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Kishi, Hirofumi*; Sakamoto, Tomokazu*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Kato, Takeshi*; Zulevi, B.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Matsumura, Daiju; et al.
Nanomaterials (Internet), 8(12), p.965_1 - 965_13, 2018/12
Times Cited Count：11 Percentile：48.30(Chemistry, Multidisciplinary)Kusano, Shogo*; Matsumura, Daiju; Asazawa, Koichiro*; Kishi, Hirofumi*; Sakamoto, Tomokazu*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Mizuki, Junichiro*
Journal of Electronic Materials, 46(6), p.3634 - 3638, 2017/06
Times Cited Count：3 Percentile：19.58(Engineering, Electrical & Electronic)Sakamoto, Tomokazu*; Matsumura, Daiju; Asazawa, Koichiro*; Martinez, U.*; Serov, A.*; Artyushkova, K.*; Atanassov, P.*; Tamura, Kazuhisa; Nishihata, Yasuo; Tanaka, Hirohisa*
Electrochimica Acta, 163, p.116 - 122, 2015/05
Times Cited Count：57 Percentile：83.30(Electrochemistry)Asazawa, Koichiro*; Kishi, Hirofumi*; Tanaka, Hirohisa*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Saputro, A. G.*; Nakanishi, Hiroshi*; Kasai, Hideaki*; Artyushkova, K.*; et al.
Journal of Physical Chemistry C, 118(44), p.25480 - 25486, 2014/11
Times Cited Count：15 Percentile：44.58(Chemistry, Physical)Sakamoto, Tomokazu*; Asazawa, Koichiro*; Martinez, U.*; Halevi, B.*; Suzuki, Toshiyuki*; Arai, Shigeo*; Matsumura, Daiju; Nishihata, Yasuo; Atanassov, P.*; Tanaka, Hirohisa*
Journal of Power Sources, 234, p.252 - 259, 2013/07
Times Cited Count：68 Percentile：86.84(Chemistry, Physical)Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
ECS Transactions, 50(2), p.2075 - 2081, 2012/10
no abstracts in English
-ray pre-irradiation graftingKoshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.240 - 241, 2011/06
The anion-exchange membranes (AEM) for fuel cells were prepared by the radiation-induced graft polymerization of chloromethylstyrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization of the grafts with trimethylamine. When the AEM were treated in 1M-KOH and washed with N
-saturated water, the membranes with chloride form can be converted quantitatively to hydroxide form. However, the hydroxide form was easily converted to the bicarbonate form by the treatment in non-bubbled (CO dissolved) water. When we introduced the crosslinkers in polymer grafts, which is proved to be very effective in the proton conducting PEM having a poly(styrenesulfonic acid) grafts, the grafted AEM with both chloride and hydroxide forms showed only slight decrease of water uptake. It should be noted that AEM with hydroxide form showed very high tendency to absorb water.
Asazawa, Koichiro*; Yamamoto, Kazuya*; Yamada, Koji*; Tanaka, Hirohisa*; Matsumura, Daiju; Tamura, Kazuhisa; Nishihata, Yasuo; Atanassov, P.*
ECS Transactions, 33(1), p.1751 - 1755, 2010/10
CoPPyC were analyzed with X-ray adsorption fine structure (XAFS) measurements. Acid-treated CoPPyC (CoPPyC-AT) has higher activity than PPyC for oxygen reduction reaction. From the analysis of EXAFS of Co, CoPPyC electrocatalysts as synthesized consist of two peaks. The peak around 1.6 
was assigned to Co-N and/or Co-O shells. The second peak around 2.6 was assigned to Co-O-Co shells originated from cobalt hydroxide. CoPPyC-AT showed only one peak of assigned to Co-N and/or Co-O, and it indicates that cobalt hydroxide is removed by acid treatment. It is clear that a coexistence of cobalt and nitrogen in CoPPyC-AT shows specific performance, and pyrolysis is not necessary to make correlation of Co-N.
