Hydrogenation properties of Mg-based hydrogen storage materials synthesized by mechanical alloying method

• Main Authors: Kwen-Chou Wu, 吳坤洲
• Other Authors: Chia-ChiehShen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/06222713820849776142

碩士 === 元智大學 === 先進能源碩士學位學程 === 100 === The aim of this study is to develop high performance Mg-Ti hydrogen storage materials by mechanical alloying method. As-received MgH2 without ball-milled can absorb hydrogen of 3.2 wt % within 30 minute at 300 ℃. After ball milling for 10 h, the MgH2-10h can absorb hydrogen of 6.8 wt % at the same condition. The dispersion of TiH2 on the MgH2 was good according to the result of the SEM-EDS area mapping. The superimposed of X-ray diffraction peaks of the TiH2 (111) and MgH2 (101) indicated that the two starting material have now become composite with β-MgH2 + δ-TiH2 + FCC-MgH2. Based on the TPD desorption curves, MgH2 doped with TiH2 started to release hydrogen gas at 200 ℃. The as-milled MgTi materials can absorb hydrogen of 3.7 and 5.5 wt %, respectively at room temperature 25 ℃ and 300 ℃ within 3 minutes. This significant enhanced hydrogen absorption rate was ascribed to the δ-TiH2-y-catalyst, in which H atoms can be pumped to Mg through the y vacancy lattice sites of TiH2-y. The PCI curves indicates that both hydrogen absorption and desorption pressures can be increased with reaction time of ball milling. According to van’t Hoff plots, the enthalpy and entropy of the FCC-MgH2 was estimated to be 78.2±1.5 kJ/mol H2 and -233.2±2 J/k mol H2,respectively.