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Shibata, Motoki*; Takenaka, Mikihito*; Motokawa, Ryuhei; Kumada, Takayuki; Ueda, Yuki; Miyazaki, Tsukasa*; Nakanishi, Yohei*; Abe, Jun*; Iwase, Hiroki*; Shibayama, Mitsuhiro*; et al.
Polymer, 340, p.129203_1 - 129203_7, 2025/12
Times Cited Count：0 Percentile：0.00(Polymer Science)Suzuki, Kenji*; Miura, Yasufumi*; Toyokawa, Hidenori*; Shiro, Ayumi*; Shobu, Takahisa; Morooka, Satoshi; Shibayama, Yuki
Quantum Beam Science (Internet), 9(2), p.15_1 - 15_15, 2025/06
Hojo, Tomohiko*; Koyama, Motomichi*; Kumai, Bakuya*; Zhou, Y.*; Shibayama, Yuki; Shiro, Ayumi*; Shobu, Takahisa; Saito, Hiroyuki*; Ajita, Saya*; Akiyama, Eiji*
ISIJ International, 65(2), p.284 - 296, 2025/02
Times Cited Count：0 Percentile：0.00(Metallurgy & Metallurgical Engineering)Shibayama, Yuki; Hojo, Tomohiko*; Koyama, Motomichi*; Akiyama, Eiji*
International Journal of Hydrogen Energy, 88, p.1010 - 1016, 2024/10
Times Cited Count：10 Percentile：66.01(Chemistry, Physical)Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Furuya, Kazuyuki*; Ando, Masami*; Kamada, Takaharu*; Ishida, Taku*; Makimura, Shunsuke*
Materials Characterization, 211, p.113881_1 - 113881_10, 2024/05
Times Cited Count：12 Percentile：84.87(Materials Science, Multidisciplinary)The microstructures and mechanical properties of bcc iron-based high entropy alloy (HEA) Fe-20Mn-15Cr-10V-10Al-2.5C (in at%) without Co and Ni elements have been investigated for applications in fields such as accelerator-target system, nuclear reactors and magnetic motors in aircraft and automobiles. This alloy was normalized at 1150
C for 2 hr and then water quenched, and it was heated at 800C for 10 min and then water quenched. The alloy had a bcc-phase and vanadium carbides with 2-3 
m arranging along grain boundaries, and the Vickers hardness was 520 Hv, harder than pure tungsten. Magnetic domain structure was observed in phase differential contrast method in scanning transmission electron microscope, and the micro-size magnetic domains in grain and sub micro size ones were formed near surface, and it is attractive to the magnetic motor field application. Element distribution in nano scale (20 nm) was observed in matrix, and the presence of crystal lattice disorder in the atomic level region was seen. Very high performance for radiation resistance was confirmed with no irradiation hardening at 300 and 500 C to 1 dpa. It can be speculated that this is due to irradiation-induced nanoscale concentration changes and strain relaxation in the HEA. These properties are very attractive in application of several fields.
Sekine, Yurina; Nankawa, Takuya; Sugita, Tsuyoshi; Nagakawa, Yoshiyasu*; Shibayama, Yuki; Motokawa, Ryuhei; Ikeda-Fukazawa, Tomoko*
Nanoscale, 16(19), p.9400 - 9405, 2024/05
Times Cited Count：5 Percentile：56.05(Chemistry, Multidisciplinary)A tough carboxymethyl cellulose nanofiber (CMF)/ zirconium (Zr) hydrogel was obtained by freeze cross-linking method. The hydrogel was prepared by adding HCl solution containing Zr to frozen CMF and thawing it. The hydrogel showed high adsorptivity for fluoride. This simple gelation method provides useful insight for developing hydrogel-metal complexes.
Sekine, Yurina; Nankawa, Takuya; Hiroi, Kosuke; Oba, Yojiro*; Nagakawa, Yoshiyasu*; Sugita, Tsuyoshi; Shibayama, Yuki; Ikeda-Fukazawa, Tomoko*
Carbohydrate Polymers, 327, p.121538_1 - 121538_11, 2024/03
Times Cited Count：20 Percentile：91.36(Chemistry, Applied)We describe non-toxic, tough nanocellulose (NC) hydrogels formed from chemically unmodified NC by cellulose crystalline transformation and subsequent freeze cross-linking reaction. Using low-concentration NaOH and freezing together induced the crystalline transformation of NC from cellulose I to II via freeze concentration. After the crystalline transformation, cross-linking between the NC and CA in the freeze concentration layer (FCL) provided a strong NC network structure, forming NC hydrogels with high mechanical strength. The freeze-cross-linked NC hydrogel easily retained powder adsorbents in its inner space by mixing the NC-NaOH sol and the powder, and the hydrogel showed high removal efficiency for heavy metals. The results highlight the versatility of chemically unmodified celluloses in developing functional materials, suggest possible practical applications.
