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Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito
Innovative Processing and Manufacturing of Advanced Ceramics and Composites II; Ceramic Transactions, Vol.243, p.61 - 69, 2014/01
A macroporous SiC material was synthesized from polycarbosilane (PCS) by direct foaming and radiation curing. A mixture of PCS and biurea, a blowing agent, was heat-treated in Ar to obtain foamed PCS body, irradiated by 
-rays to fix the shaped body and finally pyrolyzed at 1000
C in Ar. In this work, effects of foaming temperature (280-320C) and biurea content (0-1wt%) on the properties of obtained porous SiC material such as average cell size, porosity, compressive strength were investigated. It was found that the average cell size increased as foaming temperature and/or biurea content increased. Corresponding to increasing in average cell size, total porosity and open porosity increased and bulk density, closed porosity and compressive strength decreased. In case of the foaming at 280C with biurea content of 1wt%, obtained porous SiC material showed average cell size of 0.5 mm, total porosity of 74% and compressive strength of 3.2 MPa.
Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito
Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.7 - 12, 2010/07
Recently, catalyst-loaded ceramic materials have been developed to apply for gas separators in the engineering field of hydrogen generation. Oxide ceramics of alumina and silica are used for the matrix in that field. However, the oxide ceramics are inferior to non-oxide ceramics in the point of resistance for high temperature, strong acid or alkali, hot steam, and so on. Si-based polymers are used as precursors for Si-based non-oxide ceramics. They have a good point of high formability and ability to form polymer blends with various materials. So far, we have established a fabrication technique of SiC products such as a fine fiber with average diameter of 6
m and a membrane for hydrogen separation. In this work, we fabricate a catalyst-loaded SiC material from a blend of Si-based polymer and transition metal compound. The catalyst-loaded SiC material showed a catalytic performance of evolution of CO
gas oxidizing CO gas.
Kita, Kenichiro; Narisawa, Masaki*; Nakahira, Atsushi*; Mabuchi, Hiroshi*; Ito, Masayoshi*; Sugimoto, Masaki; Yoshikawa, Masahito
Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.45 - 50, 2010/06
Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Watanabe, Shogo*; Seki, Shu*
Advances in Polymer Derived Ceramics and Composites; Ceramic Transactions, Vol.213, p.105 - 110, 2010/06
We have succeeded in synthesizing ceramic nano fibers from precursor polymers using Single Particle Nanofabrication Technique (SPNT). A thin film of the precursor polymer was cross-linked by MeV-order heavy-ion beam irradiation along ion tracks of nano-size in radius through the whole thickness of the thin film. Nano fibers were developed on the surface of the substrate by dissolution and washing away of un-crosslinked polymer. Subsequent pyrolysis converted polymeric into ceramic nano fibers. The radius, length and number density of nano fibers are controlled by liner energy transfer (LET) of ion beam, thickness of polymeric target and number of projected ions, respectively.
Taguchi, Tomitsugu; Igawa, Naoki; Jitsukawa, Shiro; Nozawa, Takashi*; Kato, Yudai*; Koyama, Akira*; Snead, L. L.*; McLaughlin, J. C.*
Advanced SiC/SiC Ceramic Composites: Developments and Applications in Energy Systems; Ceramic Transactions Vol. 144, p.69 - 76, 2002/00
Process optimization for Forced-thermal gradient Chemical Vapor Infiltration (FCVI) fabrication of 75 mm diameter size SiC composites with advanced SiC fibers; Hi-Nicalon Type S and Tyranno SA, was carried out. The SiC/SiC composites fabricated by FCVI exhibited significant reduction in porosity (15.1%) and more uniform pore distribution by decreasing the MTS and H gases flow rates in the latter part of the FCVI process. The tensile strength of the both composites using Hi-Nicalon Type S or Tyranno SA fibers was slightly increased with increased thickness of carbon interphase in the range of 75-300 nm. In order to perform the comparative testing required to directly compare the thermomechanical property changes following neutron irradiation, larger composites with uniform microstructural property are required. From the results of process optimization for fabrication of 75 mm diameter size FCVI SiC/SiC composites, the definitive purpose in this study is the fabrication of the 300 mm diameter size SiC/SiC composite with the uniform microstructural properties.
Yamada, Reiji; Igawa, Naoki; Taguchi, Tomitsugu
Advanced SiC/SiC Ceramic Composites: Developments and Applications in Energy Systems; Ceramic Transactions Vol. 144, p.289 - 299, 2002/00
A Finite-element method(FEM) was applied for a computer simulation of a laser flash method for measuring thermal diffusivity of SiC/SiC composites. To understand the effect of individual fiber and matrix thermal conductivities as well as fiber volume on the overall composite's thermal diffusivity, the cases of high and low values for the fiber and matrix thermal conductivities were calculated as a function of fiber volume fraction at specimen temperatures of 200 and 900
. The results of calculations showed that if low thermal conductive SiC fibers were used, the increase of fiber volume worsened the composite thermal diffusivity with highly conductive matrix, whereas when using highly conductive SiC fiber, the effect of increasing fiber volume was positive for increasing the composite diffusivity with low matrix thermal conductivity. The specimen temperatures altered the values of the composite thermal diffusivity but the qualitative tendencies above mentioned were maintained.
NbO
(0.5≦x≦2)Nakamura, Akio; ; Nakada, Masami; Saeki, Masakatsu; *; Akimitsu, Jun*
Ceramic Transactions, 71, p.295 - 306, 1996/00
no abstracts in English
Igawa, Naoki; Ono, Hideo; Nagasaki, Takanori; Ishii, Yoshinobu; Noda, Kenji; Watanabe, H.; Matsuo, Toru*; Igarashi, Kazuo*
Ceramic Transactions, Vol.27, p.135 - 156, 1992/00
no abstracts in English