Thermodynamic model of 45S5 bioglass

Shakhmatkin and Vedishcheva thermodynamic model (SV TDM) of 45S5 bioglass was evaluated at T = 800 K. From 42 considered system components, only 7 components (Na2O & sdot;SiO2, Na2O & sdot;3CaO & sdot;6SiO(2), 3CaO & sdot;2SiO(2), CaO & sdot;SiO2, 9Na(2)O & sdot;6SiO(2)& sdot;2P(2)O(5), 2CaO & sdot;SiO2, and Na2O & sdot;2CaO & sdot;P2O5) were present in significant equilibrium molar amount. The calculated Q-distribution of silicate units (22.6% of Q(3), 63.1% of Q(2), 10.1% of Q(1), and 4.2% of Q(0)) was compared with the Q-distribution for so-called crystalline reference state (6.3% of Q(3), 93.7% of Q(2)). Further, both Q-distributions were compared with the MAS NMR experimental data published by different authors (e.g. 33.3% of Q(3), 54.5% of Q(2), and 12.2% of Q(1), or 17.8% of Q(3), 76.7% of Q(2), and 5.5% of Q(1)). It was concluded that there is no principal difference between SV TDM and MAS NMR distributions of silicate units. Further the Q-distribution of phosphate units was analysed. The CRS resulted in 100% presence of Q(0) units (i.e. PO43-). The SV TDM resulted in significantly broader distribution, i.e. 4.5% of Q(2), 10.4% of Q(1), and 85.1% of Q(0). This distribution is comparable with those obtained by MAS NMR (e.g. 26.7% of Q(1) and 73.3% of Q(0)).