Early stage reversed crystal growth of zeolite A and its phase transformation to sodalite

Microstructural analysis of the early stage crystal growth of zeolite A in hydrothermal synthetic conditions revealed a revised crystal growth route from surface to core in the presence of the biopolymer chitosan. The mechanism of this extraordinary crystal growth route is discussed. In the first st...

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Bibliographic Details
Published in:Journal of the American Chemical Society Vol. 131; no. 49; p. 17986
Main Authors: Greer, Heather, Wheatley, Paul S, Ashbrook, Sharon E, Morris, Russell E, Zhou, Wuzong
Format: Journal Article
Language:English
Published: United States 16.12.2009
Subjects:
Crystallization
Nanoparticles - chemistry
Particle Size
Phase Transition
Surface Properties
Zeolites - chemistry
ISSN:1520-5126, 1520-5126
Online Access:Get more information
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Summary:Microstructural analysis of the early stage crystal growth of zeolite A in hydrothermal synthetic conditions revealed a revised crystal growth route from surface to core in the presence of the biopolymer chitosan. The mechanism of this extraordinary crystal growth route is discussed. In the first stage, the precursor and biopolymer aggregated into amorphous spherical particles. Crystallization occurred on the surface of these spheres, forming the typical cubic morphology associated with zeolite A with a very thin crystalline cubic shell and an amorphous core. With a surface-to-core extension of crystallization, sodalite nanoplates were crystallized within the amorphous cores of these zeolite A cubes, most likely due to an increase of pressure. These sodalite nanoplates increased in size, breaking the cubic shells of zeolite A in the process, leading to the phase transformation from zeolite A to sodalite via an Ostwald ripening process. Characterization of specimens was performed using scanning electron microscopy and transmission electron microscopy, supported by other techniques including X-ray diffraction, solid-state NMR, and N(2) adsorption/desorption.
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ISSN:1520-5126
1520-5126
DOI:10.1021/ja907475z