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Ohashi, Tomonori*; Sakamaki, Tatsuya*; Funakoshi, Kenichi*; Steinle-Neumann, G.*; Hattori, Takanori; Yuan, L.*; Suzuki, Akio*
Journal of Mineralogical and Petrological Sciences (Internet), 120(1), p.240926a_1 - 240926a_13, 2025/06
We explore the structures of dry and hydrated (HO and D
O) Na
Si
O
melt at 0-6 GPa and 1000-1300 K and glasses recovered from high pressure and temperatures by in-situ neutron and X-ray diffraction. The structures of the melts at 0-10 GPa and 3000 K are also investigated by ab-initio molecular dynamics simulation. In-situ neutron experiments revealed that the D-O distance increases with compression due to the formation of -O-D-O- bridging species, which is reproduced by the molecular dynamics simulations. The pressure-induced -O-D-O- formation reflects a more rigid incorporation of hydrogen, which acts as a mechanism for the experimentally observed higher solubility of water in silicate melts. Together with shrinking modifier domains, this process dominates the compression behavior of hydrous Na
Si
O
melt, whereas the compression of dry Na
Si
O
at 0-10 GPa and 3000 K is governed largely by bending of the Si-O-Si angle. The molecular dynamics simulations on hydrous Na
Si
O
melts further suggest that the sodium ions are scavenged from its network-modifying role via 2(
Si-O
+ Na
)
Si-(O-
Si-O)
+ 2Na
and Si-O
+ Na
+ Si-OH
Si-(O-H-O-Si)
+ Na
with increasing pressure.
Beyer, D. C.*; Spektor, K.*; Vekilova, O. Y.*; Grins, J.*; Barros Brant Carvalho, P. H.*; Leinbach, L. J.*; Sannemo-Targama, M.*; Bhat, S.*; Baran, V.*; Etter, M.*; et al.
ACS Omega (Internet), 10(15), p.15029 - 15035, 2025/04
Times Cited Count:0 Percentile:0.00(Chemistry, Multidisciplinary)Hydridosilicates featuring SiH octahedral moieties represent a rather new class of compounds with potential properties relating to hydrogen storage and hydride ion conductivity. Here, we report on the new representative BaSiH
obtained from reacting the Zintl phase hydride BaSiH
with H
fluid at pressures above 4 GPa and subsequent decompression to ambient pressure. It consists of complex SiH
ions, which are octahedrally coordinated by Ba
counterions. The arrangement of Ba and Si atoms deviates only slightly from an ideal fcc NaCl structure. IR and Raman spectroscopy showed SiH
bending and stretching modes in the ranges 800-1200 and 1400-1800 cm
, respectively. BaSiH
is thermally stable up to 95
C above which decomposition into BaH
and Si takes place. DFT calculations indicated a direct band gap of 2.5 eV. The discovery of BaSiH
consolidates the compound class of hydridosilicates, accessible from hydrogenations of silicides at gigapascal pressures (
10 GPa). The structural properties of BaSiH
suggest that it presents an intermediate (or precursor) for further hydrogenation at considerably higher pressures to the predicted superconducting polyhydride BaSiH
.
Niu, X.*; Elakneswaran, Y.*; Li, A.*; Seralathan, S.*; Kikuchi, Ryosuke*; Hiraki, Yoshihisa; Sato, Junya; Osugi, Takeshi; Walkley, B.*
Cement and Concrete Research, 190, p.107814_1 - 107814_17, 2025/04
Times Cited Count:0 Percentile:0.00(Construction & Building Technology)Collaborative Laboratories for Advanced Decommissioning Science; Ibaraki University*
JAEA-Review 2023-021, 112 Pages, 2024/02
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Contribution to Risk Reduction in Decommissioning Works by the Elucidation of Basic Property of Radioactive Microparticles" conducted from FY2018 to FY2021 (this contract was extended to FY2021). The present study aims to understand the basic properties (size, chemical composition, isotopic composition - including concentration of -emitters, electrostatic properties, and optical properties, etc.) of fine particles composed of silicate with insoluble properties which contain regions of highly concentrated radioactive cesium (Cs) released to the environment by the accident at the Fukushima Daiichi Nuclear Power Station of TEPCO in 2011 March.
