Mechanochemical synthesis of alane

Alane can be synthesized by cryomilling alanate and aluminium halides. The yield of alane has been found to be increased using 3NaAlH4 + AlCl3 and 3LiAlD4 + AlBr3 compared to 3LiAlD4 + AlCl3. Furthermore the relative amount of α′- over α-alane has increased from 0.63–0.67 to 1.05 by adding small amounts of FeF3 to 3LiAlD4 + AlCl3. When synthesized from 3NaAlH4 + AlCl3 the ratio α′/α was also increased to 1.04. α′-AlH3 was confirmed to be less thermally stable than α-AlH3. The maximum amount of synthesized alane was obtained by using NaAlH4 as a starting material instead of Li-alanate. However, the synthesis route from NaAlH4 provided alane with less thermal stability than the synthesis from LiAlD4. The use of Na3AlH6, LiH or TiCl3 resulted in no alane formation.