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Journal Articles

Superparamagnetically modified A-type, X-type and CHA-type zeolites with silica-coated Fe $_{3}$ O $_{4}$ and CoFe $_{2}$ O $_{4}$ nanoparticles for removal of Sr $^{2+}$ and Cs $^{+}$ from radioactively contaminated water

Ito, Azusa; Thirunavukkarasu, G.*; Hriljac, J. A.*

Frontiers in Environmental Chemistry (Internet), 5, p.1445482_1 - 1445482_19, 2024/09

https://doi.org/10.3389/fenvc.2024.1445482

Magnetised zeolite A, zeolite X and Na,K-CHA composites with superparamagnetic nanoparticles of SiO $_{2}$ -coated Fe $_{3}$ O $_{4}$ or CoFe $_{2}$ O $_{4}$ ferrite spinels were prepared, characterised and tested for ion exchange efficacy. They were synthesised by following three steps, synthesising Fe $_{3}$ O $_{4}$ and CoFe $_{2}$ O $_{4}$ nanoparticles by a solvothermal method, coating the metal oxide particles with SiO $_{2}$ by a sol-gel process, and attaching the M $_{x}$ O $_{y}$ /SiO $_{2}$ onto the zeolites during synthesis. The magnetic zeolites were characterised by X-ray diffraction, X-ray fluorescence spectroscopy, Raman spectroscopy, vibrating sample magnetometry and both scanning and transmission electron microscopy. It was confirmed they had superparamagnetic properties due to successful attachment of the M $_{x}$ O $_{y}$ /SiO $_{2}$ particles onto the zeolites. Adsorption capacities of Sr $^{2+}$ onto the magnetic zeolite A and zeolite X and Cs $^{+}$ onto the magnetic Na,K-CHA were also evaluated. The results show the M $_{x}$ O $_{y}$ /SiO $_{2}$ did not block the adsorption sites of the zeolites and the M $_{x}$ O $_{y}$ /SiO $_{2}$ particles were not detached from the zeolites during the adsorption experiments.

Journal Articles

Phase-field mobility for crystal growth rates in undercooled silicates, SiO and GeO liquids

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of Crystal Growth, 585, p.126590_1 - 126590_7, 2022/05

https://doi.org/10.1016/j.jcrysgro.2022.126590

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 $frac{TDelta T}{eta}$ on the solid/liquid interface process during the crystal growth in a log-log plot. We determined that parameters, and , of the $L=A(frac{k_{B}TDelta T}{6pi^{2}lambda^{3}eta T_{m} })^{B}$ were $A=6.7times 10^{-6}$ to mJ $^{-1}$ s $^{-1}$ 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 $T_{m}$ in a log-log graph. The depends on the sum of the cation molar mass per the oxygen molar mass, $frac{Sigma_{i}M_{i}}{M_{O}}$ , in a compound. In $frac{Sigma_{i}M_{i}}{M_{O}}leq 25$ , 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 $frac{Sigma_{i}M_{i}}{M_{O}}geq 25$ , the saturates at approximately 0.67, which leads to $T_{p}approx 0.9T_{m}$ .

Journal Articles

Effect of resonant core-level excitation in an atom on photoemission from the neighboring atoms

Baba, Yuji*; Shimoyama, Iwao

Chemical Physics, 550, p.111302_1 - 111302_5, 2021/10

https://doi.org/10.1016/j.chemphys.2021.111302

Times Cited Count：2 Percentile：7.91(Chemistry, Physical)

The effect of a core-to-valence resonant photoexcitation in an atom on photoemission from the neighboring atoms has been experimentally investigated. For SiO $_{2}$ fine powder mixed with boron nitride matrix, it was found that the intensity of the O photoelectrons was reduced around the Si resonant photoexcitation. On the other hand, the intensity of the B or N photoelectrons from the matrix material did not change regardless of the photon energy. Similar phenomenon was also observed for Si $_{3}$ N $_{4}$ powder mixed with cellulose as a matrix material. The results demonstrated that photoemission from the nearest-neighbor atoms that are directly bound to silicon is perturbated by the core-to-valence resonant photoexcitation in silicon. Using the phenomenon, it is expected that species of the nearest neighbor atom can be identified by a resonant core-level excitation in a target atom.

