Effects of initial pressure on the decomposition of LiBH4 and MgH2 mixture

Hydrogen desorption/absorption of the LiBH4/MgH2 mixture milled for 5 h was investigated with different initial pressures. The results showed that the initial pressure played an important role in the reversibility of the LiBH4/MgH2 mixture. The stability of the hydrogen capacity in the subsequent desorption was improved with a higher initial pressure. A possible reason was from the increase in the formation of MgB2 and the lower degree in the decomposition of both LiBH4 to the amorphous phases of Li2B12H12 and B; and MgH2 to Mg, during the hydrogen desorption. However, the higher initial pressure increased the hydrogen desorption temperature. The desorption temperature was increased from 310 A degrees C for the sample decomposing under 0.1 MPa hydrogen pressure to 360 A degrees C for other cases. This may be due to the higher energy required to overcome the suppression of MgH2 and LiBH4 decomposition.