Behavior and characteristics of amorphous calcium carbonate and calcite using CaCO3 film synthesis

The synthesis of a large area calciumcarbonate (CaCO3) film was carried out under room temperature and atmospheric pressure. The crystallographic, thermal, and mechanical properties of amorphous calcium carbonate (ACC) and calcite obtained from CaCO3 film synthesis were analyzed. Calcium carbonate through the film synthesis initially consisted mainly of ACC and then consisted mainly of calcite as the holding time increased. Morphologically, an increase in blade shaped calcite from hemispherical ACC was observed as the holding time increased. Analysis of the thermal properties showed that when a short reaction holding time was maintained the decomposition temperature of CaCO3 was 680 +/- 2 degrees C, whereas with increased reaction holding time, the decomposition temperature of the calcium carbonate approached 755 degrees C. The nanoindentation analysis showed that the calcite present in the calcium carbonate film had hardness of approximately 5-5.5 GPa, while the ACC had an average hardness of approximately 0.75GPa. For the combined elastic modulus, the value was approximately 59-60 GPa for calcite and approximately 25-30 GPa for the ACC. (C) 2016 Elsevier Ltd. All rights reserved.