Mechanism of densification of calcium carbonate by cold sintering process

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 degrees 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.

Automated summary

Conventional ceramic sintering cannot harden carbonates easily due to their thermal decomposition, but the cold sintering process (CSP) allows for lower temperature hardening. This study used vaterite phase calcium carbonate as the starting material and found that as the cold sintering temperature increased, the bulk density and compressive strength of the hardened calcium carbonate also increased, with the maximum compressive strength achieved at 80 degrees Celsius.