Growth kinetics of MgH2 nanocrystallites prepared by ball milling

Abstract

MgH2 is one of promising hydrogen storage materials due to its high hydrogen capacity of 7.6 wt%. However, MgH2 nanocrystallites easily grow up during hydrogen absorption―desorption cycling, leading to deterioration of hydrogen storage properties. To clarify the growth kinetics of MgH2 crystallites, the growth characteristics of MgH2 nanocrystallites are investigated in this work. The growth exponents of MgH2 nanocrystallites in pure MgH2 and MgH2―10 wt% Pr3Al11 samples are evaluated to be n = 5 and n = 6, respectively. Meanwhile, their activation energies for crystallite growth are also determined to be 109.2 and 144.2 kJ/mol, respectively. The increase of growth exponent and rise of activation energy for crystallite growth in MgH2―10 wt% Pr3Al11 composite are ascribed to the presence of nano-sized Pr3Al11 phase.