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Nagata, Shinji*; Inoue, Aichi; Yamamoto, Shunya; Tsuchiya, Bun*; Takano, Katsuyoshi; To, Kentaro*; Shikama, Tatsuo*
Journal of Alloys and Compounds, 446-447, p.558 - 561, 2007/10
Times Cited Count:20 Percentile:69.78(Chemistry, Physical)The effect of the composition of non-stoichiometric WO films on the gasochromic coloration are investigated. The films are prepared by a reactive RF magnetron sputtering with varying oxygen partial pressure. To determine the quantitative composition of deposited films, Rutherford backscattering spectroscopy (RBS) and Elastic recoil detection (ERD) are employed. Gasochromic coloration of the films coated with Pd catalyst is examined by optical transmission in hydrogen gas. O/W atomic ratio of the films increases from 0.25 to 3.0 with increasing the oxygen partial pressure in the sputtering gas. H/W ratio increases up to 0.7 with increasing the O/W ration. As regards gasochromic coloration, the film with O/W atomic ratio of 3.0 shows superior coloration performance comparing with that of less than 3.0. Therefore, it is assumed that the good gasochromic coloration of tungsten oxide films is realized by near-stoichiometric WO. In addition, gasochromic coloration state, increasing of hydrogen concentration in WO films is observed. It indicates that gasochromic coloration of WO is relate to formation of HWO structure.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Sugimoto, Masaki; Yoshikawa, Masahito; Nagata, Shinji*
Japanese Journal of Applied Physics, Part 1, 46(9B), p.6315 - 6318, 2007/09
Times Cited Count:11 Percentile:39.15(Physics, Applied)The amorphous, polycrystalline, and oriented films of the tungsten oxide were fabricated by sputtering deposition. It is found that each film has different roughness in the surface. The films with rough surface show fast coloration in 1% hydrogen. There is possibility that the gasochromic properties are improved effectively by the control of the surface morphology, and the films with large grains on the surface have better gasochromic coloration.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Sugimoto, Masaki; Sugiyama, Akira; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(3), p.673 - 676, 2007/09
The deposition of tungsten oxide on the sheet of polyethylene terephthalate or polyvinylindene chloride was performed by sputtering method. It was found that the color of the sheets changes within few minuets to expose 0.1 vol.% diluted hydrogen, so as to be able to confirm the change by viewing. The sheets can be produced with low cost, and are useful as convenient sheet-type hydrogen sensors for the utilization of hydrogen in fuel cell as a clean energy source.
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
Nuclear Instruments and Methods in Physics Research B, 262(1-2), p.29 - 32, 2007/08
Times Cited Count:21 Percentile:79.51(Instruments & Instrumentation)Tungsten oxide films coated with Pd catalysts are colored by exposure to hydrogen gas (gasochromic coloration) and it can be used for optical hydrogen sensors. The effects of composition and structure on gasochromic coloration of tungsten oxide films for hydrogen have been investigated. Tungsten oxide films with various O/W atomic ratios from 1.5 to 3.0 are prepared using a reactive rf magnetron sputtering at different oxygen partial pressures. The crystallographic structure and O/W atomic ratio of the films were determined by X-ray diffraction and Rutherford backscattering spectroscopy. The stoichiometric WO film with amorphous structure resulted in superior gasochromic coloration. The superior gasochromic performance was realized in stoichiometric WO films with amorphous structure. It suggests that the gasochromic coloration of tungsten oxide films for hydrogen is strongly influenced by the composition and structure.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Miyashita, Atsumi; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(1), p.159 - 162, 2007/03
Ion irradiations with He at 350 keV were performed for the tungsten tri-oxide (WO) films. Gasochromic coloration of the irradiated films was observed by a measurement of optical transmittance with the expose of 1 % hydrogen. The extent of coloration level of the irradiated film with the fluence of ions/sm is 7.5 times lager than that of non-irradiated film. W 4 photoemission spectra for the films were measured by X-ray photoelectron spectroscopy. From the fitting analysis for the spectra, the non-irradiated film has only W. In the irradiated film with the fluence of ions/sm, it is estimated that 17 % and 4 % of the amount of W change into W and W, respectively. The improvement of the gasochromic coloration of the irradiated WO films relates to the increment of oxygen deficient tungstens induced by the irradiation.
Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Takano, Katsuyoshi; Yoshikawa, Masahito; Shikama, Tatsuo*
Transactions of the Materials Research Society of Japan, 32(1), p.107 - 110, 2007/03
We investigated the gasochromic coloration of amorphous tungsten oxide films having compositions between WO and WO. The films were deposited on SiO or glassy carbon substrates by the reactive radio frequency (r. f.) magnetron sputtering with varying oxygen partial pressure. The oxygen and hydrogen concentration of the tungsten oxide films were determined using the Rutherford Backscattering Spectrometry (RBS) and the Elastic Recoil Detection Analysis (ERDA), respectively. The optical transmission was examined for the films coated with palladium catalysis during the exposure of diluted hydrogen gas. Superior gasochromic properties were obtained for the films consisting of tungsten trioxide WO. For the films with lower oxygen concentration than WO, the optical transmission hardly changed during the hydrogen exposure. A large concentration of hydrogen about 0.7 per a tungsten atom was found in the WO films. The hydrogen retention drastically decreased with a decrease of the oxygen concentration.
