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Journal Articles

Effect of heat treatment on TEM microstructures of Zirconium carbide coating layer in fuel particle for advanced high temperature gas cooled reactor

Aihara, Jun; Ueta, Shohei; Yasuda, Atsushi*; Takeuchi, Hitoshi*; Mozumi, Yasuhiro*; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Materials Transactions, 50(11), p.2631 - 2636, 2009/11

 Times Cited Count:8 Percentile:49.11(Materials Science, Multidisciplinary)

The ZrC coating layer has been fabricated using the bromide process at JAEA. The coated particles with IPyC layers reported in a previous study were annealed at around 1800$$^{circ}$$C for 1h, under which compact sintering will be done in a practical process, in order to study effects of the heat treatment (annealing) on their microstructure evolution. Then the microstructures of the ZrC layers in the cases (batches) of C/Zr = 1.11 and 1.35 were characterized by means of TEM and STEM. Certain changes in the shape and size of voids or free carbons region caused by the heat treatment were found in the cases of both batches. After the heat treatment, the voids or free carbons region have shown a clod like feature with diameters of 50 to 100 nm. The grain growth of ZrC was also observed in both cases: In the ZrC layer with C/Zr = 1.11, the fibrous carbons grew as of to stand from the PyC to ZrC layers on some places in the IPyC/ZrC boundary.

Journal Articles

TEM/STEM observation of ZrC coating layer for advanced high-temperature gas-cooled reactor fuel, Part II

Aihara, Jun; Ueta, Shohei; Yasuda, Atsushi; Ishibashi, Hideharu; Mozumi, Yasuhiro; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Journal of the American Ceramic Society, 92(1), p.197 - 203, 2009/01

 Times Cited Count:7 Percentile:44.95(Materials Science, Ceramics)

The ZrC coating layer was fabricated with bromide process at JAEA. In a later stage of the project, we have successfully kept nominal deposition temperature almost constant. Microstructures of the ZrC layers, of which nominal deposition temperatures were able to measure, were characterized by means of TEM and STEM and the results were compared and discussed with those obtained for different batches including those reported in a previous study. The ZrC grains were oriented in the ZrC layers deposited at about 1630 K. This feature was rather different from that reported in the previous study. The formation of fairly different PyC structures was found on the PyC/ZrC boundary as well as around the pores existing near the boundary. Fibrous carbons were observed on the PyC/ZrC boundary produced in a batch deposited at a higher temperature (nominal temperature was 1769 K); no such fibrous carbons were found in a batch deposited at a lower temperature (nominal temperature was 1632 K).

Journal Articles

TEM/STEM observation of ZrC-coating layer for advanced high-temperature gas-cooled reactor fuel

Aihara, Jun; Ueta, Shohei; Yasuda, Atsushi; Ishibashi, Hideharu; Takayama, Tomoo; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Journal of the American Ceramic Society, 90(12), p.3968 - 3972, 2007/12

Japan Atomic Energy Agency (JAEA) has started to study and develop ZrC coated fuel particles for advanced high temperature gas cooled reactors. This paper mainly focuses on the microstructures of the ZrC and isotropic dense pyrolytic carbon (PyC) coating layer produced in the early stage of the project. The structure of free carbon region in the ZrC coating layer appears to be such that c-plane was along with the ZrC grain boundary. It appears that the existence of the free carbon phase, especially with such structure, deteriorates the fission product (FP) retention performance in addition to the mechanical strength of ZrC. The PyC coating layer appears to be a medium-range ordered amorphous structure.