Kim, G.*; Cho, S.-M.*; Im, S.*; Suh, H.*; Morooka, Satoshi; Shobu, Takahisa; Kanematsu, Manabu*; Machida, Akihiko*; Bae, S.*
Construction and Building Materials, 411, p.134529_1 - 134529_18, 2024/01
Times Cited Count:10 Percentile:67.40(Construction & Building Technology)Cho, S.*; Suh, H.*; Im, S.*; Kim, G.*; Kanematsu, Manabu*; Morooka, Satoshi; Machida, Akihiko*; Shobu, Takahisa; Bae, S.*
Construction and Building Materials, 409, p.133866_1 - 133866_20, 2023/12
Times Cited Count:13 Percentile:83.68(Construction & Building Technology)Im, S.*; Jee, H.*; Suh, H.*; Kanematsu, Manabu*; Morooka, Satoshi; Choe, H.*; Nishio, Yuhei*; Machida, Akihiko*; Kim, J.*; Lim, S.*; et al.
Construction and Building Materials, 365, p.130034_1 - 130034_18, 2023/02
Times Cited Count:17 Percentile:77.68(Construction & Building Technology)Kim, G.*; Im, S.*; Jee, H.*; Suh, H.*; Cho, S.*; Kanematsu, Manabu*; Morooka, Satoshi; Koyama, Taku*; Nishio, Yuhei*; Machida, Akihiko*; et al.
Cement and Concrete Research, 159, p.106869_1 - 106869_17, 2022/09
Times Cited Count:27 Percentile:86.84(Construction & Building Technology)Kawaguchi, Munemichi; Uno, Masayoshi*
Journal of Crystal Growth, 585, p.126590_1 - 126590_7, 2022/05
Phase-field mobility, , and crystal growth rates in crystallization of 11 oxides or mixed oxides in undercooled silicates, SiO
and GeO
liquids were calculated with a simple phase-field model (PFM), and material dependence of the
was discussed. Ratios between experimental crystal growth rates and the PFM simulation with
were confirmed to be proportional to a power of
on the solid/liquid interface process during the crystal growth in a log-log plot. We determined that parameters,
and
, of the
were
to
m
J
s
and
to
, which were unique for the materials. It was confirmed that our PFM simulation with the determined
reproduced quantitively the experimental crystal growth rates. The
has a proportional relationship with the diffusion coefficient of a cation molar mass average per unit an oxygen molar mass at
in a log-log graph. The
depends on the sum of the cation molar mass per the oxygen molar mass,
, in a compound. In
, the
decreases with the cation molar mass increasing. The assumed cause is that the B represents the degree of the temperature dependence of the
. Since the cation molar mass is proportional to an inertial resistance of the cation transfer, the
decreases with inverse of the cation molar mass. In crystallization of the silicates of heavy cation in
, the
saturates at approximately 0.67, which leads to
.
Im, S.*; Jee, H.*; Suh, H.*; Kanematsu, Manabu*; Morooka, Satoshi; Koyama, Taku*; Nishio, Yuhei*; Machida, Akihiko*; Kim, J.*; Bae, S.*
Journal of the American Ceramic Society, 104(9), p.4803 - 4818, 2021/09
Times Cited Count:26 Percentile:83.08(Materials Science, Ceramics)Sato, Junya; Shiota, Kenji*; Takaoka, Masaki*
Zairyo, 70(5), p.406 - 411, 2021/05
An aluminosilicate solid is an inorganic material that has the property of immobilizing heavy metals or radionuclides in the matrix. In this study, aluminosilicates with a Si/Al molar ratio of 0.5 was synthesized from a chemical reagent in order to produce aluminosilicate solids with a low Si/Al molar ratio, which were expected to improve the immobilization of heavy metals and radionuclides contained in the matrix. The synthesized Si-Al gel with a Si/Al molar ratio of 0.5 had little impurity content and was in an amorphous phase. In addition, the compressive strength of the aluminosilicate solid produced by the synthesized Si-Al gel showed a 5 MPa or more, confirming that it can be used as a raw material for aluminosilicate solids. The aluminosilicate solid with a Si/Al molar ratio of 1.25 had a dense surface structure from the result of BSE images and had the highest compressive strength among all samples.
Collaborative Laboratories for Advanced Decommissioning Science; Ibaraki University*
JAEA-Review 2020-033, 84 Pages, 2021/01
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2018, this report summarizes the research results of the "Contribution to Risk Reduction in Decommissioning Works by the Elucidation of Basic Property of Radioactive Microparticles" conducted in FY2019.
