Fabrication of Single-Crystalline Calcite Needle-Like Particles Using the Aragonite–Calcite Phase Transition

Calcium carbonate (CaCO3) occurs in two major polymorphs: rhombohedral calcite and orthorhombic aragonite, the latter is thermodynamically metastable. In this study, we first prepared aragonite needle-like particles by introducing CO2-containing gas into Ca(OH)2 aqueous slurry. Then, the resulted aragonite particles were heat treated at 500 ◦C for 1 h, in order to induce the aragonite–calcite phase transition. Particle structures before and after the heat treatment were characterized mainly by powder X-ray diffractometry (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). We found that single-crystalline calcite needle-like particles with zigzag surface structures can be fabricated using the phase transition.