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Hirobe, Daichi*; Sato, Masahiro*; Kawamata, Takayuki*; Shiomi, Yuki*; Uchida, Kenichi*; Iguchi, Ryo*; Koike, Yoji*; Maekawa, Sadamichi; Saito, Eiji
Nature Physics, 13(1), p.30 - 34, 2017/01
Times Cited Count:91 Percentile:96.69(Physics, Multidisciplinary)Ogata, Yudai*; Iguchi, Yusuke*; Tokuda, Makoto*; Januszko, K.*; Khandaker, J. I.*; Ono, Masao; Mashimo, Tsutomu*
Journal of Applied Physics, 117(12), p.125902_1 - 125902_6, 2015/03
Times Cited Count:7 Percentile:31.13(Physics, Applied)Ono, Masao; Okayasu, Satoru; Iguchi, Yusuke*; Esaka, Fumitaka; Bagum, R.*; Haruki, Rie; Mashimo, Tsutomu*
Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology Japan (Internet), 12(ists29), p.Tq_1 - Tq_3, 2014/04
We had realized the composition gradient of elements or isotopes in some binary alloys or single element by solid-state centrifugation. While, it might difficult to realize graded structure of elements in binary ionic crystal by centrifugation as it strongly keeps their stoichiometry. However, isotope fractionation in binary ionic crystal by centrifugation might be expected as the self-diffusion of ions occurs. We have planed the ultracentrifuge experiments on -AgI superionic conductor to investigate the isotope effect in binary ionic crystal under a strong centrifugal acceleration field. -AgI superionic conductor is suitable for the confirmation experiment as it is an intrinsic ionic crystal and Ag ions have high diffusivity. For the first stage, we have experimentally searched the experimental conditions of magnitude of centrifugal acceleration and temperature that ensure the experiment without decomposition. It is confirmed that the combination of experimental conditions of up to 6.110 g, 350C, 24h ensure the experiment without decomposition at least.
Nabara, Yoshihiro; Nunoya, Yoshihiko; Isono, Takaaki; Hamada, Kazuya; Takahashi, Yoshikazu; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Ebisawa, Noboru; et al.
IEEE Transactions on Applied Superconductivity, 22(3), p.4804804_1 - 4804804_4, 2012/06
Times Cited Count:17 Percentile:65.56(Engineering, Electrical & Electronic)no abstracts in English
Okayasu, Satoru; Ono, Masao; Nishio, Taichiro*; Iguchi, Yusuke*; Mashimo, Tsutomu*
Defect and Diffusion Forum, 323-325, p.545 - 548, 2012/04
Times Cited Count:0 Percentile:0.01Atomic sedimentation in solid occurs under mega-gravity treatment. As the result, partially melt-growth in -phase of BiPb-alloy occurs. Small difference of densities between fully hcp structure of BiPb and that of partially defected BiPb are enhanced under mega-gravity, and cause the separation of the -phase. Superconducting properties differs between the separated two phases.
Iguchi, Yusuke*; Mashimo, Tsutomu*; Ono, Masao; Okayasu, Satoru
Philosophical Magazine Letters, 90(7), p.513 - 518, 2010/07
Times Cited Count:4 Percentile:29.33(Materials Science, Multidisciplinary)We performed an ultracentrifuge experiment on Bi-Sb alloy. Deformation twins with misorientations of about 90 were observed in the low-gravitational region where grain refinement had not occurred. The twins were thicker than the conventional deformation twins and their thickness was proportional to the gravitational field. We found that the minimum gravitational field required for grain refinement was 1.710 G at 240 C for periods 10 h.
