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Journal Articles

Effects of alumina powder characteristics on H$$_{2}$$ and H$$_{2}$$O$$_{2}$$ production yields in $$gamma$$-radiolysis of water and 0.4M H$$_{2}$$SO$$_{4}$$ aqueous solution

Yamada, Reiji; Kumagai, Yuta

International Journal of Hydrogen Energy, 37(18), p.13272 - 13277, 2012/09

 Times Cited Count:5 Percentile:18.71(Chemistry, Physical)

The effects of powder characteristics on H$$_{2}$$ and H$$_{2}$$O2 productions in $$^{60}$$Co $$gamma$$-radiolysis were studied in pure water and in 0.4M H$$_{2}$$SO$$_{4}$$ aqueous solutions containing alumina powders. In 0.4 M H$$_{2}$$SO$$_{4}$$ solution, the H$$_{2}$$ yields strongly depended on alumina structures and decreased in the order of $$alpha$$, $$theta$$, $$gamma$$ alumina, although the specific surface areas increased as $$alpha$$, $$theta$$, $$gamma$$. The yields increased with increasing specific surface area when compared am-alumina. In pure water, similar dependence was observed but not as strong as that for 0.4 M H$$_{2}$$SO$$_{4}$$ solution. The H$$_{2}$$O$$_{2}$$ yields were strongly decreased by adding the alumina powders in both water and 0.4 M H$$_{2}$$SO$$_{4}$$ aqueous solution, although the amounts of decrease were almost neither correlated with specific surface areas nor structures. The enhancing H$$_{2}$$ production was discussed in terms of the electron supply from alumina to aqueous solution as well as the adsorption of OH radicals on alumina surfaces.

Journal Articles

Effect of alumina on the enhancement of hydrogen production and the reduction of hydrogen peroxide in the $$gamma$$-radiolysis of pure water and 0.4M H$$_{2}$$SO$$_{4}$$ aqueous solution

Yamada, Reiji; Kumagai, Yuta; Nagaishi, Ryuji

International Journal of Hydrogen Energy, 36(18), p.11646 - 11653, 2011/09

 Times Cited Count:7 Percentile:22.28(Chemistry, Physical)

The H$$_{2}$$ and H$$_{2}$$O$$_{2}$$ produced by $$^{60}$$Co $$gamma$$-radiation at room temperature were measured in pure water and 0.4M H$$_{2}$$SO$$_{4}$$ aqueous solution with alumina powder. By increasing the addition of alumina powder, a strong reduction of H$$_{2}$$O$$_{2}$$ concentrations in the solutions was obtained, and the final product H$$_{2}$$ yields were correspondingly enhanced. These enhancement and reduction effects were diminished in the subsequent $$gamma$$-radiation when irradiated alumina powder was used. The effects were reversibly restored by washing the irradiated powder with purified water. In 0.4M H$$_{2}$$SO$$_{4}$$ solution with alumina powder, the H$$_{2}$$ yields increased by increasing the absorbed dose rate in the region of 1-5 kGy/hr. The radiation-enhanced H$$_{2}$$ production correlated with the reduction of H$$_{2}$$O$$_{2}$$ concentration could be brought about by the reduction of H$$_{2}$$O$$_{2}$$ molecules and OH radicals in the solutions due to alumina powder.

Journal Articles

Basic and application studies on chemical responses to quantum beams in heterogeneous systems

Nagaishi, Ryuji; Yamada, Reiji; Kumagai, Yuta; Sugo, Yumi

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 160, 2008/11

no abstracts in English

JAEA Reports

Development of production methods of the Sr-90/Y-90 source for hydrogen production experiments

Motoki, Riyozo; Aoki, Hiromichi; Uchida, Shoji; Nagaishi, Ryuji; Yamada, Reiji

JAEA-Technology 2008-014, 23 Pages, 2008/03

JAEA-Technology-2008-014.pdf:9.05MB

The study of producing hydrogen with a Sr-90/Y-90 source is planned to utilze the radioactive waste effectively. Therefore we developed two methods of caking Sr-90 and a catalyst for the production of hydrogen effectively. One is a method of caking $$^{90}$$SrTiO$$_{3}$$ and TiO$$_{2}$$ in a silica gel. And another is a method of caking $$^{90}$$SrSO$$_{4}$$ and TiO$$_{2}$$ in a silica gel. These solid matters are porous materials, which has a radiation resistant and chemical resistant. In addition, Y-90 which is a daughter nuclide of Sr-90 can be also used for hydrogen production.

