Preparation And Hydrogen Storage Properties Of New Mg-rich Based Hydrogen Storage Alloys

In this work, we focus on the preparation and hydrogen storage properties of Mg-richMg-Ni-La and Mg-Ni-La/Y-Co system alloys. Firstly, we research the effect of rapidsolidification on phase structure and hydrogen storage properties of Mg60Ni30La10alloyfrom the perspective of two preparation methods. Secondly, we study the effect of Cocontent on phase structure and hydrogen storage properties of Mg60Ni30La10-xCox(x=0,2,4)and Mg60Ni30Y10-xCox(x=2,4) alloys by adding Cobalt. Finally, we research the effect ofRe on phase structure and hydrogen storage properties of Mg90(ReNi3)10(Re=La, Pr, Nd)alloys with high magnesium content.For Mg60Ni30La10alloy, XRD patterns and SEM imagines show that the Mg60Ni30La10alloy contains MgH2and Mg2NiH4phase after hydrogenation of573K and2MPa, whilethe rapid solidification alloy mainly contains La4H12.19phase and the arc melting+mechanical alloying alloy contains La8H18.40phase. From kinetic curves, it can clearly beseen that the rapid solidification alloy shows the maximum hydrogen absorption/desorptioncapacity. However, arc melting+mechanical alloying alloy has the maximum hydrogenabsorption/desorption rate. The dehydrogenation activation energies of Mg60Ni30La10alloyare calculated by Kissinger method, showing the values of99.94±5.15<101.68±8.97kJ/mol for the rapid solidification alloy and the arc melting+mechanical alloying alloy.For Mg60Ni30La10-xCox(x=0,2,4) alloy, after hydrogenation of573K under2MPahydrogen pressure, XRD pattern results indicate the formation of new phases of MgH2(x=0,2,4), Mg2NiH4(x=0,2,4), La4H12.19(x=0,2,4), Mg2Ni0.9Co0.1H4(x=2), Mg2NiH0.26(x=4), Mg2CoH5(x=4). It is observed that the experimental data of hydrogen desorptionkinetics at523K,553K,573K are well fitted with Avrami-Erofeev equation. Based on theresults of Kissinger analysis, dehydrogenation activation energies of these alloys aredetermined to be91.38±2.82kJ/mol (x=0),96.33±5.61kJ/mol (x=2) and78.99±2.98kJ/mol (x=4), which are according with the results of hydrogen desorption kinetics.For Mg60Ni30Y10-xCox(x=2,4) alloy, after hydrogenation of573K under2MPahydrogen pressure, XRD pattern results indicate the formation of new phases of YH3, Co5Yand Mg2Ni0.9Co0.1H4(x=2,4). Based on the results of Kissinger analysis, dehydrogenationactivation energies of these alloys are determined to be80.65±5.49kJ/mol (x=4)>76.66±9.56kJ/mol (x=2), which are according with the results of hydrogen desorption kinetics.It can be seen from the TPD curves that the alloy (x=2) has a lower initial temperature(164.64℃), and the alloy (x=4) has a higher initial temperature of hydrogen, is167.19℃.For Mg90(ReNi3)10(Re=La, Pr, Nd) alloys, XRD patterns and SEM imagines show that the Mg90(LaNi3)10alloy contains LaNi5, LaNi7, Mg and Ni phase. And the Mg90(PrNi3)10alloy contains PrMg2Ni9, Mg and Ni phase and the Mg90(NdNi3)10contains Nd2Ni7, Mgand Ni phase. After hydrogenation Mg90(ReNi3)10alloys contain Mg2NiH4, MgH2andReHx. It can be seen from the TPD curves that Nd element is good at reducing thehydrogen desorption temperature of magnesium-based hydrogen storage alloys, followedby Pr and La element.