Effects of Temperature and Pressure on De-/Re-hydrogenation Behavior of Lithium Alanate mixed with Magnesium Hydride.

• Main Authors: I-ChunLin, 林怡君
• Other Authors: Wen-Ta Tsai
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/8nhwwa

碩士 === 國立成功大學 === 材料科學及工程學系 === 105 === Rehydrogenation behavior of the discharged MgH2-LiAlH4 composites was investigated by using thermal gravimetric analysis (TGA) and in situ synchrotron X-ray diffraction (XRD) technique. For 4MgH2-LiAlH4 composite, the experimental results showed that at least 3 wt% of hydrogen could be recharged during rising pressure to 3.1MPa/H2 at 400 °C to form MgH2 after its first dehydrogenation reaction. The faster hydrogen absorption rate 0.065 wt%/min happened between 0.17 MPa ~ 1.38 MPa. The XRD results indicated that it would have different absorption reaction in the various pressure interval by using various MgH2-LiAlH4 composite. (Table 1) Not only Mg but also Mg17Al12 and Mg2Al3 could be rehydrogenated in the hydrogen atmosphere investigated although LiAlH4 was found irreversible. In the experiment of isobaric, we know that it must be more than 1.38 MPa would have a better amount of hydrogen absorption and reaction time. In the cyclic test, the second test had the extent of hydrogen absorption 100 %, and the third one had 90%. Both of them were good. The In-situ synchrotron XRD results indicated that the reversibility of the MgH2-LiAlH4 composite which was temperature-dependent.