Growth Control of Ultrafine CaCO_3

The ultrafine CaCO3 crystal growth controlled by Na5P3O10 in the carbonation of Ca(OH)2 suspension, was investigated by using SEM. The results show that CaCO3 nucleates along with the nucleus growth. The presence of Na5P3O10 accelerates the CaCO3 nucleation. At the initial stage, a large number of CaCO3 nucleus engender, and metastable tiny crystallites (R= 23-26nm) can be observed in SEM imagine. The CaCO3 crystal growth controlled by short distance diffusion when mass pass through the crystal interface, does not correspond to ZenerHam theory. At the next stage, the metastable tiny crystallites disappear in SEM imagine. The CaCO3 crystal growth abides by the long distance control model R(t)=(Dt)n, in which the time coefficient n is 0.4874-0.4992 (theory value n=0.5) and the constant Dn decreases from 16.69 to 11.36. Consequently, Na5P3O10 can effectively inhabit the CaCO3 crystal growth.