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melt by two-dimensional detector at 1 kHzKumar, M. V.*; Kuribayashi, Kazuhiko*; Nagashio, Kosuke*; Ishikawa, Takehiko*; Okada, Jumpei*; Yu, J.*; Yoda, Shinichi*; Katayama, Yoshinori
Applied Physics Letters, 100(19), p.191905_1 - 191905_4, 2012/05
Times Cited Count：2 Percentile：8.9(Physics, Applied)
identification of metastable phases formed from the undercooled LuFeO melt under controlled oxygen partial pressure 
o
was studied by X-ray diffraction measurements at a synchrotron radiation source. Real-time observation of the formation and growth of individual phases during the single recalescence of LuFeO
and LuFeO
phases at o of 1
10
Pa has been revealed by a high speed imaging system at 1 kHz. The obtained diffraction pattern of the metastable phase in the LuFeO system was consistent with that of the metastable and stable phases reported in the Lu-Fe-O system.
Li, M.*; Nagashio, Kosuke*; Ishikawa, Takehiko*; Mizuno, Akitoshi*; Adachi, Masayoshi*; Watanabe, Masahito*; Yoda, Shinichi*; Kuribayashi, Kazuhiko*; Katayama, Yoshinori
Acta Materialia, 56(11), p.2514 - 2525, 2008/06
Times Cited Count：23 Percentile：71.59(Materials Science, Multidisciplinary)Co-61.8 at.% Si (CoSe-CoSi) eutectic alloys were solidified on an electromagnetic levitator (EML) and an electrostatic levitator (ESL) at different undercooling levels. The results indicated that there is only a single recalescence event at low undercooling with the CoSi intermetallic compound as primary phase, which is independent of processing facilities, on either an EML or an ESL. The microstructure, however, is strongly dependent on the processing facility. On high undercooling, double recalescence takes place regardless of levitation condition. In situ X-ray diffraction of alloys solidified on the EML demonstrates that the CoSi compound becomes the primary phase upon the first recalescence, and the CoSi intermetallic phase crystallizes during the second recalescence. In addition to phase identification, real-time diffraction patterns can also provide additional evidence of the fragmentation of the primary phase.
Nagashio, Kosuke*; Nozaki, Kiyoshi*; Kuribayashi, Kazuhiko*; Katayama, Yoshinori
Applied Physics Letters, 91(6), p.061916_1 - 061916_3, 2007/08
Times Cited Count：6 Percentile：26.4(Physics, Applied)The spontaneous dendrite fragmentation in solidification from undercooled Si melt was studeid by time-resolved 2D X-ray diffractometry using sinchrotron radiation. For the sample solidified at 
=261 K, several diffraction spots appeared at 1 ms after recalescence and the subsequent transition from spots to rings occurred within 
25 ms, which suggests that the fragmentation occurred after recalescence but just at the initial stage of the plateau period. Although the present experiment supported that the driving force for the fragmentation is a capillarity effect at the plateau period, the time scale for the fragmentation differed from the current quantitative prediction.
identification of the metastable phase during solidification from the undercooled YFeO melt by fast X-ray diffractometry at 250 HzNagashio, Kosuke*; Kuribayashi, Kazuhiko*; Vijaya Kumar, M. S.*; Niwata, Kenji*; Hibiya, Taketoshi*; Mizuno, Akitoshi*; Watanabe, Masahito*; Katayama, Yoshinori
Applied Physics Letters, 89(24), p.241923_1 - 241923_3, 2006/12
Times Cited Count：22 Percentile：61.1(Physics, Applied)A time-resolved X-ray diffraction (XRD) experiment at 250 Hz using a synchrotron radiation source was carried out during the containerless solidification of ReFeO (Re=Y and Lu) in order to identify the metastable phase 
. The metastable phase solidified primarily from the undercooled YFeO melt finally transformed to the stable orthorhombic YFeO phase during the short period of recalescence (0.035 s). Although the metastable phase could not be detected in the as-solidified sample by the powder XRD, the successfully obtained diffraction pattern of the metastable phase in the YFeO system was consistent with that of the metastable hexagonal LuFeO phase.
