Ultrasmall Angle X-Ray Scattering (USAXS) studies of morphological changes in NaAlH4

Shathabish NaraseGowda, Scott A. Gold, Jan Ilavsky, Tabbetha A. Dobbins

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

The ultra-small Angle X-Ray Scattering (USAXS) technique has been explored to study morphological changes that occur in the hydrides during various stages of hydrogen release. The power law scattering data from USAXS measurements yield the power law slope (p) which is used as a definitive parameter to study changes in surface fractal dimensions (Ds). Changes in surface area occur due to densification during desorption at elevated temperatures and the rate of those changes are mitigated by the addition of transition metal dopants. For the present study, NaAlH4 was doped with 4 mol% TiCl3 by high energy ball milling and subjected to USAXS measurements to determine the effect of the catalyst. USAXS measurements were also done on NaAlH4 nano-confined within porous alumina membranes. Results showed that the power law slope from USAXS analysis increased from p=-3.6 to p=-3.46 after high energy ball milling; to p=-3.26 after catalyst addition and to p=-3 after heat treatment, indicating an increase in specific surface area accompanying hydrogen release. The particle sizes before and after heat treatment were also evaluated to quantify the extent of densification occurring due to heat treatment. The radius of gyration (Rg) for unmilled NaAlH4 increased from 9.7nm to 26.4nm and a 5 min milled NaAlH4 particle size increased from R g=6nm to Rg=14.5nm. USAXS on nanostructured NaAlH 4 yielded power law slopes of p=-1.41 (rod shaped particles) and p=-2.7 (disc shaped particles) which proved USAXS to be an effective tool to identify the confined particles in porous matrices by virtue of shape.

Original languageEnglish (US)
Title of host publicationMaterials Challenges in Alternative and Renewable Energy, Energy 2010 - A Collection of Papers Presented at the Materials Challenges in Alternative and Renewable Energy Conference
PublisherAmerican Ceramic Society
Pages51-59
Number of pages9
ISBN (Print)9781118016053
DOIs
StatePublished - 2011
Externally publishedYes

Publication series

NameCeramic Transactions
Volume224

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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