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Kawabori, Tatsuru*; Watanabe, Masashi; Imai, Yoshiyuki; Ueta, Shohei; Yan, X.; Mizoshiri, Mizue*
Applied Physics A, 129(7), p.498_1 - 498_9, 2023/07
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We investigated a potential of femtosecond laser sintering of silicon carbide (SiC) using the nanoparticles in air. A SiC nanoparticle ink including polyvinylpyrrolidone and ethylene glycol exhibited intense absorption by SiC nanoparticles at the wavelength of 780 nm. The whole of the sintered film patterns from the surface to the bottom underwent significant oxidation at a scanning speed of 1 mm/s, suggesting that the excessive energy irradiation generated silicon oxides. In contrast, the patterns fabricated by laser scanning at a raster pitch of 30 
m at which a sintered area was observed at a scanning speed of 5 mm/s, exhibited no significant difference in oxidation of the raw SiC nanoparticles except for the surfaces from 1.72 m. These results indicate that the irradiation of femtosecond laser pulses generated the sintered SiC patterns without additional atmospheric oxidation of the raw materials because of its low heat accumulation. In additions, the dispersant of polyvinylpyrrolidone and ethylene glycol did not affect the sintering by an X-ray photoelectron spectroscopy. This vacuum-free direct printing technique has the potential for additive manufacturing.
Watanabe, Masashi; Yokoyama, Keisuke; Imai, Yoshiyuki; Ueta, Shohei; Yan, X.
Ceramics International, 48(6), p.8706 - 8708, 2022/03
Times Cited Count：8 Percentile：72.1(Materials Science, Ceramics)Previous studies have used various methods for sintering of SiC, carbon, and SiC/carbon functionally graded materials (FGM). However, no experimental studies on SiC/graphite FGM manufacturing using the spark plasma sintering (SPS) method have been reported. In this study, a SiC/graphite FGM specimen has been fabricated using SPS. The interface between the adjacent layers of the sintered specimen exhibits no apparent defects such as gaps or delaminations. The SiC and graphite phases in the specimen show no substantial change before and after sintering.
Watanabe, Masashi; Seki, Takayuki*
Materials Science & Engineering B, 272, p.115369_1 - 115369_6, 2021/10
Times Cited Count：1 Percentile：7.51(Materials Science, Multidisciplinary)The effect of oxygen non-stoichiometry on the initial sintering behavior of CeO
was investigated. It was found that the initial sintering of the stoichiometric and hypo-stoichiometric composition was controlled by the grain boundary diffusion. The activation energies of cation diffusion were derived from initial sintering data. Moreover, it is suggested that the cation diffusion was caused by a vacancy mechanism.
for production of 
Tc radioactive isotopeSuematsu, Hisayuki*; Sato, Soma*; Nakayama, Tadachika*; Suzuki, Tatsuya*; Niihara, Koichi*; Nanko, Makoto*; Tsuchiya, Kunihiko
Journal of Asian Ceramic Societies (Internet), 8(4), p.1154 - 1161, 2020/12
Times Cited Count：3 Percentile：16.44(Materials Science, Ceramics)Pulsed electric current sintering of molybdenum trioxide (MoO) was carried out by one- and two-step pressuring methods for fabrication of irradiation target using production of 
Mo and 
Tc nuclear medicine. At 550
C by the two-step pressurizing method, a relative density of 93.1% was obtained while, by the one-step pressurization method, the relative density was 76.9%. Direct sample temperature measurements were conducted by inserting a thermocouple in a punch. By the two-step pressurizing method, the sample temperature was higher than that by the one-step pressurizing method even almost the same die temperature. From voltage and current waveforms, it was thought that the conductivity of the sample increased by the two-step pressurizing method to increase the sample temperature and the relative density. The two-step pressurization method enables us to prepare dense targets at a low temperature from recycled and coarse-grained 
Mo enriched MoO powder.
Aihara, Jun; Honda, Masaki*; Ueta, Shohei; Ogawa, Hiroaki; Ohira, Koichi*; Tachibana, Yukio
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(1), p.29 - 36, 2019/03
Japan Atomic Energy Agency carried out development of fabrication technology of oxidation resistant fuel element for improvement of safety of high temperature gas-cooled reactors in serious oxidation accident, based on precursor research in former JAEA. Dummy coated fuel particles (alumina particles) were over-coated with mixed powder of Si, C and small amount of resin to form over-coated particles, and over-coated particles were molded and hot-pressed to sinter dummy oxidation resistant fuel elements with SiC/C mixed matrix. We fabricated dummy oxidation resistant fuel elements with matrix whose Si/C mole ratio (about 0.551) is three times as large as that in precursor research. Si peak was not detected by X-ray diffraction of matrix. Better oxidation resistant was confirmed with oxidation test in 20% O at 1673 K than that of ordinal fuel compact with ordinal graphite/carbon matrix. All dummy coated fuel particles were held in specimen after 10 h oxidation.
