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Journal Articles

On-line diffusion tracing in Li ionic conductors by the short-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Sugai, Hiroyuki; et al.

Japanese Journal of Applied Physics, 47(8), p.6413 - 6415, 2008/08

 Times Cited Count:5 Percentile:22.79(Physics, Applied)

A non-destructive and on-line diffusion tracing in Li ionic conductors has been demonstrated. As a tracer, pulsed beam of $$^{8}$$Li was implanted into LiGa. By analyzing the time dependent yield of the $$alpha$$-particles decaying from $$^{8}$$Li, diffusion coefficients were extracted with a high accuracy. The ordering of Li vacancies in the Li-deficient $$beta$$ phase of LiGa was observed for the first time in terms of the Li diffusion.

Journal Articles

Microstructure formation and in situ phase identification from undercooled Co-61.8 at.% Si melts solidified on an electromagnetic levitator and an electrostatic levitator

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:71.87(Materials Science, Multidisciplinary)

Co-61.8 at.% Si (CoSe-CoSi$$_{2}$$) 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$$_{2}$$ 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.

Journal Articles

Diffusion of $$^{8}$$Li short-lived radiotracer in Li ionic conductors of NaTl-type intermetallic compounds

Sugai, Hiroyuki; Sataka, Masao; Okayasu, Satoru; Ichikawa, Shinichi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Nakanoya, Takamitsu; Osa, Akihiko; Sato, Tetsuya; Hashimoto, Takashi; et al.

Defect and Diffusion Forum, 273-276, p.667 - 672, 2008/00

Journal Articles

Modeling and simulation of thermophysical properties of minor actinides-containing oxide fuels

Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Uno, Masayoshi*; Miwa, Shuhei; Osaka, Masahiko; Tanaka, Kenya; Yamanaka, Shinsuke*

Materials Research Society Symposium Proceedings, Vol.1043, p.190 - 195, 2008/00

The molecular dynamics (MD) calculation was performed on minor actinides (MA)-containing mixed oxide (MOX) fuels, (U$$_{0.7-x}$$Pu$$_{0.3}$$MA$$_{x}$$)O$$_{2}$$ (x = 0, 0.016, 0.03, 0.05, 0.1, 0.15), and the lattice parameter, heat capacity and thermal conductivity were evaluated. The calculated thermal conductivity data are comparable in (U$$_{0.7-x}$$Pu$$_{0.3}$$MA$$_{x}$$)O$$_{2}$$ at any temperature and any x value, indicating that the thermal conductivity of MA-containing MOX fuels is scarcely influenced by adding MA up to 15 %. The present study shows that the MD calculation can be usefully applied to determine the thermophysical properties of MA-containing MOX fuels.

Journal Articles

${it In situ}$ identification of the metastable phase during solidification from the undercooled YFeO$$_{3}$$ melt by fast X-ray diffractometry at 250 Hz

Nagashio, 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:61.23(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$$_{3}$$ (Re=Y and Lu) in order to identify the metastable phase ${it in situ}$. The metastable phase solidified primarily from the undercooled YFeO$$_{3}$$ melt finally transformed to the stable orthorhombic YFeO$$_{3}$$ phase during the short period of recalescence ($$sim$$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$$_{3}$$ system was consistent with that of the metastable hexagonal LuFeO$$_{3}$$ phase.

Journal Articles

Molecular dynamics studies of americium-containing mixed oxide fuels

Kurosaki, Ken*; Adachi, Jun*; Katayama, Masahito*; Osaka, Masahiko; Tanaka, Kenya; Uno, Masayoshi*; Yamanaka, Shinsuke*

Journal of Nuclear Science and Technology, 43(10), p.1224 - 1227, 2006/10

 Times Cited Count:11 Percentile:60.35(Nuclear Science & Technology)

The molecular dynamics (MD) calculation was performed for americium containing mixed oxide fuels, (U$$_{0.7-x}$$Pu$$_{0.3}$$Am$$_{x}$$)O$$_{2}$$ (x = 0, 0.016, 0.03, 0.05, 0.1, 0.15), in the temperature range from 300 to around 2500 K to evaluate the lattice parameter, heat capacity and thermal conductivity. The calculated lattice parameter is found to obey Vegard's law. The MD results reveal that the calculated heat capacity and thermal conductivity are at a similar level in the entire composition range, in other words they are scarcely influenced by adding americium up to 15 %.

Journal Articles

Real-time X-ray observation of solidification from undercooled Si melt

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:47.22(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 ($$Delta T<$$100K) did not increase at the plateau stage, while the diffraction pattern at medium undercoolings (100K$$<Delta T<$$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 ($$Delta T>$$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.

Journal Articles

Measurement of self-diffusion coefficients in Li ionic conductors by using the short-lived radiotracer of $$^8$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Okayasu, Satoru; et al.

Journal of Phase Equilibria and Diffusion, 26(5), p.472 - 476, 2005/09

Authors developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound $$beta$$LiAl using an $$alpha$$-emitting radiotracer of $$^8$$Li(T$$_{1/2}$$ = 0.84 s). It was found that the time-dependent yields of the alpha particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in $$beta$$LiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects.

