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Journal Articles

Changes in electronic structure of carbon supports for Pt catalysts induced by vacancy formation due to Ar$$^{+}$$ irradiation

Okazaki, Hiroyuki*; Kakitani, Kenta*; Kimata, Tetsuya*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Yamamoto, Shunya*; Yamaki, Tetsuya*

Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03

 Times Cited Count:1 Percentile:0.01(Chemistry, Physical)

Journal Articles

Fabrication of Pt nanoparticle incorporated polymer nanowires by high energy ion and electron beam irradiation

Tsukuda, Satoshi*; Takahashi, Ryota*; Seki, Shuhei*; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Tanaka, Shunichiro*

Radiation Physics and Chemistry, 118, p.16 - 20, 2016/01

 Times Cited Count:1 Percentile:14.27(Chemistry, Physical)

Polyvinylpyrrolidone (PVP)-Pt nanoparticles (NPs) hybrid nanowires were fabricated by high energy ion beam irradiation to PVP thin films including H$$_{2}$$PtCl$$_{6}$$. Single ion hitting caused crosslinking reactions of PVP and reduction of Pt ions within local cylindrical area along an ion trajectory (ion track); therefore, the PVP nanowires including Pt NPs were formed and isolated on Si substrate after wet-development procedure. The number of Pt NPs was easily controlled by the mixed ratio of PVP and H$$_{2}$$PtCl$$_{6}$$. However, increasing the amount of H$$_{2}$$PtCl$$_{6}$$ led to decreasing the radial size and separation of the hybrid nanowires during the wet-development. Additional electron beam irradiation after ion beam improved separation of the nanowires and controlled radial sizes due to an increase in the density of crosslinking points inner the nanowires.

Journal Articles

Swelling of radiation-cured polymer precursor powder for silicon carbide by pyrolysis

Takeyama, Akinori; Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito

Journal of Asian Ceramic Societies (Internet), 3(4), p.402 - 406, 2015/12

Journal Articles

In-situ monitoring of ion-beam luminescence of Si-O-C(-H) ceramics under proton-beam irradiation

Narisawa, Masaki*; Koka, Masashi; Takeyama, Akinori; Sugimoto, Masaki; Idesaki, Akira; Sato, Takahiro; Hokazono, Hiroki*; Kawai, Taketoshi*; Iwase, Akihiro*

Journal of the Ceramic Society of Japan, 123(9), p.805 - 808, 2015/09

Journal Articles

Model magnet development of D1 beam separation dipole for the HL-LHC upgrade

Nakamoto, Tatsushi*; Sugano, Michinaka*; Xu, Q.*; Kawamata, Hiroshi*; Enomoto, Shun*; Higashi, Norio*; Idesaki, Akira; Iio, Masami*; Ikemoto, Yukio*; Iwasaki, Ruri*; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4000505_1 - 4000505_5, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Recently, development of superconducting magnet system with high radiation resistance has been demanded for application in accelerator facilities such as CERN LHC. In order to realize superconducting magnet system with high radiation resistance, it is necessary to develop electrical insulator with high radiation resistance because the electrical insulator is made of organic materials whose radiation resistance is inferior to that of inorganic materials. We developed a glass fiber reinforced plastic with bismaleimide-triazine resin. The developed material showed excellent radiation resistance; the material evolved gases of 5$$times$$10 $$^{-5}$$mol/g and maintained flexural strength of 640MPa (90% of initial value).

Journal Articles

Irradiation effect of gamma rays on cyanate ester/epoxy resins, 3

Idesaki, Akira; Uechi, Hiroki*; Hakura, Yoshihiko*; Kishi, Hajime*

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 29, 2015/03

Effects of gamma-ray irradiation on a cyanate ester/epoxy resin composed of dicyanate ester of bisphenol A (DCBA) and diglycidyl ether of bisphenol A (DGEBA) was investigated by changes in physicochemical properties such as gas evolution behavior, change in chemical structure, and so on, after the gamma-ray irradiation with dose of 100 MGy as maximum under vacuum. It was found that ether linkages are mainly decomposed by the gamma-ray irradiation with evolving gases of hydrogen, carbon dioxide and carbon monoxide and decreasing in glass transition temperature.

