Journal of Materials Science, Vol.52, No.15, 9202-9210, 2017
Fabrication of bioinspired structured glass-ceramics with enhanced fracture toughness
Nature has the amazing ability to evolve materials with combined strength and toughness that far exceed those of their individual constituents. This study aims to develop a bioceramic that mimics the hierarchical organisation of the structure of nacre on multiple scale levels by using a widespread ceramics processing technique and bioactive components. We synthesised hexagonal-shaped platelets of beta-tricalcium phosphate (beta-TCP) with high aspect ratio (diagonal length of similar to 800 nm and thickness of similar to 150 nm) to mimic the aragonite (CaCO3) platelets in nacre. Bioactive glass nanoparticles (BGn, median size of 50 nm) with composition (mol%) of: B2O3 9.98, SiO2 49.02, CaO 39.64, P2O5 1.54 were fabricated to mimic bridges and asperities on the surface of platelets in nacre. Hierarchically organised structures were achieved by freeze-casting of a suspension containing beta-TCP platelets and various concentrations of BGn in a custom-designed mould by adjusting the casting parameters. Results demonstrated successful self-organisation of all structural features during the freezing stage, including local alignment of platelets and entrapment of BGn between the platelets. The most significant mechanical results were obtained for nacre-structured beta-TCP/5 wt% BGn sintered at an unconventionally low temperature (900 degrees C), which showed an indentation fracture toughness of 1.6 MPa m(1/2), compared to reported values of 0.3-1.1 MPa m(1/2) for beta-TCP sintered at 1100-1300 degrees C, as well as other conventional bioceramics and glasses.