SEM and TEM characterization of magnesium hydride catalyzed with Ni nano-particle or Nb₂O₅

The microstructures of MgH₂ catalyzed with Ni nano-particle or Nb₂O₅ mesoporous powders are examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. For MgH₂ catalyzed with Ni, the Ni particles with the diameter smaller than 1 μm were detected on the MgH₂ particles with the diameter smaller than 5 μm by the back scattering electron (BSE) microscopy. In details, the TEM micrograph indicates that the Ni particles distribute ∼20 nm in diameter on MgH₂ uniformly, which was the same size as the additive doped in MgH₂ before milling. On the other hand, for MgH₂ catalyzed with Nb₂O₅, the additive particles could not be found anywhere in the BSE image. Even in the TEM micrograph by much larger magnification than the SEM micrograph, the particles corresponding to the additive cannot be observed at all. Furthermore, an energy dispersive X-ray (EDX) analysis in spots with a diameter of 20 nm indicated that the existing ratio of Mg to Nb was evaluated to 98:2, being the same as the starting ratio before milling. Therefore, the metal oxide Nb₂O₅ becomes extremely small particle that could not be observed by the present work after milling compared to metal Ni^nano.