance and wear resistance to other hard material. In this study, the effect of Mo content on mechanical properties and phase formation of the hard material was investigated. The results were summarized as follows:
(1) The B4C/(W, Mo)B2 hard material was densified at 2173K for 3.6ks by hot pressing.
(2) It was found that bending strength and fracture toughness were improved by adding Mo(5-20vol%) to B4C/(W, Mo)B2 hard materials. The 20vol%Mo added B4C/(W, Mo)B2 hard material had the highest values for the 4-points bending strength (850MPa) and the fracture toughness(6.1MPa. m1/2).
(3) In the case of 5-30vol% Mo added B4C/(W, Mo)B2 hard materials, the needle shaped crystals was observed in SEM micrographs. As the results of TEM, AES, XRD analysis, the needle shaped crystal phase was (W, Mo)B2 and its crystal system was hexagonal.View full abstractDownload PDF (3481K) -
Norio Matsui, Katsuhiko Matsui, Keizo Kobayashi, Akira Sugiyama, Kimih ...2000 Volume 47 Issue 1 Pages 30-35
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSFe-48at%Cr alloy powders were synthesized by mechanical alloying (MA) of elementary Fe powder and Cr powder using a planetary ball milling at various times under 1.33kPa argon gas atomosphere. The obtained MA powders were consolidated at 1123K for 0.3ks by spark plasma sintering (SPS) process and rectangular sintered bodies having a size of 30 mm long, 5 mm wide and 2 mm thick were prepared. Tensile specimens were prepared from these sintered bodies by grinding. The results of the tensile test, the tensile strength increased and the elongation decreased in MA-SPS process as the milling time of MA increased. It is conjectured that oxygen and nitrogen were mingled during the MA process. The tensile strength of Fe-48at%Cr alloy prepared by MA-SPS process using MA powders milling for 360ks was about 1045MPa and the elongation of that was about 11%. Fe-48at%Cr alloy prepared by this process existed no σ phase.View full abstractDownload PDF (3667K) -
Katsuyoshi Kondoh, Atsushi Kimura, Ryuzo Watanabe2000 Volume 47 Issue 1 Pages 36-41
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEffect of Mg on sintering phenomenon of aluminum alloy powder has been examined. The relative density of sintered material increased by 9% when the Mg content increased. XPS analysis clarified the chemical reaction at the most-top surface of aluminum alloy powder during heating. It is considered that Mg acted to deoxidize Al2O3 surface film of aluminum alloy powder and accelerated sintering between particles. As a result, the tensile strength and elongation of sintered materials remarkably increased and the dimples are observed at the fractured surface of the tensile test specimen when the Mg content in aluminum alloy powder increased.View full abstractDownload PDF (5205K) -
Katsuyoshi Kondoh, Atsushi Kimura, Ryuzo Watanabe2000 Volume 47 Issue 1 Pages 42-46
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe nitrogen content of the aluminum alloys including tin sintered in nitrogen gas was less than 1/10 compared to the sintered material without tin. It is considered that liquid tin covered the surface of aluminum particles and prevented the formation of AIN during sintering. The amount of in-situ formed AIN depended on both the chemical compositions of raw powder and the specific particle surface area and in particular was proportional to the surface area.View full abstractDownload PDF (1859K) -
Hitoshi Hashimoto2000 Volume 47 Issue 1 Pages 47-51
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTheoretical analysis of mechanical alloying process conducted by ball mills is indispensa during mechanical alloying should be investigated. In this paper, some results of the author's computer-based motion simulation of individual balls during ball milling of metal powders were presented. One of the results was helpful to understand the metal powder coating behavior during mechanical alloying by a tumbling ball mill.View full abstractDownload PDF (464K) -
Seizo Takahashi, Takeo Nakagawa2000 Volume 47 Issue 1 Pages 52-57
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA long cylinder-shaped compacts were formed by a single-action tooling from dry and loose iron powder admixed with 1 mass% zinc stearate, 10% fine iron powder and 1% micro wax powder. Avarage green density of formed compact reached a relative density of 88%, and the variation in density throughout the green compact was reduced to less than 3% in the height of 40 mm. Sufficient flowability of densified powder at pressing side was experimentally confirmed by investigating the change of density distribution during compaction and the flowability was effective by admixing with fine spherical powder. The radial crushing strength of the sintered compact amounted to 400 MPa.View full abstractDownload PDF (2029K) -
