Facile synthesis of nanosized sodium magnesium hydride, NaMgH3

The ternary magnesium hydride NaMgH₃ has been synthesised via reactive milling techniques. The method employed neither a reactive H₂ atmosphere nor high pressure sintering or other post-treatment processes. The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio. High purity NaMgH₃ powder (orthorhombic space group Pnma, a=5.437(2) Å, b=7.705(5) Å, c=5.477(2) Å; Z=4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction (PXD), Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). The products formed sub-micron scale (typically 200–400 nm in size) crystallites that were approximately isotropic in shape. The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption (TPD). The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K.