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Kiyoshi Aoki - One of the best experts on this subject based on the ideXlab platform.
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Formation of surface oxides and its effects on the Hydrogen Permeability of Nb40Ti30Ni30 alloy
International Journal of Hydrogen Energy, 2016Co-Authors: Kazuhiro Ishikawa, H. Habaguchi, N. Obata, Y. Kobori, N. Ohtsu, Kiyoshi AokiAbstract:Abstract The formation of oxides on the surface of Nb40Ti30Ni30 alloy by annealing in air at elevated temperatures and the effect of an intermediate oxide layer on the Hydrogen Permeability of a Pd/alloy composite were investigated. Oxides were formed when the Nb40Ti30Ni30 alloy was annealed in air for 2 h; Nb6O below 773 K, Nb6O + TiO2+Ti4Ni2O at 873 K and Nb6O + TiO2+Ti4Ni2O + Nb2O5 at 973 K. The Hydrogen Permeability of the Pd/oxide/Nb40Ti30Ni30 composite oxidized below 773 K was slightly higher than that of the oxide-free Pd/Nb40Ti30Ni30 composite after 100 h. XPS analysis revealed that penetration between Pd and alloy elements was suppressed by the oxide layer. In contrast, the composite oxidized at 873 K showed low Hydrogen Permeability that remained fairly constant for 100 h. The oxide layer contributes a barrier to the diffusion of Hydrogen and metallic atoms, which suggests that control of the structure and thickness of the oxide layer is important to achieve both high Hydrogen Permeability and low degradation.
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Microstructure and Hydrogen Permeability in Nb-TiFe alloys
Journal of Alloys and Compounds, 2013Co-Authors: Kazuhiro Ishikawa, Shogo Watanabe, Kiyoshi AokiAbstract:Abstract The relationship between the microstructure and Hydrogen Permeability of Nb–TiFe alloys is investigated. The fully eutectic alloy, which consisted of the bcc-(Nb, Ti) and B2-TiFe phases, is found in the Nb16Ti53Fe31 composition. The alloys formed between the Fe50Ti50 and Nb16Ti53Fe31 compositions, expressed as (Ti50Fe50)1−x(Nb16Ti53Fe31)x, consist of the eutectic structure, including the primary TiFe phase for x 1. The volume fraction of the primary phase is decreased (0 1) with increasing x. The alloys with 0.4
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Hydrogen Permeability and microstructure of rapidly quenched Nb–TiNi alloys
Journal of Alloys and Compounds, 2011Co-Authors: Kazuhiro Ishikawa, Yuta Seki, Koichi Kita, Minoru Nishida, Kiyoshi AokiAbstract:Abstract Effect of annealing on structure, microstructure and Hydrogen Permeability of rapidly quenched Nb 30 Ti 35 Ni 35 and Nb 40 Ti 30 Ni 30 alloy ribbons were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and the gas flow method. Crystalline (Nb, Ti) and TiNi phases coexisted with the amorphous phases in the as-quenched Nb 30 Ti 35 Ni 35 alloy, while only crystalline (Nb, Ti) and TiNi phases were formed in the as-quenched Nb 40 Ti 30 Ni 30 alloy. Both the as-quenched alloys were too brittle to measure their Hydrogen Permeability, but they became ductile by annealing above 1173 K and showed the microstructure consisting of the crystalline (Nb, Ti) phase embedded in the crystalline TiNi matrix. The volume fraction of the (Nb, Ti) phases in the Nb–TiNi alloys increased with increasing Nb content. Hydrogen Permeability at 673 K, i.e. Φ 673 K of the crystalline Nb 30 Ti 35 Ni 35 and Nb 40 Ti 30 Ni 30 alloys was 1.1 × 10 −8 and 1.9 × 10 −8 (molH 2 /m/s/Pa 0.5 ), respectively, which were comparable with that of Pd. The present work has clearly demonstrated that the rapid quenching technique and subsequent annealing process are useful and attractive method for the preparation of Hydrogen permeable Nb–TiNi alloy membrane.
