Synthesis of CaCO3/graphene composite crystals for ultra-strong structural materials

Composite crystals of calcium carbonate (CaCO3) and graphene with hexagonal plate or ring, dendritic and rhombohedral shapes were synthesized by the hydrothermal reaction of calcium acetate and urea in the presence of graphene oxide (GO) sheets. Their crystal structures were characterized to be vaterite, aragonite and calcite, respectively. In this case, the hydrothermally reduced graphene oxide (rGO) acted as an atom-thick, two-dimensional template for controlling the nucleation and growth of the CaCO3 crystals. The vaterite CaCO3 composite crystals (VCCs) were used as a filler of poly(vinyl alcohol) (PVA) to form a composite with a nacre-like structure. The Young's modulus and tensile strength of PVA/45 wt% VCC were tested to be 34.1 ± 2.5 GPa and 165 ± 6 MPa, respectively.