Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.
Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10
Sano, Tomokazu*; Eimura, Takayuki*; Hirose, Akio*; Kawahito, Yosuke*; Katayama, Seiji*; Arakawa, Kazuto*; Masaki, Kiyotaka*; Shiro, Ayumi*; Shobu, Takahisa; Sano, Yuji*
Metals, 9(11), p.1192_1 - 1192_13, 2019/11
The purpose of the present study was to verify the effectiveness of dry laser peening (DryLP), which is the peening technique without a sacrificial overlay under atmospheric conditions using femtosecond laser pulses on the mechanical properties such as hardness, residual stress, and fatigue performance. After DryLP treatment of the laser-welded 2024 aluminum alloy, the softened weld metal recovered to the original hardness of base metal, while residual tensile stress in the weld metal and heat-affected zone changed to compressive stresses. The fatigue life almost doubled at a stress amplitude of 180 MPa and increased by a factor of more than 50 at 120 MPa. As a result, DryLP was found to be more effective for improving the fatigue performance of laser-welded aluminum specimens with welding defects at lower stress amplitudes.
Naoe, Takashi; Teshigawara, Makoto; Futakawa, Masatoshi; Mizutani, Haruki; Muramatsu, Toshiharu; Yamada, Tomonori; Ushitsuka, Yuji*; Tanaka, Nobuatsu*; Yamasaki, Kazuhiko*
Proceedings of 8th International Congress on Laser Advanced Materials Processing (LAMP 2019) (Internet), 5 Pages, 2019/05
Laser cutting is one of the options in the disposal of radio-active waste, such as spallation neutron target vessel in J-PARC, etc. Due to unique characteristic of laser, such as non-contact system, it is more easily to provide remote-controlled system in comparison with conventional one, such as mechanical cutting machine, etc. However, a demerit of laser cutting is the sputter and fume caused by laser cutting, resulting in contamination with radio-active materials its surroundings. Recently it was developed that the spatter suppression technique by controlling laser beam profile in laser welding process. In order to apply this suppression technique to laser cutting, first of all, we attempted to observe the phenomenon at melting area during laser cutting using a high-speed video camera in order to make the physical model. The result showed that the appearance of fume and sputter were independently confirmed in the time evolution.
Sasaki, Hirokazu*; Nishikubo, Hideo*; Nishida, Shinsuke*; Yamazaki, Satoshi*; Nakasaki, Ryusuke*; Isomatsu, Takemi*; Minato, Ryuichiro*; Kinugawa, Kohei*; Imamura, Akihiro*; Otomo, Shinya*; et al.
Furukawa Denko Jiho, (138), p.2 - 10, 2019/02
no abstracts in English
Aratani, Hidekazu*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Kawada, Moeki*; Kanai, Yuina*; Yamagami, Kohei*; Fujioka, Shuhei*; Hamamoto, Satoru*; Kuga, Kentaro*; Kiss, Takayuki*; et al.
Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09
Taguchi, Shigeo; Yamamoto, Masahiko; Furuse, Takahiro*; Masaki, Yuji*; Kuno, Takehiko
JAEA-Technology 2018-005, 14 Pages, 2018/06
The method to remove Pu, Am and Np from plutonium nitrate solution recovered from spent nuclear fuel prior to ICP-OES measurement has been developed for the determination of 18 impurity metal elements (Fe, Cr, Ni, Mn, Al, Cd, V, Cu, Si, Zn, Mo, Sn, Ca, Mg, Na, Ag, Pb, B). In this method, two TRU resin packed columns were used for separation. In the first column, Pu and Am were mainly removed by adsorption. The recovered solution from the fist column was added to the second column after reduction of Np, and Am(III) and Np(IV) were removed by adsorption. The Pu nitrate solution (22g/L) of 2mL were treated by proposed method. The alpha emission nuclide was decreased to 5.8 Bq/mL in a solution diluted to 100mL. As a result of ICP-OES measurement, the recoveries of impurity metals separated by proposed method were almost 100%. This separation scheme can apply to the metal impurity elemental analysis in Pu nitrate solution recovered from spent nuclear fuel.
Nakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.
Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03
Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Mori, Takeo*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; Yamagami, Hiroshi*; et al.
