Mullitization of Manganese-Doped Aluminosilicate Diphasic Gel

Diphasic mullite precursor gel was synthesized from inorganic salts of aluminum and silicon. The synthesized gel was characterized by means of chemical analyses, FTIR spectroscopic studies as well as measurement of surface area and bulk density. Manganese dioxide (MnO2) as an additive was mixed with the dried gel in different ratios (w/w) by co-grinding followed by compaction. The compacted masses were sintered at different elevated temperatures. The mullitization process was studied by performing differential thermal analysis (DTA) at four different heating rates and the activation energy for mullitization was calculated in each case, using the Kissinger thermal analysis model. MnO2 lowered the activation energy of the mullitization process. XRD and SEM techniques were used to study the microstructures and phase development in the sintered masses. It was observed that in presence of MnO2, the microstructure of the mullite ceramics was significantly modified, resulting in an enhancement of the mechanical properties of mullite.