Sawada, Shinichi*; Kimura, Takehiro*; Nishijima, Haruyuki*; Kodaira, Takahide*; Tanaka, Nobuyuki; Kubo, Shinji; Imabayashi, Shinichiro*; Nomura, Mikihiro*; Yamaki, Tetsuya*
International Journal of Hydrogen Energy, 45(27), p.13814 - 13820, 2020/05
An electrochemical membrane Bunsen reaction using a cation exchange membrane (CEM) is a key to achieving an iodine-sulfur (IS) thermochemical water splitting process for mass-production of hydrogen. In this study, we prepared both the radiation-grafted CEM with a high ion exchange capacity (IEC) and the highly-porous Au-electroplated anode, and then used them for the membrane Bunsen reaction to reduce the cell overvoltage. The high-IEC grafted CEM exhibited low resistivity for proton transport, while the porous Au anode had a large effective surface area for anodic SO oxidation reaction. As a result, the cell overvoltage for the membrane Bunsen reaction was significantly reduced to 0.21 V at 200 mA/cm, which was only one-third of that of the previous test using the commercial CEM and non-porous anode. From the analysis of the current-voltage characteristics, employment of the grafted CEM was found to be more effective for the overvoltage reduction compared to the porous Au anode.
Kitamura, Akane; Yamaki, Tetsuya*; Yuri, Yosuke*; Koshikawa, Hiroshi*; Sawada, Shinichi*; Yuyama, Takahiro*; Usui, Aya; Chiba, Atsuya*
Nuclear Instruments and Methods in Physics Research B, 460, p.254 - 258, 2019/12
Poly(vinylidene-fluoride) (PVDF) film is suitable for investigation of the size of etchable ion tracks because we can clearly judge the finish of the track etching and the surrounding bulk area remains due to the high chemical stability. Thereby we can measure the radius of ion tracks of each ion. In this study, we focused on two irradiation conditions for controlling the size of etchable ion tracks of PVDF films. One was irradiation in an oxygen atmosphere and the other was a fullerene (C) cluster beam irradiation. SEM observation showed that the size of pores became larger by irradiation in an oxygen atmosphere. It was found that the oxidation of ion tracks widened the size of etchable ion tracks. The C irradiation caused larger etchable tracks on the PVDF surface. The result could represent the effect of local and simultaneous collisions by the swift aggregated ions.
Inagaki, Yoshiyuki; Sakaba, Nariaki; Tanaka, Nobuyuki; Nomura, Mikihiro*; Sawada, Shinichi*; Yamaki, Tetsuya*
Nippon Kaisui Gakkai-Shi, 73(4), p.194 - 202, 2019/08
The thermochemical IS process is a promising hydrogen production method which can produce hydrogen in a large amount and stably with high efficiency by thermal splitting of water. Research and development on chemical reaction technology with membranes was conducted for the purpose of improving the efficiency of IS process and application of solar heat. The basic technology of ceramic membranes applied to decomposition reactions of hydrogen iodine and sulfuric acid was developed, and it is expected that the conversion rate on decomposition in each reaction can be remarkably improved. The basic technology of a cation exchange membrane applied to Bunsen reaction was developed with radiation-induced grafting technique, it is expected that the amount of iodine can be reduced to about one-fifth compared to the conventional method. These achievements are important technologies for practical use of the IS process.
Sawada, Shinichi*; Yasukawa, Masahiro*; Koshikawa, Hiroshi*; Kitamura, Akane; Higa, Mitsuru*; Yamaki, Tetsuya*
Nippon Kaisui Gakkai-Shi, 73(4), p.208 - 216, 2019/08
For applications to saline water concentration by electrodialysis, we prepared nano-structure-controlled cation and anion exchange membranes (CEMs and AEMs) by a so-called ion-track grafting technique. This new technique involves irradiation of a polymer substrate with an MeV-GeV heavy-ion beam to form the nano-sized cylindrical ion tracks and the graft polymerization only into the ion tracks for the creation of one-dimensional transport pathways. A 25-m-thick poly(ethylene-co-tetrafluoroethylene) film was irradiated with 560 MeV Xe or 310 MeV Kr. The irradiated films were immersed in grafting solutions of ethyl p-styrenesulfonate (EtSS) and chloromethylstyrene (CMS),and then subjected to the hydrolysis of EtSS units and quaternization of CMS units to prepare CEMs and AEMs, respectively. These CEMs and AEMs showed lower resistance than the commercially-available membranes even at the very low water uptake. This would be due to the signifcantly-effcient transport of ions through the unique one-dimensional highly-connected transport pathways. In the saline water concentration experiment, a pair of our CEM and a commercial AEM or vice versa led to a higher salt concentration in the concentration chamber than did a pair of the commercial membranes. This result demonstrated great applicability of our ion-track-grafted CEMs and AEMs for saline water concentration.
