Synthesis, microstructure and mechanical properties of tricalcium phosphate–hydroxyapatite (TCP/HA) composite ceramic

Abstract Tricalcium phosphate-hydroxyapatite (TCP/HA) is an important composite ceramic ubiquitously applied in biomedicine research. In this work, a novel design and synthesizing method for preparation of TCP/HA composites is proposed consisting in suspension mixing amorphous calcium phosphate (ACP) and hydroxyapatite (HA) ceramic powders with different weight ratios, and their compaction under a uniaxial pressure of 200 MPa and sintering at 1150 °C for 2 h. The obtained sintered bodies exhibited optimum hardness and fracture toughness of 5 GPa and 1.27 MPa m1/2, and values significantly improved as compared with those obtained with the traditional mechanical mixing method. The mechanical enhancement mechanism was mainly attributed to the good ACP and HA phase dispersion and ACP crystallization. SEM and HRTEM observations showed the suspension mixing method to allow amorphous spherical ACP and crystalline rod-like HA particles with size around 50 nm to uniformly disperse at the nano scale in the composite powder, which contributes to the excellent sinter ability. Furthermore, XRD results indicate that after sintering, nearly 100% of amorphous spherical ACP transformed to the crystalline β-TCP, which results in the nanoparticle shrinkage, porosity reduction and composite densification.