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Journal Articles

Optimization of mechanical properties in aluminum alloys $$via$$ hydrogen partitioning control

Toda, Hiroyuki*; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Su, H.*; Fujiwara, Hiro*; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; et al.

Tetsu To Hagane, 105(2), p.240 - 253, 2019/02

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Corrosion resistance of structural materials in high-temperature aqueous sulfuric acids in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Ioka, Ikuo; Onuki, Kaoru; Yamaguchi, Akihisa*

International Journal of Hydrogen Energy, 38(16), p.6577 - 6585, 2013/05

 Times Cited Count:18 Percentile:47.36(Chemistry, Physical)

Very harsh environments exist in the iodine-sulfur process for hydrogen production. Structural materials for sulfuric acid vaporizers and concentrators are exposed to high-temperature corrosive environments. Immersion tests were carried out to evaluate the corrosion resistance of ceramics and to evaluate corrosion-resistant metals exposed to environments of aqueous sulfuric acids at temperatures of 320, 380, and 460$$^{circ}$$C, and pressure of 2 MPa. The aqueous sulfuric acid concentrations for the temperatures were 75, 85, and 95 wt%, respectively. Ceramic specimens of silicon carbides (SiC), silicon impregnated silicon carbides (Si-SiC), and silicon nitrides (Si$$_{3}$$N$$_{4}$$) showed excellent corrosion resistance from weight loss measurements after exposure to 75, 85, and 95 wt% sulfuric acid. High-silicon irons with silicon content of 20 wt% showed a fair measure of corrosion resistance. However, evidence of crack formation was detected via microscopy. Silicon enriched steels severely suffered from uniform corrosion with a corrosion rate in 95 wt% sulfuric acid of approximately 1 gm$$^{-2}$$h$$^{-2}$$. Among the tested materials, the ceramics SiC, Si-SiC, and Si$$_{3}$$N$$_{4}$$ were found to be suitable candidates for structural materials in direct contact with the considered environments.

Journal Articles

Adaptability of Metallic Structural Materials to gaseous HI decomposition environment in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Onuki, Kaoru; Yamaguchi, Akihisa*

Corrosion Engineering, 62(3), p.104 - 111, 2013/03

The iodine-sulfur thermochemical cycle for hydrogen production takes place in very harsh environments. Structural metallic materials for the hydrogen iodide decomposition are exposed in a high temperature halogen corrosion and hydrogen embrittlement environment. To evaluate adaptability of the materials, the corrosion rates and mechanical properties (the yield strength, the tensile strength, and the elongation) were measured. Prepared test specimens were exposed to ambient gas consisting of HI, I$$_2$$, H$$_2$$O, and H$$_2$$ (molar fraction of 1:1:6:0.16) at 450$$^{circ}$$C for 1000 h at atmospheric pressure. After the exposure, the corrosion rates were obtained by the weight loss of each specimen. Nickel-based alloys (Hastelloy C-276, MAT21, Inconel 625) exhibited appropriate corrosion resistance ($$<$$ 0.03 g m$$^{-2}$$ h$$^{-1}$$. In addition, no degradations of the mechanical properties for the MAT21 and the Inconel 625 were observed. The specimens of tantalum and titanium showed hydrogen embrittlement; the specimens of zirconium and niobium exhibited poor corrosion resistance. The specimens of molybdenum (Mo) exhibited good corrosion resistance; however, the strength degradation of Mo is cause for concern. As the results show, the nickel-based alloys are well suited for the structural materials within this environment from the viewpoint of the corrosion resistance. MAT21 among them is an outstanding material with an eye to its corrosion resistance and mechanical properties.

Journal Articles

Adaptability of metallic structural materials to gaseous HI decomposition environment in thermochemical water-splitting iodine-sulfur process

Kubo, Shinji; Futakawa, Masatoshi; Onuki, Kaoru; Yamaguchi, Akihisa*

Zairyo To Kankyo, 62(3), p.122 - 128, 2013/03

The iodine-sulfur thermochemical cycle for hydrogen production takes place in very harsh environments. Structural metallic materials for the hydrogen-iodide decomposition are exposed in the high-temperature halogen corrosion and the hydrogen embrittlement environment. To evaluate adaptability of the materials, corrosion rates and mechanical properties (the yield strength, the tensile strength, and the elongation) were measured. Prepared test specimens were exposed to ambient gas consisting of HI, I$$_{2}$$, H$$_{2}$$O and H$$_{2}$$ (molarfraction, 1:1:6:0.16) at 450$$^{circ}$$C for 1000 hours at the atmospheric pressure. After the exposure, the corrosion rates were obtained by the weight loss of each specimen. Nickel-based alloys (Hastelly C-276, MAT21, Inconel 625) exhibited appropriate corrosion resistance ($$<$$ 0.03 g m$$^{-2}$$ h$$^{-1}$$). In addition, no degradations of the mechanical properties for the MAT21 and the Inconel 625 were observed. The specimens of tantalum and titanium showed the hydrogen embrittlement; the specimens of zirconium and niobium exhibited poor corrosion resistance. The specimens of molybdenum (Mo) exhibited good corrosion resistance, however strength degradation of Mo is causing concern. As the results, the nickel-based alloys are well suited for the structural materials within this environment from the viewpoint of the corrosion resistance. MAT21 among them is the outstanding material with an eye to its corrosion resistance and mechanical properties.

