Smectite clays have been used in various technical applications, particularly in traditional ceramic material, for ensuring the plasticity required for the forming green and simultaneously promote the development of mullite crystals during the firing phase, which confers mechanical strength to the final product. an important innovation over the past decades in the ceramic sector is the use of fast firing, which can induce changes during thermal processing of raw materials and mixtures. to implement changes in firing parameters it is crucial the knowledge of phase transformations of clays, being necessary in some situations the formulation of new compositions. the aim of this work is to analyze the influence of different heat treatments on the mineralogical and microstructural changes of smectites, emphasizing the presence of mullite. two samples of natural bentonite and one imported commercial were used. the natural samples were initially subjected to a milling process. subsequently, they were submitted to chemical analysis by x-ray fluorescence, thermogravimetric and differential thermal analyses. the clays were treated in the 800-1250 °c range with a heating rate 30 °c/min and kept at the maximum temperature for 10 min. the results showed that the clay composition and the temperature have influence on the amount of mullite formed.
smectite; heat treatment; phase transformations; mullite
