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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:81.07(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, 3(4), p.402 - 406, 2015/12

Journal Articles

Observation of oxidized region in $$gamma$$-ray irradiated polyethylene with KOH treatment and SEM-EDS

Shimada, Akihiko; Sugimoto, Masaki; Yoshikawa, Masahito

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 30, 2015/03

In case of the accelerated ageing test on polymer cable insulation used for the nuclear power facility, it is very important to recognize whether oxygen penetrates in the polymer wholly or not. To confirm this, there are the method by which polymer is soaked in the KOH solution at 70$$^{circ}$$C for 5 minutes, dried and observed by a SEM-EDS, only for ethylene propylene rubber, one of the polymers. This study is to apply that method for polyethylene. Polyethylene sheet of 2 mm thickness was irradiated by $$gamma$$ ray at a dose rate of 2 kGy/h for 400 h. A piece of irradiated polyethylene was picked up and the piece was soaked in the KOH solution for 24 h. After that, the piece was observed by a SEM-EDS. At the region within 70 micro meters from the surface, potassium is observed. It means that oxidation is occurred in this region. From now on, optimum soaking time will be examined.

Journal Articles

Characterization of Pt and Pd epitaxial films on sapphire substrates by RBS/channeling

Yamamoto, Shunya; Hakoda, Teruyuki; Yoshikawa, Masahito

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 129, 2015/03

no abstracts in English

Journal Articles

Structural and gasochromic properties of WO$$_{3}$$ films prepared by reactive sputtering deposition

Yamamoto, Shunya; Hakoda, Teruyuki; Miyashita, Atsumi; Yoshikawa, Masahito

Materials Research Express (Internet), 2(2), p.026401_1 - 026401_8, 2015/02

 Times Cited Count:2 Percentile:88.07(Materials Science, Multidisciplinary)

The effects of deposition temperature and film thickness on the structural and gasochromic properties of tungsten trioxide films used for the optical detection of diluted cyclohexane have been investigated. The tungsten trioxide films were prepared on SiO$$_{2}$$ substrates by magnetron sputtering, with the deposition temperature ranging from 300 to 550$$^{circ}$$C in an Ar and O$$_{2}$$ gas mixture. The gasochromic properties of the films, coated with a catalytic Pt layer, were examined by exposing them up to 5% cyclohexane in N$$_{2}$$ gas. We found that (001)-oriented monoclinic tungsten trioxide films, with a columnar structure, grew at deposition temperatures between 400 and 450$$^{circ}$$C. The gasochromic characterization of the tungsten trioxide films revealed that (001)-oriented tungsten trioxide films, with cauliflower-like surface morphology, were appropriate for the optical detection of cyclohexane.

Journal Articles

Plasmonic cyclohexane-sensing by sputter-deposited Au nanoparticle array on SiO$$_{2}$$

Kawaguchi, Kazuhiro*; Yamamoto, Shunya; Yoshikawa, Masahito; Takahiro, Katsumi*

Thin Solid Films, 562, p.648 - 652, 2014/07

 Times Cited Count:3 Percentile:79.74(Materials Science, Multidisciplinary)

Liquid organic-hydrides such as cyclohexane which can release-absorbing hydrogen in reversible have been proposed approvable carriers to store and transport hydrogen. However, organic-hydrides are known as highly flammable in air. To realize practical use of this hydrogen production process, the monitoring of leakage of organic-hydride gas is strongly required. In the present work, we have examined the plasmonic sensing ability of Au nanoparticle (NP) arrays for dilute cyclohexane. Au NP arrays were prepared on SiO$$_{2}$$ by a sputter deposition technique. The change in an extinction spectrum of Au NP arrays before and after exposure of cyclohexane vapor enabled us to detect it. The Au NP array prepared with 4.4 $$times$$ 10$$^{16}$$ Au atoms/cm$$^{2}$$ deposited at 300$$^{circ}$$C was and demonstrated a high sensitivity for cyclohexane at RT. The experimentally detectable concentration of cyclohexane was as low as 0.5 vol%, much lower than its explosion limit (1.3 vol%).

Journal Articles

Production of nano-sized platinum-particle films using low energy electron beams

Hakoda, Teruyuki; Yamamoto, Shunya; Aritani, Hirofumi*; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 127, 2014/03

Reduction of noble metal ions and subsequent production of noble metal particles in a solution has been performed as a radiation-induced precipitation (RIP) method using high energy ionizing radiation. Electron beams with energies below 300 keV have shorter penetration range and can irradiate at higher dose rates. Application of such low energy EBs to the RIP method has a possibility of producing film matters consisting of noble metal particles on the surface of the solution. In the present study, this possibility was examined using a few ten keV EBs for PtCl$$_{6}$$$$^{2-}$$ ion solutions. Black-colored film matters were produced on the surface of the sample solution after EB irradiation. Lower concentrations of ethanol such as 0.5v% accelerated the formation of Pt films on the sample solution. The films had network structure consisting of connected Pt particles with sizes of 2-5 nm.

