Thermal stability and its improvement of the alumina membrane top-layers prepared by sol-gel methods

Y. S. Lin, K. J. de Vries, A. J. Burggraaf

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Abstract

The thermal stability of unsupported alumina membrane top-layers was studied by determining the pore structure (mainly pore size) change of alumina gels, prepared by sol-gel methods, after sintering at different temperatures ranging from 450 to 1200 °C. The average pore size of the pure alumina membranes and PVA-added membranes increased sharply after sintering at temperatures higher than 1000 °C. Addition of 3% lanthanum, either by mixing lanthanum nitrate in the alumina sol or impregnating lanthanum nitrate into calcined alumina gel, followed by a second heat treatment, can considerably stabilize the pore structure of the alumina membrane top-layers. The pore diameter for the lanthanum-doped membranes was stabilized within 25 nm after sintering at 1200 °C for 30 h, about one-sixth of that for the pure alumina membranes after sintering at 1200 °C for 30 h. The substantial increase in the pore size for the pure alumina membranes at the sintering temperature of 1000 to 1200 °C was accompanied by the phase transformation from γ-to α-alumina. The addition of lanthanum can raise this phase transformation temperature by about 200 °C.

Original languageEnglish (US)
Pages (from-to)715-720
Number of pages6
JournalJournal of Materials Science
Volume26
Issue number3
DOIs
StatePublished - Jan 1 1991
Externally publishedYes

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ASJC Scopus subject areas

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

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