Study On The Morphology Control Of Sub-micro Spindle Shaped Calcium Carbonate

Calcium carbonate which has kinds of morphology can be used in different industries. Controllable preparation of functioned superfine calcium carbonate with specific morphology and size distribution has become an attractive research project in material field. The sub-micro spindle shaped calcium carbonate is prepared by three ways in this paper. Factors affecting the morphology of calcium carbonate such as additive amount of crystal control agent, initial carbonation temperature and so on were studied. Futhermore, the shape control mechanism of crystal control agents were discussed.The seeding method mainly includes two parts, which are preparation of seed crystal and sub-micro spindle shaped calcium carbonate. The results show that seed crystals provide the nucleation sites and the CaCO3 crystals grow on the surface of seed crystals. The sub-micron spindle shaped CaCO3 with major axis of 400?600 nm and aspect ratio up to 4 can be prepared at the initial temperature of 30?35? and with seed crystal mass fraction of 20%.The second way to preparation of sub-micro spindle shaped calcium carbonate is carbonation with polyethylene glycol whose molecular weight is 4000 as crystal control agent. The sub-micro spindle shaped calcium carbonate with major axis of 600?1000 nm can be synthesized when the initial carbonation temperature is 25?30?, PEG-4000 mass fraction is 2%. The results show that PEG-4000 plays a crucial role in the formation of CaCO3. Bescause of the long pair electrons on the oxygen atoms of PEG-4000, there is srong electrostatic interaction between PEG-4000 and Ca2+ ions, so PEG-4000 can absorb on the CaCO3 crystals to make the nucleation energy decrease and affect the relative growth rate of crystal faces.The third way to preparation of sub-micro spindle shaped calcium carbonate is carbonation with AlCl3·6H2O as crystal control agent. The sub-micro spindle shaped calcium carbonate whose size can be controlled can be synthesized at the initial temperature of 35? and with AlCl3·6H2O mass fraction of 6%-7%. The additive amount varys with the initial temperature. Aluminium chloride which is added into Ca(OH)2 slurry can promote crystal nucleation because supersaturation increases.