Reply to \u2018Comments on \u201cEvidence of the hydrogen release mechanism in bulk MgH2\u201d\u2019

Kazuhiro Nogita,Christopher M Gourlay,Syo Matsumura,Xuan Q Tran,Tomokazu Yamamoto,Stuart D Mcdonald,Kazuhiro Yasuda,Eishi Tanaka

doi:10.1038/srep43720

Abstract

In a comment on our Article “Evidence of the hydrogen release mechanism in bulk MgH2”, Surrey et al. assert that the MgH2 sample we studied was not MgH2 at any time but rather MgO; and that the transformation we observed was the formation of Kirkendall voids due to the outward diffusion of Mg. We address these issues in this reply.

Highlights

Kazuhiro Nogita[1,2], Xuan Q
In a comment on our Article “Evidence of the hydrogen release mechanism in bulk MgH2”, Surrey et al assert that the MgH2 sample we studied was not MgH2 at any time but rather MgO; and that the transformation we observed was the formation of Kirkendall voids due to the outward diffusion of Mg
The question that remains is what was the difference between the samples and observation techniques used by Surrey et al.[1] which made the MgH2 so unstable and the dehydriding reaction so fast as to make observation difficult ? The answer is that we studied large samples a few microns in size that were relatively free of deformation in ultra-high voltage transmission electron microscopy (UHV-TEM) (1,000 kV), while Surrey et al.[1] studied small 100 nm samples that were produced by high-energy ball-milling in low voltage TEM (300 kV)

Summary

Introduction

Kazuhiro Nogita[1,2], Xuan Q. In a comment on our Article “Evidence of the hydrogen release mechanism in bulk MgH2”, Surrey et al assert that the MgH2 sample we studied was not MgH2 at any time but rather MgO; and that the transformation we observed was the formation of Kirkendall voids due to the outward diffusion of Mg. We address these issues in this reply. MgO is most likely to exist in a nanocrystalline form on the outer surface of the bulk specimen under atmospheric exposure and ring patterns would have been found in the SAD instead of diffraction spots (See for example Figure 2 of the comments by Surrey et al.)[1].

Results

Conclusion