本研究主旨在探討鎂鎳合金儲氫罐在循環吸放氫作用下，不同粉末填充率及粉末大小對其罐壁應變變化的影響，並同時探討在儲氫罐內建一氣體通道其對壁應變及儲氫量的影響。實驗條件為在3 MPa氫氣壓力下吸氫，在真空狀態下放氫，吸放氫溫度為255 oC，並利用SEM觀察Mg2Ni合金粉末活化前及實驗結束後的型態與大小。
結果顯示，在儲氫罐表面之特定位置上，其切線方向應變隨著粉末填充率提高而增加，這是由於較高的粉末填充率產生較多的粉碎細小粉末所導致。在較低粉末填充率的情況下，儲氫罐壁上的切線方向應變將隨著粉末粒徑增大而增加。在較高粉末填充率的情況下，較大的吸氫應變會出現在裝填較大初始粒徑粉末的儲氫罐壁上，而較大的放氫應變則會出現在裝填較小初始粒徑粉末的儲氫罐壁上。裝填較小初始粒徑粉末的儲氫罐，由於較易產生大量的粉末堆積結塊，在實驗結束後發現吸氫量將會大幅度的減少。在儲氫罐內部建立一個氣體通道將有效的增加儲氫罐儲氫量及減少罐壁上的應變。總而言之，較大粒徑的初始粉末及內建氣體通道皆有利於提升金屬氫化物儲氫罐的儲氫量。

The purpose of this study is to investigate variations of the wall strain on the storage vessel of Mg2Ni alloy with different packing fractions and particle sizes during cyclic hydriding/dehydridng processes. A modification of hydride storage vessel with an internal gas tunnel is also investigated for its influence on the wall strain and hydrogen storage capacity. The reaction pressure conditions for the absorption and desorption steps were of 3 MPa and vacuum, respectively, at 255 oC. The particle morphology of the Mg2Ni alloy before activation and after a 50-cycle test was analyzed with scanning electron microscopy (SEM).
Results showed that at a given position on the storage vessel surface, the hoop strain was increased with a higher packing fraction of alloy powders during the cyclic hydriding/dehydriding reactions. This resulted from a larger amount of pulverized fine powders generated by a larger packing fraction of alloy powders. Given a lower packing fraction, the hoop strain in the vessel wall induced by the hydriding/dehydriding reactions was increased with alloy powder size. For a higher packing fraction, a greater absorption strain was induced in the vessel packed with a larger initial powder size, while a greater desorption strain was present in the vessel packed with a smaller initial powder size. A greater extent of degradation of absorbed hydrogen content at the end of the 50-cycle test was observed for a smaller initial size of alloy powders as a result of formation of a larger agglomerated stack of alloy powders. A gas tunnel built at the center of the vessel was effective for enhancing the hydrogen storage capacity of the vessel and reducing the surface strain on the vessel wall. In summary, a larger initial powder size and an internal gas tunnel are favorable conditions for enhancing the hydrogen storage content of a metal-hydride reaction vessel.

1. S. Oberthur and H. E. Ott, The Kyoto Protocol: International Climate Policy for the 21st Century, Springer, Berlin, Germany, 1999.
2. T. J. Carter and L. A. Cornish, “Hydrogen in Metals,” Engineering Failure Analysis, Vol. 8, 2001, pp. 113-121.
3. A. Midilli, M. Ay, I. Dincer, and M. A. Rosen, “On Hydrogen and Hydrogen Energy Strategies I: Current Status and Needs,” Renewable and Sustainable Energy Reviews, Vol. 9, 2005, pp. 255-271.
4. A. Zuttel, “Materials for Hydrogen Storage,” Materials Today, September, 2003, pp. 24-33.
5. U. Eberle, G. Arnold, and R. von Helmolt, “Hydrogen Storage in Metal-Hydrogen Systems and Their Derivatives,” Journal of Power Sources, Vol. 154, 2006, pp. 456-460.
6. B. Sakintuna, F. Lamari-Darkrimb, and M. Hirscher, “Metal Hydride Materials for Solid Hydrogen Storage: A Review,” International Journal of Hydrogen Energy, Vol. 32, 2007, pp. 1121-1140.
7. M. Martin, C. Gommel, C. Borkhart, and E. Fromm, “Absorption and Desorption Kinetics of Hydrogen Storage Alloys,” Journal of Alloys and Compounds, Vol. 238, 1996, pp. 193-201.
8. G. Sandrock, “A Panoramic Overview of Hydrogen Storage Alloys from a Gas Reaction Point of View,” Journal of Alloys and Compounds, Vol. 293-295, 1999, pp. 877-888.
9. H. Yukawa, K. Nakatsuka, and M. Morinaga, “Design of Hydrogen Storage Alloys in View of Chemical Bond Between Atoms,” Solar Energy Materials and Solar Cells, Vol. 62, 2000, pp. 75-80.
