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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

Investigation of nano porous SiC based fibers synthesized by precursor method

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

Journal Articles

Synthesis and properties of ceramic fibers from polycarbosilane/polymethylphenylsiloxane polymer blends

Kita, Kenichiro; Narisawa, Masaki*; Nakahira, Atsushi*; Mabuchi, Hiroshi*; Sugimoto, Masaki; Yoshikawa, Masahito

Journal of Materials Science, 45(13), p.3397 - 3404, 2010/04

 Times Cited Count:9 Percentile:32.88(Materials Science, Multidisciplinary)

We synthesized ceramic fibers based on silicon carbide (SiC) from polymer blends of polycarbosilane (PCS) and polymethylphenylsiloxane (PMPhS). PMPhS was compatible with PCS up to 30 mass%. The polymer blend was formed a transparent melt at temperatures higher than 513 K and the softening point was also lowered by adding PMPhS. 15 mass% of PMPhS to PCS was the most suitable condition for obtaining thin fibers with an average diameter of 14.4 $$mu$$m and the ceramic yield of the cured fiber was 85.5% after pyrolysis at 1273 K. In spite of the small diameter, the resulting tensile strength at 1273 K was rather limited at 0.78 GPa. After high temperature pyrolysis at 1673$$sim$$1773 K, a porous nanocrystalline SiC fiber with a unique microstructure was obtained with surface area of 70$$sim$$150 m$$^{2}$$/g.

Journal Articles

High-temperature pyrolysis of ceramic fibers derived from polycarbosilane-polymethylhydrosiloxane polymer blends with porous structures

Kita, Kenichiro; Narisawa, Masaki*; Nakahira, Atsushi*; Mabuchi, Hiroshi*; Ito, Masayoshi*; Sugimoto, Masaki; Yoshikawa, Masahito

Journal of Materials Science, 45(1), p.139 - 145, 2010/01

 Times Cited Count:8 Percentile:30.01(Materials Science, Multidisciplinary)

The polymer blends of polycarbosilane (PCS) and polymethylohydrosiloxane with high molecular weight (PMHS-h) were prepared by freeze-drying process. Melt viscosity, themogravimetric analysis, and gas evolution from the polymer blends were analyzed. The polymer blend of HSah15 (15 mass% PMHS-h to PCS) was melt-spun to fiber form, curing by thermal oxidation and pyrolyzed at various temperatures up to 1773 K. The fibers were investigated by tensile tests, FE-SEM observation, and XRD (X-ray diffraction) analysis. After pyrolysis at 1273 K, there were amounts of pores in the cross sections of the fiber derived from HSah15, and after pyrolysis at 1773 K, no remarkable $$beta$$-SiC crystal were formed on the outside surface of the fiber derived from HSah15.

Journal Articles

Formation of continuous pore structures in Si-C-O fibers by adjusting the melt spinning condition of a polycarbosilane - polysiloxane polymer blend

Kita, Kenichiro; Narisawa, Masaki*; Mabuchi, Hiroshi*; Ito, Masayoshi*; Sugimoto, Masaki; Yoshikawa, Masahito

Journal of the American Ceramic Society, 92(6), p.1192 - 1197, 2009/06

 Times Cited Count:10 Percentile:54.02(Materials Science, Ceramics)

Journal Articles

Synthesis of SiC based fibers with continuous pore structure by melt-spinning and controlled curing method

Kita, Kenichiro; Narisawa, Masaki*; Mabuchi, Hiroshi*; Ito, Masayoshi*; Sugimoto, Masaki; Yoshikawa, Masahito

Advanced Materials Research, 66, p.5 - 8, 2009/04

 Times Cited Count:2 Percentile:68.51

Journal Articles

Synthesis of a minute SiC product from polyvinylsilane with radiation curing, 2; Ceramization process of radiation cured polyvinylsilane

Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Journal of Materials Science, 42(1), p.130 - 135, 2007/01

 Times Cited Count:2 Percentile:10.8(Materials Science, Multidisciplinary)

We have synthesized minute SiC products from polyvinylsilane (PVS), which is a liquid organosilicon polymer, with radiation curing. Since there is a close relationship between the properties of obtained SiC products and pyrolysis condition, it is important to investigate the ceramization process of PVS in order to find out the optimum pyrolysis condition. In this paper, the ceramization process of the PVS cured by $$gamma$$-ray irradiation at room temperature was investigated by gas analysis, thermogravimetric analysis, density measurement, and so on. It was found that the ceramization of $$gamma$$-ray cured PVS starts above 500K, and that drastic organic-inorganic conversion occurs in the temperature range of 700-1100K. According to the results of the changes of mass and density, it was found that the volume shrinkage of PVS during the curing and pyrolysis processes is 80%. The SiC obtained by pyrolysis at 1573K showed the density of 2.50g/cm$$^{3}$$ and microvickers hardness of 31.6GPa.