Kawaguchi, Munemichi; Uno, Masayoshi*
Journal of the Ceramic Society of Japan, 128(10), p.832 - 838, 2020/10
Times Cited Count:3 Percentile:12.51(Materials Science, Ceramics)This study developed phase-field method (PFM) technique in oxide melt system by using a new mobility coefficient (). The crystal growth rates (
) obtained by the PFM calculation with the constant
were comparable to the thermodynamic driving force in normal growth model. The temperature dependence of the
was determined from the experimental crystal growth rates and the
. Using the determined
, the crystal growth rates (
) in alkali disilicate glasses, Li
O-2SiO
, Na
O-2SiO
and K
O-2SiO
were simulated. The temperature dependence of the
was qualitatively and quantitatively so similar that the PFM calculation results demonstrated the validity of the
. Especially, the
obtained by the PFM calculation appeared the rapid increase just below the thermodynamic melting point (
) and the steep peak at around
-100 K. Additionally, as the temperature decreased, the
apparently approached zero ms
, which is limited by the
representing the interface jump process. Furthermore, we implemented the PFM calculation for the variation of the parameter
in the
. As the
increased from zero to two, the peak of the
became steeper and the peak temperature of the
shifted to the high temperature side. The parameters
and
in the
increased exponentially and decreased linearly as the atomic number of the alkali metal increased due to the ionic potential, respectively. This calculation revealed that the
and
in the
were close and reasonable for each other.
Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*
Journal of Nuclear Science and Technology, 57(9), p.1062 - 1073, 2020/09
Times Cited Count:9 Percentile:64.46(Nuclear Science & Technology)The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high temperature conditions. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under Ar-5%H and Ar-4%H
-20%H
0 with maximum temperature of 1100
C. Prior being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also the sake of thermodynamic evaluation to those available ones. Based upon the initial condition (preliminary heat treatment) of calcium silicate, it was found that if the original material consisted of xonotlite (Ca
Si
0
(0H)
), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730
C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0
), the interaction occurred over temperature range 700-1100
C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H
and Ar-4%H
-20%H
0 atmosphere, cesium aluminum silicate, CsAlSi0
was formed with aluminum in the samples as an impurity or adduct.
Otani, Eiji*; Suzuki, Akio*; Ando, Ryota*; Urakawa, Satoru*; Funakoshi, Kenichi*; Katayama, Yoshinori
Advances in High-Pressure Technology for Geophysical Applications, p.195 - 209, 2005/09
This paper summarizes the techniques for the viscosity and density measurements of silicate melt and glasses at high pressure and temperature by using the X-ray radiography and absorption techniques in the third generation synchrotron radiation facility, SPring-8, Japan. The falling sphere method using in situ X-ray radiography makes it possible to measure the viscosity of silicate melts to the pressures above 6 GPa at high temperature. We summarize the details of the experimental technique of the viscosity measurement, and the results of the measurements of some silicate melts such as the albite and diopside-jadeite systems. X-ray absorption method is applied to measure the density of the silicate glasses such as the basaltic glass and iron sodium disilicate glass up to 5 GPa at high temperature. A diamond capsule, which is not reactive with the glass, is used for the density measurement of the glasses. The present density measurement of the glasses indicates that this method is useful for measurement of the density of silicate melts at high pressure and temperature.
Kameo, Yutaka; Nakashima, Mikio; Hirabayashi, Takakuni*
Journal of Nuclear Science and Technology, 41(9), p.919 - 924, 2004/09
Times Cited Count:14 Percentile:64.92(Nuclear Science & Technology)A new laser decontamination method utilizing a gel made from a sodium silicate solution and an acid was developed for removing radioactive nuclide incorporated into a surface oxide layer on metal waste. Decontamination tests were carried out using both simulated contaminated samples and pipe specimens cut from the primary coolant system of the Japan Power Demonstration Reactor. In the case of surface oxide layer consisting mainly of iron oxide, more than 99% of surface radioactivities were removed after two to three decontamination runs. In order to ascertain the role of laser irradiation on chemical reactions, chemical states of O and Fe in the oxide layer before and after decontamination were analyzed by X-ray photoelectron spectroscopy. It was found that the oxide layer was dissolved into the acid-containing gel, and the reaction was extensively promoted by the laser irradiation.
Nakashima, Mikio; Nakashio, Nobuyuki; Kameo, Yutaka; Fukui, Toshiki*; Isobe, Motoyasu*; Otake, Atsushi*; Wakui, Takuji*; Hirabayashi, Takakuni*
Radiochimica Acta, 91(1), p.45 - 51, 2003/01
Times Cited Count:2 Percentile:18.49(Chemistry, Inorganic & Nuclear)no abstracts in English
Onuki, Kaoru; ; Nakajima, Hayato; Shimizu, Saburo
J. Chem. Eng. Jpn., 30(2), p.359 - 362, 1997/00
Times Cited Count:3 Percentile:34.98(Engineering, Chemical)no abstracts in English
Kudo, Hiroshi
Radiochimica Acta, 50, p.71 - 74, 1990/00
no abstracts in English
; Bamba, Tsunetaka
Journal of Nuclear Science and Technology, 26(6), p.607 - 615, 1989/06
no abstracts in English