Mechanism of densification of calcium carbonate by cold sintering process

Abstract

In general, carbonates cannot be easily hardened by the conventional ceramic sintering process due to their thermal decomposition during heating. However, when the cold sintering process (CSP) is selected, carbonates can be hardened at lower temperatures. It has been demonstrated that calcium carbonate can be hardened by CSP, but the detailed densification mechanisms of cold sintering at various temperatures have not been fully clarified. In this study, the vaterite phase of calcium carbonate was selected as the starting material. As the cold sintering temperature for calcium carbonate powder increased, the bulk density of the hardened calcium carbonate body increased. The compressive strength was maximized when cold sintered at 80 °C due to the balance between the solubility of calcium carbonate and the reactivity of cold sintering. Almost no crystal phase transformation from vaterite to calcite occurred during cold sintering, and reprecipitation of the vaterite phase though dissolution-precipitation densified the body.