Structural and thermal gas desorption properties of metal aluminum amides

Metal aluminum amides for hydrogen storage – Crystal structure studies

“…In the case of KAl(ND 2 ) 4 , the phase transformation from α to β was observed at around 60 °C, and the β-phase disappeared at around 66 °C as shown in Fig.2c. These amorphization temperatures are consistent with ammonia desorption temperatures of metal aluminum amides determined from thermal desorption mass spectroscopy [5].…”

“…S5). The peak positons are in fair agreement with the previously suggested hexagonal unit cell with a = 12.09 and c = 7.968 Å [5]. SR-PXD data gives the unit cell parameters a = 12.08 and c = 7.974 Å and possible space group P6, however, it has not succeeded to solve the structure based on these data.…”

“…The spectrometer was installed in a glove box filled with purified Ar. [4,5] with the expected shift due to the isotope effect when replacing H with D [34]. Amide ions have symmetric and asymmetric stretching modes, which provide two absorption bands in the IR spectra.…”

“…They can thus be regarded as metal alanates where the hydrogen atoms have been substituted by NH 2 . The compounds desorb NH 3 during thermal decomposition and the NH 3 desorption properties have been investigated with temperature-programmed-desorption coupled with a mass spectrometer (TPD-MS), and it reveals that the main NH 3 release occurs in the range 50 -150 °C for M[Al(NH 2 ) 4 ] x (M = Li, Na, K, Mg and Ca) [4,5]. Analogously to the amideimide system [6], NH 3 desorption in metal aluminum amides can be replaced by H 2 desorption by making composites with alkali metal hydrides, therefore the compounds have recently been studied as hydrogen storage materials.…”

A new complex alkali metal aluminium amide borohydride, Li2Al(ND2)4BH4: synthesis, thermal analysis and crystal structure

“…6 It is also reported that an intermediate phase Metal aluminium amide (MAl(NH 2 ) 4 ), are compounds where H  in metal alanate are substituted by NH 2  ions. They desorbs ammonia at around 100 °C for M = Li, Na and K. 9,10 In analogy to the LiNH 2 LiH system, the LiAl(NH 2 ) 4 LiH system has been studied. The ball-milled mixture of LiAl(NH 2 ) 4 +4LiH desorbed >5.0 wt% of H 2 at 130 °C.…”