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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Abstract

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
DOIs
StatePublished - 1 Oct 2002

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