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Hosokawa, Kaiji*; Yama, Masaki*; Matsuo, Mamoru; Kato, Takeo*
Physical Review B, 110(3), p.035309_1 - 035309_12, 2024/07
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Funato, Takumi*; Matsuo, Mamoru; Kato, Takeo*
Physical Review Letters, 132(23), p.236201_1 - 236201_7, 2024/06
Times Cited Count：2 Percentile：84.29(Physics, Multidisciplinary)Hirooka, Shun; Horii, Yuta; Sunaoshi, Takeo*; Uno, Hiroki*; Yamada, Tadahisa*; Vauchy, R.; Hayashizaki, Kohei; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Science and Technology, 60(11), p.1313 - 1323, 2023/11
Times Cited Count：5 Percentile：89.01(Nuclear Science & Technology)Additive MOX pellets are fabricated by a conventional dry powder metallurgy method. Nd
O
and SmO are chosen as the additive materials to simulate the corresponding soluble fission products dispersed in MOX. Shrinkage curves of the MOX pellets are obtained by dilatometry, which reveal that the sintering temperature is shifted toward a value higher than that of the respective regular MOX. The additives, however, promote grain growth and densification, which can be explained by the effect of oxidized uranium cations covering to a pentavalent state. Ceramography reveals large agglomerates after sintering, and Electron Probe Micro-Analysis confirms that inhomogeneous elemental distribution, whereas XRD reveals a single face-centered cubic phase. Finally, by grinding and re-sintering the specimens, the cation distribution homogeneity is significantly improved, which can simulate spent nuclear fuels with soluble fission products.
Pu
Am
O
uranium-plutonium-americium mixed oxides at 1573, 1773, and 1873 KVauchy, R.; Sunaoshi, Takeo*; Hirooka, Shun; Nakamichi, Shinya; Murakami, Tatsutoshi; Kato, Masato
Journal of Nuclear Materials, 580, p.154416_1 - 154416_11, 2023/07
Times Cited Count：8 Percentile：96.34(Materials Science, Multidisciplinary)Yama, Masaki*; Matsuo, Mamoru; Kato, Takeo*
Physical Review B, 107(17), p.174414_1 - 174414_15, 2023/05
Times Cited Count：3 Percentile：52.62(Materials Science, Multidisciplinary)Sato, Tetsuya*; Kato, Takeo*; Oue, Daigo*; Matsuo, Mamoru
Physical Review B, 107(18), p.L180406_1 - L180406_6, 2023/05
Times Cited Count：2 Percentile：38.37(Materials Science, Multidisciplinary)Ishikawa, Takuto*; Matsuo, Mamoru; Kato, Takeo*
Physical Review B, 107(5), p.054426_1 - 054426_9, 2023/02
Times Cited Count：1 Percentile：20.07(Materials Science, Multidisciplinary)Funato, Takumi*; Kato, Takeo*; Matsuo, Mamoru
Physical Review B, 106(14), p.144418_1 - 144418_10, 2022/10
Times Cited Count：4 Percentile：40.97(Materials Science, Multidisciplinary)
-wave superconductor/ferromagnetic insulator bilayer systemsOminato, Yuya*; Yamakage, Ai*; Kato, Takeo*; Matsuo, Mamoru
Physical Review B, 105(20), p.205406_1 - 205406_7, 2022/05
Times Cited Count：11 Percentile：76.32(Materials Science, Multidisciplinary)Sato, Tetsuya*; Tatsuno, Masahiro*; Matsuo, Mamoru; Kato, Takeo*
Journal of Magnetism and Magnetic Materials, 546, p.168814_1 - 168814_6, 2022/03
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Izumida, Wataru*; Okuyama, Rin*; Sato, Kentaro*; Kato, Takeo*; Matsuo, Mamoru
Physical Review Letters, 128(1), p.017701_1 - 017701_6, 2022/01
Times Cited Count：5 Percentile：59.61(Physics, Multidisciplinary)Yamamoto, Tsuyoshi*; Kato, Takeo*; Matsuo, Mamoru
Physical Review B, 104(12), p.L121401_1 - L121401_5, 2021/09
Times Cited Count：6 Percentile：40.97(Materials Science, Multidisciplinary)Yama, Masaki*; Tatsuno, Masahiro*; Kato, Takeo*; Matsuo, Mamoru
Physical Review B, 104(5), p.054410_1 - 054410_9, 2021/08
Times Cited Count：8 Percentile：51.67(Materials Science, Multidisciplinary) at high temperatures of 1673-1873 KWatanabe, Masashi; Kato, Masato; Sunaoshi, Takeo*
Journal of Nuclear Materials, 542, p.152472_1 - 152472_7, 2020/12
Times Cited Count：2 Percentile：19.64(Materials Science, Multidisciplinary)The oxygen self-diffusion coefficients in near stoichiometric (U,Pu)O at high temperatures were successfully measured by thermogravimetry combined with the oxygen isotope exchange method. The activation energy for oxygen diffusion in the stoichiometric composition of (U,Pu)O was evaluated from experimental data, and the value was determined to be 248 kJ/mol. In addition, the defect migration energies of (U,Pu)O were derived, and the oxygen self-diffusion coefficients were evaluated using these. As a result, good agreement was found between the experimental data and the oxygen self-diffusion coefficients calculated using the defect migration energies.
