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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

A Development of super radiation-hardened power electronics using silicon carbide semiconductors; Toward MGy-class radiation resistivity

Hijikata, Yasuto*; Mitomo, Satoshi*; Matsuda, Takuma*; Murata, Koichi*; Yokoseki, Takashi*; Makino, Takahiro; Takeyama, Akinori; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; et al.

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.130 - 133, 2015/11

Journal Articles

Effect of humidity and temperature on the radiation response of SiC MOSFETs

Takeyama, Akinori; Matsuda, Takuma; Yokoseki, Takashi; Mitomo, Satoshi; Murata, Koichi; Makino, Takahiro; Onoda, Shinobu; Tanaka, Yuki*; Kandori, Mikio*; Yoshie, Toru*; et al.

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.134 - 137, 2015/11

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

Development of the RAQM2 aerosol chemical transport model and predictions of the Northeast Asian aerosol mass, size, chemistry, and mixing type

Kajino, Mizuo*; Inomata, Yayoi*; Sato, Keiichi*; Ueda, Hiromasa*; Han, Z.*; An, J.*; Katata, Genki; Deushi, Makoto*; Maki, Takashi*; Oshima, Naga*; et al.

Atmospheric Chemistry and Physics, 12(24), p.11833 - 11856, 2012/12

 Times Cited Count:43 Percentile:78.96(Environmental Sciences)

A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model and achieved completely dynamic solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super micro m. To consider a variety of atmospheric aerosol properties, a category approach is utilized: aerosols are distributed into 4 categories, Aitken, accumulation, soot aggregates, and coarse mode. A regional-scale simulation was performed for the entire year of 2006, covering Northeast Asian region. Statistical analysis showed the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. Modeled size distributions of total weight and chemical components were consistent with the observations, indicating simulations of aerosol mixing types were successful.

Journal Articles

Gas permeation property of SiC membrane using curing of polymer precursor film by electron beam irradiation in helium atmosphere

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

Materials Transactions, 52(6), p.1276 - 1280, 2011/06

 Times Cited Count:15 Percentile:65.43(Materials Science, Multidisciplinary)

SiC membranes were prepared using curing of precursor polymer (polycarbosilane, PCS) film by electron beam irradiation in helium atmosphere. The membrane prepared via curing of PCS film coated using 10 mass % PCS solution for dip-coating followed by immersing it for 30 s in PCS solution, showed H$$_{2}$$ permeance of 3.1$$times$$10$$^{-7}$$ mol/m$$^{2}$$/s/Pa and the selectivity of 51 at 523 K. The H$$_{2}$$ permeance of the membrane was increased proportional to the temperature by the activated diffusion of H$$_{2}$$. It indicates SiC film without pinholes or cracks formed on the support. As the pyrolysis temperature of cured PCS film was increased, the selectivity of the membrane reached the maximum at 923 K.

JAEA Reports

Photocatalytic activity of Sulfur-doped TiO$$_{2}$$ fiber under visible light illumination (Joint research)

Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Hasegawa, Yoshio*; Awatsu, Satoshi*

JAEA-Research 2007-012, 29 Pages, 2007/03

JAEA-Research-2007-012.pdf:3.77MB

The Sol-Gel derived precursor fiber was annealed under hydrogen disulfeid (H$$_{2}$$S) following oxygen atmosphere, Sulfer-doped titanium dioxide (TiO$$_{2}$$) fiber was obtained. Crystal structure of the fiber was identified as anatase phase of TiO$$_{2}$$. The energy band gap of the fiber was narrower by about 0.06 eV than that of anatase, which showed that it could absorb visible light. The fiber contains about 0.58 atomic % of Sulfer, and they located at the oxygen lattice site of TiO$$_{2}$$. Under visible light illumination, the fiber degraded Trichroloethylen (TCE) and produced carbon dioxide (CO$$_{2}$$). This shows Sulfer-doped TiO$$_{2}$$ fiber has the photocatalytic activity under visible light illumination.

Journal Articles

Blister formation in rutile TiO$$_{2}$$(100) films by helium irradiation

Yamamoto, Shunya; Nagata, Shinji*; Takeyama, Akinori; Yoshikawa, Masahito

Nuclear Instruments and Methods in Physics Research B, 249(1-2), p.374 - 376, 2006/08

 Times Cited Count:8 Percentile:52.29(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Characterization of sulfur-doped TiO$$_{2}$$ films by RBS/C

Yamamoto, Shunya; Takeyama, Akinori; Yoshikawa, Masahito

Nuclear Instruments and Methods in Physics Research B, 242(1-2), p.377 - 379, 2006/01

 Times Cited Count:9 Percentile:52.29(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Blister formation in rutile TiO$$_{2}$$ (100) thin films by helium ion implantation

Yamamoto, Shunya; Nagata, Shinji*; Takeyama, Akinori; Yoshikawa, Masahito

Transactions of the Materials Research Society of Japan, 30(3), p.789 - 792, 2005/09

no abstracts in English

Journal Articles

Formation of Cu precipitates by ion implantation and thermal annealing for the growth of oxide nanorods

Takeyama, Akinori; Yamamoto, Shunya; Ito, Hiroshi; Yoshikawa, Masahito

Nuclear Instruments and Methods in Physics Research B, 232(1-4), p.333 - 337, 2005/05

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

Cu precipitates were formed on Si(100) by 200 keV Cu ion implantation and subsequent annealing at 773 K. The shape of the Cu precipitates evolved from a large rectangle to a small elongated pyramid with increasing annealing time. This shape evolution seemed to result from the epitaxial formation of Cu precipitates to minimize the interfacial energy between the precipitate and the Cu implanted substrate. The average density of Cu precipitates monotonously increased and the average diameter of Cu precipitates decreased with increasing annealing time up to 1 h. These indicate that the morphology, size and average density of Cu precipitates can be controlled by varying annealing time, and that Cu ion implantation and subsequent annealing were effective in producing a substrate dispersed with catalytic particles for oxide nanorods growth.

