Synthesis of spherical shape borate-based bioactive glass powders prepared by ultrasonic spray pyrolysis

Spherical shape borate-based bioactive glass powders with fine size were directly prepared by high temperature spray pyrolysis. The powders prepared at temperatures between 1200 and 1400 degrees C had mixed phase with small amounts of fine crystal and an amorphous rich phase. Glass powders with amorphous phase were prepared at a temperature of 1500 degrees C. The mean size of the glass powders prepared by spray pyrolysis was 0.76 mu m. The glass powders prepared at a temperature of 1200 degrees C had two distinct exothermic peaks (T-c1 and T-c2) at temperatures of 588 and 695 degrees C indicating crystallization. The glass transition temperature (T-g) of the powders prepared at a temperature of 1200 degrees C was 480 degrees C. Phase-separated crystalline phases with spherical shape were observed from the surface of the pellet sintered at a temperature of 550 degrees C. Crystallization of the pellet was completely occurred at temperatures of 750 and 800 degrees C. The pellets sintered at temperatures below 700 degrees C had single crystalline phase of CaNa3B5O10. The pellet sintered at a temperature of 800 degrees C had two crystalline phases of CaNa3B5O10 and CaB2O4. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.