Mechanochemical pretreatment of ammonia borane: A new procedure for sodium amidoborane synthesis

The present work reports a new procedure for solid state synthesis of sodium amidoborane (NaAB) by mechanochemical (MC) reaction between as-received NaH and MC pretreated AB. Ball milling (BM) method was used for this purpose. First, pretreated AB was obtained by BM of as-received AB for 4.5 min. Second, powder of pretreated AB was mixed with as-received NaH and conducted to BM. Milling times were from 0 to 200 min: 5, 10, 30, 50, 100 and 200 min, respectively. By fixing the parameters of the milling conditions, only the influence of milling time on NaAB formation was followed. FTIR and XRD methods are used for analysis of powders after milling. We proved, by MC modification of pure AB, that the reaction rate between AB and NaH could be restricted to the interface between newly formed larger AB and small NaH particles. In such a way we obtained much better control of the reaction system with very accurate determination of reaction steps. Depending on the milling times, reaction process can be separated in three phases: i) 0–30 min phase - reactant and product are present; ii) 50–100 min phase - formed NaAB is almost without other pure; iii) 200 min phase - NaAB is totally decomposed. By this synthesis procedure we produced, for the first time, pure NaAB almost without any impurities.