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Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy
Materials Science Forum, 2010Co-Authors: Wei Liang Wang, Kazuhiro Ishikawa, Kiyoshi AokiAbstract:In general, Hydrogen PermeabilityΦ of the alloy membrane is expressed as the product of the Hydrogen diffusion coefficient D and the Hydrogen solution coefficient K. Therefore, to improve the Hydrogen Permeability efficiently, the values of K and D should be separately considered. In the present study, Hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the Hydrogen flow method and compared with those of palladium. The Hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of Hydrogen pressure and Hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the Hydrogen Permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.
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Effect of Ti/Ni Ratio and Annealing on Microstructure and Hydrogen Permeability of Nb-TiNi Alloy
MATERIALS TRANSACTIONS, 2008Co-Authors: Tetsuya Kato, Kazuhiro Ishikawa, Kiyoshi AokiAbstract:A series of Nb40Ti30þxNi30� x alloys are characterized in terms of microstructure, crystal structure, ductility, susceptibility to Hydrogen embrittlement, and Hydrogen Permeability as non-palladium-based Hydrogen permeation alloys. The maximum Hydrogen Permeability and ductility of the alloy is exhibited by the alloy with composition of x ¼ 2 (Nb40Ti32Ni28). The enhancement of Hydrogen Permeability correlates well with an increase in the volume fraction of the primary (Nb, Ti) phase. After cold rolling and annealing, the Hydrogen Permeability of the Nb40Ti34Ni26 (x ¼ 4) alloy becomes superior to that of the Nb40Ti30Ni30 (x ¼ 0) composition previously reported to be the best in the Nb40Ti30þxNi30� x series. The present results indicate that the Hydrogen Permeability of the Nb-TiNi alloy can be optimized by annealing and appropriately adjusting the Ti/Ni ratio for a given niobium content. [doi:10.2320/matertrans.MA200851]
Kazuhiro Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Permeability degradation of Pd-coated NbTiNi alloy caused by its interfacial diffusion
Applied Surface Science, 2016Co-Authors: Naofumi Ohtsu, Kazuhiro Ishikawa, Yoshihiro KoboriAbstract:Abstract Pd-coated Nb 40 Ti 30 Ni 30 (Nb⿿TiNi) is considered a promising material for Hydrogen-permeable membranes because of the low usage of Pd metal. This paper reports the degradation of Hydrogen Permeability occurring during the permeation experiment above 773 K. Surface analysis using X-ray photoelectron spectroscopy revealed that interdiffusion between the Pd coating and the constituent elements of Nb and Ti progressed during the permeation experiment. The diffused Ti was concentrated near the topmost surface and then formed TiO 2 , which resulted in a decrease in the Pd concentration at the topmost surface. However, the diffused Nb was observed to bind to Pd in the surface and formed a Pd⿿Nb alloy beneath the topmost surface. We concluded that these changes caused the decline of the Hydrogen Permeability at high-temperature conditions.
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Formation of surface oxides and its effects on the Hydrogen Permeability of Nb40Ti30Ni30 alloy
International Journal of Hydrogen Energy, 2016Co-Authors: Kazuhiro Ishikawa, H. Habaguchi, N. Obata, Y. Kobori, N. Ohtsu, Kiyoshi AokiAbstract:Abstract The formation of oxides on the surface of Nb40Ti30Ni30 alloy by annealing in air at elevated temperatures and the effect of an intermediate oxide layer on the Hydrogen Permeability of a Pd/alloy composite were investigated. Oxides were formed when the Nb40Ti30Ni30 alloy was annealed in air for 2 h; Nb6O below 773 K, Nb6O + TiO2+Ti4Ni2O at 873 K and Nb6O + TiO2+Ti4Ni2O + Nb2O5 at 973 K. The Hydrogen Permeability of the Pd/oxide/Nb40Ti30Ni30 composite oxidized below 773 K was slightly higher than that of the oxide-free Pd/Nb40Ti30Ni30 composite after 100 h. XPS analysis revealed that penetration between Pd and alloy elements was suppressed by the oxide layer. In contrast, the composite oxidized at 873 K showed low Hydrogen Permeability that remained fairly constant for 100 h. The oxide layer contributes a barrier to the diffusion of Hydrogen and metallic atoms, which suggests that control of the structure and thickness of the oxide layer is important to achieve both high Hydrogen Permeability and low degradation.