Journal Articles

Preparation of gasochromic MoO$$_{3}$$ films by reactive sputtering deposition

Yamamoto, Shunya; Hakoda, Teruyuki; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 123, 2014/03

no abstracts in English

Journal Articles

Creation of database of radiation resistance on polymer materials and equipment

Shimada, Akihiko; Sugimoto, Masaki; Miyashita, Atsumi; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 29, 2014/03

Recovery from the accident at Tokyo Electric Power Company Fukushima Dai-ichi Nuclear Power Plant (NPP) is a matter of great urgency. In order to realize safe and secure operation for decontamination and decommissioning of NPP, it is indispensable to use equipments with sufficient radiation resistance (RR). In JAEA as well as other agency, various studies on RR of various materials and equipments have been conducted and a number of reports and papers have been published. Then, we started construction of a database named as "Database of Radiation Resistance on Polymer Materials and Equipments" and announced this database in a press release on June 1, 2012. At present, the database includes 878 data of materials, which are consisted of 423 data of polymer materials, 223 data of equipments and parts, 103 data of oils, fats and paintcoatings and 129 data of organic composite materials. The database will be extended and expected to be utilized for safe and secure operation.

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

Atomic and electronic structure analysis of the interface between $$a$$-SiO$$_{2}$$ and 4H-SiC(11-20)

Miyashita, Atsumi; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 11, 2014/03

no abstracts in English

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

Epitaxial transformation of hcp-fcc Ti sublattices during nitriding processes of evaporated-Ti thin films due to nitrogen-implantation

Chen, Y.*; Feng, X.*; Kasukabe, Yoshitaka*; Yamamoto, Shunya; Yoshikawa, Masahito; Fujino, Yutaka*

Journal of Alloys and Compounds, 577(Suppl.1), p.S18 - S24, 2013/11

 Times Cited Count:0 Percentile:100(Chemistry, Physical)

Epitaxial transformation processes of titanium films due to Nitrogen-implantation have been clarified through in-situ observations by using transmission electron microscope(TEM)and electron energy loss spectroscope, along with molecular orbital calculations. The N$$_{2}$$$$^{+}$$ ions with 62 keV are implanted into as-deposited Ti films which consist of hcp-Ti and TiH$$_{x}$$ with preferred orientations, in the 400 kV analytic high resolution TEM combined with ion accelerators at JAEA Takasaki. Thus, titanium nitride (TiN$$_{y}$$) films with preferred orientations are epitaxially formed by the inheritance of partial atomic arrangement of hcp-Ti or TiH$$_{x}$$ in as-deposited Ti films and by the occupation of octahedral sites by N atoms, which elucidates that epitaxial transformation of hcp-fcc Ti sublattices occurs.

Journal Articles

Characterization of epitaxial transformation phenomena induced by the interaction of implanted N-ions with Ti thin films

Kasukabe, Yoshitaka*; Shimoda, Hiroyuki*; Chen, Y.*; Yamamoto, Shunya; Yoshikawa, Masahito; Fujino, Yutaka*

Nuclear Instruments and Methods in Physics Research B, 315, p.131 - 135, 2013/11

 Times Cited Count:1 Percentile:86.02(Instruments & Instrumentation)

Epitaxial transformation phenomena of titanium films due to Nitrogen-implantation have been clarified through in-situ observations by using transmission electron microscope(TEM)and electron energy loss spectroscope (EELS), along with molecular orbital calculations. The N$$^{2+}$$ ions with 62 keV are implanted into as-deposited Ti films which consist of hcp-Ti and TiH$$_{rm x}$$ with preferred orientations, in the 400 kV analytic high resolution TEM combined with ion accelerators at JAEA Takasaki. The result of EELS measurements indicates that the hcp-fcc transformation occurs preferentially above a critical concentration ratio, N/Ti $$sim$$ 0.25. This means that above the N/Ti $$sim$$ 0.25, the invasion of implanted N atom to the N-unoccupied octahedral site in the neighboring unit cell next to the N-occupied one in hcp-Ti occurs preferentially, and induces the growth of nucleus of the hcp-fcc transformation.

