Effect of mechanochemical activation on the thermal reactions of boehmite (γ-AlOOH) and γ-Al2O3

K. J.D. MacKenzie, J. Temuujin, M. E. Smith, P. Angerer, Y. Kameshima

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Abstract

Boehmite (γ-AlOOH) and γ-Al2O3 were ground for 60 min and the changes in their structure and thermal reactions were monitored by X-ray powder diffraction, thermal analysis and 27Al MAS NMR. Grinding does not cause the boehmite to dehydrate, but causes a decrease in the intensity of its X-ray reflections, and the formation of an amorphous phase containing tetrahedral Al and another Al site with a resonance at 36 ppm (sometimes attributed to pentacoordinated Al). The ground material thermally transforms to corundum at 940°C via γ-Al2O3, by contrast with the unground control, which forms corundum at 1195°C via γ and δ-Al2O3. Grinding γ-Al2O3 decreases the intensity of its X-ray reflections and induces the formation of some corundum without further heating. Complete transformation to corundum occurs at 927°C, compared with 1193°C in the unground material which transforms via δ-Al2O3. The relationship between the mechanochemical development of the 36 ppm 27Al NMR resonance in aluminas and their hydroxyl and adsorbed water content is discussed. ũ 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)87-94
Number of pages8
JournalThermochimica Acta
Volume359
Issue number1
DOIs
Publication statusPublished - Aug 21 2000
Externally publishedYes

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Keywords

  • Alumina
  • Mechanochemical activation
  • Thermal reactions

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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