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Hong, Z.*; Ahmed, Z.*; Pellegrini, M.*; Yamano, Hidemasa; Erkan, N.*; Sharma, A. K.*; Okamoto, Koji*
Progress in Nuclear Energy, 171, p.105160_1 - 105160_13, 2024/06
In this study, it is found that the eutectic reaction between BC powder and stainless steel (SS) is considerably more rapid than that between the BC pellet and SS. The derived reaction rate constant values for powder and pellet cases are consistently based on the reference values. Also, a composition analysis using SEM/EDS was conducted for the detailed microstructures of the powder and pellet samples. In the powder case, only one thick layer is found as the reaction layer consisting of (Fe, Cr)B precipitate, including BC powder. In the pellet case, two layers are found in the reaction layer.
Chong, Y.*; Gholizadeh, R.*; Guo, B.*; Tsuru, Tomohito; Zhao, G.*; Yoshida, Shuhei*; Mitsuhara, Masatoshi*; Godfrey, A.*; Tsuji, Nobuhiro*
Acta Materialia, 257, p.119165_1 - 119165_14, 2023/09
Times Cited Count:4 Percentile:84.87(Materials Science, Multidisciplinary)Metastable titanium alloys possess excellent strain-hardening capability, but suffer from a low yield strength. As a result, numerous attempts have been made to strengthen this important structural material in the last decade. Here, we explore the contributions of grain refinement and interstitial additions in raising the yield strength of a Ti-12Mo (wt.%) metastable titanium alloy. Surprisingly, rather than strengthening the material, grain refinement actually lowers the ultimate tensile strength in this alloy. This unexpected and anomalous behavior is attributed to a significant enhancement in strain-induced martensite phase transformation, where in-situ synchrotron X-ray diffraction analysis reveals, for the first time, that this phase is much softer than the parent phase. Instead, a combination of both oxygen addition and grain refinement is found to realize an unprecedented strength-ductility synergy in a Ti-12Mo-0.3O (wt.%) alloy. The advantageous effect of oxygen solutes in this ternary alloy is twofold. Firstly, solute oxygen largely suppresses strain-induced transformation to the martensite phase, even in a fine-grained microstructure, thus avoiding the softening effect of excessive amounts of martensite. Secondly, oxygen solutes readily segregate to twin boundaries, as revealed by atom probe tomography. This restricts the growth of deformation twins, thereby promoting more extensive twin nucleation, leading to enhanced microstructural refinement. The insights from our work provide a cost-effective rationale for the design of strong yet tough metastable titanium alloys, with significant implications for more widespread use of this high strength-to-weight structural material.
Chong, Y.*; Gholizadeh, R.*; Tsuru, Tomohito; Zhang, R.*; Inoue, Koji*; Gao, W.*; Godfrey, A.*; Mitsuhara, Masatoshi*; Morris, J. W. Jr.*; Minor, A. M.*; et al.
Nature Communications (Internet), 14, p.404_1 - 404_11, 2023/02
Times Cited Count:6 Percentile:93.59(Multidisciplinary Sciences)Interstitial oxygen embrittles titanium, particularly at cryogenic temperatures, which necessitates a stringent control of oxygen content in fabricating titanium and its alloys. Here, we propose a structural strategy, via grain refinement, to alleviate this problem. Compared to a coarse-grained counterpart that is extremely brittle at 77K, the uniform elongation of an ultrafine-grained (UFG) microstructure (grain size 2.0 m) in Ti-0.3wt.%O was successfully increased by an order of magnitude, maintaining an ultrahigh yield strength inherent to the UFG microstructure. This unique strength-ductility synergy in UFG Ti-0.3wt.%O was achieved via the combined effects of diluted grain boundary segregation of oxygen that helps to improve the grain boundary cohesive energy and enhanced dislocation activities that contribute to the excellent strain hardening ability. The present strategy could not only boost the potential applications of high strength Ti-O alloys at low temperatures, but could also be applied to other alloy systems, where interstitial solution hardening results into an undesirable loss of ductility.
Guo, B.*; Mao, W.; Chong, Y.*; Shibata, Akinobu*; Harjo, S.; Gong, W.; Chen, H.*; Jonas, J. J.*; Tsuji, Nobuhiro*
Acta Materialia, 242, p.118427_1 - 118427_11, 2023/01
Times Cited Count:5 Percentile:64.46(Materials Science, Multidisciplinary)Hong, Z.*; Pellegrini, M.*; Erkan, N.*; Liao, H.*; Yang, H.*; Yamano, Hidemasa; Okamoto, Koji*
Annals of Nuclear Energy, 180, p.109462_1 - 109462_9, 2023/01
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)A series of experiments were conducted using BC material and SUS304 tubes as a simulant of the real control rods. Reaction rate constant data in the 1450K-1500K range were obtained, and are consistent with the reference values. The reaction layer microstructure observation and the associated chemical composition analysis were also carried onto the experiment samples.