Journal Articles

Growth of ZnO nanorods on Cu implanted substrates

Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Ito, Hiroshi

Japanese Journal of Applied Physics, Part 1, 44(1B), p.750 - 753, 2005/01

 Times Cited Count:0 Percentile:0(Physics, Applied)

Pyramid shaped Cu precipitates were formed on Si (100) surface as a result of 200 keV Cu ion implantation and subsequent annealing. Then, ZnO nanorods were successfully synthesized on the Cu implanted substrates by chemical vapor transport (CVT). Hexagonal shaped nanorods with a diameter of 200 nm were grown nearly perpendicular to the Cu implanted substrate and their average density was increased as increasing that of Cu precipitates. The facts strongly indicate the Cu precipitates served as the catalytic particles for the growth of ZnO rods.

Oral presentation

Growth of ZnO rods using catalytic particles dispersed on the Cu ion-implanted substrate

Takeyama, Akinori; Yamamoto, Shunya; Ito, Hiroshi; Yoshikawa, Masahito

no journal, , 

no abstracts in English

Oral presentation

Visible photoluminescence of ZnO rods grown on Cu implanted Substrate

Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Ito, Hiroshi

no journal, , 

no abstracts in English

Oral presentation

Hydrogen sensing characteristics of Ag implanted WO$$_{3}$$

Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Ito, Hiroshi

no journal, , 

no abstracts in English

Oral presentation

Gas permeation property of SiC membranes prepared by a dissoution of a precursor film after a coating

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

Hydrogen separation membrane consisted of Silicon Carbide(SiC) thin fim and a SiC intermediate layer was prepared. The intermediate layer was deposited on a porous alumina support by a pylorisis after a coating of the SiC precursor film, an immersion of the film in a solvent and a curing. Maximum hydrogen permeanse and selectivity of the membrane with the "immersed" intermediate layer at 523.15 K was larger than that of the membrane with "un-immersed" layer.

Oral presentation

Gas permeation characteritics of silicon carbide membranes prepared with an immersion of a precursor film

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

Silicon carbide (SiC) films as a hydrogen separation membrane were prepared using a novel preparation technique. The films were obtained by a coating of precursor films on porous alumina supports followed by an immersion into cycohexane, curing in an inert atmosphere and pyrolisis. A selectivity of the film, which is defined as the ratio of the amount of hydrogen (H$$_{2}$$) to nitrogen (N$$_{2}$$) which passed thorough the membrane, was increased up to 6.1 as increasing the immersion time. This is supposed that precursor in pores is dissolved by cyclohexane and pores are filled with the precursor solution, which leads to a decrease of the pore diameter and an improvement of the selectivity.

Oral presentation

Gas permeation property of SiC membranes deposited on SiC intermediate layer

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

no abstracts in English

Oral presentation

Fabrication of ceramic gas separation membranes by EB crosslinking without oxygen

Sugimoto, Masaki; Takeyama, Akinori; Yoshikawa, Masahito

no journal, , 

SiC membranes synthesized from precursor polymers have an excellent thermal and corrosion resistances and the structure is amorphous with nano-hole which has gas permeability. Therefore, the membranes are expected as a hydrogen separation filter that can be used in the severe environment. However, the improvement of the amount of the hydrogen penetration and the separation ratio is required. In this research, the possibility of controlling the gas penetration of the SiC membranes by EB crosslinking technique was examined.

Oral presentation

Stability of silicon carbide membrane prepared from polymer precursor in steam

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

Precursor-derived silicon carbide (SiC) membrane has been a promising candidate as a membrane for hydrogen separation in harsh condition. In this report, SiC membrane was exposed to steam and its gas permeances were measured. Polymer precursor, polycarbosilane (PCS) film was coated on a porous support.Subsequently, it was cured and cross-linked by an electron beam irradiation in helium atmosphere followed by the pyrolysis at 973 K or 1073 K. A series of preparation procedure was repeated three times to layer SiC film. Prepared membrane was exposed to steam at 773 K for 10 hours. Water vapor pressure was about 47 kPa. H$$_{2}$$ permeance of as-prepared membrane prepared via pyrolysis at 1073 K followed Arrhenius plot against the reciprocal temperature. This meanes H$$_{2}$$ permeated through the membrane by molecular sieving mechanism. H$$_{2}$$ permeance still followed Arrhenius plot after the exposure to steam. H$$_{2}$$ permeance of as-prepared membrane prepared via pyrolysis at 973 K also followed Arrhenius plot. However, the membrane was subject to oxidation by steam, consequently large sized pores for Knudsen diffufion of H$$_{2}$$ were formed in the membrane after the exposure.

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