Waste AZ91D magnesium alloy chip as hydrogen storage material: its hydrogen storage properties and modification

• Main Authors: Yu-Cheng Liu, 劉育承
• Other Authors: Chun Chiu
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/66667445736315515643

碩士 === 國立臺灣科技大學 === 機械工程系 === 104 === AZ91D alloy powders were prepared by mechanical milling of waste AZ91D alloy chips with different air exposure times. During the milling process, 10 mol% of In metal powder and 5 wt% of NbF5 were added to investigate the feasibility of thermodynamic destabilization and kinetic improvement of Mg-based hydrogen storage materials. We found that air exposure time has no significant effect on hydrogen storage property. The reversible hydrogen storage capacities for AZ91D alloy powders with different air exposure times are all around 6 wt%. For the AZ91 alloy powders added with 10 mol% of In, Mg-In intermetallic compounds are formed after hydrogenation at 375°C under 5.3 MPa of hydrogen, which result in a reduced hydrogen capacity of 3 wt%. The hydrogen capacity bounces back slightly after 5 wt% of NbF5 is added into the 10 mol%-In-contained AZ91D powder. However, the hydrogen desorption time increases after adding 5 wt% of NbF5, which is known as a good catalyst for MgH2. XRD results also show that addition of 5 wt% of NbF5 reduces the amount of Mg(In) solid solution, which lowers the effect of thermodynamic destabilization produced by addition of In in the Mg-based alloys. DTA results show AZ91D alloy powder added with 10 mol% of In has lower hydrogen desorption temperature than that of pure AZ91D alloy powder. The hydrogen desorption temperature could further reduce if 5 wt% of NbF5 is added.