Kaolinite to Mullite Reaction Sequence

When heated, kaolinite undergoes a complex series of chemical and physical changes that transform the layered mineral to a combination of crystalline mullite and an amor­phous siliceous phase. Though simple conceptually, the study of this reaction sequence

Kaolinite to Mullite Reaction Sequence

Fig. 12 Schematic representation of the build up of a cast layer (wall) from a suspension of clay particles (slip) in contact with a gypsum(hydrated plaster of Paris) mold (reproduced by permission of Addison-Wesley from F. H. Norton, Elements of Ceramics, Addison-Wesley Publishing, Reading, MA, 1952) [22]

continues to draw interest from the materials research community due to on-going con­troversies related to the composition and structure of the intermediate phases. Notable studies of the reaction of clays during heating have been conducted by LeChatelier [32], Brindley [33], and MacKenzie [34]. In an interesting parallel to the connection between the processing of clay-based ceramics and advanced processing methods, the characteri­zation protocols used in modern ceramic science draw heavily on the work of these authors who were among the first in the field of materials to apply characterization techniques that are now considered routine. LeChatelier used thermal analysis, Brindley employed a combination of transmission electron microscopy and diffraction, and MacKenzie made use of nuclear magnetic resonance spectroscopy.