Journal Articles

Effects of $$gamma$$-ray irradiation on a cyanate ester/epoxy resin

Idesaki, Akira; Uechi, Hiroki*; Hakura, Yoshihiko*; Kishi, Hajime*

Radiation Physics and Chemistry, 98, p.1 - 6, 2014/05

 Times Cited Count:17 Percentile:84.87(Chemistry, Physical)

Effects of $$gamma$$-ray irradiation on a cyanate ester/epoxy resin composed of dicyanate ester of bisphenol A (DCBA) and diglycidyl ether of bisphenol A (DGEBA) was investigated by changes in physicochemical and mechanical properties after the $$gamma$$-ray irradiation with dose of 100 MGy as maximum at ambient temperature under vacuum. After the irradiation, gases of hydrogen, carbon monoxide and carbon dioxide were evolved, glass transition temperature decreased, and flexural strength also decreased. It was concluded that ether linkages bonded to cyanurate, isocyanurate and oxazolidinone structures are mainly decomposed by the irradiation. After 100 MGy irradiation, the flexural strength of DCBA/DGEBA was maintained more than 170 MPa which is 90% of initial value of 195 MPa.

Journal Articles

A Macroporous SiC material synthesized from preceramic polymer with direct foaming and radiation curing

Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 42, 2014/03

A macroporous SiC material was synthesized from polycarbosilane (PCS) by direct foaming and radiation curing. A mixture of PCS and biurea, a blowing agent, was heat-treated in Ar to obtain foamed PCS body, irradiated by $$gamma$$-rays to fix the shaped body and finally pyrolyzed at 1000$$^{circ}$$C in Ar. In this work, effects of foaming temperature (280-320$$^{circ}$$C) and biurea content (0-1wt%) on the properties of obtained porous SiC material such as average cell size, porosity, compressive strength were investigated. It was found that the average cell size increased as foaming temperature and/or biurea content increased. Corresponding to increasing in average cell size, total porosity and open porosity increased and bulk density, closed porosity and compressive strength decreased. In case of the foaming at 280$$^{circ}$$C with biurea content of 1wt%, obtained porous SiC material showed average cell size of 0.5 mm, total porosity of 74% and compressive strength of 3.2 MPa.

Journal Articles

Synthesis of a porous SiC material from polycarbosilane by direct foaming and radiation curing

Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito

Innovative Processing and Manufacturing of Advanced Ceramics and Composites II; Ceramic Transactions, Vol.243, p.61 - 69, 2014/01

A macroporous SiC material was synthesized from polycarbosilane (PCS) by direct foaming and radiation curing. A mixture of PCS and biurea, a blowing agent, was heat-treated in Ar to obtain foamed PCS body, irradiated by $$gamma$$-rays to fix the shaped body and finally pyrolyzed at 1000$$^{circ}$$C in Ar. In this work, effects of foaming temperature (280-320$$^{circ}$$C) and biurea content (0-1wt%) on the properties of obtained porous SiC material such as average cell size, porosity, compressive strength were investigated. It was found that the average cell size increased as foaming temperature and/or biurea content increased. Corresponding to increasing in average cell size, total porosity and open porosity increased and bulk density, closed porosity and compressive strength decreased. In case of the foaming at 280$$^{circ}$$C with biurea content of 1wt%, obtained porous SiC material showed average cell size of 0.5 mm, total porosity of 74% and compressive strength of 3.2 MPa.

Journal Articles

Positron annihilation lifetime of irradiated polyimide

Hirade, Tetsuya; Oka, Toshitaka; Morishita, Norio*; Idesaki, Akira; Shimada, Akihiko

Materials Science Forum, 733, p.151 - 154, 2013/00

 Times Cited Count:7 Percentile:95.56

Polyimide polymers such as Kapton show a very good performance at high radiation environment such as in space or in radiation facilities. Positron annihilation lifetime measurement is a widely used method for materials science, and the lifetime of triplet positronium (electron-positron pair) can give important information of free volume of polymers. However, there is no positronium formation in Kapton and hence this method was no applied for polymer studies. Here, we indicated that free positron annihilation lifetime can give information of change of free volume by showing the temperature dependence of the lifetime. We applied this method to study irradiation effects on Kapton and we successfully indicated that the free positron lifetime can be applied for polymer studies.