Journal of Electron Spectroscopy and Related Phenomena, 220, p.50 - 53, 2017/01
We report the soft X-ray angle-resolved photoemission study for LaNiGe to reveal the electronic structures derived from non-4 bands of the heavy fermion compound CeNiGe. The photoemission spectra recorded at the La M absorption edges clearly show the enhancement of the La 5 components in the valence band spectra. The circular dichroism of photoemission spectra reveals the band-dependent dichroic response due to the orbital symmetry.
Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.
Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11
In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides SrIrO using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO-plane structure. This transition occurs when the spin-orbit-coupled = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO and -dependent oscillations of photoelectron intensity in SrIrO. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.
Kaneko, Makoto*; Iwata, Hajime; Shiotsu, Hiroyuki; Masaki, Shota*; Kawamoto, Yuji*; Yamasaki, Shinya*; Nakamatsu, Yuki*; Imoto, Jumpei*; Furuki, Genki*; Ochiai, Asumi*; et al.
Frontiers in Energy Research (Internet), 3, p.37_1 - 37_10, 2015/09
The mobility of the aggregates of submicron-sized sheet aluminosilicate in the surface environment is a key factor controlling the current Cs migration in Fukushima.
Berner, G.*; Sing, M.*; Fujiwara, Hidenori*; Yasui, Akira*; Saito, Yuji; Yamasaki, Atsushi*; Nishitani, Yoshihito*; Sekiyama, Akira*; Pavlenko, N.*; Kopp, T.*; et al.
Physical Review Letters, 110(24), p.247601_1 - 247601_5, 2013/06
The interface between LaAlO and SrTiO hosts a two-dimensional electron system of itinerant carriers, although both oxides are band insulators. Interface ferromagnetism coexisting with superconductivity has been found and attributed to local moments. Experimentally, it has been established that Ti 3 electrons are confined to the interface. Using soft X-ray angle-resolved resonant photoelectron spectroscopy we have directly mapped the interface states in space. Our data demonstrate a charge dichotomy. A mobile fraction contributes to Fermi surface sheets, whereas a localized portion at higher binding energies is tentatively attributed to electrons trapped by O vacancies in the SrTiO.
Masaki, Kiyotaka*; Kameshima, Yohei*; Hisamori, Noriyuki*; Sano, Yuji*; Akita, Koichi; Shobu, Takahisa
Zairyo, 62(5), p.297 - 304, 2013/05
Effects of laser peening without protective coating (LPwC) for high cycle fatigue property on + type Ti-6Al-4V alloy were investigated. As the results of peening effect investigation, it was clear that the surface layer was slightly hardened and high level compressive residual stress was induced near the surface by the LPwC treatment. However, the fatigue property was not improved by the LPwC treatment on the condition. One of the reasons was thought notch effects by surface roughness, then fatigue tests with surface polished LPwC specimen were carried out. However, the fatigue life of polished LPwC specimen was shorter than that of LPwC specimen unexpectedly.
Yoshida, Masafumi; Tanabe, Tetsuo*; Nobuta, Yuji*; Hayashi, Takao; Masaki, Kei; Sato, Masayasu
Journal of Nuclear Materials, 390-391, p.635 - 638, 2009/06
We have investigated hydrogen isotopes retention in the outboard first wall tiles of JT-60U by means of TDS, SIMS and SEM. The outboard first wall tiles of JT-60U are mostly eroded. The total retention (H+D) normalized by a unit area and integrated NBI time in the eroded first wall tiles and the eroded divertor tiles were nearly the same, in spite of the lower temperature of the first wall. Differently from divertor tiles, in which H retention was dominated owing to HH discharges preformed after DD discharges, deuterium is dominated in hydrogen isotopes retention and penetrates deeper from the surface. This is attributed to injection of high energy D and difficulty of isotopic replacement owing to their lower temperature. The integrated amount over the whole surface could be appreciably large. This type of hydrogen retention could be also possible for the metallic wall.
Nobuta, Yuji*; Arai, Takashi; Yagyu, Junichi; Masaki, Kei; Sato, Masayasu; Tanabe, Tetsuo*; Yamauchi, Yuji*; Hino, Tomoaki*
Journal of Nuclear Materials, 390-391, p.643 - 646, 2009/06
The hydrogen and deuterium retention in gap side surfaces of the first wall tiles exposed to DD and HH discharges in JT-60U were investigated. The hydrogen and deuterium retention and boron deposition increased with the gap width. The depth profile of deuterium was very similar to that of boron, indicating that deuterium was incorporated with boron. Thick carbon deposition layer ( 1em) was observed in the gap of inboard tile and the atomic ratio in (H+D)/C at the carbon layer was estimated to be approximately 0.15. This value is higher than that observed in the divertor region. In this study, the H+D amount in gap side surfaces of the first wall was of the order of 1e23 1e24m.
