稳定非晶态CaCO_(3)在乙二醇无水体系中的制备及形成机理

Synthesis and Formation Mechanism of Amorphous CaCO_(3) in Anhydrous Ethylene Glycol

采用醇钙法在乙二醇钙无水体系中制备了纯净且稳定的非晶态CaCO_(3)(ACC),即利用K_(2)CO_(3)和CaCl_(2)在乙二醇溶液中的反应制备ACC,并研究了溶液浓度、陈化温度和时间对产物相类型和颗粒形貌的影响。X射线衍射(XRD)结果表明,当溶液混合后立即有ACC生成;在0℃和20℃的反应温度下,当陈化时间延长至4个月时,产物依然保持非晶态,说明生成的ACC非常稳定;20℃下不同浓度溶液反应得到的产物也为纯净ACC。产物的红外光谱(IR)、透射电镜(TEM)以及选区电子衍射(SAED)结果验证了产物CaCO_(3)为非晶态。扫描电镜(SEM)观察结果表明,反应时间越短、反应温度越低、溶液越稀,ACC越容易呈现疏松多孔状;随着陈化时间的延长,ACC由疏松多孔的无定形态逐渐变成不规则颗粒状(0℃)和较规则的椭球状或球状颗粒(20℃)。最后,从CaCl_(2)和K_(2)CO_(3)在乙二醇中电离的角度探讨了ACC的形成机理。该研究为稳定的纯净ACC的制备提供了全新的途径,有助于进一步加深对ACC调控制备的理解。

Pure and stable amorphous calcium carbonate(ACC)was synthesized by using alcohol-calcium method in anhydrous ethylene glycol,i.e.the reaction between CaCl_(2)and K_(2)CO_(3)ethylene glycol solutions.The effect of solution concentration,aging temperature and time on polymorphs and morphologies of CaCO_(3)was studied.XRD results indicate that ACC is formed upon the mixing of the two solutions.At the reaction temperatures of 0℃and 20℃,the product maintains amorphous even prolonging aging time to 4 months.ACC is the only polymorph in product obtained from different solution concentrations at 20℃.IR spectra,TEM images and SAED patterns verify the formation of ACC.SEM images reveal that the shorter aging time,the lower reaction temperature and the more diluted solution,the more readily for the formation of porous loose ACC.With prolonging aging time to 4 months,porous loose ACC becomes irregular particle at 0℃and relative regular ellipsoidal or near-spherical particle at 20℃.The formation mechanism of ACC was discussed from the viewpoint of the ionization of CaCl_(2)and K_(2)CO_(3)in ethylene glycol.This research extends the route to prepare stable pure ACC and provides new insights into its controllable synthesis.