臺灣博碩士論文加值系統

　　在所有氫氣儲存方式中，以金屬氫化物來儲存氫氣具有體積小、壓力低、且較安全的特點；而在各種介金屬氫化物中，則以AB5型的LaNi5儲氫合金具有活化容易、吸氫速率快、儲氫量大、及壓力變化平緩的平衡壓等優越特性；因此，此合金系適合用來作為儲氫特性與其應用的研究材料。
　　本論文的第一部份是針對不同合金元素的置換來探討其對儲氫特性的影響；首先，以Al, Cr, Mn, Nb, Zr取代部份的Ni，透過電弧熔煉爐製備合金，並進行真空熱處理。實驗中，使用X光繞射儀分析合金結構，並在恆溫中量測合金的吸氫動力曲線及吸氫量與氫氣平衡壓之關係曲線（P-C-T）。再選取適當的成份，以自動充放氫系統進行3000次循環測試，探討合金吸氫性能衰退的情形，並以掃描式電子顯微鏡觀察材料微粉化的情況。
　　根據實驗結果所作的分析，得知以Nb取代部份Ni時，可加速合金活化，但會降低氫氣平衡壓與吸氫量，在循環充放氫衰減的部份則有小幅的改善；以Zr取代部份Ni時，雖增加合金活化速率，但使氫氣平恆壓降低與遲滯現象擴大，另外，在循環充放氫的部份則大幅的改善了衰減和程度；以Cr取代部份Ni時，對合金活化與吸氫量有不利的影響；以Mn取代Ni不僅可促進活化速率，並降低合金的平衡壓，少量添加時還可增加合金的吸氫量與降低遲滯現象；此外，若同時以Cr, Mn取代部份Ni，可同時加速活化過程與明顯改善循環充放氫的衰減情形，但也使平衡壓大幅降低，並造成平原區明顯的傾斜。
　　本論文的另一部份是針對儲氫材料應用於燃料電池的研究，根據對鑭鎳系儲氫材料的瞭解，本研究與工業技術研究院能源與資源研究所合作，對儲氫材料應用於可攜式燃料電池組進行開發，燃料電池組本體由能源與資源研究所負責研製，本實驗室則針對氫氣供應系統進行研究；此部份實驗主要利用一套真空容積系統、質量流量計、與壓力計，量測材料吸收與放出的氫氣量，觀察是否符合電池組需求，並研究如何改善；研究方向分為儲氫材料選擇與儲氫槽設計兩部份。
　　由實驗結果得知，在儲氫材料部份，實驗中的材料最適用於燃料電池的成份是LaNi5；而在不同材質的儲氫槽中，由於銅具有最好的熱傳導特性，在放氫過程中有較佳的效果。將本實驗中設計的儲氫系統與國外相似系統比較得知，未來儲氫系統之設計應朝向高平衡壓之儲氫材料配合使用調壓閥的型式，以改善儲氫合金因儲氫槽在空氣中散熱不良，而導致放氫效果不佳的現象。

　　Among the several types of hydrogen storage materials, LaNi5, an AB5-type alloy, possesses outstanding characteristics such as easy activation, large hydrogen absorption capacity, rapid hydrogenation rate, and a flat region of plateau pressure. In this research, Partial substitution of Ni in LaNi5 and LaNi4.85Al0.15 with Cr, Mn, Nb, Or Zr was conducted. The compounds were prepared by arc furnace and heat-treated in vacuum. The crystal structures of these alloys were analyzed by X-ray diffraction (XRD). The hydrogenation properties including the kinetics and pressure-composition-temperature (P-C-T) curves were measured by a Sievert''s-type apparatus. To realize the degradation in hydrogenation, severac compositions were chosen for the cyclic absorption-desorption test for up to 3000 cycles. In addition, the morphologies of the samples after the cyclic test were examined by scanning electron microscopy (SEM).
　　The activation rate and the hydrogen absorption capacity decrease when Ni is partially substituted by Cr. The hydrogenation rate in the first cycle increases as Ni is partially replaced by Mn. The plateau pressure and the hysteresis are also decreased, but the absorption capacity increases with the substitution. The activation becomes easier and the plateau pressure is reduced as Ni is substituted with Nb or Zr, but the capacity is reduced and the plateau pressure becomes more slant as the amount of substitution increases. Niobium and zirconium also improve the stability during cyclic hydrogenation. As Ni is partially replaced by both Cr and Mn, the kinetics of hydrogenation is increased and the stability in cyclic test is improved, but the plateau pressure is reduced.