EFFECT OF SINTERING TEMPERATURE ON THE STRUCTURE AND BIOACTIVITY OF HAp-5.0wt.%SO₂ BIOCERAMIC COMPOSITES

Bioceramic composites were synthesized by sintering the powders of hydroxyapatite (HAp) mixed directly with additive of 5.0wt.%SiO₂ at different temperatures ranging from 800°C to 1200°C. X-ray diffraction analysis indicated that the phase transformation from HAp to tricalcium phosphate (TCP) began to take place as the sintering temperature is as high as 900°C, and the content of TCP phase increased notably with increasing temperature. Microstructural observations demonstrated that a distinctive microstructure featuring crystalline clusters with different sizes surrounded by glassy matrix formed in HAp-5.0wt.%SO₂ bio-composites, as the sintering temperature reached 1100°C. Soaking experiments in a stimulated body fluid revealed that the bio-composites showed a faster bone-like apatite layer growth, namely an enhanced in vitro bioactivity, as the sintering temperature increased, since the increase in sintering temperature promoted the phase transformation from HAp to TCP, which exhibits a higher solubility than HAp.