The effect of alkaline earth metals (Magnesium and Calcium) on Hydrogen storage efficiency of alanate nanopowders

Abstract

Different Aluminum: alkaline earth metal atomic weight ratios effects on structure transformations in alanates nanopowders were studied. Changes in crystal structures from alane to alanates by increasing alkaline earth metals dopants in the mixture with slight changes in crystal structures from rhombohedral centered – trigonal (alane) to trigonal (magnesium alanate), and monoclinic (calcium alanate), while thermal behavior alters from one step dissociation at ~150 ْC with ~ 8.1 wt% hydrogen release in alane to the two steps hydrogen releases in magnesium alanate at 130 and 285 ْC with 7 and 2.1 wt% changes, and to the three steps hydrogen releases in calcium alanate at 127, 260, and 328 ْC with 1.7, 2.1, and 4 wt% changes were indicated. Residual phases after dissociation are formed in aluminum and magnesium alloying systems and intermetallic phases like Mg₂Al₃ and Mg₁₇Al₁₂ with no sign of oxide formation and pure aluminum, Al₄Ca, Al₂Ca intermetallic phases and Ca in aluminum: Calcium system.