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Volume 71, Issue 8
Displaying 1-13 of 13 articles from this issue
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Ryuji Wada, Noriko Kobayashi, Toshiyuki Fujii, Susumu Onaka, Masaharu ...2007 Volume 71 Issue 8 Pages 587-591
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSElastic interaction energy between two super-circular inclusions with purely dilatational misfit strains is evaluated. For the calculation, a two dimensional model is used together with linear elasticity for the cubic anisotropy of copper. When two inclusions lie parallel to <100> of the copper crystal, attractive interaction is observed between the inclusions. The maximum of the attractive interaction is realized when the two inclusions exist close to each other. As the inclusion shape becomes circular to square-like, the maximum interaction energy decreases and the distance between the two inclusions to give the maximum increases. Furthermore, the two inclusions are found to be most stable when they have the same size. In addition to the elastic interaction energy, interface energy of the matrix/inclusion interface is also considered. The results show that the two inclusions tend to become the same size even for a situation when the interface energy is much more dominant compared with the elastic interaction energy.
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Tohru Nobuki, Jean-Claude Crivello, Toshiro Kuji2007 Volume 71 Issue 8 Pages 592-597
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSIn this work, the Mg17Al12 phase was successfully synthesized by the Bulk Mechanical Alloying (BMA) based on repeating compression and extrusion cycles in the metallic die. After 2000 cycles of compression and extrusion, nano-structural Mg17Al12 phase was obtained in bulk form.
X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and differential scanning calorimetry (DSC) analyses were carried out for several mechanically milled powder mixtures. The qualitative and quantitative analysis of phase abundance, evolution of microstructure and distribution of particles size were studied.
It was demonstrated that Mg17Al12 alloy is able to absorb a large amount of hydrogen, higher than 3 mass% of Hydrogen.
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Kazuma Kutaragi, Yasuhito Harada, Kazunori Tanaka, Yoshitake Nishi2007 Volume 71 Issue 8 Pages 598-602
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSIn order to strengthen carbon fiber reinforced polymer (CFRP), effects of a pre-stressing on mechanical properties in stress-strain curve of tensile test have been investigated. The pre-stressing remarkably improves the apparent elastic coustant, tensile strengrh and fracture strain. They probably depend on the residual compressive stress induced by the pre-stressing in CFRP.
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Takamitsu Honjo, Tohru Nobuki, Masafumi Chiba, Toshiro Kuji2007 Volume 71 Issue 8 Pages 603-607
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSMg-based alloys possess light-weight and high hydrogen absorption capacity, so they have been investigated extensively for several decades. Also, attention has recently been paid to graphite as a hydrogen absorber. In this study Mg-C composites were prepared by ball milling and their hydrogenation properties were investigated. Powders were first mixed with a 1:1 molar ratio of Mg (99.9% purity) to graphite (99.9% purity), and then milled using ZrO2 balls in a ZrO2 pot for 60 hours. This process was performed in a vibration ball mill at the speed of 345 rpm under an Ar gas atmosphere. The powders prepared in this way were handled in a glove box filled with an Ar gas. From the XRD patterns, it was found that the peak corresponding to the Mg phase shifted slightly to lower diffraction angles, indicating that the lattice spacing of the Mg phase was expanded by alloying partially with C in the powders. On the other hand, graphite peaks were rather broadened. An affinity for the powders with hydrogen was confirmed from the absorption experiment at the temperature of 453 K and the hydrogen pressure of 1.8 MPa. The total amount of absorbed hydrogen was estimated to be 3.5 mass% from the TDS measurement.
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Shigeru Saito, Kazuya Kurokawa, Shigenari Hayashi, Toshiyuki Takashima ...2007 Volume 71 Issue 8 Pages 608-614
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSCompositions with tie-lines between the σ, γ, and δ phases in a ternary Re-Cr-Ni system were investigated at 1423 K by heat-treating various ternary Re-Cr-Ni alloys and a binary Re-40 at%Ni alloy in vacuum for times up to 8640 ks. The microstructures of the Re-containing alloys which had been water-quenched after various heating times were observed and their concentration profiles for Re, Cr and Ni were measured using an electron probe micro-analyzer. The Re-Cr-Ni alloys consisted of the γ phase with either the σ or δ phase. It was found that concentration profiles of the γ phase became flat after short heat treatment, but longer times of up to 8640 ks were required to achieve the same effect for the σ and δ phases.
