Mechanical activation of the decomposition and sintering of kyanite

Joaquín Aguilar-Santillán, Ricardo Cuenca-Alvarez, Heberto Balmori-Ramírez, Richard C. Bradt

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The influence of attrition milling on the thermal decomposition of kyanite (Al 2O 3·SiO 2) to mullite (3Al 2O 3·2SiO 2) and SiO 2, and its subsequent sintering, was studied. A commercial kyanite was attrition-milled for times up to 12 h. Dilatometry confirmed that as-received unmilled kyanite decomposes between 1300° and 1435°C. The decomposition reaction is slow initially and accelerates during the later stages until about one-half of the decomposition occurs in the last 35°C. For the attrition-milled kyanite, the onset decomposition temperature decreases, the transformation temperature interval is reduced, and both the decomposition reaction and subsequent sintering are accelerated. A dense microstructure of fine equiaxed mullite grains in the 1 μm size range, evenly dispersed in a glassy matrix, is obtained by sintering the attrition-milled kyanites. These results are explained in terms of the energy accumulated during attrition milling, a reduction of the milled kyanite particle size, and the presence of a liquid phase during sintering.
Original languageAmerican English
Pages (from-to)2425-2431
Number of pages2181
JournalJournal of the American Ceramic Society
StatePublished - 1 Oct 2002


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