Microstructural study of hydrogen desorption in 2NaBH_4 + MgH_2 reactive hydride composite

摘要

The desorption mechanism of as-milled 2NaBH_4 + MgH_2 was investigated by volumetric analysis, X-ray diffraction and electron microscopy. Hydrogen desorption was carried out in 0.1 bar hydrogen pressure from room temperature up to 450 ℃ at a heating rate of 3 ℃ min~(-1). Complete dehydrogenation was achieved in two steps releasing 7.84 wt.% hydrogen. Desorption reaction in this system is kinetically restricted and limited by the growth of MgB_2 at the Mg/Na_2B_(12)H_(12) interface where the intermediate product phases form a barrier to diffusion. During desorption, MgB_2 particles are observed to grow as plates around NaH particles.