and (U,Pu,Am,Np)OHirooka, Shun; Matsumoto, Taku; Kato, Masato; Sunaoshi, Takeo*; Uno, Hiroki*; Yamada, Tadahisa*
Journal of Nuclear Materials, 542, p.152424_1 - 152424_9, 2020/12
Times Cited Count：11 Percentile：75.60(Materials Science, Multidisciplinary)The measurement of oxygen potential was conducted at 1,673, 1,773, and 1,873 K for (U
Pu
Am
)O and at 1,873 and 1,923 K for (U
Pu
Am
Np
)O by using a thermo-gravimeter and an oxygen sensor. Am inclusion in terms of substituting the U significantly increased the oxygen potential. Similarly, the inclusion of Np as a substitute for U increased the oxygen potential; however, the effect was not as large as that with the Pu or Am addition at the same rate. The results were analyzed via defect chemistry and certain defect formations were suggested in the reducing region and the near-stoichiometric region by plotting the relationship between PO and the deviation from the stoichiometry. The equilibrium constants of the defect reactions were arranged to reproduce the experiment such that Am/Np contents were included in the entropy with coefficients fitting the experimental data.
Kato, Takeo*; Onuma, Yuichi*; Matsuo, Mamoru
Physical Review B, 102(9), p.094437_1 - 094437_10, 2020/09
Times Cited Count：16 Percentile：66.68(Materials Science, Multidisciplinary)
U
)O
Nakamichi, Shinya; Hirooka, Shun; Kato, Masato; Sunaoshi, Takeo*; Nelson, A. T.*; McClellan, K. J.*
Journal of Nuclear Materials, 535, p.152188_1 - 152188_8, 2020/07
Times Cited Count：14 Percentile：80.81(Materials Science, Multidisciplinary)Oxygen-to-metal ratio (O/M) of uranium and plutonium mixed oxide depends on its oxygen partial pressure. To attain the desirable microstructure and O/M ratio of sintered pellets, it is important to investigate the relation between the sintering behavior and the atmosphere of sintering process. In this study, sintering behavior of (PuU)O and (PuU)O
in controlled po atmosphere were investigated. It was found activation energy of (PuU)O was higher than that of (PuU)O. On the other hand, it was observed grain growth during sintering was suppressed in hypo-stoichiometric composition.
Suzuki, Kiichi; Kato, Masato; Sunaoshi, Takeo*; Uno, Hiroki*; Carvajal-Nunez, U.*; Nelson, A. T.*; McClellan, K. J.*
Journal of the American Ceramic Society, 102(4), p.1994 - 2008, 2019/04
Times Cited Count：45 Percentile：91.74(Materials Science, Ceramics)The fundamental properties of CeO were assessed using a range of experimental techniques. The oxygen potential of CeO was measured by the thermogravimetric technique, and a numerical fit for the oxygen potential of CeO is derived based on defect chemistry. Mechanical properties of CeO were obtained using sound velocity measurement, resonant ultrasound spectroscopy and nanoindentation. The obtained mechanical properties of CeO are then used to evaluate the Debye temperature and Gruneisen constant. The heat capacity and thermal conductivity of CeO were also calculated using the Debye temperature and the Gruneisen constant. Finally, the thermal conductivity was calculated based upon laser flash analysis measurements. This result demonstrates that the thermal conductivity has strong dependence upon material purity.
Sakamoto, Tetsuo*; Morita, Masato*; Kanenari, Keita*; Tomita, Hideki*; Sonnenschein, V.*; Saito, Kosuke*; Ohashi, Masaya*; Kato, Kotaro*; Iguchi, Tetsuo*; Kawai, Toshihide*; et al.
Analytical Sciences, 34(11), p.1265 - 1270, 2018/11
Times Cited Count：10 Percentile：32.37(Chemistry, Analytical)Matsuo, Mamoru*; Onuma, Yuichi; Kato, Takeo*; Maekawa, Sadamichi
Physical Review Letters, 120(3), p.037201_1 - 037201_5, 2018/01
Times Cited Count：50 Percentile：90.10(Physics, Multidisciplinary)We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal metal (NM)/ferromagnet (FM) bilayer system. Starting with a simple FI-NM interface model with both spin-conserving and spin-non-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for an yttrium iron garnet (YIG) - platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the spin-non-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.
