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Wang, Q.*; Ma, N.*; Huang, W.*; Shi, J.*; Luo, X.-T.*; Tomitaka, Sora*; Morooka, Satoshi; Watanabe, Makoto*
Materials Research Letters (Internet), 11(9), p.742 - 748, 2023/09
Times Cited Count：2 Percentile：20.10(Materials Science, Multidisciplinary)Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; Kajimoto, Ryoichi; et al.
Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09
Times Cited Count：12 Percentile：92.34(Multidisciplinary Sciences)Lam, T.-N.*; Chin, H.-H.*; Zhang, X.*; Feng, R.*; Wang, H.*; Chiang, C.-Y.*; Lee, S. Y.*; Kawasaki, Takuro; Harjo, S.; Liaw, P. K.*; et al.
Acta Materialia, 245, p.118585_1 - 118585_9, 2023/02
Times Cited Count：19 Percentile：88.60(Materials Science, Multidisciplinary)
GeTe
Bao, S.*; Wang, W.*; Shangguan, Y.*; Cai, Z.*; Dong, Z.-Y.*; Huang, Z.*; Si, W.*; Ma, Z.*; Kajimoto, Ryoichi; Ikeuchi, Kazuhiko*; et al.
Physical Review X, 12(1), p.011022_1 - 011022_15, 2022/02
Times Cited Count：25 Percentile：94.45(Physics, Multidisciplinary)CuTeO
Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Cai, Z.*; Wang, W.*; Huang, Z.*; Ma, Z.*; Liao, J.*; Zhao, X.*; Kajimoto, Ryoichi; et al.
Physical Review B, 104(22), p.224430_1 - 224430_8, 2021/12
Times Cited Count：1 Percentile：5.86(Materials Science, Multidisciplinary)Miao, P.*; Tan, Z.*; Lee, S. H.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Yonemura, Masao*; Koda, Akihiro*; Komatsu, Kazuki*; Machida, Shinichi*; Sano, Asami; et al.
Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03
Times Cited Count：3 Percentile：21.40(Materials Science, Multidisciplinary)The layered perovskite PrBaCoO
demonstrates a strong negative thermal expansion (NTE) which holds potential for being fabricated into composites with zero thermal expansion. The NTE was found to be intimately associated with the spontaneous magnetic ordering, known as magneto-volume effect (MVE). Here we report with compelling evidences that the continuous-like MVE in PrBaCoO is intrinsically of discontinuous character, originating from an magnetoelectric transition from an antiferromagnetic insulating large-volume (AFILV) phase to a ferromagnetic less-insulating small-volume (FLISV) phase. Furthermore, the magnetoelectric effect (ME) shows high sensitivity to multiple external stimuli such as temperature, carrier doping, hydrostatic pressure, magnetic field etc. In contrast to the well-known ME such as colossal magnetoresistance and multi-ferroic effect which involve symmetry breaking of crystal structure, the ME in the cobaltite is purely isostructural. Our discovery provides a new path way to realizing the ME as well as the NTE, which may find applications in new techniques.
Naeem, M.*; He, H.*; Zhang, F.*; Huang, H.*; Harjo, S.; Kawasaki, Takuro; Wang, B.*; Lan, S.*; Wu, Z.*; Wang, F.*; et al.
Science Advances (Internet), 6(13), p.eaax4002_1 - eaax4002_8, 2020/03
Times Cited Count：189 Percentile：99.24(Multidisciplinary Sciences)Wang, X.*; Hou, Z.*; Ikeda, Takashi; Huang, S.-F.*; Terakura, Kiyoyuki*; Boero, M.*; Oshima, Masaharu*; Kakimoto, Masaaki*; Miyata, Seizo*
Physical Review B, 84(24), p.245434_1 - 245434_7, 2011/12
Times Cited Count：32 Percentile：75.45(Materials Science, Multidisciplinary)The structural and electronic properties of N-doped zigzag graphene ribbons with various ratios of di- to monohydrogenated edge carbons are investigated within the density functional theory framework. We find that the stability of graphitic N next to the edge, which is claimed to play important roles in the catalytic activity in our previous work, will be enhanced with increasing the concentration of di-hydrogenated carbons. Furthermore, the di-hydrogenated edge carbons turn out to be easily converted into mono-hydrogenated ones in the presence of oxygen molecules at room temperature. Based on our results, we propose a possible way to enhance the oxygen reduction catalytic activity of N-doped graphene by controlling the degrees of hydrogenation of edge carbons. The characteristic features in the X-ray absorption and emission spectra for each specific N site considered here will also be given.
