Thermal behavior and dimensional stability of clay- and bentonite-based ceramic composites

Clay- and bentonite-based ceramic composites reinforced with 5.6 wt.% SiC or Al ₂ O ₃ were investigated using thermogravimetric and differential scanning calorimetry (TG–DSC) and dilatometry to assess their thermal behavior and dimensional stability. The results revealed distinct thermal responses of the two matrices, with total mass losses of 18.29 wt.% for clay and 10.09 wt.% for bentonite. In the clay matrix, dehydration occurred at approximately 119°C, followed by dehydroxylation between 406 and 708 °C, whereas bentonite exhibited dehydration at 85.8°C and montmorillonite dehydroxylation at approximately 550°C. The addition of SiC or Al ₂ O ₃ did not alter the sequence of the main thermal transformations, causing only minor shifts in characteristic temperatures. Dilatometry showed initial drying shrinkage in clay-based composites and predominantly continuous expansion in bentonite-based composites up to approximately 530°C–560°C. The maximum linear contraction reached 65%, while the maximum linear expansion was 50%. Above approximately 750°C, most mass-changing physicochemical processes were completed. The combined TG–DSC and dilatometric results provide quantitative information for optimizing firing schedules and reducing distortion, cracking, and dimensional inaccuracies during ceramic processing.