JAEA Reports

Study of cable ageing mechanism for nuclear power plant (Contract research)

Seguchi, Tadao*; Tamura, Kiyotoshi*; Watashi, Katsumi; Suzuki, Masahide; Shimada, Akihiko; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Oshima, Takeshi; Kudo, Hisaaki*

JAEA-Research 2012-029, 158 Pages, 2012/12

JAEA-Research-2012-029.pdf:9.4MB

The degradation mechanisms of ethylene-propylene rubber (EPR), crosslinked polyethylene (XLPE), polyvinylchloride (PVC), and silicone rubber (SiR) as the cable insulation materials were investigated for the cable ageing research of the nuclear power plant. The materials as same insulations for the practical cable (practical formulation) and as the model formulation containing specific additive were selected. They were exposed to the accelerated radiation and thermal environments. The mechanical properties, the crosslinking and chain scission, and the distribution of antioxidant and of oxidative products were measured and analyzed.

Journal Articles

Synthesis of a Ni-containing porous SiOC material from polyphenylmethylsiloxane by a direct foaming technique

Idesaki, Akira; Colombo, P.*

Advanced Engineering Materials, 14(12), p.1116 - 1122, 2012/12

 Times Cited Count:9 Percentile:33.5(Materials Science, Multidisciplinary)

JAEA Reports

Ageing research of cable insulation materials

Seguchi, Tadao*; Tamura, Kiyotoshi; Kudo, Hisaaki*; Shimada, Akihiko; Sugimoto, Masaki; Idesaki, Akira; Oshima, Takeshi; Yoshikawa, Masahito

JAEA-Review 2012-027, 46 Pages, 2012/08

JAEA-Review-2012-027.pdf:5.87MB

The research on cable degradation mechanisms was conducted for 5 years in 2006 - 2010 as the project research of plant life management for nuclear power plant by NISA (Nuclear and Industrial Safety Agency) of METI (Ministry of Economy, Trade, and Industry). At the finish of above research, the degradation mechanisms were reviewed on the analysis of many reports on cable degradation. The reports published after 1970 were mainly surveyed and the facts or data containing the experimental accuracy were selected. The verified facts, the reasonable interpretation of the facts, unresolved aspects were checked on the view points of recent techniques or analysis, and proposed the new model of degradation mechanisms was proposed.

Journal Articles

The Effect of antioxidants on degradation mechanism of cable insulation material for nuclear power plant

Shimada, Akihiko; Kudo, Hisaaki*; Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito; Tamura, Kiyotoshi; Seguchi, Tadao*

Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.244 - 247, 2011/06

Journal Articles

Irradiation condition on accelerated ageing test of cable designed for nuclear power plants

Shimada, Akihiko; Kudo, Hisaaki*; Idesaki, Akira; Oshima, Takeshi; Tamura, Kiyotoshi; Seguchi, Tadao*

Proceedings of International Conference on Condition Monitoring and Diagnosis 2010 (CMD 2010), Vol.2, p.705 - 708, 2010/09

The lifetime evaluation of cable insulation used in nuclear power plants is very important for their safety running. In the present, the evaluation of cable lifetime is performed under the higher dose rate of radiation and elevated temperatures compared to actual conditions. In that case, we need to select the reasonable dose rate. One of the important points is the homogeneous oxidation throughout insulation polymer materials during irradiation for the equivalent oxidation with the real ageing condition. The oxidation depth of polymer material depends on the dose rate and oxygen diffusion coefficient into polymer material. Then, the dose rate could be increased if the diffusion coefficient was increased by increasing the irradiation temperature. The relations between dose rate and irradiation temperature were studied on XLPE, EPR, PVC and SiR for cable insulation. These materials are irradiated with cobalt 60 $$gamma$$-rays at dose rates up to 1 kGy/h under elevated temperature. The irradiation effects were analyzed by tensile test, change of swelling ratio and gel fraction, SEM-EDS, and FT-IR.

Journal Articles

Synthesis of a catalyst-loaded SiC material from Si-based polymer

Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito

Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.7 - 12, 2010/07

Recently, catalyst-loaded ceramic materials have been developed to apply for gas separators in the engineering field of hydrogen generation. Oxide ceramics of alumina and silica are used for the matrix in that field. However, the oxide ceramics are inferior to non-oxide ceramics in the point of resistance for high temperature, strong acid or alkali, hot steam, and so on. Si-based polymers are used as precursors for Si-based non-oxide ceramics. They have a good point of high formability and ability to form polymer blends with various materials. So far, we have established a fabrication technique of SiC products such as a fine fiber with average diameter of 6$$mu$$m and a membrane for hydrogen separation. In this work, we fabricate a catalyst-loaded SiC material from a blend of Si-based polymer and transition metal compound. The catalyst-loaded SiC material showed a catalytic performance of evolution of CO$$_{2}$$ gas oxidizing CO gas.

