Detailed investigation of ion exchange in ball-milled LiH + MgB2 system using ultra-high field nuclear magnetic resonance spectroscopy

The present Study with the detailed H-1-Li-6 cross polarization NMR analysis confirms the formation of a ternary compound, (Mg1-xLi2x)B-2, during ball milling of LiH+(1/2)MgB2 at room temperature. The Li-6 sites in (Mg1-xLi2x)B-2 exhibit spinning sidebands (SSBs), whereas the Li-6 sites in LiH do not. The SSBs and the very short spin-lattice relaxation time manifested by Li-6 sites in (Mg1-xLi2x)B-2 indicate that the Li ions in (Mg1-xLi2x)B-2 are located between the layered boron structures and close to Mg ions. The formation of (Mg1-xLi2x)B-2 explains the previous observation that the LiH + (1/2)MgB2 mixture ball-milled effectively has a greatly enhanced hydriding kinetics at temperatures below the melting point of LiBH4. (C) 2009 Elsevier B.V. All rights reserved.