Preparation and characteristics of calcium carbonate/silica nanoparticles with core-shell structure

In this paper, a step-by-step (SBS) method was used to prepare calcium carbonate/silica nanoparticles with core-shell structure. The core of calcium carbonate nanoparticles were cubic shaped with an average size of 48 nm obtained in the first step of carbonation method and the shell of SiO2 with thickness about 5 nm were coated on the core in the second step of sol-precipitation method from precursor of Na2SiO3·9H2O. The products were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscope. The results indicate that the products have a core-shell structure, which are combined through the chemical bonds of Ca–O–Si. In addition, it is also shown that the reaction parameters, including the pH value of the solution, the concentration of the Na2SiO3 solution and the reaction time, play important roles in the formation of SiO2 thin layers coated on the surface of CaCO3 particles. Analyses of acid resistance property (ARP) indicate that the products have relatively high ARP and fine stability in acid solutions.