Mechanochemical synthesis of NaBH 4 starting from NaH–MgB 2 reactive hydride composite system

The present investigation focuses on a new synthesis route of NaBH 4 starting from the 2NaH + MgB 2 system subjected to mechanochemical activation under reactive hydrogen atmosphere. The milling process was carried out under two different hydrogen pressures (1 and 120 bar) with two different rotation speeds (300 and 550 rpm). The reaction products were characterized by ex-situ solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR), ex-situ X-ray powder diffraction (XRPD) and Infrared Spectroscopy (IR). From the results of these analyses, it can be concluded that milling in all the considered conditions led to the formation of NaBH 4 (cubic- Fm - 3m ). In particular, a reaction yield of 5 and 14 wt% is obtained after 20 h of milling at 120 bar of H 2 for the tests performed at 300 rpm and 550 rpm, respectively. The presence of MgH 2 is also detected among the final products on the as milled powders. The influence of the milling conditions and the evaluation of the parameters related the mechanochemical process are here discussed.