Influence of boron substitution on the crystallisation behaviour of tetracalcium phosphate phase in the 4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-5CaO glass system

摘要

This study focuses on the effect of boron substitution on the crystallisation behaviour of an important bioceramic phase, tetracalcium phosphate (TTCP, Ca-4 P2O9), in the 4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-5CaO glass system. The influence of phase separation on the crystallisation activation energy as well as the microstructure is systematically analysed. The results indicate that increasing the extent of substitution of B for Al tends to lead to a decrease of the glass-transition temperature (T-g) and crystallisation temperature (T-p). When the substitution amount of B reaches 15 mol%, phase separation is observed. Weak phase separations during glass making can promote the nucleation of crystals due to heterogeneous nucleation with reduced nucleation activation energy. When 50 mol % B is substituted, serious phase separation is observed, with spherical-shaped TTCP phases appearing in the glass. The growth of striped-shaped TTCP crystals is largely suppressed even when a long holding time (1 h) at 900 degrees C is applied.