-edge X-ray absorption spectra of nanographeneHou, Z.*; Wang, X.*; Ikeda, Takashi; Huang, S.-F.*; Terakura, Kiyoyuki*; Boero, M.*; Oshima, Masaharu*; Kakimoto, Masaaki*; Miyata, Seizo*
Journal of Physical Chemistry C, 115(13), p.5392 - 5403, 2011/03
Times Cited Count：38 Percentile：71.44(Chemistry, Physical)Carbon 
-edge X-ray absorption spectra of nanographene have been simulated by density functional theory calculations in order to obtain the information on the edge termination by hydrogen. Our results show that different edge terminations significantly affect the binding energy of 1s core-level of C atoms in the vicinity of edges because of the change in chemical bonding and the localized edge states. We find that a shoulder or a peak appears below the 
peak at relatively different positions with respect to the peak position in the theoretical spectra of zigzag graphene nano-ribbons, depending on the ratio of mono-hydrogen- to di-hydrogen-terminations. We also point out that the two additional features observed between the and 
peaks of an ideal graphene originate from the states of C-H bonding and C-H bonding at the edges.
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：0.00(Nuclear Science & Technology)It was observed that the concentration ratio 
Se/
Se increased by % level in the specimen ultracentrifuged at 0.7
0.9 million G and at 300
C(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.
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：59.15(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.
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：59.40(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.
Huang, X. S.*; Ono, Masao; Ueno, Hideto*; Iguchi, Yusuke*; Tomita, Takeshi; Okayasu, Satoru; Mashimo, Tsutomu
Journal of Applied Physics, 101(11), p.113502_1 - 113502_5, 2007/06
Times Cited Count：26 Percentile：67.36(Physics, Applied)A large linearly graded structure on atomic-scale up to 88 at%/mm with oriented grown crystals was formed in selenium-tellurium (Se-Te) semiconductor using a strong gravitational field of 1 million G level at 260 C. The lattice constants and the binding energies of Se and Te 3
electrons continuously changed along the direction of gravity accordingly, which indicated the formation of the graded band gap structure. The grown crystals showed the crystalline orientation with c-axis of hexagonal structure roughly perpendicular to the direction of gravity. It was found that the diffusion coefficient of sedimentation was larger than that of normal diffusion by more than 100 times, which suggested a different diffusion mechanism from the normal vacancy mechanism.
Iguchi, Yusuke*; Shibata, Yasuhiro*; Uchida, Yuta*; Huang, X.*; Ono, Masao; Okayasu, Satoru; Mashimo, Tsutomu
Advanced Materials Research, 15-17, p.639 - 642, 2007/00
Times Cited Count：2 Percentile：58.93(Thermodynamics)In this study, we investigate the crystalline states and conditions for the grain-refinement of Bi
Sb
alloy. It was considered under an ultra strong gravity field, the crystals were fine-grained from the primary grain sizes of several mm to several tens of mm, and the crystal growth followed with formation of graded-composition structure due to sedimentation of atoms along the direction of gravity. It was found that for the crystal-grain refinement in BiSb alloy the minimum gravitational field and the minimum time duration were at least 160,000 G and 10 hours, respectively at about 200 C.
Ono, Masao; Kinoshita, Takahiro*; Huang, X. S.*; Iguchi, Yusuke*; Okayasu, Satoru; Mashimo, Tsutomu*
Nihon Kinzoku Gakkai-Shi, 70(6), p.511 - 516, 2006/06
Times Cited Count：0 Percentile：0.00(Metallurgy & Metallurgical Engineering)Ultracentrifuge experiments were performed on a miscible In-Pb alloy to study sedimentation of constitutional atoms under a strong gravitational field (maximum acceleration: 10
g level, temperature: below melting point (solid), starting state: intermediate 
-phase (f.c.t., c
/a
1), time duration: 30-150 h). The Graded structures were formed in all centrifuged samples, in which, the Pb content continuously increased, and the In content decreased in the direction of gravitational field. It was experimentally cleared that the composition profiles gradually changed with time and the change of composition profiles converged to steady state within 60 hours in case of the experimental conditions. And it was found that the diffusion coefficient for sedimentation was about 8 times larger than that for usual diffusion. According to the simulation, the diffusion coefficient for the sedimentation could be estimated as about 10
m
/s in the case of these experimental conditions. The present result indicated that the diffusion mechanism of the sedimentation in this system was different from the conventional one.
Pb
intermetallic compoundOno, Masao; Huang, X. S.*; Shibata, Yasuhiro*; Iguchi, Yusuke*; Sakai, Seiji; Maekawa, Masaki; Chen, Z. Q.*; Osakabe, Toyotaka; Kawasuso, Atsuo; Naramoto, Hiroshi*; et al.
Proceedings of 1st International Conference on Diffusion in Solids and Liquids (DSL 2005), p.531 - 533, 2005/07
Recently, we formed atomic-scale graded structures in some miscible alloys and observed the decomposition in BiPb intermetallic compound by sedimentation of atoms under strong gravitational field. In this study, we measured positron lifetime of centrifuged BiPb, to which the composition change was very small as it was treated at low temperature. It was found that the positron lifetime became longer than that of starting state. This indicated that the point defects (vacancy or divacancy) increased in the sample by centrifugal treatment. We are now investigating the relationship between increase in point defects and sedimentation of atoms.
