Strengthening calcite ceramics via cold-sintering silica nanoparticle-encapsulated caco3 microspheres inducing lattice distortion

Biological mineralized tissues exhibit exceptional mechanical robustness by incorporating nanoscale inclusions, which enhance toughness by inducing crack deflection through either reversible deformation or local compressive stress. Inspired by these design principles, high-performance calcite ceramics are fabricated by cold sintering of SiO 2 nanoparticles-encapsulated CaCO 3 microspheres. The microspheres are assembled through particle attachment of radially oriented vaterite nanoparticles, enabling efficient encapsulation of SiO 2 nanoparticles within the microspherical architecture. Assisted by cold sintering process (CSP) at 250 °C and 700 MPa, the densified CaCO 3 ceramic containing 2 wt% SiO 2 achieves optimal mechanical properties: a Vickers hardness of 3.0 GPa and a flexural strength of 105.5 MPa, 1.7 and 1.5 times improvements over the control groups, respectively. It demonstrates that the strong interfacial interactions between SiO 2 nanoparticles and calcium carbonate matrices induce a 0.49 % contraction in the (104) interplanar spacing of calcite, generating compressive stress that impedes crack propagation and improves deformation resistance. Furthermore, the prestressed ceramics exhibit a 20 % increase of fracture toughness, and a 38 % enhancement of dynamic impact resistance relative to the control group. Learning from the biomineralization process could effectively guide the development of prestress-reinforced artificial ceramics under low-temperature and low-energy conditions.