Mo/Tc production by (n,
) methodNishikata, Kaori; Kimura, Akihiro; Ishida, Takuya; Shiina, Takayuki*; Ota, Akio*; Tanase, Masakazu*; Tsuchiya, Kunihiko
JAEA-Technology 2014-034, 34 Pages, 2014/10
JAEA-Technology-2014-034.pdf:3.26MB
As a part of utilization expansion after the Japan Material Testing Reactor (JMTR) re-start, research and development (R&D) on the production of medical radioisotope Mo/Tc by (n, ) method using JMTR has been carried out in the Neutron Irradiation and Testing Reactor Center of the Japan Atomic Energy Agency. Mo is usually produced by fission method. On the other hand, Mo/Tc production by the (n, ) method has advantages for radioactive waste, cost reduction and non-proliferation. However, the specific radioactivity per unit volume by the (n, ) method is low compared with the fission method, and that is the weak point of the (n, ) method. This report summarizes the investigation of raw materials, the fabrication tests of high-density MoO pellets by the plasma sintering method for increasing of Mo contents and the characterization of sintered high-density MoO pellets.
Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Jitsukawa, Shiro
Journal of Physics and Chemistry of Solids, 66(2-4), p.576 - 580, 2005/02
Times Cited Count：51 Percentile：84.05(Chemistry, Multidisciplinary)SiC/SiC composites are expected to be one of the candidate materials for fusion reactors because of the low radioactivity after neutron irradiation and excellent mechanical properties at high temperature. Reaction-Bonding (RB) process was employed since this process has a possibility of producing a much denser matrix compared with other processes. SiC fibers, however, adhere strongly to the matrix because of high reactiveness of molten Si with the SiC fiber during RB process. In this study, we investigated the effects of SiC layer as an interphase on fracture behavior in the SiC/SiC. The specimen without an interphase layer showed catastrophic failure behavior while the specimen with SiC interphase layer exhibited non-catastrophic failure behavior by 3-point bending testing. The microstructure observation indicated that SiC fibers did not adhere to the matrix in the specimen with SiC interpahse layer. After 3-point bending testing, the pull-out phenomenon occurred in the SiC/SiC with SiC interphase layer while did not occur in the composite without interphase layer.
Ishiyama, Shintaro; Maruyama, Shigeki*
Journal of the Ceramic Society of Japan, Supplement, Vol.112, No.1 (CD-ROM), p.S159 - S166, 2004/05
no abstracts in English
*
JNC TN1400 2001-013, 70 Pages, 2001/08
JNC-TN1400-2001-013.pdf:5.13MB
no abstracts in English
Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Futakawa, Masatoshi; Jitsukawa, Shiro
Ceramic Engineering and Science Proceedings (25th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A), 22(3), p.533 - 538, 2001/03
no abstracts in English
Takago, S.*; Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Hirose, Yukio*
Nihon Zairyo Gakkai Dai-36-Kai X Sen Zairyo Kyodo Ni Kansuru Shimpojiumu Koen Rombunshu, p.266 - 271, 2000/09
no abstracts in English
Takago, S.*; Sasaki, Toshihiko*; Minakawa, Nobuaki; Morii, Yukio; Hirose, Yukio*
Proceedings of 6th International Conference on Residual Stressess (ICRS-6), Vol.1, p.41 - 48, 2000/07
no abstracts in English
Namba, Hideki
Hoshasen Riyo Ni Okeru Saikin No Shimpo, p.162 - 172, 2000/06
no abstracts in English
Kakehi, Isao;
JNC TN9400 2000-054, 84 Pages, 2000/04
JNC-TN9400-2000-054.pdf:7.15MB
This report describes accomplishment of the study on the quality of vipac (vibro-packed) oxide fuel obtained by pyrochemical processing (molten salt electrolytic processing). This study is intended to contribute to the design study of the pyro-reprocessing-vipac fuel recycling system of oxide fuel. In this study, vibro-packing experiment has been conducted using granular U0 obtained by molten salt electrolytic processing (cold experiment). The oxide pyro process developed by Research lnstitute of Atomic Reactors (RIAR) is the method in which the sintered oxide is electrically deposited on the cathode at approximately 600C. 0xide granules for vipac fuel are obtained by crushing the oxide deposited on the cathode. This process is also developed as recycle process because it is capable of FP separation. Also in Japan, this process is studied as one of the new FBR fuel recycling systems. ln this study, we made an effort to clarify the mechanisms of vibro-packing of the electrically obtained granules, which influence on the effective parameters of vibro-packing density and fuel particles size distribution in the fuel cladding in case of non-sphere particles of the granules. As a result of the study, smear density of 75% and almost uniform distribution of U0 particles have been taken in the experiment, and much knowledge for the improvement of the vibro-packing quality has been found. And the possibility of the smear density over 80% and the uniform distribution of U0 particles has been suggested in this study.