10. E. Akiba and H. Iba, “Hydrogen Absorption by Laves Phase Related BCC Solid Solution,” Intermetallics, Vol. 6, 1998, pp. 461-470.
11. S. Satyapal, J. Petrovic, C. Read, G. Thomas, and G. Ordaz, ”The U. S. Department of Energy’s National Hydrogen Storage Project: Progress Towards Meeting Hydrogen-Powered Vehicle Requirements,” Catalysis Today, Vol. 120, 2007, pp. 246-256.
12. P. Selvam, B. Viswanathan, C. S. Swamy and V. Srinivasan, “Magnesium and Magnesium Alloy Hydrides,” International Journal of Hydrogen Energy, Vol. 11, 1986, pp. 169-192.
13. T. Malinova and Z. X. Guo, “Artificial Neural Network Molding of Hydrogen Storage Properties of Mg-based Alloys,” Material Science and Engineering, Vol. A 365, 2004, pp. 219-227.
14. J. Cermak and L. Kral, “Hydrogenation of Mg and Two Chosen Mg-Ni Alloys,” International Journal of Hydrogen Energy, Vol. 33, 2008, pp. 7464-7470.
15. ASM Handbook, Vol. 3, ASM International, Materials Park, OH, USA, 1992, p. 2.281.
16. D. Sun, H. Enoki, F. Gingl, and E. Akiba, “New Approach for Synthesizing Mg-based Alloys,” Journal of Alloys and Compounds, Vol. 285, 1999, pp. 279-283.
17. Z. Dehouche, R. Djaozandry, J. Goyette, and T. K. Bose, ”Evaluation Techniques of Cycling Effect on Thermodynamic and Crystal Structure Properties of Mg2Ni Alloy,” Journal of Alloys and Compounds, Vol. 288, 1999, pp. 269-276.
18. Q.-D. Wang, J. Wu, C.-P. Chen, and Z.-P. Li, ”An Investigation of the Mechanical Behaviour of Hydrogen Storage Metal Beds on Hydriding and Dehydriding and Several Methods of Preventing the Damage of Hydride Containers Caused by the Expansion of Hydrogen Storage Metals,” Journal of the Less-Common Metals, Vol. 131, 1987, pp. 399-407.
19. S. T. McKillip, C. E. Bannister, and E. A. Clark, “Stress Analysis of Hydride Bed Vessels Used for Tritium Storage,” Fusion Technology, Vol. 21, 1992, pp. 1011-1016.
20. T. Saito, K. Suwa, and T. Kawamura, “Influence of Expansion of Metal Hydride During Hydriding-Dehydriding Cycles,” Journal of Alloys and Compounds, Vol. 253-254, 1997, pp. 682-685.
21. K. Nasako, Y. Ito, N. Hiro, and M. Osumi, “Stress on a Reaction Vessel by the Swelling of a Hydrogen Absorbing Alloy,” Journal of Alloys and Compounds, Vol. 264, 1998, pp. 271-276.
22. B. Y. Ao, S. X. Chen, and G. Q. Jiang, “A Study on Wall Stresses Induced by LaNi5 Alloy Hydrogen Absorption-Desorption Cycles,” Journal of Alloys and Compounds, Vol. 390, 2005, pp. 122-126.
23. F. Qin, L. H. Guo, J. P. Chen, and Z. J. Chen, “Pulverization, Expansion of La0.6Y0.4Ni4.8Mn0.2 During Hydrogen Absorption-Desorption Cycles and Their Influences in Thin-Wall Reactors,” International Journal of Hydrogen Energy, Vol. 33, 2008, pp. 709-717.
24. F. Qin, J. P. Chen, and Z. J. Chen, “The Hydriding-Dehydriding Characteristics of La0.6Y0.4Ni4.8Mn0.2 and Their Influences in the Surface Strain on Small-Scale, Thin-Wall and Vertical Containers,” Materials and Design, Vol. 29, 2008, pp. 1926-1933.
25. S. Ono, Y. Ishido, K. Imanari, and T. Tabata, “Phase Transformation and Thermal Expansion of Mg-Ni Alloys in a Hydrogen Atmosphere,” Journal of Less-Common Metals, Vol. 88, 1982, pp. 57-61.
26. S. Enache, W. Lohstroh, and R. Griessen, “Temperature Dependence of Magnetoresistance and Hall Effect in Mg2NiHx Films,” Physical Review, Vol. B 69, 2004, pp. 115326-1-115326-12.
27. Y.-H. Jhang, “Analysis of Wall Strain on the Reaction Vessel of Mg2Ni Alloy During Cyclic Hydriding/Dehydriding Processes,” M.S. Thesis, National Central University, 2008.
28. C. W. Hsu, S. L. Lee, R. R. Jeng, and J. C. Lin, “Mass Production of Mg2Ni Alloy Bulk by Isothermal Evaporation Casting Process,” International Journal of Hydrogen Energy, Vol. 32, 2007, pp. 4907-4911.