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Microstructure and Hydrogen Permeability in Nb-TiFe alloys
Journal of Alloys and Compounds, 2013Co-Authors: Kazuhiro Ishikawa, Shogo Watanabe, Kiyoshi AokiAbstract:Abstract The relationship between the microstructure and Hydrogen Permeability of Nb–TiFe alloys is investigated. The fully eutectic alloy, which consisted of the bcc-(Nb, Ti) and B2-TiFe phases, is found in the Nb16Ti53Fe31 composition. The alloys formed between the Fe50Ti50 and Nb16Ti53Fe31 compositions, expressed as (Ti50Fe50)1−x(Nb16Ti53Fe31)x, consist of the eutectic structure, including the primary TiFe phase for x 1. The volume fraction of the primary phase is decreased (0 1) with increasing x. The alloys with 0.4
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Hydrogen Permeability and microstructure of rapidly quenched Nb–TiNi alloys
Journal of Alloys and Compounds, 2011Co-Authors: Kazuhiro Ishikawa, Yuta Seki, Koichi Kita, Minoru Nishida, Kiyoshi AokiAbstract:Abstract Effect of annealing on structure, microstructure and Hydrogen Permeability of rapidly quenched Nb 30 Ti 35 Ni 35 and Nb 40 Ti 30 Ni 30 alloy ribbons were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and the gas flow method. Crystalline (Nb, Ti) and TiNi phases coexisted with the amorphous phases in the as-quenched Nb 30 Ti 35 Ni 35 alloy, while only crystalline (Nb, Ti) and TiNi phases were formed in the as-quenched Nb 40 Ti 30 Ni 30 alloy. Both the as-quenched alloys were too brittle to measure their Hydrogen Permeability, but they became ductile by annealing above 1173 K and showed the microstructure consisting of the crystalline (Nb, Ti) phase embedded in the crystalline TiNi matrix. The volume fraction of the (Nb, Ti) phases in the Nb–TiNi alloys increased with increasing Nb content. Hydrogen Permeability at 673 K, i.e. Φ 673 K of the crystalline Nb 30 Ti 35 Ni 35 and Nb 40 Ti 30 Ni 30 alloys was 1.1 × 10 −8 and 1.9 × 10 −8 (molH 2 /m/s/Pa 0.5 ), respectively, which were comparable with that of Pd. The present work has clearly demonstrated that the rapid quenching technique and subsequent annealing process are useful and attractive method for the preparation of Hydrogen permeable Nb–TiNi alloy membrane.
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Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy
Materials Science Forum, 2010Co-Authors: Wei Liang Wang, Kazuhiro Ishikawa, Kiyoshi AokiAbstract:In general, Hydrogen PermeabilityΦ of the alloy membrane is expressed as the product of the Hydrogen diffusion coefficient D and the Hydrogen solution coefficient K. Therefore, to improve the Hydrogen Permeability efficiently, the values of K and D should be separately considered. In the present study, Hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the Hydrogen flow method and compared with those of palladium. The Hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of Hydrogen pressure and Hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the Hydrogen Permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.
Mary Laura Lind - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Permeability and mechanical properties of NiNb-M (M = Sn, Ti and Zr) amorphous metallic membranes
Journal of Alloys and Compounds, 2016Co-Authors: Tianmiao Lai, Sudhanshu S. Singh, Arun Sundar S. Singaravelu, Kaushik Sridhar Vadari, Afsaneh Khosravi, Nikhilesh Chawla, Mary Laura LindAbstract:Abstract In this paper, we report on the Hydrogen Permeability at 673 K of 45-μm thick splat-quenched Ni60Nb35M5 (M = Sn, Ti and Zr) amorphous metallic membranes. Changes in mechanical properties, induced by Hydrogen, were evaluated by nanoindentation. The effect of different elemental substitutions on both the Hydrogen Permeability and the thermal stability are discussed. Membrane crystalline structure was probed with X-ray diffraction and membrane thermal properties were analyzed with differential scanning calorimetry. The Young’s modulus and hardness changes of the membranes were measured by nanoindentation. All of these ternary Ni–Nb membranes maintain their amorphous structure after 24 h of Hydrogen Permeability testing at 673 K. The Ni60Nb35Zr5 alloy membranes exhibited a Hydrogen Permeability of 10−10 mol m−1 s−1 Pa−0.5, the maximum of the three compositions tested. The Hydrogen Permeability declined slightly with time during the testing. Overall the amorphous metallic membranes were thermally stable and maintained their amorphous structure. A decrease in free volume is hypothesized to be the reason for i) the increase of Young’s modulus and hardness; ii) Hydrogen Permeability decrease over time.