Journal Articles

Formation of Type A glassy cesium-bearing microparticles from HEPA filter materials in Unit 3 during Fukushima Dai-ichi NPS accident; From viewpoint of similarity in silicate glass composition

Hidaka, Akihide

Proceedings of 2021 International Congress on Advances in Nuclear Power Plants (ICAPP 2021) (USB Flash Drive), 10 Pages, 2021/10

Author recently proposed that the Type A glassy Cesium-bearing microparticles that were released during the Fukushima accident may have been formed by melting and atomization of glass fibers of the High Efficiency Particulate Air (HEPA) filter in the Stand-by Gas Treatment System (SGTS) line in Unit 3 during the hydrogen explosion. In the present study, the components of the Type A and glass fibers of HEPA filter were examined using EPMA. The results showed that the components of the Type A were almost the same as that of the glass fibers except for Cs, Fe, Sn, which are considered to have been contained in the in-vessel-derived particles. When the glass fiber was irradiated with the electron beam of the Electron Probe Micro Analyzer (EPMA) under vacuum condition, spherical particles of a few micro m size were formed that looked very similar to the Type A. These strongly suggest that the HEPA filter is Si source of the Type A.

Journal Articles

Fabrication, permeation, and corrosion stability measurements of silica membranes for HI decomposition in the thermochemical iodine-sulfur process

Myagmarjav, O.; Shibata, Ai*; Tanaka, Nobuyuki; Noguchi, Hiroki; Kubo, Shinji; Nomura, Mikihiro*; Takegami, Hiroaki

International Journal of Hydrogen Energy, 46(56), p.28435 - 28449, 2021/08

https://doi.org/10.1016/j.ijhydene.2021.06.079

Times Cited Count：5 Percentile：13.95(Chemistry, Physical)

Journal Articles

Evaluation of oxidation efficiency of hydrophobic palladium catalyst for $^{3}$ H monitoring in radioactive gaseous waste

Furutani, Misa; Kometani, Tatsunari; Nakagawa, Masahiro; Ueno, Yumi; Sato, Junya; Iwai, Yasunori*

Hoken Butsuri (Internet), 55(2), p.97 - 101, 2020/06

https://doi.org/10.5453/jhps.55.97

Herein, an oxidation catalyst was introduced after heating it to 600 $^{circ}$ C to oxidize tritium gas (HT) existing in exhaust into tritiated water vapor (HTO). This study aims to establish a safer $^{3}$ H monitoring system by lowering the heating temperature required for the catalyst. In these experiments, which were conducted in the Nuclear Science Research Institute, Japan Atomic Energy Agency, cupric oxide, hydrophobic palladium/silicon dioxide (Pd/SiO $_{2}$ ), and platinum/aluminum oxide (Pt/Al $_{2}$ O $_{3}$ ) catalysts were ventilated using standard hydrogen gas. After comparing the oxidation efficiency of each catalyst at different temperatures, we found that the hydrophobic Pd/SiO $_{2}$ and Pt/Al $_{2}$ O $_{3}$ catalysts could oxidize HT into HTO at 25 $^{circ}$ C.

Journal Articles

Evaluation of oxidation efficiency of hydrophobic palladium catalyst for $^{14}$ C monitoring in gaseous radioactive waste

