Multi-scale nacre-inspired lamella-structured Ti-Ta composites with high strength and low modulus for load-bearing orthopedic and dental applications.

Mimicking the hierarchical structure of nacre in artificial materials is a promising approach to obtain high mechanical performance. In this work, nacre-inspired lamella-structured Ti-Ta composites were fabricated by successive spark plasma sintering, mechanical processing and annealing. The specimen sintered at 1200 °C and then hot rolled with 60% height reduction exhibited multi-scale lamellar microstructure. At micro-scale, the composite was composed of alternate Ti-enriched and Ta-enriched micro-bands. At nano-scale, highly-ordered lamellar structures consisted of Ti-enriched and Ta-enriched nano-lamellae were found near Ti/Ta micro-bands. The biomimetic-structured Ti-Ta composite possessed appropriate combination of strength (1030 MPa ultimate tensile strength) and ductility (10.2% elongation), which is much stronger than pure Ti and comparably strong as Ti-6Al-4 V. Moreover, the biomimetic-structured Ti-Ta composite possessed low modulus (80.6 GPa). In vitro cell culture experiment revealed that the biomimetic-structured Ti-Ta composite was cytocompatible, evidenced by the well-spread morphology and favorable growth of human bone mesenchymal stem cells (hBMSCs) on material surface. A rat femoral fracture model was employed to evaluate the therapeutic performance of biomimetic-structured Ti-Ta composite implant on fracture healing compared to that of pure Ti. In vivo results showed that the composite implant enhanced fracture healing in rats. Together, the findings obtained in the current work suggest that mimicking the hierarchical structure of nacre in Ti-Ta composite is an effective way for material strengthening. Moreover, the biomimetic-structured Ti-Ta composite with high strength, good ductility, low modulus and favorable biocompatibility is promising for load-bearing applications in orthopedic and dental area.