This paper presents a comparative study of H₂ absorption and desorption in MgH₂ milled with NbF₅ or NbH_0.9. The addition of NbF₅ or NbH_0.9 greatly improves hydriding and dehydriding kinetics. After 80 h of milling the mixture of MgH₂ with 7 mol.% of NbF₅ absorbs 60% of its hydrogen capacity at 250 °C in 30 s, whereas the mixture with 7 mol.% of NbH_0.9 takes up 48%, and MgH₂ milled without additive only absorbs 2%. At the same temperature, hydrogen desorption in the mixture with NbF₅ finishes in 10 min, whereas the mixture with NbH_0.9 only desorbs 50% of its hydrogen content, and MgH₂ without additive practically does not releases hydrogen. The kinetic improvement is attributed to NbH_0.9, a phase observed in the hydrogen cycled MgH₂ + NbF₅ and MgH₂ + NbH_0.9 materials, either hydrided or dehydrided. The better kinetic performance of the NbF₅-added material is attributed to the combination of smaller size and enhanced distribution of NbH_0.9 with more favorable microstructural characteristics. The addition of NbF₅ also produces the formation of Mg(H_xF_1-x)₂ solid solutions that limit the practically achievable hydrogen storage capacity of the material. These undesired effects are discussed.

本文对用NbF ₅或NbH _0.9研磨的MgH ₂中H _2的吸收和解吸进行了比较研究。NbF ₅或NbH _0.9的添加大大改善了氢化和脱水动力学。研磨80小时后，MgH ₂与7摩尔％NbF ₅的混合物在30 s内在250°C下吸收60％的氢容量，而具有7摩尔％NbH _0.9的混合物占48％，并且未添加添加剂而研磨的MgH ₂仅吸收2％。在相同温度下，含NbF ₅的混合物中的氢脱附在10分钟内完成，而含NbH _0.9的混合物中的氢解吸完成。MgH ₂仅解吸其氢含量的50％，而无添加剂的MgH ₂实际上不释放氢。动力学上的改善归因于NbH _0.9，在氢化或脱水的氢循环MgH ₂  + NbF ₅和MgH ₂  + NbH _0.9材料中观察到的相。添加NbF _5的材料具有更好的动力学性能，这归因于较小的尺寸和增强的NbH _0.9分布以及更有利的微观结构特征。NbF _5的添加也会产生Mg（H _x F _1-x）₂固溶体限制了材料实际可实现的储氢能力。讨论了这些不良影响。