AFM IMAGING OF THE SURFACE OF NATURAL HEULANDITE

The factors that determine the resolution of the atomic force microsco pe (AFM) images of zeolite surfaces were determined by examining the s urface of natural heulandite crystals either in deionized water or in a 0.1 N NaOH aqueous solution. Wide-scan imaging of the (100) surface revealed for the first time a crystal growth-induced step structure th at corresponds to aluminosilicate layers. Also revealed was what is ca lled bunching (macro-steps composed of several aluminosilicate layers) . For the (100) surface, the atomic-scale image revealed the framework composed of TO4 polyhedrons (where T is either Si or Al), whereas for the (010) surface the image resolved the hydroxyl groups. This depend ence of the image on the surfaces implies that the magnitude of the pe riodic corrugation on the zeolite surface is a critical factor in the resolution of AFM imaging of zeolites. (C) 1998 Elsevier Science B.V. All rights reserved.