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Journal Articles

Study on cesium compound formation by chemical interaction of CsOH and concrete at elevated temperatures

Luu, V. N.; Nakajima, Kunihisa

Journal of Nuclear Science and Technology, 60(2), p.153 - 164, 2023/02

 Times Cited Count:3 Percentile:73.56(Nuclear Science & Technology)

Journal Articles

Emulsification of low viscosity oil in alkali-activated materials

Reeb, C.*; Davy, C. A.*; Pierlot, C.*; Bertin, M.*; Cantarel, V.; Lambertin, D.*

Cement and Concrete Research, 162, p.106963_1 - 106963_16, 2022/12

 Times Cited Count:2 Percentile:47.64(Construction & Building Technology)

Journal Articles

High-temperature gaseous reaction of cesium with siliceous thermal insulation; The Potential implication to the provenance of enigmatic Fukushima cesium-bearing material

Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*

ACS Omega (Internet), 7(33), p.29326 - 29336, 2022/08

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

Journal Articles

Quantifying internal strains, stresses, and dislocation density in additively manufactured AlSi10Mg during loading-unloading-reloading deformation

Zhang, X. X.*; Andr$"a$, H.*; Harjo, S.; Gong, W.*; Kawasaki, Takuro; Lutz, A.*; Lahres, M.*

Materials & Design, 198, p.109339_1 - 109339_9, 2021/01

 Times Cited Count:33 Percentile:95.11(Materials Science, Multidisciplinary)

Journal Articles

Investigation of high-temperature chemical interaction of calcium silicate insulation and cesium hydroxide

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:7 Percentile:68.59(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$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 with maximum temperature of 1100$$^{circ}$$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$$_{6}$$Si$$_{6}$$0$$_{17}$$(0H)$$_{2}$$), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730$$^{circ}$$C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0$$_{3}$$), the interaction occurred over temperature range 700-1100$$^{circ}$$C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H$$_{2}$$ and Ar-4%H$$_{2}$$-20%H$$_{2}$$0 atmosphere, cesium aluminum silicate, CsAlSi0$$_{4}$$ was formed with aluminum in the samples as an impurity or adduct.

Journal Articles

Continuous liquid-liquid extraction of uranium from uranium-containing wastewater using an organic phase-refining-type emulsion flow extractor

Nagano, Tetsushi; Naganawa, Hirochika; Suzuki, Hideya; Toshimitsu, Masaaki*; Mitamura, Hisayoshi*; Yanase, Nobuyuki*; Grambow, B.

Analytical Sciences, 34(9), p.1099 - 1102, 2018/09

 Times Cited Count:12 Percentile:46.95(Chemistry, Analytical)

A previously reported emulsion flow (EF) extraction system does not include a device for refining used solvent. Therefore, the processing of large quantities of wastewater by using the EF extractor alone could lead to the accumulation of wastewater components into the solvent and diminished extraction performance. In the present study, we have developed a solvent-washing-type EF system, which is equipped with a unit for washing used solvent to prevent accumulation, and successfully applied it for treating uranium-containing wastewater.

Journal Articles

Development of a water purifier for radioactive cesium removal from contaminated natural water by radiation-induced graft polymerization

Seko, Noriaki*; Hoshina, Hiroyuki*; Kasai, Noboru*; Shibata, Takuya; Saiki, Seiichi*; Ueki, Yuji*

Radiation Physics and Chemistry, 143, p.33 - 37, 2018/02

 Times Cited Count:15 Percentile:85.91(Chemistry, Physical)

Journal Articles

Synthesis of a minute SiC product from polyvinylsilane with radiation curing, 2; Ceramization process of radiation cured polyvinylsilane

Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Journal of Materials Science, 42(1), p.130 - 135, 2007/01

 Times Cited Count:3 Percentile:14.25(Materials Science, Multidisciplinary)

