Composites matching the properties of human cortical bones: The design of porous titanium-zirconia (Ti-ZrO2) nanocomposites using polymethyl methacrylate powders

Bone-like low elastic modulus micro-porous titanium (Ti) and titanium-zirconia (Ti-ZrO2) nanocomposites were fabricated by a pressureless sintering process with biocompatible polymethyl methacrylate (PMMA) powders as the pore-forming agents. A microstructural analysis revealed that the method can successfully make randomly distributed pores in the sintered monolithic and nanocomposite, and the pore-forming agents can be removed by a heat treatment process. The material properties, i.e., the relative density, pore morphology, microhardness and elastic modulus, can be dramatically altered with the pore-forming agent. Moreover, the porous Ti-based nanocomposites produced in this way (50 vol% PMMA) have interconnected pores, higher biocompatibility, better mechanical properties and well controlled the Ti grain size, when compared with the monolithic porous Ti bodies through the second phase strengthening mechanism. The elastic moduli of the highly porous monolithic Ti and Ti-ZrO2 nanocomposites can be controlled to be about 20.0 and 22.4 GPa, respectively, which are almost the same as human cortical bones (7-25 GPa).