As the Cr contents increased (i.e., Re contents decreased) in the γ phase, the solubility limits of Ni in the σ phase tie-lined with the γ phase increased from 19 at%Ni to 24 at%Ni. The δ phase tie-lined with the γ phase(11.8 at%Re, 11.5 at%Cr, and 76.7 at%Ni) has 71.1 at%Re, 3.2 at%Cr, and 25.7 at%Ni. The Ni contents in the δ phase in a binary Re-Ni system are 30 and 35 at%Ni at 1573 and 1773 K, respectively. It was concluded that compositions of the γ phase tie-lined with the σ and δ phases coincided with those in the calculated and experimentally determined phase diagrams, respectively.
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Takeshige Takahashi, Makoto Kawabata, Takami Kai, Hisamichi Kimura, Ak ...2007 Volume 71 Issue 8 Pages 615-619
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSMethanol steam reforming has been carried out over catalysts prepared from glassy alloy containing a small amount of noble metals. When the alloy is treated at a temperature above the crystallization temperature, the reforming activity increases, whereas the original alloy does not have the similar activity. The reforming activity of the treated alloys increases with the decreasing content of noble metals down to 1 at%. The DSC (differential scanning calorimetry) analysis of the original alloy has revealed that the activity is related to the extent of supercooling and endothermic heat observed between the glassy temperature and crystallization temperature. Furthermore, the copper particle size of the treated alloy is related to the range of supercooling. These results indicate that the noble atoms are uniformly dispersed into the glassy Cu-Zr alloy by heating from the glass transition temperature to crystallization temperature. When the Cu-Zr alloy with a small amount of noble metals is oxidized over the crystallization temperature, the alloy changes to fine copper particles supported on zirconium oxide. A highly active reforming catalyst can be prepared from a glassy Cu-Zr alloy containing a small amount of noble metals.
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Manabu Tominaga, Satoru Toyooka, Hirofumi Kadono2007 Volume 71 Issue 8 Pages 620-628
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSDynamic processes of deformation in tensile experiments of plates of SUS304 stainless steels at low strain rates less than 10-4 s-1 were investigated by dynamic ESPI (DESPI). Full-field deformation behaviors could be observed continuously and totally as moving speckle correlation patterns from the start of a tensile test to fracture of a specimen. In later stage of plastic deformation, anomalous stress fluctuations or projections in a stress-strain curve were found. Correspondingly, characteristic X-shaped strain localizations which swept over the specimen repeatedly were found. Dependence of anomalous deformation behavior on strain rate was precisely examined. Changes in magnetic properties before and after passing the X-shaped strain localization were also investigated by the ferritescope. Propagating strain localization can be considered as the front of strain induced martensitic transformation.
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Hidekazu Sueyoshi, Shigeki Kakiuchi2007 Volume 71 Issue 8 Pages 629-635
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSThin Au film was prepared by sputtering and evaporation methods with a quartz substrate, followed by microwave irradiation in air (frequency of microwave: 2.45 GHz, incident flux of microwave: 563 W, irradiation time: 600 s). As a result, it was confirmed that microwave heating of thin Au film is feasible. The growth of crystalline and particles due to microwave heating was confirmed from AFM observation and XRD analysis.
Thin Au film is continuously heated during microwave irradiation, regardless of a preparation method of thin film. Microwave heating depends on the amount of microwave absorption on a thin Au film, which is related to the thickness and microstructure of the thin Au film. The rate of temperature rise depends on the ratio of a thickness to resistivity of thin Au film.
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Takashi Ando, Kenichiro Togoe, Yoshio Harada2007 Volume 71 Issue 8 Pages 636-640
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSIn order to improve the adhesion of 75 mass% Cr-Fe alloy plasma spray coatings, which provide sulfide corrosion resistance for the inner surface of NAS battery high-temperature type Al cylinders, the Al substrate temperature and the flattening behavior of the plasma spray particles were studied. Also, experiments were conducted to study how changes in the preheating temperature of the Al cylinder affected the spray coating's adhesion strength. The splat morphology of the spray particles changed significantly in relation to the preheating temperature of the Al substrate, from splash shaped to disk shaped as the preheating temperature increased. It was especially evident that the splat morphology of the particles changed sharply at over 433K, forming disk shaped splats with excellent adhesion to the substrate. A good correlation was found between the flatness of the spray particles and the adhesion strength of the coating formed by changing the preheating temperature of the Al cylinder. When the preheating temperature was set at over 433K, coating's with good adhesion strength were formed. It was therefore shown that by studying the flattening behavior of the plasma spray particles, an effective method could be found for improving the adhesion strength of the plasma spray coating.
