Young's Modulus of Alumina Ceramics During Isothermal Heating

The Young's modulus is studied in dehydroxylated alumina ceramic samples in the solid-state sintering region. The initial composition is 35.5 wt.% of kaolin, 35 wt.% of Al2O3, and 29.5 wt.% of feldspar. Since solid-state sintering and dehydroxylation run simultaneously, the samples are preheated at 490 degrees C for 40 h to reach a complete transformation of kaolinite into metakaolinite. Afterwards, the samples are studied by the modulated force thermomechanical analysis in the isothermal regime at the temperatures 500, 600, 700, 800, 900, 1000, and 1050 degrees C when no liquid phase is created. The Young's modulus is measured for 8 h. For temperatures 500, 600, 700, and 800 degrees C only a small increase (2-8%) of the Young's modulus is observed, and after 4 h the samples became stabilized. On the other hand, for temperatures higher than 1000 degrees C the increase of the Young's modulus continues during the whole time period and reaches over 90 %.