Formation of Mullite from Pyrophyllite by Mechanical and Thermal Treatments

Abstract
When pyrophyllite is submitted to mechanical and thermal treatments, significant changes take place, according to XRD and DTA results. With grinding, the DTA endothermic peak is shifted to 540°C and becomes sharper and similar to kaolinite. A sharp exothermic peak is also produced at 1000°C, which is not present in the unground material. Increasing the mullite is associated with the formation of the latter peak. Thermal treatment causes the formation of mullite at higher temperatures.