High-Resolution TEM Observations of the Decomposition of NaAlH4

Hao Yao; Hiroshi Kawasaki; Shigehito Isobe; Yongming Wang; Naoyuki Hashimoto; Somei Ohnuki

doi:10.2320/matertrans.MBW200902

High-Resolution TEM Observations of the Decomposition of NaAlH₄

Hao Yao, Hiroshi Kawasaki, Shigehito Isobe, Yongming Wang, Naoyuki Hashimoto, Somei Ohnuki

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Keywords: hydrogen storage materials, high-resolution transmission electron microscopy, sodium alanate

JOURNAL FREE ACCESS

2010 Volume 51 Issue 5 Pages 1016-1019

DOI https://doi.org/10.2320/matertrans.MBW200902

View "Advance Publication" version (March 25, 2010).

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Abstract

Sodium alanate (NaAlH₄) was ground in a glove box in inert gas and transferred to a microscope without exposing the samples to air, using a plastic bag method. The results of in-situ electron beam diffraction showed that NaAlH₄ decomposed to Na₃AlH₆ and Al, and then to NaH and Al when heated to 150°C and then 200°C. The decomposition of NaAlH₄ was observed by ex-situ transmission electron microscopy (TEM) at 1250 keV. Porous structures appeared when the samples were heated and dehydrogenated. These are likely due to structural defects or are cavities due to volume changes between phases. The Na₃AlH₆ and Al particles were found to distribute around the pores.

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