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.

Visible photoluminescence of ZnO rods grown on Cu implanted Substrate

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

no journal, , 

no abstracts in English

Structural evolution of polymer precursor of silicon carbide ceramics during pyrolysis

Takeyama, Akinori; Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

In order to prepare crack-free silicon carbide hydrogen separation membrane, how volume shrinkage or expansion of polymer precursor, polycarbosilne (PCS) take places when it is converted into silicon carbide ceramics during pysolysis was investigated. PCS powder cured by electron beam irradiation with several dose of 12,16,18,24 MGy in helium atmosphere was pysolysed at 923 K to convert them into SiC ceramic powder. As the dose was increased, ceramic yield was gradually increased, indicating amount of decomposed gas evolved during pyrolysis was decreased. Density of obtained SiC ceramic powders was decreased with increasing dose. By electron beam irradiation, network structure of PCS was developed and decomposition gas seemed to be easily accumulated in the network structure. It follows that PCS powder swelled as decomposition gas was accumulated and swelling was lowered density of SiC ceramic powders. Furthermore, surface area of SiC ceramic powder was increased from 0 m/g for 12 MGy to 0.6 m/g for 24 MGy by swelling. Consequently, swelling suppressed volume shrinkage of PCS powder during pyrolysis.

Gas permeation property of SiC membranes deposited on SiC intermediate layer

Takeyama, Akinori; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

no abstracts in English

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.