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the Hydrogen Permeability of cu zr binary amorphous metallic membranes and the importance of thermal stability
Journal of Membrane Science, 2015Co-Authors: Tianmiao Lai, Huidan Yin, Mary Laura LindAbstract:Abstract We synthesized three compositions of amorphous metallic Cu–Zr (Zr=37, 54, 60 at%) membranes by splat quenching. We measured the thermal properties with differential scanning calorimetry (DSC). We tested Hydrogen Permeability of the membranes before and after Pd coatings. Experimentally, we found that the Hydrogen Permeability of the alloys is lower than that predicted by existing modeling results; we hypothesize this may be the result of oxides formed on the surface of our membranes. The formation of oxides is composition dependent. The Permeability change during the testing time indicates that Hydrogen has promoted structural change at a temperature lower than the glass transition temperature (Tg). Our original experimental results show that thermal stability is critical for Hydrogen separation applications in amorphous metallic membranes.
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Heat treatment driven surface segregation in Pd77Ag23 membranes and the effect on Hydrogen Permeability
International Journal of Hydrogen Energy, 2015Co-Authors: Mary Laura LindAbstract:Abstract We applied different heat treatment to commercial Pd77Ag23 membranes to promote surface segregation and measured the influence of surface segregation on Hydrogen Permeability. We report X-ray photoelectron spectroscopy (XPS) analysis of the surface elemental composition of the membranes. We used atomic force microscopy (AFM) to observe the surface roughness and area change. We found that surface composition varied with the method of heat treatment. The surface area of all membranes increased after heat treatment. We found that the higher the surface Pd/(Pd + Ag) ratio, the higher the Hydrogen Permeability. We demonstrate that surface carbon removal and surface area increase do not explain the observed Permeability differences. The vacuum level during the heat treatment is crucial to promote Ag surface segregation of membranes. After exposure to Hydrogen, we observed reverse segregation (Pd segregation).
Hiroshi Yukawa - One of the best experts on this subject based on the ideXlab platform.
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A Review for Consistent Analysis of Hydrogen Permeability through Dense Metallic Membranes.
Membranes, 2020Co-Authors: Asuka Suzuki, Hiroshi YukawaAbstract:The Hydrogen permeation coefficient (ϕ) is generally used as a measure to show Hydrogen permeation ability through dense metallic membranes, which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However, the Hydrogen Permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper, various methods for consistent analysis of Hydrogen Permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of Hydrogen Permeability are introduced: (1) prediction of Hydrogen flux under given conditions, (2) comparability of Hydrogen Permeability, (3) understanding of the anomalous temperature dependence of Hydrogen Permeability of Pd-Ag alloy membrane, and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high Hydrogen Permeability together with strong resistance to Hydrogen embrittlement.
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Alloying effects on Hydrogen Permeability of V without catalytic Pd overlayer
Journal of Alloys and Compounds, 2015Co-Authors: Y. Nakamura, Asuka Suzuki, Hiroshi Yukawa, Tomonori Nambu, Yoshihisa Matsumoto, Yoshinori MurataAbstract:Abstract Hydrogen Permeability of air–treated V–based alloy membranes without Pd coating have been investigated. The diffusion–limiting Hydrogen permeation reaction takes place even without catalytic Pd overlayer on the surface. It is shown that pure V and its alloy membranes without Pd overlayer possess excellent Hydrogen Permeability and good durability at high temperature. The new description of Hydrogen permeation based on Hydrogen chemical potential has been applied and the Hydrogen flux is analyzed in terms of the mobility of Hydrogen atom and the PCT factor, f PCT .