Taguchi, Tomitsugu; Igawa, Naoki; Yamada, Reiji; Futakawa, Masatoshi; Jitsukawa, Shiro
Proceedings of 24th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures A, 21(3), p.453 - 458, 2000/00
no abstracts in English
; ; ; ; Kamide, Hideki
JNC TN9400 2000-025, 78 Pages, 1999/11
JNC-TN9400-2000-025.pdf:2.24MB
Local blockage issue in a fuel subassembly is one of initiation of local fault in a fast reactor core. ln existing studies, it is shown that blockage in a wire-spacer type pin bundle will consist of small particles coming through the bundle and will be porous. ln order to evaluate the integrity of fuel pins covered by the porous blockage, we have to predict thermohydraulics in the blockage and also in the pin bundle. ln this study sodium experiments were carried out using a 37-pin bundle test section with a porous blockage. The fueI pins are modeled by electric heater pins of 8.5 mm in diameter (full scale). The blockage is formed by stainless steel spheres of 0.3 mm in diameter. The blockage is set in the two rows of subchannels along one side of hexagonal wrapper tube. The length of blockage in axial direction is 35 mm and corresponds to 1/6th of wire wrapping pitch. The experimental parameters were power of the heater pins. The heater power was varied from 14% to 43% of the maximum linear heat rate of a real reactor (
420W/cm). The flow rate in the subassembly was set at 430 l/min corresponding to 93% of the Reynolds number in a fuel subassembly of real reactor under full power condition. The experimental results showed that the highest temperature was measured on the pin surface covered by the blockage and faced to the subchannel which was surrounded by the blockage. The height of peak temperature point was nearly top of the blockage. lt means that the temperature field in the blockage is influenced by flow filed in the blockage significantly. The non-dimensional temperature profile in the blockage and in the pin bundle is independent on heater power.
; Kano, Shigeki; ; Tachi, Yoshiaki; Hirakawa, Yasushi; Yoshida, Eiichi
PNC TN9410 98-021, 68 Pages, 1998/02
Engineering ceramics have excellent properties such as high strength, high hardness and high heat resistance compared with metallic matelials. To apply the ceramic in fast reactor environment, it is necessary to evaluate the sodium compatibility and the influence of sodium on the mechanical properties of ceramics. In this study, the influence of high temperature sodium on the mechanical properties of sintered ceramics of conventional and high purity AlO, SiC, SiAlON, AlN and unidirectional solidified ceramics of AlO/YAG eutectic composite were investigated by means of flexure tests. Test specimens were exposed in liquid sodium at 823K and 923K for 3.6Ms. There were no changes in the flexural strength of the conventional and high purity AlO, AlN and AlO/YAG eutectic composite after the sodium exposure at 823K. On the contrary, the decrease in the flexural strength was observed in SiC and SiAlON. After the sodium exposure at 923K, there were also no changes in the flexural strength of AlN and AlO/YAG eutectic composite. In the conventional and high purity AlO and SiC, the flexural strength decreased and signs of grain boundary corrosion were detected by surface observation. The flexural strength of SiAlON after the sodium exposure at 923K increased instead of severe corrosion. In the specimens those showed no changes in the flexural strength, further exposure in sodium is needed to verify whether the mechanical properties degrade or not. For SiAlON, it is necessary to clarify the reason for the increased strength after the sodium exposure at 923K.
Tachi, Yoshiaki; Hirakawa, Yasushi; Kano, Shigeki; Yoshida, Eiichi
PNC TN9410 98-054, 57 Pages, 1998/01
It has been progressed as the Frontier Materials Research to research and develop ceramics to apply for several components of fast breeder reactor using liquid sodium as coolant instead of metallic materials. Grain boundary of ceramics has peculiar properties compared with matrix because most of ceramics are produced by hardening and firing their raw powders. Some previous researchers indicated that ceramics were mainly corroded at grain boundaries by liquid sodium, and ceramics could not be used under corrosive environment. Thus, it is the most important for the usage of ceramics in liquid sodium to improve corrosion resistance of grain boundaries. In order to develop the advanced ceramics having good sodium corrosion resistance among fine ceramics, which have recently been progressed in quality and characteristics remarkably, sodium corrosion behaviors of typical sintering additives such as MgO, YO and AIN etc. have been examined and evaluated. As a result, the followings have been clarified and some useful knowledge about developing advanced ceramics having good corrosion resistance against liquid sodium has been obtained. (1)Sodium corrosion behavior of MgO depended on Si content. Samples containing large amount of Si were corroded severely by liquid sodium, whereas others with low Si contents showed good corrosion resistance. (2)Both YO and AIN, which contained little Si, showed good sodium corrosion resistance. (3)MgO, YO and AIN ale thought to be corroded by liquid sodium, if they contain some SiO. Therefore, in order to improve sodium corrosion resistance, it is very important for these ceramics to prevent the contamination of matrix with SiO through purity contlol of their raw powders.
O sintered pelletsTanifuji, Takaaki; Yamaki, Daiju; Noda, Kenji
Fusion Engineering and Design, 39-40, p.723 - 729, 1998/00
no abstracts in English