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
Transactions of the Materials Research Society of Japan, 32(1), p.171 - 174, 2007/03
The gasochromic materials have considerable promise as the optical gas sensors. Palladium oxide is known to exhibit optical absorbance changes due to the reduction reaction with hydrogen gas. However, the gasochromic performance of palladium oxide films is strongly influenced by preparation conditions, such as a heat-treatment temperature. We investigate the correlation between of oxidation temperature of Pd films and the gasochromic performance for hydrogen. Palladium oxide films are prepared by thermal oxidation of the Pd films at temperature ranging from 300 to 900C in air. The gasochromic performance of palladium oxide films coated with Pd catalyst was examined by optical transmission in 1% hydrogen with argon gas. The palladium oxide film, thermally oxidized at 600C in air, shows the good gasochromic performance. The results should lead to an optimization of preparation conditions to provide the gasochromic films used for the optical hydrogen sensors.
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Yoshikawa, Masahito
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 160, 2007/02
Gasochromic properties for hydrogen gas on tungsten oxide thin films have been investigated for an optical hydrogen gas sensors. The gasochromic properties are considered to relate to oxygen vacancies or defects in the tungsten oxide. In this study, it is tried to make oxygen vacancies or defects in the tungsten oxide thin films by ion beam irradiation, to investigate the relation between the amount of fluency and the gasochromic properties. The coloration for 1 % hydrogen was measured by time resolved optical spectroscopy with 630 nm light. The coloration is enhanced with the increasing the fluence, over ions/cm.
Inoue, Aichi; Nagata, Shinji*; Shikama, Tatsuo*; Yamamoto, Shunya; Takano, Katsuyoshi
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 147, 2007/02
no abstracts in English
Nagata, Shinji*; Yamamoto, Shunya; Inoue, Aichi; Tsuchiya, Bun*; To, Kentaro*; Takano, Katsuyoshi; Yoshikawa, Masahito; Shikama, Tatsuo*
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 148, 2007/02
no abstracts in English
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 159, 2007/02
no abstracts in English
Takano, Katsuyoshi; Yamamoto, Shunya; Yoshikawa, Masahito; Inoue, Aichi; Sugiyama, Akira
Transactions of the Materials Research Society of Japan, 31(1), p.223 - 226, 2006/03
no abstracts in English
Inoue, Aichi; Takano, Katsuyoshi; Yamamoto, Shunya; Yoshikawa, Masahito; Nagata, Shinji*
Transactions of the Materials Research Society of Japan, 31(1), p.227 - 230, 2006/03
no abstracts in English
Asano, Yoshihiro; Kishi, Noriyuki*; Moriya, Takahiro*; Miura, Yuta*; Inoue, Katsuaki*
AIP Conference Proceedings 705, p.568 - 571, 2004/04
no abstracts in English
Takano, Katsuyoshi; Yamamoto, Shunya; Inoue, Aichi; Yoshikawa, Masahito
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Takano, Katsuyoshi; Yamamoto, Shunya; Yoshikawa, Masahito; Inoue, Aichi
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no abstracts in English
Yamamoto, Shunya; Takano, Katsuyoshi; Inoue, Aichi; Yoshikawa, Masahito
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no abstracts in English
Inoue, Aichi; Nagata, Shinji*; Shikama, Tatsuo*; Yamamoto, Shunya; Takano, Katsuyoshi; Yoshikawa, Masahito
no journal, ,
no abstracts in English
Nagata, Shinji*; Inoue, Aichi; To, Kentaro*; Tsuchiya, Bun*; Shikama, Tatsuo*; Yamamoto, Shunya; Takano, Katsuyoshi; Yoshikawa, Masahito
no journal, ,
no abstracts in English
Takano, Katsuyoshi; Inoue, Aichi; Yamamoto, Shunya; Yoshikawa, Masahito
no journal, ,
Tungsten oxide has been studied as a gasochromic material to apply to optical hydrogen gas sensors. The gasochromic coloration of tungsten oxide exposing hydrogen is related to a defect of oxygen atoms in the crystal of tungsten oxide. In this study, the gasochromic coloration of tungsten oxide films irradiated by helium ion beam at 350 keV was investigated, to create the defect by ion beam irradiation. Then the gasochromic coloration were measured an optical transmission. The coloration is enhanced with the increasing the amount of irradiation in 350 keV beam than un-irradiated samples. Therefore, the gasochromic coloration can be improved by ion beam irradiation.