1H NMR and magnetization measurements of a nanostructured composite material of the Mg 2NiH system synthesized by reactive mechanical grinding

Abstract

1H NMR spectra and magnetization have been measured for a nanostructured Mg 2NiH system. 1H MAS NMR spectra indicate the presence of four phases; α-Mg 2NiH, β-Mg 2NiH 4, α-MgH, and β-MgH 2. Most of the hydrogens are contained in the disordered β-Mg 2NiH 4 phase. Magnetization consists of superparamagnetic and paramagnetic ones. The former has its origin in Ni particles formed during the hydrogenation. The latter is greater than the values of crystalline α-Mg 2NiH, and β-Mg 2NiH 4. 1H NMR line width increases with the decrease in temperature linearly, most of which is of dipolar origin. The hydrogen is more mobile in the disordered β-Mg 2NiH 4 phase than in the crystalline counterpart.