Surface Microtopography of Lath-Shaped Hydrothermal Illite by Tapping-Mode™ and Contact-Mode AFM

Yoshihiro Kuwahara1, Seiichiro Uehara2 and Yoshikazu Aoki2
1 Department of Evolution of Earth Environments, Graduate School of Social and Cultural Studies, Kyushu University, Ropponmatsu, Fukuoka 810, Japan
2 Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, Hakozaki, Fukuoka 812, Japan

Abstract: Lath-shaped hydrothermal illite particles in Izumiyama pottery stone were examined by contact-mode atomic force microscopy (CMAFM) and tapping-mode AFM (TMAFM) in air. With CMAFM, the lath-shaped particles showed interlacing patterns on the (001) surface in deflection images, while in height images such patterns were unclear. Also, evidence of artifacts caused by frictional forces between the surface and tip and/or edge effects were found in the CMAFM height images of the particle and Si substrate surfaces. In contrast, TMAFM showed interlacing patterns clearly in both amplitude and height images, and artifacts were barely evident. The TMAFM height images permitted the accurate measurement of 1.0- or 2.0-nm height steps corresponding to single or double mica layers, as well.

Many lath-shaped particles in the Izumiyama hydrothermal illite exhibit interlacing patterns on their (001) surface, as shown by these AFM observations. The interlacing patterns are characterized by polygonal spirals with comparatively wide spacings and steps having a height of 1.0 or 2.0 nm. Generally a single lath-shaped particle has a single spiral center on the (001) surface, and 2 mica layers rotated 120° originate from the dislocation point. These support the view that lath-shaped illites belong to the 2M1 polytype. It is likely that these illite particles were formed by a uniform process of development that is characterized by very slow growth, spiral mechanisms in that growth and low supersaturation conditions.

Key Words: Contact-Mode AFM • Hydrothermal Illite • Interlacing Pattern • Microtopography • Polytype • Spiral Growth • Tapping-Mode AFM

Clays and Clay Minerals; October 1998 v. 46; no. 5; p. 574-582; DOI: 10.1346/CCMN.1998.0460511
© 1998, The Clay Minerals Society
Clay Minerals Society (www.clays.org)