填充率及粒徑大小對鎂鎳合金儲氫罐膨脹應變之影響; Effects of Packing Fraction and Particle Size on the Expansive Deformation in the Reaction Vessel of Mg2Ni Alloy

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Title:	填充率及粒徑大小對鎂鎳合金儲氫罐膨脹應變之影響;Effects of Packing Fraction and Particle Size on the Expansive Deformation in the Reaction Vessel of Mg2Ni Alloy
Authors:	黃思銘;Sih-ming Huang
Contributors:	機械工程研究所
Keywords:	鎂鎳合金;儲氫罐;膨脹應變;Mg2Ni;hydride storage vessel;expansion;strain
Date:	2009-07-08
Issue Date:	2009-09-21 12:06:20 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	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.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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