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Volume 48, Issue 12
Displaying 1-12 of 12 articles from this issue
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Shunichi Takemoto, Osamu Takumi, Hiromasa Takeuchi, Yoshiharu Koizumi2001 Volume 48 Issue 12 Pages 1107-1111
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of electrical resistivity and magnetoresistance on the Jahn-Teller distortion of perovskaite type La1-xSrxMnO3 (LSMO) were examined. The samples were the polycrystalline specimens that are well grown the crystal in the <100> axis, and prepared by the sintering process with the synthesis of powder oxides La2O3, SrCO3 and Mn2O3, respectively. It was proven by the measurement of XPS in respect of ge-orbit and t2g-orbit of the Mn3+ on the Jahn-Teller ion of LSMO crystal, and the difference of both energy levels had been 2 eV. The electrical resistivity of the samples becomes a minimum, when Sr composition ratio x are 0.2 and 0.5. This fact means that the hopping of the conduction electron becomes active due to relaxation of the Jahn-Teller distortion and transformation from the insulator phase to metallic phase on account of substituting the Sr ion for the part of the La ion in LaMnO3. It was proven to become a maximum by linking the magnetoresistance effect with the phenomenon, when electrical resistivity undergoes transition by the effect of Sr composition ratio.View full abstractDownload PDF (372K) -
Seizo Takahashi, Kiyoaki Irie, Takeo Nakagawa, Julian A. Thomas, Randa ...2001 Volume 48 Issue 12 Pages 1112-1118
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPure iron powders admixed with fine carbonyl iron powder of 10mass%, micro wax powder of 1 mass% and zinc stearate of 1 mass% are formed to combined compact by a uniaxial press machine. The powder flows from ring to undercut during pressing, the local density of undercut division becomes higher and the difference in density in sintered compact can be reduced. The density of undercut increases following the ring height increase. Shearing strength of sintered compact is increased in proportion to the density of undercut and the maximum value is gotten 230MPa. The powder flow into the undercut during pressing is inclined. Therefore, the lower density region exists at the just below the mother material. As a result of pressing tested powder by floating die tooling, it is possible to prevent a crack. The feature of this compaction is powder flow within the die cavity during dry press forming by mixing a small amount of binder.View full abstractDownload PDF (3833K) -
Tomio Satoh, Michiru Sakamoto, Hua-Nan Liu2001 Volume 48 Issue 12 Pages 1119-1125
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPowder metallurgy process was adopted to improve the mechanical properties and the elevated temperatures oxidation resistance of high chromium cast irons with hypo- and hyper-eutectic compositions. Rapidly solidified powders produced by a centrifugal atomization process were used as a starting material. The powders were sintered by spark plasma sintering. Mechanical properties and high-temperature oxidation resistance of the sintered compacts were investigated and compared to those of the cast ingots. The sintered compacts have remarkably refined and homogeneous microstructure in comparison with the ingots. The hardness of the sintered compacts is higher than that of the ingots in both hypo- and hyper-eutectic alloys. The hardness of the hyper-eutectic sintered compact reaches 68 (HRC) on Rockwell C-scale. High-temperature oxidation resistance of the sintered compacts is superior to that of the ingots independent of the alloy composition. Weight gains of the hypo- and hyper-eutectic sintered compacts decrease a half and one-fifth compared with those of the ingots at 973 K, respectively. The excellent oxidation resistance of the sintered compacts can be ascribed to the formation of homogenous oxide film on the surface of the compacts due to the refined microstructure.View full abstractDownload PDF (6382K) -
Hisamichi Kimura, Akihisa Inoue, Kenichiro Sasamori, Hyang-Yeon Kim, T ...2001 Volume 48 Issue 12 Pages 1126-1131
Published: December 15, 2001
