Effect of Hydroxyapatite on Sinterability, Mechanical Properties, and Bioactivity of Chemically Synthesized Alumina–Zirconia Composites

This work focuses on fabrication of 80 alumina/(20-x)zirconia/xHA (x = 0.0. 5.0, 10.0 and 15 wt.%) composites. Alumina, zirconia and hydroxyapatite powders were synthesized separately by sol-gel method, then mixed and sintered at different temperatures. The obtained ceramic composites were investigated by x-ray diffraction (XRD), water displacement method, and scanning electron microscope. The compressive strength, pore size distribution, bioactivity and antibacterial were also investigated. The results indicated that high-porosity composites were obtained after sintering. With increasing hydroxyapatite content, the composites sintered at 1600 °C exhibited the lowest porosity (33.92–39.92%) and highest bulk density (2.75–2.42 g/cm³) as compared to that sintered at 1500 and 1700 °C. The addition of HA led to reduction of bulk density and increasing the apparent porosity. After sintering, the phases of alumina, monoclinic zirconia, tetragonal zirconia, tri-calcium phosphate and calcium aluminate appear in XRD patterns. The highest compressive strength was obtained for the composites sintered at 1600 °C; their values were 75.88, 74.57, 72.17, and 68.17 MPa for the composites that contained 0.0, 5, 10, and 15 HA, respectively. The bioactivity of composites sintered at 1600 °C increased with increasing HA content. The antibacterial activity against E. coli and Staphylococcus aureus was improved with increasing the HA content in the composites.