Myagmarjav, O.; Iwatsuki, Jin; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Ioka, Ikuo; Kubo, Shinji; Nomura, Mikihiro*; Yamaki, Tetsuya*; Sawada, Shinichi*; et al.
International Journal of Hydrogen Energy, 44(35), p.19141 - 19152, 2019/07
Yamaki, Tetsuya*; Nuryanthi, N.*; Kitamura, Akane; Koshikawa, Hiroshi*; Sawada, Shinichi*; Voss, K.-O.*; Severin, D.*; Tautmann, C.*
Nuclear Instruments and Methods in Physics Research B, 435, p.162 - 168, 2018/11
We used individual single-ion tracks in fluoropolymers with diameters of tens to hundreds of nanometers; chemical etching and ion-track grafting enabled us to develop ion-track and proton-conductive membranes, respectively. In the ion-track membranes of PVDF, strongly-LET-dependent etching was found, so the pore shape as well as the size was exclusively controlled by the track structures. We performed the ion-track grafting of styrene into ETFE to develop nanostructure-controlled proton exchange membranes (PEMs) for applications in PEM fuel cells. Our ion beam technology to develop fluoropolymer-based nanostructures has the potential to apply in the field of filtration processes and fuel cell devices. This would make it possible to provide new microfiltration technology for water treatment, sterilization, petroleum refining and dairy processing.
Nomura, Mikihiro*; Kodaira, Takahide*; Ikeda, Ayumi*; Naka, Yasuhito*; Nishijima, Haruyuki*; Imabayashi, Shinichiro*; Sawada, Shinichi*; Yamaki, Tetsuya*; Tanaka, Nobuyuki; Kubo, Shinji
Journal of Chemical Engineering of Japan, 51(9), p.726 - 731, 2018/09
Thermochemical hydrogen production by the iodine-sulfur process decomposes water into hydrogen and oxygen by combining the chemical reactions of iodine and sulfur. Two types of acids are produced through the Bunsen reaction. To improve the performance of this reaction, ion-exchange membranes for the membrane Bunsen reaction should be developed. In the present study, a cation-exchange membrane was prepared by using a radiation-graft polymerization method. It was found that a divinylbenzene crosslinking procedure was very effective in reducing water permeation through the membrane, and the membrane Bunsen reaction was successfully carried out by using the developed crosslinked membrane. Therefore, the developed crosslinked membrane is a potential candidate for cation-exchange membranes for the membrane Bunsen reaction.
Yamaki, Tetsuya*; Kitamura, Akane; Sawada, Shinichi*; Koshikawa, Hiroshi*
Nippon Kaisui Gakkai-Shi, 72(2), p.62 - 74, 2018/04
This review paper is devoted to two topics, i.e., fluoropolymer-based porous and ion-exchange membranes, both of which include the creation of nanostructure-controlled functional membranes with high-energy ion beams. Latent tracks of the MeV-GeV heavy ions in a polymer foil can sometimes be chemically etched out to form a membrane with micro- and nano-sized through-pores, the so-called ion-track membrane. Our focus is on ion-track membranes of poly (vinylidene fluoride) (PVDF) and cation- and anion-exchange membranes (CEMs and AEMs, respectively).
Yamaki, Tetsuya*; Goto, Mitsuaki*; Sawada, Shinichi*; Koshikawa, Hiroshi*; Kitamura, Akane; Higa, Mitsuru*
QST-M-8; QST Takasaki Annual Report 2016, P. 35, 2018/03
We prepared ion exchange membranes by a heavy-ion-track grafting method, and then used them for seawater concentration process. Both the water uptake and resistance were lower for our ion-track grafted membranes than for the conventional -ray-grafted membranes. The results would be because local and high-density energy deposition due to the ion beam enabled us to control the membrane structure in a nanometer scale. We demonstrate our membranes are suitable for this application.
