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Hybrid Gels Designed for Mullite Nucleation and Crystallization Control
Published online by Cambridge University Press: 28 February 2011
Abstract
The controlled nucleation of phase transformations by seeding is an established technique for influencing transformation kinetics and sintered microstructures in ceramics. Previous studies have focused on seeding with ultrafine, solid particles having the requisite crystal characteristics for either homo- or heteroepitactic nucleation of the desired phase. Size separation of particulate seed crystals is not an efficient process and thus more recent efforts have concentrated on chemical approaches to nucleating solid phase transformations. Hybrid gels, in which two or more gels are combined to capitalize on the benefits of each, have been reported for the homoepitactic nucleation of mullite. In principle, the molecularly-mixed gel crystallizes to mullite at ∼1000°C and, in turn, acts to nucleate the colloidal gel component's transformation to mullite at higher temperatures. However, the transformation sequence and kinetics are profoundly affected by the interfacial reaction between the two gels comprising the hybrid. This paper discusses how the physical distribution and chemistry of the gel components can be manipulated for the control of mullite nucleation, crystallization and microstructure development.
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- Copyright © Materials Research Society 1990
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