[in Japanese]2000 Volume 47 Issue 1 Pages 60
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (100K) -
Hiroshi Yoshinaga, Hitoshi Wada, Tetsuo Sakai2000 Volume 47 Issue 1 Pages 61-67
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNew flake-like metal powder such as copper, nickel, nickel alloy and nickel-cobalt composite, which could provide good electrical conductivity and binding ability were developed as new electrode producing materials. A mixture of hydrogen storage alloy powder for metal hydride electrode or nickel hydroxide powder for nickel electrode with the flake-like metal powder was roll-pressed on a nickel-mesh substrate without polymeric binder and a formed nickel substrate. A laminated network structure of the flake-like metal powder was formed to connect tightly hydrogen storage alloy powder or nickel hydroxide powder in the electrode. The flake-like metal powder provided higher discharge capacity (utilization efficiency) and higher mechanical strength for the electrodes than a conventional powder.View full abstractDownload PDF (10004K) -
Takuya Tamura, Takahiro Kuriiwa, Takeshi Fuda, Atsunori Kamegawa, Masu ...2000 Volume 47 Issue 1 Pages 68-72
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have developed the new compositional V-7.4at%Ti-7.4at%Zr-7.4at%Ni alloys that consist of BCC as main phase, and C14 Laves phases along grain boundary. They have the flat plateau region in the PCT curves and 2.0mass% protium absorption-desorption capacity. This paper investigates electrochemical characteristics of V-7.4at%Ti-7.4at%Zr-7.4at%Ni protium absorbing alloys as metal hydride electrodes. The electrodes which were prepared by mixing as-cast alloys with 300mass% Ni powder show 372mAh/g discharge capacity at 10mA/g discharge current. This result indicates that V-7.4at%Ti-7.4at%Zr-7.4at%Ni alloys work as metal hydride electrodes. It was found that the electrodes which were prepared by mixing as-cast alloys with Ni powder and heat-treated for 1h at 873K can discharge by the protium that can't desorb in a gas reaction.View full abstractDownload PDF (3255K) -
Yukio Tominaga, Shinya Nishimura, Kaname Matsumoto, Takeshi Fuda, Taku ...2000 Volume 47 Issue 1 Pages 73-77
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTi-V-Cr BCC solid solutions are known to absorb a high amount of protium. But, relations of their microstructures with their protium absorption-desorption properties are not systematically studied. The purpose of this study is to clarify the effects of V content and heat-treatment on the protium absorption-desorption properties of Ti-(0-35)at%V-Cr alloys.
Addition of V to Ti-Cr alloys was effective in forming a BCC phase. However, with decreasing V content, a Laves phase was formed and an effective protium capacity decreased.
Anealling at 1573 K was effective to flatten the plateau region and enlarge the effective protium capacity. A Ti-10V-55.4Cr alloy, which contained a laves phase in the as-cast state, became a BCC single-phase after annealing over 1573K. Even though the alloy contains only 10 at%V, this heat-treated alloy showed an effective protium capacity of 2.5 mass%H.View full abstractDownload PDF (2316K) -
Toshiyuki Koyama, Norikazu Sasida, Takahiro Yamakawa, Yoshikazu Inoue2000 Volume 47 Issue 1 Pages 78-85
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA new-type porous strucutre, named ‘KAMINARI-OKOSI’ struture, was succesfully prepaerd utilizing both aquaous gel-casting slurry and resin filter and measured their pore size distribution, air permiability, bending strength and electrical conductivity. The slurry compositon contained pore former such as carbon, nickel caobonate to induce relatively small pore in calcinated body. On the other hand, a resin filter immersed into the slurry also acted as an another pore former and left relativery large pore after calcination. By the contribution of these two different vanishing materials, obtained porous body was consist of large porous sphericals bonding together and realized a bi-modal open-pore size distribution showing relatively large size pore (around 10 × 10-6m) and ordinary size pore (around 10-6m). After reduction at 1073K in H2, Ni/YSZ cermets having the ′KAMINARI-OKOSI′-type structure were allowed to high air permiability, and which made possible to fire at high temperature and to obtain high bending strength. This porous body having ′KAMINARI-OKOSI′-type structure was combined with a porous body having conventional porous structure, named ′KARUME-YAKI′-type one, to make thin YSZ electrolyte layer on the surface of porous body with ease and form a number of 3-phase interface site as active catalytic points. Splendid characteristics of the porous body combined ′KAMINARI-OKOSI′-type and ′KARUME-YAKI′-type structure in ratio of 6:4 by thicness were obtained as follows: air permiability of around 10-7m4·kg-1·Sec-1 at room temperature, 3-point bending strength of 34 MPa at room temperature and electrical conductivity of around 104S. m-1 at 1073K.View full abstractDownload PDF (4337K) -