Hidaka, Akihide; Nakano, Yoshihiro; Watanabe, Yoko; Arai, Nobuyoshi; Sawada, Makoto; Kanaizuka, Seiichi*; Katogi, Aki; Shimada, Mayuka*; Ishikawa, Tomomi*; Ebine, Masako*; et al.
JAEA-Review 2016-011, 208 Pages, 2016/07
JAEA has been conducting the Instructor Training Program (ITP) since 1996 under the auspices of MEXT to contribute to human resource development in currently 11 Asian countries in the field of radiation utilization for seeking peaceful use of nuclear energy. ITP consists of Instructor Training Course (ITC), Follow-up Training Course (FTC) and Nuclear Technology Seminars. In the ITP, trainings or seminars relating to technology for nuclear utilization are held in Japan by inviting nuclear related people from Asian countries to Japan and after that, the past trainees are supported during FTC by dispatching Japanese specialists to Asian countries. News Letter is also prepared to provide the broad range of information obtained through the trainings for local people near NPPs in Japan. The present report describes the activities of FY2014 ITP and future challenges for improving ITP more effectively.
Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; et al.
Transactions of the Materials Research Society of Japan, 40(4), p.359 - 362, 2015/12
The ion-track grafting of a vinylbenzyl chloride (VBC) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film is necessary for preparing nanostructured hydroxide-ion-conductive electrolyte membranes. A key for success here is to obtain as high graft levels as possible (for higher conductivity) in a smaller number of tracks (for improving the other membrane properties). To this end, therefore, the effect of the medium for the VBC grafting was investigated as part of our continuing effort to optimize the experimental conditions. A 25 m-thick ETFE film was irradiated in a vacuum chamber with 560 MeV Xe at different fluences, and then the grafting was performed by immersing the irradiated films in a 20vol% VBC monomer at 60C. A medium was a mixture of water (HO) and isopropyl alcohol (iPrOH) at different volume ratios. The degree of grafting increased as the HO content became higher, and reached a maximum in pure HO. These results can be explained by considering the well-known Trommsdorff effect, in which poor solubility of the grafted polymer in polar media leads to an increased polymerization rate probably due to a lower termination rate.
Hamada, Takashi; Hasegawa, Shin; Fukasawa, Hideyuki*; Sawada, Shinichi; Koshikawa, Hiroshi; Miyashita, Atsumi; Maekawa, Yasunari
Journal of Materials Chemistry A, 3(42), p.20983 - 20991, 2015/11
no abstracts in English
Sawada, Shinichi; Ursino, C.*; Galiano, F.*; Simone, S.*; Drioli, E.*; Figoli, A.*
Journal of Membrane Science, 493, p.232 - 242, 2015/11
The replacement of commonly-used substances with non-toxic equivalents is attracting a great amount of attention in membrane preparation processes. In order to address this issue, we prepared porous poly(vinylidene fluoride) (PVDF) membranes via thermally-induced phase separation using the following non-toxic Citroflex as solvents: acetyl tributyl citrate (ATBC); acetyl triethyl citrate (ATEC); and triethyl citrate (TEC). The pore size of the membranes increased in the following solvent order of ATBC ATEC TEC, which is the same trend of the PVDF/solvent affinity. During the phase separation process, high-affinity solvent molecules should have enough molecular mobility and easily gather with each other to form the large solvent rich phases, thereby producing the large pores. In the pure water microfiltration test using the PVDF membranes, the water permeability can be controlled in the wide range, depending on the pore size.
Kim, J.*; Fujiwara, Akihiko*; Sawada, Tomohiro*; Kim, Y.*; Sugimoto, Kunihisa*; Kato, Kenichi*; Tanaka, Hiroshi*; Ishikado, Motoyuki*; Shamoto, Shinichi; Takata, Masaki*
IUCrJ, 1(3), p.155 - 159, 2014/05
Using a charge density analysis based on synchrotron radiation X-ray powder diffraction data, we found that the charge carriers only accumulated in the iron layer of the superconducting phase of LaFeAsOF at low temperatures. Analysis of the electrostatic potential distribution revealed the concerted enhancement of the electronic polarization of the As ions and the carrier redistribution.
