Highlighting of a Single Reaction Path during Reactive Ball Milling of Mg and TM by Quantitative H₂ Gas Sorption Analysis To Form Ternary Complex Hydrides (TM = Fe, Co, Ni)

MgH2 synthesis during reactive mechanical alloying studied by in-situ pressure monitoring

“…This value is considerably shorter than the timescale of 10e20 h observed in the pressure drops during the rest periods. The estimated timescale agrees well with the typical times experimentally observed in a different milling device, with a small chamber but a higher milling energy [16]. Therefore, having discarded gas leaks and gas cooling as causes of pressure drops, we attribute pressure changes to H 2 consumption by MgH 2 formation.…”

“…Gas cooling would be the natural consequence of gas heating during mechanical processing. It has been reported that the temperature of milling chambers and balls can increase noticeably when milling is performed with intermediate or high-energy milling devices [13,16,24]. Several processes contribute to the heating of the milling media: mechanical energy converted into heat, MgH 2 formation reaction, Mg plastic deformation, etc.…”

“…More recently, Doppiu et al have used the same technique to determine the effect of different H 2 pressures on Mg hydriding by RMA [13]. The synthesis of other hydrides has also been followed by pressure measurements: Chen et al and Dunlap et al have studied the hydriding behavior of Ti [12,14], Friedrichs et al have analyzed the reaction of Mn 3 Ti 2 V and Ca with H 2 during RMA [15], and likewise Zhang and coworkers have determined the reaction path leading to the formation of Mg 2 TM (TM ¼ Fe, Co, Ni) complex hydrides [16]. Interestingly, in a few cases it has been mentioned that the hydriding process not only occurs during milling, but also happens throughout the rest periods between milling stages [12,14].…”

Mechanochemistry and hydrogen storage properties of 2Li3N+Mg mixture

“…At a short time of t \ 30 min, the vial temperature increases very fast at the beginning and then equilibrates at about 50°C. The temperature of the hydrogen gas calculated is 14°C higher than the vial temperature as revealed by the calibration experiments [27]. The hydrogen pressure also rises correlatively to the temperature for t \ 30 min.…”

“…The vial was produced by Evicomagnetics, and it can work under H 2 atmosphere up to 15 MPa and was assembled with a blockvalve joint for evacuation and hydrogen filling [26]. In situ hydrogen absorption data on milling were obtained from corrected temperature and pressure in the vial using the Hemmes equation [27,28]. All sample handlings were done in argon-filled and purified glove box with oxygen and nitrogen contents of \0.5 9 10 -6 .…”