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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:9.29(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

Influence of configuration at dopant sites on catalytic activity of phosphorus-doped graphite

Shimoyama, Iwao; Hakoda, Teruyuki; Shimada, Akihiko; Baba, Yuji

Carbon, 81, p.260 - 271, 2015/01

 Times Cited Count:21 Percentile:64.2(Chemistry, Physical)

The relationship between catalytic activity and local structure at dopant sites of phosphorus-doped graphite prepared by ion implantation was studied by electrochemical measurements and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The P K-edge NEXAFS spectra of samples doped at room temperature and high temperature showed different polarization dependences, with graphite-like clear polarization dependence observed for the sample prepared by high-temperature doping. NEXAFS spectra were analyzed by density functional theory calculations to reveal the chemical-bonding states of P sites. In electrochemical measurements with an acid solution, samples with relatively small polarization dependence of NEXAFS exhibited marked catalytic activity in oxygen reduction reactions while those with larger polarization dependence showed lower catalytic activity. This indicates the influence of the configuration at dopant sites on catalytic activity and suggests that the introduction of curved structures is one way to design carbon catalysts with high catalytic activity.

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

Preparation of tungsten carbide nanoparticles by ion implantation and electrochemical etching

Kato, Sho; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kawaguchi, Kazuhiro; Kobayashi, Tomohiro*; Suzuki, Akihiro*; Terai, Takayuki*

Nuclear Instruments and Methods in Physics Research B, 314, p.149 - 152, 2013/11

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

We implanted 100 keV W$$^+$$ in unpolished GC substrates at nominal fluences up to $$1.7times10^{17}$$ ions/cm$$^2$$. The implanted samples were electrochemically anodized in a NaOH aqueous solution to etch the surface layer. The analyses were performed by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). XPS W 4f spectra indicated the formation of carbides as reported previously. The electrochemical etching clearly increased the W concentration on the surface. According to the RBS results, half of the implanted W atoms were retained in the substrate, while the rest should escape to the etching solution. The cross-sectional TEM image revealed a uniform distribution of WC particles with a diameter of less than 10 nm just near the surface region.

Journal Articles

Ion-track membranes of fluoropolymers; Toward controlling the pore size and shape

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

 Times Cited Count:2 Percentile:21.46(Instruments & Instrumentation)

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.

Journal Articles

Nanoparticle formation by tungsten ion implantation in glassy carbon

Kato, Sho; Yamaki, Tetsuya; Yamamoto, Shunya; Hakoda, Teruyuki; Kawaguchi, Kazuhiro; Kobayashi, Tomohiro*; Suzuki, Akihiro*; Terai, Takayuki*

Transactions of the Materials Research Society of Japan, 38(1), p.81 - 84, 2013/03

Nanoparticles were formed by 100 keV tungsten-ion implantation in unpolished glassy carbon substrates at nominal fluences of $$2.4times10^{16}$$ - $$1.8times10^{17}$$ ions/cm$$^2$$. The implanted samples were analyzed by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, hydrodynamic voltammetry using a rotating disk electrode, and field emission scanning electron microscopy. A significant sputtering effect changed the depth profile during the course of irradiation and limited the amount of tungsten retainable in the substrate in agreement with our calculated distributions. The nanoparticles were composed of tungsten carbide and dispersed uniformly with diameters of around 10 nm.

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:18.93(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%).

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:21.91(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

Spectroellipsometric studies on EB induced refractive index change of aliphatic polyimide

Seito, Hajime; Hakoda, Teruyuki; Hanaya, Hiroaki; Haruyama, Yasuyuki; Kaneko, Hirohisa; Yamashita, Takashi*; Kojima, Takuji

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 150, 2012/01

no abstracts in English

Journal Articles

Dosimetry for 110 keV electron beam processing

Seito, Hajime; Matsui, Shinjiro*; Hakoda, Teruyuki; Ishikawa, Masayoshi*; Haruyama, Yasuyuki; Kaneko, Hirohisa; Kimura, Jun*; Kojima, Takuji

Zairyo Gijutsu, 30(1), p.10 - 16, 2012/01

The dosimetry of a 110 keV electron beam (EB) irradiation field is studied using a calorimeter, film dosimeter, and Monte Carlo simulation. This is important base for dose control in practical processing to guarantee the process reproducibility and product reliability. The simulation results are validated on the measurement of the energy fluence obtained by the calorimeter at one position in the air plane at different distances from a beam exit window. The spatial dose distribution obtained from the simulation is compared to that obtained by the film dosimeter. They show good agreement within $$pm$$5.0%. The precision of $$pm$$5.0% is sufficient to control the surface modification of polymers and the development of semiconductor devices in practical radiation processing. These results suggest that film dosimetry results at just one position in the air plane are sufficient to determine the irradiation characteristics of the low energy EB, and to provide a base of quality control measures in practical radiation processing.

