Daido Institute of Technology

Nagoya, Japan

Daido Institute of Technology

Nagoya, Japan
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Okouchi H.,Fukuda Metal Foil and Powder Co. | Okouchi H.,Kumamoto University | Seki Y.,Kobelco Research Institute | Sekigawa T.,Mitsubishi Group | And 2 more authors.
Materials Science Forum | Year: 2010

Interests in magnesium alloys increase as eco-material for its lightweight, and many investigations have been carried out on the development of manufacturing processes and alloy development. In 2001, Mg97Zn 1Y2 (at%) alloy with a tensile yield strength of 610 MPa and an elongation of more than 5 % has been developed by rapidly solidified powder metallurgy (RS P/M) processing. The developed alloy was characterized by a novel phase with long period stacking ordered (LPSO) structure. Recently, we have investigated new compositions for LPSO RS P/M Mg-Zn-Y-X alloys in order to improve the corrosion resistance of the RS P/M Mg97Zn 1Y2 alloy with maintaining the superior mechanical properties. Consequently, we have developed a RS P/M Mg96.7Zn 0.85Y2Al0.45 alloy with high strength and high corrosion resistance. The RS P/M Mg96.7Zn0.85Y 2Al0.45 alloy contained the LPSO phase and exhibited a tensile strength of 525 MPa, an elongation of 9 % and a fatigue strength of 325 MPa, which were similar to those of the RS P/M Mg97Zn 1Y2 alloy. However, the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al0.45 alloy was 1.5 times that of the RS P/M Mg97Zn1Y2 alloy. The specific tensile yield strength, the specific fatigue strength and the corrosion resistance of the RS P/M Mg96.7Zn0.85Y2Al 0.45 alloy were about 1.7 times, 1.8 times, and twice those of extra-super-duralumin (7075-T6 or 7075-T73), respectively. © (2010) Trans Tech Publications.

Tagawa T.,Osaka University | Kayamori Y.,Nippon Steel & Sumitomo Metal Corporation | Hira H.,Daido Institute of Technology
Engineering Fracture Mechanics | Year: 2010

The statistical scatter of fracture toughness in the ductile-brittle transition temperature range was experimentally examined on a 500. MPa class low carbon steel. Fracture toughness tests were replicatedly performed at -60 °C, -20 °C and -10 °C. The tests at -60 °C resulted in a single modal Weibull distribution with a shape parameter of 4 for the critical stress intensity factor converted from J-integral, whereas the Weibull distributions of the critical stress intensity factor at -20 °C and -10 °C showed a bilinear pattern with an elbow point, which caused a wider scatter than that at -60 °C. Such scatter transition behavior was discussed with reference to stable crack initiation. A model of the statistical scatter transition has been proposed in this work and the model reasonably explains the experimental results. © 2010 Elsevier Ltd.

Hosokawa T.,Tokyo Denki University | Kaneda T.,Tokyo Denki University | Takahashi T.,Sony Corporation | Yamamoto T.,Nikon Corporation | And 2 more authors.
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2011

The dc breakdown characteristics in the gap with the thin dielectric sheet under atmospheric air were investigated experimentally. The breakdown phenomna were divided into three patterns by current and discharge light (photon) waveforms. The first pattern consisted of a single waveform as a primary pulse. The second pattern consisted of multiple secondary pulses as the successors of the primary pulse. The third pattern was a developing process from the second pattern to the breakdown of the sheet as a final stage. The breakdown voltage of the sheet was irregular even under the same experimental conditions, and its value increased with the sheet thickness. On the other hand, the breakdown voltage in the complex gap consisting of the thin sheet and air gap became higher than that of the thin sheet, and its maximum value reached the breakdown voltage in the air gap. These phenomena and the breakdown mechanism for each pattern were analyzed by the electric field distribution between the electrodes. The breakdown models in the gap with the thin sheet and the complex gap were proposed by comparing the experimental results with the breakdown mechanisms. © 2006 IEEE.

Yamamoto N.,Nagoya University | Jin X.G.,Nagoya University | Mano A.,Nagoya University | Ujihara T.,Nagoya University | And 8 more authors.
Journal of Physics: Conference Series | Year: 2011

Recently, we have developed a transmission-type polarized electron sources (PES)s for the generation of a high brightness beam. The developed PES can applied the extraction voltage of 20 kV at 4 mm electrode-gap and enables to realize the source beam radius of a few micro meter. As the results of prototype gun experiments, the brightness of ∼2 x 107 A.cm -2.sr-1 and a charge density lifetime of 1.8 x 10 8 C.cm-2 were obtained. A maximum polarization of ∼90 % and quantum efficiency of 0.09 % was achieved simultaneously using the transmission photocathode with GaAs-GaAsP strained superlattice layers. Up to now, another two electron gun was manufactured, and those mechanical designs are almost same as that of the prototype. The prototype gun and the second gun have been already operated for the photocathode R&D and for the Spin-LEEM application, respectively. In the near future, further experiments are prepared by using the third gun.

Takasaki M.,Toray Industries Inc | Nakagawa Y.,Toray Industries Inc | Sakiyama Y.,Toray Industries Inc | Tanabe K.,Toray Industries Inc | And 5 more authors.
Journal of the Electrochemical Society | Year: 2013

Operation tests were applied to fuel cell with perfluorosulfonic acid (PFSA) polymer for membranes and electrodes. Degradation of PFSA polymer in catalyst layers after the tests was investigated using 19F NMR. As the decomposition products, six kinds of the side-chain fragments were acquired from the water and the methanol extracts, and the each weight of the fragment was acquired. The side-chain fragments indicate that side-chain scission occurs at two positions in the side-chain. Moreover, reduction of relative equivalent weight for all PFSA polymer (EW*all) and amounts of PFSA polymer in catalyst layer after the tests suggests that main-chain scission occurs. Hydrogen peroxide vapor (HPV) exposure tests were applied to PFSA polymer membranes. PFSA polymer degradation after the tests was investigated using ion chromatography and total organic carbon analysis for trap water, and using 19FNMR for water/methanol extracts of membranes. Decomposition products other than fluoride ion accounted for a significant portion of degradation weight loss, and their generation rates were not proportional to fluoride ion release rate (FRR). The differences between the results of FRR and other decomposition product analysis strongly suggest the presence of two or more decomposition mechanisms in PFSA degradation. © 2013 The Electrochemical Society.

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