| Synthsis of needlelike, chainlike and plate nano calcium carbonate by using stirring carbonation method and crystal control agent to control products morphologies. This paper discussed the influence of parameters such as addition amount of crystal control agent, temperature, Ca(OH)2 solid content of slurry and CO2 gas content on the morphologies and particles size distribution of products. Furthermore, nucleation and growth mechanism of needlelike, chainlike and plate calcium carbonate under acting of crystal control agent were mainly studied.The results indicated, dispersal and narrow particles size distribution calcium carbonate with an average diameter of 35-50 nm can be synthesized using EDTA as crystal control agent at 30℃and CO2 content lower than 25.5%. The addition of EDTA can lead to selective growth of CaCO3 crystal and accelerate the nucleation of CaCO3 crystal. The side face of CaCO3 crystals grew slowly while the tip grew fast leading to the formation of slender needlelike particles network at forepart of carbonation process. A general sideways growth took place with carbonation. Dispersal and narrow particles size distribution calcium carbonate with an average diameter of 27-50 nm can be synthesized using ZnCl2 as crystal control agent at 30℃and CO2 content higher than 33.3%. The reaction product amphoteric Zn(OH)2 can link Ca(OH)2 and CaCO3 composite particles together. These particles tightly linked to form rodlike particles. A general sideways growth took place with carbonation. Finally, the linking power of these particles became smaller to form chainlike particles with particles size increased. Dispersal calcium carbonate with an average diameter of 375 nm can be synthesized with oxalate at 20℃, Ca(OH)2 solid content lower than 0.7mol/L and CO2 content higher than 33.3%. Oxalate can break the crystal lattice of spindle intermediate particles. The particles can grow along a face to form plate structure under acting of tetragonal CaC2O4.
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