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Fumio Kurosawa, Tomohiro Akimoto2007 Volume 71 Issue 8 Pages 641-645
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSIn order to understand the mechanism of increase in precipitation hardening, the critical size and lattice misfit of coherent precipitates in metallic materials were studied using a method newly developed by the author, which might be called “Different Lattice Mesh Overlapping Method”. The relationship among lattice arrangement, overlapping degree, critical size and lattice misfit of coherent precipitates were first made clear by this method. Then, it was shown that the critical size of coherent precipitates was determined by the overlapping area defined at a overlapping degree of 25%.
Since the overlapping area with overlapping degree of 25% is calculated as 56/X (lattice misfit ratio %), the present and previous results are concluded by the following formula.
Y(critical size/N)≒56/X(lattice misfit ratio/%)
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Yasuyuki Kitano, Masao Komatsu, Eishi Tanabe, Masashi Wada, Kouichi Ya ...2007 Volume 71 Issue 8 Pages 646-653
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSAs negative electrode materials with high capacity and long cycle lives for advanced Li-ion batteries, Si-based alloy films have been prepared on Cu-foil substrate by use of electron beam deposition method or magnetron-sputtering method at room temperature. In this study, nano-structures of the Si-based alloy films have been investigated by conventional and analytical transmission electron microscopy.
Experimental results are summarized as follows: (1) Si-based alloy films consist of a number of nano-fibers of 5 nm in diameter. Electron diffraction patterns from the films show halo. Crystallites are seldom found in high resolution images. (2) One-dimensional modulations of the constituents are formed in the range of 3.6 to 11 nm in the films. These nano-structures of the Si-based alloy films could relax the volume expansion of the Si during Li-insertion, causing the longer cycle lives than that of the Si film as the negative electrodes.
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Tokiko Nakagawa2007 Volume 71 Issue 8 Pages 654-660
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSElectrochemical characteristics of galvanic couples between iron and zinc•aluminum alloy were studied in a 3 mass% NaCl solution in a high oxygen pressure of 2 MPa at a high temperature of 423 K for 14.4 ks, and those were compared with that of a galvanic couple between iron and zinc. Both the galvanic corrosion potentials and currents of Fe-Zn couple, Fe-Zn•5Al couple and Fe-Zn•55Al couple remarkably changed after a certain period. Then, the polarities of the galvanic corrosion currents of Fe-Zn and Fe-Zn•5Al couples were reversed, indicating that iron is not protected any more. But the polarity of Fe-Zn•55Al couple was not changed although the current was decreased, indicating that iron is still protected. On the other hand, the polarity of Fe-Al couple was not changed throughout the experiment and iron was protected. When iron, zinc and aluminum were connected together at one point, dissolution current of zinc was large in the early stage and gradually became smaller, and the polarity of the current was finally reversed. On the other hand, the dissolution current of aluminum continued to increase. Therefore, aluminum resulted in protecting both iron and zinc from corrosion.
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Akira Heya, Naoto Matsuo, Tadashi Serikawa, Naoya Kawamoto2007 Volume 71 Issue 8 Pages 661-665
Published: 2007
Released on J-STAGE: August 01, 2007
JOURNAL FREE ACCESSA novel low-temperature crystallization method is proposed; the excimer laser annealing (ELA) of amorphous silicon (a-Si) with a hydrogen-modulation-doped layer (ELHMD). The effects of hydrogen on low-energy crystallization by conventional ELA and ELHMD were investigated. As the hydrogen concentration increases, the crystallinity of the polycrystalline silicon (poly-Si) prepared at a low energy density improves. It is considered that the nucleation is enhanced by the desorption energy of hydrogen from the Si-H2 bond during the Si melting. In addition, the film exfoliation by H2 burst can be suppressed using HMD a-Si film.
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