Crystal growth of faujasite observed by atomic force microscopy

Atomic force microscopy (AFM) was employed to reveal the crystal growth mechanism of faujasite. The seeded growth of faujasite in dilute aluminosilicate solutions was observed. Two solutions were prepared: one was near equilibrium with the seed and the other was in growth mode for the seed. Morphological changes during the seeded growth were observed along with the growth period at the same position on the seed (ex situ observation). These observations showed the rough surface of the seed changing into a well-ordered (1 1 1) face in the solution that was near equilibrium with the seed. This surface ordering proceeded by thermodynamic stabilization of the top-surface structure via the mutual transfer of aluminosilicate species between the solution and solid phases, and/or by the dissolution of the amorphous matter on the seed. In growth mode, most of the top surfaces of the seeded crystals were terminated by double six-membered rings (D6Rs), while some were by complete or incomplete socialite cage. These results showed that aluminosilicate species equal to or smaller than 6R contributed to the crystal growth. (C) 2004 Elsevier Inc. All rights reserved.