Suzuki, Daisuke; Kokubu, Yoko; Sakurai, Satoshi; Lee, C. G.; Magara, Masaaki; Iguchi, Kazunari*; Kimura, Takaumi
International Journal of Mass Spectrometry, 294(1), p.23 - 27, 2010/06
Times Cited Count:39 Percentile:87.26(Physics, Atomic, Molecular & Chemical)A new method for isotope ratio measurement with thermal ionization mass spectrometry (TIMS), "continuous heating method", was developed in order to determine an accurate isotope ratio of uranium ranging from sub-picograms to several dozen picograms. In this method, signals were measured during evaporation of an entire sample; however, part of the higher detected signals was used for calculation of the isotope ratio. The continuous heating method can measure the ratios with high reproducibility regardless of the sample amount and the skill of operators because procedures of measurement and data calculation were standardized, enabling accurate correction of mass discrimination effect. When U/U ratios in isotopic reference materials measured by the continuous heating method were compared with those measured by the conventional method and the total evaporation method, there was no difference in the case of measurement of a larger amount of samples. However, the continuous heating method showed the most accurate result compared with those measured by the other methods for the measurement of the sample of sub-picograms.
Ono, Masao; Sueyoshi, Masanori*; Okayasu, Satoru; Hao, T.; Esaka, Fumitaka; Osawa, Takahito; Iguchi, Yusuke*; Mashimo, Tsutomu
Review of Scientific Instruments, 80(8), p.083908_1 - 083908_6, 2009/08
Times Cited Count:3 Percentile:17.82(Instruments & Instrumentation)A prototype rotor with 2 grooves for the multi-stage centrifugal isotope separation in solid state was developed to test a new idea. This idea is based on the sedimentation of constitutional atoms in solid. In the performance test using indium specimen, it is verified that the developed rotor can receive all injected molten-indium droplets from an automatic raw-material feeding system even at the high rotational speed of 97,000 r.p.m. without the loss of rotational stability, and the received indium specimens can be transferred in/between 2 grooves through the plastic flow under the influence of strong centrifugal force even in the solid state. The isotope ratio of centrifuged indium specimens was analyzed employing the Secondary Ion Mass Spectrometry (SIMS), and it is confirmed that intended isotope separation by the centrifugation is realized in the solid state.
Ono, Masao; Iguchi, Yusuke*; Okayasu, Satoru; Esaka, Fumitaka; Kobayashi, Katsura*; Hao, T.; Bagum, R.*; Osawa, Takahito; Fujii, Kimio; Nakamura, Eizo*; et al.
Defect and Diffusion Forum, 289-292, p.63 - 68, 2009/04
The atomic-scale graded structure of In-Pb alloy was formed by an ultracentrifuge experiment under conditions that a gravitational field of 0.8110 G for 100 hours at 150 C in solid state in our previous study. The isotope ratio measurements were performed on the centrifuged sample with secondary ion mass spectrometer (SIMS). Pb/Pb and Pb/Pb isotope ratio changed with negative gradient in the direction of centrifugal force approximately 1.5% and 0.8%, respectively. And three-isotope diagram of Pb/Pb versus Pb/Pb proved that the isotope fluctuation depends on isotopic mass difference. These results showed that the strong gravitational field not only affected on the inter-diffusion but also on self-diffusion in this alloy as causing isotope fractionation effect, and the isotope fractionation was dependent on mass-difference.
Iguchi, Yusuke*; Ono, Masao; Okayasu, Satoru; Mashimo, Tsutomu
Defect and Diffusion Forum, 289-292, p.319 - 322, 2009/04
An atomic-scale graded structure has been formed by sedimentation of substitutional atoms under an ultra-strong gravitational field of 1 million G level in alloys and compounds. In this study, we investigate the sedimentation of impurity atoms in semiconductor materials under a strong gravitational field. High-temperature ultracentrifuge experiments (0.5910 G, 400C, 60 hours) have been performed on an InSb single crystal wafer which surface was coated with Ge by means of Physical Vapor Deposition (PVD). It was observed that the penetration depth of diffused Ge atoms under the gravitational field was several times larger than under terrestrial field at the same temperatures.
Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Takeda, Shingo*; Kimura, Shigeru*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru; Tsurui, Takao*; et al.
Defect and Diffusion Forum, 289-292, p.357 - 360, 2009/04
A visible four-layers structure with anomalous nano-sturucture was formed from a homogeneous e-phase BiPb intermetallic compound under a strong gravitational field (1.0210 G, 130C, 100 hours). In the 4th layer (lowest-gravity region), pure Bi particles precipitate. In the 2nd 3rd layers, composition graded structures, where Pb content increased along the gravity direction, were formed. It was found that the very broad XRD peak appeared in the 2nd layer, which indicated that an amorphous structure was contained.