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on -ray crosslinked ethylene-tetrafluoroethylene copolymer (ETFE) by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. Little effect of radiation crosslinking was observed for the degree of CMS grafting and the quaternization ratio. Interestingly, however, the crosslinking structure in ETFE was found to lower water uptake of the resulting membranes in the OH form, thereby restricting excessive swelling during hydrazine-fuel-cell operation.
-ray pre-irradiation grafting; Effect of the structure of quaternary ammonium ionsKoshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We investigated the effect of the length of the linear chain on the structure of quaternary ammonium ions on the membrane properties such as durability of ion conductivity. Graft polymerization was performed by immersing the pre-irradiated ETFE film in the CMS solution. The ETFE-g-CMS film was then quaternized in four different tertiary amines, that is, trimethylamine (n = 1), dimethylethylamine (n = 2), n-butyldimethylamine (n = 4) and n-hexyldimethylamine (n = 6) solutions. The n dependence of the OH
conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution. When n increased from 1 to 6, the OH conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. The chemical durability seemed to increase eight-fold at the same time. The chemical attack by hydroxyl radicals on the quaternary ammonium ions would be controlled by hydrophobicity and steric hindrance of the alkyl group.
Maekawa, Yasunari; Sinnananchi, W.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yamamoto, Kazuya*; Sampei, Fumihiro*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non precious metals are used as a electrode catalyst, were prepared using radiation techniques. The grafted AEM were prepared by the radiation-induced graft polymerization of chloromethylstyrene (CMS) into poly(ethylene-co-tetrafluoroethylene) (ETFE) films and subsequent quaternization of the grafts with trimethylamine. When the grafted AEM were treated in 1M-KOH and washed with N-saturated water, the membranes with chloride form (ETFE-TMAMS(Cl)) can be converted quantitatively to hydroxide form (ETFE-TMAMS(OH)) without the formation of the bicarbonate form. The grafted AEM with IEC of 2.0 mmol/g showed the maximum power density of more than 300 mW/cm
with stability for 400 hours under the operation at 80
C.
Yoshimura, Kimio; Sinnananchi, W.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamaguchi, Susumu*; Yamamoto, Kazuya*; Asazawa, Koichiro*; Yamada, Koji*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Yoshimura, Kimio; Sinananwanich, W.*; Koshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
Maekawa, Yasunari; Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non precious metals are used as an electrode catalyst, have been developing by radiation techniques. AEMs having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole or the copolymerizaiton with styrene onto ETFE film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 80 C. The AEM consisting of the homopolymer grafts showed alkaline stability at 80 C for ca. 150 hours. In contrast, the copolymer (1:1 molar ratio) grafts type AEM kept its ion conductivity above 10 mS/cm in 1M KOH at 80 C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on an ethylene-tetrafluoroethylene copolymer by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. The crosslinker effect was investigated in terms of membrane preparation and performance of a hydrazine fuel cell. The quaternization ratio appeared to decrease as the concentration of divinylbenzene (DVB) in the CMS grafting solution increased. Importantly, the crosslinker lowered the water uptake of the resulting membranes in the Cl and OH forms, possibly thereby restricting excessive swelling during the fuel-cell operation.
-ray pre-irradiation grafting; Effect of the structure of quaternary ammonium ionsKoshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We investigated the effect of a linear carbon chain length (n) in quaternary ammonium ions, on the durability of ion conductivity of anion exchange membrane. The poly(ethylene-co-tetrafluoroethylene) grafted chloromethylstyrene film was quaternized in four different tertiary amines, that is, trimethylamine (n=1), dimethylethylamine (n=2), n-butyldimethylamine (n=4) and n-hexyldimethylamine (n=6) solutions. The n dependence of ion conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution (3% hydrogen peroxide+ 4 ppm iron sulfate) at 80 C for 2 h. When n increased from 1 to 6, the ion conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. Interestingly, the chemical durability seemed to increase eight-fold at the same time. The chemical attack by hydroxyl radicals on the quaternary ammonium ions would be controlled by hydrophobicity and steric hindrance of the alkyl group.
