Solid state phase transformations in LiAlH4 during high-energy ball-milling

Abstract

Mechanochemical processing of polycrystalline LiAlH revealed good stability of this complex aluminohydride during high-energy 4 ball-milling in a helium atmosphere for up to 35 h. The decomposition of lithium aluminohydride into Li AlH , Al and H is observed 3 6 2 during prolonged mechanochemical treatment for up to 110 h and is most likely associated with the catalytic effect of a vial material, iron, which is introduced into the hydride as a contaminant during mechanical treatment.

On the Reversibility of Hydrogen Storage in Novel Complex Hydrides

“…Hence, neither Li nor Mg exhibit any reversibility under conditions that cause the Na system to easily rehydrogenate, even after 5 cycles. It is noteworthy that the Li system appears to be stable when doped and ball milled, which is somewhat contrary to that reported elsewhere (Balema et al, 2000;. The Li system is also not reversible at the conditions where reversibility was thought to occur, but probably did not (Chen et al, (2001).…”

“…Increasing the dopant level further to 2 mole% Ti yields an initial decomposition temperature similar to that obtained for the sample doped with 0.5 mole% Ti; however, the overall dehydrogenation temperature is lowered substantially by about 25 o C. The Ti dopant also affects the first reaction more than the second reaction, similarly to the NaAlH 4 system. Contrary to information published in the literature (Balema et al, 2000;, the stability of the LiALH 4 system, whether doped or not, does not seem to be a major issue. Note that when LiAlH 4 is doped with 2 mole% Ti, it releases 3 wt % hydrogen before 100 o C is reached.…”

“…Nevertheless, this performance level makes it one of the highest capacity, hydride based, hydrogen storage materials known (Sandrock and Thomas, 2001). This very favorable result has also sparked considerable interest in other complex hydride materials, especially LiAlH 4 (Chen et al, 2001;Balema et al, 2000; and Mg(AlH 4 ) 2 (Fichtner and Fuhr, 2002 …”

Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles

“…In the XRD spectra of the as-milled LiAlH 4 all diffraction peaks correspond to the LiAlH 4 phase, without any additional decomposition products, suggesting that pure LiAlH 4 remains rather stable during the ball milling process. [13][14][15][16]18,40,43,57,58 This point can also be proven by the nonisothermal dehydrogenation properties of the as-received and as-milled LiAlH 4 (Fig. 1), and the FTIR spectra of the as-milled LiAlH 4 (Fig.…”

Carbon Nanomaterials as Catalysts for Hydrogen Uptake and Release in NaAlH4

“…However, ball milling is known to degrade fragile carbon nanostructures (15,16)and is known to introduce Fe contamination from the ball mill vial and/or balls (17,18), and Fe is an excellent catalyst for dehydrogenation of NaAlH 4 (19). When studying carbon materials as catalysts for NaAlH 4 , care must be taken in the preparation of samples.…”