Synthesis, Characterisation and Hydroxy Carbonated Apatite (Hca) Formation Studies on Sol-Gel Derived SiO2-CaO-P2O5, SiO2-CaO-Na2O-P2O5, SiO2-CaO-BaO-Na2OP2O5 Glass Systems

Abstract

58SiO2-(19-x)P2O5-(23+x)CaO (where x=0, 5, 10 and 15 mol %), 58SiO2-(38- x)CaO-xNa2O-4P2O5 (where x=5, 10, 15 and 20 mol %) and 58SiO2-(32-x)BaO-xCao- 6Na2O-4P2O5 (where x=15, 20, 25 and 30 mol %) samples were synthesized using conventional sol-gel method at 700 °C sintering temperature. Thermal and structural properties were studied using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopy. TGA/DTA and XRD analysis confirmed that the variations in crystalline or amorphous nature of synthesized glass samples depended on both onset crystalline temperatures as well as chemical composition. Using Raman spectra non-bridging oxygen concentrations were estimated. The hydroxy carbonated apatite [HCA] layer formation on samples soaked for 7 days in simulated body fluid (SBF) was analyzed. The growth of HCA self assembled layers on the sample surface was discussed as a function of NBO/BO ratio. Results indicated that the number of Ca2+ ions released into SBF solution in the dissolution process and weight loss of SBF treated samples vary with NBO/BO ratio. Transmission electron microscopy (TEM) with selected area electron diffraction (SAED) analysis also confirmed that HCA crystals were formed during SBF treatment. Raman and Infrared spectroscopic analyses have given strong evidence for HCA crystal layer formation through the identification of CO32- and PO43- groups. The changes in NBO/BO ratios were observed to be proportional to HCA forming ability. Among all glass samples, the glass with high CaO concentration (ternary system) shows more HCA forming ability. Calcium phosphosilicate glasses with less concentrations of BaO and Na2O in comparision with CaO favour the HCA formation in tertiary glass system.