Bioprocessing-inspired Water-Mediated Crystallization and Densification of Strong Nacre-Like Aragonite Ceramic from Hydrated Amorphous Precursor

Ceramics are usually obtained by powder sintering at a temperature higher than 1000 °C. By contrast, living organisms can use hydrated amorphous precursors to produce biominerals with high inorganic content and excellent mechanical properties under mild conditions. Here, inspired by the biomineralization process, aragonite ceramic composed of densely packed nanocrystals is manufactured by in situ crystallization and densification of amorphous calcium carbonate (ACC) under pressure at low temperature (80 °C). It is demonstrated that the structural water played critical roles in promoting the fusion of nanoparticles, nucleation of aragonite nanocrystals, and further densification. More importantly, strong nacre-like aragonite ceramic is constructed by introducing cellulose films as the organic layers, where a gradient interface is achieved by water-promoted fusion of nanocrystals into cellulose. Notably, the hardness and Young's modulus of the artificial nacre from nanoindentation can reach 3.76 and 63.38 GPa, respectively, which are comparable to natural nacre. The macroscopic mechanical analysis gave a Vickers hardness of 258.26 Kgf mm −2 and Young's modulus of 5.94 GPa. Besides, the flexural strength and fracture toughness can reach 158.0 MPa and 3.35 MPa m 1/2 , respectively. Thus, the study provides a new bioprocessing-inspired strategy for the fabrication of ceramics with excellent mechanical properties at low temperatures.