Synthesis and Characterization of Ultra-fine Calcium Carbonate Whiskers in High-Gravity

Ultra-fine whiskers of calcium carbonate were successfully synthesized by reactive precipitation in highgravity field generated by the rotating packed bed（RPB）. In the experiment Ca（OH）2 and CO2 were as reactants and H3PO4 was used as the morphology-control additive. Synthesizing the same amount of CaCO3 whiskers，the needed carbonation time in the high-gravity field is 1/36-1/18 of that by the traditional technology reported in the literature. The ultra-fine CaCO3 whiskers can be synthesized and well-controlled under the following conditions：the volumetric flow rate of gas 100-300 L/h and that of liquid 600-1000 L/h，rotating speed of RPB 600-1200 r/min，reaction temperature between 40-80℃ and concentration of H3PO4 5.0%-30%. The calcium carbonate whiskers have the mean shaft diameter of 80-250 nm and the average aspect ratio of 10-25 with the narrow distribution of both the mean shaft diameter and the aspect ratio. The properties of the product are characterized by means of TEM，electron diffraction，XRD，TG-DTA and elementary analysis. Electron diffraction analysis shows that the synthesized calcium carbonate whiskers have crystalline structure，while XRD analysis indicates that aragonite structure accounts for 97.77% in content of the final CaCO3 whisker product. And TG-DTA analysis shows that the obtained product decomposes at 423℃，which is 402℃ lower than that of the CaCO3 obtained in the normal gravity.