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Volume 72, Issue 11
Displaying 1-12 of 12 articles from this issue
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Takashi Mitani, Tadashi Terazawa, Tomoyuki Hasegawa, Chihiro Watanabe, ...2008 Volume 72 Issue 11 Pages 847-851
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSApplication of a thermomechanical treatment to W-Mo type high-speed steel specimens enhanced the fatigue strength of the specimens. The fracture origin of as-prepared (AP) and thermomechanically-treated (TMT) specimens was large aggregates of about 12 μm, consisting of two or three M6C•MC carbides. Voids were produced by decohesion of the M6C/MC interfaces in M6C•MC carbides and a crack propagated between two voids in adjacent large M6C•MC carbides. The voids in the large carbides in the TMT specimens are less easily formed than in the AP specimens. This is attributable to greater stress concentration due to more inhomogeneous deformation around the carbides in the AP specimens than in the TMT specimens. A high density of tangled dislocations around the carbide brings about the inhomogeneous deformation around the carbide. The fatigue life of the TMT specimens is longer than that of the AP specimens because the nucleation of cracks in large M6C•MC carbide aggregates in the TMT specimens occurs less easily.
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Kazue Ichino Takahashi, Ryutaro Terakado, Jiro Nakamura, Ichiro Daigo, ...2008 Volume 72 Issue 11 Pages 852-855
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSWe developed a novel methodology to analyze world-scale stock-in-use of copper by using a nighttime light image. Radiance calibrated nighttime light imaged data (RCD) of the world has been assembled from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) by the National Geophysical Data Center. It has been recognized that the intensities of nighttime light are strongly associated with human settlement, such as population density and energy consumption. We assumed that wherever the light exists the electrical conducting material, such as copper should be used. The stock-in-use data of copper such as in Japan, North America, Australia and China were obtained from existing studies on material flow analysis. We analyzed the relationship between the light accumulation density and the amount of stock of copper in those countries. A significant correlation was found and the feasibility of this method was confirmed. We applied this method to analyze stock-in-use in other Asian countries. The in-use stock of copper was correlated with gross domestic product (GDP).
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Rongguang Wang, Takamichi Tokuyama, Mitsuo Kido2008 Volume 72 Issue 11 Pages 856-862
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSMicro-contaminants on SUS304 stainless steel were observed and confirmed by atomic force microscope, and micro-contaminant removal was carried out by ultraviolet-ozone (UV-O3) treatment. With an increase in the holding time in air, particle- and film-like micro-contaminants appeared and their amount increased on the specimen surface. Then, the amount of particle-like contaminants decreased and finally almost all the surface was covered by film-like contaminants. The amount of micro-contaminants on the specimen surface decreased with an increase in UV-O3 treatment time, with extensive removal of the organic substance in the contaminants but leaving part of the contained water in the contaminants. The micro-contaminants slowly re-adhered on the treated surface when the surface was re-exposed to air, with a long period of more than 172 ks for the recovery to the state before the UV-O3 treatment. The surface for macro-droplets after the UV-O3 treatment became hydrophilic, while no large change of the wettability for micro-droplets on the same surface can be observed.
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Nahoko Sugioka, Masahiro Kitada2008 Volume 72 Issue 11 Pages 863-867
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSThe metallic compound of the yellow dyestuff used for touzan cotton fabric imported in the late Edo period has been investigated. Cotton threads dyed three colors, indigo blue, shellac dark red and unknown yellow, are used in the specimen. The color is analyzed with a spectrophotometer. The microstructures are observed by SEM. The composition and crystal structure are analyzed by EDX and XRD, respectively. The average diameter and length of the cotton thread used are 20 μm and 27 mm, respectively. From the size, the cotton is thought to be made in a country in Southeast Asia. Many particles 1-2 μm in length and 0.2-0.7 μm in width are observed on the thread surface. The absorption edges at 536 nm (2.3 eV) and 730 nm (1.7 eV) are observed in the reflectance spectrum. The yellow color is determined by the edge at 536 nm, and the dyestuff material is a semiconductor having the band gap of 2.3 eV. Chromium (Cr) and Lead (Pb) species are detected from the surface and the inside of the cotton fiber. The metallic compound, PbCrO4, is detected by XRD; this compound is called chrome-yellow and was developed in Europe at the beginning of the 19th century.