We have synthesized minute SiC products from polyvinylsilane (PVS), which is a liquid organosilicon polymer, with radiation curing. Since there is a close relationship between the properties of obtained SiC products and pyrolysis condition, it is important to investigate the ceramization process of PVS in order to find out the optimum pyrolysis condition. In this paper, the ceramization process of the PVS cured by $$gamma$$-ray irradiation at room temperature was investigated by gas analysis, thermogravimetric analysis, density measurement, and so on. It was found that the ceramization of $$gamma$$-ray cured PVS starts above 500K, and that drastic organic-inorganic conversion occurs in the temperature range of 700-1100K. According to the results of the changes of mass and density, it was found that the volume shrinkage of PVS during the curing and pyrolysis processes is 80%. The SiC obtained by pyrolysis at 1573K showed the density of 2.50g/cm$$^{3}$$ and microvickers hardness of 31.6GPa.

Journal Articles

Synchrotron radiation photoabsorption and photoemission spectroscopy for thermal-induced reoriented Si polymer

Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.323 - 326, 2005/06

 Times Cited Count:5 Percentile:27.37(Spectroscopy)

The effect of laser annealing on electronic atructures and molecular orientation for poly(dimethylsilane), {PDMS, [Si(CH$$_{3}$$)$$_{2}$$]$$_{n}$$} has been studied by synchrotron radiation photoemission and photoabsorption spectroscopy. Prior to annealing, PDMS powder was mounted on the basal plane of highly oriented pyrolytic graphite. Both Si 1s X-ray photoemission spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at Si 1s edge show that electronic structures have been modified due to annealing. Furthermore, the angle-dependent NEXAFS spectra clearly indicate that the annealed products maintain a specific orientation. Interestingly, no such kind of orientation is present in as-received PDMS powder as no angle-dependency is observed before annealing.

Journal Articles

Interactions between anionic complex species of actinides and negatively charged mineral surfaces

Yamaguchi, Tetsuji; Nakayama, Shinichi; Yoshida, Takahiro

Radiochimica Acta, 92(9-11), p.677 - 682, 2004/12

 Times Cited Count:6 Percentile:40.92(Chemistry, Inorganic & Nuclear)

Adsorption of actinides onto negatively charged mineral surfaces was investigated under conditions that actinides were predominantly present as anionic complex species: Th(CO$$_{3}$$)$$_{5}$$$$^{6-}$$, Am(CO$$_{3}$$)$$_{3}$$$$^{3-}$$, Np(CO$$_{3}$$)$$_{2}$$(OH)$$_{2}$$$$^{2-}$$, UO$$_{2}$$(OH)$$_{4}$$$$^{2-}$$, NpO$$_{2}$$(OH)$$_{2}$$$$^{-}$$, Sn(OH)$$_{5}$$$$^{-}$$ and Pb(OH)$$_{3}$$$$^{-}$$. These solutions were left to stand for 2 days to confirm these elements stable in dissolved state, and then contacted with minerals, $$gamma$$-Al$$_{2}$$O$$_{3}$$ or SiO$$_{2}$$ (AEROSIL, specific surface area: 10$$^{5}$$ m$$^{2}$$ kg$$^{-1}$$). After desired contact time for 2 days or more, the solutions were ultra-filtered through 10$$^{4}$$-molecular-weight cutoff Millipore filters and the concentrations of the elements in the filtrates were determined. The sorption experiments were performed at room temperature (25$$^{circ}$$C) under Ar. Distribution coefficients decreased with the increasing pH and with increasing carbonate concentrations. The monotonous decrease in the distribution coefficients in the investigated pH range suggests that the electrostatic repulsion was a dominant interaction between anionic complex species of actinides and negatively charged mineral surfaces.

