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Journal Articles

Relation between the structure and tolerance factor for perovskite-type oxyfluorides

Katsumata, Tetsuhiro*; Inaguma, Nobuyuki*; Mori, Daisuke*; Aimi, Akihisa*; Yoneda, Yasuhiro

Seramikkusu, 54(9), p.629 - 632, 2019/09

Crystal structure analysis of ABO$$_3$$ perovskite-type oxyfluoride were performed by using high-energy synchrotron X-ray measurement. The effect of tolerance factor appeared in the local structure. The average structure of perovskite-type oxyfluoride found to be a cubic structure in the traditional crystal structure analysis.

Journal Articles

Local structure analysis of ferroelectric materials by collaborating XAFS and PDF

Yoneda, Yasuhiro

Seramikkusu, 51(10), p.689 - 693, 2016/10

We report the results of synchrotron X-ray studies of BaTiO$$_3$$ and NaNbO$$_3$$. These materials occur ferroelectric phase transitions in which the average structure changes from a tetragonal to rhombohedral structure. However, the refinements of local structures indicates that the structures in ferroelectric phases have the rhombohedral symmetry. The middle-range order structure of BaTiO$$_3$$ and collaboration between PDF and XAFS in NaNbO$$_3$$ are also discussed.

Journal Articles

Development and application of large bore ceramic ring for DC 1MV vacuum insulation

Tobari, Hiroyuki; Hanada, Masaya; Matsuyama, Hisayoshi*; Morikawa, Kazufumi*

Seramikkusu, 49(12), p.1050 - 1055, 2014/12

In ITER neutral beam injector, a large bore ceramic ring (1.56 m in outer diameter, 50 mm in thickness) for HV bushing has been required, which acts as an insulating feedthrough from gas-insulated transmission line of 1 MV power supply to beam source in vacuum. However, maximum outer diameter was limited less than 1 m in an early phase of development. Development of manufacturing technology of large bore ceramic ring up to $$phi$$1.56 m was a critical issue for ITER HV bushing. In this paper, R&Ds on large bore ceramic ring; a development of new forming method of such a large ring, optimization of sintering method and verification test of high-voltage holding capability toward ITER HV bushing in JAEA are presented.

Journal Articles

Evaluation methods of the failure behavior of SiC/SiC composites with a scope of their application under severe environments

Nozawa, Takashi

Seramikkusu, 49(12), p.1034 - 1039, 2014/12

The small specimen test technique is a viable method for nuclear reactor materials irradiation because of reducing irradiation volume, radioactivity, and waste. It is important to develop the evaluation method to consider unique failure behavior of composites since composites generally show anisotropy due to discontinuity among various constituents with finite size. This paper reviewed recent progress of failure evaluation by various modes and summarized requirements and issues about the small specimen test techniques for composites. Finally, we discussed future perspectives of the small specimen test techniques toward standardization.

Journal Articles

Design of sulfuric acid decomposer made of SiC for IS process hydrogen production method

Takegami, Hiroaki

Seramikkusu, 48(1), p.28 - 32, 2013/01

no abstracts in English

Journal Articles

Development of novel magnetic semiconductor

Maekawa, Sadamichi

Seramikkusu, 46, P. 1072, 2011/12

no abstracts in English

Journal Articles

Tritium accountancy and storage by hydrogen adsorption alloy in fusion fuel cycle

Yamanishi, Toshihiko; Hayashi, Takumi; Kawamura, Yoshinori

Seramikkusu, 46(3), p.201 - 205, 2011/03

The fusion fuel cycle is composed of isotope separation, impurity processing, and tritium storage systems. The tritium is a fuel of fusion reactor, and the tritium storage system recovering and supplying tritium plays an important role in the fuel cycle. There are several alloys which can be used for the storage of tritium; ZrCo alloy has been applied for ITER from the following reasons. The alloy of ZrCo is quite stable in comparison with Uranium. The equilibrium pressure is quite low at room temperature. In this report, recent activities and results on this ZrCo tritium storage bed has been described. Some important ceramic materials, which have been used for hydrogen recovery as the proton conductors, are also reported.

Journal Articles

High-pressure synthesis of aluminum hydride by ${it in situ}$ synchrotron radiation X-ray diffraction measurement

Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori; Aoki, Katsutoshi

Seramikkusu, 46(3), p.178 - 182, 2011/03

The AlH$$_{3}$$ sample prepared at 10 GPa, 650 $$^{circ}$$C contained high-quality single crystals. Crystallinity of the AlH$$_{3}$$ single crystal was characterized by an X-ray oscillation photograph taken at BL22XU beamline of SPring-8. This result have posed a question: how such high-quality single crystals can grow through the hydrogenation given the significant modification in unit cell structure and the accompanying volume expansion of the host metal lattice. In this paper, we will show the formation and crystal growth process of AlH$$_{3}$$.

Journal Articles

Production of nuclear fusion reactor fuel by ceramic tritium breeder material

Kawamura, Yoshinori; Ochiai, Kentaro; Hoshino, Tsuyoshi

Seramikkusu, 46(3), p.206 - 209, 2011/03

Fuel tritium is generated from the nuclear reaction between the fusion neutron and the lithium of the breeder material arranged in the blanket that encloses the fusion plasma in the fusion reactor. However, the release process of the generated tritium has not been completely clarified. Recently, Japan Atomic Energy Agency started the tritium generation and recovery experiment in using nuclear fusion neutron source (FNS). In this report, the recent results of study on breeder material and its manufacturing technology is presented.

