9-2-2 Regeneration Technique of Ammonia Borane Using Milling Method

Abstract

Ammonia borane (AB) can be regenerated by using hydrazine and liquid ammonia via intermediate phases of N₂H₄BH₃ and B(NH₂)₃. By an analogy of this method, we have recently reported that AB forms from hexagonal boron nitride (h-BN) by milling under hydrogen pressure and then using hydrazine and ammonia. However, this regeneration mechanism is still unclear. In this work, the reaction pathways of hydrogenated h-BN and B samples with liquid hydrazine-ammonia solution have been investigated in order to understand the key factor for forming AB by using hydrazine and ammonia. As a result, the reaction pathway for the hydrogenated h-BN is similar to that for polyborazirene (PB) since the same intermediates were observed after both the reactions with hydrazine and ammonia. On the other hand, the hydrogenated B was not converted to AB by using hydrazine and ammonia, indicating that existence of N-B-H bonding is necessary to obtain AB by using hydrazine and ammonia.