Journal Articles

Bulk damage observed in recent LSI devices

Shindo, Hiroyuki*; Kuboyama, Satoshi*; Ikeda, Naomi*; Otomo, Hiromitsu*; Shimada, Osamu*; Hirao, Toshio; Matsuda, Sumio*

Proceedings of the 6th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-6), p.63 - 66, 2004/10

no abstracts in English

Journal Articles

Study on proton-induced single event upset in Sub-0.1$$mu$$m CMOS LSIs

Fukui, Hironobu*; Hamaguchi, Masafumi*; Yoshimura, Hisao*; Oyamatsu, Hisato*; Matsuoka, Fumitomo*; Noguchi, Tatsuo*; Hirao, Toshio; Abe, Hiroshi; Onoda, Shinobu; Yamakawa, Takeshi; et al.

Proceedings of the 6th International Workshop on Radiation Effects on Semiconductor Devices for Space Application (RASEDA-6), p.169 - 172, 2004/10

no abstracts in English

Journal Articles

Synthesis of a minute SiC product from polyvinylsilane with radiation curing, 1; Radiation curing of polyvinylsilane

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Journal of Materials Science, 39(18), p.5689 - 5694, 2004/09

 Times Cited Count:7 Percentile:30.96(Materials Science, Multidisciplinary)

Irradiation effect of $$gamma$$-ray on polyvinylsilane (PVS), which is a liquid organosilicon polymer, was investigated and the optimum curing condition to synthesize a minute SiC product with radiation curing was discussed. Room temperature and liquid nitrogen temperature (77K) were examined as the irradiation temperature. In both cases, the cured PVS maintaining its formed shape could be obtained by $$gamma$$-ray irradiation under vacuum, and the cured PVS in solid state at room temperature was obtained by irradiation with dose of above 3-4MGy. It was found that the efficiency of crosslinking in case of the irradiation at room temperature is higher than that in case of irradiation at 77K. The PVS injected into a mold was irradiated by $$gamma$$-ray with dose of 3.6MGy at room temperature under vacuum, and pyrolyzed at 1273 K in Ar gas atmosphere. As a result, minute SiC products which had similar shapes to the mold and the sizes of 30-60$$mu$$m were obtained.

Journal Articles

Propulsive Impulse Measurement of a Microwave-Boosted Vehicle in the Atmosphere

Nakagawa, Tatsuo*; Mihara, Yorichika*; Komurasaki, Kimiya*; Takahashi, Koji; Sakamoto, Keishi; Imai, Tsuyoshi

Journal of Spacecraft and Rockets, 41(1), p.151 - 153, 2004/02

 Times Cited Count:39 Percentile:88.4(Engineering, Aerospace)

A launching experiment of a microwave-boosted vehicle model was carried out using the 110GHz, 1MW gyrotoron and a propulsive inpulse to lift up the vehicle was measured. The rf power and pulse was 1MW and 0.175 $$sim$$ 0.8msec. The launching mechanism is as follows. Plasma is produced in the nozzle of the vehicle model when the rf beam is injected toward it. The plasma heated by the rf beam can produce a shock wave that gives a propulsive impulse to the vehicle. Maximum momentum coupling coefficient from the impulse to the vehicle is 395N/MW which is comparable to that of a laser boosted vehicle. The rf pulse was 0.175msec. The coupling coefficient is limitted by the gyrtron operation in pulse length and can increase if the pulse length is shorter than 0.175msec.

Journal Articles

Minute SiC products synthesized from polyvinylsilane with radiation curing

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

International Symposium in Honor of Professor K. Okamura: Collected Abstracts, 3 Pages, 2003/04

Minute SiC products were synthesized from polyvinylsilane (PVS), which is a liquid organosilicon polymer, with radiation curing. The PVS was injected into molds whose patterns were square and circle with 50$$mu$$m in side or diameter, and 10$$mu$$m in depth. The molds containing the PVS were irradiated by $$gamma$$-ray with dose of 3.6MGy at room temperature in vacuum, and heat-treated at 1273K in Ar gas atmosphere. The obtained SiC products had shapes similar to those of the molds, and the sizes of the products were about 30$$mu$$m in side or diameter.