Bagum, R.*; Okayasu, Satoru; Iguchi, Yusuke*; Ono, Masao; Mashimo, Tsutomu
Defect and Diffusion Forum, 289-292, p.517 - 521, 2009/04
Ultracentrifuge experiments were performed on the twinned YBaCuO (Y123) single crystal at much lower temperatures than the melting point. Two layers structure with slightly different compositions was observed in the sample ultracentrifuged at 250 C (380,000 G), which might be due to the sedimentation of atoms. In the strong gravity layer, it was found that the Y123 phase disappeared, and unknown XRD peaks appeared. Decomposition occurred in the sample ultracentrifuged at 400 C.
Osawa, Takahito; Ono, Masao; Esaka, Fumitaka; Okayasu, Satoru; Iguchi, Yusuke*; Hao, T.; Magara, Masaaki; Mashimo, Tsutomu
EPL; A Letters Journal Exploring the Frontiers of Physics, 85(6), p.64001_1 - 64001_5, 2009/03
Times Cited Count:6 Percentile:41.75(Physics, Multidisciplinary)Pure tin metals were centrifuged at 1 and at 220 C for 100 hours, 0.40 at 220-230 C for 24 hours, and 0.25 at 220 C for 24 hours. Their isotopic compositions were measured by a secondary ion mass spectrometer (SIMS). Sn/Sn and Sn/Sn ratios of the 1.02 sample were considerably different than the initial compositions, and the magnitude of isotopic fractionation reached 2.6%. A three-isotope diagram of Sn/Sn versus Sn/Sn shows conclusively that isotopic fractionation caused by a gravitational field depended only on isotopic mass.
Ono, Masao; Iguchi, Yusuke*; Okayasu, Satoru; Esaka, Fumitaka; Kobayashi, Katsura*; Hao, T.; Bagum, R.*; Osawa, Takahito; Fujii, Kimio; Nakamura, Eizo*; et al.
Journal of Nuclear Science and Technology, 45(Suppl.6), p.108 - 110, 2008/09
Times Cited Count:1 Percentile:10.12(Nuclear Science & Technology)The atomic-scale graded structure of In-Pb alloy was formed by an ultracentrifuge experiment under conditions that a gravitational field of 810,000 G for 100 hours at 150C (solid state) in our previous study. The isotope fluctuation on this sample was measured using secondary ion mass spectrometer (SIMS). The ratio both Pb/Pb and In/In changed with positive gradient in the direction of centrifugal force approximately 1.2%. These isotope fluctuations were larger than that of starting state of natural state (In0.2%, Pb0.1%). These show that the sedimentation of isotopes occurred by solid centrifugation in this alloy, although achieved concentration gradients were small.
Mashimo, Tsutomu; Ono, Masao; Huang, X.*; Iguchi, Yusuke*; Okayasu, Satoru; Kobayashi, Katsura*; Nakamura, Eizo*
Journal of Nuclear Science and Technology, 45(Suppl.6), p.105 - 107, 2008/09
Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)It was observed that the concentration ratio Se/Se increased by % level in the specimen ultracentrifuged at 0.70.9 million G and at 300C(liquid state) or 190C (solid state), respectively. The present result is evidence of sedimentation of substitutional atoms in condensed matter via self-diffusion, and suggests its possible application to isotope separation by condensed matter centrifugation.
Ono, Masao; Iguchi, Yusuke*; Bagum, R.*; Fujii, Kimio; Okayasu, Satoru; Esaka, Fumitaka; Mashimo, Tsutomu*
AIP Conference Proceedings 973, p.476 - 481, 2008/03
We had realized atomic-scale graded structures in several miscible alloys by ultracentrifuge experiment. In this study, we performed an ultracentrifuge experiment on a MgCd order-disorder alloy at disordered state of solid solution. The experimental conditions were as follows: maximum acceleration: 610,000 g, temperature: 400C, composition: Mg:Cd=50:50at%, time duration: 60 h). We investigated the crystal state of the centrifuged sample that had ordered from the disorder state of atomic-scale graded structure. It was found that the graded structure was formed in the centrifuged sample, in which Cd content continuously increased in the direction of gravitational field. It was also found that the different peaks from the starting state appeared in X-ray diffraction patterns of the centrifuged sample. We will present details at the session.
Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru
AIP Conference Proceedings 973, p.502 - 505, 2008/03
Ultra-high gravitational field (Mega-gravity field) can realize the sedimentation of atoms (diffusion) even in solids, and is expected to form a composition-graded structure and/or nonequilibrium phase in multi-component condensed matter. We had realized the sedimentation of substitutional solute atoms in miscible systems (Bi-Sb, In-Pb, etc.). In this study, the mega-gravity experiment at high temperature was performed on a thin-plate sample (0.7 mm in thickness) of intermetallic compound BiPb. A visible four-layers structure appeared, which indicated different microscopic structures. In the lowest-gravity region layer, Bi phase appeared. In the mid layers, the composition-graded structure was formed, while the powder X-ray diffraction patterns show difference. Such multi-layers structure was expected to show unique physical properties such as superconductivity. Keywords: Sedimentation of atoms, Ultra-high gravity field, BiPb, Graded structure.
Mashimo, Tsutomu; Ono, Masao; Huang, X. S.*; Iguchi, Yusuke*; Okayasu, Satoru; Kobayashi, Katsura*; Nakamura, Eizo*
Europhysics Letters, 81(5), p.56002_1 - 56002_4, 2008/03
Times Cited Count:12 Percentile:59.61(Physics, Multidisciplinary)A strong gravitational field resulted in the gravity-induced diffusion (sedimentation) of isotope atoms in monoatomic solid Se. The layer crystalline morphology consisting of three zones of the fine-grained crystals, the long crystals and feather-shaped crystals grown parallel to gravity direction appeared in the specimen ultracentrifuged at 0.8-1 million G and at 190 C. Change in concentration ratio Se/Se of 0.8% was observed in the grown crystalline region. These results show an evidence for sedimentation of substitutional atoms in solid via self-diffusion, and suggest possibility of application to control of impurity and crystalline state as well as to isotope separation.
Usuda, Shigekazu; Shinohara, Nobuo; Sakurai, Satoshi; Magara, Masaaki; Miyamoto, Yutaka; Esaka, Fumitaka; Yasuda, Kenichiro; Kokubu, Yoko; Hirayama, Fumio; Lee, C. G.; et al.
KEK Proceedings 2007-16, p.13 - 22, 2008/02
For the purpose of controlling and monitoring radiations and radioactive materials emitted from nuclear facilities to the environment and also evaluating their effects, various R&D on environmental radioactivity has been carried out at Japan Atomic Energy Agency (JAEA). Especially, for the abolition of nuclear weapons and for peaceful uses nuclear energy, ultra-trace analysis of environmental samples for safeguards and ultra-high sensitive monitoring of radionuclides for the CTBT verification, which have been scheduled in the middle of 1990s, have been promotted under the auspices of the Japanese Government at JAERI, the former of JAEA. In this presentation, the outline of R&D on environmental radioactivity for nuclear non-proliferation is introduced. In addition, applications of the developed techniques and future perspectives will be discussed.
Mashimo, Tsutomu; Ono, Masao; Huang, X. S.*; Iguchi, Yusuke*; Okayasu, Satoru; Kobayashi, Katsura*; Nakamura, Eizo*
Applied Physics Letters, 91(23), p.231917_1 - 231917_3, 2007/12
Times Cited Count:20 Percentile:60(Physics, Applied)A strong gravitational field resulted in the sedimentation of isotope atoms in monatomic liquid. The concentration ratio Se/Se increased by greater than 3.5% in specimen ultracentrifuged at 0.70.9 million G and at 300C. The recovered sample had a feather-shaped crystalline morphology. The concentration gradient was nearly twice that of the steady state analytical result (ideal gas system), indicating a non-ideal system diffusion. The present result is evidence of sedimentation of substitutional atoms in condensed matter via self-diffusion, and suggestes its possible application to isotope separation, crystalline control and matter dynamics in massive star.