Magic angle spinning oxygen-17 NMR of aluminum oxides and hydroxides

Thomas H. Walter, Eric Oldfield

Research output: Contribution to journalArticlepeer-review

Abstract

We have obtained magic angle spinning 17 O nuclear magnetic resonance spectra of 17 O-labeled α-Al 2 O 3 , boehmite (AlO(OH)), bayerite (Al(OH) 3 ), and several transitional aluminas, including γ-, η-, δ-, and θ-Al 2 O 3 . Cross polarization from 1 H to 17 O has been used to enhance the hydroxyl oxygen resonances of boehmite and bayerite and to allow the observation of hydroxyl groups on the surface of γ-Al 2 O 3 . The spectra yield nuclear quadrupole coupling constants, electric field gradient tensor asymmetry parameters, and isotropic chemical shifts for each chemically distinct oxygen site. The quadrupole coupling constants for tetrahedrally coordinated oxide sites (OAl 4 ) range from 1.2 to 2.2 MHz, while those of trigonally coordinated hydroxide sites (Al 2 OH) are in the 5-6-MHz range. Trigonally coordinated oxide sites (OAl 3 ), arising as a result of cation vacancies in the transitional aluminas, are estimated to have quadrupole coupling constants of approximately 4 MHz. It is shown that the observed quadrupole coupling constants and asymmetry parameters are in generally good agreement with the results of electric field gradient calculations based on a point charge model.

Original languageEnglish (US)
Pages (from-to)6744-6751
Number of pages8
JournalJournal of physical chemistry
Volume93
Issue number18
DOIs
StatePublished - Jan 1 1989

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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