Effect of Additives on Polymorphs and Morphologies of CaCO₃ Powder via High-energy Milling Method

Due to its low thermodynamic stability, it is difficult to synthesize vaterite phase of CaCO₃. The effect of milling time, milling speed and the weight ratio of milling ball to reactant on the polymorphs and the morphologies of CaCO₃, in absence of NaCl or KCl as diluter, was firstly studied. Amorphous CaCO₃ (ACC) was formed at the early reaction stage and at low milling speeds, while otherewise calcite is the only phase. Prolonging milling time, enhancing milling speed and increasing the weight ratio of milling ball to reactant are beneficial to the formation and crystallization of calcite. The effect of sodium dodecyl sulfonate (SDSN) and sodium hexametaphosphate (SHMP) on the polymorphs and the morphologies of CaCO₃ was then evaluated, indicating that both SHMP and SDSN can promote the formation of vaterite. The percentages of vaterite phase are 58.2 wt.% and 81.9 wt.%, when using SDSN and SHMP respectively.