Abstract
The renowned mechanical performance of biological ceramics can be attributed to their hierarchical structures, wherein structural features at the nanoscale play a crucial role. However, nanoscale features, such as nanogradients, have rarely been incorporated in biomimetic ceramics because of the challenges in simultaneously controlling the material structure at multiple length scales. Here, we report the fabrication of artificial nacre with graphene oxide nanogradients in its aragonite platelets through a matrix-directed mineralization method. The gradients are formed via the spontaneous accumulation of graphene oxide nanosheets on the surface of the platelets during the mineralization process, which then induces a lateral residual stress field in the platelets. Nanoindentation tests and mercury intrusion porosimetry demonstrate that the material's energy dissipation is enhanced both intrinsically and extrinsically through the compressive stress near the platelet surface. The energy dissipation density reaches 0.159 ± 0.007 nJ/μm(3), and the toughness amplification is superior to that of the most advanced ceramics. Numerical simulations also agree with the finding that the stress field notably contributes to the overall energy dissipation. This work demonstrates that the energy dissipation of biomimetic ceramics can be further increased by integrating design principles spanning multiple scales. This strategy can be readily extended to the combinations of other structural models for the design and fabrication of structural ceramics with customized and optimized performance.