Modification of vacuum plasma sprayed tungsten coating on reduced activation ferritic/martensitic steels by friction stir processing

Tanigawa, Hiroyasu; Ozawa, Kazumi; Morisada, Yoshiaki*; Noh, S.*; Fujii, Hidetoshi*

Fusion Engineering and Design, 98-99, p.2080 - 2084, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.04.059

The vacuum plasma spray (VPS) technique has been investigated as the most practical method to form Tungsten (W) layer as a plasma facing material in fusion devices. The issues are the thermal conductivity and the strength of VPS-W, i.e., the thermal conductivity of VPS-W were significantly lower than that of the bulk W, and the hardness of VPS-W is much less than that of the bulk W. These are mainly caused by the porous structure of VPS-W. In order to solve these issues, friction stir processing (FPS) was applied on VPS-W in this study. It was suggested that FSP can contribute to significant improvement both in mechanical and thermal properties of VPS-W coating.

Stress envelope of silicon carbide composites at elevated temperatures

Nozawa, Takashi; Kim, S.*; Ozawa, Kazumi; Tanigawa, Hiroyasu

Fusion Engineering and Design, 89(7-8), p.1723 - 1727, 2014/10

https://doi.org/10.1016/j.fusengdes.2013.12.032

A SiC/SiC composite is a promising candidate material for the advanced fusion DEMO blanket. For the design of the DEMO, the stability of high-temperature strength of SiC/SiC composites needs to be identified. Additionally, strength anisotropy needs to be clarified because of its unique fabric architecture. This study therefore aims to evaluate mechanical properties by various modes at elevated temperatures, eventually providing a stress envelope for the design. A P/W Tyranno-SA3 fiber reinforced CVI SiC matrix composite with multilayered SiC/PyC interface was evaluated in this study. Tensile and compressive tests were conducted by the SSTT specifically arranged for the high-temperature use. In-plane shear properties were contrarily estimated by the off-axial tensile method assuming that the mixed mode failure criterion is valid for composites. All tests were performed in vacuum. The preliminary test results indicate no degradation of both proportional limit stress (PLS) and the ultimate tensile strength at temperatures below 1000C. Similarly, no significant degradation of high-temperature compressive and in-plane shear properties were identified, finally providing the stress envelope at elevated temperatures for the design.

Characterization of failure behavior of silicon carbide composites by acoustic emission

Nozawa, Takashi; Ozawa, Kazumi; Tanigawa, Hiroyasu

Ceramic Materials for Energy Applications II, p.95 - 110, 2012/11

https://doi.org/10.1002/9781118217535.ch7

This study aims to identify failure behavior of SiC/SiC composites by varied test modes. For this purpose, acoustic emission (AE) was applied to detect composites' failure. Tensile and compressive tests were conducted for a plain-weave (P/W) chemical vapor infiltration (CVI) composite. Various loading angles were applied to discuss an anisotropic issue. AE results distinguished damage accumulation processes in axial and off-axial loading cases. Specifically, test results indicated a clear difference of damage density between tensile and compressive tests. This study also classified the characteristic failure modes by separately discussing localized variations of power within a time series by wavelet analysis.

Plan and reports of coupled irradiation (JRR-3 and JOYO of research reactors) and hot facilities work (WASTEF, JMTR-HL, MMF and FMF); R&D project on irradiation damage management technology for structural materials of long-life nuclear plant

Matsui, Yoshinori; Takahashi, Hiroyuki; Yamamoto, Masaya; Nakata, Masahito; Yoshitake, Tsunemitsu; Abe, Kazuyuki; Yoshikawa, Katsunori; Iwamatsu, Shigemi; Ishikawa, Kazuyoshi; Kikuchi, Taiji; et al.

JAEA-Technology 2009-072, 144 Pages, 2010/03

JAEA-Technology-2009-072.pdf:45.01MB

"R&D Project on Irradiation Damage Management Technology for Structural Materials of Long-life Nuclear Plant" was carried out from FY2006 in a fund of a trust enterprise of the Ministry of Education, Culture, Sports, Science and Technology. The coupled irradiations or single irradiation by JOYO fast reactor and JRR-3 thermal reactor were performed for about two years. The irradiation specimens are very important materials to establish of "Evaluation of Irradiation Damage Indicator" in this research. For the acquisition of the examination specimens irradiated by the JOYO and JRR-3, we summarized about the overall plan, the work process and the results for the study to utilize these reactors and some facilities of hot laboratory (WASTEF, JMTR-HL, MMF and FMF) of the Oarai Research-and-Development Center and the Nuclear Science Research Institute in the Japan Atomic Energy Agency.