Yogo, Akifumi; Sato, Katsutoshi; Nishikino, Masaharu; Mori, Michiaki; Teshima, Teruki*; Numasaki, Hodaka*; Murakami, Masao*; Demizu, Yusuke*; Akagi, Takashi*; Nagayama, Shinichi*; et al.
Applied Physics Letters, 94(18), p.181502_1 - 181502_3, 2009/05
Nagata, Hidezumi*; Hirao, Norie*; Onoki, Takamasa*; Baba, Yuji; Yamasaki, Yuki*; Nakahira, Atsushi*
Journal of the Ceramic Society of Japan, 116(1350), p.216 - 219, 2008/02
Bulky palladium catalyst supported on mesoporous silica (Pd-MCM-41) was successfully synthesized by hydrothermal hot-pressing method. The structure of the palladium species in Pd-MCM-41 bulk before and after heat-treatment process was investigated by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and transmission electron microscopy (TEM). On the basis of these results, the microstructures and mesoporous properties of Pd-MCM-41 were discussed. As a result, it was revealed that the obtained Pd-MCM-41 bulks possessed a high area of over 1000 m/g and the electronic state of palladium in Pd-MCM-41 bulk is almost equal to palladium (0) metal.
Sasaki, Yuji; Masaki, Tomoo*; Saeki, Morihisa
Chemistry Letters, 36(4), p.488 - 489, 2007/04
Using the new extractant, -tetraoctyl-diglycolamide (TODGA), the dependence of the distribution ratio on the ionic radii for M(II) was investigated and their relation with the structures of metal-complexes were discussed. Ca(II) (ionic radius: 100 pm) shows the highest D values, and the D values decrease with increase and decrease of ionic radius from 100 pm. The geometrical optimization by density functional theory (DFT) of M(II)-TODGA complex suggests that the carbonyl oxygen has more affinity with metal than the ether oxygen, and the distance between the center of oxygen donor and the edge of cation corresponds to the van der Waals radius of oxygen atom. The most stable complex, as 1:1 complex, can be formed with Mg(II) from DFT calculation, the complex become unstable with increase of ionic radius of M(II). This order is good agreement with the magnitude of D for Ca(II), Sr(II) and Ba(II).
Nobuta, Yuji; Masaki, Kei; Arai, Takashi; Sakasai, Akira; Miya, Naoyuki; Tanabe, Tetsuo*
Europhysics Conference Abstracts (CD-ROM), 31F, 4 Pages, 2007/00
no abstracts in English
Mo, S.-K.*; Kim, H.-D.*; Denlinger, J. D.*; Allen, J. W.*; Park, J.-H.*; Sekiyama, Akira*; Yamasaki, Atsushi*; Suga, Shigemasa*; Saito, Yuji; Muro, Takayuki*; et al.
Physical Review B, 74(16), p.165101_1 - 165101_12, 2006/10
We present high-resolution bulk-sensitive photoemission spectra of (V)O (=Cr,Ti). The measurements were made for the paramagnetic metal (PM), paramagnetic insulator (PI), and antiferromagnetic insulator (AFI) phases of (V)O. In the PM phase, we observe a prominent quasiparticle peak in general agreement with theory, which combines dynamical mean-field theory with the local density approximation. For both the PI and AFI phases, the vanadium 3 parts of the valence spectra are not simple one peak structures. For the PI phase, there is not yet a good theoretical understanding of these structures. Spectra taken in the same phases with different compositions show interesting monotonic changes as the dopant concentration increases, regardless of the dopant species. With increased Cr-doping, the AFI phase gap decreases and the PI phase gap increases.
Fukuda, Yuji; Kishimoto, Yasuaki; Masaki, Tomohiro*; Yamakawa, Koichi
Physical Review A, 73(3), p.031201_1 - 031201_4, 2006/03
An ultrashort, intense laser-cluster interaction and a resultant structure formation are investigated in detail by employing a particle code including relaxation and ionization processes. In addition to a laser-induced polarization field, we have found that an ambipolar radial electric field and an internal/external sheath field play a key role in a disassembling dynamics of the cluster. Electrons and ions show a complex behavior leading to a prominent dip structure in electron energy distribution and a double structure in ion density and energy distributions for higher charge states.