Journal Articles

Growth temperature dependence of strain relaxation during InGaAs/GaAs(0 0 1) heteroepitaxy

Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Takahashi, Masamitsu; Fujikawa, Seiji; Kamiya, Itaru*; Oshita, Yoshio*; Yamaguchi, Masafumi*

Journal of Crystal Growth, 323(1), p.13 - 16, 2011/05

 Times Cited Count:18 Percentile:82.45(Crystallography)

Growth temperature dependence of strain relaxation during In$$_{0.12}]$$Ga$$_{0.88}$$As/GaAs(001) molecular beam epitaxy was studied by in situ X-ray reciprocal space mapping. Evolution of the residual strain and crystal quality for the InGaAs film was obtained as a function of film thickness at growth temperatures of 420, 445 and 477 $$^{circ}$$C. In the early stages of strain relaxation, it was found that evolution of the residual strain and crystal quality was dependent on the growth temperature. In order to discuss this observation quantitatively, the strain relaxation model was proposed based on the Dodson-Tsao kinetic model, and its validity was demonstrated by good agreement with the experimental residual strain. Additionally, rate coefficients reflecting dislocation motions during strain relaxation were obtained as a function of growth temperature and strain relaxation was discussed in terms of the thermally active dislocation motion.

Journal Articles

Real-time observation of anisotropic strain relaxation by three-dimensional reciprocal space mapping during InGaAs/GaAs(001) growth

Suzuki, Hidetoshi*; Sasaki, Takuo*; Sai, Akihisa*; Oshita, Yoshio*; Kamiya, Itaru*; Yamaguchi, Masafumi*; Takahashi, Masamitsu; Fujikawa, Seiji

Applied Physics Letters, 97(4), p.041906_1 - 041906_3, 2010/07

 Times Cited Count:31 Percentile:76.12(Physics, Applied)

Journal Articles

In situ study of strain relaxation mechanisms during lattice-mismatched InGaAs/GaAs growth by X-ray reciprocal space mapping

Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Takahashi, Masamitsu; Fujikawa, Seiji; Oshita, Yoshio*; Yamaguchi, Masafumi*

Materials Research Society Symposium Proceedings, Vol.1268, 6 Pages, 2010/05

 Times Cited Count:0 Percentile:0.01

Journal Articles

${it In situ}$ real-time X-Ray reciprocal space mapping during InGaAs/GaAs growth for understanding strain relaxation mechanisms

Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Lee, J.-H.*; Takahashi, Masamitsu; Fujikawa, Seiji; Arafune, Koji*; Kamiya, Itaru*; Oshita, Yoshio*; Yamaguchi, Masafumi*

Applied Physics Express, 2, p.085501_1 - 085501_3, 2009/07

 Times Cited Count:34 Percentile:77.64(Physics, Applied)

Journal Articles

Corrosion resistance of materials of construction for high temperature sulfuric acid service in thermochemical IS process, Alloy 800, Alloy 600, SUSXM15J1 and SiC

Tanaka, Nobuyuki; Onuki, Kaoru; Shimizu, Saburo; Yamaguchi, Akihisa*

Zairyo To Kankyo, 55(7), p.320 - 324, 2006/07

Exposure tests of candidate materials were carried out up to 1000 hr in the sulfuric acid environments of thermochemical hydrogen production IS process, focusing on the corrosion of welded portion and of crevice area. In the gas phase sulfuric acid decomposition condition at 850$$^{circ}$$C, welded samples of Alloy 800 and of Alloy 600 showed the same good corrosion resistance as the bare materials. Also, in the boiling condition of 95wt% sulfuric acid solution, negligible corrosion was observed in crevice corrosion test sample of SiC.

Journal Articles

Corrosion rate evaluations of structural materials for a iodine-sulfur thermochemical water-splitting cycle

Kubo, Shinji; Futakawa, Masatoshi; Tanaka, Nobuyuki; Iwatsuki, Jin; Yamaguchi, Akihisa*; Tsukada, Ryuji*; Onuki, Kaoru

Proceedings of 2006 International Congress on Advances in Nuclear Power Plants (ICAPP '06) (CD-ROM), 6 Pages, 2006/06

no abstracts in English

Journal Articles

Mechanical property evaluation of surface layer corroded in thermochemical-hydrogen-production process condition

Futakawa, Masatoshi; Kubo, Shinji; Wakui, Takashi*; Onuki, Kaoru; Shimizu, Saburo; Yamaguchi, Akihisa*

Jikken Rikigaku, 3(2), p.109 - 114, 2003/06

Micro-indentation technique was applied to evaluate the mechanical properties of corroded surface layers of Ni-alloy, 316SS, Ti and Ta, which were exposed into the corrosive gaseous environment consisting of HI+I$$_{2}$$+H$$_{2}$$O+H$$_{2}$$. The corrosion condition was chosen so as to simulate one of the environments in the thermochemical hydrogen production, IS process, where the degradation due to the corrosion attack by HI and the hydrogen embrittlement is a key issue from the viewpoint of material integrity. The micro-indentation tests using a spherical indenter and the inverse analysis with Kalman filter were performed to quantitatively estimate material constants of corroded surface layer. Ni-alloy exhibited good corrosion resistance and Ta was remarkably influenced by the hydrogen embrittlement.

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