Jun Ishida, Takayuki Ichikawa, Yasuo Takeda, Nobuyuki Imanishi, Osamu ...2000 Volume 47 Issue 1 Pages 86-90
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSUsing a good mixed oxide ion and electrical conductor makes it possible to reduce CO2 to CO even by the unelectrical methods. The La(Sr)CrO3-based perovskite oxide was chosen as the mixed conductor because these oxides are stable under a reduced condition. In order to increase the oxide ion conductivity, Ga was doped for Cr site synthesizing La1-xSrxCr1-y(Ga1-zMgz)yO3-δ La1-xSrxCr1-y(Ga1-zMgz)yO3-δexhibit high electronic and oxide ionic conductivity, thermal stability and stability in the wide oxygen partial pressure. Oxygen permeation rate was increased with temperature and increasing Ga rate.View full abstractDownload PDF (380K) -
Keijiro Terashita, Tatsuya Hashimoto, Kei Miyanami2000 Volume 47 Issue 1 Pages 91-96
Published: January 15, 2000
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe aim of this study is to evaluate the binderless process for manufacturing positive electrodes for primary batteries. Composite particles for positive electrodes were prepared by dry-coating manganese dioxide with graphite using a high-performance planetary mill; particle size distribution and composite particle fluidity were measured. The particles were then compression-molded into tablets whose electric resistance and density were measured.
The measurements have proven that positive electrodes with low electric resistance and high density can be produced by compression-molding composite particles properly prepared by the dry-coating process, i.e., without using binder. Experiments were also carried out to clarify the optimal processing time for composite particles, as well as optimal particle size and centrifugal acceleration, that yields composite particles with superior electric resistance and density, most suitable for positive electrodes. It has also been verified that the electric resistance and density of positive electrodes produced by this binderless dry process are equal or superior to those attained by the conventional wet process.View full abstractDownload PDF (3203K) -
Keijiro Terashita, Hideya Asano, Kei Miyanami2000 Volume 47 Issue 1 Pages 97-102
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe aim of this study is to establish methods for evaluating the dispersion of electrode materials in the process of manufacturing electrodes for secondary lithium ion batteries. In an experiment, materials were mixed and kneaded into paste, with various agitation times and binder-adding methods. After being conditioned, the paste was applied to the base plate, and electrode material dispersion in the coating film was evaluated. Methods for evaluating such dispersion before application were also studied.
The study revealed that electrode material dispersion can be quantitatively evaluated by measuring the volume resistance, gloss, thickness and apparent density of the film, and systematically examining the measured values. The results of the study imply that dispersion in the paste can be evaluated by measuring paste particle size distribution and electric conductivity.View full abstractDownload PDF (540K) -
Keita Uchiyama, Yasuo Takeda, Nobuyuki Imanishi, Osamu Yamamoto, Mitsu ...2000 Volume 47 Issue 1 Pages 103-108
Published: January 15, 2000
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSpinel type Li1+xMn2-xO4(x=0.00-0.10)was chemically delithiated into Li0.5-0.9Mn2-xO4 by using Br2 as an oxidant. Li was extracted from Li1+xMn2-xO4 to Li0.5-0.9Mn2-xO4 keeping their spinet structure. The solubility of Mn into the electrolye is significantly large in Li-extracted Li1-xMn2O4 spinels. The discharge-charge behavior of Li/Li0.51Mn1.99O4 whose Li was extracted from Li0.99Mn1.99O4 showed different behaivor from that of Li/Li0.99Mn1.99O4, while that of Li/Li0.74Mn1.90O4 whose Li was extracted from Li1.10Mn1.90O4 was similar to that of Li/Li1.10Mn1.90O4. This shows that Li1.10Mn1.90O4 is the most stable composition in Li1+xMn2-xO4 spinl system.View full abstractDownload PDF (396K)
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