Journal Articles

Synthesis of a minute SiC product from polyvinylsilane with radiation curing, 1; Radiation curing of polyvinylsilane

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Journal of Materials Science, 39(18), p.5689 - 5694, 2004/09

 Times Cited Count:6 Percentile:29.02(Materials Science, Multidisciplinary)

Irradiation effect of $$gamma$$-ray on polyvinylsilane (PVS), which is a liquid organosilicon polymer, was investigated and the optimum curing condition to synthesize a minute SiC product with radiation curing was discussed. Room temperature and liquid nitrogen temperature (77K) were examined as the irradiation temperature. In both cases, the cured PVS maintaining its formed shape could be obtained by $$gamma$$-ray irradiation under vacuum, and the cured PVS in solid state at room temperature was obtained by irradiation with dose of above 3-4MGy. It was found that the efficiency of crosslinking in case of the irradiation at room temperature is higher than that in case of irradiation at 77K. The PVS injected into a mold was irradiated by $$gamma$$-ray with dose of 3.6MGy at room temperature under vacuum, and pyrolyzed at 1273 K in Ar gas atmosphere. As a result, minute SiC products which had similar shapes to the mold and the sizes of 30-60$$mu$$m were obtained.

Journal Articles

Minute SiC products synthesized from polyvinylsilane with radiation curing

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

International Symposium in Honor of Professor K. Okamura: Collected Abstracts, 3 Pages, 2003/04

Minute SiC products were synthesized from polyvinylsilane (PVS), which is a liquid organosilicon polymer, with radiation curing. The PVS was injected into molds whose patterns were square and circle with 50$$mu$$m in side or diameter, and 10$$mu$$m in depth. The molds containing the PVS were irradiated by $$gamma$$-ray with dose of 3.6MGy at room temperature in vacuum, and heat-treated at 1273K in Ar gas atmosphere. The obtained SiC products had shapes similar to those of the molds, and the sizes of the products were about 30$$mu$$m in side or diameter.

Journal Articles

Radiation curing of polyvinylsilane as a precursor for SiC-based material

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

Key Engineering Materials, 247, p.129 - 132, 2003/00

Polyvinylsilane (PVS), a liquid organosilicon polymer at room temperature, is expected to be used as a precursor for SiC product with minute and complex shape. In the synthesis of the SiC product, it is necessary to cure the polymer in order to retain the shape during the pyrolysis. We have used a radiation for curing of the PVS. However, there is a problem that the PVS foams during electron beam irradiation at room temperature. In this report, the curing of PVS by $$gamma$$-ray irradiation was examined, and effect of irradiation temperature was studied in order to find out conditions that prevent the foaming of PVS. It was found that the PVS is cured without foaming by the $$gamma$$-ray irradiation in both cases of the irradiation temperature at liquid nitrogen temperature (77K) and at room temperature. From the results of measurement of gel fraction and TGA, it was found that the PVS is cured more efficiently by the irradiation at room temperature than at 77K.

Journal Articles

Fine SiC fiber synthesized from organosilicon polymers; Relationship between spinning temperature and melt viscosity of precursor polymers

Idesaki, Akira; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Tanaka, Shigeru; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Journal of Materials Science, 36(23), p.5565 - 5569, 2001/12

 Times Cited Count:36 Percentile:77.69(Materials Science, Multidisciplinary)

A very fine silicon carbide (SiC) fiber with diameter of 6 $$mu$$ m, about a half of that of a commercially available SiC fiber, was synthesized from a polymer blend of polycarbosilane (PCS) and polyvinylsilane (PVS). The fine SiC fiber was obtained by optimizing the composition and the spinning temperature of PCS-PVS polymer blends. In order to determine these optimum conditions, the relationship between temperature and melt viscosities of the polymer blends was investigated. As a result, it was found that the optimum spinning temperature range was within a temperature range where the melt viscosity is 5-10Pa$$cdot$$s. Moreover, by blending PVS with PCS, the spinning temperature of the polymer blends was lowered, the spinnability of polymer system was improved, and finer polymer fiber was obtained compared with PCS. The optimum content of PVS in the polymer blend was 15-20wt%.

