Epitaxial growth of calcite crystals on dolomite and kutnahorite (104) surfaces

摘要

Epitaxial growth of calcite on dolomite and kutnahorite (104) surfaces has been promoted at room temperature by immersing cleavage rhombohedra of these minerals in highly supersaturated solutions with respect to calcite (β_(calcite) = [a(Ca~(2+))·a(CO_3~ (2-))/K_(sp,calcite)] > 20). Scanning electron microscopy (SEM) images revealed an inhomogeneous coverage of dolomite and kutnahorite surfaces by large calcite crystals. In situ atomic force microscopy (AFM) observations showed that, while calcite islands rapidly grow perpendicularly to the substrates, their lateral spreading is slower. Furthermore, the accumulated strain associated with the relatively high calcite-substrate lattice misfits (δ > 2.2%) is accommodated by the generation of screw dislocations, which are evidenced by growth spirals on calcite three-dimensional islands. These observations are consistent with the Volmer-Weber epitaxial growth mode, characteristic of high overgrowth-substrate lattice misfits. Additional nanomanipulation experiments conducted with the AFM tip allowed us to remove calcite islands on both dolomite and kutnahorite (104) surfaces and to provide first estimates of shear strength.