Characterization of novel zinc-hydroxyapatite/wollastonite composite synthesized from biowaste for biodegradable orthopedic implant applications

In this study, high-strength zinc composites were fabricated using hydroxyapatite (HA) and wollastonite (WA) recovered from biowastes such as eggshells and rice husk ash for biomedical applications. The objective of this work is to evaluate the impact of hybrid reinforcement (HA and WA) particles on microstructural, mechanical, phase, and corrosion properties of novel Zn-1 Mg-0.2Ti/x(HA-WA) composite (x = 1, 5, and 10 wt.%) by squeeze casting method. XRD and FTIR characterization of the synthesized powders revealed the formation of pure HA phase and WA phase, milled for 10 h and calcined at 1000 °C for 1 h. Density measurement showed that Zn-1 Mg-0.2Ti/10(HA-WA) composite exhibited 25% density reduction compared to Zn-1 Mg-0.2Ti alloy. The hardness of Zn-1 Mg-0.2Ti/5(HA-WA) composite (82 HV) was over two times that of Zn-1 Mg-0.2Ti alloy (39 HV). Furthermore, Zn-1 Mg-0.2Ti/5(HA-WA) composite reported homogeneous distribution of the hybrid reinforcement along the grain boundary and the precipitate formation increased the mechanical properties of the composite. Zn-1 Mg-0.2Ti/5(HA-WA) composite reported the highest compressive strength as 364 MPa, which is comparable with the compressive strength of cortical bone (88–230 MPa). All the composites demonstrated dimples, cleavage planes, and lamellar cleavage facets, indicating a ductile and mixed-mode fracture. Electrochemical corrosion test revealed early passivation in Zn-1 Mg-0.2-Ti/5(HA-WA) composite with lower current density than higher reinforced composites. The proposed zinc composite, having improved microstructural, mechanical, and corrosion properties, may be helpful in various biomedical applications which involve load-bearing capacity and biodegradability, such as orthopedic implants.