Calcite microrod arrays fabricated via anisotropic dissolution of calcite in the presence of NH₄I and (NH₄)₂SO ₄

In this work, we studied the anisotropic dissolution process of geogenic calcite substrates in aqueous solution in the presence of ammonium iodide and ammonium sulfate. Arrays of calcite micropyramids elongated along the c axis of calcite and quadrangular and hexagonal transverse cross sections were obtained for the first time via anisotropic dissolution in undersaturated aqueous solutions in the presence of ammonium iodide and ammonium sulfate, respectively. The anisotropic dissolution and the formation process of the micropyramids were tracked with SEM after different dissolution times. It is found that the heights of the micropyramids increase with the increase of the dissolution time and the concentration of the ammonium salts.