Ueno, Yumi; Nakagawa, Masahiro; Sato, Junya; Iwai, Yasunori

Hoken Butsuri, 51(1), p.7 - 11, 2016/03

https://doi.org/10.5453/jhps.51.7

In the Nuclear Science Research Institute, Japan Atomic Energy Agency (JAEA), in order to oxidize $^{14}$ C, which exists in various chemical forms in exhaust, into $^{14}$ CO $_{2}$ , a copper oxide (CuO) catalyst is introduced after heating to 600 $^{circ}$ C. Our goal was to establish a safer $^{14}$ C monitoring system by lowering the heating temperature required for the catalyst; therefore, we developed a new hydrophobic palladium/silicon dioxide (Pd/SiO $_{2}$ ) catalyst that makes the carrier's surface hydrophobic. In these experiments, catalysts CuO, platinum/aluminum oxide (Pt/Al $_{2}$ O $_{3}$ ), palladium/zirconium dioxide (Pd/ZrO $_{2}$ ), hydrophobic Pd/SiO $_{2}$ , and hydrophilic Pd/SiO $_{2}$ were ventilated with standard methane gas, and we compared the oxidation efficiency of each catalyst at different temperatures. As a result, we determined that the hydrophobic Pd/SiO $_{2}$ catalyst had the best oxidation efficiency. By substituting the currently used CuO catalyst with the hydrophobic Pd/SiO $_{2}$ catalyst, we will be able to lower the working temperature from 600 $^{circ}$ C to 300 $^{circ}$ C and improve the safety of the monitoring process.

Journal Articles

Alignment of grain orientation in polycrystalline-SiO $_{2}$ films induced by high-energy heavy ions

Shinde, N. S.*; Matsunami, Noriaki*; Shimura, Tetsuo*; Sataka, Masao; Okayasu, Satoru; Kato, Teruo; Tazawa, Masato*

Nuclear Instruments and Methods in Physics Research B, 245(1), p.231 - 234, 2006/04

https://doi.org/10.1016/j.nimb.2005.11.107

Times Cited Count：4 Percentile：33.39(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Synchrotron radiation photoelectron emission study of SiO $_{2}$ film formed by a hyperthermal O-atom beam at room temperature

Tagawa, Masahito*; Sogo, Chie*; Yokota, Kumiko*; Hachiue, Shunsuke; Yoshigoe, Akitaka; Teraoka, Yuden

Japanese Journal of Applied Physics, 44(12), p.8300 - 8304, 2005/12

https://doi.org/10.1143/JJAP.44.8300

Times Cited Count：5 Percentile：21.06(Physics, Applied)

Si oxide layers formed on Si(001) substrates by irradiation of hyperthermal oxygen atomic beams at room temperature were analysed at the JAERI soft X-ray beamline by photoemission spectroscopy. It was found that sub-oxide components were scarcely observed in the Si oxide layers formed by the atomic oxygen beam.

Journal Articles

Interface properties of 4H-SiC MOS structures studied by a slow positron beam

Maekawa, Masaki; Kawasuso, Atsuo; Yoshikawa, Masahito; Ichimiya, Ayahiko

Materials Science Forum, 445-446, p.144 - 146, 2004/05

no abstracts in English

Journal Articles

Heat stability of Mo/Si multilayers inserted with compound layers

Ishino, Masahiko; Yoda, Osamu; Takenaka, Hisataka*; Sano, Kazuo*; Koike, Masato

Surface & Coatings Technology, 169-170(1-3), p.628 - 631, 2003/06

no abstracts in English

Journal Articles

Optimization of the silicon oxide layer thicknesses inserted in the Mo/Si multilayer interfaces for high heat stability and high reflectivity

Ishino, Masahiko; Yoda, Osamu

Journal of Applied Physics, 92(9), p.4952 - 4958, 2002/11

https://doi.org/10.1063/1.1510566

Times Cited Count：6 Percentile：27.61(Physics, Applied)

no abstracts in English

Journal Articles

Measurements of the depth profile of the refractive indices in oxide films on SiC by spectroscopic ellipsometry

Iida, Takeshi*; Tomioka, Yuichi*; Yoshimoto, Kimihiro*; Midorikawa, Masahiko*; Tsukada, Hiroyuki*; Orihara, Misao*; Hijikata, Yasuto*; Yaguchi, Hiroyuki*; Yoshikawa, Masahito; Ito, Hisayoshi; et al.

Japanese Journal of Applied Physics, Part 1, 41(2A), p.800 - 804, 2002/02

https://doi.org/10.1143/JJAP.41.800

Times Cited Count：17 Percentile：54.79(Physics, Applied)

no abstracts in English

Journal Articles