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Hayakawa, Sho*; Doihara, Kohei*; Okita, Taira*; Itakura, Mitsuhiro; Aichi, Masaatsu*; Suzuki, Katsuyuki*
Journal of Materials Science, 54(17), p.11509 - 11525, 2019/09
Times Cited Count：15 Percentile：56.33(Materials Science, Multidisciplinary)Nakanishi, Daiki*; Kawabata, Tomoya*; Doihara, Kohei*; Okita, Taira*; Itakura, Mitsuhiro; Suzuki, Katsuyuki*
Philosophical Magazine, 98(33), p.3034 - 3047, 2018/09
Times Cited Count：10 Percentile：47.84(Materials Science, Multidisciplinary)By using the six sets of interatomic potentials for face-centredcubic metals that differ in the stacking fault energy (SFE) while most of the other material parameters are kept almost identical, we conducted molecular dynamics simulations to evaluate the effects of SFE on the defect formation process through collision cascades. The ratio of glissile SIA clusters tends to decrease with increasing SFE. This is because perfect loops, the edges of which split into two partial dislocations with stacking fault structures between them in most cases, prefer to form at lower SFEs. The enhanced formation of glissile SIA clusters at lower SFEs can also be observed even at increased temperature.
Doihara, Kohei*; Okita, Taira*; Itakura, Mitsuhiro; Aichi, Masaatsu*; Suzuki, Katsuyuki*
Philosophical Magazine, 98(22), p.2061 - 2076, 2018/05
Times Cited Count：20 Percentile：71.42(Materials Science, Multidisciplinary)In this study, molecular dynamics simulations were performed to elucidate the effects of stacking fault energy (SFE) on the physical interactions between an edge dislocation and a spherical void in the crystal structure of face-centred cubic metals at various temperatures and for different void sizes. Four different types of interaction morphologies were observed, in which (1) two partial dislocations detached from the void separately, and the maximum stress corresponded to the detachment of the trailing partial; (2) two partial dislocations detached from the void separately, and the maximum stress corresponded to the detachment of the leading partial; (3) the partial dislocations detached from the void almost simultaneously without jog formation; and (4) the partial dislocations detached from the void almost simultaneously with jog formation. With an increase in void size or SFE, the interaction morphology changed in the above-mentioned order. It was observed that the magnitude of the critical resolved shear stress (CRSS) and its dependence on the SFE were determined by these interaction morphologies. The value of the CRSS in the case of interaction morphology (1) is almost equal to an analytical one based on the linear elasticity by employing the Burgers vector of a single partial dislocation. The maximum value of the CRSS is also obtained by the analytical model with the Burgers vector of the two partial dislocations.
Komori, Yukiko*; Yokokita, Takuya*; Kasamatsu, Yoshitaka*; Haba, Hiromitsu*; Toyoshima, Atsushi; Toyomura, Keigo*; Nakamura, Kohei*; Kanaya, Jumpei*; Huang, M.*; Kudo, Yuki*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1385 - 1388, 2015/02
Times Cited Count：2 Percentile：17.57(Chemistry, Analytical)We studied solid-liquid extraction behavior of carrier-free Mo and W radiotracers onto an Aliquat 336-loaded resin from HCl solutions toward extraction chromatography experiments of element 106, seaborgium(Sg). Distribution coefficients (
) of Mo and W on the resin were determined as a function of HCl concentration by a batch method. On-line extraction chromatography of Mo and W was also carried out in 2-8 M HCl solutions with an automated rapid chemistry apparatus. The order of extraction probability from 2 to 8 M HCl was Mo
W, which reflected the order of the values in the batch experiment.
Futakawa, Masatoshi; Naoe, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Okita, Kohei*
Experimental Thermal and Fluid Science, 57, p.365 - 370, 2014/09
Times Cited Count：10 Percentile：46.63(Thermodynamics)A liquid mercury target system for a megawatt-class spallation neutron source is being developed in the world. Proton beam is injected to the mercury target to induce spallation reaction. The moment the proton beams bombard the target, pressure waves are generated in the mercury by the thermally shocked heat deposition. The pressure waves excite the mercury target vessel and negative pressure that may cause cavitation along the vessel wall. Gas-bubbles will be injected into the flowing mercury to mitigate the pressure waves and suppress the cavitation inception. The injected gas-bubbles conditions were examined and the effects were predicted experimentally and theoretically from the viewpoints of macroscopic time-scale and microscopic time-scale, i.e. in the former is dominant the interaction between the structural vibration and the pressure in mercury, and in the later is essential the pressure wave propagation process.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi; Ikeda, Yujiro; Riemer, B.*; Wendel, M.*; Haines, J.*; Bauer, G.*; Naoe, Takashi; Okita, Kohei*; et al.
Journal of Nuclear Materials, 377(1), p.182 - 188, 2008/06
Times Cited Count：28 Percentile：85.1(Materials Science, Multidisciplinary)no abstracts in English
Yokokita, Takuya*; Oe, Kazuhiro; Komori, Yukiko*; Kikutani, Yuki*; Kino, Aiko*; Nakamura, Kohei*; Kasamatsu, Yoshitaka*; Takahashi, Naruto*; Yoshimura, Takashi*; Takamiya, Koichi*; et al.
no journal, ,
We carried out solvent extraction of Mo(VI), Mo(V), W(VI) and W(V) in 0.01-0.36 M Aliquat 336 / 0.1-11 M HCl system as model experiments for element 106, seaborgium (Sg). The HCl solutions of Mo(VI), Mo(V), W(VI) and W(V) were prepared using macro amounts of Mo and W. Extraction behaviors of mononuclear Mo and W were also investigated using carrier-free radiotracers 
Mo and 
W, which were produced as 
U(n, f) and Ta (p, n) reaction, respectively. The distribution ratios (D) of Mo(V) and W(V) were higher than those of Mo(VI) and W(VI), respectively. These results suggest that reduction behavior of the group-6 elements can be observed by solvent extraction. The D values of carrier-free Mo(VI) and W(VI) are almost the same as those with macro amounts in 6-11 M HCl. This condition would be suitable for the Sg experiments.