Journal Articles

Measurement of diffusion coefficients in solids by the short-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Nuclear Instruments and Methods in Physics Research B, 230(1-4), p.596 - 600, 2005/04

 Times Cited Count:6 Percentile:45.55(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Precise Measurement of density and structure of undercooled molten silicon by using synchrotron radiation combined with electromagnetic levitation technique

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:87.17(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$$AA$$ 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.

Journal Articles

Simulation study on the measurements of diffusion coefficients in solid materials by short-lived radiotracer beams

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Iwase, Akihiro; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Japanese Journal of Applied Physics, Part 1, 42(7A), p.4576 - 4583, 2003/07

no abstracts in English

Journal Articles

Simulation study on the measurements of diffusion coefficients in solid materials by short-lived radiotracer beams

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Iwase, Akihiro*; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Japanese Journal of Applied Physics, Part 1, 42(7A), p.4576 - 4583, 2003/07

 Times Cited Count:14 Percentile:50.41(Physics, Applied)

no abstracts in English

Oral presentation

Fundamental properties of low-decontaminated fuels, 4; Molecular dynamics studies of (U,Pu,Np,Am)O$$_{2}$$

Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Uno, Masayoshi*; Yamanaka, Shinsuke*; Osaka, Masahiko; Tanaka, Kenya

no journal, , 

Fundamental properties were evaluated by the molecular Dynamics method on (U,Pu,Np,Am)O$$_{2}$$. Thermal properties of (U,Pu,Np,Am)O$$_{2}$$ having various compositions were calculated.

Oral presentation

Molecular dynamics simulations of MOX fuels containing minor actinides (MA: Np, Am)

Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Osaka, Masahiko; Miwa, Shuhei; Tanaka, Kenya; Muta, Hiroaki*; Uno, Masayoshi*; Yamanaka, Shinsuke*

no journal, , 

no abstracts in English

Oral presentation

Fundamental properties of low-decontaminated fuels, 6; Molecular dynamics studies of MOX containing MA

Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Uno, Masayoshi*; Yamanaka, Shinsuke*; Miwa, Shuhei; Osaka, Masahiko; Tanaka, Kenya

no journal, , 

Thermophysical propoerties of (U,Pu,Np)O$$_{2}$$ were evaluated by the molecular dynamics method for the purpose of understanding the phase relation and thermophysical propoerties of low-decontaminated fuel. Thermophysical properties of (U,Pu,Np)O$$_{2}$$ with various compositions were evaluated.

Oral presentation

Evaluation of physical properties of MOX fuels containing minor actinides by molecular dynamics simulation

Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Uno, Masayoshi*; Yamanaka, Shinsuke*; Miwa, Shuhei; Tanaka, Kenya; Osaka, Masahiko

no journal, , 

no abstracts in English

Oral presentation

Molecular dynamics simulation of the thermal properties of minor actinides-containing mixed oxide fuels

Kurosaki, Ken*; Katayama, Masahito*; Adachi, Jun*; Uno, Masayoshi*; Miwa, Shuhei; Osaka, Masahiko; Tanaka, Kenya; Yamanaka, Shinsuke*

no journal, , 

The molecular dynamics (MD) calculations were performed on MA-containing mixed oxide (MOX) fuels; in this case MA = Np and Am. The lattice parameter, heat capacity, and thermal conductivity of the MA-containing MOX fuels were evaluated and the effects of the MA content on the properties were studied. The calculated lattice parameter increased with temperature and varied linearly with the MA content. The calculated thermal conductivity data were comparable in MOX at any temperature and any x value, indicating that the thermal conductivity of MA-containing MOX fuels is scarcely influenced by adding MA up to 15 %. This result seems to be reasonable because both the mass and size differences between the ions of uranium and neptunium and/or americium are very small. The present study showed that the MD calculation can be usefully applied to determine the thermal properties of the MA-containing MOX fuels.

Oral presentation

Li diffusion in NaTl-type intermetallic compound LiGa observed by $$^{8}$$Li short-lived radiotracer

Sugai, Hiroyuki; Sataka, Masao; Okayasu, Satoru; Ichikawa, Shinichi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Nakanoya, Takamitsu; Osa, Akihiko; Sato, Tetsuya; Hashimoto, Takashi; et al.

no journal, , 

Non-destructive and on-line Li diffusion experiments in Li ionic conductors are conducted using the short-lived $$alpha$$-emitting radiotracer of $$^{8}$$Li. The radiotracers produced as an energetic and pulsed ion beam from TRIAC (Tokai Radioactive Ion Accelerator Complex) are implanted into a structural defect mediated Li ionic conductor of NaTl-type intermetallic compounds $$beta$$-LiGa. The diffusion coefficients obtained for $$beta$$-LiGa with Li content of 43-54 at.% at room temperature are discussed in terms of the interaction between Li-ion and the structural defects in the specimen, compared with the case of $$beta$$-LiAl and $$beta$$-LiIn. The nonlinear Li-content dependency of Li diffusion coefficients for $$beta$$-LiGa suggests that the Li diffusion with Li-deficient region is obstructed by the defect complex composed of vacancies at the Li sites.

18 (Records 1-18 displayed on this page)
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