Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO3 modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO3 modified in the presence of sodium stearate, ODP and OA. When modified CaCO3 was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO3 nanoparticles and the organic matrixes were greatly improved.
A new method for mimic biomineralization was used to synthesize CaCO 3 . The organized organic substrates, which could associate with Ca 2+ by means of molecular recognition and induce the nucleation and growth of CaCO 3, were synthesized fristly, and followed by the preparation of the CaCO 3 by carbonation of a solution of Ca(OH) 2 with CO 2. Well dispersed spindle-like nano-CaCO 3 particles with an average width of 50 nm and a ratio of diameter to length about 1∶5 were obtained under the given experimental conditions. The products were characterized by FTIR spectra, TGA analysis and transmission electron microscope(TEM).
Hollow spheres of Si/Al composite oxide with mesopores in the shell wall were prepared by combining O/W/O emulsion with sol-gel process. In this study, TEOS and aluminum isopropylate were used as silicon resource and aluminum resource, respectively. As an additive, PEG-20000 was added into the inorganic precursors. TEM and N2 adsorption-desorption isotherms indicate the presence of mesopores with uniform pore size in the shell wall. The diameter, shell thickness and hollow structure property of the spheres were characterized by transmission polarized light microscopy and SEM. （）27Al MAS NMR spectrum shows that the coordinated number of the aluminum species is four. The influences on special morphology under different oil phase and reaction temperature were also investigated. The hollow spheres exhibit high thermal stability and can remain their intact spherical structures even after calcination at 550 ℃ for 6 h. This strategy can be extended to synthesize hollow spheres of other binary composite oxide with mesopores.
