Synthesis of CaCO3 nanoparticles by mechanochemical processing

The synthesis of calcite (CaCO3) nanoparticles by mechanochemical reaction and subsequent heat treatment was investigated. A solid-state displacement reaction CaCl2+Na2CO3 -> CaCO3+2NaCl was induced during mechanical milling of a CaCl2+ Na2CO3 powder mixture. Heat treatment of the as-milled powder at 350 degrees C completed the reaction, forming crystalline CaCO3 nanoparticles separated from each other in a dry-salt matrix. A simple washing process to remove the matrix yielded calcite single phase ultrafine powder. The mean particle size was controlled by changing the volume fraction of CaCO3 in the matrix. 20% volume fraction yielded nanoparticles of similar to 140 nm in size, whereas 10% volume fraction led to similar to 80 nm size nanoparticles.