Tran Duy, T.*; Sawada, Shinichi; Hasegawa, Shin; Yoshimura, Kimio; Oba, Yojiro*; Onuma, Masato*; Katsumura, Yosuke*; Maekawa, Yasunari
Macromolecules, 47(7), p.2373 - 2383, 2014/04
The hierarchical structures of graft-type ETFE-based polymer electrolyte membranes (ETFE-PEMs) were investigated using small- and ultrasmall-angle X-ray cattering experiments. The ETFE-PEMs with IECs 2.4 mmol/g possessed conducting graft domains around lamellar crystals, with a d-spacing of 21.8-29.1 nm, and oriented crystallites with short and long correlation distances of 218-320 and 903-1124 nm, respectively. The membranes with IECs 2.7 mmol/g showed a new phase of crystallite network domains with a d-range of 225-256 nm, indicating a phase transition from oriented crystallite to crystallite network structures in the IEC range of 2.4-2.7 mmol/g. Noted that for the ETFE-PEMs with high IECs higher conductivity at 30% RH and compatible tensile strengths at 100% RH and 80 C, compared with Nafion, originated from the well-interconnected ion channels around the crystallites and the remaining lamellar crystals and crystallites, respectively.
Ishibashi, Masayuki; Onoe, Hironori; Sawada, Atsushi; Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Hosoya, Shinichi*
Dai-42-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.101 - 106, 2014/01
Japan Atomic Energy Agency is proceeding with the Mizunami Underground Research Laboratory Project in order to establish comprehensive techniques for the investigation, analysis and assessment of the deep geological environment in fractured crystalline rock for geological disposal of high level radioactive wastes. We have carried out discrete fracture network modeling, groundwater flow and particle tracking simulation in order to understand the important factors for the solute transport characterizations. In this paper, a method of discrete fracture network modeling based on in-situ data at underground gallery and the influences of different data interpretation are described.
Tran, D. T.; Sawada, Shinichi; Hasegawa, Shin; Katsumura, Yosuke*; Maekawa, Yasunari
Journal of Membrane Science, 447, p.19 - 25, 2013/11
Relative humidity (RH) dependence of the proton conduction and mechanical properties of poly(ethylene-co-tetrafluoroethylene) (ETFE)-based radiation grafted polymer electrolyte membranes (PEMs) were investigated in a wide ion exchange capacity (IEC) range at 80 C. The proton conductivities of the ETFE-based PEMs for IECs of 1.3-2.9 mmol/g were 0.001-0.013 S/cm at 30% RH. These PEMs have conductivities that are less dependent on RH than aromatic-hydrocarbon-polymer based PEMs. The ETFE PEM (IEC 2.4 mmol/g) showed higher tensile strength than Nafion at 100% RH. It was revealed that the mechanical strength and proton conductivity were clearly related to PEM crystallinities.
Kitamura, Akane; Yamaki, Tetsuya; Yuri, Yosuke; Sawada, Shinichi; Yuyama, Takahiro
Nuclear Instruments and Methods in Physics Research B, 314, p.47 - 50, 2013/11
Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Asano, Masaharu; Sawada, Shinichi; Hakoda, Teruyuki; Maekawa, Yasunari; Voss, K.-O.*; Severin, D.*; Seidl, T.*; et al.
Nuclear Instruments and Methods in Physics Research B, 314, p.77 - 81, 2013/11
Ion-track membranes of poly(vinylidene fluoride) (PVDF), a type of fluoropolymer, could find wide applications due to its superior chemical and mechanical properties. In order to produce track-etched pores in PVDF films, we have independently employed much milder etching conditions without any oxidant additives in the alkaline etching solution. The goal of this work is to pursue the possibility of varying beam parameters and applying the effect of the etching pretreatment to control the pore size and shape. Ongoing in-situ/on-line analyses at the M-branch of the UNILAC would shed light on the detailed chemistry of not only ion-induced degradation but also the post-irradiation reactivity.
Nuryanthi, N.*; Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Sawada, Shinichi; Hasegawa, Shin; Maekawa, Yasunari; Katsumura, Yosuke*
Nuclear Instruments and Methods in Physics Research B, 314, p.95 - 98, 2013/11
Our efforts have been focused on ion-track etched membranes of poly(vinylidene fluoride) (PVDF). This study deals with the effect of the transmembrane potential applied during the conductometry in order to offer a higher degree of freedom to control the pore size. We can say that higher voltage application during the conductometry would accelerate the etching in the tracks. The electrophoretic migration of dissolved products occurring out of each pore might be one of the reasons for this enhanced pore evolution and growth.