『Abstract
We investigated the dissolution behaviour of polished calcite
surfaces in situ using a fluid-cell atomic force microscope. Polished
calcite surfaces enabled us to study the effects of applied surface
stress and crystallographic orientation on calcite dissolution
pattern formation. Thin-sections of Iceland spar single-crystals
polished either parallel or with a 5゜ miscut angle to {1014}（後ろの1の頭に-） cleavage planes were studied. Compressive
surface stresses of up to 50 MPa were applied to some of the thin-section
samples by means of elastic concave bending. Experiments were
carried out in semi-stagnant deionized water under mainly transport
limited dissolution conditions. Samples polished parallel to {1014}（後ろの1の頭に-） cleavage planes dissolved by the formation
of etch-pits originating from polishing defects. The dissolution
behaviour of 5゜ miscut surfaces was relatively unaffected by polishing
defects, since no etch-pits developed in these samples. Dissolution
of the miscut samples led to stepped or rippled surface patterns
on the nanometer scale that coarsened during the first 30-40 min
of the experiments. Possible reasons for the pattern-coarsening
were: (i) progressive bunching of retreating dissolution steps
and (ii) surface energy driven recrystallization (Ostwald ripening)
under transport limited dissolution conditions. A flat polished
miscut surface in calcite may recrystallize into a hill-and-valley
structure in a (near-)saturated solution so as to lower its total
surface free energy in spite of a larger surface area. No clear
effect of applied stress on dissolution pattern formation has
been observed.』
1. Introduction
2. Method
2.1. Material and sample preparation
2.2. AFM experiments
2.3. AFM image acquisition and analysis
3. Observations
3.1. Surfaces (sub)parallel to cleavage planes
3.2. Surfaces at 5゜ to cleavage planes
4. Discussion
4.1. Dissolution rate in semi-stagnant water
4.2. Pattern coarsening in miscut samples
5. Conclusions
Acknowledgments
Appendix A
A.1. Grinfeld instability
References