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSAl-Fe-Cr-Ti and Al-V-Fe alloys prepared by the powder metallurgy (P/M) process have high strength exceeding 600 MPa, high-elevated temperature strength exceeding 300 MPa after holding for 100 hours at 573 K and more excellent wear resistance than commercial A390 aluminum alloy. In this work mechanical properties of the P/M Al93Fe3Cr2Ti2 and Al94V4Fe2 alloys were found to be improved by the addition of misch metal (Mm). P/M Al92Fe3Cr2Ti2Mm1 alloys containing quasicrystalline phase were prepared by extrusion of argon gas atomized powders at 673 K, where the atomized powders sieved into the sizes smaller than 75μm were used. The P/M Al92Fe3Cr2Ti2Mm1 alloy has a mixed structure consisting of Al, quasicrystal and compounds phases and exhibits good mechanical properties as follows: ultimate tensile strength (σUTS) of 680±13 MPa, 0.2% proof strength (σ0.2) of 670±10 MPa, plastic elongation (εP) of 0.3±0.1%, Young's modulus (E) of 91±3 GPa and Vickers hardness (Hv) of 230±3, respectively, at room temperature, and alas of 347±5 MPa, σ0.2 of 315±3 MPa and εP of 1.8±0.3%, respectively, after holding for 100 hours at 573 K.View full abstractDownload PDF (1850K) -
Kazushige Kamihira, Tadayuki Fujii2001 Volume 48 Issue 12 Pages 1132-1138
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to understand in detail the secondary recrystallization behavior of fine-grained molybdenum alloy sheets dispersed with TiC and HfC particles of 0.8mol%, the effects of kinds of dispersed particle on the secondary grain growth behavior and annealing textures in hot-rolled dispersion strengthened molybdenum sheets were investigated. First, it was recognized that dispersed particles, which are present in the form of Ti (Ox, C) and Hf (Ox, C) as complicated oxides and carbides at the primary recrystallized grain boundaries, play an important role as inhibitors to the normal grain growth and conversely as promoters of the abnormal grain growth at higher temperatures in both molybdenum alloy sheets. Moreover, the temperature at which secondary recrystallization commences from both molybdenum alloy sheets is strongly dependent on the kinds of dispersed particle and is correspondent to their dissociation and dissolution. Secondary, it was found that most components of secondary textures correspond to very weak components in the primary recrystallization textures and are related by a rotation of approximately 20°-30° about the <110> axis of the strong primary recrystallized {111} (<112>+<110>) matrice in both molybdenum alloy sheets.View full abstractDownload PDF (5551K) -
Masato Arakawa, Tadashi Kanasaku, Koji Amezawa, Naoichi Yamamoto2001 Volume 48 Issue 12 Pages 1139-1144
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new low temperature processing route of lithium-manganese spinel was developed. In this process, a lithium manganese spinel was prepared by extracting Li ion from LiMnO2 compound in distilled water or in acidic solution of low H2SO4 concentration. In some reaction conditions, lithium-manganese spinel can be obtained below the temperature of 100°C in H2SO4 acid aqueous solution. The new processing route of lithium manganese spinel below 100°C throughout entire route may be easy to the environment.View full abstractDownload PDF (2355K) -
[in Japanese]2001 Volume 48 Issue 12 Pages 1146
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (73K) -
Yasushi Sato, Kohtaro Yoshioka, Valery Petrykin, Minoru Osada, Masato ...2001 Volume 48 Issue 12 Pages 1147-1151
Published: December 15, 2001
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSPolycrystalline samples of (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3O7+δ tetragonal superconductor for Ca content(x)from 0.0 to 0.6 were synthesized by a simple aqueous solution technique using citric acid. The combined results of X-ray diffraction and Raman scattering analysis indicated that the polycrystalline samples for the entire Ca content (x) were of single-phase character. The Tc onset values for (x) from 0.0 to 0.6, determined precisely from the complex magnetic susceptibility measurements, increased from 45.0 K for x=0.0 to 78.7 K for x = 0.4, remained almost constant at 80 K between x=0.5 and x=0.6. It was also found that sintering condition affected rather dramatically superconducting properties in this system.View full abstractDownload PDF (392K) -
Takeshi Horiuti, Shouichi Nasu, Kentaro Ohhashi, Naoaki Hayashi, Mikio ...2001 Volume 48 Issue 12 Pages 1152-1155
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have adopted iron iodide intercalation into Bi2Sr2CaCu2Oy. The intercalation compound was prepared by heating pelletized mixture of polycrystalline Bi2Sr2CaCu2Oy powder and Fe powder in iodine atmosphere.
