Hydride formation in ball-milled and cryomilled Mg–Fe powder mixtures

Investigation of Effect of Milling Atmosphere and Starting Composition on Mg2FeH6 Formation

“…The synthesis of Mg 2 FeH 6 by ball milling has been studied by several authors using different milling parameters, such as: type of mill; ball to powder ratio; number and size of balls; milling time; rotational speed; milling atmosphere and hydrogen pressure [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Irrespective of the milling conditions, some iron was always detected in the milled powder representing an incomplete Mg 2 FeH 6 formation.…”

“…Some authors reported that Mg 2 FeH 6 is formed from the metallic elements [2,4,19,24], while others claimed that MgH 2 is the Mg 2 FeH 6 precursor [9,20,21,25,26]. Recently, we studied the transformation of phases during hydrogen absorption of a ball milled 2Mg + Fe mixture [27].…”

Formation reaction of Mg2FeH6: effect of hydrogen absorption/desorption kinetics

“…This is due to immiscibility of Mg and Fe and thus the absence of the intermetallic compound, which could play the role of Mg 2 FeH 6 precursor. Different techniques have been used to prepare Mg 2 FeH 6 from 2Mg-Fe or 2MgH 2 -Fe mixtures: sintering 1 , ball milling followed by sintering 3 , ball milling of 2MgH 2 -Fe 4 , reactive milling of 2Mg-Fe 5 , cryomilling 6 and high pressure synthesis 7 . Regardless of the synthesis procedures some iron was always indentified in the processed material showing an incomplete reaction and resulting in a lower hydrogen capacity.…”

“…Some authors suggested that Mg 2 FeH 6 is formed directly from the reaction of 2Mg+Fe+3H 2 [1,2,6,8] , while others reported that the reaction involves two steps: the first one is the formation of MgH 2 , and secondly, the reaction of magnesium hydride with Fe [5,[9][10][11] . Polanski et al 11 using in-situ synchrotron X-ray diffraction showed that MgH 2 is the Mg 2 FeH 6 precursor.…”

Mg2FeH6-based nanocomposites with high capacity of hydrogen storage processed by reactive milling

“…This mechanically activated method can reduce the grain and particles sizes to nanometric scale and improve the hydrogen sorption kinetics of the hydrides 7,8 . The synthesis of the ternary complex hydride, Mg 2 FeH 6 , using ball milling from the stoichiometric compositions 2Mg-Fe or 2MgH 2 -Fe were also studied using different milling conditions [9][10][11][12][13][14][15][16] . Regardless of the milling condition, a remaining iron was always present after milling, which represents an incomplete reaction of hydride formation and results in a lower hydrogen density.…”