Effect of mechanochemical activation on the thermal reactions of boehmite (gamma-AlOOH) and gamma-Al2O3
UNSPECIFIED. (2000) Effect of mechanochemical activation on the thermal reactions of boehmite (gamma-AlOOH) and gamma-Al2O3. THERMOCHIMICA ACTA, 359 (1). pp. 87-94. ISSN 0040-6031Full text not available from this repository.
Boehmite (gamma-AlOOH) and gamma-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 Al-27 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 degrees C via gamma-Al2O3, by contrast with the unground control, which forms corundum at 1195 degrees C via gamma and delta-Al2O3. Grinding gamma-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 degrees C, compared with 1193 degrees C in the unground material which transforms via delta-Al2O3, The relationship between the mechanochemical development of the 36 ppm Al-27 NMR resonance in aluminas and their hydroxyl and adsorbed water content is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Journal or Publication Title:||THERMOCHIMICA ACTA|
|Publisher:||ELSEVIER SCIENCE BV|
|Date:||21 August 2000|
|Number of Pages:||8|
|Page Range:||pp. 87-94|
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