HYDROTHERMAL DEGRADATION OF CERAMIC MATERIALS ON THE NATURAL RAW MATERIALS BASE

In this paper is dealt with ageing of ceramics, particularly with structural changes of ceramic materials on the base of natural materials after hydrothermal exposure. Identified structural changes are correlated with physical changes expressed as relative deformation. It is assumed deformation of fired clay-based materials is governed by the rehydroxylation of kaolinite, namely via inner and outer OH-groups, present in clay minerals. Samples from mixtures of clay minerals and calcite and/or dolomite, and from fine kaolinitic clay were prepared. Structural changes during hydrothermal exposures were evaluated by the means of infrared spectroscopy. (27)Al MAS nuclear magnetic resonance was also used for confirmation of change of bonds. Correlation between relative deformation and amount of the specific OH bonds in rehydrated samples was confirmed.