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Volume 51, Issue 10
Displaying 1-9 of 9 articles from this issue
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Asami Murai, Hiroshi Terada, Takuya Shibata, Seiko Nakatsukasa2004 Volume 51 Issue 10 Pages 719-723
Published: October 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAs well-known that partial substitution of a Pb for Bi in the Bi-Sr-Ca-Cu-O system has been found to sharply increase the volume fraction of the high-Tc phase when both the starting material and the heating process are appropriate. This paper discusses the influence, in this case of the CaCO3 or CaO used as a raw material of Ca and the cold isostatic pressing (CIP) method on the superconducting properties of Bi1.8Pb0.4Sr2Ca2+xCu3.2Oy prepared by the solid-atate reaction. The superconducting characteristic obtained from the electrical resistance for the specimens sintered at 850°C for 200h, became gradually lower from 105K to 70K with increasing a Ca content from O to 0.8 mol. The Jc value increase with x was a maximum of 1820A/cm2 at x=0.4 sintered at 850°C to 200h.View full abstractDownload PDF (3599K) -
Yukihiro Kadogawa, Harada Eisuke2004 Volume 51 Issue 10 Pages 724-729
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSmAlO3 was synthesized by the TW method. As the starting solution, each aqueous solution of Al(NO3)39H2O and Sm(NO3)36H2O was dissolved in proper amount of distilled water. Various quantities of Si(OC2H5)4)(TEOS) and a small amount of 2M-HCl as catalysis were mixed into the starting solution. In a sample obtained by heating the gel with TEOS of 0.90×10-2 mol for 30 min, pure SmAlO3 in a single phase was not obtained at the temperature of 1100°C, because the obtained sample had each small amount of SmO and β-Cristobalite liberated from SmSiO3. It was thought that SmAlO3 was formed as a degradation product of Sm4Al2O9, simultaneously as a product of the reaction of γ-Al2O3 and Sm2O3 in the progress of its decomposition when the decomposition of SmSiO3 proceeded in preference to the degradation of Sm4Al2O9. From comparison of their X-ray diffraction patterns for samples with two kinds of TEOS content consisting of 1.35×10-2 mol and 0.90×10-2 mol, it was thought that α-Al2O3 was transformed into γ-Al2O3.View full abstractDownload PDF (420K) -
Tomio Satoh, Kenji Uchida, Yuji Kawakami, Shin-ichi Nishida, Nobusuke ...2004 Volume 51 Issue 10 Pages 730-735
Published: October 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSCarbon fiber/metal matrix composites were fabricated by powder metallurgy process, spark plasma sintering followed by rotary swaging, to achieve high heat conduction and low thermal expansion. Pitch-based carbon shortfiber was mixed with the powder of aluminum or copper. A volume fraction of the fiber was 40%. Orientation angles of the fiber to the compacting direction were measured in the longitudinal sections of the composites. Hermans' orientation parameter was adopted to evaluate the fiber orientation. The swaging process caused the parameter to change markedly from -0.9 to 0.9 in both of Al and Cu matrix composites. These values mean that the fiber is dispersed perpendicularly to the compacting direction in the sintered objects and dispersed in parallel to that one in the objects with swaging process. Thermal conductivity of the composites increases with increasing Hermans' orientation parameter. The thermal conductivity of Al and Cu composites was 210 and 420 W⋅m-1⋅K-1 at room temperature, respectively. Coefficients of thermal expansion of both Al and Cu matrix composites decreased approximately 25% as compared with those of monolithic Al and Cu metals.View full abstractDownload PDF (5058K) -
Ritsuko Tsuzuki, Masaya Ishihara, Katsuyoshi Kondoh, Eiji Yuasa2004 Volume 51 Issue 10 Pages 736-740
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMg2Si/Mg composite which shows high mechanical properties was expected to be produced via solid-state synthesis using AZ31 powder and Si powder as initial material. For the first step of this research, thermal behavior of AZ31 and Si was investigated in this paper.
AZ31/Si compacts with various compositions were examined by differential scanning calorimeter and analyzed by X-ray diffraction to confirm reactability between them.