Journal Articles

Calculation of the pressure vessel failure fraction of fuel particle of gas turbine high temperature reactor 300C

Aihara, Jun; Ueta, Shohei; Mozumi, Yasuhiro; Sato, Hiroyuki; Motohashi, Yoshinobu*; Sawa, Kazuhiro

Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.416 - 422, 2007/09

In high temperature gas-cooled reactors (HTGRs), coated particles are used as fuels. For upgrading HTGR technologies, present SiC coating layer which is used as the 3rd layer could be replaced with ZrC coating layer which have much higher temperature stability in addition to higher resistance to chemical attack by fission product palladium than the SiC coating layer. The ZrC layer could deform plastically at high temperatures. Therefore, the Japan Atomic Energy Agency modified an existing pressure vessel failure fraction calculation code to treat the plastic deformation of the 3rd layer in order to predict failure fraction of ZrC coated particle under irradiation. Finite element method is employed to calculate the stress in each coating layer. The pressure vessel failure fraction of the coated fuel particles under normal operating condition of GTHTR300C is calculated by the modified code. The failure fraction is evaluated as low as 3.5$$times$$10$$^{-6}$$.

Journal Articles

Crystal nucleation behavior caused by annealing of SiC irradiated with Ne at liquid nitrogen temperature or at 573K

Aihara, Jun; Hojo, Kiichi; Furuno, Shigemi*; Hojo, Tomohiro; Sawa, Kazuhiro; Yamamoto, Hiroyuki; Motohashi, Yoshinobu*

Materials Transactions, 48(7), p.1896 - 1900, 2007/07

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

Silicon carbide(SiC) TEM specimens were annealed, in-situ, at 1273K for 30 minutes after amorphization with 30keV Ne$$^{+}$$ irradiation to the fluence of 1.9 or 2.3$$times$$10$$^{20}$$Ne$$^{+}$$/m$$^{2}$$ at 573K or about 98K. The crystal nucleation and bubble coalescence accompanied by recrystallization were observed in both specimens with the annealing after the irradiations. 2.3$$times$$10$$^{20}$$Ne$$^{+}$$/m$$^{2}$$ irradiations in both specimens. The Debye-Sherrer rings of the nucleated crystals well fitted the net pattern of the matrix, even though no ring corresponding to (200) of $$beta$$-SiC appeared. Dependence of the crystal nucleation behavior on irradiation temperature was not observed within the present experimental range.

Journal Articles

Fatigue strength degradation by pitting damage

Naoe, Takashi; Futakawa, Masatoshi; Oi, Toshiyuki; Wakui, Takashi; Motohashi, Yoshinobu*

Zairyo, 55(10), p.944 - 950, 2006/10

Mercury target will be installed at the material and life facility in J-PARC. Pressure waves will be generated in mercury by thermally shocked heat deposition when the high intense proton beams bombard the mercury target. Cavitation will be induced through the pressure wave propagation in the mercury and eroded the vessel inner surface contacting with the mercury. The eroded vessel wall is damaged by cyclic fatigue because pulsed proton beams strike the target repeatedly. It is, therefore, important to investigate the fatigue strength of the eroded vessel wall. In order to precisely investigate the effects of damages, at the first, the pitting damage by erosion was evaluated against the number of pulses, and then the fatigue test was carried out using the specimen with a certain pitting damage. As a result, the fitigue limit with pitting damage is degraded to less than half of that without pitting damage, after 2500 hrs operation at 1MW.

Journal Articles

A New strength prediction method for 2D-C/C composite components

Hanawa, Satoshi; Ishihara, Masahiro; Shibata, Taiju; Sawa, Kazuhiro; Motohashi, Yoshinobu*

Zairyo, 55(9), p.868 - 873, 2006/09

no abstracts in English

Journal Articles

Microstructural change with annealing of SiC irradiated with Ne at 573-673 K

Aihara, Jun; Hojo, Kiichi; Furuno, Shigemi*; Shimura, Kenichiro; Hojo, Tomohiro*; Sawa, Kazuhiro; Yamamoto, Hiroyuki; Motohashi, Yoshinobu*

Nuclear Instruments and Methods in Physics Research B, 242(1-2), p.441 - 444, 2006/01

 Times Cited Count:1 Percentile:13.43(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Analytical study on biaxial strength of structural ceramics under tension-compression condition

