元素揮發對Mg-Ni-Li合金儲放氫特性之影響

Effect of element evaporation on the hydrogen storage properties of Mg-Ni-Li alloy

劉人豪(Jen-hao Liu)

指導教授 ： 李勝隆

國立中央大學/工學院/材料科學與工程研究所/碩士(2008年)

摘要

本實驗於鑄態過共晶Mg-Ni合金(hypereutectic Mg-Ni alloy)中添加Li，觀察Li於300℃高溫下之揮發穩定性對過共晶(Mg-Ni)合金儲放氫特性之影響。
由X光繞射分析得知，鑄態Mg82Ni18合金為Mg與Mg2Ni兩相所構成，而含2 wt.% Li之Mg82Ni18合金為Mg(Li)與Mg2Ni兩相所構成，當Li含量增加至5 wt.%時，Mg(Li)固溶體將轉變成Li(Mg)固溶體結構，但其Li繞射峰角度與純Li之繞射峰角度無明顯差異。
經300 ℃之充分活化後，由於Li的揮發，造成含Li合金之結構回復為不含Li之Mg82Ni18合金結構，但其吸放氫量並無法回復，且隨著Li含量之增加而遞減。其中，含Li之Mg82Ni18合金隨著Li的揮發，共晶Mg與Mg2Ni的結合性降低，導致Mg2Ni催化能力降低，以致於催化距離減少，致使Mg元素吸放氫平台長度大幅縮短。此外，因Li的揮發，亦造成Mg2Ni之吸氫平台亦有微幅降低的現象。

關鍵字

儲放氫特性 ； XRD ； Mg82Ni18 ； Li

並列摘要

In this study, Li was added in hypereutectic Mg-Ni alloys for researching the effect of Li addition and evaporation on the hydrogen storage properties of hypereutectic Mg-Ni alloy.
From XRD, there were only Mg and Mg2Ni phases exiting in the as-cast Mg82Ni18 alloy. But Mg(Li) and Mg2Ni phases was observed in the as-cast Mg82Ni18 alloy with 2 wt.% Li. When Li contents enhanced to 5 wt.%, the phases transferred to Li and Mg2Ni.
The structure of Mg82Ni18 alloys with Li contents returned to Mg and Mg2Ni phases after Li evaporation, but the hydrogen capacity decreased with Li contents increasing. The length of first plateau (Mg+H2 → MgH2) decreased appreciably, it is assumed Li addition and evaporation in Mg82Ni18 alloy weaken the bonding of eutectic Mg with Mg2Ni and decreased catalyzing effect of Mg by Mg2Ni. Otherwise, the length of second plateau(Mg2Ni+2H2 → Mg2NiH4) also decreased slightly.

並列關鍵字

XRD ； hydrogen storage ； Li ； Mg82Ni18 alloys

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