Journal Articles

Radiation curing of polyvinylsilane as a precursor for SiC-based material

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Key Engineering Materials, 247, p.129 - 132, 2003/00

Polyvinylsilane (PVS), a liquid organosilicon polymer at room temperature, is expected to be used as a precursor for SiC product with minute and complex shape. In the synthesis of the SiC product, it is necessary to cure the polymer in order to retain the shape during the pyrolysis. We have used a radiation for curing of the PVS. However, there is a problem that the PVS foams during electron beam irradiation at room temperature. In this report, the curing of PVS by $$gamma$$-ray irradiation was examined, and effect of irradiation temperature was studied in order to find out conditions that prevent the foaming of PVS. It was found that the PVS is cured without foaming by the $$gamma$$-ray irradiation in both cases of the irradiation temperature at liquid nitrogen temperature (77K) and at room temperature. From the results of measurement of gel fraction and TGA, it was found that the PVS is cured more efficiently by the irradiation at room temperature than at 77K.

Journal Articles

Fine SiC fiber synthesized from organosilicon polymers; Relationship between spinning temperature and melt viscosity of precursor polymers

Idesaki, Akira; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Tanaka, Shigeru; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Journal of Materials Science, 36(23), p.5565 - 5569, 2001/12

 Times Cited Count:40 Percentile:78.56(Materials Science, Multidisciplinary)

A very fine silicon carbide (SiC) fiber with diameter of 6 $$mu$$ m, about a half of that of a commercially available SiC fiber, was synthesized from a polymer blend of polycarbosilane (PCS) and polyvinylsilane (PVS). The fine SiC fiber was obtained by optimizing the composition and the spinning temperature of PCS-PVS polymer blends. In order to determine these optimum conditions, the relationship between temperature and melt viscosities of the polymer blends was investigated. As a result, it was found that the optimum spinning temperature range was within a temperature range where the melt viscosity is 5-10Pa$$cdot$$s. Moreover, by blending PVS with PCS, the spinning temperature of the polymer blends was lowered, the spinnability of polymer system was improved, and finer polymer fiber was obtained compared with PCS. The optimum content of PVS in the polymer blend was 15-20wt%.

Journal Articles

Development of SiC/SiC composites from Si-based polymer blend by radiation application

Sugimoto, Masaki; Tanaka, Shigeru; Ito, Masayoshi*; Okamura, Kiyohito*

High Temperature Ceramic Matrix Composites, p.357 - 361, 2001/10

no abstracts in English

Journal Articles

Fine silicon carbide fibers synthesized from polycarbosilane-polyvinylsilane polymer blend using electron beam curing

Idesaki, Akira*; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Journal of Materials Science, 36(2), p.357 - 362, 2001/01

 Times Cited Count:15 Percentile:53.63(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Fine silicon carbide fiber synthesized from a silicon-based polymer blend using radiation curing

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Morita, Yosuke; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

High Temperature Ceramic Matrix Composites, p.35 - 40, 2001/00

Silicon carbide (SiC) fiber, which is one of the likeliest candidates as a reinforcement fiber of ceramic matrix composites (CMCs), is synthesized from polycarbosilane (PCS). The diameter of thus SiC fibers is 10-15 $$mu$$m. In order to fabricate CMCs with 3-dimensional complex shapes, it is important to develop a SiC fiber with diameter of less than 10 $$mu$$m, flexibility, and high strength. In order to improve the spinnability of precursor polymer, we have blended polyvinylsilane (PVS), which is a liquid polymer at room temperature, to PCS as a spinning additive. According to relationship between temperature and melt viscosity of the polymer blend, it was found that the polymer can be melt-spun at about 490K, 110K lower than PCS (about 600K), and that the spinnability of the polymer is improved by blending PVS. Fine polymer fiber was obtained from the polymer blend, and finally, very fine SiC fiber with the average diameter of 6 $$mu$$m was synthesized from the PCS-PVS polymer blend.

55 (Records 1-20 displayed on this page)