Microstructural characteristics and long-term stability of wollastonite-based chemically bonded phosphate ceramics

The microstructure of a wollastonite chemically bonded phosphate ceramic (WCPC) and its long-term stability can be characterized in terms of functions over time and at intermediate temperatures (RT, 40°C, 60°C, and 80°C). As seen through SEM images and EDX analysis, the ceramic microstructure comprises brushite, wollastonite and an amorphous heterogeneous phase. Electron backscatter diffraction (EBSD) mapping shows the amorphous phase in this chemically bonded phosphate ceramic to have a uniform distribution of Ca and P elements. The transformation of brushite and the amorphous matrix in its solid state to a more stable CaP phase takes place over a long period. The mechanical performance of the ceramic is therefore improved by thermal aging. Chemical changes are accompanied by denser, more stable phases leading to increased stiffness. The primary disadvantage associated with using this new material in construction would be its relatively high shrinkage as a result of chemical and physical factors.