Hanawa, Satoshi; Ishihara, Masahiro; Motohashi, Yoshinobu*

Key Engineering Materials, 297-300, p.40 - 46, 2005/11

no abstracts in English

Journal Articles

Evaluation of mechanical properties and microstructure in ion-irradiated surface layer

Naoe, Takashi*; Futakawa, Masatoshi; Naito, Akira*; Kogawa, Hiroyuki; Ikeda, Yujiro; Motohashi, Yoshinobu*

JSME International Journal, Series A, 48(4), p.280 - 285, 2005/10

Target vessel materials used in spallation neutron source will be exposed to proton and neutron irradiation and mercury immersion environments. In order to evaluate the surface degradation of the vessel candidate materials due to such environment, the triple-ion beam irradiation taking the spallation reaction into account and mercury immersion tests were carried out. Mechanical properties of the gradient surface layer ware evaluated by the inverse analysis with multi-layer model that considers distribution of surface characteristic was applied to the load and depth curves measured by using the instrumented indentation machine. Transmission electron microscopic observations ware performed to evaluate the changes of microstructure in irradiated surface layer using focused ion-beam cut micro-specimen. It was confirmed that the ductility loss is enhanced by the irradiation and mercury immersion, and simulated stress and strain curves of the ion-irradiated surface layer ware adequately in good agreement with the curves of experimental equivalent neutron-irradiated material.

Journal Articles

Study on brittle fracture model for multiaxial tensile stress

Hanawa, Satoshi; Ishihara, Masahiro; Motohashi, Yoshinobu*

Zairyo, 54(2), p.201 - 206, 2005/02

no abstracts in English

Journal Articles

Ion beam surface modification of Y-TZP and effects of subsequent annealing

Motohashi, Yoshinobu*; Shibata, Taiju; Harjo, S.*; Sakuma, Takaaki*; Ishihara, Masahiro; Baba, Shinichi; Sawa, Kazuhiro

Proceedings of 14th International Federation for Heat Treatment and Surface Engineering Congress Transactions of Materials and Heat Treatment Vol.25 No.5, p.1032 - 1036, 2004/10

no abstracts in English

Journal Articles

Probabilistic strength evaluation on superplastic 3Y-TZP ceramics

Baba, Shinichi; Shibata, Taiju; Yamaji, Masatoshi*; Sumita, Junya; Ishihara, Masahiro; Motohashi, Yoshinobu*; Sawa, Kazuhiro

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2004) Koen Rombunshu (No.040-3), p.61 - 62, 2004/09

no abstracts in English

Journal Articles

Neutron irradiation effect on microstructure of superplastic 3Y-TZP ceramics

Shibata, Taiju; Motohashi, Yoshinobu*; Ishihara, Masahiro; Baba, Shinichi; Ito, Tsutomu*; Sawa, Kazuhiro

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2004) Koen Rombunshu (No.040-3), p.63 - 64, 2004/09

no abstracts in English

Journal Articles

High temperature bending characteristics of Al$$_{2}$$O$$_{3}$$ joints bonded using superplastic ceramics as interlayer

Sato, Takashi*; Motohashi, Yoshinobu*; Sakuma, Takaaki*; Waseda, Kazuyoshi*; Shibata, Taiju; Ishihara, Masahiro; Sawa, Kazuhiro

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2004) Koen Rombunshu (No.040-3), p.55 - 56, 2004/09

no abstracts in English

Journal Articles

Variations in mechanical properties of zirconia-base ceramics due to superplastic deformations

Kikuchi, Makoto*; Motohashi, Yoshinobu*; Ito, Tsutomu*; Sakuma, Takaaki*; Shibata, Taiju; Baba, Shinichi; Ishihara, Masahiro; Sawa, Kazuhiro; Hojo, Tomohiro*; Tsuji, Nobumasa*

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2004) Koen Rombunshu (No.040-3), p.57 - 58, 2004/09

no abstracts in English

Journal Articles

Effects of neutron irradiation on some superplastic characteristics of tetragonal zirconia polycrystals containing 3 mol% yttria

