On the kinetics of ion exchange in phlogopite - An in situ afm study

Aldushin, Kirill; Jordan, Guntram; Aldushina, Elena und Schmahl, Wolfgang W. (2007): On the kinetics of ion exchange in phlogopite - An in situ afm study. In: Clays and Clay Minerals, Bd. 55, Nr. 4: S. 339-347

Abstract

The kinetics of cation exchange in phlogopite have been studied in situby hydrothermal atomic force microscopy (HAFM). The exchange ofinterlayer K by octylammonium ions caused an increase in the interlayerdistance and the formation of reaction fronts which can be locallyresolved by AFM. The observed reaction fronts revealed Substantialvariations in their propagation rates - even within single interlayers.This observed variability in interlayer reactivity could mainly beattributed to chemical and structural inhomogeneities of the samples. Aquantitative evaluation of the front propagation at representative sitesyielded a diffusion coefficient of the K+ exchange by octylammonium of1.2 +/- 0.6 x 10(-11) cm(2)/s A assuming negligible transport normal tothe layers. The reverse reaction, i.e. the exchange of organic ions byK+, resulted in a retreat of the reaction fronts and a generalrestoration of the original morphological state. However, indications ofstructural alterations and areas with trapped oetylammonium ions werefound.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften > Kristallographie und Materialwissenschaft
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• Sprache: Englisch