| Mg2Ni alloy are considered to be one of the most promising materials applied in fuelcell, because of their high hydrogen storage capacity of3.6wt%, however, somedisadvantages such as high hydride-desorption temperatures, poor hydriding anddehydriding kinetics have hindered their business application, therefore, many efforts haveadopt to improves their total hydrogen performances such as Elements substitution andmelt-spinning.The alloys with composition Mg25-xRExNi10（RE=Pr, Y; x=0,1,3,5,7）wereprepared by vacuum induction melting to obtain the as-cast alloy, then the partial cast-alloywere re-melted and spun by melt spinning technique to obtain the as-spun alloy, thespinning rates were chose as15m/s. The phase compositions, surface morphology andcrystal structure were analyzed by XRD, SEM and TEM. The thermal stability of as-spunalloy and hydride-desertion temperatures were analyzed by DSC. Therefore we cancalculate activation energy of alloys during the process of dehydriding. The gas-hydrogenabsorption and PCT curve of alloy were measured by Sieverts apparatus.As-cast Mg25Ni10alloy consist of Mg2Ni phase and Mg phase, and the addition of Prgive rise to the formation of some secondary phase. Mg-Pr-Ni alloy consist of Mg2Niphase、PrMg12and PrNi5phase, Pr addition has improved the hydrogen absorptionkinetics of the Mg2Ni, however, the hydrogen capacities are reduced inevitably. With therising of Pr amount addition, the hydride-desertion temperatures of as-cast Mg-Pr-Ni alloydecreases and activation energy for dehydriding of alloy first declines and then augments,when the amount of Pr addition is five, the activation energy for dehydriding of alloy isminimum value of64.24kJ/mol. The PCT of as-cast alloy have two plateaus，the lowerplateau is related to the formation of MgH2，the higher plateau is related to the formationof Mg2NiH4, the enthalpy of as-cast Mg-Pr-Ni alloy is lower than Mg25Ni10alloy.As-spun Mg-Pr-Ni alloy appears some amorphous phase, therefore, the substitution ofPr facilitates amorphous formation ability of the alloy. Moreover, with the rising of Pr content, the amount of amorphous phase increases，the hydride-desertion temperatures ofas-spun Mg-Pr-Ni alloy decreases and activation energy for dehydriding of alloy firstdeclines and then augments, when the amount of Pr addition is three, the activation energyfor dehydriding of alloy is minimum value of87.48kJ/mol. When the content of Prsubstitution range from1to5, the hydrogen capacities of as-spun alloy is larger than as-cast alloy and absorption kinetics of as-spun alloy is faster than as-cast alloy. The as-spunMg-Pr-Ni alloy exhibit a higher plateaus than as-cast alloy.Mg-Y-Ni alloy consist of Mg2Ni phase and YNi3phase, although the hydrogencapacities decreases with the growing of Y content, the hydrogen absorption kinetics ofalloy improves obviously, moreover, the hydride-desertion temperatures of alloy firstreduces and then increases, when the amount of Y content is three, hydride-desertiontemperatures of alloy is lowest value of209.07℃. The activation energy for dehydridingof alloy first decreases and then augments. When the amount of Y substitution is three, theactivation energy for dehydriding of alloy is minimum value of66.74kJ/mol. The PCT ofas-cast alloy consists of two plateaus, the higher plateau is correspond with Mg2NiH4formation, the lower plateau is correspond with MgH2formation.As-spun Mg-Y-Ni alloy appears some amorphous phase, moreover, with the rising ofY content, the amount of amorphous phase increases，the hydride-desertion temperaturesof as-spun Mg-Y-Ni alloy decreases and activation energy for dehydriding of alloy firstdeclines and then augments, when the amount of Y addition is one, the activation energyfor dehydriding of alloy is minimum value of62.29kJ/mol. Although the as-spun Mg-Y-Ni alloy shows a slower absorption kinetics ability than as-cast alloy, it has largerhydrogen capacities. The as-spun Mg-Y-Ni alloy exhibit a higher plateaus than as-castalloy. |
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