Journal Articles

Fine silicon carbide fibers synthesized from polycarbosilane-polyvinylsilane polymer blend using electron beam curing

Idesaki, Akira*; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Journal of Materials Science, 36(2), p.357 - 362, 2001/01

 Times Cited Count:15 Percentile:54.95(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Fine silicon carbide fiber synthesized from a silicon-based polymer blend using radiation curing

Idesaki, Akira; Sugimoto, Masaki; Tanaka, Shigeru; Morita, Yosuke; Narisawa, Masaki*; Okamura, Kiyohito*; Ito, Masayoshi*

High Temperature Ceramic Matrix Composites, p.35 - 40, 2001/00

Silicon carbide (SiC) fiber, which is one of the likeliest candidates as a reinforcement fiber of ceramic matrix composites (CMCs), is synthesized from polycarbosilane (PCS). The diameter of thus SiC fibers is 10-15 $$mu$$m. In order to fabricate CMCs with 3-dimensional complex shapes, it is important to develop a SiC fiber with diameter of less than 10 $$mu$$m, flexibility, and high strength. In order to improve the spinnability of precursor polymer, we have blended polyvinylsilane (PVS), which is a liquid polymer at room temperature, to PCS as a spinning additive. According to relationship between temperature and melt viscosity of the polymer blend, it was found that the polymer can be melt-spun at about 490K, 110K lower than PCS (about 600K), and that the spinnability of the polymer is improved by blending PVS. Fine polymer fiber was obtained from the polymer blend, and finally, very fine SiC fiber with the average diameter of 6 $$mu$$m was synthesized from the PCS-PVS polymer blend.

Journal Articles

Application of electron beam curing for silicon carbide fiber synthesis from blend polymer of polycarbosilane and polyvinylsilane

Idesaki, Akira*; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Proceedings of International Symposium on Prospect for Application of Radiation towards the 21st Century, p.139 - 140, 2000/03

no abstracts in English

Journal Articles

Use of blended precursors of poly(vinylsilane) in polycarbosilane for silicon carbide fiber synthesis with radiation curing

Narisawa, Masaki*; Idesaki, Akira*; *; *; Sugimoto, Masaki; Seguchi, Tadao; Ito, Masayoshi*

Journal of the American Ceramic Society, 82(4), p.1045 - 1051, 1999/00

 Times Cited Count:21 Percentile:76.84(Materials Science, Ceramics)

no abstracts in English

Journal Articles

Synthesis of SiC-based fibers derived from hybrid polymer of polycarbosilane and polyvinylsilane

Idesaki, Akira*; Narisawa, Masaki*; *; Sugimoto, Masaki; Seguchi, Tadao; Ito, Masayoshi*

Key Engineering Materials, 159-160, p.107 - 111, 1999/00

no abstracts in English

Journal Articles

SiC-based fibers synthesized from hybrid polymer of polycarbosilane and polyvinylsilane

Idesaki, Akira*; Narisawa, Masaki*; *; Sugimoto, Masaki; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Key Engineering Materials, 164-165, p.39 - 42, 1999/00

no abstracts in English

Journal Articles

Reaction mechanism of the pyrolysis of polycarbosilane and polycarbosilazane as ceramic precursors

Narisawa, Masaki*; *; *; Sugimoto, Masaki; Seguchi, Tadao

Bulletin of the Chemical Society of Japan, 68, p.1098 - 1104, 1995/00

 Times Cited Count:33 Percentile:81.54(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Electron spin resonance studies in process of ceramics formation from organosilicon polymers

Narisawa, Masaki*; *; Sugimoto, Masaki; *; Seguchi, Tadao

Ceramics,Powders,Corrosion and Advanced Processing (Trans. of Materials Research Soc. Jpn., Vol. 14A), 0, p.827 - 830, 1994/00

no abstracts in English

Oral presentation

The Possibility of synthesis of SiC based micro tube through precursor method

Kita, Kenichiro; Narisawa, Masaki*; Mabuchi, Hiroshi*; Sugimoto, Masaki; Yoshikawa, Masahito

no journal, , 

no abstracts in English

24 (Records 1-20 displayed on this page)