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Preparation of Ni Aluminide/Ni-Hf Alloy Coating by Electrodeposition and Cyclic Oxidation ResistanceKatsuya Uemura, Michihisa Fukumoto, Motoi Hara, Toshio Narita2008 Volume 72 Issue 11 Pages 868-874
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSThe formation of a bi-layer coating consisting of Ni aluminide/Ni-Hf alloy on a Ni substrate was attempted by the electrodeposition of Hf on the Ni substrate, followed by the electrodeposition of Ni and Al. Before the formation of this coating, it was confirmed by the diffusion couple test that the Ni-Hf alloy consisting of Ni7Hf2 acted as a diffusion barrier of aluminum. Upon forming this bi-layer coating, Hf and Al were deposited by molten salt electrolysis at 1023 K. The cyclic oxidation resistance for the Ni covered with this coating was then evaluated in air at 1373 K. The electrodeposition of Hf on the Ni substrate led to the formation of a layer consisting of the Ni-Hf alloy. The electrodeposition of Ni and Al on the Ni-Hf alloy layer led to the formation of a layer consisting of Ni2Al3 as a surface layer. The cyclic oxidation test showed that the mass gain due to oxidation for the sample covered with the bi-layer coating consisting of the Ni2Al3/Ni-Hf alloy was lower than that for the sample covered with a single-layer coating consisting of Ni2Al3. The analytical results of a cross-section of the sample covered with the bi-layer coating after the 5-cycle oxidation test showed that the chemical composition of the Ni-Hf alloy layer was uniform, and this layer consisted of Ni7Hf2. Furthermore, it was confirmed that the aluminum concentration in the Ni aluminide layer was constant at about 40 at%, and the Ni-Hf alloy layer depressed the diffusion of aluminum from the Ni aluminide layer to the Ni substrate. For the sample covered with the bi-layer coating after the 100-cycle oxidation test, the aluminum concentration in the Ni aluminide layer was constant at about 20 at%, and a protective alumina scale containing small amounts of hafnium oxide was formed. On the contrary, for the sample covered with the single-layer coating consisting of Ni2Al3, the aluminum concentration in the Ni aluminide layer was only about 10 at%, and an internal oxide was largely formed in the Ni aluminide layer.
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Yoshimi Sato, Naoyuki Nomura, Akihiko Chiba2008 Volume 72 Issue 11 Pages 875-880
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSThe gas atomized Co-29Cr-6Mo alloy powder was hot-pressed in Ar, Ar and N2 (Ar+N2), and N2 atmosphere at 1273 K and 80 MPa for 7.2 ks. Nitrogen content in the compacts can be controlled by the mixture ratio of Ar and N2 gases and the compacts contains nitrogen as high as 0.81 mass%. Microstructure and constituent phase of the compacts depends on the nitrogen content. In the compacts containing nitrogen less than 0.2%, the γ(fcc) ε (hcp) and σ phases coexist in the compacts. The volume fraction of σ phase decreases with increasing nitrogen content up to 0.2%. The γ phase is dominantly confirmed in the compacts with nitrogen content of approximately 0.2%. In the compacts containing nitrogen over 0.2%, Cr2N phases in addition to the γ and ε phases are detected in the compacts. This result suggests nitrogen suppress the σ phases formation and stabilize γ phase in the Co-29Cr-6Mo alloy. When the Co-29Cr-6Mo alloy compacts are hot-pressed with Cr2N powder as a nitrogen source, the σ and nitrides coexist and the microstructure is inhomogeneous. Therefore, it is found that controlling the mixture ratio of Ar and N2 gases during hot-pressing is effective methods to distribute nitrogen uniformly in the Co-Cr-Mo alloy compacts.
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Yasuyuki Kitano, Tetsuya Ozaki, Manabu Kanemoto, Masao Komatsu, Shigeo ...2008 Volume 72 Issue 11 Pages 881-885
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSIn order to improve the hydrogen absorption properties of the layer structure appearing at the nickel rich side of La-Mg-Ni alloy, appropriate amounts of Ni were replaced by some elemental atoms, Mn, Co and Al. The La0.8Mg0.2Ni3.4-xCo0.3(MnAl)x (0<x<0.4) alloy system was prepared and crystal structures were investigated by electron microscopy. The atomic concentration ratio of (LaMg) to the other atoms was 3.7 in this system. The Pr5Co19-type structure (5:19H-structure) and the Ce5Co19-type structure (5:19R-structure) were found in this alloy system. Electron micrographs of these structures are presented in this paper. Structure analysis of the complex layer structure is demonstrated by careful observation of the electron diffraction pattern.
