Cycling Characteristics of MgH2 made by Hydriding Chemical Vapor Deposition Method

The cycling characteristics of MgH2 made by hydriding chemical vapor deposition method have been investigated. The particle size of MgH2 made by HCVD was about 1 pm. The cycling experiment was performed by measuring hydrogen quantity absorbed at 673 K and under 35 atm of hydrogen pressure for 30 min. Up to 3 cycles the hydrogen storage capacity increased, but from 4 to 6 cycles the hydrogen storage capacity decreased rapidly. During this cycling test the particle size increased gradually from 1 mu m to 6 mu m. This increase was due to sintering by the high reaction temperature and the heat of reaction during hydrogen absorption. From 7 to 30 cycles, the hydrogen storage capacity was maintained at 5.8 wt%. Even after 30 cycles, the plateau pressure was constant.