Journal Articles

Basic and application studies on chemical responses to quantum beams in heterogeneous systems

Nagaishi, Ryuji; Yamada, Reiji; Aoyagi, Noboru; Sugo, Yumi

JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 161, 2008/03

From the standpoints of utilization of radioactive wastes, and of sophistication of separation process of spent fuels, we have been investigating promotion or inhibition of radiation-induced reactions in immiscible heterogeneous systems: solutions coexisting/contacting with solid oxides, solvent system with aqueous and organic phases, etc.. We have recently report that the reactions of reduction of metal ions and of hydrogen production in aqueous solution were promoted by adding oxide particles to the solution, and that the radiolysis of amides in n-dodecane was dependent on aqueous solution contacting with the n-dodecane. In this report, we illustrate recover of platinum-group elements from aqueous solution, and non-toxic treatment of chrysotile asbestos using ionizing radiations as the experimental results found in fiscal 2006.

Journal Articles

Hydrogen production in the $$gamma$$-radiolysis of aqueous sulfuric acid solutions containing Al$$_{2}$$O$$_{3}$$, SiO$$_{2}$$, TiO$$_{2}$$ or ZrO$$_{2}$$ fine particles

Yamada, Reiji; Nagaishi, Ryuji; Hatano, Yoshihiko; Yoshida, Zenko

International Journal of Hydrogen Energy, 33(3), p.929 - 936, 2008/02

 Times Cited Count:14 Percentile:37.21(Chemistry, Physical)

Hydrogen production was studied in the $$gamma$$-radiolysis of aqueous H$$_{2}$$SO$$_{4}$$ solutions containing oxide powder of Al$$_{2}$$O$$_{3}$$, SiO$$_{2}$$, TiO$$_{2}$$ or ZrO$$_{2}$$. The observed yields of final product H$$_{2}$$ increased with relative amounts of oxide powder in the solutions and exhibited a particular H$$_{2}$$SO$$_{4}$$ concentration dependence, which was different for each oxide species and its amount. The addition of a small amount of CH$$_{3}$$OH to a H$$_{2}$$SO$$_{4}$$ aqueous solution with oxide powder was quite effective for increasing the final product yields of H$$_{2}$$. The obtained results revealed that heterogeneous systems composed of oxide powder and aqueous H$$_{2}$$SO$$_{4}$$ solution were more efficient for producing H$$_{2}$$ molecules in $$gamma$$-radiolysis than homogeneous systems without oxides.

Journal Articles

Mechanical properties of SiC/SiC composite with magnesium-silicon oxide interphase

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Journal of Nuclear Materials, 367-370(1), p.725 - 729, 2007/08

 Times Cited Count:10 Percentile:57.83(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Hydrogen production and morphological change of chrysotile asbestos in the radiolysis of aqueous solutions

Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji

Chemistry Letters, 36(7), p.890 - 891, 2007/07

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

A high yield of H$$_{2}$$ gas was unprecedentedly produced due to the radiolysis of water containing asbestos while the morphology of them turned fibrous bundles into non-fibrous particles in 0.40 M H$$_{2}$$SO$$_{4}$$ solution over 2.0 MGy dose of irradiation. In conclusion, irradiation against asbestos in solutions can promote the hydrogen gas production and cause the morphological change of chrysotile without providing heat or chemicals.

