本研究主旨在探討LaNi5儲氫合金罐體在循環吸放氫作用之下，填充於罐體中的粉末量以及初始粒徑尺寸對於罐壁應變變化的影響，並分析探討LaNi5儲氫合金罐體結構設計對於罐體膨脹變形之影響。實驗採用三種不同罐體內部設計，實驗條件為在3.2MPa氫氣壓力下吸氫，真空狀態下放氫，於室溫下連續進行吸放氫逾50至80次，並利用掃瞄式電子顯微鏡觀察LaNi5合金粉末在活化前、實驗中各個階段以及實驗後的外觀型貌與尺寸變化。 結果顯示，在吸放氫循環過程中，合金粉末的膨脹會使罐體外壁產生明顯的應變值。合金粉末粉碎化現象在中空型罐體當中，無可避免地會在罐體底部產生較大程度的罐壁應變。中空型罐體在較多粉末填充量的條件下，每單位質量合金的吸氫量比較低填充量條件下來得低，這是由於有較多粉碎細化粉末緻密堆積結塊，使得氫氣與合金粉末無法完全反應所致。氣體通道的增設提供了更多氫氣於儲氫容器中流動的能力，使得氫氣更容易與合金粉末進行反應，有效改善合金粉末的儲氫量，同時罐壁的應變值也因為氣體通道緩衝了合金粉末的膨脹而減少。罐體內隔層腔體的設計，可使合金粉末均勻地配置在罐體各部位，有效減少合金粉末緻密堆積結塊的情形。相較於中空型以及增設氣體通道的罐型設計，隔層多腔體的罐型設計可大幅度有效降低容器罐壁因合金粉末膨脹所產生之變形量。在罐體增設氣體通道之下，以及均勻分散粉末於腔體當中的配置，相對於中空形罐體設計，可以達到較高的合金粉末儲氫量。總而言之，對於儲氫合金罐體的設計與應用，於合金罐體內增設氣體通道及隔層腔體，可以達到符合安全以及較高效率的要求。 The purpose of this study is to investigate variations of the wall strain on the hydride storage vessel of LaNi5 alloy with different packing fractions and particle sizes during cyclic hydriding/dehydridng processes. Three structural designs of metal hydride storage vessels were applied for the expansive deformation analysis. The LaNi5 alloy powders were repeatedly hydrided with 3.2 MPa hydrogen and then dehydrided with vacuum at room temperature during the cyclic test. The morphology of the LaNi5 alloy powders before activation and after the cyclic test was analyzed with scanning electron microscopy. Experimental results showed that strains induced on the vessel wall by volume expansion of the metal hydrides of LaNi5 were noticeable. Unavoidable pulverization and agglomeration of alloy powders in a hollow type of vessel led to a great extent of strain accumulation at a lower position. During a cyclic hydriding/dehydriding process, a larger packing fraction in a hollow vessel exhibited a lower hydrogen storage capacity for a given initial particle size. An internal gas tunnel built in the reaction vessel could enhance the hydrogen storage capacity by providing more flow paths for the hydrogen to react with the alloy powders. The induced expansion deformation on vessel wall was reduced, as the internal gas tunnel could also absorb the stresses induced by the volume expansion of hydrides. The built-in separators in a multi-chamber vessel could evenly distributed the alloy powders into various chambers and effectively avoided densification and agglomeration of alloy powders at lower positions during cyclic hydriding/dehydriding processes. Therefore, accumulation of the wall strain in the hoop direction was significantly reduced to a very small level in a multi-chamber reaction vessel. In summary, for design of a metal hydride storage vessel with a greater safety and efficiency, addition of separators and internal gas tunnels inside the reaction vessel is a favorable consideration.