The powder X-ray diffraction pattern showed the same result as of FeI2+xBi2Sr2CaCu2O8+y synthesized by Kijima group. The Mössbauer spectra showed α-Fe2O3(60%), 40% iron iodide intercalation performed. From a.c. magnetic susceptibility, the compound showed insulating. Iodine intercalation was also performed in order to compare their superconductivity.View full abstractDownload PDF (277K) -
Katsuyoshi Hotta, Hajime Miyazawa, Takashi Ogue, Kazushi Sugawara, Har ...2001 Volume 48 Issue 12 Pages 1156-1159
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe bulk sample simply produced by pressing calcined superconductor powder shows no superconductive properties. Laser scan transforms however such non-superconducting bulk material into superconductive one partially along the scanned area. The goal of this study is to make superconductive circuits on the surface of the(Bi 2223 system)non-superconductive bulk by scanning focused laser beam as designed. This paper reports the effect of 150W CO2 laser irradiation on the superconducting property of the bulk by changing the following conditions: beam scan speed (bss), beam scan times(bst)and assist gas pressure(agp).The best result of Tc(end)=66.5 K was obtained when the laser irradiation was performed with bss=10 mm/min, bst=1 stroke and agp=49 kPa. Superconductive crystals were grown at the laser irradiated area with depth of-300μm. The crystals were oriented to the same direction of the beam scan.View full abstractDownload PDF (2660K) -
Katsuyoshi Hotta, Toshikazu Nishi, Kenichi Nihei, Yasuo Watanabe, Haru ...2001 Volume 48 Issue 12 Pages 1160-1163
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe experimented on the reflective attenuation properties of Bi 2223 superconductor against electromagnetic waves. Sample was prepared as a pellet(32mmφ×2mm, or 32mmφ×5mm) which consists of the superconductor with the average particle size of 50μm or below and epoxy resin. The wt% proportion of the superconductor and epoxy resin was changed to some extent.
The pellet was irradiated by the electromagnetic wave in the ranges from 10.0 to 11.0 GH2 (X band) and from 20.0 to 26.0 GHz (K band) at 290 K and 77K to measure its reflective intensity by using vector network analyzer.
The attenuation value defined in the experiment as a difference between reflective intensity of the sample and that of the same size copper plate gave the maximum attenuation of 60 dB at 10.5 GHz for X band and that of 37 dB at 23.5 GHz for K band.
The maximum attenuations of 52.7 dB at 10.7 GHz and 63.3 dB at 25.2 GHz were obtained for the average particle size of 170μm at 80wt% content although no significant attenuations were observed for the particle size of 270/um at the same content.
Such attenuation properties will be understood in terms of a kind of percolation mechanism.View full abstractDownload PDF (228K) -
Hiroshi Terada, Katsura Matsuura, Takuya Fujii, Mamoru Fukunaga2001 Volume 48 Issue 12 Pages 1164-1167
Published: December 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe prepared Ag-sheathed Nd system tape by the compression molding powder-in-tube method. Ag sheathed tapes of Nd system superconductors were studied for sample with nominal composition of NdBa2Cu3Oy(Nd123). The critical current density of sample apparently depended on the thickness of the tape and temperature gradient, and increased markedly with decreasing the tape thickness. The maximum value of the critical current density of sample reached 2.0×105 A/cm2 at 6.7 K in zero magnetic field for a tape with 0.3 mm thickness and 1.1×104A/cm2 at 77K in zero magnetic field.View full abstractDownload PDF (1588K)
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