Journal Articles

Synthesis of ceramic nano fiber from precursor polymer by single particle nano-fabrication technique

Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Watanabe, Shogo*; Seki, Shu*

Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.105 - 110, 2010/06

We have succeeded in synthesizing ceramic nano fibers from precursor polymers using Single Particle Nanofabrication Technique (SPNT). A thin film of the precursor polymer was cross-linked by MeV-order heavy-ion beam irradiation along ion tracks of nano-size in radius through the whole thickness of the thin film. Nano fibers were developed on the surface of the substrate by dissolution and washing away of un-crosslinked polymer. Subsequent pyrolysis converted polymeric into ceramic nano fibers. The radius, length and number density of nano fibers are controlled by liner energy transfer (LET) of ion beam, thickness of polymeric target and number of projected ions, respectively.

Journal Articles

Control of radial size of crosslinked polymer nanowire by ion beam and $$gamma$$ ray irradiation

Tsukuda, Satoshi*; Asano, Atsushi*; Sugimoto, Masaki; Idesaki, Akira; Seki, Shu*; Tanaka, Shunichiro*

Journal of Photopolymer Science and Technology, 23(2), p.231 - 234, 2010/06

 Times Cited Count:0 Percentile:0.01(Polymer Science)

The nanowires based on polystyrene (PS) and polycarbosilane (PCS) were formed by 450 MeV Xe beam irradiation to their thin films. The nanowires, which formed by crosslinking reaction along the single ion path, can isolated by development procedures. This technique is sometimes called as single particle nanofabrication technique (SPNT). In this paper, tow step irradiation of ion beam and ray was carried out in order to control their radial sizes. The radial sizes of nanowires, based on PS and PCS were increased with the dose of ray. The change of radial sizes, which depended on the dose, was quantitatively measured, and we discussed in terms of radiation induced gel formation.

Journal Articles

Interlaminar shear properties of composite insulation systems for fusion magnets at cryogenic temperatures

Shindo, Yasuhide*; Takeda, Tomo*; Narita, Fumio*; Miura, Masaya*; Watanabe, Shinya*; Koizumi, Norikiyo; Idesaki, Akira; Okuno, Kiyoshi

Cryogenics, 50(1), p.36 - 42, 2010/01

 Times Cited Count:12 Percentile:43.19(Thermodynamics)

This paper reports the cryogenic interlaminar shear properties of composite insulation systems for the superconducting magnet coils in the International Thermonuclear Experimental Reactor (ITER). Short beam shear tests were performed at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) on three insulation systems consisting of woven glass fiber reinforced plastic (GFRP) composites with different polymer resins and polyimide films, and the dependence of their apparent interlaminar shear strength on the temperature and the polymer resins was discussed. A detailed observation of failed specimens was made to verify the failure mechanisms. Insulation systems subjected to $$gamma$$ irradiation at room temperature were also considered, and the effect of irradiation on the cryogenic interlaminar shear properties was examined.

Journal Articles

Gas evolution from insulating materials for superconducting coil of ITER by gamma ray irradiation at liquid nitrogen temperature

Idesaki, Akira; Koizumi, Norikiyo; Sugimoto, Makoto; Morishita, Norio; Oshima, Takeshi; Okuno, Kiyoshi

AIP Conference Proceedings 986, p.169 - 173, 2008/03

A laminated material composed of glass cloth/polyimide film/epoxy resin will be used as an insulating material for superconducting coil of ITER. In order to keep safe and stable operation of the superconducting coil system, it is indispensable to evaluate radiation resistance of the material, because the material is exposed to high radiation field of 10 MGy at low temperature of 4 K. In this work, the gas evolution from the laminated material by gamma ray irradiation at liquid nitrogen temperature (77 K) was investigated, and the difference of gas evolution behavior due to difference of components in the epoxy resin was discussed. As a result, it was found that the main gases from the epoxy resin by the irradiation were hydrogen, carbon monoxide and carbon dioxide, and that the amount of the gases from epoxy resin containing cyanate ester was 30-40% less than that from the epoxy resin containing tetraglycidyl-diaminophenylmethane (TGDDM).

85 (Records 1-20 displayed on this page)