纳米CaCO3的生长和控制机理

应用SEM分析测试技术 ,研究了纳米CaCO3 的生长特征以及反应温度、添加剂及其加入量等因素对CaCO3 晶体形态和粒径的控制机理。结果表明 :纳米CaCO3 晶体的生长过程遵循MLS结晶生长模型 ,随Ca(OH) 2浓度的增加 ,CaCO3 的结晶生长时间延长 ,且由于碳化液粘度的增大而凝并长大 ;反应温度的升高 ,改变了CaCO3的晶面生长速率 ,使CaCO3 粒径增大 ,而且纳米CaCO3 呈现出高面网密度的晶体形态 ;添加剂的作用在于其电离产生的离子进入CaCO3 的晶格位置 ,或选择性地吸附在CaCO3 的晶面上 ,从而改变CaCO3 的表面能 ,因此当添加剂足以包覆CaCO3 晶面的活性部位时 ,增加添加剂量 ,不能继续抑制CaCO3 的生长

Growth characteristics and controlling mechanism of nanometer CaCO3

The growth characteristics of nanometer CaCO 3, the controlling mechanism of temperature, Ca(OH) 2 concentration, additive species and adding amount acting on nanometer CaCO 3 morphology and particle size were investigated by means of SEM. The results show that the growth of nanometer CaCO 3 particles obeys MLS crystal growth model. With the increasing of Ca(OH) 2 concentration, the CaCO 3 crystal growth periods were found to be extended, and the aggregation growth of the nanometer CaCO 3 particles due to the viscosity increase of the carbonation suspension was observed. The rise in reaction temperature may increase the CaCO 3 crystal growth rate causing larger grain radii, also the CaCO 3 crystal can reveal a morphology with higher lattice networking density. The ions produced due to the electroionization of the additive species can occupy the CaCO 3 lattice sites, or be absorbed on CaCO 3 crystal faces, therefore changing the CaCO 3 crystal surface energy. Hence, when the additive amount is large enough to cover active sites on crystal faces, the increasing of additive concentration can not further inhabit crystal growth.