Interfacial property evaluation of SiC/SiC model composites

Ozawa, Kazumi; Nozawa, Takashi; Tanigawa, Hiroyasu; Kato, Yutai*; Snead, L. L.*

no journal, , 

An advanced SiC/SiC composite is a candidate material for fusion DEMO reactor. Four types of model unidirectional SiC/SiC composites (minicomposites) with variations in fiber (Hi-Nicalon Type-S (HNLS), Tyranno-SA3, Sylramic and Sylramic-iBN) by chemical vapor infiltration method were evaluated for tensile and fiber/matrix interfacial properties. The ultimate tensile strength (UTS) increased with the interfacial sliding stress () obtained by the hysteresis loop analysis for Tyranno-SA3, Sylramic and Sylramic-iBN. However, this was not the case for the HNLS composite. The composite achieved high UTS due to very low , arising from the larger residual radial tensile stress and smooth fiber surface. In contrast, the fracture behavior of the other composites may have been strongly affected by the clamping stress produced by the relatively rough fiber surfaces.

Strength and interfacial properties of single fiber-tow CVI SiC/SiC minicomposites

Ozawa, Kazumi; Kato, Yutai*; Nozawa, Takashi; Tanigawa, Hiroyasu; Snead, L. L.*

no journal, , 

An advanced SiC/SiC composite is very attractive as an advanced blanket material for fusion DEMO reactor. In this study, tensile and fiber/matrix interfacial properties of unirradiated SiC/SiC minicomposites were evaluated in order to examine the effects of difference of fiber and interphase thickness. The experiments revealed that fiber surface roughness directly correlates with interfacial sliding stress and that the relationship can affects ultimate tensile stress. Additionally the dependence of interphase thickness on tensile and interfacial strength was also confirmed.

Tensile and interfacial strength evaluation of SiC/SiC model composites

Ozawa, Kazumi; Nozawa, Takashi; Tanigawa, Hiroyasu

no journal, , 

Tensile and interfacial properties of unidirectional SiC/SiC model composites reinforced with Hi-Nicalon Type-S fibers with innermost pyrolytic carbon (PyC) layer thickness of 240 and 1150 nm (TypeS-240 and TypeS-1150, respectively) were evaluated by unloading/reloading cyclic tensile tests and single fiber push-out tests. Effective fiber bundle strength in the TypeS-240 and -1150 composites were 79-104% and 70-85%, compared with the original fiber bundle strength. According to the analytic results using hysteresis loops of tensile curves, interfacial sliding stress of the TypeS-1150 estimated to be about 0.7 times as large as the TypeS-240. This tendency was also confirmed by the single fiber push-out tests. These composites showed quasi-ductility, but it is considered that the composite with the thicker interphase could not achieve its fiber bundle strength, probably due to the lower interfacial sliding stress.

Tensile and interfacial properties of SiC/SiC minicomposites

Ozawa, Kazumi; Nozawa, Takashi; Tanigawa, Hiroyasu

no journal, , 

A silicon carbide (SiC) matrix composite is a promising candidate for nuclear fusion energy applications. In order to design a damage tolerant composite, fiber/matrix interfacial properties with and without irradiation effects should be thoroughly and systematically understood. For this purpose an approach using model composites is considered to be suitable. This study examines the effects of different fibers and interphases on tensile and interfacial properties of non-irradiated SiC/SiC minicomposites which have high crystalline and near stoichiometric SiC fibers. As a result of the tensile unloading-reloading cyclic tests, following analysis of the hysteresis loops, and the single fiber push-out tests, (1) fiber surface roughness can significantly affect interfacial sliding stress and hence each tensile characteristic such as tensile strength/strain and hysteresis loop width, and (2) interphase thickness would also influence the interfacial and tensile properties.

Effects of transmuted hydrogen on microstructure of SiC by nano-infiltration transient eutectic process after triple ion beam irradiation

Ozawa, Kazumi; Koyanagi, Takaaki*; Taguchi, Tomitsugu; Nozawa, Takashi; Tanigawa, Hiroyasu; Kondo, Sosuke*; Hinoki, Tatsuya*

no journal, , 

no abstracts in English

Tensile and interfacial properties of unidirectional advanced SiC/SiC minicomposites

Ozawa, Kazumi; Nozawa, Takashi; Tanigawa, Hiroyasu; Kato, Yutai*; Snead, L. L.*

no journal, , 

A silicon carbide (SiC) matrix composite is a promising candidate for nuclear fusion energy applications. Unloading-reloading cyclic tensile tests were conducted to estimate interfacial properties for unidirectional SiC/SiC minicomposites reinforced by Hi-Nicalon Type-S (HNLS) or Tyranno-SA3 SiC fibers via CVI process were conducted. The interfacial properties were also evaluated by fiber push-out test. According to these results, it is implied that both fiber surface roughness and interfacial layter thickness can impact the tensile and interfacial properties.