Journal Articles

Local structural analysis on crystalline materials by using atomic Pair Distribution Function (PDF)

Kodama, Katsuaki

Seramikkusu, 43(11), p.909 - 916, 2008/11

The concept of atomic pair distribution function and the experimental method which obtains PDF, are shown in detail. As examples of the applications of PDF analyses to crystalline materials, we introduce the relation between local structural distortion and negative thermal expansion observed in giant negative thermal expansion material Mn$$_3$$Cu$$_{1-x}$$Ge$$_x$$N, and the observation of domain structure with lower symmetry in bulk sample of multiferroic material BiMnO$$_3$$.

Journal Articles

SiC-based ceramic fibers prepared via organic-to-inorganic conversion process; A Review

Okamura, Kiyohito*; Shimoo, Toshio*; Suzuya, Kentaro; Suzuki, Kenji*

Nihon Seramikkusu Kyokai Gakujutsu Rombunshi, 114(1330), p.445 - 454, 2006/06

 Times Cited Count:45 Percentile:75.76(Materials Science, Ceramics)

Several types of Si-based ceramic fibers have been prepared using an organic-to-inorganic conversion process. In this article, the preparation, microstructure, and high-temperature stability of SiC-based ceramic fibers prepared from polycarbosilane of an organosilicon polymer are reviewed. The first fiber produced was an amorphous Si-C-O fiber, next was a low-oxygen content Si-C fiber, and finally, a nearly stoichiometric SiC fiber was developed. These fibers are continuous fine fibers that have high tensile strength with high heat resistance. The pyrolytic behavior and active-passive oxidation of these fibers at high temperatures are described here. The heat resistance of these fibers increases in the order of the Si-C-O fiber, the Si-C fiber, and the SiC fiber. The high-temperature properties are dependent on the atomic arrangement and the quantity of amorphous SiC$$_{x}$$O$$_{y}$$ and glassy carbon in the fibers.

Journal Articles

Graphite components in the high temperature gas-cooled reactors

Ishihara, Masahiro

Seramikkusu, 39(10), p.834 - 837, 2004/10

no abstracts in English

Journal Articles

Tritium breeders and tritium permeation barrier coatings for fusion reactor

Yamawaki, Michio*; Kawamura, Hiroshi; Tsuchiya, Kunihiko

Seramikkusu, 39(10), p.843 - 848, 2004/10

no abstracts in English

Journal Articles

Coated particle fuel for high-temperature gas-cooled reactors

Minato, Kazuo

Seramikkusu, 39(10), p.830 - 833, 2004/10

no abstracts in English

Journal Articles

Development of Rock-like Oxide Fuel, an innovative nuclear fuel for burning plutonium

Yamashita, Toshiyuki

Seramikkusu, 39(10), p.817 - 821, 2004/10

no abstracts in English

Journal Articles

Influence of TiO$$_{2}$$ and Na$$_{2}$$O additives on properties synthetic rock of fly ash from municipal waste incinerator

Mitamura, Hisayoshi; Bamba, Tsunetaka; Maeda, Toshikatsu

Nihon Seramikkusu Kyokai Gakujutsu Rombunshi, 110(1277), p.55 - 59, 2002/01

 Times Cited Count:1 Percentile:19.97(Materials Science, Ceramics)

Influence of additives and hot-pressing temperature on properties of the synthetic rock was investigated, which was developed for making harmless and stabilizing fly ash from municipal waste incinerator. Sintering test at 1200$$^{circ}$$C for 16 h revealed that addition of 20 and 1.5 wt% of TiO$$_{2}$$ and Na$$_{2}$$O, respectively, is necessary for preparation of dense products. X-ray diffractometry showed that these additives promoted the formation of perovskite (CaTiO$$_{3}$$) and gehlenite (Ca$$_{2}$$Al$$_{2}$$SiO$$_{7}$$) minerals. During hot pressing, bulk density of the synthetic rock increased steeply with temperature between 1000 and 1100$$^{circ}$$C. On the other hand, its open porosity decreased rapidly with temperature between 1050 and 1150$$^{circ}$$C. These facts imply that the temperature of 1100$~{}1$150$$^{circ}$$C is practical in hot pressing of fly ash.

Journal Articles

Structural studies on ceramic thin films by X-ray anomalous diffraction

Mizuki, Junichiro

Seramikkusu, 33(8), p.620 - 624, 1998/00

no abstracts in English

Journal Articles

Development of B$$_{4}$$C-carbon fiber composite ceramics as plasma facing materials in nuclear fusion reactor, part 3; Heat resistance evaluation by electron beam irradiation and by in situ plasma discharge in JT-60

*; Saido, Masahiro; Nakamura, Kazuyuki; Akiba, Masato; ; Dairaku, Masayuki; *; *; *; Goto, Yoshitaka*

Nihon Seramikkusu Kyokai Gakujutsu Rombunshi, 105(1228), p.1091 - 1098, 1997/12

 Times Cited Count:1 Percentile:19.15(Materials Science, Ceramics)

no abstracts in English

Journal Articles

Fabrication of SiC devices by ion implantation; Technique and evaluation

Oshima, Takeshi

Nyu Seramikkusu, 10(5), p.20 - 27, 1997/05

no abstracts in English

Journal Articles

Alpha-decay damage of perovskite

; Bamba, Tsunetaka; Muraoka, Susumu

Nyu Seramikkusu, 9(11), p.23 - 29, 1996/11

no abstracts in English

30 (Records 1-20 displayed on this page)