Effect of ball milling on chemically synthesized nanoparticles of CaCO3

Nanoparticles of CaCO3 with an average size of ∼28 nm was synthesized by chemical precipitation method. The as prepared sample was of vaterite phase, possibly due to the high value of surface energy associated with the smaller size. The as prepared sample was subjected to ball milling for different milling times and the milled samples were characterized using XRD analysis, and FTIR and FT Raman spectroscopy. Ball milling induced vaterite to calcite phase transformation along with the formation of a small percentage of aragonite phase. The grain size of the vaterite phase was not much affected by milling, while that of calcite phase was found to be reduced from ∼50 to ∼32 nm. The results were explained in terms of the enhanced diffusion due to ballistic displacement of atoms during ball milling.