銀對於鎂鎳儲氫合金吸放氫及電化學性質之研究; ffects of Ag on hydrogen storage properties and electrochemical performances of Mg2Ni alloy

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Title:	銀對於鎂鎳儲氫合金吸放氫及電化學性質之研究;ffects of Ag on hydrogen storage properties and electrochemical performances of Mg2Ni alloy
Authors:	江建璋;Chien-chang Chiang
Contributors:	機械工程研究所
Keywords:	電化學;球磨法;吸放氫;Mg-Ni-Ag 合金;IECP;electrochemical performances;hydrogen storage;Ball milling;IECP;Mg-Ni-Ag alloy
Date:	2008-06-23
Issue Date:	2009-09-21 12:01:52 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究結合自行開發的恆溫揮發鑄造法(Isothermal Evaporation Casting Process, IECP)與球磨法，將不同含量之Ag添加於Mg2Ni合金中，研究Ag在Mg2Ni合金中的形態對於吸放氫與電化學性質之影響。 IECP法可以熔配出高純度的Mg2Ni合金，當Ag添加於Mg2Ni合金時，將形成Mg2Ni(固溶Ag)與Mg3Ag(固溶Ni)兩相，同時IECP鑄態合金的最大吸氫量隨著Ag的添加而下降，但吸氫速率沒有改善，且Ag添加到 Mg2Ni合金中，其PCI曲線呈現雙平台區，第一平台為Mg2Ni合金的氫化反應，第二平台吸氫推測為固溶部分Ni的Mg3Ag吸氫，且經ICEP法之鑄態合金對於電化學性質沒有改善；在球磨法方面，Mg2Ni合金經球磨2小時與5小時後，其XRD結果相仿，均呈現寬化與弱化的現象，而含Ag的球磨合金，在結構上依然有Ag的存在，且在退火後，會產生MgAg相。球磨法Mg2Ni合金其吸氫量下降到2.9wt.%，而含Ag的球磨合金吸氫量下降，是由於MgAg的生成，而Mg2Ni合金經球磨後，電容量提升到100 mAh/g左右，且Ag的添加導致球磨合金降低初始電容量，但循環壽命優於不含Ag之Mg2Ni合金。 A different ratio of Ag has been added in Mg2Ni by isothermal evaporation casting process (IECP) and ball milling. To research the effects of Mg-Ni-Ag alloys on the hydrogen storage properties and discharge capacity when Ag addition in Mg2Ni with different types (compounds or elements). A high purity Mg2Ni alloy will be fabricated by IEC-process. There are two phases appeared (partial Ag substituted Mg2Ni and partial Ni substituted Mg3Ag) in Ag added Mg2Ni. The hydrogen storage capacity decrease with sliver content increasing, but hydrogen absorption rate has not improved. The PCI curves show two plateaus in Ag added Mg2Ni. It is found that the hydriding mechanism of the first plateau is Mg2Ni alloy hydrogenation. The second plateau guesses partial Ni substituted Mg3Ag alloy hydrogenation. Ag addition was no effect on the discharge properties. In ball milling, there are similar results for broaden and weakened Mg2Ni and Ag peaks after ball milling 2 hours and 5 hours by X-ray diffraction (XRD). There is the new phase MgAg formed in ball-milled Mg2Ni + 20wt.% Ag alloy after annealing. The maximum hydrogen storage capacity of Mg2Ni alloy reached 2.9 wt.%, but the capacity of Mg2Ni +20wt.% Ag alloy only reached 2.0 wt.%. The capacity decrease is because of the MgAg phase formation. Discharge capacity upgraded to 100 mAh / g after Mg2Ni alloy ball-milled. Ag addition can improve cycle life by ball milling, but the maximum discharge capacities was been reduced.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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