Mechanical synthesis of magnesium alloys for hydrogen storage

Abstract:

In this work, synthesis, characterisation and hydrogen sorption properties of MgH2, Mg-Li alloy, NaMgH3, Li substitution in NaMgH3, Ca-Mg-H, and Li/Na substitution into Ca-Mg-H ternary systems have been investigated. Samples were ball milled under Ar or H2 for 2, 5, 10 or 15 h; then characterized by X-ray diffraction (XRD), Raman Spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis coupled with a mass spectrometer (TGA-MS). The compositional changes and reversibility were investigated using in-situ XRD. The X-ray intensities decreased with increasing milling, which corresponds to a reduction in crystallinity. For the first time, the effect of ball milling on the Raman of MgH2 was studied. For Mg-Li no formation of LiMgH3, Li2MgH4 was observed. NaMgH3 was synthesized after 2 h milling in Ar. DSC-TGA-MS showed H2 desorption occurs in 2 steps with a total mass loss of 5.9 wt. % H2 at 359 °C. Substituting Li in NaMgH3 led to a decrease in desorption temperature of about 50 °C when 0.5 mol (Li) was added. However, the total mass loss was decreased to 5.1 wt % H2. Ca-Mg-H and Li/Na substitutions into the ternary hydride showed desorption temperatures between 300 °C and 385°C with a maximum of 3.5 wt.% H2 released.

Año de publicación:

2018

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