Preparation Of Calcium Carbonate Biomimetic Materials

CaCO3 crystals were fabricated in pyridine/water solution, collodion film and microemulsion reaction systems, respectively. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electronic microscopy (SEM), Transmission electronic microscopy (TEM), High-resolution transmission electronic microscopy (HRTEM) and Selected Area electronic diffraction (SAED). The obtained results were as follows:1. Polymorphs of calcium carbonate (CaCO₃) have been easily synthesized in a water/pyridine mixed solvent system under mild conditions without using other organic additives. The phase transition from pure aragonite to almost pure vaterite, and then to pure calcite, can be nicely captured by the choice of the suitable ratio of water to pyridine. The formation mechanisms of the obtained calcium carbonate crystals have been proposed. A novel morphology of calcite, wire-like shaped, was found in pure pyridine solvent. A process for the formation of wire-like calcite in pure pyridine solution has been proposed. The effect of experimental time on morphology of calcite was investigated in pure pyridine solvent. The results obtained proved that such reaction media could give an alternative and versatile tool for controlling both the structure and the polymorphism of inorganic materials.2. A novel and simple method for preparing tubular structure agglomerates of calcium carbonate (CC-tube) was described. Calcium chloride and sodium carbonate aqueous solutions were used as reactants separated by a collodion film (a nitrocellulose material). The effects of the concentrations of calcium chloride and sodium carbonate aqueous solutions on the morphology and phase structure of the as-obtained samples were investigated. The CC-tube growth was prevented with the increase of reactant concentration from 0.5 to 1.0 mol/L. Compared with Na₂CO₃ aqueous solution, it is favourable to grow calcite crystals in CaCl₂ aqueous solution.3. The soluble aspartic acid and insoluble collodion membrane were employed to direct the crystallization of calcium carbonate. The obtained results showed that the flower-shaped and self-assembled structure was fabricated. And it is favor to formating vaterite by increasing the reaction time. The formation mechanisms were proposed.4. The particle morphology and size of calcium carbonate were controlled simultaneously via reverse microemulsion (CTABⁿ-C4H9OH/c-C6H12/H2O reverse microemulsion system). The effects of the reaction time, the concentrations of CaCl₂ and Na2CO3 aqueous solutions, and the molar ratio of CaCl₂ to Na2CO3 on morphology and polymorph of CaCO3 crystals were studied. The micro-sized square, virgate and spherical particles of calcium carbonate were successfully synthesized in this study.