Journal Articles

Relationship between catalytic property and NEXAFS of P-doped graphite

Shimoyama, Iwao; Hakoda, Teruyuki; Baba, Yuji; Sekiguchi, Tetsuhiro; Hirao, Norie; Koswattage, K.

Photon Factory Activity Report 2011, Part B, p.93_1 - 93_2, 2012/00

no abstracts in English

Journal Articles

Success of flue gas cleaning by electron beam and other industrial applications of radiation processing in Poland

Chmielewski, A. G.*; Hakoda, Teruyuki

Hoshasen To Sangyo, (130), p.15 - 19, 2011/06

This paper is the article which was translated from an English original one entitled as "Success of Flue Gas Cleaning by Electron Beam and Other Industrial Applications of Radiation Processing in Poland" written by Dr. Andrzej G. Chmielewski. This paper describes the status of the development of the purification technology of fuel gases from electric power plants using electron beam irradiation, and the electron-beam and $$gamma$$-ray irradiation facilities for sterilization and polymer production.

Journal Articles

Purification of gas using electron beam

Hirota, Koichi; Hakoda, Teruyuki; Shimada, Akihiko; Taguchi, Mitsumasa; Kimura, Atsushi; Kojima, Takuji

Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.108 - 109, 2011/06

We have focused on using MnO$$_2$$ for the oxidation of intermediates produced from electron beam irradiation of VOC. Manganese dioxide can decompose ozone, produced by the irradiation of air containing VOCs, into activated oxygen, which can ultimately oxide the intermediates. Hybrid system equipped with electron accelerator and MnO$$_2$$ has demonstrated the complete oxidation of the intermediates produced during the irradiation of xylene and toluene. The electron-beam treatment of dioxin from municipal solid waste incinerator was carried out at Takahama Clean Center in Japan. An incinerator gas of 1000 m$$^3$$N/h was diverted downstream of a dry electric precipitator and was irradiated with electron beams using an electron accelerator that supplied 300 kV with a maximum energy of 12 kW. The results showed electron-beam is a promising technology for destroying dioxin in exhaust gases.

Journal Articles

Synthesis of palladium nanoparticles in a ceramic matrix using radiation grafting method

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

Radiation Physics and Chemistry, 80(4), p.587 - 590, 2011/04

 Times Cited Count:1 Percentile:11.72(Chemistry, Physical)

no abstracts in English

Journal Articles

Dehydrogenation catalyst for optical organic-hydride detection

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

Applied Surface Science, 257(9), p.4428 - 4431, 2011/02

 Times Cited Count:5 Percentile:27.56(Chemistry, Physical)

no abstracts in English

Journal Articles

Oxygen reduction activity of N-doped carbon-based films prepared by pulsed laser deposition

Hakoda, Teruyuki; Yamamoto, Shunya; Kawaguchi, Kazuhiro; Yamaki, Tetsuya; Kobayashi, Tomohiro*; Yoshikawa, Masahito

Applied Surface Science, 257(5), p.1556 - 1561, 2010/12

 Times Cited Count:12 Percentile:51.43(Chemistry, Physical)

Carbon-based films having nitrogen species on their surface were prepared on a glassy-carbon (GC) substrate as a non-platinum cathode catalyst for polymer electrolyte fuel cells by depositing cobalt and carbon in the presence of N$$_{2}$$ gas using a pulse laser deposition method and then removing metal Co by HCl-washing treatment. The oxygen reduction reaction (ORR) activity was electrochemically determined using a rotating disk electrode system where the film samples on the GC substrate were replaceable. The ORR activity increased with elevating temperature of the GC substrate during the deposition. A carbon-based film prepared at 600$$^{circ}$$C in the presence of 66.7 Pa N$$_{2}$$ showed the highest ORR activity among the tested samples; its ORR potential was 0.66 V (vs. NHE). This film was composed of amorphous carbons doped with pyridine-type nitrogen atoms on its surface.

Journal Articles

175 (Records 1-20 displayed on this page)