Reactivity features of original sol-gel-derived 52S4 glass versus heat treatment temperature

This work is devoted to study the reactivity of the quaternary glass 52S4 (52% SiO2-30% CaO-14% Na2O-4% P2O5 (wt%)), synthesized by sol-gel process versus the treatment temperature. The dried gel was heat treated at 600 and 650 degrees C and soaked in simulated body fluid (SBF). XRD results confirm the amorphous character of glass treated at 600 degrees C even though the heat treatment at 650 degrees C induces Na2Ca2Si3O9 formation. After soaking in SBF, SEM and EDS results show the formation of carbonated hydroxyapatite (CHA) at the glass surface for both temperatures. For the glasses treated at 600 and 650 degrees C, two phenomena were observed: the glass dissolution in SBF and the CHA precipitation, but the reactivity kinetics of glass was different when temperature changes. For SGDG600, the CHA began to crystallize after 16h. For SGDG650, a glass ceramic made of a glassy matrix and of Na2Ca2Si3O9, the crystallized carbonated HA was observed after 2h. In addition, a new crystallization at the glass surface of Na2Ca2Si3O9 was observed after 15days.