Study of milling time impact on hydrogen desorption from LiAlH₄-Fe₂O₃ composites

LiAlH₄ was modified by mechanical milling and with the addition of 5 wt.% Fe₂O₃ in order to improve its hydrogen desorption properties. The composite was milled for 1, 3, 5, 7 or 15 min, and depending on the milling time, various phenomena took place. Up to a milling time of 5 min, the particle size of the composite decreases. Further milling leads to the particles agglomeration reaching the size of the starting material after 15 min. Moreover, the mechanical milling process leads to the transformation of AlH₄^– to AlH₆^{3 –} structure as a result of partial hydrogen desorption. Hydrogen desorption during the milling is the most pronounced in the sample milled for 15 min, so this sample has only one hydrogen desorption peak in the temperature-programmed desorption measurements. Mechanical milling with the addition of Fe₂O₃ for up to 15 min improves LiAlH₄ hydrogen desorption properties as hydrogen desorption temperature and apparent activation energies decrease.