The detailed result indicated that Si could completely react with AZ31 and synthesize Mg2Si when heated at 753 K, which is almost the same temperature as in the case of using purity Mg. The starting temperature of synthesis became lower and exothermic heat increased as Si content increased. Repeated plastic working (RPW) was also effective to decrease their synthesizing temperature. That is because the reaction between Mg and Si occurred easily due to the mechanisms of RPW process such as (1) breakage of oxide film on the surface of Mg particles and (2) refinement of both of the Mg and Si particles. In addition, it was observed as the result of optical microstructure that Mg2Si particles were dispersed into matrix and they existed at the interface of Mg grain.View full abstractDownload PDF (1809K) -
Kimitoshi Sato, Takamasa Ishigaki, Hidehiro Kamiya, Yusuke Moriyoshi2004 Volume 51 Issue 10 Pages 741-748
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSOxide-carbide composites have excellent mechanical properties. However, the composites have not been so extensively applied to industrial use because of the difficulty in pressureless sintering of them. In our work, improvement of pressureless sintering of ZrC-Al2O3 composites is shown. Heating of bare green compact in an argon atmosphere gives a relatively low density of sintered bodies. The change of lattice constant of the ZrC phase, and chemical composition of sintered bodies indicate the incorporation of oxygen into ZrC during firing. The oxygen-containing phase is chemically denoted as ZrC(O), in which oxygen atoms are dissolved into the ZrC of the NaCl type crystal structure. The incorporation is related to alumina evaporation during firing, that hinderes densification. We examine preserving of particle size of ZrC powder during mixing and the alumina encapsulation of specimens during firing to prevent evaporation of specimens and proceed the sintering. Addition of MgO leads to further improvement of sintered density, i.e., the relative density of ZrC25-Al2O3 75vol% composite exceeded 98%. We discuss the pressureless sintering behavior of ZrC(O)-Al2O3 composites comparing it with that of TiC(O)-Al2O3 composites as we previously reported.View full abstractDownload PDF (4333K) -
Katsuhiro Maekawa, Terutake Hayashi, Yasuo Sato, Kazumi Minagawa, Hide ...2004 Volume 51 Issue 10 Pages 749-755
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSintering and lamination characteristics of Fe-Cu atomized powder have been investigated to meet requirements on recycling of automobiles and manufacture of lightweight structure. The greentape laser sintering method using Nd:YAG pulse laser and powder tape called "greentape" is employed for the fabrication of Fe-Cu porous structure. Extensively investigated is influence of laser parameters, such as voltage, pulse width and average power upon the state of liquid sintering or both surface texture and tensile strength of the sintered specimens. A water-atomized Fe-5mass%Cu powder (3-8μm in diameter) is superior to the gas-atomized Fe-2mass%Cu one (5-38μm) in monolayer strength, but being difficult to laminate due to the existence of massive pores. It is successful to laminate 16 layers of gas-atomized greentape (190μm in thickness each) at a voltage of 198V, a pulse width of 2.0ms and an average power of 13W. Porous structure can be controlled by changing these laser parameters, whereas it is necessary to resolve distortion of the sintered part by means of a segmented laser irradiation.View full abstractDownload PDF (6671K) -
Kazumi Minagawa, Keisuke Ida, Hideki Kakisawa, Susumu Takamori, Yoshia ...2004 Volume 51 Issue 10 Pages 756-760
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe studied the 3-Dimensional Printing method to fabricate the metallic components from powder. The laminating fabrication by starch-coated metal powder was proposed as rapid prototyping. In this research, the effects of the drying time, laminating pitch, size of adherent powder, and the starch-coating thickness on the handling of green body were investigated. Based on the obtained results, the optimum process conditions were determined.View full abstractDownload PDF (7046K) -
Takashi Suzuki, Tadayuki Tsutsui, Kei Ishii, Akira Kishibuchi, Kunihir ...2004 Volume 51 Issue 10 Pages 761-765
Published: October 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIt is required a function that the compressor of a car air conditioner in case overloaded will be disconnected from the engine power. Presented here is the development of a mechanical fuse part having such function. This part can be realized by satisfying two functions simultaneously; (1) the part has sufficient fatigue strength to transmit power without breaking, and (2) it breaks promptly to disconnect the power if an overload occurs. This can be realized by developing a material having high fatigue limit ratio (fatigue strength/tensile strength). Such material was investigated and was found that a high fatigue limit ratio is achieved by steam treating a Fe-Cu-C material sintered compact with a decreased amount of carbon. This newly developed material has recently been applied to such required mechanical fuse parts.View full abstractDownload PDF (2916K) -
Akinori Muto, Aki Hanioka, Thallada Bhaskar, Kiyotaka Inoue, Yusaku Sa ...2004 Volume 51 Issue 10 Pages 766-772
Published: October 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA porous carbon membrane plate (PCMP) was prepared from some kinds of phenol resins and rice husks by carbonization in a N2 stream and activation in a CO2 stream under high pressure. Effect of the carbonization/activation time and temperature, heating rate, ratio of the phenol resins and particle diameter of the raw material (rice husks) on density and strength of the PCMP was examined.
The PCMPs without crack were prepared when pressurization was ceased at 450°C from both the phenol resins and rice husks. These PCMP were 17 mm in diameter and 3mm in thickness. They had smooth surface and micro pore structure. The pore structure of PCMP was affected by the mixture ratio of the phenol resins. The PCMP with higher density was prepared from the rice husk including more ash (silica).View full abstractDownload PDF (5589K)
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