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Consistent description of Hydrogen Permeability through metal membrane based on Hydrogen chemical potential
International Journal of Hydrogen Energy, 2014Co-Authors: Asuka Suzuki, Hiroshi Yukawa, Tomonori Nambu, Yoshihisa Matsumoto, Yoshinori MurataAbstract:Abstract A new description of the Hydrogen permeation through metal membrane has been proposed according to the diffusion equation based on the Hydrogen chemical potential. The diffusion of Hydrogen atom through metal membrane is found to be linked with the shape of the pressure-composition-isotherm (PCT curve) of the material. Thus, the analysis of the PCT curves is very important to understand the Hydrogen Permeability of metal membranes. The validity of the new diffusion equation has been verified by a series of Hydrogen permeation test with a pure niobium membrane. There is a linear relationship between the Hydrogen flux and the PCT factor, f PCT , indicating that the Hydrogen flux obeys the new diffusion equation. This new description of Hydrogen Permeability is very useful for alloy design and setting the permeation conditions to get high Hydrogen flux through metal membrane.
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Design of group 5 metal-based alloy membranes with high Hydrogen Permeability and strong resistance to Hydrogen embrittlement
Advances in Hydrogen Production Storage and Distribution, 2014Co-Authors: Hiroshi Yukawa, Tomonori Nambu, Yoshihisa MatsumotoAbstract:Abstract: Hydrogen permeable metal membranes are important materials for the effective production of high purity Hydrogen. The low cost and high Hydrogen Permeability of group 5 metals – vanadium, niobium and tantalum – will make them preferable to Pd-based alloys for future high performance Hydrogen permeable membranes. However, their poor resistance to Hydrogen embrittlement is currently a problem for their practical use. This chapter considers recent developments in these Hydrogen permeable membranes using single solid solution phase of Nb- and V-based alloys, which exhibit strong resistance to Hydrogen embrittlement together with excellent Hydrogen Permeability.
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Alloying effects of Ru and W on the resistance to Hydrogen embrittlement and Hydrogen Permeability of niobium
Journal of Alloys and Compounds, 2008Co-Authors: N. Watanabe, Hiroshi Yukawa, Tomonori Nambu, Yoshihisa Matsumoto, G.x. Zhang, Masahiko MorinagaAbstract:Abstract The alloying effects of ruthenium and tungsten on the Hydrogen solubility, the resistance to Hydrogen embrittlement and the Hydrogen Permeability are investigated for Nb–M (M = Ru and W) alloys. The Hydrogen solubility decreases by alloying and also by increasing the temperature of the alloy. As a result, the resistance to Hydrogen embrittlement is improved owing to the low Hydrogen content in the alloy. On the other hand, the Hydrogen flux increases with increasing Hydrogen concentration difference, ΔC, between the inlet and outlet sides of the alloy membrane. It is found that Nb–5 mol%X (X = Ru and W) alloys possess excellent Hydrogen Permeability without showing any Hydrogen embrittlement when used under the appropriate permeation conditions of the temperatures and Hydrogen pressures.
John Mickalonis - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Permeability of multiphase v ti ni metallic membranes
Materials Letters, 2007Co-Authors: Thad Adams, John MickalonisAbstract:Development of advanced Hydrogen separation membranes in support of Hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national Hydrogen economy. Current generation metallic Hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and Hydrogen Permeability. Electrochemical Hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state Hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.
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Hydrogen Permeability of multiphase V–Ti–Ni metallic membranes
Materials Letters, 2007Co-Authors: Thad Adams, John MickalonisAbstract:Development of advanced Hydrogen separation membranes in support of Hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national Hydrogen economy. Current generation metallic Hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate a Group 5A-Ta, Nb, V-based alloy with respect to microstructural features and Hydrogen Permeability. Electrochemical Hydrogen permeation testing of the V-Ti-Ni alloy is reported herein and compared to pure Pd measurements recorded as part of this same study. The V-Ti-Ni was demonstrated to have a steady state Hydrogen permeation rate an order of magnitude higher than the pure Pd material in testing conducted at 22 C.