Chong, Y.*; Tsuru, Tomohito; Guo, B.*; Gholizadeh, R.*; Inoue, Koji*; Tsuji, Nobuhiro*
Acta Materialia, 240, p.118356_1 - 118356_15, 2022/11
Times Cited Count:15 Percentile:92.67(Materials Science, Multidisciplinary)In this study, we systematically investigated the influences of nitrogen content and grain size on the tensile properties and deformation behaviors of titanium at room temperature. By high-pressure torsion and annealing, we obtained ultrafine-grained (UFG) Ti-0.3wt.%N alloy with a fully recrystallized microstructure, which combined an unprecedented synergy of ultrahigh yield strength (1.04 GPa) and large uniform elongation (10%). The hardening and strain-hardening mechanisms of Ti-0.3wt.%N alloy were comprehensively studied via deformation substructure observation and first-principles calculations. It is revealed that the contributions of nitrogen to the excellent strength/ductility balance in UFG Ti-0.3wt.%N were twofold. On one hand, nitrogen atoms inside the grains strongly impeded the motion of dislocations on prismatic plane due the shuffling of nitrogen from octahedral to hexahedral site, giving rise to a six-fold increase in the friction stress than pure Ti. Moreover, the greatly reduced stacking fault energy difference between prismatic and pyramidal planes in Ti-0.3wt.%N alloy facilitated an easier activation of dislocations, which contributed to an enhanced strain-hardening rate. On the other hand, some nitrogen atoms segregated near the grain boundaries, a phenomenon discovered in -titanium for the first time. These segregated nitrogen atoms served as an additional contributor to the yield strength of UFG Ti-0.3wt.%N, by raising the barrier against dislocation slip transfer between grains. Our experimental and theoretical calculation work provide insights for the design of affordable high strength titanium without a large sacrifice of ductility, shedding lights on a more widespread use of this high strength to weight material.
Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Morita, Koji*; Nakamura, Kinya*; Fukai, Hirofumi*; et al.
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
This paper describes the project overview and progress of experimental and analytical studies conducted until 2020. Specific results in this paper are the measurement of the eutectic reaction rates and the validation of physical model describing the eutectic reaction in the analysis code through the numerical analysis of the BC-SS eutectic reaction rate experiments in which a BC pellet was placed in a SS crucible.
Yu, Y.*; Yang, C.*; Baggioli, M.*; Phillips, A. E.*; Zaccone, A.*; Zhang, L.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Yu, D.*; Hong, L.*
Nature Communications (Internet), 13, p.3649_1 - 3649_10, 2022/06
Times Cited Count:8 Percentile:81.66(Multidisciplinary Sciences)Kim, Y. S.*; Chae, H.*; Huang, E.-W.*; Jain, J.*; Harjo, S.; Kawasaki, Takuro; Hong, S. I.*; Lee, S. Y.*
Materials, 15(4), p.1312_1 - 1312_11, 2022/02
Times Cited Count:0 Percentile:0(Chemistry, Physical)Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Health Physics, 121(6), p.613 - 620, 2021/12
Times Cited Count:0 Percentile:0.01(Environmental Sciences)According to the implementing arrangement between JAEA (Japan Atomic Energy Agency) and KAERI (Korea Atomic Energy Research Institute) in the field of the radiation protection and environmental radiation monitoring, the joint measurement has been conducted to assess the radioactive cesium deposition in the ground around the Fukushima Daiichi Nuclear Power Plants (FDNPP). First, mobile gamma-ray spectrometry using backpack survey platform was conducted to assess the distribution of dose rate around specific three survey sites. The carborne survey using gamma-ray spectrometers, as loading inside a vehicle, was successfully conducted to compare measured dose rates in routes from site to site and verify evaluation methods including the attenuation correction.