Shibata, Taiju; Ishihara, Masahiro; Motohashi, Yoshinobu*; Ito, Tsutomu*; Baba, Shinichi; Kikuchi, Makoto*

Materials Transactions, 45(8), p.2580 - 2583, 2004/08

 Times Cited Count:3 Percentile:28.51(Materials Science, Multidisciplinary)

Fast neutrons (energy $$>$$ 1.6$$times$$10$$^{23}$$ J) were irradiated to tetragonal zirconia polycrystals containing 3 mol% yttria (3Y-TZP) at the fluence levels of 2.5$$times$$10$$^{24}$$ (Light irradiation) and 4.3$$times$$10$$^{24}$$ (Heavy irradiation) m$$^{-2}$$. The irradiation caused no significant swelling in the 3Y-TZP specimens. After the neutron irradiation, superplastic characteristics were examined by tensile tests at a temperature range from 1623 to 1773 K with initial strain rates ranging from 5.0$$times$$10$$^{-4}$$ to 1.67$$times$$10$$^{-2}$$s$$^{-1}$$. It was found that the elongation to fracture of the irradiated specimens was quite small in comparison with the unirradiated ones. The apparent activation energy for the superplastic flow of the irradiated 3Y-TZP was fairly high, i.e., 781 and 693 kJ・mol$$^{-1}$$ for Light and Heavy irradiations, respectively. Atomic displacement damages and defects in the 3Y-TZP caused by the irradiation were thought to be main causes of these property changes.

Journal Articles

Radiation damage effects in superplastic 3Y-TZP irradiated with Zr ions

Motohashi, Yoshinobu*; Kobayashi, Tomokazu*; Harjo, S.*; Sakuma, Takaaki*; Shibata, Taiju; Ishihara, Masahiro; Baba, Shinichi; Hoshiya, Taiji

Nuclear Instruments and Methods in Physics Research B, 206, p.144 - 147, 2003/05

 Times Cited Count:4 Percentile:34.53(Instruments & Instrumentation)

The 3mol% yttria containing tetragonal zirconia polycrystals(3Y-TZP) were irradiated using 130MeV Zr$$^{11+}$$ ions in the TANDEM accelerator facility at Tokai Research Establishment, JAERI. Irradiation was performed with the fluence of 3.5$$times$$10$$^{16}$$ and 2.1$$times$$10$$^{17}$$ ions/m$$^{2}$$. Residual stress and changes in mechanical properties caused by the ion irradiation and the effects of the subsequent annealing are studied. The occurrence of compressive residual stresses and increases in hardness and fracture toughness were found at the surface regions of as-irradiated specimens. It was found from the subsequent annealing that these quantities decreased gradually with raising the annealing temperature and returned to that of un-irradiated state at around 1173K. A most probable cause of the increases in the hardness and fracture toughness after the irradiation may, therefore, be the residual compressive stresses left in the irradiated surface region.

Journal Articles

Superplastic deformation characteristics of 3Y-TZP after Zr ion irradiation

Shibata, Taiju; Ishihara, Masahiro; Motohashi, Yoshinobu*; Baba, Shinichi; Hoshiya, Taiji; Kobayashi, Tomokazu*; Harjo, S.*; Sakuma, Takaaki*

Nuclear Instruments and Methods in Physics Research B, 206, p.139 - 143, 2003/05

 Times Cited Count:4 Percentile:34.53(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Thermal conductivity of superplastically deformed 3Y-TZP

Wan, C.*; Motohashi, Yoshinobu*; Shibata, Taiju; Baba, Shinichi; Ishihara, Masahiro; Hoshiya, Taiji

Materials Transactions, 43(10), p.2473 - 2479, 2002/10

 Times Cited Count:11 Percentile:59.43(Materials Science, Multidisciplinary)

no abstracts in English

39 (Records 1-20 displayed on this page)