| 摘要: | 為解決化石能源衍生之各項問題，各國莫不積極尋求替代能源與解決之道，而氫能作為一種潔淨能源已漸受重視，儲氫合金即是伴隨氫能發展而被看好的新型功能材料，此乃以儲氫合金儲存氫具有體積儲存密度高、安全性高、儲存時間長、無損耗等優點。儲氫合金之儲氫原理是使大量氫氣為金屬吸收後轉變成金屬氫化物形式儲存，氫以固態結合形式儲存於其中，與金屬氫化物間進行可逆反應，當外界施予金屬氫化物熱量時，即可分解為儲氫合金並釋放出氫氣。儲氫合金以粉末之物相形成與作用，應用之際尚需一套具備控制氫氣出入口之密閉性裝填容器（本計畫稱為儲氫合金罐）作為反應平台。當氫原子擴散進入儲氫合金並造成相變態後，會引起晶格膨脹，使儲氫合金晶格體積變大，晶格被撐大甚至變形破裂，此時體積膨脹所產生之應力容易造成儲氫合金粉碎化現象，而罐體將承受罐內氫氣壓力及金屬氫化物體積膨脹之總合作用力，若罐體結構設計不良，即可能產生變形及破損，所以儲氫合金吸氫之體積膨脹應變及對罐體造成之影響為儲氫合金罐結構設計所需考量之首要因子。本研究計畫將以未來極具商業化潛力之高儲氫量鎂鎳合金做為研究對象，針對其應用上所需之高溫儲氫合金罐，於結構設計所應掌握之合金及罐體膨脹行為模式進行深入探討，開發有效之設計分析技術，作為設計高效率、高安全性、低成本儲氫合金罐之用。本研究規劃進行實驗量測與力學分析，從改變吸放氫反應溫度、合金粒徑、合金裝填量、罐體壁厚及內裝構型設計等實驗條件著手，分析合金體積膨脹率演化、粉末細化堆疊模式及相對應於罐體所產生應力應變之變化情形，從而瞭解儲氫合金罐之變形與破損機制，進而建立高儲氫量鎂鎳合金儲氫罐膨脹力學作用模式，提供未來設計高溫型儲氫合金罐結構與評估其耐久壽命之參考。各分年研究重點為：(1)第一年（目前執行中）：設計與建構高溫型Mg2Ni 儲氫合金罐吸放氫反應實驗裝置，進行於不同溫度、填充率、粉末粒徑組合實驗條件下之儲氫合金罐膨脹應變量測，並發展膨脹應力分析模式；(2)第二年（本申請案）：進行於不同罐體結構設計下之儲氫合金罐膨脹應變量測，建立適用於高溫型儲氫合金罐結構設計之變形與應力分析技術。 Problems related to the use and depletion of fossil fuels have led to significant research effort on alternative and cleaner fuels in which hydrogen is considered one of the most promising candidates. World wide interest in the use of hydrogen has led to much research on its storage and usage. Recently, using metal hydrides for hydrogen storage has been receiving more and more attention thanks to advantageous characteristics such as low operating pressure, high level of safety, and high volumetric density. Metal hydrides can provide a reversible way of storing hydrogen from the gaseous phase within a solid material. One of the concerns with the use of metal hydrides is the container, or called storage vessel. Metal hydrides expand, possibly 20 to 35% in volume, during the hydriding step and create a large stress on the alloy and the storage vessel. The alloy powders tend to fragment into smaller particles through a pulverization mechanism, as a result of this stress. This leads to material movement and segregation in the storage vessel, which generate large internal pressure. Also, as the alloy powders become smaller, there is an increasing tendency for the hydride fines to flow in the gas streams. Therefore, the storage vessel system must accommodate these small particles and the resulting expansion. Strain in the vessel wall should not be overlooked when assessing the practical use of hydrides for hydrogen storage. If uncontrolled, these strains can result in vessel failure. Therefore, it is important to study the structural design requirements for a safe and cost-effective hydride storage vessel. The aim of this proposal is to develop effective analysis tools for assessment of vessel wall strain variation during the hydriding process for a high hydrogen-storage-capacity alloy, Mg2Ni, which is a promising candidate for commercial usage. In order to develop a highly efficient and reliable high-temperature metal hydride storage vessel, several issues need to be studied for critical design considerations. Both experimental and theoretical approaches will be implemented in this study. In the experimental program, simple-shaped storage vessels filled with alloy powders are designed, fabricated and tested in the ongoing, first year to investigate the alloy pulverization and expansion characteristics and their influence on vessel wall strain during high-temperature hydriding/dehydriding cycles. Effects of reaction temperature, alloy powder size, and alloy powder packing fraction on vessel wall strain variation will be systematically studied. In the theoretical program, mathematical models to describe the expansion and pulverization behavior of metal hydrides will also be developed and numerically solved in the ongoing, first year. In the currently proposed, second-year work, effects of vessel structural design and dimensions on vessel wall strain variation will be studied with several modified designs of the interior structure of the vessel. In addition, the numerical results for these modified designs will be compared with the experimental data to validate the mathematical models. Based on the experimental and numerical results, an effective technique for improving design of a high-temperature metal hydride storage vessel with reliable structural integrity is intended to be developed for use in the high hydrogen-storage-capacity Mg2Ni alloy. 研究期間：9908 ~ 10007 |
