| CaCO3 is one of the important fillers used in the industries of plastics, rubber, paint, and so on. Nanoparticles as an important harvest of nanotechnology have attached many attentions in the field of materials science. However, the nano-CaCO3 are easily aggregate because of the very small particle size, high surface activity and high surface energy. Therefore, controlling the particle size during the preparation process, avoiding the aggregation of particles and inducing the powders to redisperse in the medium are current'hot topics'in the field of nanomaterials. Surface modification of CaCO3 would lead to a great expansion in its applications; since mineral particles are hardly dispersed in a polymer matrix. Biomineralization is mother natures approach to advanced materials synthesis, and it attempts to chemically control the growth of inorganic crystals in the organic substrate by adapting or imitating biological mineralization strategies. The key to the successful synthesis of an inorganic-organic composite is an understanding of the parameters that control the nucleation and growth of inorganic crystals under the organic substrate in aqueous solution. In this thesis, a research on combine the techniques of chemical synthesis and surface modification are performed. In-situ surface modification technique is took place during the preparation via mimicking the essential functions of biomineralization. As a result, a series of functional nano-CaCO3 are prepared under kinds of effective controls. The results indicate it is an available and ideal strategy.We synthesize octadecyl dihydrogen phosphate (C18H37OPO3H2) as organic substrate which can make interfacial recognition of molecules with mineral. The organic substrate shields the solid surface through C18H37OPO3Ca, which decreasing dramatically its surface energy and hence facilitate the dispersion of the filler in a polyolefinic matrix, on the other hand, enhance the compatibity between filler and matrix leading possibly to better mechanical performance of the composite. The spindle-like hydrophobic CaCO3 nanoparticles with a mean diameter less than 0.1μm and the radio of diameter to length about 1:3.5 can be synthesized in situ by a carbonation process in the presence of organic substrate. The active ratio of the product reaches 99 %. As the concentration of organic substrate increased, the active ratio of the hydrophobic CaCO3 increased and the mean particle length increased at the same time. Hydrophobic calcium carbonate nanoparticles were prepared via crystallization of calcium carbonate whereby aqueous solutions CaCl2 and Na2CO3 are combined with C18H37OPO3H2 in methanol. In the experiments, the surfactant could not only control the crystal shape but also modify the surface of calcium carbonate. The ellipse-like nano-CaCO3 particles with an average diameter of 40 nm have been obtained under given experimental conditions. The crystal polymorph of the final particles was aragonite and calcite. The contact angle analysis indicated that the final calcium carbonate was hydrophobic. We have succeeded in surface modification of calcium carbonate in situ.Hydrophobic CaCO3 particles were prepared in situ by carbonation of Ca(OH)2 slurry in the presence of the ethanol solution of oleic acid by mimicking the process of biomineralization. The oleic acid solution was used in precipitation process to control the particle size and to modify the surface of CaCO3 particles simultaneously. In this study the ellipse-like CaCO3 particles in the average diameter of about 50 nm can be synthesized. By changing the weight ratio of oleic acid to CaCO3, the surface property of CaCO3 particles was changed from hydrophilic to hydrophobic. The active ratio of the modified CaCO3 might reach 100 %. The contact angle of the modified CaCO3 was 108.77 o. IR spectrums of the CaCO3 particles showed the appearance of the alkyl groups from the oleic acid. Hydrophobic vaterite nanoparticles were prepared via crystallization of CaCO3 by mimicking the process of biomineralization, whereby aqueous solutions CaCl2 and Na2CO3 are combined with oleic acid in methanol. The organic moieties shield the solid surface through the reaction of–COO- groups of oleic acid with Ca2+, which decreasing dramatically its surface energy and hence facilitate the dispersion of the filler in a polyolefinic matrix. High concentration of oleic acid gave stable vaterite crystals covered with the hydrophobic species. The present stable monodispersed spherical vaterite particles would be expected to be excellent as stable pillaring precursors in several polymer matrixes. The C=C bonds of oleic acid can be copolymerization with organic monomer, and this is potentially important for industrial process of biomineralization. Two metastable calcium carbonate polymorphs, rod-like aragonite and spherical vaterite are selectively formed using hydrolyzation of urea. Aragonite rods were synthesized from a calcium acetate (Ca(AC)2) and urea (CO(NH2)2) solution under given condition. In contrast, the addition of oleic acid results in the formation of spherical vaterite. The results show that oleic acid can be used as additive to select the polymorph from aragonite and vaterite.Hydrophobic CaCO3 nanoparticles were prepared in aqueous solution via carbonation method by mimicking biomineralization. In this paper, C17H35COONa solution synthesized by C17H35COOH and NaOH was used as organic substrate and growth medium for CaCO3. This organic substrate could not only induce the nucleation and growth of CaCO3 but also make the surface of CaCO3 hydrophobic. The spindle-like CaCO3 with a diameter about 10 nm and the ratio of diameter to length about 1:4 was prepared. According to the floating ratio test, the active ratio of the products exceeded 99 % at an appropriate condition. A simple synthetic method for the preparation of hydrophobic lamellar aragonite has been developed, whereby aqueous solutions CaCl2 and Na2CO3 are combined with sodium stearic in methanol at 60 oC. The results reveal that the surfactant plays important roles in determining the structure and morphology of the sample. The contact angle of the modified aragonite reached 108.59 o. We have succeeded in surface modification of particles in situ.CaCO3 nanoparticles with about 50 nm in size could be prepared by carbonation reaction of a mixture of Ca(OH)2 and dodecyl dimethyl betaine (BS-12) via bubbling CO2 gas. The results indicate that the CaCO3 powder samples can self-diffuse in water, thus forming a suspension with enhanced stability and longevity. The bubbling effect of BS-12 increased the retention time and contact area of CO2 in the solution thus the higher carbonation efficiency was observed. The presence of BS-12 accelerates the period of absorption and shortens the time of carbonation. We have succeeded in surface modification of CaCO3 with BS-12.A carbonation route for the synthesis of nano-sized calcium carbonate (aragonite) was studied. In the process, poly-acrylamide (PAM) was used as an organic substrate to induce the nucleation and growth of calcium carbonate. The calcium carbonate particles were produced by means of carbonation of the mixture of calcium hydroxide and poly-acrylamide by bubbling CO2/N2 gas mixture. The synthesized calcium carbonate particles in the presence of organic substrate are the mixture of aragonite with needle shape and calcite with cubic shape. The–NH2 groups of poly-acrylamide could adsorb onto the growing crystal face and suppress the transformed of aragonite into calcite.In this thesis, we attempted a biomimetic method to obtained nano-CaCO3 with special properties, introduced a novel ideal to synthesis nano-CaCO3. In-situ surface modification technique employed during preparation process, which introduced functional groups upon the surface of nano-CaCO3 overcoming the agglomeration of nanoparticles. For the benefits of simple,uninterrupted and inexpensive, this innovatory technique has potential use in application and guide meaning in large-scale industrialization manufacture of nano-CaCO3.
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