Experimental Research Of Calcium Carbonate Crystal Growth In Gels

Because mineral crystallization is regulated by the organic matrix excreted by the biology, and organic matrix can induce the inorganic materials to crystallize and grow, the biomineralization is quite different from the common mineral crystallization in nature. It is generally accepted that the control of organic matrix over crystal growth, morphology and polymorphism is due to the molecular recognition between organic-inorganic interfaces, by which the organic matrix can act on crystal selectively.Calcium carbonate is one of the most important inorganic minerals and used in many fields. However, being a biomaterial, calcium carbonate receives considerable interest from many branches of science just in recent years. Its properties are controlled by the composite character and in particular the morphology of calcium carbonate. The researches on biomineralization will provide new pathways to study the mechanism of biogenic calcium carbonate and to fabricate advanced organic-inorganic composite calcium carbonate. In the thesis, calcium carbonate crystals grew in agarose gels or silicon gels by gel method, equally further knowledge about growth morphology and mechanism of calcite crystals can be obtained by AFM investigations, which is useful to guide the practical crystal growth process.In the thesis, agarose gels are mainly used to regulate and control the growth progress of calcium carbonate crystals under present conditions. In our experiments, versatile morphologies, diverse nucleation amount and different polymorphs of calcium carbonate crystals are grown by changing experience parameters, such as reactants concentration, pH of gels, gels concentration, temperature and Na +. Especially, the crystals grown in agarose gels and in silicon gels differ in many ways. Meanwhile, the mechanisms of these results and the gel method are investigated. The experimental results provide authentic theory to improve gel method.The research utilizes AFM to observe the growth morphology of calcites, which grew in silicon gels or agarose gels by altering reactants concentration. The images indicate that growth morphologies of calcites are dissimilar in different gels, although these crystals show similar growth mechanism. Analyzing the formation of growth morphology, the research proves that the crystal defects affect crystal growth. It can be concluded that the 2D nucleation and crystal defects control calcite growth.