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Evolution Mechanism of Calcium Carbonate in Solution
郭亚平*1,2,3, 唐海雄2, 周玉2, 贾德昌2, 宁聪琴4, 郭亚军1
1.Department of Chemistry, Shanghai Normal University, Shanghai 200234, China;2.Institute for Advance Ceramics, Harbin Institute of Technology, Harbin 150001, China;3.State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Insti;4.State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
Abstract:
Calcium carbonate was synthesized in a CaCl2/NaCO3 mixed solution by using ethylenedi-aminetetraacetic acid (EDTA) as an additive. The thermodynamics and kinetics analyses indicate that although the driving force of amorphous calcium carbonate (ACC) precipi-tation is always less than that of calcite and vaterite precipitation, the nucleation rate of ACC is greater than that of calcite and vaterite at the initial stage of the precipitation reaction. With the increasing incubation time, vaterite and calcite particles nucleate het-erogeneously by using the as-formed particles as active sites. Scanning electron microscopy images indicate that the transformation mechanism of ACC and vaterite to calcite is the dissolution-recrystallisation reaction. The presence of EDTA not only improves the stabil-ities of ACC and vaterite, but also leads to forming enlongated, connected rhombohedral calcite crystals after incubation 7 days in solutions. The ACC and vaterite are stabler in air than in solutions at room temperature, although the dissolution-recrystallisation reaction occurs on the surface.
Key words:  Calcium carbonate, Dissolution-recrysatllisation reaction, Phase transition
FundProject:
碳酸钙在溶液中的演化机理
Ya-ping Guo*,Hai-xiong Tang,Yu Zhou,De-chang Jia,Cong-qin Ning,Ya-jun Guo
1.上海师范大学化学系,上海200234;2.哈尔滨工业大学特种陶瓷研究所,哈尔滨150001;3.中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室,上海20050
摘要:
以EDTA作为添加剂,在CaCl2/NaCO3混合液中采用共沉淀法制备了碳酸钙,并探讨它在母液中的演化机理. 热力学和动力学计 算表明虽然形成无定形碳酸钙(ACC)的驱动力小于方解石和球霰石,但在共沉淀反应的初始阶段ACC的形核速率高于方解石和球霰石. 随着陈化时间的延长,最新生成的碳酸钙成为球霰石和方解石异相形核的活性点. 通过SEM发现ACC和球霰石在母液中通过溶解-再结晶机理转化成方解石. 此外,EDTA添加剂不仅提高了ACC和球霰石的稳定性,而且有助于碳酸钙在母液中陈化7天后转化成长棒状、菱形的方解石晶体. 如果将碳酸钙放置在空气介质中,ACC和球霰石也可以通过溶解-再结晶反应转化成方解石,但其转化速率低于溶液介质.
关键词:  碳酸钙,溶解-再结晶反应,相变
DOI:10.1088/1674-0068/23/06/731-737
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