Journal Articles

Radiation-induced catalytic reduction of chromium(VI) in aqueous solution containing TiO$$_{2}$$, Al$$_{2}$$O$$_{3}$$ or SiO$$_{2}$$ fine particles

Nagaishi, Ryuji; Yoshida, Zenko; Yamada, Reiji; Hatano, Yoshihiko

Radiation Physics and Chemistry, 75(9), p.1051 - 1054, 2006/09

 Times Cited Count:7 Percentile:48.03(Chemistry, Physical)JP, H17-065162   Licensable Patent Information Database   Patent publication (In Japanese)

Reduction of chromium(VI) in aqueous neutral or basic solution was promoted by $$gamma$$-ray irradiation in the presence of oxide particles such as TiO$$_{2}$$, Al$$_{2}$$O$$_{3}$$ or SiO$$_{2}$$. The oxide particles behaved as a catalyst, and the efficiency of the Cr(VI) reduction increased with an increase of the irradiation dose irrespective of the initial Cr(VI) concentration. The insoluble Cr(III) oxide formed through the Cr(VI) reduction also acted as the catalyst.

Journal Articles

Effect of thick SiC interphase layers on microstructure, mechanical and thermal properties of reaction-bonded SiC/SiC composites

Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Jitsukawa, Shiro

Journal of Physics and Chemistry of Solids, 66(2-4), p.576 - 580, 2005/02

 Times Cited Count:46 Percentile:83.43(Chemistry, Multidisciplinary)

SiC/SiC composites are expected to be one of the candidate materials for fusion reactors because of the low radioactivity after neutron irradiation and excellent mechanical properties at high temperature. Reaction-Bonding (RB) process was employed since this process has a possibility of producing a much denser matrix compared with other processes. SiC fibers, however, adhere strongly to the matrix because of high reactiveness of molten Si with the SiC fiber during RB process. In this study, we investigated the effects of SiC layer as an interphase on fracture behavior in the SiC/SiC. The specimen without an interphase layer showed catastrophic failure behavior while the specimen with SiC interphase layer exhibited non-catastrophic failure behavior by 3-point bending testing. The microstructure observation indicated that SiC fibers did not adhere to the matrix in the specimen with SiC interpahse layer. After 3-point bending testing, the pull-out phenomenon occurred in the SiC/SiC with SiC interphase layer while did not occur in the composite without interphase layer.

Journal Articles

Preparation and characterization of magnesium-silicon based oxide coating on high-crystalline SiC fiber as an interphase in SiC/SiC composite

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings, Vol.26, No.2, p.27 - 34, 2005/00

no abstracts in English

Journal Articles

Thermal diffusivity/conductivity of Tyranno SA fiber- and Hi-Nicalon type S fiber-reinforced 3-D SiC/SiC composites

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu

Journal of Nuclear Materials, 329-333(Part1), p.497 - 501, 2004/08

 Times Cited Count:24 Percentile:82.19(Materials Science, Multidisciplinary)

SiC fiber reinforced SiC composites (SiC/SiC) have a potential for a structural material for a blanket wall of advanced fusion reactors. To reduce thermal stresses in the wall under heavy thermal loads SiC/SiC composites are expected to have high thermal conductivity as possible. Advanced SiC fibers recently developed, such as Tyranno SA and Hi-Nicalon Type S have been employed for weaving 3D textures as well as those 2D unwoven fabrics. The CVI and PIP/CVI fabrication methods were used. The thermal conductivity at RT was 40-50 W/mK and 35-40 W/mK for Tyranno CVI and PIP/CVI composites, respectively, whereas about 25 and about 17 W/mK at 1000 $$^{circ}$$C. 2D unwoven CVI composites had less than 12 W/mK for RT-1000 $$^{circ}$$C. For Hi-Nicalon Type S, 3D CVI composites had about 35 and about 20 for RT and 1000 $$^{circ}$$C, respectively. The reason of these high thermal conductivities was ascribed to higher density as well as better SiC crystallinity. The fiber configuration effects on the thermal conductivity of SiC/SiC composites were dominant in the low temperature region.