Kim, B. K.*; Tan, L.*; Sakasegawa, Hideo; Parish, C. M.*; Zhong, W.*; Tanigawa, Hiroyasu*; Kato, Yutai*
Journal of Nuclear Materials, 545, p.152634_1 - 152634_12, 2021/03
Times Cited Count:1 Percentile:16.35(Materials Science, Multidisciplinary)Nakanishi, Toshimichi*; Okuno, Mitsuru*; Yamasaki, Keiji*; Hong, W.*; Fujita, Natsuko; Nakamura, Toshio*; Horikawa, Yoshiyuki*; Sato, Eiichi*; Kimura, Haruo*; Tsutsumi, Hiroyuki*
Nagoya Daigaku Nendai Sokutei Kenkyu, 5, p.38 - 43, 2021/03
no abstracts in English
Song, T.*; Gubler, P.; Hong, J.*; Lee, S. H.*; Morita, Kenji*
Physics Letters B, 813, p.136065_1 - 136065_5, 2021/02
Times Cited Count:3 Percentile:34.88(Astronomy & Astrophysics)Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Radiation Physics and Chemistry, 179, p.109205_1 - 109205_11, 2021/02
Times Cited Count:6 Percentile:72.21(Chemistry, Physical)In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with several dose rate levels around the Fukushima Daiichi Nuclear Power Plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr(Ce) detectors to assess the radioactive cesium deposition in the ground. The diverse levels of radioactivity of Cs were then distributed to six survey sites from 30 to 3000 kBq m in the measurement period of October 2018. A method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site.
Taya, Hidetoshi*; Park, A.*; Cho, S.*; Gubler, P.; Hattori, Koichi*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; Monnai, Akihiko*; Onishi, Akira*; et al.
Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08
Times Cited Count:8 Percentile:69.78(Physics, Nuclear)Metoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.
JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03
Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
Ishikado, Motoyuki*; Shamoto, Shinichi; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Hong, T.*; Mutka, H.*
Scientific Reports (Internet), 8, p.16343_1 - 16343_6, 2018/11
Times Cited Count:3 Percentile:29.25(Multidisciplinary Sciences)Spin fluctuations are widely believed to play an important role as one of the most possible mechanisms for unconventional high-temperature superconductors. Here, the spin fluctuation in LaFePO is found at high energies such as 30-50 meV with comparable intensity to an optimally doped LaFeAs(O,F).
Metoki, Naoto; Yamauchi, Hiroki; Suzuki, Hiroyuki*; Kitazawa, Hideaki*; Hagihara, Masato*; Masuda, Takatsugu*; Aczel, A. A.*; Chi, S.*; Hong, T.*; Matsuda, Masaaki*; et al.
Journal of the Physical Society of Japan, 87(9), p.094704_1 - 094704_8, 2018/09
Times Cited Count:6 Percentile:46.54(Physics, Multidisciplinary)The -electron states of PrPdAl were revealed by neutron inelastic scattering. The flat -orbitals with large become stable under the two-dimensional CEF potential of unique crystal structure, which is the origin of the Ising anisotropy. A systematic understanding is possible in RPdAl based on this CEF potential. Especially the -type anisotropy in NpPdAl can be qualitatively understood with the positive Stevens factors. It mean that the local property is important for the physical properties of RPdAl including the heavy fermion superconductivity in NpPdAl.
Matsuda, Masaaki*; Onishi, Hiroaki; Okutani, Akira*; Ma, J.*; Agrawal, H.*; Hong, T.*; Pajerowski, D. M.*; Copley, J. R. D.*; Okunishi, Koichi*; Mori, Michiyasu; et al.
Physical Review B, 96(2), p.024439_1 - 024439_8, 2017/07
Times Cited Count:12 Percentile:51.46(Materials Science, Multidisciplinary)Wang, Y.*; Wang, L.*; Zheng, H.*; Li, K.*; Andrzejewski, M.*; Hattori, Takanori; Sano, Asami; Katrusiak, A.*; Meng, Y.*; Liao, F.*; et al.
Journal of Physical Chemistry C, 120(51), p.29510 - 29519, 2016/12
Times Cited Count:23 Percentile:62.07(Chemistry, Physical)Pressure-induced polymerization (PIP) of aromatic molecules can generate saturated carbon nanostructures. As a strongly interacted - stacking unit, the CH-CF adduct is widely applied in supramolecular chemistry, and it provides a good preorganization for the PIP. Here we investigated the structural variation of CH-CF cocrystal and the subsequent PIP process under high pressure. Four new molecular-complex phases V, VI, VII, and VIII have been identified and characterized by the in situ Raman, IR, synchrotron X-ray, and neutron diffraction. The phase V is different from the phases observed at low temperature, which has a tilted column structure. Phases VI and VII have a structure similar to phase V. Phase VIII polymerizes irreversibly upon compression above 25 GPa without any catalyst, producing sp(CH/F) materials. The - interaction is still dominant below 0.5 GPa but is most likely to be overstepped under further compression, which is important for discussing the supramolecular phase transition and the polymerization process.