Papers by Author: Hidemi Kato

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Authors: Z.H. Chu, Hidemi Kato, Guo Qiang Xie, D.R. Yan, Guang Yin Yuan
Abstract: In recent years, bulk metallic glasses (BMGs) have received considerable attention due to their unique mechanical properties. However, the deformation of BMGs is highly localized in a few shear bands so that many of them exhibit poor plasticity. As such, more and more researchers have focused on improving the plasticity by in-situ or ex-situ introducing of nanoor micro-scale crystalline phases into the metallic glassy matrix in order to formation of multiple shear bands.
Authors: Hyung Seop Shin, Y.-J. Jung, Ki Hyun Kim, Jung Ho Ahn, Hidemi Kato, Akihisa Inoue
Authors: Hidemi Kato, Dmitri V. Louzguine-Luzgin, Akihisa Inoue, Hyoung Seop Kim, Sun Ig Hong
Authors: Guang Yin Yuan, Wen Jiang Ding, Kenji Amiya, Hidemi Kato, Akihisa Inoue
Abstract: Mg-8Zn-4Al-xY base alloys containing an icosahedral quasicrystal phase (i-phase) as a main strengthening phase were prepared by casting into a copper mould at moderate cooling rates. The Y addition was effective for decreasing the size of i-phase and the more homogeneousness of its dispersed state. The mechanical properties at room temperature were much superior to those of AZ91 alloy. The creep tests indicated a promising high temperature creep resistance of the quasicrystal-reinforced Mg-Zn-Al-Y cast alloy. The dislocation characteristic in crept specimens which containing i-phase and no i-phase was analyzed and strengthening mechanism was discussed.
Authors: Masuyuki Hasegawa, M. Takeuchi, D. Nagata, T. Wada, Hidemi Kato, Y. Yamaura, Akihisa Inoue
Abstract: The hydrogen-induced internal friction and mechanical strength of the Ti-rich Ti34Zr11Cu47Ni8 and (Ti34Zr11Cu47Ni8)98Si2 hydrogenated glassy alloys have been investigated. It is found that the tensile strength is more than 0.8 GPa at room temperature when the hydrogen content is below about 20 at% for both alloys. The frequency dependence of peak temperature of the hydrogen-induced internal friction of (Ti34Zr11Cu47Ni8)98Si2-17.3 at%H hydrogenated glassy alloys has been clarified. Activation energy and pre-exponential factor are estimated to be 0.35 eV and 1.3x10-12, respectively. Compared with these values with those of Zr40Cu49Al10Si1 hydrogenated glassy alloys which show an internal friction peak around 300 K at about 300 Hz, it is found that the activation energy is much smaller than that of the latter although the pre-exponential factor is almost the same. Considering their similar composition and different component (Al), it is suggested that the component Al of the latter glassy alloys is effective for the higher activation energy which results in the increase of the peak temperature.
Authors: Vladislav Yu. Zadorozhnyy, Xue Tao Shi, Takeshi Wada, Hidemi Kato, Dmitri V. Louzguine-Luzgin
Abstract: This paper describes investigation of the mechanical properties and biocompatibility of the Ti-based low-alloys minor alloying by the noble metal. It was found that almost all of the investigated Ti-based low-alloys, minor alloying by the noble metal, have relatively high biocompatibility, but found to be very brittle during tensile tests. The Ti94Au3Nb3 alloy exhibited relatively good tensile mechanical properties, having very good plasticity.
Authors: Sachiko Fujisawa, Kyosuke Yoshimi, Hidemi Kato, Kouichi Maruyama
Abstract: In this study, rapidly solidified Co-Sn-Ti and Co-Sn-Si alloys were investigated as candidate cathodic materials for lithium-ion batteries. (Co0.5Sn0.5)1-xTix (x=0.1, 0.2, 0.3, 0.4) and (Co0.5Sn0.5)0.9Si0.1 alloys were produced by Ar arc-melting. These alloys were further rapidly solidified into ribbons by the single-roll melt-spinning method. Constituent phases in the ribbons were identified by XRD, indicating that all of the alloys were composed of crystalline multi-phases with no amorphous phase. The microstructure of the ribbons was observed by SEM and TEM, and the chemical composition of constituent phases was analyzed by TEM-EDS. It is found from the SEM and TEM observations that the grain size of the constituent phases ranged from tens to hundreds nanometers due to the rapid solidification effect.
Authors: Dmitri V. Louzguine-Luzgin, Hidemi Kato, Akihisa Inoue
Authors: Albertus D. Setyawan, Hidemi Kato, Junji Saida, Akihisa Inoue
Abstract: A Zr65Al7.5Ni10Cu17.5-xPdx (x=0-17.5 at. %) alloy system is found to exhibit a different dependence of glass-forming ability (GFA) on atmosphere-pressure during mold casting process. High-Pd alloys (x=7.5-17.5) show a remarkable increase of critical size for glass formation (dc) as casting-atmosphere (Ar) pressure varies from vacuum to ambient. No significant change of dc, however, is observed in low-Pd alloys (x=0-5) despite the variation in atmosphere pressure. The origin of the phenomenon is unveiled by correlating the cooling characteristic during mold casting and on-cooling phase transformation characteristic of the alloy system.
Authors: Toshiya Matsusako, Takami Kai, Tsutomu Nakazato, Hisamichi Kimura, Takashi Goto, Hidemi Kato
Abstract: Amorphous Cu–Zr metallic alloys were studied as precursors to catalysts for methanol steam reforming to produce hydrogen. The alloy ribbons were prepared by single-roll rapid solidification, and the optimum pretreatment method and conditions were determined. The activity of the catalysts prepared by the improved pretreatment method was greater than that of previously prepared catalysts by two degrees of magnitude. The addition of a very small amount of Pt enhanced the activity without increasing CO formation.
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