Hierarchical CaCO3 particles self-assembled from metastable vaterite and stable calcite during the decomposition of Ca(HCO3)2

When Ca(HCO₃)₂ solution is put at 80 °C, ACC initially formed grow into calcite, aragonite and vaterite particles. The trunk of snow-shaped particles are self-assembled from hexagonal vaterite particles by one or more steps, followed by the filling in the pores of snow-shaped particles by small crystals.