Resistive coupled microwave sintering of hydroxyapatite/titania nano-biocomposite and tailoring its mechanical properties

Abstract

Tailoring the mechanical properties of bioceramics plays a crucial role in the fabrication of hard tissue substitutes. In this work, phase pure nanostructured hydroxyapatite and titania were synthesized using a single-step combustion technique. To study the influence of titania in the mechanical properties of hydroxyapatite, hydroxyapatite/titania (TiO2-0%, 10%, 20%, and 30%) nanocomposites were prepared. The sample containing 20% titania showed maximum sinterability and was analysed in detail. The samples were sintered by a novel resistive coupled microwave sintering to 98.9% of the theoretical density at 1020 °C for a soaking duration of 20 min. A substantial reduction in sintering temperature of ∼165 °C and a significantly low soaking duration were observed in the samples sintered using the new technique and it yielded pellets with reduced grain size compared to the samples sintered via conventional resistive heating. They have shown better microhardness of 7.7 GPa, enhanced compressive strength of 194.9 MPa, and improved elastic modulus of 136.2 GPa without compromising the cell viability, cell adhesion, differentiation, proliferation, and biomineralization. The results indicate that by varying the titania content in hydroxyapatite and by adopting a suitable low-temperature sintering strategy like resistive coupled microwave sintering, one can tailor the mechanical properties of bone implants.