Hojo, Tomohiko*; Nagasaka, Akihiko*; Kobayashi, Junya*; Shibayama, Yuki; Akiyama, Eiji*
Metals, 14(3), p.346_1 - 346_19, 2024/03
Times Cited Count：1 Percentile：12.38(Materials Science, Multidisciplinary)Chiba, Shuya*; Koyama, Motomichi*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki; Varanasi, R. S.*; Akiyama, Eiji*
ISIJ International, 64(4), p.706 - 713, 2024/02
Times Cited Count：2 Percentile：24.60(Metallurgy & Metallurgical Engineering)Matsuno, Takashi*; Fujita, Taiki*; Matsuda, Tomoko*; Shibayama, Yuki; Hojo, Tomohiko*; Watanabe, Ikumu*
Journal of Materials Processing Technology, 322, p.118174_1 - 118174_16, 2023/12
Times Cited Count：13 Percentile：68.24(Engineering, Industrial)The impact of high stress triaxiality on work hardening in transformation-induced plasticity (TRIP) steel has been widely acknowledged, particularly through measurements of the austenite fraction. Understanding this TRIP behavior is crucial for predicting material fracture in press-forming processes. However, the actual flow stresses under high-stress-triaxiality conditions remain largely undetermined. To address this gap, we developed a new tensile testing method using tiny notched round bars to investigate stress-triaxiality-induced work hardening in TRIP steels. The specimens were analyzed using two-dimensional micrometry to allow finite element analyses to identify the flow stress. Additionally, we conducted in situ tensile tests in which their crystal lattice stresses were monitored using synchrotron X-ray diffraction (XRD) to realize mechanism analyses of the unexpected work-hardening behavior identified by the developed tensile testing method. Our combined approach revealed a mutual, unstable increase in the flow stress and stress triaxiality in the TRIP-aided bainitic ferrite steel, which reduced the hardening exponent coefficients and thus induced a higher stress triaxiality. In contrast, the TRIP-aided martensitic steel exhibited a weakening behavior, characterized by a significant decrease in the hardening exponent coefficients in the case of the sharpest notch. XRD analyses showed that microstructural heterogeneity led to an extraordinarily high hydrostatic stress in the austenite phase, accounting for these contrasting behaviors. This finding challenges the established consensus on TRIP steels and suggests the need for a revised framework for their application in press-forming, taking into account stress-triaxiality conditions.
Wakai, Eiichi; Noto, Hiroyuki*; Shibayama, Tamaki*; Furuya, Kazuyuki*; Wakui, Takashi; Ando, Masami*; Makimura, Shunsuke*; Ishida, Taku*
Science Talks (Internet), 8, p.100278_1 - 100278_4, 2023/12
High entropy alloys tend to combine high strength with good ductility due to their inherent properties. This material is considered as a promising new material not only for higher-performance future general industrial applications, but also for increasing the durability and range of application of radiation-affected equipment in nuclear and radiation environments, and has been rapidly gaining attention in recent years. In this study, two types of high-entropy alloys (Fe-Mn-V-Cr-Al-C and Fe-Si-W-Cr-V) composed of low-radioactive elements (without Ni and Co) were prepared and their basic properties were evaluated for application as new functional materials to be used under radiation in high-energy accelerator target system components, nuclear reactors, fusion reactors, etc. and their basic properties were evaluated. The two materials under development in this study have unique properties in the following respects. The former is expected to be developed as a basic research for high-power motor materials as a new structural material and magnetic properties sharing the features of high strength and low radiation. On the other hand, the latter is expected to be applied as a new functional material in new engineering fields by mixing tungsten, which has the highest melting point among metallic elements, with vanadium, which has a considerably higher melting point, to raise the melting point of the alloy and to design an alloy with high strength.
Shibata, Motoki*; Nakanishi, Yohei*; Abe, Jun*; Arima, Hiroshi*; Iwase, Hiroki*; Shibayama, Mitsuhiro*; Motokawa, Ryuhei; Kumada, Takayuki; Takata, Shinichi; Yamamoto, Katsuhiro*; et al.
Polymer Journal, 55(11), p.1165 - 1170, 2023/11
Times Cited Count：6 Percentile：35.52(Polymer Science)Hojo, Tomohiko*; Shibayama, Yuki; Ajita, Saya*; Koyama, Motomichi*; Akiyama, Eiji*
Materia, 61(7), p.413 - 418, 2022/07
no abstracts in English
Hojo, Tomohiko*; Koyama, Motomichi*; Kumai, Bakuya*; Shibayama, Yuki; Shiro, Ayumi*; Shobu, Takahisa; Saito, Hiroyuki*; Ajito, Saya*; Akiyama, Eiji*
Scripta Materialia, 210, p.114463_1 - 114463_5, 2022/03
Times Cited Count：25 Percentile：81.62(Nanoscience & Nanotechnology)Izumi, Atsushi*; Shudo, Yasuyuki*; Shibayama, Mitsuhiro*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki
Langmuir, 37(47), p.13867 - 13872, 2021/11
Times Cited Count：3 Percentile：11.15(Chemistry, Multidisciplinary)Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
Tetsu To Hagane, 107(9), p.760 - 768, 2021/09
Times Cited Count：0 Percentile：0.00(Metallurgy & Metallurgical Engineering)no abstracts in English
Nishimura, Hayato*; Hojo, Tomohiko*; Ajita, Saya*; Shibayama, Yuki*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Akiyama, Eiji*
ISIJ International, 61(4), p.1170 - 1178, 2021/04
Times Cited Count：12 Percentile：48.53(Metallurgy & Metallurgical Engineering)Shibayama, Yuki; Hojo, Tomohiko*; Koyama, Motomichi*; Saito, Hiroyuki*; Shiro, Ayumi*; Yasuda, Ryo*; Shobu, Takahisa; Matsuno, Takashi*; Akiyama, Eiji*
ISIJ International, 61(4), p.1322 - 1329, 2021/04
Times Cited Count：9 Percentile：38.61(Metallurgy & Metallurgical Engineering)Izumi, Atsushi*; Shudo, Yasuyuki*; Shibayama, Mitsuhiro*; Yoshida, Tessei*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki
Macromolecules, 53(10), p.4082 - 4089, 2020/05
Times Cited Count：10 Percentile：29.66(Polymer Science)Shudo, Yasuyuki*; Izumi, Atsushi*; Hagita, Katsumi*; Yamada, Takeshi*; Shibata, Kaoru; Shibayama, Mitsuhiro*
Macromolecules, 51(16), p.6334 - 6343, 2018/08
Times Cited Count：17 Percentile：47.34(Polymer Science)