Magnetic and electronic properties of (LaMnO)(SrMnO) superlattice revealed by resonant soft X-ray scattering

Kubota, Masato; Yamada, Hiroyuki*; Nakao, Hironori*; Okamoto, Jun*; Yamasaki, Yuichi*; Sawa, Akihito*; Murakami, Yoichi*

Japanese Journal of Applied Physics, 53(5S1), p.05FH07_1 - 05FH07_5, 2014/05

https://doi.org/10.7567/JJAP.53.05FH07

A Study on flow field of purge gas for tritium transfer through breeder pebble bed in fusion blanket

Seki, Yohji; Ezato, Koichiro; Yokoyama, Kenji; Enoeda, Mikio; Kubota, Jinichi*; Sakamoto, Kensaku

Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 8 Pages, 2012/12

Japan Atomic Energy Agency has been performing R&D and design of a blanket module of a nuclear fusion reactor. Pebbles of a ceramic tritium breeder are packed in a container of the blanket. Helium purge gas is applied as a transport fluid in a tritium recovery system. Prediction of the flow phenomena with a tritium transfer is important for designs of the container. A purpose of our research is to establish and verify a method for a prediction of the flow in the pebble bed. In this study, pressure drops of the helium purge gas through the pebble bed were measured up to 100 L/min of flow rate. Reliability of prediction ability of the pressure drop was validated by this experiment within the flow rate which is less than 40 L/min. A numerical simulation for the flow field through the pebble bed also has been performed. Consequently, the velocity distributions are quantitatively and qualitatively obtained at near the wall and the center region in the pebble bed.

Comparative study on the preparation and properties of radiation-grafted polymer electrolyte membranes based on fluoropolymer films

Chen, J.; Septiani, U.*; Asano, Masaharu; Maekawa, Yasunari; Kubota, Hitoshi*; Yoshida, Masaru

Journal of Applied Polymer Science, 103(3), p.1966 - 1972, 2007/03

https://doi.org/10.1002/app.24950

In this study, ETFE and PVDF films, together with the crosslinked PTFE (cPTFE) films have been compared on the basis of their preparation and properties of radiation-grafted polymer electrolyte membranes (PEM). The proton conductivity and chemical stability of the three types of membranes with the similar ion exchange capacity near 1.0 mmolg were investigated and discussed in detail. Although the ETFE-based PEM was relatively more stable, its proton conductivity was lower than those of the PVDF- and cPTFE-based membranes. On the other hand, the cPTFE-based membrane showed the significantly higher proton conductivity, but its chemical stability was shorter than that of the ETFE-based membrane. The difference in the preparation and properties of the PEMs was due to the difference in the crystallinity and intrinsic properties of the base films.

Influence of pre-irradiation atmosphere on the properties of polymer electrolyte membranes prepared using radiation grafting method

Septiani, U.*; Chen, J.; Asano, Masaharu; Maekawa, Yasunari; Yoshida, Masaru; Kubota, Hitoshi*

Journal of Materials Science, 42(4), p.1330 - 1335, 2007/02

https://doi.org/10.1007/s10853-006-1196-z

The influence of pre-irradiation atmosphere, argon and air, on radiation grafting of styrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and the properties of the ETFE-based radiation-grafted polymer electrolyte membranes were investigated. The preparation and properties of the membranes were found to be strongly influenced by the -ray pre-irradiation atmosphere. The proton conductivity was measured in its water-saturated state at 25C, and the membrane durability was tested in a 3 % HO aqueous solution at 60C. The proton conductivity of the membrane prepared by pre-irradiation under air was higher than that of the membrane prepared under argon with the same ion exchange capacity level. However, the durability of the former was considerably lower than that of the latter. For instance, the membrane with an ion exchange capacity of about 1.0 mmolg-1 prepared under argon was twice as durable as that prepared under air. It was considered that the lower durability of the membrane prepared by pre-irradiation under air was because of the unstable ether bond introduced between the graft chains and the backbone chains. : polymer electrolyte membrane (PEM); radiation grafting; styrene; durability; ETFE

Nano-structure controlled polymer electrolyte membranes for fuel cell applications prepared by ion beam irradiation

Yamaki, Tetsuya; Kozone, Yuichi; Hiroki, Akihiro; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru

ECS Transactions, 3(1), p.103 - 112, 2006/00

https://doi.org/10.1149/1.2356129

Fluoropolymer-based electrolyte membranes for water electrolyzers and fuel cells were prepared by using heavy ion beams from the cyclotron accelerator. The preparation method for these so-called "nano-scale structure-controlled membranes" involves (1) the swift heavy ion irradiation of polyvinylidene fluoride films and subsequent chemical etching to obtain cylindrical pores with a diameter of 100 nm, and (2) the filling of proton-conducting polymer chains into the etched pores by -ray-induced graft polymerization. The proton transport only in the thickness direction was observed for the resulting membranes with controlled ion exchange capacities, indicating the formation of one-dimensional straight proton-conducting pathways parallel to the ion-beam incident axis. The membranes exhibited a lower water uptake and reduced methanol permeability compared to commercially-available Nafion probably due to the restricted structures.

Polytetrafluoroethylene-based proton-conducting membranes prepared by ultraviolet-induced photografting

Chen, J.; Asano, Masaharu; Maekawa, Yasunari; Sakamura, Takahiro*; Kubota, Hitoshi*; Yoshida, Masaru

Electrochemical and Solid-State Letters, 9(11), p.G326 - G329, 2006/00

https://doi.org/10.1149/1.2344827

A novel process comprising UV-induced photografting of styrene into PTFE films and subsequent sulfonation has been developed for preparing proton-conducting membranes. The significance of this process is that the graft chains can penetrate throughout the PTFE base films; the resultant sulfonated electrolyte membrane with a low degree of grafting near 7% shows higher proton conductibility and better mechanical properties, similar to those of Nafion membrane. Furthermore, the performances of the UV-photografted electrolyte membranes are better as compared to those of the radiation grafted electrolyte membranes.

Preparation of proton exchange membranes based on crosslinked polytetrafluoroethylene for fuel cell applications

Yamaki, Tetsuya; Kobayashi, Kazuhiro; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru

Polymer, 45(19), p.6569 - 6573, 2004/09

https://doi.org/10.1016/j.polymer.2004.07.048

We prepared proton exchange membranes by the -ray-induced post grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. The degree of grafting was controlled in the range of 7-75% by the crosslinking density of the PTFE matrix as well as the grafting conditions. Under our preparation conditions, the films at the grafting yield of 30% were found to produce ion exchange membranes with a homogeneous distribution of sulfonic acid groups. The resulting membranes showed a large ion exchange capacity up to 2.9 meq g, which exceeded the performance of commercially-available perfluorosulfonic acid films such as Nafion; nevertheless, they appeared to be dimensionally stable in water. These should undoubtedly result from the use of the crosslinked PTFE films as graft substrates and make our ion exchange membranes promising for applications to polymer electrolyte fuel cells.

Radiation grafting of styrene into crosslinked PTEE films and subsequent sulfonation for fuel cell applications

Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Morita, Yosuke; Suwa, Takeshi; Chen, J.*; Tsubokawa, Norio*; Kobayashi, Kazuhiro*; Kubota, Hitoshi*; Yoshida, Masaru

Radiation Physics and Chemistry, 67(3-4), p.403 - 407, 2003/08

https://doi.org/10.1016/S0969-806X(03)00075-6

no abstracts in English

Permeation of p-nitrophenol through N-isopropylacrylamide-grafted etched-track membrane close to -point temperature

Hiroki, Akihiro*; Yoshida, Masaru; *; Asano, Masaharu; N.Reber*; R.Spohr*; Kubota, Hitoshi*; Katakai, Ryoichi*

Radiat. Eff. Defects Solids, 147, p.165 - 175, 1999/00

no abstracts in English

Reversible on-off switch function of ion-track pores for thermo-responsive films based on copolymers consisting of diethyleneglycol-bis-allylcarbonate and acryloyl-L-proline methyl ester

Yoshida, Masaru; Nagaoka, Noiyasu*; Asano, Masaharu; Omichi, Hideki; Kubota, Hitoshi*; Ogura, K.*; Vetter, J.*; Spohr, R.*; Katakai, Ryoichi*

Journal of Nuclear Materials, 122(1), p.39 - 44, 1997/00

no abstracts in English