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Abstract:A non-stoichiometric, amorphous a-Mn(BH 4 ) (2x) hydride, accompanied by a NaCl-type salt, was mechanochemically synthesized from the additive-free mixture of (2NaBH 4 + MnCl 2 ), as well as from the mixtures containing the additives of ultrafine filamentary carbonyl nickel (Ni), graphene, and LiNH 2 . It is shown that both graphene and LiNH 2 suppressed the release of B 2 H 6 during thermal gas desorption, with the LiNH 2 additive being the most effective suppressor of B 2 H 6 . During solvent filtration and extraction of additive-free, as well as additive-bearing, (Ni and graphene) samples from diethyl ether (Et 2 O), the amorphous a-Mn(BH 4 ) (2x) hydride transformed into a crystalline c-Mn(BH 4 ) 2 hydride, exhibiting a microstructure containing nanosize crystallites (grains). In contrast, the LiNH 2 additive most likely suppressed the formation of a crystalline c-Mn(BH 4 ) 2 hydride during solvent filtration/extraction. In a differential scanning calorimeter (DSC), the thermal decomposition peaks of both amorphous a-Mn(BH 4 ) (2x) and crystalline c-Mn(BH 4 ) 2 were endothermic for the additive-free samples, as well as the samples with added graphene and Ni. The samples with LiNH 2 exhibited an exothermic DSC decomposition peak.