Abstract
Green ceramic material is a mixture of 60 wt % of clay, 10 wt % of calcite waste and 30 wt % of the clay fired at 1000°C for 90 min. The clay consists of 83 wt % of phyllosicates. The samples were undergone to XRD analysis, DTA, TGA, TDA and mf-TMA during heating 5°C/min. The mf-TMA was based on the measuring Young’s modulus by resonant method. The samples pass over several changes–release of the physically bounded water, burning of the organic impurities, dehydroxylation of kaolinite and illite, decomposition of calcite and creation of anorthite and mullite. The first visible increasing of Young’s modulus, which runs from room temperature to ~300°C, is a consequence of the release of the physically bounded water from pores, micropores and faces of crystals. In a temperature interval 450–650°C dehydroxylation of kaolinite and illite takes place, then decomposition of calcite runs between ~700 and 900°C. These three processes produce new structures which are mechanically weak because of significant part of micropores. In spite of that, Young’s modulus tends to slightly increase from 500 to 750°C and decreases only in a small extent during heating from 750 to 850°C. Then a steep increase of Young’s modulus values is recorded which can be ascribed to superposition of the solid-state sintering and creation of anortite at ~950°C and mullite above 950°C.
