Study of controlled crystallization of calcite by electrochemical method. Effect of ions on nucleationgrowth of calcite
The study of crystallization of calcium carbonate on gold single-crystal (111) presents a big interest for the research of new materials finely accorded. The aim of the present work is to form by electrochemical way an epitaxial calcite without use any templates. The deposits formed on the massive copper and oriented copper, silver and gold substrates are analyzed by scanning electronic microscopy (SEM) coupled with the elementary analysis EDS, electron backscattered diffraction (EBSD), X-rays diffraction (XRD), spectroscopy Raman and by electrochemical impedance spectroscopy (EIS). The precipitation of calcium carbonate is induced by electrochemical way by imposing the dissolved oxygen reduction potential which allows an increase of the local pH at the metal/solution interface. A successful crystallization of epitaxial calcite is observed on gold and silver supports with an orientation (001) parallel to the surface of substrates whereas two crystallographic varieties are observed on the polycrystalline substrate (calcite and vatérite) and only the calcite is precipitated on the single-crystal copper under various rhombohedra forms. In the light of these results an epitaxial relation is established. The effect of sulphate, magnesium and phosphate is studied towards the nucleation-growth and the orientation of the calcite. Finally, two molecules (MEDPHOS and the isonicotinic acid) are tested for their inhibiting power of the crystallization of calcite.