Ono, Masao; Kinoshita, Takahiro*; Ueno, Hideto*; Huang, X.*; Osakabe, Toyotaka; Mashimo, Tsutomu
Materials Transactions, 46(2), p.219 - 224, 2005/02
Times Cited Count：8 Percentile：54.44(Materials Science, Multidisciplinary)Ultracentrifuge experiments were performed on the In-Pb system to study the sedimentation of atoms and phase equilibrium. After the experiments, the graded structures were obtained. Pb-rich phase (f.c.c) and In-rich phase (tetragonal) appeared at the strong- and weak-gravitational field sides of the sample, respectively, from starting state of -phase. And, the continuous changes in lattice parameters were observed in each phase. These observation results showed that the graded structure was continuous in atomic scale, and was formed by the sedimentation of atoms. Composition profiles of the centrifuged samples for 31.3 h, 60 h and 150 h showed that the composition change reached the steady state within 60 hours. The diffusion coefficient for sedimentation was estimated to be about 8 times larger than that for usual diffusion by the simulation. The result indicated that the diffusion mechanism of the sedimentation was different from the conventional ones.
Ono, Masao; Huang, X.*; Kinoshita, Takahiro*; Ueno, Hideto*; Osakabe, Toyotaka; Mashimo, Tsutomu
Defect and Diffusion Forum, 237-240(2), p.1101 - 1104, 2005/00
Ultra-strong gravitational field can induce sedimentation of even atoms in condensed matter. We had realized sedimentation of substitutional solute atoms in some miscible alloys. How about in the other alloys? So, In this study, the ultra-centrifuge experiments were performed on an intermetallic compound of Bi-Pb system (BiPb) by changing time duration of experiment time (experimental conditions; maximum centrifugal force: 1.0
10g level, temperature: 130-150 C, duration: 30-150h, state: solid). Composition changes were observed in the centrifuged samples. And, it was found that the Bi phase appeared from starting state of BiPb around the weak gravitational field region of the sample. These results showed that sedimentation of substitutional solute atoms occurred, and induced the structure change in intermetallic compounds.
Huang, X.*; Mashimo, Tsutomu; Ono, Masao; Tomita, Takeshi; Sawai, Tomotsugu; Osakabe, Toyotaka; Mori, Nobuo*
Journal of Applied Physics, 96(3), p.1336 - 1340, 2004/08
Times Cited Count：12 Percentile：44.70(Physics, Applied)Mega-gravity field experiments were performed on the BiSb(atomic percent) alloy and pure Bi below their melting points, to investigate the change in crystalline state. For the alloy centrifuged at 191-205 C, no change in composition was observed, and the grain sizes of the crystals decreased from several mm to tens of 
m, while no distinct change in grain size was observed for the centrifuged pure Bi. The alloy centrifuged at 220-240 C consisted of two regions with different morphologies-fine-grained crystals with grain sizes around tens of m in the low gravity region, and large crystals with grain sizes several mm long and hundreds of m wide along the direction of gravity in the high gravity region, where sedimentation of atoms was confirmed. The large crystals with hexagonal structures were formed by preferential crystal growth roughly along the c axes, and a large strain that increased as the gravitational field increased existed inside these crystals. Formation of this anomalous crystal state might be correlated with the sedimentation of atoms.
Mashimo, Tsutomu; Huang, X.; Osakabe, Toyotaka; Ono, Masao*; Nishihara, Masamichi*; Ihara, Hirotaka*; Sueyoshi, Masanori*; Shibasaki, Koji*; Shibasaki, Shiro*; Mori, Nobuo*
Review of Scientific Instruments, 74(1), p.160 - 163, 2003/01
Times Cited Count：54 Percentile：88.91(Instruments & Instrumentation)An ultracentrifuge apparatus, which could generate an ultra-strong gravitational field of even 1,000,000 (1 million) G (1G = 9.8 m/s) in a wide temperature range up to 500C with high stability controls, was developed for new materials science research. The system consisted of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter up to 160 mm, a vacuum chamber and a heating system. The ultracentrifuge experiments using the 70 and 80 mm-diam rotors made of titanium alloy with rotational speeds of up to 170,000 rpm at temperatures of even over 200C for 100 hours with the ripples of 0.05% and 1 degree, respectively, were successfully performed, where the maximum gravitational field at sample was 1,000,000 G, and the potential energy and sample volume were larger than those of the Kumamoto University one (Rev. Sci. Instr. 67, 3170 (1996)) by 1.9 and 4 times, respectively.
