Nanostructured thin palladium-silver membranes: Effects of grain size on gas permeation properties

B. A. Mccool, Y. S. Lin

Research output: Contribution to journalArticle

80 Scopus citations

Abstract

Submicron-thick Pd-Ag alloy membranes, prepared on 4 nm pore γ-alumina support by magnetron sputter deposition, are nanocrystalline with a grain (crystallite) size of about 20 nm. The membranes show good selectivity for hydrogen over helium (about 4000 at 300°C). Hydrogen permeation is dominated by the surface reaction steps in 100-200°C with an activation energy of about 30 k J/mol. Bulk diffusion resistance becomes important at higher temperatures (>200 °C). Grain size is the most critical parameter affecting the hydrogen permeance of the thin nanostructured Pd-Ag membranes. Increase in Pd-Ag grain size from about 20 to 60 nm results in a substantial improvement in hydrogen permeance with a higher apparent activation energy in 100-300°C. Grain growth appears to increase the hydrogen permeability in the bulk phase of the Pd-Ag membranes. Helium permeance through the grain boundary decreases with increasing temperature or hydrogen partial pressure due to grain expansion. Carbonat ion and the accompanied grain expansion have detrimental effects on the perm-selectivity of the Pd-Ag membranes.

Original languageEnglish (US)
Pages (from-to)3221-3227
Number of pages7
JournalJournal of Materials Science
Volume36
Issue number13
DOIs
StatePublished - Jul 1 2001
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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