Effect of mullite–zircon addition on sintering and mechanical properties of hydroxyapatite

Hydroxyapatite (HAp) is used as a biomaterial especially as a coating material on the metallic substrates to take the advantages of both excellent biocompatibility of hydroxyapatite and good mechanical properties of the metals as well. However, the mechanical properties of HAp is not adequate and it can be improved by adding various reinforcement materials. In this study, HAp was reinforced with −25 μm mullite–zircon (3Al2 O3 ·2SiO2 –ZrSiO4 ) in different ranges from 0 up to 10 wt% and cylindrical samples were produced by uniaxial dry pressing at 10 MPa. After drying of samples at 110 °C for overnight sintering was performed at 1300 °C for 5 h in air to see the effects of various reinforcement percentages on the development of microstructure, mechanical and physical properties. Mechanical property of all samples were investigated by microhardness measurements. Physical properties was also measured involving bulk density, apparent porosity, weight and volumetric changes. XRD analysis was also conducted after sintering to identify reaction products formed and finally optical microstructural examination was also performed. Improvement of mechanical properties of HAp was observed after sintering. As the amount of reinforcement rises particularly after 4 wt% addition up to 10 wt%, density and hardness values increase leading to microstructural development and improvement.