Thermodynamic model of 45S5 bioglass

Abstract

AbstractShakhmatkin and Vedishcheva thermodynamic model (SV TDM) of 45S5 bioglass was evaluated at T = 800 K. From 42 considered system components, only 7 components (Na2O⋅SiO2, Na2O⋅3CaO⋅6SiO2, 3CaO⋅2SiO2, CaO⋅SiO2, 9Na2O⋅6SiO2⋅2P2O5, 2CaO⋅SiO2, and Na2O⋅2CaO⋅P2O5) were present in significant equilibrium molar amount. The calculated Q-distribution of silicate units (22.6% of Q3, 63.1% of Q2, 10.1% of Q1, and 4.2% of Q0) was compared with the Q-distribution for so-called crystalline reference state (6.3% of Q3, 93.7% of Q2). Further, both Q-distributions were compared with the MAS NMR experimental data published by different authors (e.g. 33.3% of Q3, 54.5% of Q2, and 12.2% of Q1, or 17.8% of Q3, 76.7% of Q2, and 5.5% of Q1). 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 Q0 units (i.e. PO 4 3− ). The SV TDM resulted in significantly broader distribution, i.e. 4.5% of Q2, 10.4% of Q1, and 85.1% of Q0. This distribution is comparable with those obtained by MAS NMR (e.g. 26.7% of Q1 and 73.3% of Q0).