Journal Articles

Gasochromic property of dehydrogenation-catalyst loaded tungsten trioxide

Hakoda, Teruyuki; Igarashi, Hidetoshi*; Isozumi, Yukihiro*; Yamamoto, Shunya; Aritani, Hirofumi*; Yoshikawa, Masahito

Journal of Physics and Chemistry of Solids, 74(2), p.200 - 204, 2013/02

 Times Cited Count:3 Percentile:78.86(Chemistry, Multidisciplinary)

The gasochromic property of dehydrogenation-catalyst loaded tungsten trioxide (M/WO$$_{3}$$) powders was examined in exposure to gaseous cyclohexane under different kinds and contents of catalysts, catalyst temperatures, and cyclohexane concentrations. The change in the intensity of visible lights reflected from the M/WO$$_{3}$$ powders was in situ obtained using a portable visible-light spectrometer. The catalyst of Pt was a catalyst initiating dehydrogenation and the change of reflected light intensity at lower temperatures in comparison with the catalysts of Pd and Rh. Among 0.1, 0.5, and 1wt% Pt/WO$$_{3}$$ powders, the 0.5wt% Pt/WO$$_{3}$$ powders demonstrated large change of reflected lights. The heating of 0.5wt% Pt/WO$$_{3}$$ powders at temperatures higher than 130$$^{circ}$$C was required to visually detect cyclohexane at a concentration of 1v%, lower than the combustion lower limit (1.3v%).

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.

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

Preparation of nano-sized platinum particles using low energy electron beams, and application to catalytic reaction

Isozumi, Yukihiro; Hakoda, Teruyuki; Yamamoto, Shunya; Aritani, Hirofumi*; Yoshikawa, Masahito

Radioisotopes, 61(6), p.289 - 296, 2012/06

In the present study, the reduction of PtCl$$_{6}$$$$^{2-}$$ ions and subsequent formation of Pt particles were examined for a few tens keV EB irradiation of PtCl$$_{6}$$$$^{2-}$$ ion solution in the presence of 1-20wt% ethanol as an OH radical scavenger. As a result, the reduction of PtCl$$_{6}$$$$^{2-}$$ ions proceeded in whole solution by irradiating only the topmost surface layer of the solution, and these Pt particles with sizes of 2-5 nm would be produced as primary particles through reduction of PtCl$$_{6}$$$$^{2-}$$ ions. Moreover, these Pt particles were observed to have hydrogen dissociation activity and oxidation activity.

Journal Articles

Optical detection of organic hydrides with platinum-loaded tungsten trioxide

Yoshimura, Kimio; Hakoda, Teruyuki; Yamamoto, Shunya; Yoshikawa, Masahito

Journal of Physics and Chemistry of Solids, 73(5), p.696 - 698, 2012/05

 Times Cited Count:4 Percentile:76.08(Chemistry, Multidisciplinary)

Tungsten trioxide powder with loading 0.1wt% platinum (Pt/WO$$_{3}$$) was prepared for opticaldetection of organic hydrides such as cyclohexane, decalin by impregnation with PtCl$$_6^{2-}$$ and subsequent calcination in N$$_{2}$$ gas at 500$$^{circ}$$C. The SEM observation of Pt/WO$$_{3}$$ shows that the Pt particles with mean diameters of 80-100 nm were on the surface of the WO$$_{3}$$ powder. The Pt/WO$$_{3}$$ showed coloration for 13% cyclohexane at higher 100$$^{circ}$$C and for 1.3% cyclohexane at 200$$^{circ}$$C. The in-situ XRD results of the Pt/WO$$_{3}$$ in coloring/bleaching change indicate that the coloring of Pt/WO$$_{3}$$ was caused by transformation of WO$$_{3}$$ to tungsten bronze. The analysis of reacted gas demonstrates that Pt on WO$$_{3}$$ produces only hydrogen and benzene through dehydrogenation of cyclohexane over 100$$^{circ}$$C. It was founded that the Pt/WO$$_{3}$$ has potential of optical detection of organic hydrides by heating at higher 100$$^{circ}$$C.

Journal Articles

Blueshift and narrowing of localized surface plasmon resonance of silver nanoparticles exposed to plasma

Kawaguchi, Kazuhiro; Saito, Masahiro*; Takahiro, Katsumi*; Yamamoto, Shunya; Yoshikawa, Masahito

Plasmonics, 6(3), p.535 - 539, 2011/09

 Times Cited Count:5 Percentile:76.5(Chemistry, Physical)

Silver nanoparticles (Ag NPs) have optical absorption bands due to localized surface plasmon resonance (LSPR) in visible range. The LSPR of Ag-NPs is being used for optical gas sensors. However, there have been differences in LSPR absorption band between most of the experimental data and calculations. We have demonstrated that plasma treatments for Ag NPs to clear the effect of contamination on surface of Ag NPs for LSPR absorption band. The results show that Ar plasma treatments to Ag NPs bring blue-shift and narrowing in their LSPR absorption band. Raman scattering analysis result that hydrocarbons adsorbed on silver surfaces were removed effectively by plasma exposure. It was found that the decrease in Raman line intensity for hydrocarbons was correlated well with the blue-shift. Our findings indicate that one of the most important factors for difference in LSPR absorption band between the experimental data and calculations is due to the impurity adsorption on silver surfaces.

331 (Records 1-20 displayed on this page)