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Norihito Sakaguchi, Seiichi Watanabe, Hideki Ichinose2008 Volume 72 Issue 11 Pages 886-891
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESS{112} Σ3 CSL grain boundary in silicon was investigated by high-resolution transmission electron microscopy (HRTEM) and ab-initio calculation. A {112} Σ3 CSL boundary consisted of two segments which differed in atomic structure. The segment near the corner and connected to {111} Σ3 CSL boundary showed symmetric structure and the other long segment, which was the distant and away from the corner, showed asymmetric structure. It was shown that the asymmetric structure is more stable than the symmetric one. In the symmetric segment a 5-fold coordinated atom presented, which elevated the structure energy of the boundary and produced a new state in the band gap.
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Keisuke Takata, Keisuke Iwata, Yoshio Tyler, Akira Tonegawa, Yoshitake ...2008 Volume 72 Issue 11 Pages 892-896
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSEffects of homogeneous irradiation of electron beam on bending strength were studied for alkali free glass. The irradiation, which was one of short-time treatments, enhanced the bending elasticity, as well as increased the bending strength, although the irradiation doesn't largely change the fracture strain. Enhancements of bending elasticity and bending strength can be explained by stabilization of atomic distance induced by nano-scopic stress relaxation, which was probably generated by optimum distribution of dangling bonds.
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Masato Yamashita, Satoshi Hanaki, Hitoshi Uchida, Kazuki Fujiwara, Nob ...2008 Volume 72 Issue 11 Pages 897-902
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSWe have examined fatigue crack propagation behavior in the [ferrite/bainite]-Hybrid materials with different hardness under a constant stress intensity factor range. It was found that crack propagation in the ferrite phase decelerated with reaching to the [ferrite/bainite]-interface, probably due to supression of plastic deformation at the crack tip. This suppression tendency of the crack propagation became higher when hardness difference between ferrite and bainite was larger. In the case with the highest hardness difference, fatigue crack did not pass through the [ferrite/bainite]-interface. Lower crack propagation rate was also found in the bainite which showed higher work softening due to crack propagation.
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Takaaki Wajima, Yasuyuki Ikegami2008 Volume 72 Issue 11 Pages 903-910
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSThe leaching of potentially toxic elements or the generation of acidity from mine waste often creates significant environmental pollution. A great deal of research has been undertaken to find an effective solution to the problem of acid mine drainage. An attractive solution has been proposed, not only efficient but also economical, as it uses another waste material. The objective of this study was to investigate the feasibility of stabilizing acidic mine waste using alkaline industrial waste, paper sludge ash (PSA), produced by the pulp and paper industry, under laboratory conditions. By mixing mine waste with (PSA) (the weight ratio of mine waste to (PSA) is 10:4), the eluted solution became neutral, and the concentrations of almost all metals dropped below the Japanese effluent standard. The inhibition of acid mine drainage with addition of PSA is sustainable. Although Radish sprouts did not grow on mine waste, they could be grown on the waste mixed with PSA. These results suggest that it is possible to use PSA for the remediation of a mine waste site.
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Kazuhiro Hasezaki, Gen-yo Kaneko, Akifumi Nakashita, Hideaki Kakuda2008 Volume 72 Issue 11 Pages 911-914
Published: 2008
Released on J-STAGE: November 01, 2008
JOURNAL FREE ACCESSCoal fly ash and NiCr alloy powder stacked layer by layer (FGM) were prepared by spark plasma sintering. The coal fly ash was produced by Misumi coal thermal power station (Chugoku Electric Power Co., Inc.), and 80 mass% nickel and 20 mass% chromium (Fukuda Metal Foil & Powder Co., Ltd) were used as source materials. The sintering was done at 1000°C in a graphite die. X-ray diffraction patterns of the sintered coal fly ash materials indicated that the mullite (3Al2O3•2SiO2) and silica (SiO2) phases were predominant. Direct joining of coal fly ash and NiCr causes a fracture at the interface due to a mismatch of thermal expansion. Cracks in the FGMs were observed between the two layers when the difference of linear thermal expansion coefficient (α) was over 4.2×10-6 K-1, while no cracks were detected in stable FGMs when the difference was less than 4.0×10-6 K-1.
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