Journal Articles

Preparation of silicon-based oxide layer on high-crystalline SiC fiber as an interphase in SiC/SiC composites

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro

Journal of Nuclear Materials, 329-333(Part1), p.554 - 557, 2004/08

 Times Cited Count:4 Percentile:30.82(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Highly thermal conductive sintered SiC fiber-reinforced 3D SiC/SiC composites; Experiments and finite-element analysis of the thermal diffusivity/conductivity

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu; Jitsukawa, Shiro

Journal of Nuclear Materials, 307-311(Part2), p.1215 - 1220, 2002/12

 Times Cited Count:20 Percentile:77.82(Materials Science, Multidisciplinary)

SiC fiber-reinforced SiC composites (SiC/SiC) are considered an advanced structural material for blanket modules of a fusion reactor, which requires high thermal conductivity in order to keep thermal stresses in the material lower than the allowable design stress. The sintered SiC fiber recently developed has obtained high thermal conductivity, so it is highly expected that sintered SiC fiber-reinforced SiC/SiC composites would also show high thermal conductivity. In this study several types of 3D SiC/SiC composites were fabricated by either CVI or PIP method. The results of the thermal conductivity measurements show that the maximum thermal conductivity at room temperature was about 60 W/mK for CVI composites or 25W/mK for PIP ones. These values are considerably higher than those of non-sintered SiC fiber reinforced SiC/SiC composites, which indicates a possibility that the developed materials would be promising. The FEM thremal analysis shows the good agreement between the caluculated and experimental results.

Journal Articles

Progress in blanket designs using SiC$$_{f}$$/SiC composites

Giancarli, L.*; Golfire, H.*; Nishio, Satoshi; Raffray, R.*; Wong, C.*; Yamada, Reiji

Fusion Engineering and Design, 61-62, p.307 - 318, 2002/11

 Times Cited Count:53 Percentile:94.77(Nuclear Science & Technology)

no abstracts in English

Journal Articles

A Finite-element analysis of the thermal diffudivity/conductivity of SiC/SiC composites

Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu

Advanced SiC/SiC Ceramic Composites: Developments and Applications in Energy Systems; Ceramic Transactions Vol. 144, p.289 - 299, 2002/00

A Finite-element method(FEM) was applied for a computer simulation of a laser flash method for measuring thermal diffusivity of SiC/SiC composites. To understand the effect of individual fiber and matrix thermal conductivities as well as fiber volume on the overall composite's thermal diffusivity, the cases of high and low values for the fiber and matrix thermal conductivities were calculated as a function of fiber volume fraction at specimen temperatures of 200 and 900$$^{circ}C$$. The results of calculations showed that if low thermal conductive SiC fibers were used, the increase of fiber volume worsened the composite thermal diffusivity with highly conductive matrix, whereas when using highly conductive SiC fiber, the effect of increasing fiber volume was positive for increasing the composite diffusivity with low matrix thermal conductivity. The specimen temperatures altered the values of the composite thermal diffusivity but the qualitative tendencies above mentioned were maintained.

Journal Articles

Mechanical and thermal properties of dense SiC/SiC composite fabricated by reaction-bonding process

Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Futakawa, Masatoshi; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings (25th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A), 22(3), p.533 - 538, 2001/03

no abstracts in English

Journal Articles

Mechanical and thermal properties of 2-D and 3-D SiC/SiC Composites

Yamada, Reiji; Taguchi, Tomitsugu; Igawa, Naoki

Journal of Nuclear Materials, 283-287(Part.2), p.574 - 578, 2000/12

 Times Cited Count:58 Percentile:95.74(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Physics design of advanced steady-state tokamak reactor A-SSTR 2

Nishio, Satoshi; Ushigusa, Kenkichi; Ueda, Shuzo; Polevoi, A.*; Kurita, Genichi; Tobita, Kenji; Kurihara, Ryoichi; Hu, G.; Okada, Hidetoshi*; Murakami, Yoshiki*; et al.

JAERI-Research 2000-029, 105 Pages, 2000/10

JAERI-Research-2000-029.pdf:4.19MB

no abstracts in English

Journal Articles

Mg-Si-Al-O coatings on Hi-Nicalon SiC fiber by Alkoxide method

Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Jitsukawa, Shiro

Ceramic Engineering and Science Proceedings (24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: B), 21(4), p.237 - 242, 2000/09

no abstracts in English

83 (Records 1-20 displayed on this page)