Nagashio, Kosuke*; Adachi, Masayoshi*; Higuchi, Kensuke*; Mizuno, Akitoshi*; Watanabe, Masahito*; Kuribayashi, Kazuhiko*; Katayama, Yoshinori
Journal of Applied Physics, 100(3), p.033524_1 - 033524_6, 2006/08
Times Cited Count：14 Percentile：47.09(Physics, Applied)Grain refined microstructure is often obtained spontaneously in the solidification of metals and semiconductors from the undercooled melt without any external forces. Although it has been reported that the grain refinement is mainly caused by the fragmentation of the dendrites, the dynamic process of the fragmentation of dendrites has not been fully understood because the microstructure after the solidification has been analyzed. Here, we present a time-resolved 2- dimensional X-ray diffraction experiment on the solidification of Si from the undercooled melt. The number of diffraction spots observed at low undercoolings (
100K) did not increase at the plateau stage, while the diffraction pattern at medium undercoolings (100K
200K) changed from the spots with the tail to rings with the lapse of time. Both this result and high speed video imaging suggested that the high-order arms of the dendrites mostly detached from the main stems because nucleation could not be expected at the melting point after recalescence. The several spots observed at low undercoolings drastically changed to rings at high undercoolings (
200K), which indicated the complete fragmentation of dendrite main stem as well as high-order arms. This complete fragmentation resulted in the grain refined microstructure.
Higuchi, Kensuke*; Kimura, Kakuryo*; Mizuno, Akitoshi*; Watanabe, Masahito*; Katayama, Yoshinori; Kuribayashi, Kazuhiko*
Measurement Science and Technology, 16(2), p.381 - 385, 2005/02
Times Cited Count：43 Percentile：87.03(Engineering, Multidisciplinary)X-ray diffraction and density measurements have been simultaneously performed to investigate the atomic structure of molten silicon in wide temperature range including undercooling region by using the electromagnetic levitation technique. The density was obtained from the mass and the shape of levitated sample by non-contact method based on the image analysis technique. X-ray diffraction experiments were performed by using the synchrotron radiation at SPring8, Japan. From structural analysis of undercooled molten silicon, first nearest neighbour coordination numbers and interatomic distances were about 5 and 2.48
with no dependence on temperature in the range of 1900-1550 K. We conclude as a result that the short-range order based on tetrahedral bonds of undercooled molten silicon does not change with the degree of undercoolings but medium-range order changes by the degree of undercoolings.
Toyoshima, Atsushi; Kasamatsu, Yoshitaka; Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Ishii, Yasuo; Tome, Hayato; Sato, Tetsuya; Nishinaka, Ichiro; Nagame, Yuichiro; et al.
no journal, ,
no abstracts in English
mediaKasamatsu, Yoshitaka; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Akiyama, Kazuhiko*; Kikunaga, Hidetoshi*; et al.
no journal, ,
Dubnium-262 was produced in the 
Cm(
F, 5
) reaction at the JAEA tandem accelerator. Adsorption of Db on the anion-exchange resin was investigated in 0.89 M HF/0.3 M HNO solution. The anion-exchange behavior of Nb, Ta, and Pa as homologues of Db was also examined in details in HF/HNO solutions. From the comparison of those results, we found that the adsorption of Db on the anion-exchange resin is considerably weaker than that of Ta and is relatively similar to those of Nb and Pa in the studied conditions.
solutionsKasamatsu, Yoshitaka; Tome, Hayato; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Shinohara, Nobuo; Nagame, Yuichiro; et al.
no journal, ,
Anion-exchange behavior of 
Db (half-life 
= 34 s) produced in the Cm(F, 5) reaction at the JAEA tandem accelerator was investigated in the mixed 0.89 M HF/0.3 M HNO solution ([F
] = 3 10
M) with the automated ion-exchange separation apparatus coupled with the detection system for alpha-spectroscopy (AIDA). Anion-exchange behavior of its lighter homologues, Nb and Ta, was also studied under the same conditions using 
Nb ( = 14.3 min) and 
Ta ( = 6.76 min) produced in the 
Ge(F, 
) and Gd(F, ) reactions, respectively. It was found that the adsorption probability on the anion-exchange resin is in the order of Ta 
Nb Db under the present condition.
solutionsKasamatsu, Yoshitaka; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Ishii, Yasuo; Tome, Hayato; Nishinaka, Ichiro; Akiyama, Kazuhiko*; Kikunaga, Hidetoshi*; et al.
no journal, ,
Dubnium-262 was produced in the nuclear reaction of Cm(F,5n)Db using the JAEA Tandem accelerator. The reaction products were rapidly transported to the chemistry laboratory and the anion-exchange behavior of Db in HF/HNO media was investigated with an on-line rapid ion-exchange apparatus. Based on the comparison of the behavior of Db with that of its homologues (Nb, Ta, and Pa), the fluoride complex formation of Db was discussed.
