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

https://doi.org/10.1016/j.jascer.2015.08.003

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

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

https://doi.org/10.5194/acp-12-11833-2012

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.

Photocatalytic activity of Sulfur-doped TiO 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 (HS) following oxygen atmosphere, Sulfer-doped titanium dioxide (TiO) fiber was obtained. Crystal structure of the fiber was identified as anatase phase of TiO. 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. Under visible light illumination, the fiber degraded Trichroloethylen (TCE) and produced carbon dioxide (CO). This shows Sulfer-doped TiO fiber has the photocatalytic activity under visible light illumination.

Characterization of sulfur-doped TiO 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

https://doi.org/10.1016/j.nimb.2005.08.077

no abstracts in English

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

https://doi.org/10.1016/j.nimb.2005.03.068

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.

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.

Optimum structures for -ray radiation resistant SiC-MOSFETs

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

no journal, , 

Oxide thickness dependence of -ray irradiation response on Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) was investigated. As a result of irradiation, the threshold voltage V for both SiC MOSFETs with gate oxide of 30 nm or 60 nm thick shifted to negative voltage-side gently. However, the V for 60 nm thick more immediately decreased over 400 kGy. It is found that SiCMOSFETs with smaller thickness has a higher radiation tolerance.

Tolerance of spin-Seebeck thermoelectricity against gamma ray irradiation

Okayasu, Satoru; Takeyama, Akinori*; Oshima, Takeshi*; Harii, Kazuya*; Ieda, Junichi; Ishida, Masahiko*; Saito, Eiji

no journal, , 

We are investigating the applications of spintronics devices in atomic fields. We reported the Tolerance of spin-Seebeck thermoelectricity against heavy swift ion irradiation previously. The tolerance of spin-Seebeck thermoelectricity against gamma ray irradiation will be reported at this conference. The spin thermoelectric properties after gamma ray irradiation up to 1MGy at room temperature and at 150C will be reported.

Swelling of radiation-cured polycarbosilane during pyrolysis

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

Inorganic membrane prepared from thermally stable precursor-derived silicon carbide (SiC) has been paid attention for the use of hydrogen or carbon dioxide separation. For preventing formation of defects called as pinholes or cracks in the membrane, volume shrinkage of polymer precursor, polycarbosilane (PCS) should be as small as possible when PCS is converted into SiC. We aim at revealing mechanism for prevention of the volume shrinkage of PCS powder during pyrolysis. With increasing the pyrolysis temperature from 673 K to 823 K, density of pyrolyzed PCS powder was decreased, whilst calculated volume change was increased, indicating PCS powder swelled. Furthermore, increased amount of total pore volume compared with that of un-pyrolyzed powder was observed in the same temperature range. We found volume shrinkage of PCS powder was relieved by swelling.