Preparation Of Calcium Carbonate Biomimetic Materials

CaCO₃ was precipitated with NaCO₃/CaCl₂ and CO(NH₂)₂/Ca(CH₃COO)₂ reaction system. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The obtained results were as follow:1. The vaterite was synthesized by the templating method with anionic surfactants SDBS. The rhombohedral calcite crystal was obtained in the absence of SDBS. As the SDBS concentration was increased to 0.5mM, the sample consists of only vaterite stirred for 3 h, and the mixture of calcite and vaterite stirred for 10 h respectively . When the SDBS concentration was further increased to as high as1 mM, the pure vaerite was obtained. The increasing of stirred time enhances the excellent dispersant. And as the SDBS concentration was increased to 5.0 mM, the stirred time had no effect on the crystal polymorph of the sample. The possible formation mechanism of vaterite was proposed based on the experimental results.2. The fast mixing of aqueous solutions of calcium chloride and sodium carbonate resulted in crystalline forms of vaterite and calcite under vigorous stirring. Instable crystalline form vaterite and stable form calcite were found in the aqueous solution. Without modulating PH value, the crystalline forms all growth with experimental time increase. With PH value = 7, the crystalline forms all decrease with experimental time increase. The thermodynamic functions of the calcite were derived at different temperatures. When the SDBS concentration was increased to as high as 5 mM, the pure vatrite was obtained. Without modulating PH value, the stirred time had no effect on the crystal polymorph of the sample.the crystal morphologies were irregular.3. The calcite was synthesized by the templating method with Tween60. The rhombohedral calcite crystal was obtained in the present of Tween60. The stirred time and temperature had no effect on the crystal polymorph of the sample.4. The calcium carbonate was synthesized by the templating method with glass chip in the Teflon-lined autoclave. The aragonate was obtained in the absence of SDBS. In the presence of SDBS, the vaterite was obtained under conditions of constant temperature (90℃), the calcite was obtained under conditions of constant temperature (120℃). The possible formation mechanism of calcium carbonate was proposed based on the experimental results.5. The calcium carbonate was synthesized in presence of Polyacrylamide (PAM) and cetyltrimethylammonium bromide (CTAB) by a hydrothermal method at 90 and 120℃. Under the condition of the same concentration(PAM), the crystalline forms all grew with temperature increase. At the same temperature, and as the PAM concentration was increased to 0.1g.L^-1,the aragonite was obtained.The vaterite was obtained in the presence of PAM. The aragonite was obtained in the presence of PAM and CTAB. The possible formation mechanism of calcium carbonate was proposed based on the experimental results.